China Construction Office China Quality Surveillance Inspection Quarantine Headquarters

GB 50251---2003 Code for design of gas transmission pipeline engineering

Table of Contents

1. General Principles……………………………………………………………………. (1)

2. Terms………………………………………………………………………………….. (2)

3. Trunkline Process…………………………………………………………………….. (3)

3.1 General Regulations……………………………………………………………... (3)

3.2 Process Design…………………………………………………………………… (3)

3.3 Process Calculation……………………………………………………………… (4)

4. Routing………………………………………………………………………………… (6)

4.1 Route Selection…………………………………………………………………... (6)

4.2 Area Grade Classification……………………………………………………….. (7)

4.3 Pipeline Laying…………………………………………………………………... (8)

4.4 The Setting of Block Wave……………………………………………………… (12)

4.5 Pipeline Constructs………………………………………………………………. (12)

4.6 Warning Signs……………………………………………………………………. (13)

5. The structure design of pipelines and pipeline auxiliaries………………………… (13)

5.1 Calculation of pipeline intensity and stability………………………………… (13)

5.2 Materials…………………………………………………………………………. (14)

5.3 Pipeline auxiliaries……………………………………………………………… (15)

6. Trunkline station……………………………………………………………………… (16)

6.1 Setting principle of trunkline station…………………………………………… (16)

6.2 Pressure Adjustment and measuring design……………………………………. (16)

6.3 Pigging Design…………………………………………………………………… (17)

6.4 Disposal of compressor set and design principle of workshop……………….. (17)

6.5 Compressor station process and the assisted system………………………….. (18)

6.6 Compressor set model…………………………………………………………… (19)

6.7 Compressor set safety protection……………………………………………….. (19)

6.8 Pipeline inside stations………………………………………………………….. (20)

7. Ground equipment for underground gas storage……………………………………. (21)

7.1 General……………………………………………………………………………. (21)

7.2 Ground process…………………………………………………………………... (21)

7.3 Selection equipment……………………………………………………………... (21)

7.4 Auxiliary system…………………………………………………………………. (22)

8. Monitor and system control…………………………………………………………. (22)

8.1 General regulations……………………………………………………………… (22)

8.2 System control management……………………………………………………. (23)

8.3 Controlled station……………………………………………………………………… (24)

8.4 Monitoring……………………………………………………………………………... (25)

8.5 Communication………………………………………………………………………… (26)

9. Auxiliary production facilities………………………………………………………………. (27)

9.1 Power supply…………………………………………………………………………… (28)

9.2 Water supply and drainage…………………………………………………………….. (29)

9.3 Heating, ventilation and air conditioning……………………………………………… (30)

10. Welding, inspection, pipeline pigging and pressure test………………………….. (32)

10.1 Welding and Inspection………………………………………………………… (32)

10.2 Pipeline pigging and pressure test……………………………………………. (35)

10.3 Dryness…………………………………………………………………………. (36)

11 Energy Saving, Health Protection and Labour Safety Health……………………… (37)

11.1 Energy saving…………………………………………………………………… (37)

11.2 Environmental protection……………………………………………………… (37)

11.3 Labor safety/hygiene…………………………………………………………… (38)

Appendix A Process Calculation of Gas Transmission Pipeline

Appendix B Stress Calculation and Equivalent Weight Stress of Axis Direction of Restricted Underground Straight Pipeline Subsection

Appendix C Calculation of Elbow Build-up Stress under the Combine Effect of Internal Pressure and Temperature Different

Appendix D Design Parameter for Laying Pipeline Conditions

Appendix E Pipeline accessories buildup stress calculation caused by expansion

Appendix F Structure and calculation for tee and strength compensation for drilling hole

Appendix G The calculation of compressor axis power

Appendix H Types of Pipe-End welding tie-in

Additional notes

Appendix: Explanations for the wording of the criterion

1.0 GENERAL PRINCIPLES

1.0.1 This code is designed in order to carry out China’s concerned policies and guidelines in the design for trunkline engineering and unify the technical requirements for advanced technique, reasonable economy, applied safety and guaranteed quality.

1.0.2 This code applies to the design for onshore trunkline engineering. The design for trunkline engineering shall conform to the following principles:

1.0.2.1 Protect the environment, economize the energy resources, economize the land, and handle the relationship with railroads and roads, river well;

1.0.2.2 Adopt advanced techniques and assimilate new abroad and domestic science and technology achievements;

1.0.2.3 Optimize design blueprints and ensure the economical and reasonable trunkline process and the best process parameter;

1.0.3 Besides according with this code, trunkline engineering design shall accord with the regulations of China’s compulsive concerned standard.

2.0 TERMS

2.0.1 Pipeline gas Natural gas and artificial coal gas which are transmitted to users through pipelines. 2.0.2 Gas transmission pipeline project The project of transmitting natural gas and artificial coal gas through pipelines, which generally includes: project of trunkline, trunkline station, trunkline crossing and auxiliary producing facilities etc. 2.0.3 Gas transmission station The general term of various process stations of trunkline engineering, which includes gas transmission first station, gas transmission last station, compressor station, gas receiving station and gas off-take station, etc. 2.0.4 Gas transmission initial station The start station of the trunkline which generally has the function of separation, pressure adjustment, measuring and pigging, etc. 2.0.5 Gas transmission terminal station The terminal station of the trunkline which generally has the function of separation, pressure adjustment, measuring, pigging and gas supply, etc. 2.0.6 Gas receiving station The station set along the routes of trunkline in order to receive the gas from the branch lines, which generally has the function of separation, pressure adjustment, measuring and pigging, etc. 2.0.7 Gas distributing stationThe station set along the routes of trunkline in order to distribute gas to users, which generally has the function of separation, pressure adjustment, measuring and pigging, etc. 2.0.8 Compressor station The station set along the routes of trunkline in order to supercharge pipeling gas through compressors.

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2.0.9 Underground gas storage It refers to the geological formation that uses certain confined space to store natural gas, this kind of geological formation including salt cave, depleted oil and gas reservoir, water bearing formation and so on. 2.0.10 Gas injection station It refers to the station that is used to inject natural gas into underground gas storage. 2.0.11 Gas withdraw station It refers to the station that is used to withdraw natural gas from underground gas storage layer. 2.0.12 Pipe auxiliaries It refers to pipe fitting, flange, valve and its assembled fitting, insulated flange or insulated tie-in and other pressure-bear fittings specially used for pipelines. 2.0.13 Pipe fitting It refers to elbow, siphon, three-way pipe, different-diameter tie-in and sealing head of pipe. 2.0.14 Gas transmission trunkline The main operational pipeline from the gas transmission initial station to gas transmission terminal station. 2.0.15 Gas transmission branch line The pipelines used for transmitting pipeling gas to trunkline and transmitting pipeling gas out of trunkline. 2.0.16 Pipe laying with elastic bending Pipelines produce elastic bending by outside force or deadweight effect. Pipe laying with elastic bending is the laying way of making use of this bending to change the pipeline direction or adapt to altitude change. 2.0.17 Pigging system The whole set of facilities to eliminate agglomerates and aggradations in pipelines, separate, replace and on-line detecting for the pipeline, which includes pigging devices, pigging device receiving and dispatching canister, pigging device indicator and pigging device track-indicator etc. 2.0.18 Design pressure In corresponding design temperature, design pressure refers to the pressure value used for confirming container or pipeline’s calculation of the wall thickness and other components’ sizes. The pressure is named as design internal pressure where the pressure is the internal pressure of containers or pipelines. The pressure is named as design external pressure where the pressure is the external pressure of containers or pipelines. 2.0.19 Design temperature The possible maximum and minimum temperature of pipeline walls or metal component during the normal working process of containers and pipelines at the corresponding design pressure. 2.0.20 Pipeline gas temperature The flowing temperature when gas transmitting in pipelines. 2.0.21 Operating pressure The pressure inside the medium of a system under stable operating condition. 2.0.22 Maximum allowable operating pressure (MOP) Under normal working condition, the actual maximum operating pressure in the pipeline. 2.0.23 Maximum allowable operating pressure (MAOP)

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When the pipeline system is working according to this specification, its maximum continuously operating pressure should be equal or less than design pressure. 2.0.23 Relief and blow-down system 2.0.24 Relief and blow-down system The facilities used for collecting and handling the ejected flammable gas in condition of exceeding pressure relief, emergent blow-down, start working, shutdown and maintenance. The relief and blow-down system is composed of relief facilities (relief valve, decompressing valve, safety valve), collecting pipelines and handling facilities (such as separation container, torch) or one of the parts. 2.0.25 Water dew point The temperature at which the first drop of water seperated out of gas under certain pressure. 2.0.21 26 Hydrocarbon dew point The temperature at which the first drop of liquid hydrocarbon separated out of gas under certain pressure.

3.0 TRUNKLINE PROCESS

3.1 General Regulations

3.1.1 The design transmission capability of the trunkline shall be calculated in accordance with the annual or daily maximum transmission volume, which is regulated in the design task or the contract. The manday per year of designing shall be calculated by 350d.

3.1.2 The mechanical impurity shall be cleaned up from the gas into the trunkline; the water dew point shall be 5 degrees lower than the minimum environmental temperature of transmission condition; the hydrocarbon dew point shall be lower than the minimum environmental temperature; the content of sulfureted hydrogen in the gas shall be not more than 20mg/m3.

3.1.3 The design pressure of trunkline shall be confirmed after technical and economical comparison of gas source condition, clients’ requirements, pipeline material quality, construction level, region safety and other relative elements.

3.1.4 Where trunkline and its auxiliaries have adopted erosion proofing measures according to China’s active 《Design code for steel pipeline and tank erosion proofing engineering 》 SY 0007 and 《Design code for buried steel pipeline strong electric current cathode protection》 SY/T 0036, the erosion abundance volume on the pipeline wall shall not be added.

3.1.5 Trunkline shall set pigging facilities. Pipeline internal-smear technique shall be adopted if conditions allow.

3.2 Process Design

3.2.1 Process design shall be confirmed after comprehensive optimized analysis and technical and economical comparison in accordance with gas source condition, transmission distance, transmission volume and clients’ characteristics and requirements.

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3.2.2 Process design shall include the following contents: 3.2.2.1 confirm gas transmission process flow. 3.2.2.2 confirm process parameter and flow of trunkline station. 3.2.2.3 confirm the number and interval between stations of trunkline stations. 3.2.2.4 confirm diameter, design pressure and station pressure rate of compressor station. 3.2.3 Gas source pressure shall be used reasonably for gas transmission by pipeline. Where gas is transmitted by supercharging, reasonable rate of station pressure of compressor station and interval between stations shall be selected. Where gas is transmitted by radial compressor and supercharging, the rate of station pressure might be 1.2:1.5, and the interval between stations shall be not shorter than 100km. 3.2.4 Compressor station specialty and pipeline specialty shall be coordinated. In condition of normal gas transmission, compressor set shall work in high efficiency area. The number, model, and connection mode of the compressor set shall be within the economic operation and satisfy the requirements of the process design parameter and working situation changes. 3.2.5 Gas quantity limit and pressure limit facility might be set on the gas distributing pipelines of the gas off-take stations with gas distributing function. 3.2.6 Gas quality monitoring facility shall be set on gas admission pipelines of trunkline initial station and gas receiving station. 3.2.7 Intensity design of trunklines shall satisfy the requirements of working situation changes. 3.2.8 Gas transmission station shall all set station-skipping side way. Block valve shall be set on the gas admission and gas-out pipelines. Block valve should be an interval from the process facility, assure easy to approach and operate under the emergency condition. Block valve should have the function to be manual operated.

3.3 Process calculation

3.3.1 Trunkline process design shall include the following materials: 3.3.1.1 The composition of the pipeling gas. 3.3.1.2 Quantity, position, gas supply volume and its adjustable range of gas sources. 3.3.1.3 Pressure of gas source and its adjustable range, pressure descending speed and continuing period under upper limit pressure. 3.3.1.4 The requirements of gas supply pressure, gas supply volume and its changes from the number of the users along the route of pipelines. When require for peak molulation with the storage of trunkline gas, it should be provided with user’s gas usage characteristic curve and data. 3.3.1.5 The natural environment and the temperature where the pipe buried. 3.3.2 Trunkline process shall be calculated according to the following formula: 3.3.2.1 Where the relative height difference along the route of pipelines △h<=200m, and omit the affection of the height difference, calculate according to: (formula and explanations omitted here on page 6 & 7). 3.3.2.2 Where the relative height difference along the route of pipelines should be considered, calculate according to: (formula and explanations omitted here on page7). 3.3.2.3 Water power friction resistance quotiety shall be calculated according to the following formula:

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(formula and explanations omitted here on page 7 & 8). 3.3.3 The temperature at any point along the routes of trunkline shall be calculated according to the following formula: 3.3.3.1 In condition of no throttle effect, calculated in the following formula: (formula and explanations omitted here on page 8). 3.3.3.2 In condition of throttle effect, calculated in the following formula: (formula and explanations omitted here on page 8). 3.3.4 according to actual requirements of the project, it is necessary to conduct stable and

dynamic analogue computation and determine the important figures such as the quantity of compressed air station for different working conditions, pressurization ratio, compressor calculation power and power consumption, flow rate/pressure/temperature at each throttle point and gas storage amount of pipeline and so on. Based on the analysis of the system, the time section can be calculated by hour or by day.

3.3.5 The software for stable and dynamic analogue computation shall be industry proven. 3.4 Safe relief of trunkline 3.4.1 Trunkline station shall set relief and blow-down facilities before the gas admission block valve and after the gas-out block valve. 3.4.2 Blow-down pipelines shall be set on upper and lower reaches of the trunkline block valve. The blow-down pipeline shall discharge the gas between the two block valves promptly. The diameter of the blow-down valve shall be equal to the diameter of the blow-down pipeline. 3.4.3 Safety valve shall be set on the pressured facilities and containers of trunkline station. The relieved gas by safety valve can be introduced into the blow-down pipeline of the same grade of pressure. 3.4.4 The fixed pressure of the safety valve shall be less than or equal to the designed pressure of the pressured facilities and containers. The fixed pressure of the safety valve (Po) shall be confirmed according to the maximum operating pressure ( P) and shall accord with the following requirements: 3.4.4.1 In condition of P<=1.8MPa, Po=P+0.18MPa; 3.4.4.2 In condition of 1.8MPa<P<=7.5MPa, P0=1.1P; 3.4.4.3 In condition of P>7.5MPa, P0=1.05P. 3.4.5The relief pipeline of safety valve shall be calculated in accordance with the following requirements: 3.4.5.1 The relief pipeline of the single safety valve shall be confirmed according to the fact that the back pressure is not more than 10% of this valve’s relief pressure and not less than the pipeline exit outlet diameter of the safety valve; 3.4.5.2 The relief pipeline connecting multi-safety valves shall be confirmed according to the fact that the back pressure produced when all safety valves work at the same time is not more than 10% of any of the safety valve’s relief pressure and the section area of the relief pipeline shall be not less than the sum of each branch pipeline’s section area. 3.4.6 The blow-down gas shall be discharged into atmosphere through blow-down vertical pipeline and shall accord with environment protection and fireproofing requirements. 3.4.7 Trunkline blow-down erect pipeline shall not be set at any place causing fire and affecting residents’ health. Its height shall be higher than 2m above the nearby constructions and its overall height shall be not lower than 10m.

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3.4.8 Trunkline station blow-down vertical pipeline shall be set outside of bounding walls and the interval between stations and other constructions should according to national criterion 《Code for fire protection design of petroleum and natural gas engineering》. Its height shall be 2m higher than 2m above the nearby constructions and its overall height shall be not lower than 10m. 3.4.9 The setting of the blow-down vertical pipeline shall be in accordance with the following stipulations: 3.4.9.1The diameter of the blow-down vertical pipeline shall satisfy the requirement of the biggest blow-down volume. 3.4.9.2 Siphon is not allowed to be set on the top of the blow-down vertical pipeline. 3.4.9.3 The bottom siphon of blow-down vertical pipeline and the connected level blow-down eduction pipeline must be buried in land; the level-buried straight pipeline before the siphon must be anchored. 3.4.9.4 Blow-down vertical pipeline shall have steady pipelines to reinforce.

4.0 ROUTING

4.1 Rroute Selection

4.1.1 The selection of the routes shall accord with the following requirements: 4.1.1.1 The best route shall be confirmed after comparison of different projects, and in accordance with the landform, the engineering geology, the geographical position of the main gas admission and gas supply point along the route and the conditions of transportation and power. 4.1.1.2 The routes shall keep away from areas of perennial economic crops and important cropland infrastructure facilities. 4.1.1.3 The position selection of big and medium river crossing engineering and compressor station shall accord with the main direction of routes. The partial direction shall be adjusted according to the position of big and medium crossing engineering and compressor stations. 4.1.1.4The routes shall keep away from important military facilities, flammable and explosive storages and safety protection district of state key Cultural Relics Preservation Monuments. 4.1.1.5 The routes shall keep away from designated urban planning area, airport, railway station, sea (river) wharf and national conservancy district, etc. When subjected to the constraints, it is necessary to pass through above areas, we should apply for the supervisor’s agreement and take the safety protection measures. 4.1.1.6 The routes shall not go through the tunnels and bridges of railways and roads, marshalling yard, large passenger station and power substation, except the roads’ tunnels and bridges specialized for pipelines. 4.1.2 Trunkline shall keep away from poor engineering geological sector. In condition of difficulties of avoiding, appropriate position and method shall be selected to go through the following sectors: 4.1.2.1 In condition of coast of small dimension, after manipulated, in the sector of coast which is ensured stable, appropriate part might be selected to go through in the way of spanning or shallow burying. Where trunkline goes through rock pile, judgment shall be concluded about its stability and corresponding measures shall be adopted. 4.1.2.2 At swamp or soft soil sector, the passable sector shall be confirmed according to its scope,

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soil thickness, landform, underground water level, soil-fetching and some other conditions. 4.1.2.3 At debris flow sector, if it cannot be bypassed reasonable method should be adopted according to the actual landform and geologic condition in order to go through. 4.1.2.4 At deep and narrow gully, spanning should be adopted in order to go through. At shallow and wide gully, where aggradations are relatively stable, buried laying should be adopted. 4.1.2.5 Where pipelines go through foreshore or desert sector, the stability shall be concluded and the corresponding pipeline-stabling protection measures shall be adopted. 4.1.2.6 At the sector where the earthquake intensity is higher than or equal to 0.1g, pipelines should go through by the smaller faultage displacement and narrower areas and essential engineering measures shall be adopted. Pipelines shall not be laid at any sector where coast, landslide, earth falling, earth cracking, debris flow and fluidified sand might be caused by earthquake.

4.2 Area grade classification

4.2.1 Four area grades are classified in accordance with the number of families and (or) the denseness of constructions along the routes of trunkline, according to which corresponding pipeline design shall be conducted. 4.2.2 Area grade classification shall accord with the following stipulations: 4.2.2.1 Within the range of 200m of both sides along the central line of pipeline, some sectors which is 2km long and can include the maximum inhabitants are classified randomly. The four grades are classified according to the number of families in the classified sectors. In the villages, compounds, uptown buildings where countryside people assemble, each independent family shall be calculated as one building for people inhabiting. (1) Area grade one: the sector where there are 15 families or less; (2) Area grade two: the sector where there are more than 15 families and less than 100 families; (3) Area grade three: the sector where there are 100 families or above, including suburb uptown,

commercial district, industrial district, developing district and the dense uptown which is not qualified for the condition of area grade four.

(4) Area grade four: it refers to the sector where there are generally centralized buildings of four floors and above (exclude the floor of basement), frequent transportation, and plenty of underground facilities.

4.2.2.2 Where area grade boundaries are classified, the distance between the boundary and external border of the nearest building shall be longer than or equal to 200m. 4.2.2.3 The schools, hospitals and other public locations where people assemble within area grade one and grade two, the design quotiety shall be selected according to area grade three. 4.2.2.4 Where one area’s developing programming will sufficiently change the current grade, the area grade shall be classified according to the developing programming. 4.2.3 The intensity design quotiety of trunkline shall accord with the stipulation of table 4.2.3. Intensity design quotiety Table 4.2.3

Area grade Intensity design quotiety (F) Grade one 0.72 Grade two 0.6

Grade three 0.5

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Grade four 0.4 4.2.4 The intensity design quotiety of trunklines which go through railways, roads and locations where people assemble and the trunklines in the trunkline station shall accord with the stipulation of table 4.2.4.

Intensity design quotiety of pipelines going through Table 4.2.4 railways, roads and in trunkline stations

Area grade One Two Three Four

Trunkline and trunkline segment

Intensity design quotiety (F) The trunklines with cover going through Road III, IV

0.72 0.6 0.5 0.4

The trunklines without cover going through Road III,IV

0.6 0.5 0.5 0.4

The trunklines with cover going through Road I, II, speedway and railway

0.6 0.6 0.5 0.4

The trunklines in trunkline station and their 200m trunklines of upper and lower reaches each. The trunklines in block valve station and their 50m trunklines of upper and lower reaches each. (the distance shall be calculated from the border of trunkline station and block valve station)

0.5 0.5 0.5 0.4

The trunklines at the locations where people assemble.

0.5 0.5 0.5 0.4

4.3 Pipeline Laying

4.3.1 Trunkline shall be laid by being buried in land. At special sectors, the method of claybank or ground laying might be adopted as well. 4.3.2 The minimum thickness of earth upon the buried pipelines shall accord with the stipulation in table 4.3.2. Protection measure shall be adopted where the thickness of earth cannot satisfy requirements or the external load is too big, or external working may endanger pipelines.

Minimum thickness of earth upon pipelines (m) Table 4.3.2 Earth type Area grade

Dry land Paddy field Rock type

One 0.6 0.8 0.5 Two 0.6 0.8 0.5

Three 0.8 0.8 0.5 Four 0.8 0.8 0.5

Remarks: (1) For earth which is going to be leveled off, it shall be calculated according to the level after leveling off;

(2) The thickness of earth upon pipelines shall be calculated from the top of pipelines. 4.3.3 Pipeline dyke border slope grade shall be confirmed in accordance with earth type and physics character (such as adhesive force, internal friction angle, humidity, capacity etc.). Where the materials of above earth physics character are not available, the border slope might be confirmed according to table 4.3.3 for pipeline dyke where the earth constitution is uniform, no underground water, hydrological and geological conditions are good, the depth is not deeper than 5m and no brace is used. For pipeline dyke which is deeper than 5m, the border slope can be made gentle or flat

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roof can be built. Pipeline dyke border slope grade allowed Table 4.3.3

The steepest border slope grade Mechanical excavation

Earth name Manual excavation

Excavation under dyke

Excavation above dyke

Common and coarse sand

1:1.00 1:0.75 1:1

Sub-sand soil, soil with scree and gravel

1:0.75 1:1.00 1:1.25

Sub-clay soil 1:0.67 1:0.75 1:1.00 Sub-sand soil, soil

with clayey 1:0.5 1:0.67 1:0.75

Clay, marl, malm 1:0.33 1:0.50 1:0.67 Dry loess 1:0.10 1:0.25 1:0.67

Powder silver sand Non-mantlerock

1:1.00 -- --

Hypo-loess 1:0 1:0 1:0 Remark: Still load mean cumulated soil or materials, dynamic load is operation with mechanical excavation, pipelayer and bulldozer. 4.3.4 Pipeline dyke width shall accord with the following stipulation: 4.3.4.1 Where pipeline dyke width should be confirmed according to the external diameter, excavate

method, assembly jointing process and project geogen, etc. When depth is less than 5m, the width of dyke bottom shall be calculated according to the following formula:

B=D+K (4.3.4) In the formula B------width of dyke bottom (m);

D------external diameter of pipeline (m); K------widened abundance volume of dyke bottom, which is confirmed according to

table 4.3.4. Widened abundance volume of dyke bottom Table 4.3.4

Assemble jointing above dyke Manual arc jointing under dyke

Soil dyke Soil dyke Condition factor With

water in dyke

No water in dyke

Rock crack dyke

Elbow, cold syphon dyke

With water in dyke

No water in dyke

Rock crack dyke

Half auto jointing dyke under dyke

Jointing elbow, syphon and 碰口under dyke

Dyke depth within 3m

0.7 0.5 0.9 1.5 1.0 0.8 0.9 1.6 2.0

K Dyke depth 3~5m

0.9 0.7 1.1 1.5 1.2 1.0 1.1 1.6 2.0

Remark: 1. When the pipe ditch is excavated by machinery and the calculated width at the bottom of the ditch is less than the width of excavator, the width at the ditch bottom shall be calculated according to the width of excavator. 2. When welding the bend, bent pipe and joints in ditch, semi auto welding points, the extended

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width shall be 1 meter on the both side of the welding point.

4.3.4.2 Where pipeline dyke need to be braced, the confirmation of the bottom width shall include the thickness of the brace structure. 4.3.4.3 Where depth of pipeline dyke is more than 5m, the dyke bottom width shall be confirmed according to earth type and physics character. 4.3.5 At sectors of rock and gravel the pipeline dyke bottom shall be 0.2m deeper excavated compared to sector of soil. The 0.2m deeper space shall be leveled up with silver sand or sand before pipelines are laid in. Where the pipeline dyke is backfilled, 0.3m above the top of pipelines shall be backfilled with silver sand, and then soil, sand and gravel whose granule diameter is fewer than 100mm, are used to continue to backfill and finally are pressed solidly. The backfilling earth shall be 0.3m higher than ground. 4.3.6 At unearthed points and two sides of elbow of trunkline, backfilling shall be bedded and tamped. 4.3.7 Where the vertical slope of pipeline dyke is bigger, measures shall be adopted according to the soil character to prevent backfilling earth sliding. 4.3.8 For pipelines at sectors of swamp and a network of rivers (including paddy field), where earth upon pipelines cannot surmount buoyancy force of pipelines, pipeline-stabling measures shall be adopted. 4.3.9 Where trunklines are buried in claybank, the height and top width of claybank shall be confirmed according to landform, engineering geology, earth type and its character, and shall be in accordance with the following stipulations: 4.3.9.1 The thickness of earth upon pipelines in claybank shall not be fewer than 0.6m; the top width of claybank shall be twice more than the diameter of pipeline and shall not be fewer than 0.5m. 4.3.9.2 The border slope grade of claybank shall be confirmed according to earth type and the height of claybank. For claybank of clay character, the quotiety of solid-press should be 0.94-0.97. Where height of claybank is lower than 2m, the border slope grade should adopt 1:0.75-1:1; Where the height of claybank is 2-5m, the border slope grade should adopt 1:1.25-1:1.5. The border slope of claybank, which is submerged, shall adopt the grade of 1:2. 4.3.9.3 The claybank located on slope shall be calculated about its stability. Where natural ground slope grade is more than 20%, measures shall be adopted to prevent backfilling earth sliding along the slope. 4.3.9.4 Where claybank blocks the aerial drainage of surface water or underground water, drainage measures shall be set. Drainage capability shall be designed according to landform and water converge volume which is the flood volume whose 25 years a happen according to flood controlling standard; the measures shall be adopted to prevent current washing out claybank. 4.3.9.5 The saturating character of the backfilling earth of claybank shall be similar. 4.3.9.6 The vegetation along the claybank floor surface shall be eliminated. 4.3.10 When the trunkline go through artificial or natural obstacle (water area, gully, railway, road, etc), shall accord with the concerned stipulations of China’s active standard《Design code for oil and gas transportation pipeline crossing engineering-Underground crossing engineering 》SY/T 0015. 4.3.11 Where buried trunkline is laid parallel with other pipelines and communication cables, the interval between shall accord with the concerned stipulations of China’s active standard《Design code for erosion proofing engineering of steel pipelines and containers》SY 0007.

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4.3.12 The interval between buried trunkline and other pipelines, electric power and communication cables shall accord with the following stipulations: 4.3.12.1 Where trunkline cross with other pipelines, the vertical headroom shall not be fewer than 0.3m. Where it is fewer than 0.3m, firm insulated partition shall be set in between; the pipelines of 10m extending from the crosspoint of both pipelines to both sides shall adopt super-insulated grade. 4.3.12.2 Where trunklines cross with electric power and communication cables, its vertical headroom shall not be fewer than 0.5m. The pipelines and cables of 10m extending from the crosspoint to both sides shall adopt super-insulated grade. 4.3.13 The elbow and siphon which are used for changing pipelines’ direction shall accord with the following requirements: 4.3.13.1The curvature radius of elbow shall be more than or equal to 5 4 times of external diameter and shall satisfy the requirements that pigging device and checking and measuring device could pass smoothly. 4.3.13.2 The minimum curvature radius of on-the-spot cooling siphon shall accord with the stipulations of table 4.3.13.

The minimum curvature radius of on-the-spot cooling siphon Table 4.3.13 Nominal Diameter DN (mm) The minimum curvature radius (Rmin)

<=300 18D 350 21 D 400 24 D 450 27D

>=500 30 D 4.3.13.3 Any part of cooling elbow and siphon shall not have any crack and other mechanical damage. The ellipse degree of its both sides shall be fewer than or equal to 2.0%; the ellipse degree of other parts shall not be more than 2.5%. 4.3.13.4 X-ray checking shall be conducted to the round welding line on siphons. 4.3.14 Pipelines laying with elastic bending shall according with the following stipulations: 4.3.14.1 Pipeline segment shall be used to connect between the pipelines laying with elastic bending and the reversed elastic siphon and between the elastic siphon and manual siphon; straight pipeline segment shall not be fewer than the external diameter of pipeline, and shall not be fewer than 500mm. 4.3.14.2 The curvature radius of pipelines laying with elastic bending shall satisfy the intensity requirements of pipelines, and shall not be fewer than 1000 times of steel pipeline’s external diameter. The curvature radius of pipelines laying with elastic bending on vertical surface shall still be more than the curvature radius of the flexible curve which is caused by the deadweight effect of pipelines. Its curvature radius shall be calculated according to the following formula: (formula and explanations omitted here on page 17 &18). 4.3.15 Drape curve and shrimp curve shall not be used for elbow and siphon. The warp of the interface of two pipelines shall not be more than 3o. 4.3.16 The design of trunkline erosion proofing shall accord with the concerned stipulations of China’s active standard 《Design code for erosion proofing engineering of steel pipelines and containers》 SY 0007 and 《Design code for buried steel pipelines strong electric current cathode protection》SY/T 0036.

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4.4 The setting of block valve

4.4.1 Trunkline shall set line block valve. The position of block valve shall be selected at the places with convenient transportation, wide landform, and higher hypsography. The maximum interval between block valves shall accord with the following stipulations:

the pipeline segments at the area of grade one mainly—not more than 32km; the pipeline segments at the area of grade two mainly—not more than 24km; the pipeline segments at the area of grade three mainly—not more than 16km; the pipeline segments at the area of grade four mainly—not more than 8km.

4.4.2 Block valve may use automatic or manual valve, and shall be able to allow pigging device to go through.

4.5 Pipeline Constructs

4.5.1 When pipeline runs across the special sections such as slopes, rocky area, gulch, canal and so on, it is important to follow the natural conditions and build adequate constructions for protecting pipeline and preventing land erosion.

4.5.2 Retaining wall shall be built when the edge of slope or the soil for pipe laying is not stable. Retaining wall shall be constructed on the solid land formation. 4.5.2.1 Retaining wall shall be provided with drainage holes, the intervals is recommended to be 2-3m, the outer tilt angle is about 5%, the dimension of hole shall not be less than 100 mm x 100 mm. Filtration bed and blind ditch shall be arranged behind the retaining wall; when there is a hill behind the retaining wall, it is necessary to build intercepting ditch, the material of land filling shall be of better filtration quality. As in seasonal tundra area, the filling behind the retaining wall shall be non- frozen expansion materials (such as cinder, gravel and course sand and so on); shrinkage joint shall be set up every 10-20 m. In case of erosive water or cold area, the retaining wall shall be treated by anti corrosion and waterproof. 4.5.2.2 When designing the pressure of retaining wall, it is important to follow the applicable national standard “ Basic Design Standards for Construction Base” GB 50007. 4.5.3 When pipeline runs across the river (ditch) banks that are subject to current scour, it is important to build bank revetment, the design of bank revetment shall comply with the following principles: 4.5.3.1: Bank revetment shall comply with the regulations of flood control and river management. 4.5.3.2: Bank revetment project shall ensure the smooth watercourse; it is not allowed to scour and cross the pipeline section and support pier. 4.5.3.3: Bank revetment project shall be based on the actual situations and make best use of local materials. According to water current and scouring degree, the applicable bank revetment measures can include: jackstone, gabion, grouting, dry walling, concrete or reinforced concrete and so on. 4.5.3.4 The width of bank revetment shall be determined according to real hydrology and geology conditions, but shall not be less than 5 m; the top of bank revetment shall be above the design flood

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elevation (including wave height and impounded level) by at least 0.5m. 4.5.4 When pipeline runs across large steep slope, and because of effects caused by the temperature changes, pipeline may generate big downslide force or pulling force, it is required to set up anchoring piers. 4.5.4.1 Anchoring piers are generally made of concrete or reinforced concrete, and the burial depth of base shall not be less than 1.5 m; 4.5.4.2: the filling around anchoring piers should be rammed layer by layer; dry bulk density should not be less than 16kN/m3 . 4.5.4.3 The contact surface between pipeline and anchoring pier shall have good electric insulation.

4.6 Warning Signs

4.6.1 Along the trunkline, the permanent signs like mileage peg, corner peg, crossing and caution signs shall be set. 4.6.2 The mileage peg shall be set continuously by each kilometer on the left side from the start to the terminal point along the forward direction of gas current. Cathode protection testing peg might be set jointly with mileage peg. 4.6.3 Signs shall be set at both sides of the crossings between buried trunklines and roads, railways, rivers and underground constructions. 4.6.4 Caution signs shall be set at the trunkline segments where there is easier access to vehicles’ collision and damage from human beings and livestock and protection measures shall be adopted as well.

5.0 THE STRUCTURE DESIGN OF PIPELINES AND PIPELINE AUXILIARIES

5.1 Calculation of pipeline intensity and stability

5.1 Calculation of the intensity and stability of pipelines 5.1.1 The pipeline intensity calculation shall accord with the following principles: 5.1.1.1 The intensity design of the buried pipelines shall be confirmed in accordance with the area grade of the pipelines location and the endured changeable and permanent load. When the pipelines go through the areas with earthquake intensity grade 0.1g and above, collation shall be conducted about the pipeline intensity during the earthquake according to state current criterion 《Code for seismic design of oil and gas steel pipeline》SY/ T 0450. 5.1.1.2 Equivalent weight stress which is composed of axis-direction stress and round-direction stress of buried straight trunkline segments shall be fewer than 90% of the minimum yielding intensity of trunklines. The design intensity of trunkline auxiliaries shall not be fewer than the design intensity of the straight trunkline segment connected. 5.1.1.3 Where the steel pipelines used for trunklines accord with the stipulations listed in 5.2.2 of this code, welding line quotiety shall be 1.0.

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5.1.2 The intensity calculation of trunklines shall accord with the following stipulations: 5.1.2.1 The pipeline wall thickness of straight pipeline segment shall be calculated according to the following formula (the calculated pipeline wall thickness shall be rounded up to the nominal wall thicknessδn of steel pipelines): (formula and explanations omitted here on page 21). 5.1.2.2The axis-direction stress of the restricted buried straight pipeline segment and the equivalent weight stress collation shall be calculated according to the formula in Appendix B of this code. 5.1.2.3The heat-expanding stress shall be calculated where the temperature changes greatly. Measures of limit heat-expanding displaconcrete shall be adopted if necessary. 5.1.2.4 The combined stress of elbow which is under the effect of internal pressure and temperature difference, shall be calculated according to the formula in Appendix C of this code. 5.1.3 The minimum nominal pipeline wall thickness of trunklines shall accord with the stipulation in table 5.1.3.

The minimum nominal pipeline wall thickness Table 5.1.3 Nominal diameter of

steel pipeline (mm)

Minimum wall thickness

(mm)

Nominal diameter of steel pipeline

(mm)

Minimum wall thickness

(mm) 100; 150 2.5 600; 650; 700 6.5

200 3.5 750; 800; 850; 900 6.5 250 4.0 950; 1000 8.0 300 4.5 1050; 1100; 1150;

1200 9.0

350; 400; 450 5.0 1300; 1400 11.5 500; 550 6.0 1500; 1600 13.0

5.1.4 The radial stability collation of trunklines shall accord with the requirements of the following formulae. Where trunklines are buried more deeply or external load is bigger, the stability shall be collated according to without-internal-pressure situation. (formula and explanations omitted here on page 22 & 23). In condition of no on-the-spot survey materials, it can be selected according to the stipulation of Appendix D in this code. 5.1.5 The steel pipelines which accord with the stipulated minimum yielding intensity by cold working, later on are heated to over 480oC without time limit or higher than 320oC for more than 1h (except for welding). The maximum pressure that such steel pipelines allow to endure shall not exceed 75% of the calculated result according to the formula (5.1.2).

5.2 Materials

5.2.1 The selection of all the steel pipelines and pipeline auxiliaries using for trunklines, shall be confirmed in accordance with using pressure, temperature, medium character, using district and other elements, and after technical and economical comparison. The used steel pipelines and steel products shall have excellent tenacity and welding capability. 5.2.2 As long as domestic steel pipelines are selected for trunklines, they shall accord with the concerned stipulations of China’s active standard, 《Petroleum and natural gas industries--Steel pipe for pipelines--Technical delivery conditions》GB/T 9711,《Weldless steel pipelines used for transmitting liquid》GB/T 8163, 《Seamless steel tubes and pipes for high pressure boiler》GB/T 5310, 《Seamless steel tubes for high-pressure chemical fertilizer equipments》GB/T 6479.

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5.2.3 The steel pipelines and pipeline auxiliaries used for trunklines shall request the tenacity of materials according to intensity grade, pipeline diameter, wall thickness, welding method and temperature of using environment. 5.2.4 The chiseled mark, slot, nick, concaved mark and the harmful disfigurement on the steel pipeline surface shall be handled according to the following requirements: 5.2.4.1 Where the wall thickness is thinned during trunkline transportation, installation and repairing, the thickness of any point on the pipeline wall shall not be fewer than 90% of the nominal wall thickness calculated according to the formula (5.1.2). 5.2.4.2 The chiseled mark and the slot shall be burnished; “the metallurgical nick” caused by electric arc burning mark shall be burnished. Where the wall thickness of burnished pipelines is fewer than the stipulation of term 5.2.4.1 of this code, the damaged pipeline segment shall be cut. Embedding is not allowed. 5.2.4.3 The concaved mark at vertical and round welding line which affects the curvature of steel pipelines, shall be removed. The depth of the concaved mark on other positions shall not be more than 6mm if the nominal diameter of steel pipelines is fewer than or equal to 300mm; the depth shall not be more than 2% of the nominal diameter of steel pipelines if the nominal diameter is more than 300mm. Where the depth of concaved mark does not accord with the requirements, the damaged segment shall be cut. Embedding or knocking to make the concaved mark swell is not allowed.

5.3 Pipeline Auxiliaries

5.3.1 Pipeline auxiliaries shall accord with the following stipulations: 5.3.1.1 Cast iron pieces shall not be used for pipeline auxiliaries. 5.3.1.2 The producing of pipeline auxiliaries shall accord with the stipulation of China’s active standard 《Armor plate welding pipeline auxiliaries》GB/T 13401,《Steel products welding weldless pipeline auxiliaries 》GB/T 12459, 《Steel products welding pipeline auxiliaries 》SY/T 0510. 5.3.1.3 The producing of pigging device receiving and dispatching canister, Pipeline converging, assembly unit refer to state criterion 《Steel pressure vessels》GB 150. 5.3.1.4Where pipeline auxiliaries and pipelines are connected by welding, the material quality shall be the same or similar. 5.3.1.5 The siphon receiving greater weariness load shall not adopt helix welding for pipelines. 5.3.1.6 In condition of on-the-spot intensity testing, leaking, damaging, plasticity distortion shall not occur. 5.3.2 Where pipeline auxiliaries are connected with straight pipelines without axis-direction restriction, the intensity collation of enduring heat-expanding shall be conducted according to the Appendix E of this code. 5.3.3 The pipeline wall thickness of elbow and siphon shall be calculated according to the following formula: (formula and explanations omitted here on page 24). 5.3.4 In condition of opening a hole on the main pipeline directly to connect with branch pipeline or making a three-way pipeline, the weakened parts of the holes might be reinforced according to the area. The structure and calculation way shall accord with the stipulation of Appendix F of this code. Where the nominal diameter of the branch pipeline is fewer than or equal to 50mm, the weakened parts might not be reinforced. Where external diameter of branch pipeline is more than or equal to

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1/2 of internal diameter of main pipeline, the standard three-way pipeline piece should be adopted. 5.3.5 The different-diameter tie-in might adopt the two structure forms of with the hem and without the hem. Its intensity design shall accord with the concerned stipulations of China’s active standard 《Steel pressure vessels》GB 150. 5.3.6 Sealing head of pipe might adopt protruding seal or flat seal. The structure, size and intensity shall accord with the concerned stipulations of China’s active standard 《Steel pressure vessels》GB 150. 5.3.7 The selection of the pipeline flange shall accord with the stipulations of China’s active standard. Flange airproof spacer and tightening piece shall be used correspondingly with flange. The design of insulated flange shall accord with the stipulations of China’s active standard《Code for insulating flange design》SY/T 0516. 5.3.8 Pipeline converging and pigging device receiving and dispatching canister shall be produced by factories which have the qualification of producing pressure containers. 5.3.9 The valves used at the key positions of fireproofing district shall have fireproofing character. 5.3.10 The valves needed to go through pigging device and measure inspection or testing instruments shall be full bore valves.

6.0 TRUNKLINE STATION

6.1 Setting Principle of Trunkline Station

6.1.1The setting of the trunkline station shall accord with the requirements of the routes and the gas transmission process design. All kinds of trunkline stations should be constructed jointly. 6.1.2 The position selection of the trunkline station shall accord with the following requirements: 6.1.2.1 Gentle and wide hypsography 6.1.2.2 Convenient power supply, water supply and drain, living and transportation. 6.1.2.3 Shall keep away from the unfavorable engineering geological sector where there is mountain torrents or coasts and other locations where trunkline station setting is inappropriate. 6.1.2.4 The safe distance between trunkline station and the nearby industry, enterprise, storage, railway station and other public facilities shall accord with the concerned stipulations of the active national standard 《Crude oil and natural gas engineering design fireproofing code》GB 50183. 6.1.3 Trunkline station shall have task channels of producing operation and facility maintenance and shall have driveway connected with outside roads. The plan layout, safe fireproofing, internal driveway and driveway connected with outside roads shall accord with the concerned stipulations of the active national standard 《Crude oil and natural gas engineering design fireproofing code》GB 50183，《Specifications for the design fire prevention constructions》 GB 50016, 《Design specifications of general plan for oil and natural gas project》SY/T 0048. 6.2 Pressure Adjustment and Measuring Design 6.2.1 Pressure adjustment and measuring process design in trunkline station shall accord with the gas transmission process design requirements and shall satisfy the working and maintenance. 6.2.2 Pressure adjustment facilities shall be set on the pipelines where the gas source pressure is not stable and gas admission pressure needs to be controlled. Off-take and distribution pipelines and the

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pipeline segment before the measuring facilities needing to control and adjust the gas volume, where the adjustment facilities have set before the measuring facilities, design for the straight pipeline segment before the measuring facilities shall accord with the concerned stipulations of the active national standard. 6.2.3 Gas measuring facility shall be set on the gas admission pipeline of trunkline, off-take pipelines, distribution pipelines and self-consuming gas pipelines in station fields.

6.3 Pigging Design 6.3.1 Pigging facilities should be set in the trunkline station. 6.3.2 Pigging process shall adopt the pigging flow of gas non-stop obturation. 6.3.3 The pass indicator of pigging device shall be installed on the pipeline segment of gas admission and gas-out, indicator shall be installed on the pipeline outside the station according to the requirement of pigging automatic operation, and the indicating sign shall be sent into trunkline station. 6.3.4 The structure of pigging device receiving and dispatching canister shall satisfy the requirement that it can pass through the pigging device or inspecting device. The design of the pigging device receiving and dispatching canister and Quick opening closure shall accord with the concerned stipulations of the active national standard 《Design technical specifications of the pigging device》SY/T 0533, 《Quick opening closure 》SY/T 0556. 6.3.5 The quick opening closure on the pigging device receiving and dispatching canister shall not face straightly the residential district or construction district whose interval is fewer than or equal to 60m. 6.3.6 The feculence eliminated by pigging task shall be collected and manipulated and are not allowed to drain randomly.

6.4 Disposal of Compressor Set and Design Principle of Workshop 6.4.1 Compressor set shall be disposed in the open air or in workshop according to working environment and the requirement for the set. At high and cold district or sand-blown-by-wind district, all-close-in workshop should be adopted; at other districts workshop in the open air or half open should be adopted. 6.4.2 The disposal of compressors and other assisted facilities in the workshop shall be set single-layer or double-layer according to machine model, set power, shape size and maintenance method, etc. and shall accord with the following requirements: 6.4.2.1 The internal between the extruding parts of two compressor sets and the distance between compressor set and wall shall satisfy the requirements of operation, maintenance field and channels. 6.4.2.2 The disposal of compressor set shall be easy for installation of pipelines. 6.4.2.3 Compressor set base shall be designed accord with the concerned stipulations of the active national standard 《Design technical specifications of the base for power machine》GB 50040, and take measures to reduce the vibration and isolate the vibration. 6.4.3 The fireproofing, explosion-proofing and noise controlling of the constructions in compressor station shall be designed according to the concerned regulations of the national active standard. 6.4.4 Each operating layer of compressor room and the operating platform which is 3m higher than the ground (excludes independent engine platform), shall have at least two safe exits and the ladder to the ground. The maximum distance between any point on the operation platform along the central

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line of channel and the safe exit shall not be more than 25m. The channel of safe exit and the channel to the safe zone shall not be blocked. 6.4.5 The construction plane and spatial layout of compressor room shall satisfy the requirement of process flow, facility disposal, installation and maintenance. 6.4.6 The fixed hoisting facility shall be collocated in compressor room for maintenance. Where compressor set is disposed in the open air, in the light structure workshop or set take the hoisting facility by themselves, the fixed hoisting facility cannot be set but shall set the hoisting field and driving channel for movable hoisting facility.

6.5 Compressor station process and the assisted system 6.5.1 Compressor station process flow design shall accord with the requirement of gas transmission system process shall satisfy the requirements of gas dusting, liquid dividing, pressure increasing, cooling, station-skipping, test operation task, set starting, shutdown, normal operation and safety protection, etc. Dividing filter shall be set at the natural gas inlet sector of the compressor station, the disposed natural gas should meet with the requirement of compressor to the gas quality. 6.5.2 The total pressure reduced in compressor station should not be more than 0.25MPa. 6.5.3 Where the temperature of the gas coming out of compressor station is higher than downstream facility, pipeline, and the maximum operate temperature allowed by bury environment of the pipeline, and in order to increase the transmitter efficiency of gas, cooling device shall be set. 6.5.4 Each radial compressor set should be equipped with natural gas flux measurement to prevent it from being surging. 6.5.5 Combustion engine fuel gas system shall accord with the following requirements: 6.5.5.1 Fuel gas pipeline shall be connected out from the main pipeline before the compressor entrance block valve and shall set pressure-reducing and measuring facilities. 6.5.5.2 Fuel gas pipeline shall be set block valve before going into compressor workshop and each combustion engine. 6.5.5.3 Fuel gas shall satisfy the requirement of combustion engine to the gas quality. 6.5.6 The oil system of radial compressor shall accord with the following requirements: 6.5.65.1 Lubrication, and servo oil system shall all be supplied with oil by the main oil tank, and shall be independent system by themselves. 6.5.6.2 The power of set lubricating system should compound of main lubricating oil pump and the assisted lubricating oil pump and emergency oil pump. Where motor is used for the lubricating oil pump, the gas quality of the actuation pneumatic motor shall accord with the requirement of facility producing factory. The oil-out pipeline of the assisted oil pump shall set unilateral valve. 6.5.7 All levels exits of the reciprocating compressor which adopts oil injection lubrication shall set liquid dividing facility. 6.5.8 Cooling system shall accord with the following requirements: 6.5.8.1 The cooling method of gas should adopt air cooling. The pressure lose of gas passing through cooling device should not be more than 0.07MPa. 6.5.8.2 The gas cylinder wall cooling water of reciprocating compressor and fuel gas engine should adopt obturation circulating cooling. 6.5.8.3 The arrangement of cooling system shall consider the adjacent heat abstraction facilities in order to avoid interference.

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6.5.9 the start up of gas turbine shall use electric (hydraulic) motors or pneumatic motor. When

pneumatic motor is adopted, the quality of driving gas and the parameters shall comply with the requirements of the manufacturers. 6.5.10 When compressor station is equipment with compression air system, the compressed air shall meet the requirements of centrifugal compressor, positive ventilation, instrument air, as well as different requirements of air quality and pressure for other facilities. 6.5.11. Fuel gas driven compressor set shall be equipment with inlet air filtration system, the air quality after filtration shall meet the requirements of manufacturers. 6.5.12: Exhaust outlet of fuel gas driven compressor set should be above the air inlet of fresh air inlet system, it is recommended to be located at the upper hand of minimum wind frequency of air inlet. It is important to keep sufficient distance between exhaust outlet and fresh air inlet so as to prevent exhausted air being re-sucked into inlet port. 6.6 Compressor set model 6.6.1The model and number of compressor set shall be confirmed according to the parameters like compressor station’s total flux, total pressure rate, out-station pressure, and gas quality and after technical and economical comparison. 6.6.2 Compressor station shall select radial compressor.Where the pressure rate is high and transmission volume is small, piston compressor should be adopted. 6.6.3 The compressor set of the same compressor station should adopt the same model. 6.6.4 The model selection of compressor motor power shall be confirmed by relating the local energy resource supply situation and after technical and economical comparison. Radial compressor should adopt combustion turbine, and reciprocating compressor should adopt combustion engine. 6.6.5 The power needed by drive facility shall match with compressor. The power for driving facilities shall match the power of compressor. Onsite power of driving facilities shall have adequate redundancy and can satisfy the different working condition requirements for seasonal temperature changes and different sea levels, as well as overcome the power decrease (castdown) caused by increased operation years and other reasons. The shaft power of compressor can be calculated according to the Formula in Appendix G. The axis power of compressor can be calculated according to the formula in Appendix G. 6.6.6 When the prime mover of compressor is frequency [speed] control motor, the power supply/distribution shall meet the regulations of applicable national standards “Power Supply Standards for General Electrical Equipment” GB 50055. The harmonic impact on public electric grid and quality of power supply shall meet the regulations of applicable national standards “Quality of Power Supply and Public Electric Grid Harmonic” GB/T 14549, otherwise it is recommended to select exclusive frequency motor.

6.7 Compressor set safety protection 6.7.1 Safety valve and relief valve shall be set between reciprocating compressor exit and the first block valve; the relief capability of safety valve shall not be less than the maximum relief volume of compressor. 6.7.2 Each compressor set shall set the following safety protection facilities: 6.7.2.1 Compressor gas entrance shall set pressure upper limit, lower limit alarm and upper limit exceeding shutdown facility. 6.7.2.2 Compressor gas exit shall set pressure upper limit, lower limit alarm and upper limit

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exceeding shutdown facility. 6.7.2.3 The compressor motor power (exclude electromotor) shall set rotate speed upper limit alarm and limit exceeding shutdown facility. 6.7.2.4 Startup gas and fuel gas pipeline shall set flow limit and pressure exceeding protection measures. Fuel gas pipeline shall set the automatic gas-cut-off and relief facility for shutdown and failures. 6.7.2.5 Compressor set oil system shall have alarm and shutdown facility. 6.7.2.6 Compressor set shall set vibrating monitoring facility and vibrating upper limit alarm, limit exceeding automatic shutdown facility. 6.7.2.7 Compressor set shall set axletree temperature and fuel gas turbine entrance gas temperature monitoring facility, temperature upper limit alarm and limit exceeding automatic shutdown facility. 6.7.2.8 Radial compressor shall set surging vibrating monitoring and controlling facility. 6.7.2.9 The cooling system of compressor set shall set alarm or parking facilities. 6.7.2.10 Compressor set shall set axis displaconcrete monitoring and alarm facility. 6.7.2.11. Dry air sealing system of compressor shall be equipped with release limit/alarm device. 6.7.3. In case of emergency shutdown, the inlet valve and outlet valve of the compressor shall be shutdown automatically, anti surge valve shall be activated; compressor and its piping shall be depressurized. 6.8 Pipelines inside stations

6.8.1 In trunkline station, all the oil gas pipelines shall adopt steel pipelines and steel pipe fitting. Steel materials shall accord with the concerned stipulation of term 5.2 of this code. 6.8.2 Sealed gas and fuel gas pipelines, which are used for compressor sets’ instrumentation, control, sampling, lube oil, centrifugal compressor and so on, shall be made from stainless steel and fittings. 6.8.3 The steel pipeline intensity and stability calculation shall accord with the concerned stipulation of term 5.1 of this code. 6.8.4 Pipeline installation design in trunkline station shall adopt measures of reducing vibration and heat stress. The stress caused by compressor’s inlet and outlet tubing to the coupling flange should be less than the allowable value of compressor technical conditions. 6.8.5 The connecting method of pipelines shall all adopt welding except that screw thread or flange are needed for connection for installation. 6.8.6 Pipeline shall adopt ground or buried laying and shall not adopt pipeline dyke for laying. 6.8.7 Pipelines should adopt cover for protection while going through driveways. 6.8.8: The pipeline section from the separation equipment of the station to the inlet of compressor shall be flushed internally.

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7.0 GROUND EQUIPMENT FOR UNDERGROUND GAS STORAGE

7.1 General 7.1.1 The design scope of Underground gas storage shall include the process and associated auxiliary facilities of gas production and gas injection wellhead to gas transmission trunkline. 7.1.2 The design process capacity of ground facilities for Underground gas storage shall be determined according to storage and production ability of geological structure, seasonal peak regulating gas volume, daily peak regulating gas volume or emergency gas reserves as specified in Design Trust Deed or in contract. 7.1.3 It is required to choose reasonable and economical peak regulating radius, Underground gas storage shall be close to the center of the load, the radius of peak regulation shall not be more than 150 km. 7.1.4 It is recommended to combine gas injection plant and gas production station; it is recommended that gas injection plant and gas production station are next to the injection/production wells. 7.1.5 the injected gas shall meet the requirements of ground facilities for Underground gas storage and the requirements of geological structure. The export gas shall meet the requirements as defined in Chapter 3.1.2. 7.2 Ground process 7.2.1 Gas injection process 7.2.1.1 Inlet pipeline of compressor shall be equipped with separation and filtration equipment, the treated natural gas shall meet the technical requirement of compressor. 7.2.1.2 According to the geological structure requirements of gas storage center, it is necessary to adopt de-oil measures for injected natural gas. 7.2.1.3 the gas injection volume for each single well shall be metered accordingly. 7.2.1.4 Injection pipeline shall be equipped with block valves for High Pressure and Low Pressure. 7.2.2 Gas production process 7.2.2.1 Gas production system shall be equipped with reliable gas/liquid separation facilities; it is required to provide gas metering and gas analysis equipment for produced gas. 7.2.2.2 Gas production system shall have the device to prevent the generation of hydrated matter. 7.2.2.3 The selection of dehydration process and de-hydrocarbon process shall be made according to the types of Underground gas storage and the comparison of technology and economy. 7.2.2.4 It is necessary to adopt throttle device to control the water dew point and hydrocarbon dew point; it is necessary to equip dual pressure regulation/throttle device. Pressure regulator shall be equipped with noise reduction measure. 7.2.2.5 Gas production process shall make best use of formation pressure; production and injection pipeline shall be united. Gas production system and injection system shall be equipped with reliable block valves. 7.2.2.6 Gas production pipeline shall be equipped with High Pressure and Low Pressure block valves. 7.3 Selection of equipment 7.3.1 The selection of compressor shall meet the following requirements: 7.3.1.1 The sizing, configuration and process of gas injection compressor shall meet the

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requirements as defined in Chapter 6. 7.3.1.2 The preferred gas injection compressor for Underground gas storage shall be reciprocating compressor; At all levels’ outlet of compressor, it is required to set lube oil separators before each cooler. 7.3.1.3 The selection (sizing) of gas injection compressor shall consider gas injection and gas production. 7.3.2 The selection of air cooler shall meet the following requirements: 7.3.2.1 As far as the air cooler of the gas injection compressor driven by fuel gas is concerned, when the engine power is sufficient, it is recommended to use fuel gas driven engine. 7.3.2.2 It is necessary for air cooler to be equipped with vibration alarm and shutdown device. 7.3.2.3 It is recommended to use air induced type air cooler. 7.4 Auxiliary System 7.4.1 The auxiliary system for Underground gas storage shall meet the requirements as specified in Chapter 8 and Chapter 9. 7.4.2 The auxiliary system of the Underground gas storage shall be applicable to the operation and monitor requirements of injection/production well and observation well.

8.0 MONITOR AND SYSTEM CONTROL

8.1 General Regulations

8.1.1 Gas transmission pipeline shall set up metering, surveying and controlling facilities. Monitor system and data collection system shall be installed for complicated pipeline projects.

8.1.2 The SCADA System of gas transmission pipeline shall consist of: main computer system for control and regulating; remote control station, digital communication system; the system shall be open network structure, with commonality, compatibility and extensibility.

8.1.3 Instruments model and control system shall be selected in accordance with gas transmission pipeline’s characteristic, dimensions, and its future development requirements. This final choice shall be confirmed after comparative demonstration of project blueprint, and shall remain consistent.

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8.1.4 SCADA System shall be equipped with high reliability and applicability index. Hot backup is required for the instrumentation and control equipment, which are subject to frequent failure.

8.1.5 The design of control system shall be favourable to production operation and energy saving, as well as minimizing the pressure loss of gas transmission pipeline.

8.2 System Control Management

8.2.1 Monitor of gas transmission pipeline and data collection system shall conform to the following regulations:

8.2.1.1 Shall increase the portion of controllable transmission gas volume in system control.

8.2.1.2 Shall be good at real time response; have consummate PRI interrupt processing function.

8.2.1.3 Shall be agile in man-machine conversation; easy and convenient to operate and maintain.

8.2.1.4 Shall be competent for data communication and capable of system expansion and network connection.

8.2.2 Monitor and data collection system shall establish control centre, the design of which shall conform to the following regulations:

8.2.2.1 Shall be established at a place easily accessible for control management,

telecommunication, and maintenance. 8.2.2.2 The design of control center shall be in accordance with the rules and

regulations stipulated in the Government standing standards, and satisfy the operation of the computer system and operational system.

8.2.2.3 Host computer system shall adopt two-computer hot backup system. 8.2.2.4 The main function of control management system shall include:

(1) Carry out regular scanning of each controlled station in accordance with preset time and adopted access mode; proceed real time displaying, alarming, storage, printing and recording of main operation parameters and status of controlled stations.

(2) Send remote control orders or regulating instructions to controlled stations. (3) Process and analysis data, and instruct operation decision.

8.2.2.5 The host computer system in control center shall be equipped with operation

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system software, monitor and data collection system software, as well as pipeline system application software.

8.3 Controlled Stations

8.3.1 Controlled Stations are recommended to adopt the control system with industrial microcomputer and PLC.

8.3.2 Controlled stations shall distribute and lay construction points in accordance with pipeline process design requirements, and shall acquire functions to satisfy the following rules:

8.3.2.1 Execute the orders of control center. 8.3.2.2 Station’s system operation parameters make itinerant detection and monitoring,

and send main operation parameters and status to control centre. 8.3.2.3 Control and adjust the programs of compressor unit and equipments. 8.3.2.4 Picture display, alarm, printing and recording of the operation status, flow,

peculiarity, and parameters. 8.3.2.5 Data process, operation running and failure diagnose instruction 8.3.2.6 Monitor Stations’ safety and defense system.

8.3.3 Station’s control system shall be able to realize centralized automatic control, site automatic control and manual operation over compressor unit, process instruments and other auxiliary facilities.

8.3.4 Station’s control system shall be able to control the normal and switching operation of centrifugal-flow compressor unit, maintain the preset pressure value of gas compressor station, coordinate the load allocation among units, and monitor the following functions of machine units:

8.3.4.1 The startup/shutdown of the machine units program, program control of auxiliary systems, safety joint lock control over machine units’ valves.

8.3.4.2 Monitor the machine units’ real time status and process parameters. 8.3.4.3 Execute the orders of control center to control and adjust. 8.3.4.4 Monitor the safety protector stipulated in Item 6.7.2 of the Criterion.

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8.3.5 The emergency shutdown of controlled station system (ESD) shall be in accordance with the requirements as follows:

8.3.5.1 In addition to the control point in control room, gas compressor station emergency shutdown system shall set up at least two more separate operation points outside the gas region of the station. Operation points shall be located in safe and convenient places, easy to operate, and marked with distinct symbols.

8.3.5.2 Emergency shutdown system shall be able to execute the following tasks rapidly:

(1) Shut down the valves to station’s entrances or exits, and open the side roads. (2) Open the blown-down valves in the station. (3) Shut down machine units and blow down. (4) Cut off fuel supply and blow down. (5) Cut off power supply with exception to fire control system and contingency

lighting. (6) Start up automatic fire extinguishing system.

8.4 Monitoring

8.4.1 While setting up monitor and data collection system, it is a must that an instrument to online, continuously and automatically analysis gas quality, and an alarm device to alarm while gas quality index exceeds limit shall be installed at the same time.

8.4.2 It is required to continuously monitor and record the important parameters such as process parameters, vital parameters to ensure the safe operation and analytical data of process and so on.

8.4.3 Pressure monitor shall conform to the following regulations:

8.4.3.1 Shall monitor the gas pressure entering or exiting gas compressor station. 8.4.3.2 Recommend pressure regulation to adopt independent regulating mode in

priority. Double loop or multi loop pressure regulating system is suggested to pipelines of continuous transmission.

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8.4.4 Shall monitor the temperature of gas exiting gas compressor station.

8.4.5 Gas flow monitor shall be able to display the disorder position of pipeline due to excess gas supplied, and should take appropriate measures to limit the flow.

8.4.6 When the gas pressure surpasses the set limit and endangers the downstream facilities of gas supply system, it is required to set up reliable safety device. When the difference between maximum inlet pressure and maximum allowable outlet pressure is more than 1.6 MPa, and the ratio of inlet pressure to outlet pressure is more than 1.6, it is recommended to take the following methods:

8.4.6.1 Install 2 sets of safety block valve (device) for each loop in series, and the block valve (device) should have the ability to close quickly and provide reliable block sealing.

8.4.6.2 Install 1 set of safety block valve (device) for each loop in series and 1 set of additional pressure regulator.

8.4.6.3 Install 1 set of safety block valve (device) for each loop in series and 1 set of maximum discharge valve.

8.5 Communication

8.5.1 The communication system of gas transmission pipeline project shall be established in accordance with the demands of production operation and control management, and shall conform to the following requirements:

8.5.1.1 Communication mode shall be decided in accordance with the circulation characteristics of transmission pipelines, and shall be able to satisfy the data transmission requirements and its future development needs put forward by monitor and data collection system.

8.5.1.2 Communication system shall set up spare channels. 8.5.1.3 Communication station shall be located in transmission management units or

stations of all levels alongside the pipeline. 8.5.1.4 Other communication tasks shall be setup in accordance with the requirements

of transmission process. These tasks include: Gas transmission pipeline control & management telephone, telephones among controlled stations, administrative telephone (conference telephone), patrol and contingency telephone, telegram, facsimile, and data transmission and so on.

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8.5.2 Telephone setup shall conform to the following requirements:

8.5.2.1 Telephone exchange is recommended to be installed in communication center,

control center, and gas compressor station; whereas private telephone can be installed in other stations and sites to ensure communication with control center, neighboring stations and other relative units.

8.5.2.2 Production area and auxiliary production area of gas compressor station can install telephone; the range with the danger of explosion should install explosion proofing communication facilities, while personnel engaged in mobile operations can carry portable phone.

8.5.3 Gas transmission pipeline accident rapid repair sites and pipeline itinerant inspection and maintenance sites can be equipped with mobile communication facilities.

9.0 AUXILIARY PRODUCTION FACILITY

9.1 Power Supply

9.1.1 The power supply for Gas transmission station shall be obtained from local power supply system. In condition that power obtainment from such source is either non-economical or non-reliable, Station can provide power for itself. A self-provided power is recommended to use pipeline gas generator or other feasible power supply after economically and technically comparison.

9.1.2 Power voltage shall be decided economically and technically in accordance with the conditions of local power supply system, the electricity load of gas transmission station, the voltage grade of power facilities, and the length of electrical wires as well as other relative factors.

9.1.3 Confirmation of the grade of gas transmission station electricity load shall conform to the following regulations:

9.1.3.1 For gas compressor station, which adopts electricity as gas transmission power,

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and adopts other drives but with the high reliability requirement to the power supply, the electricity load is suggested to be Grade 1.

9.1.3.2 For other gas transmission stations, the electricity load is suggested to be Grade 2. For branch gas transmission stations, the electricity load can be Grade 3 according to the working condition and requirement.

9.1.4 Gas transmission station shall install contingency lighting for accident. The degree of such lighting shall be no less than 10% of the regular lighting used to ensure normal work of main sites.

9.1.5 Power system for control, instrumentation and communication equipments shall install contingency power supply facilities, in case that power cut may influent the normal operation of gas transmission station or may incur accident.

9.1.6 Gas transmission station shall mark off explosion dangerous area in accordance with Government standing standards – “Division of Explosive Dangerous Area for Oil and Gas Fields” SY/T 0025, and shall select and equip electrical facilities and electrical circuits according to the Grade of explosion dangerous area.

9.1.7 The lightning protection of the gas transmission project should meet the following requirements:

9.1.7.1 The lightning protection classification and lightning protection measures shall follow the applicable national standards “Design Standards of Lightning Protection for Buildings” GB 50057, among which, the lightning protection of electrical project shall observe the relevant regulations specified in applicable national standards “Design Standards of Over Voltage Protection” GB 50064.

9.1.7.2 Steel contained equipment and vessels and so on, which are located in the open are of process plant, shall be equipped with lightning protection and grounding. When the thickness of top plate is less than 4mm, a lightning rod (wire) is compulsory.

9.1.7.3 As for the all kinds of electrical and IT equipment located in process plant, the wiring shall be armoured cable, shielding cable or steel tube wiring. When the first and last terminal of the IT wiring need to be connected with the IT equipment, it is required to set up corresponding over voltage (electric surge) protection device. Equipotential bonding and grounding are required at least at the both ends of the metal armour of wiring or steel pipe, as well as in lightning boundary.

9.1.7.4 It is not required to set lightning rod on the top of steel venting standpipe in the gas

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transmission station, but central grounding device is required at the bottom of steel standpipe (including metal anchoring ropes).

9.1.8 The power supply of fire fighting equipment shall follow the relevant requirements of the applicable national standards of “Petroleum And Natural Gas Engineering Design Fire Prevention Standard” GB 50183 and “Petro-Chemical Enterprises Engineering Fire Prevention Standards”

9.2 Water Supply and Drainage

9.2.1 Design plan for gas transmission station water supply shall be in accordance with the requirements for production, living, fire fighting, and water quality. In addition to local water source condition and hydrology information shall be taken into consideration for integrated comparison. Same water source should be used for production, living and fire fighting.

9.2.2 Gas transmission station total water supply quantum shall include water supply quantum for production, for living, for fire fighting (can be excluded if a safety water pool is available), and for irrigating plants and roads, as well as unpredictable water supply. Unpredictable water usage can be calculated by 15% - 25% of the daily maximum usage quantum.

9.2.3 Safety water pool shall be setup in accordance with gas transmission station water supply quantum and the credibility of water supply system. While needs to setup safety water pool arises, the following regulations shall be complied with:

9.2.3.1 Shall make full use of landform, and build plateau pool. 9.2.3.2 The cubage of safety pool shall be decided in accordance with quantum

needed for production and water used for the reserve water and fire fighting. Production reserve water quantum shall be decided as the average water usage volume at 8 ~ 24h on the date when water usage is most. Water quantum for fire fighting can be calculated in accordance with Government standing standard – “Fire Fighting Design Regulations for Crude Oil and Natural Gas Projects” GB 50183. Safety pool should equipped with facility to prevent the fire fighting water from be used for other purposes.

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9.2.4 Water quality shall conform to the following regulations:

9.2.4.1 Water supply for production shall comply with the requirements of gas transmission process. Water supply for living shall comply with Government standing standards – “Sanitary Standards for Living Drinking Water” GB 5749. In case water for production and living are using the same supply network, its quality must live up to the standards for living drinking water.

9.2.4.2 The quality and process of recycling water shall be in keeping with the related regulations of Government standing standards – “Design Criterion for Industrial Recycling Cooling Water” GB 50050.

9.2.4.3 Should compressor unit itself is always equipped with recycling water cooling system; the quality of its cooling water shall conform to the requirements set for such units.

Gas transmission station wastewater must keeping with the related regulations of Government standing standards – “Integrated wastewater discharge standard” GB 8978.

9.2.5 The setting of gas transmission station’s fire fighting system and facilities shall be in keeping with related regulations stipulated in Government standing standards – “Design Criterion for Fire Fighting of Crude Oil and Natural Gas Projects” GB 50183

9.3 Heating, Ventilation and Air Conditioning

9.3.1 The design of gas transmission station’s heating, ventilation and air-conditioning shall conform to the related regulations stipulated in Government standing standards – “Design Criterion for Heating, Ventilation and Air Conditioning” GBJ 19.

9.3.2 The calculated temperature standards of winter indoor heating for all buildings shall be in keeping with the following regulations:

9.3.2.1 Buildings for production or auxiliary production shall apply to Chart 9.3.2. 9.3.2.2 Buildings with special requirements shall execute in accordance with its

special needs, or relative criterion. 9.3.2.3 The indoor temperature of other buildings during winter shall conform to

Government standing standards – “Sanitation Standards for Industrial Enterprises Design” GBJ 36.

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Indoor calculated temperature during winter for gas transmission station

production building and auxiliary production building Chart 9.3.2 Building Name Temperature (℃)

Metering Instrument Room, Control Room, Duty Room 16 ~ 18

Pump Rooms, Compressor Room, Ventilation Room 8 ~ 10

Laboratory 16 ~ 18 Mechanical, Electricity, Instrument

Maintenance Room 16 ~ 18

Fire Engine Garage 8 Car Garage 5

9.3.3 Fire heating is forbidden in explosion dangerous areas of gas transmission station.

9.3.4 Ventilation design for gas transmission station production and auxiliary production building shall conform to the following regulations:

9.3.4.1 Parts that are emitting deleterious substance or explosion dangerous gas shall take partial ventilation measures to assure the density of deleterious substance in the building be in keeping with Government standing standards – “Sanitation Standards for Industrial Enterprise Design”, and shall not be higher than 20% of the minimum density of its explosion point.

9.3.4.2 Heat insulation facilities shall be installed for the equipments which emit a large volume of heat.

9.3.4.3 For building that is emitting deleterious substance, gas and heat at the same time, a full-scale ventilation volume shall be calculated by the maximum air volume needed to eliminate the deleterious substance, gas and residual heat. In case the quantum of deleterious substance, gas or heat can not be decided, the full-scale ventilation times shall conform to the following regulations:

(1) For air compressor room, ventilation is suggested to be 8 times/hour. (2) For chemical laboratory, ventilation is suggested to be 5 times/hours.

9.3.5 Accident ventilation system shall be established for buildings which are likely to emit a great deal of deleterious gas at a sudden. Accident ventilation volume shall be calculated in accordance with process condition, and the status of accident that might happen. In case accident status is hard to define, ventilation shall be 8 times per hour, and volume for each time shall be no less

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than the cubage of the room. Both normal ventilation system and accident ventilation system shall be responsible for accident ventilation.

9.3.6 In addition to the normal ventilation as is stipulated in 9.3.4, air compressor room shall also set up accident ventilation facility to ensure ventilation of 8 times per hour.

9.3.7 Underground or half underground building, which is likely to accumulate gas, shall set up fixed or mobile mechanical ventilation facility.

9.3.8 For underground or half underground building or construction which is located far from gas transmission station, and is likely to accumulate gas but impossible to set up ventilation system, design documents shall clearly state that safety protection measures shall be taken while operation personnel or maintenance personnel enter the above said building or construction.

9.3.9 In the event that normal heating and ventilation facility can not meet the indoor temperature or humidity standards required by production course, process equipments or instruments, air conditioning facility can be installed in accordance with practical needs.

10.0 WELDING, INSPECTION, PIPELINE PIGGING AND PRESSURE TEST

10.1 Welding and Inspection

10.1.1 The welding installation and inspection requirements stipulated in this Chapter apply to

the site welding of gas transmission pipeline and pipeline auxiliaries.

10.1.2 Design documents shall clearly indicate the specifications of gas transmission pipeline,

pipeline auxiliary raw materials, and welding materials, and the model of welding seam

and welding tie-in. Specific requirements for welding techniques, warm-up before

welding, heat treatment after welding and welding inspection shall also be presented.

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10.1.3 Before starting work, Contractor shall conduct welding process test in accordance with

steel grade, welding materials, welding methods, welding process and other related

regulations stipulated in design documents, and shall compile welding process brochure

according to the results of process test.

Welding process brochure, process test content, and testing methods shall conform to Government standing standards – “Execution, Inspection and Approval Criterion for Site Equipments and Industrial Pipeline Welding Project” GB 50236.

10.1.4 Welders should have valid certificates. The qualification test of welders shall meet the

regulations of applicable national standards “Implementation, Check and Acceptance

Standards for Onsite Facilities and Industrial Pipe Welding Project” GB 50236.

10.1.5 The selection of welding material shall be in accordance with the mechanical capability,

chemical component, warm-up before welding, heat treatment after welding and other

conditions of the welded material.

10.1.6 Domestic welding material shall be in keeping with the related regulations stipulated in

Government standing standards – “Carbon and Steel Welding Rod” GB/T 5117, “Low

Alloy Steel Welding Rod” GB/T 5118, “Steel Wire used for Welding” GB 1300 etc.

10.1.7 The type and dimension design of welding line slope mouth shall be able to ensure the

quality of welding tie-in, and meet the needs for pipeline pigging facility to pass through.

Connecting welding tie-in can use single-V mouth, X mouth or other shapes. In the event

that both pipes have the same or different thickness, their welding tie-in shapes shall

comply with the regulations stipulated in Appendix H of this Criterion.

10.1.8 Warm-up and heat treatment after welding of the welding material shall conform to the following regulations:

10.1.8.1 Warm-up and heat treatment after welding shall be decided in accordance with pipeline material capability, welded parts thickness, welding condition and climate condition etc. Shall conform to Government standing standards – “Execution, Inspection and Approval Criterion for Site Equipments and Industrial Pipeline Welding Project” GB 50236.

10.1.8.2 While welding two materials that have different warm-up requirement, the material requiring a higher warm-up temperature shall serve as criterion.

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10.1.8.3 For welded parts requiring warm-up, the temperature among layers in the course of welding shall not be lower than warm-up temperature.

10.1.8.4 For carbon-steel whose thickness exceeds 32mm, its welding seam shall eliminate stress by heat treatment after welding.

10.1.8.5 In case that the two sides being connected by welding tie-in are made of same material but of different thickness, the thicker shall serve as the criterion for elimination of stress.

10.1.8.6 For welded parts of different material, elimination of stress shall be conducted if any one of the materials has such requirements.

10.1.8.7 Warm-up and heat treatment after welding shall be conducted stably and equally. Set temperature shall be maintained during welding and eliminating stress. Heat preservation shall be conducted on areas outside of heating zone.

10.1.9 Inspection and testing of welding quality shall conform to the following regulations:

10.1.9.1 When bending intensity of pipeline is higher than or equal to 20% of bending intensity, its welding tie-in shall be tested by nondestructive test (NDT), or by cutting off the completed welding seam and applying to destructive test.

10.1.9.2 Welding tie-in NDT shall conform to the following regulations: (1) Welded parts all should go through 100% all-round perimeter test by nondestructive test.

By X-ray photograph and ultrasonic crack detection are preferred nondestructive test method. Surface defection on seam can be inspected by magnetic powder and liquid permeation. While adopt ultrasonic crack detection instrument to inspect welding beam by nondestructive test, the selected beam should been gone through all-round perimeter retest by X-ray photograph, the above mentioned welding seam to be retested shall be selected in random from all the welding seam completed by each welder on the day, and shall not be less than the following stated quantity:

5% welding line from First Level Region 10% welding line from Second Level Region 15% welding line from Third Level Region 20% welding line from Fourth level Region

(2) 100% x-ray photograph test shall be applied to gas transmission station pipeline welding seam, crossing water area, high way, rail way pipeline welding seam, and connecting pipeline welding line which has not gone through pressure test.

10.1.9.3 When repeating the examination by radiogram technology, if the quantity of the welded joints cannot meet the requirements of the above mentioned, it is necessary to set an inspection section for each KM, and repeat the examination according to the specified percentage.

10.1.9.4 For welding seam tested by manual ultrasonic detection, the quality inspection and approval standards shall be conducted in accordance with Government standing standards – “Steal Welding Line Manual Ultrasonic Detection Method and Detection

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Results Analysis” GB 11345. LevelⅠis certified. 10.1.9.5 For welding line tested by x-ray photograph, the quality inspection and approval

standards shall be conducted in accordance with Government standing standards – “Steel Melting Welding Connection Tie-in X-Ray Photograph Test and Quality Analysis” GB 3323. Level Ⅱ is certified.

10.1.9.6 For welding line tested by destructive test, sample selection, tested item, testing methods, welding quality shall be conducted in accordance with Government standing standards – “Execution, Inspection and Approval Criterion for Site Equipment and Industrial Pipeline Welding Project” GB 50236.

10.1.9.7 Inspection of welding from preparation, operation process, inspection after welding, beam defects cleaning and rework, inspection for welding project commissioning record, welding project completion inspection requirement shall conform to Government standing standards – “Execution, Inspection and Approval Criterion for Site Equipment and Industrial Pipeline Welding Project” GB50236.

10.2 Pipeline Pigging and Pressure Test

10.2.1 The following regulations shall be conformed to while pigging pipelines:

10.2.1.1 Before pressure test of gas transmission pipeline, pipeline shall be pigged by pigging facility for no less than two times.

10.2.1.2 Temporary pipeline pigging collection and distribution facility and empting vent shall be set up. Whereas, such facilities in the station shall not be used.

10.2.2 Pressure test of gas transmission pipeline shall conform to the following regulations:

10.2.2.1 Gas transmission pipeline strength test and holistic leak test shall be conducted by subsections. Pressure-tested gas transmission pipeline shall be divided into subsections in accordance with the region level stipulated in 4.2.2, and the characteristics of landform.

10.2.2.2 In the event that subsections are certified by pressure test, the welding seam connecting each subsection can be exempt from pressure test after certified by x-ray photograph test and having been switched on in full scale.

10.2.2.3 Subsections of gas transmission pipeline, crossing large and medium sized rivers, rail way, high way above grade Ⅱ , and speed way shall be pressure tested individually.

10.2.3 Strength test of gas transmission pipeline shall conform to the following regulations;

10.2.3.1 Test Medium: Roger Continues 2006/11/28 (1) Pipeline subsection located in first and second level region can take air or water as test

medium. (2) Pipeline subsection located in third and fourth level region, and process pipeline located

within gas transmission station shall take water as test medium.

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(3) The all the conditions meet the above mentioned table 10.2.3; Test the pressure by air can be applied to the process pipelines sections in level 3 and level 4 areas and the process pipeline in gas transmission station.

10.2.3.2 When all conditions in Table 10.2.3 have been provided, the pipelines in 3 and 4 class areas and in the gas transmission stations can use air to try the pressure.

Table 10.2.3 Air pressure trial conditions for pipelines in 3 and 4 class areas and in the gas transmission stations Hoop stress when in pressure trial

3 class area 4 class area 50‰ 40‰

The maximum operation pressure shall not exceed the 80% of maximum filed trial pressure

The pipes for trial shall be new, and the welding factor shall be L.0

10.2.3.3 Test Pressure:

(1) Subsection in first level region shall not be lower than 1.1 times of designed pressure. (2) Subsection in second level region shall not be lower than 1.25 times of designed pressure. (3) Subsection in third level region shall not be lower than 1.4 times of designed pressure. (4) Subsection in fourth level region and process pipeline in gas transmission station shall

not be lower than 1.5 times of designed pressure. 10.2.3.4 The stable pressure time of the test shall not be shorter than 4 hours.

10.2.4 Leak test shall be conducted after strength test is proven to be certified. With air as test

medium, when test pressure reach design pressure and stable pressure time reach 24 hours

without leak, the test is certified.

10.3 Dryness

10.3.1 After pipeline goes through the pressure test and pigging operation, it needs to be dried. It is required to use water absorptive foam pig to absorb, dry gas (including compressed air and nitrogen gas) to purge, vacuum evaporate, inject glycol hygroscopic agent to wash, etc, to dry the inside of pipeline. 10.3.2 One or more of above methods can be used to dry the pipeline according to local conditions and current techniques, to be economical and easy for operation, and have minimum environmental pollution. 10.3.3 Check and acceptance of dryness 1. When use dry gas to purge the pipeline, it is necessary to set a dew point analyzer on the end of pipeline, the dew point of discharged gas after drying shall be continuously for 4h at the temperature of 5℃ less than the minimum environment temperature under pipeline transmission condition, and the scope of variance shall not be bigger than 3℃. 2. When use vacuum method, the accuracy of vacuum gauge shall not be less than class 1, the dew point of discharged gas after drying shall be continuously 4h lower than –20℃, equivalent to 100 Pa air pressure (absolute). 3. When use glycol hygroscopic agent, the water content in glycol discharged from the end of pipeline after drying shall be less than 20%.

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10.3.4 After drying, if the pipeline does not put into production straight away, it is necessary to fill in nitrogen gas, and seal the pipeline to let its inside pressure bigger than 0.12-0.15MPa under dry condition, to prevent outside moisture re-enter into the pipeline, otherwise it needs to dry the pipeline again.

11. Energy Saving, Health Protection and Labour Safety Health

11.1 Energy saving 11.1.1 Project design shall abide by “Energy Saving Law of P.R. of China” and country’s other applicable regulations and standards. 11.1.2 The technical design of gas transmission shall fully use the gas pressure of pipeline, minimize the pressure loss and improve the transmission efficiency, and reduce energy consumption. 11.1.3 The technical design of gas transmission shall also minimize gas vent out by selecting the pipeline fittings, valves and other parts of good sealing performance, to avoid the leaking of gas. 11.1.4 The technical scenario of gas transmission shall be optimized, to improve self-control capability, reduce energy consumption. 11.1.5 Select the new mechanical, electrical and thermal equipment and products of high efficient energy saving, strictly prohibit the use of out of date products according to national standards. 11.1.6 When combustion gas turbine is selected as the prime engine of compressor, it is better to use the combined power supply system of thermoelectricity and thermal power according to environmental conditions; when electromotor is used as the prime engine, it is better to use frequency speed control technique according to real necessity, to improve the comprehensive usage of energy efficiently. 11.1.7 According to the natural environmental conditions where the pipeline is going through it is recommended to properly use the local energies such as solar energy, wind energy, geothermal energy, and other useful energies. 11.1.8 Fully use natural daylight and natural ventilation, use newly developed type of energy saving construction materials, to reduce the constructions’ energy consumption. 11.1.9 When use oil, gas, water, electricity, and steam, etc, the metering instruments shall be installed. 11.1.10 Comprehensive energy consumption analysis shall be carried out for the engineering design, including integrated energy consumption calculation and unit energy consumption comparison. 11.2 Environmental protection 11.2.1 The design of gas pipeline construction project shall abide by the “Environmental Protection Law of P. R. of China” and the “Water and Soil Conservation Law of P. R. of China”, shall be in accordance with relevant environment protection regulations constituted by country, local governments or petroleum/gas industry. 11.2.2 Selection of routes and station locations of pipeline shall keep away from residential areas, water-source reserve, scenic spots, historical sites, natural protection reserves, important protected sites of underground culture relic, etc. For the damages of soil, vegetation, and landform, shall take effective measures to recover them, and properly plant vegetation at the transmission stations.

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11.2.3 The wastewater and waste gas and other waste residues from transmission stations shall go through nuisance free treatment or disposal, and they shall conform to following requirements: 11.2.3.1. Drainage of wastewater shall conform to the item 9.2.5 of this specification. 11.2.3.2. Exhaust of waste gas shall conform to the country standards “Integrated Exhaust Standards

for Air Pollutants” GB16297. 11.2.3.3. Harmful wastes (residues or liquids) shall be buried after proper pretreatment. 11.2.4 Protection and treatment for the noise of transmission stations shall conform to the country

standards ‘Noise Standards at Factory Sites for Industrial Enterprises” GB12348 11.3 Labor safety/hygiene 11.3.1 The design of gas pipeline construction project shall abide by the “Safety Production Law of P. R. of China”, the “Petroleum/Natural Gas Pipeline Safety Supervision and Management Regulations” of state’s Economy & Trade Commission, the “Pressure Pipeline Safety Management and Supervision Regulations” of state’s Department of Labor, “Construction Project (Engineering) Labor Safety/hygiene Supervision Regulation”, “Petroleum/Natural Gas Industry Health, Safety and Environment Management System” SY/T 6276, and other practical standards. 11.3.2 Design of Labor Safety/hygiene shall be carried out in accordance with the project’s characters, including following items: 11.3.2.1. Identify the main hazards, harmful elements and vocational hazards coming from the

construction project. 11.3.2.2. Carry out qualitative and quantitative analysis on various hazards, harmful elements and

vocational hurts coming from natural environment, project construction and production. 11.3.2. 3. Present relevant practical, economical and reasonable labor safety/hygiene strategies and

protective measures. 11.3.2.4. Labor safety/hygiene facilities and expenses.

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APPENDIX A Process Calculation of Gas Transmission Pipeline (pg 50 – 51)

A.0.1 If gas transmission pipeline comparative height difference along the line ⊿h≤200m,and

omit the affection of comparative height difference, the following formula shall be applied:

In the formula qv ------ Tthe flow (m3/d) of gas (P0 = 0.101325MPa, T=293K) d ------ Internal diameter of gas transmission pipeline P1, P2 ----- Pressure (absolute) of jumping-off point and end point of the calculated subsections of gas transmission pipeline (MPa) Z ------ Gas compression coefficient T ------ Average gas temperature (Km) L ------ Length of the calculated subsections of gas transmission pipeline (km) ⊿------- Relative gas density E ------ Efficiency coefficient of gas transmission pipeline (When pipeline nominal diameter is DN300 ~ DN800mm, E is 0.8 ~ 0.9; when pipeline nominal diameter is bigger than DN800mm, E is 0.91 ~ 0.94.) A.0.2 If gas transmission pipeline consider the affection of comparative height difference along the line, the following formula shall be applied:

In the Formula α----- Coefficient (m -1), Ra ----- Gas Constant of the air. Under standard status, Ra = 287.1m2 / (s2·K)

⊿h ----- The standard height difference from the end-point to the jumping-off point of calculated subsection of transmission pipeline. (m)

n ----- The number of calculated subsections along the pipeline. Calculated subsections shall be counted from the starting point of the gas transmission pipeline and all the way along. One part of the pipeline, when the relative height difference of its starting point and its end point is ≤200m, is deemed as one calculated subsection.

hi, hi-1 ----- The standard height difference between the end point and starting point of the calculated subsection (m).

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Li ----- The length of calculated subsections (km).

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APPENDIX B Stress Calculation and Equivalent Weight Stress of Axis Direction of Restricted Underground Straight Pipeline Subsection

(pg 52) B.0.1 Axis Direction Stress caused by internal pressure and temperature shall be calculated according to the following formula:

In the formula: σL ----- Pipeline Axis Direction Stress. Pull Stress is positive, and press stress

is negative (MPa); µ ----- Poisson's ratio, is 0.3;

σh ----- Pipeline Ring Direction Stress caused by internal pressure. (MPa)

P ----- Pipeline design internal pressure (MPa) d ----- Pipeline internal diameter (cm)

δn ----- Pipeline nominal wall thickness (cm) E ----- The modulus of elasticity for steel material α ----- Linear expansibility of steel material (℃-1) t1 ----- Pipeline temperature while put in tunnel and backfill (℃) t2 ----- Working temperature of pipeline B.0.2 Controlled heat expansion straight pipeline subsection shall calculated equivalent weight stress according to biggest shearing strength theory, and shall satisfy the following formula:

In the formula σe ----- equivalent weight stress (Mpa)

σs ----- lowest bending strength of pipeline (MPa)

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APPENDIX C Calculation of Elbow Build-up Stress under the Combine Effect of Internal Pressure and Temperature Difference

(pg 53 – 54)

C.0.1 When the ring direction stress σh that the elbow is receiving is lower than allowed stress [σ],

build-up stress σ shall be calculated in accordance with the following formula:

In the formula σe ----- Elbow build-up stress under the combined effect of internal pressure and

temperature difference (MPa)

σh ----- Ring direction stress caused by internal pressure (MPa)

σb ----- Strength limit of material

P ----- Designed internal pressure (MPa) d ----- Internal diameter of elbow (cm) δb -----Wall thickness of elbow (cm)

[σ] ----- Allowed stress of material (MPa);

F ----- Design coefficient, selected according to Chart 4.2.3 and Chart 4.2.4 Φ ----- Welding beam coefficient. If steel pipe is selected in accordance with the

requirements stipulated in 5.5.2, φ is 1.0 t ----- Temperature decrease coefficient. When temperature is lower than 120℃,

t shall be 1.0;

σs ----- Bending limit of material (MPa)

σhmax ----- Biggest ring direction stress caused by heat expansion of bend

quadrature (MPa) βq ----- Enhanced coefficient of ring direction stress γ ----- Average radius of elbow section (m) R ----- Bending radius of elbow (m)

42

λ----- Elbow parameters

σ0 ----- Ring direction stress caused by heat expansion of bend quadrature

(MPa)

Ib----- Inertia quadrature of elbow section (m4)

M ----- Heat expansion bend quadreature of elbow (MN.m).

43

APPENDIX D Design Parameter for Laying Pipeline Conditions (pg 55)

Design Parameter for Laying Pipeline Conditions Chart D Laying Type

Laying Condition E(MN/m2)

Bedding Angle (°)

Bedding Parameter K

Type 1 Pipeline to be laid on undisturbed earth, backfill soil incompact

1.0 30 0.108

Type 2 Pipeline to be laid on undisturbed earth. Earth below pipe’s midline to be pressed firm gently

2.0 45 0.105

Type 3 Pipeline to be put into a padding layer of incompact soil, which shall be no thinner than 100mm. backfill soil below pipe top to be pressed firm gently

2.8 60 0.103

Type 4 Pipeline to be put into a padding layer of sand screen or detritus. The top of padding layer shall be at 1/8 above the bottom of pipe, but shall not be shorter than 100mm. The density of backfill soil below top is about 80%.

3.8 90 0.096

Type 5 Pipe below the midline to be put into firmly pressed clay soil. Backfill soil below the pipe top to be tamped, and density is about 90%.

4.8 150 0.085

Note: ① If its pipe diameter is equal to or bigger than DN750mm, the pipeline is not

suggested to be Type 1. ② Bedding Angle parameter refers to arc angle by the counteractive of pipeline and

bedding soil.

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APPENDIX E Pipeline Accessories Buildup Stress Calculation caused by Expansion

(pg 56 – 59) E.0.1 In Gas transmission Pipeline system, when straight pipeline subsection has no axis direction restriction (e.g. fixed nog or other anchor fitting), the pipeline accessories become bend or retorted due to heat expansion, thus resulted buildup stress shall conform to the requirement of the following formula:

Of which:

óe—Combined stress (MPa);

ós—Minimum yield strength of the steel pipe (MPa)

ómp—Bend resultant stress (MPa);

ót3—Twisting stress (MPa); Mb—Bending moment (N.m); Mt—Torque (N.m); I—Bending stress amplification coefficient of Pipe (refer to the Table E.0.1); W—Section factor of the steel pipe (cm3).

When the steel pipe can not meet óe≤0.72 ós, it it necessary to enlarge the thickness of pipe wall.

45

Pipe Fitting Bend Stress Enhanced Coefficient Chart Chart E

Stress Enhanced Coefficient Title In Plane Ii Out Plane Io

Flexibility Characteristic

Simple Drawing

Elbow or bent pipe (refer to drawing)

R- bent semi diameter

Pull Mode Tee (refer to drawing) 0.75I0+0.25

4.4 δ / ν

Tee with fortified belt (refer to drawing)

0.75I0+0.25

Overall fortified Tee (refer to drawing)

0.75I0+0.25

δ / ν

Connecting welding tie-in, connecting welding tie-in of different pipes, connecting welding flange

1.0 1.0 δ / ν

Flat welding of both surfaces, and welding flange

1.2 1.2 δ / ν

Angle-welded tie-in or single surface flat welding flange

1.3 1.3 δ / ν

Note: For pipeline auxiliaries, stress enhanced coefficient I apply to bend on any surface, and its value is no less than 1. These two coefficients are applicable to the whole arc and the connection of tee of an arc tie-in. E.0.2 In thin wall elbow and siphon of big diameter, internal pressure distinctly influences the enhance stress coefficient. Therefore, original stress enhance coefficient shall divide formula (E.0.2).

……………. (E.0.2).

In the formula P ---- the internal pressure that pipeline fitting is enduring (MPa); Ec --- the flexible modulus in room temperature

46

APPENDIX F Structure and Calculation for Tee and Strength Compensation for Drilling Hole

(pg 59 – 61) F.0.1 Tee or drilling a hole directly in pipeline to connect with branch pipeline, the part weakened by the hole can be compensated by equal area according to strength compensation principle. Its result shall satisfy the formula (F.0.1 – 1).

In the formula (Omitted note) F.0.2 Strength compensation for pull mode tee. (Drawing F.0.2) (Omitted Drawing F.0.2 and note) For tee chose main pipe has pull mode wrench tie-in and connect with branch pipe, when choosing tee and branch pipe, must have A1+A2+A3 ≥ AR. Herein with A3=2γ0(δ0 - δl). In the drawing, the area marked by the line between the two dots is effective strength compensation area. F.0.3 Strength compensation for all-round thickened tee (Drawing F.0.3) (Omitted Drawing F.0.3) The structure of all-round thickened tee is the wall thickness of main pipe or branch pipe increases, or the wall thickness of main pipe and branch pipe increases at the same time to satisfy: A1+A2+A3 ≥ AR. Herein with, A3 is the welding seam acreage within the strength compensation area. The symbol marked in the drawing is the same as that in F.0.2. F.0.4 Partial strength compensation for hole drilled. (Drawing F.0.4) When hole is drilled in the pipe direct to connect with branch pipe, the strength compensation for the part weakened due to the drilled hole must achieve A1+A2+A3 ≥ AR. Herein with, A3 is the sum of strength compensation acreage provided by compensation fitting and the welding seam acreage within the strength compensation area. The strength compensation structure shall also conform to the following condition: F.0.4.1 The material of compensation fitting shall be the same as that of main pipe. When the allowed stress of compensation fitting steel is lower than that of main pipe material, the acreage of compensation fitting shall increase proportionally at the ratio of the allowed stress of both materials. F.0.4.2 When the main pipe is drilled neighboring holes to connect branch pipes, the distance of the neighboring branch pipes’ centerline shall not be shorter than 1.5 times the sum of two branch pipes’ diameters. When the distance of the neighboring branch pipes’ centerline is short than 2 times and longer than 1.5 times the sum of two branch pipes’ diameters, associated compensation fitting shall

47

be used. The strength compensation acreage between the exterior walls of the two branch pipes shall not be smaller than 1/2 of the total strength compensation acreage needed for drilling hole in main pipe. F.0.4.3 Hole drilling shall avoid welding seam. (Omitted Drawing F.0.4) The symbol marked in this drawing is the same as that in F.0.2.

APPENDIX G The Calculation of Compressor Axis Power (pg 62)

48

G.0.1 The axis power for centrifugal-flow compressor shall be calculated according to the following formula:

In the formula:

(Omit the note) G.0.2 The axis power for reciprocating compressor shall be calculated according to the following formula:

In the formula: (Omit the note)

49

APPENDIX H Types of Pipe-End Welding Tie-In (pg 63 – 65)

H.0.1 Butt welding tie-in type with same pipe-end wall thickness (Drawing H.0.1) (Omit the drawing H.0.1)

(b) Pipe-end standard slope mouth (c) Butt welding pipe fitting standard slope mouth and pipe end (thickness ≤

22.2mm) random slope mouth. Standard slope mouth (d) Pipe and pipe fitting (thickness ＞ 22.2mm) recommended slope mouth (e) (f) Patch up mode for pipe end slope mouth (g)

H.0.2 Butt welding tie-in types with different pipe end thickness and or different material bending intensity. (Drawing H.0.2)

Note: ① When connecting materials has same strength but different thickness, ① in the drawing doesn’t set minimum value;

② The maximum thickness δ2 used in Drawing 2 design shall not be bigger than 1.5δ1 .

H.0.3 Explanation for Drawing H.0.2: H.0.3.1 General Regulations:

(1) Wall thickness outside the connecting pipe tie-in design area shall conform to the design requirements stipulated in the Criterion.

(2) When the bending intensity of connecting pipe is different, the mechanical performance of welding seam metal shall at least equal to that of the steel pipe with higher strength.

(3) The transition between two pipe ends with different thickness can use cone surface, or adopt the welding method shown in the drawing, or use prefabricated transition short section, the length of which shall not be shorter than the semidiameter of the steel

50

pipe. (4) The welding seam edge of the inclined surface shall avoid sharp cut or fluting. (5) Connection of two steel pipes with different wall thickness but same bending

intensity shall also conform to the abovementioned regulations. But the smallest angle of cone surface is not limited.

(6) The requirement for heat treatment after welding shall be decided according to the effective welding seam height value.

H.0.3.2 When the inner diameter of connection pipes is different; the following regulations shall be complied with:

(1) If the nominal wall thickness difference of two pipes with same length is no bigger than 2.5mm, there’s no need for special treatment. Thorough and solid welding will do fine (Refer to Drawing H.0.2a).

(2) If the thickness difference of inner wall is bigger than 2.5mm, and it’s impossible to weld from inside the pipe, the inner side of the pipe with thicker wall shall be cut into cone surface, so as to achieve transition (Refer to Drawing H.0.2b). The angle of cone surface shall not bigger than 30°, and not smaller than 14°.

(3) For steel pipe whose loop direction stress exceeds 20% of bending intensity, and whose inner wall thickness difference exceeds 2.5mm but is no more than 1/2 wall thickness of the thinner pipe, and can weld from inner side of the pipe, cone can be used for transition (refer to Drawing H.0.2c). The height of slope mouth obtuse side of the thicker pipe shall equal to the inner difference of pipe wall thickness plus the height of slope mouth obtuse side of the connecting pipe.

(4) When inner wall thickness difference is bigger than 1/2 wall thickness of the thinner pipe, and can weld from inner side of the pipe, transition can be done by cutting the inner side of the thicker pipe into cone surface (refer to Drawing H.0.2b), or by using a compounding cone-shaped welding seam. That is, take cone-shaped welding seam equivalent to 1/2 wall thickness of the thinner pipe, and from that point, cut the rest section into cone surface (refer to Drawing H.0.2d).

H.0.3.3 When the outer diameter of the connecting pipes is different; the following regulations shall be complied with:

(1) If the outer wall thickness difference is no more than 1/2 wall thickness of the thinner pipe, welding seal can be taken to execute transition (refer to Drawing H.0.2e). However, the ascending angle of the welding seam surface shall be no bigger than 30°, and the two butt connecting slope mouth side shall be corrected melted and welded.

(2) If the outer wall thickness difference exceeds 1/2 wall thickness of the thinner pipe, the exceeding part shall be cut into cone surface (refer to Drawing H.0.2f).

H.0.3.4 When the inner diameter and outer diameter of the connecting steel pipes are different, tie-in design (such as drawing H.0.2g) shall take integrated adoption of the methods shown in Drawing H.0.2a ~ Drawing H.0.2f. At the same time, special attention shall be paid to the accurate

51

position of slope mouth.

52

The Explanation for the Wording of the Criterion (pg 66)

0.1 In order to make a difference to the execution of the Criterion’s articles and clauses, different wording are used for different levels of strict requirements. The narration is as follows:

(1) Wording to express very strict, and cannot violate: Positive wording use “Must”; Negative wording use “Must not”

(2) Wording to express strict, and ought to follow in normal conditions: Positive wording use “Shall” Negative wording use “Shall not”

(3) Wording to express permit and a bit of choice, and shall first follow if condition permit: Positive wording use “recommended/suggested” or “can” Negative wording use “not recommended/suggested” or “cannot”.

0.2 When indicated in the Article that execution must follow a designed standard, criterion or other relative regulations, wording is “in accordance with… regulations” or “shall conform to …”.

53

National Standards of People’s Republic of China

Gas Transmission Pipeline Project Design Criterion

GB 50251 – 2003

Article Explanation

54

1 General Principles 1.0.2 The applying scope of this code is the onshore trunkline engineering design from the terminal station of transmitting gas out to the users. 1.0.3 This explanation is as follows: 1.0.3.1 The workout of this code takes full consideration of the industry construction guidelines and technical and economical policies constituted by the concerned ministries and commissions of China, such as environmental protection, economizing resources, economizing construction land and 《The provisional stipulation about productive construction project professional safety sanitation supervising》 ,《The specific stipulation of reducing cost of petroleum onshore engineering》,《The provisional stipulation about the prophase work of basic construction and civil engineering in earthquake district》,《Some stipulation of the interrelationship between petroleum natural gas long trunkline and railways》,《Some stipulation of handling the interrelationship between petroleum trunkline, natural gas trunkline and roads》 and etc. Meanwhile, it requires the trunkline engineering design to carry out China’s concerned government order, rules of law and pay attention to the change of these government orders and rules of laws, in order to make this code fit China’s concerned technical policy. 1.0.3.2 This code requires the trunkline engineering design to adopt the advanced abroad and domestic techniques, assimilate new scientific achievements, but to conform to China’s situation and focus on practical effect. 1.0.3.3 For large-scale engineering project which is needed to report to the ministry for approval, optimized design shall be conducted generally and the best process parameter shall be confirmed. For projects approved by the corporation itself, the specific engineering situation shall be depended on. For instance, the oil gas field’s rolling development sometimes does not possess the condition for optimized design. 1.0.4 This code only compiles the main engineering part of trunkline engineering. While the erosion proofing engineering, crossing engineering, environmental protection engineering and the concerned engineering designs shall be conducted according to the concerned stipulations of China and the industry standard.

55

2 Terms The terms listed in this chapter and their definitions and scope only apply to this code.

56

3 Gas transmission process 3.1 General regulations

3.1.1 The gas transmission volume of trunkline is influenced by gas source supply fluctuating, users load changing, seasoning temperature difference and pipeline maintenance, etc. Therefore it cannot operate full-load whole year. In order to ensure the annual transmission task of trunklines, gas transmission capability of trunklines is required to have certain abundance volume. Thus this code regulates that the design gas transmission capability of trunklines is calculated by 350d each year. Due to some transmission capability regulated in the design task or the contract is daily transmission value, daily transmission value will be more directly to indicate the pipeline gas transmission capability during process design, so this code add the daily transmission value as the index of designed pipeline gas transmission capability. 3.1.2 The pipeling gas quality standard regulated in this code mainly considers the transmission process, pipeline transmission safety, pipeline erosion and general users’ requirements to gas quality. Pipeling gas has become one of the important energy resources and commodities. The report of the 15th World Coal Gas Conference AI natural gas collection and adjustment branch conference indicated: the natural gas supplied by gas supplying unit shall accord with certain quality standard. Generally speaking, processing is not necessary before smooth transmission, distributing and general users’ requirements. The impurity which effects gas transmission, distributing and using includes: sulfureted hydrogen, water, hydrocarbon condensation and solid impurity, etc.

Dew point: the educt water in trunkline is the main reason of pipeline erosion. Electrochemistry erosion and other erosion will not happen without water. The result of 《The research on low-concentration sulfureted hydrogen causing erosion on steel products》conducted by SiChuan Petroleum Design Institute and SiChuan Petroleum Bureau Gas Transmission Department shows “…… industrial natural gas dehydrated by silica gel will not erode steel products. The erosion sample still remains the original metal polish. The erosion rate is almost equal to zero. It shows that the erosion on steel products will be impossible without water. ……”. The pipeling gas can also improve transmission efficiency after being dehydrated. Pipeling gas dew point is the gas dew point at the maximum possible operational pressure which is put forward by many countries in the world according to different seasons (see table 1). Considering China is with a vast territory and the climate difference is quite great, the requirement to gas dew point is adjustable to local conditions. Therefore this code only regulates the minimum difference between gas dew point temperature and minimum gas transmission temperature.

The criteria and requirements of Canada, Britain, France, Germany and etc Table 1 to transmitting, distributing and using sulfureted hydrogen, hydrocarbon

condensation, water and other impurity content in natural gas

Criteria and requirements

Austria Belgium Canada France Germany

Component Sulfuret mg/m3

Sulfureted Hydrogen

<=6 <=5 23 23 15 <=5

Hydroxyl Sulfuret

Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

_

Sulfuret Alcohol

<=15 <=15 Not regulated

Not regulated

Not regulated

16

57

Total sulfured branch

<=100 <=150 460 115 150 <=150

Aryl hydrocarbon

g/m3

Benzene Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

_

Toluene Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

_

xylene Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

_

Other impurity mg/m3

Compressed engine oil

Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

_

Carbinol Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

_

Glycol Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

_

Hg Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

_

Chlorid Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

_

Dust Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

_

Water content g/m3

Summer (May 1st-

September 30th)

_ _ Not regulated

65 _ _

Winter (October 1st- April 30th)

_ _ Not regulated

_ _

Dew point oC/bar

_ 0oC

Summer -7/40 -8/69 Not regulated

_ -5

Winter below Hydrocarbon

dew point oC/bar

Summer -5/40 -3/above Not regulated

-10/54 Not regulated

G260

Winter 69 Criteria and requirements

Hungary Italy Holand Poland Britain Yugoslavia

Component Sulfuret mg/m3

Sulfureted Hydrogen

20 2 5 20 5 20

Hydroxyl Sulfuret

Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

58

Sulfuret Alcohol

70 <=15 Not regulated

Not regulated

70

Total sulfured branch

100 <=100 150 40 50 100

Aryl hydrocarbon

g/m3

Benzene Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

Toluene Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

xylene Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

Other impurity mg/m3

Compressed engine oil

Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

Carbinol Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

Glycol Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

Hg Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

Chlorid Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

Dust Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

Not regulated

Water content g/m3

Summer (May 1st-

September 30th)

_ _ _ _ _ _

Winter (October 1st- April 30th)

_ _ _ _ _

Dew point oC/bar

-10 +5/ +4.4/ -7/40

Summer -5/40 -8/70 33.7 69 -11/40 Winter /6 -10/33.7 -9.4/69

Hydrocarbon dew point

oC/bar

Summer +25/40 -10/ -3/above Not regulated

+10/69 -5/40

Winter 60 70 -1/69 Hydrocarbon dew point: the main purpose of getting rid of the hydrocarbon of liquid state in

pipeline gas is to improve gas transmission efficiency, and guarantee gas transmission safety. Most of countries in the world regulate the hydrocarbon dew point according to water dew point (see table 1). This code regulates the hydrocarbon dew point of gas according to China’s specific situation.

Sulfureted hydrogen content: generally speaking, where the educt water had been dehydrated from pipeline gas, erosion will not happen. However, in China trunkline is not simply transmitting gas from the start to the terminal point. There are plenty of civil and industrial users along the

59

trunkline. Therefore, in order to ensure the safety of users and environmental protection, the stipulation of sulfureted hydrogen content in pipeline gas after being dehydrated shall accord with content standard of natural gas of second type (i.e. sulfureted hydrogen content shall be fewer than 20mg/m3 to satisfy the standard of civil-using gas) to satisfy the requirements of majority of users. Meanwhile centralized getting-rid-of-sulfureted is more economical.

This code does not regulate the maximum dust content of pipeline gas because there is not appropriate instrument to test the impurity content in gas yet. The principle requirement is put forward only to get rid of solid impurity. 3.1.3 High pressure gas transmission is generally more economical if gas source pressure, construction technical level and pipelines quality can all be satisfactory. For pipelines which is driven by gas well mouth pressure, stratum energy resources shall be fully used to improve the pipeline starting transmitting pressure as much as possible. For trunklines using compressor to improve pressure, the best process parameter shall be selected through optimized design: pressure, pipeline diameter, pressure rate. The confirmation of pipeling pressure shall consider China’s present pipeline-producing level, construction quality and the district safety where trunklines go through, etc. 3.1.4 Trunkline shall have good erosion proofing design to ensure the using life span of trunkline and avoid accidents. Pipeline erosion proofing is composed of external erosion proofing (i.e. prevent soil and environment from eroding metal) and internal erosion proofing (i.e. prevent the harmful medium in the pipeling gas from eroding the metal of internal wall of pipelines). China’s active《Design code for steel pipeline and container erosion proofing engineering》SY 0007 and 《Design code for buried steel pipeline force electric current cathode protection》SY/T 0036 which is constituted according to abroad and domestic practical experiences, put forward the effective methods of preventing pipeline external erosion. Thus this code’s stipulation of trunkline external erosion proofing shall accord with the concerned stipulations of the two codes mentioned above.

The gas which conforms to the stipulation of 3.1.2 of this code will not generally erode the metal of internal wall of pipelines. Where the gas violating the above stipulation is transmitted, other effective measure shall be adopted to prevent the happening of internal wall erosion of pipelines, such as: reducing the water dew point of gas, injecting erosion-slowing preparation or internal coat, etc. Trunkline generally does not allow to improve erosion abundance volume to solve the internal erosion problems due to engineering cost, metal consuming and other economic reasons. Therefore this code regulates: after adopting erosion-proofing measures, erosion abundance volume might not be considered in condition of confirming pipeline thickness. 3.1.5 Trunkline sets pigging facilities for necessary pigging on one hand and for pipeline testing during normal producing on the other hand. The coarseness of pipeline internal wall and the feculence in pipelines are the main reason of lower efficiency of gas transmitting. Since at present pipeline producing, pipeline construction and producing and management situation in China sometimes cannot reach the predicted result, this code puts forward the pigging requirements for trunkline system in order to get rid of the feculence in pipelines and coagulated and educt liquid from production.

The effect of trunkline internal wall coat is obvious. It can not only prevent erosion, but also improve gas transmission efficiency. According to some concerned material, the gas transmission efficiency can be improved by 5%-8% or more. However since at present in China internal wall coat is not widely applied, this code only regulates it might be adopted.

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3.2 Process design 3.2.1 This term add the requirement of the system optimized design. The system optimized design is a process to separately combine all designed parameters and conditions that will affect the process program, so as to form multi process programs, after process calculation and system optimize and comparison, finally confirm the recommended process programs. This has widely been applied at large size gas transmitting pipeline design for China internal. 3.2.2 Select gas transmission process first and then confirm process parameter while constituting project. Pipeline diameter and transmitting pressure can be finally confirmed after process calculation, facility model choosing, and pipeline diameter first selection, and then after technical and economic comparison. Whether supercharging transmitting is necessary shall be confirmed after technical and economic comparison as well. Optimized design is the process of selecting gas transmission process, selecting pipeline diameter, confirming transmission pressure, selecting pressure rate, confirming station distance, conducting technical and economic comparison. The main content included in the process design listed in this term is the four indispensable contents of trunkline process design. 3.2.3 The gas source referred in this term is gas field gas or high pressure manual coal gas, etc. Making full use of gas source pressure is one of the ways for improving gas transmission pressure and is also one measure to economize energy, and has obvious economic effects. As long as the producing and installing process of trunkline itself can reach and accord with technology and economy optimizing conditions, and the pressure of gas source can be guaranteed for longer time, gas transmission pressure shall be improved as much as possible.

Whether trunkline adopts supercharging transmission depends on the length, transmission volume, and diameter of trunklines and other various conditions which are comprehensively analyzed and compared with other projects to be confirmed. The station distance of compressor station depends on the selection of station pressure rate of compressor station. The number of compressor stations depends on the length of trunkline. The station pressure rate and station distance regulated in this term are the recommended numerical value range put forward about the selection of station pressure rate and confirmation of station distance, Where supercharging gas transmission process and radial compressor have been confirmed to be adopted. The station distance design of the compressor station for the future might be improved with the continuous improvement of pipeline producing technology, continuous development of new pipeline producing materials, possible reduction of pipeline producing cost, and possible improvement of pressure rate and power of compressor and producing techniques. Therefore this term does not regulate the upper limit value of the station distance. 3.2.4 This term regulates that compressor model selection shall satisfy two conditions: gas transmission process parameter and operating working situation changes. That is to say Where within the scope regulated by gas transmission process design, compressor changes in combined operation of connecting in series and parallel connecting or station-skipping gas transmission is adopted, the set character can fit to the pipeline character and power machine is required to work within reasonable efficiency scope as well. 3.2.5 The pressure of each off-take station, gas distribution station and last station of trunkline is confirmed by trunkline process design. The transmission pressure and volume of above stations

61

shall be controlled within allowed scope. Otherwise trunkline system will lose balance. Therefore, each off-take station and gas distribution station shall control and limit the volume of off-take, distribution and the pressure. 3.2.6 The gas going into the trunkline shall be tested in order to ensure the gas quality accords with the stipulation of the term 3.1.2. 3.2.7 The wall thickness of trunkline is confirmed according to gas transmission pressure and area grade. There are two possible situations of gas transmission pressure: the pipeline segment pressure caused during normal gas transmitting, and the pipeline segment pressure during changes of working situation. Where some compressor adopts station-skipping measure because its normal operation has been stopped, the upper reach pipeline segment pressure of such compressor will be more than the normal pressure of normal operating conditions. Thus the trunkline system intensity design regulated in this term shall satisfy the requirements of changes of operating working conditions. 3.2.8 The purpose for compressor station setting the trunkline station-skipping side-way valve is to adopt station-skipping measure if necessary. There are three conditions of station-skipping operation: (1) there are accidents happening in compressor station; (2) the power machine and compressor of compressor station need maintenance; (3) the gas transmitting situation of trunkline changes (i.e. the gas transmitting volume of trunkline is reduced).

Pigging station trunkline station-skipping side-way pipelines are normal operating pipelines. The purpose of setting block valve at gas admission and gas-out pipelines of trunkline station is: (1) the operation needs to be stopped because of maintenance of facilities in the station; (2) the operation is stopped because of accidents happening on trunklines or the station itself. Since trunkline needs to be blocked when the operation of trunkline station or trunkline or branch line stops, gas admission and gas-out block valve shall be set. Install position of block valve is according to American regulation 《Gas Transmission and Distribution Pipeline System》 ASME B31.8 and American《US DOT regulations》 49CFR192.

3.3 Process calculation

3.3.1 The design and calculation of the needed main basic materials and data shall be put forward by the pipeline construction unit according to engineering construction conditions and tasks. The materials listed in this term are indispensable for trunkline design and calculation. Without these materials and data, the process design of trunkline will be impossible. 3.3.2 Trunkline basic formulae are adopted for trunkline process design because complicated and accurate calculation are conditional due to the development of calculation technology of modern trunkline design. This formula is obtained by the combination of gas dynamics theory, the flowing movement equation in gas pipelines, continuous equation and gas state equation. Its result can be expressed by the following basic equation: (formula omitted here on page 81). Suppose dh=0 is taken as level pipeline, the above expression can be expressed by the following equation: (formula omitted here on page 81). After calculation and simplification of the above equation, the basic formula for calculating level pipeline is as follow:

62

(formula omitted here on page 82). (1) Where the landform along trunklines is flat, the height difference between any two points is

fewer than 200m, the error will be very small even can be ignored if level pipeline formula is used to calculate. Now level pipeline basic formula (1) can be adopted to calculate. But if the gas transmitting pressure is higher, the pressure due to the gas pile will be higher though relative height is less than 200m, for a sample, when pressure is 6.4Mpa, natural gas with relative density 0.6 will generate a pressure about 0.1Mpa due to 200m gas pile. For explain the application condition of formula (1), this term add the limit condition for “omit the affection of the height difference”.

Where the landform along trunklines is waved, and the height difference between any two points is more than 200m, the gas transmission volume will be affected. Therefore formula (2) shall be used to calculate.

The trunkline whose length is L is treated as being composed of couple straight pipeline segments with different height and average upward or downward slope grade. Suppose the length of each segment is L1, L2, L3 ……Ln, and the pressure is PH, P1, P2, P3 ……Pk, and the altitude is hH, h1, h2, ……hk. If the start altitude is supposed as hH=0, the height difference of each straight pipeline segment is △h1=h1-hH, △h2=h2-h1, △h3=h3-h2 ……and △h=hk-hH. The following formula can be obtained by calculating and simplifying of the above equations: (formula and explanations omitted here on page 82 & 83). (2) The computation unit in formula (1) and (2) will be explained as follow. Besides, see table 2.

Where the natural gas is at standard state, suppose PG=0.7kg/m3. The gas column of 100m equals to the pressure of 700Pa,. It can be ignored. Where landform is waved and height difference is more than 200m, gas transmission volume error caused will be big and cannot be ignored. For instance, in condition of pressure of 7.5MPa, compression coefficient is 0.87, PG=60.3kg/m3 and height difference is 1000m. For pressure of 0.603MPa, such pressure cannot be ignored. Therefore as long as there is any point, which is 200m higher or lower than the start point along trunklines, the effect of height difference on landform has be considered in the calculation of trunkline waterpower.

Where each parameter unit has been given, C value can be obtained, as table 2. C Value Table 2

P L d q C 105Pa km mm 106m3/d 0.332*10-6

Pa m m m3/s 0.0384

The formula listed in the text of this code is obtained by transferring the formula 3.3.2-1 and 3.3.2-2 by legal signs and legal computation unit.

Where the gas flowing state in trunkline is resistance square district, the process calculation is recommended to adopt the formula in Appendix A (originally Panhandle B formula) according to China’s present situation of metallurgy, pipeline producing, construction, producing and management, etc.

One gas transmission efficiency quotiety E is introduced in Appendix A formula. Its definition is (formula and explanations omitted here on page 84).

Gas transmission efficiency quotiety E equals to the rate of the actual gas transmitting volume of trunkline to theoretical calculating volume, showing the extent of actual operating situation straying ideal calculation condition. While designing, the selection of E shall consider the difference between calculation condition and trunkline actual operating condition, in order to ensure that after

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a period of operating, the actual gas transmitting volume can satisfy the design task volume. In America, generally E=0.9~0.96.

The value of E relates with the operating years of trunkline, the cleanness extent inside trunkline, trunkline diameter value, coarseness extent of trunkline wall and etc. If gas quality is strictly controlled, and there is no solid and liquid impurity accumulating in pipelines and there is no erosion on internal wall, the value of E will be higher. Where the coarseness extent equals to the cleanness extent, the coarseness extent of bigger diameter pipeline will be relatively smaller. Thus the E value will be higher than small diameter pipelines.

There is still gap between China’s pipeline producing level, gas quality control and transmitting process and the advanced level in the world. The operating and calculating condition do not apply totally as well. This code recommends that Where nominal diameter of trunkline is DN300-DN800, E value is 0.8-0.9; in condition of DN 800, E value is 0.91-0.94.

3.3.4 Due to the scale of gas transmitting pipeline expanded, the complexity of system increased and gas supply range extended, so the reliability requirement for gas transmitting increased. Unstable working status will largely affect the safety and gas transmitting stabilization, unstable working status is mainly caused from gas supply and usage unbalanced and pipeline system out of order, such as pipeline cracked and leakage, compressor unit out of order and stopped. For analysis the affection of unstable working status to gas transmitting reliability, we should simulate every unstable working status, dynamic calculate to the system, and calculate every joint point’s process parameter and gas storage value, so as to analysis the gas supply and peak molulation capability, emergency self save capability and measures should be taken.

Should provide the gas usage hourly change data (or load index) within one cycle for dynamic calculate the gas usage unbalance. General each week is a cycle. If for accident status, mainly to calculate the pipeline keep continuously gas supply time. The period will change according to accident place, accident character, so this term does not regulate the detail calculate cycle.

3.3.5 Due to many calculate software currently, it should take engineering practice verification before application, so as to assure the reliability of calculated result.

3.4 Safe relief of trunkline 3.4.1 This term consults the stipulation of term 845.1 of America national standard ANSI B31.8 《Gas transmitting and gas distribution pipeline system》(hereinafter referred to as ANSI B31.8). This term regulates that “for trunkline, main pipeline, gas distribution system, user aerometer and connected facilities, compressor station, pipeline gas tank, the container made of pipelines and pipeline fitting and all of the facilities for special purpose, appropriate pressure relief and pressure limit facilities shall be set Where there is control failure of the pressure of the connected compressor or gas source, or other reason, and the pressure of the above facilities exceeds the maximum allowed operating pressure.” 3.4.2 This term consults the stipulation of term 846.21item (C) of America national standard ANSI B31.8. This term regulates “Relief valve shall be set on trunkline in order that each pipeline segment between main valves can be relieved all. The connecting pipeline size and capability set for pipeline relief shall be able to relieve the pipeline in urgent situation as quickly as possible.” 3.4.3 The design pressure of pressure bear facilities and containers is generally confirmed according

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to the maximum operating pressure required by process conditions. Because of misoperation, failure happening on pressure control facilities or fire accidents, etc, the internal pressure of pressure bear facilities and containers may exceed the design pressure. In order to prevent the happening of pressure-exceeding phenomenon, generally safe relief facilities shall be set on pressure bear facilities and containers or the connected pipelines.

In trunkline station, on-the-spot relief is not generally adopted for relief and blow-down gas. They are inducted into the relief pipelines with the same pressure to transmit to the relief vertical pipeline outside of trunkline station for relief. This relief and blow-down method will not only benefit environmental protection but also benefit fireproofing safety.

3.4.4 Item 169 of USA compellent regulation 《United Pipeline Safety Code》part 192 natural gas and item 843.441 of American regulation 《Gas Transmission and Distribution Pipeline System》 ASME B31.8, have regulated for the limit pressure of the compression station as: “assure the maximum operational pressure allowed of compression station pipeline and equipments is not excess 10%”.

England and Europe code 《Natural gas Supply System---Gas Transmission and Distribution Pressure Adjustment Station Functional Requirement》SB ENI2186-2000 have demand for pressure control as below table (table 3).

Comparison of maximum allowed operation pressure, peak operation pressure, temporally operation pressure under regulate valve controlled and allowed maximum incidental pressure within the short period limited by safety equipment: Table 3 Maximum allowed operation pressure (bar)

Peak operation pressure

Temporally operation pressure under regulate valve controlled (TOP)

Allowed maximum incidental pressure within the short period limited by safety equipment (MIP)

MAOP >40 1.025 MAOP 1.1 MAOP 1.15 MAOP 16<MAOP<=40 1.025 MAOP 1.1 MAOP 1.20 MAOP 5<MAOP<=16 1.050 MAOP 1.2 MAOP 1.30 MAOP 2<MAOP<=5 1.075 MAOP 1.3 MAOP 1.40 MAOP 0.1<MAOP<=2 1.125 MAOP 1.5 MAOP 1.75 MAOP MAOP<=0.1 1.125 MAOP 1.5 MAOP 2.50 MAOP

Term 6.3.2.2 of international standard 《Crude oil and Natural Gas Industrial—Pipeline Transmitting System 》ISO13623:2000 (E) regulate: “Incidental pressure within the short period allowed to exceed maximum allowed operation pressure, but this type of pressure occur times and continues period should be limited, and cannot exceed 10% of maximum allowed operation pressure”.

Pipeline system should submit an intensity experiment under the pressure at least 1.1 times of the designed value before put into production, the pressure defined at this code for safety valve is safety, and comply with international standard. 3.4.5 The safe relief and blow-down gas in trunkline station is generally inducted into pipelines to transmit to relief vertical pipeline outside of trunkline station for relief or ejected into atmosphere after burned at he top of the vertical pipelines. The confirmation of exhaust eduction pipeline diameter is generally calculated on the basis of 10% of safe relief pressure as backpressure. 3.4.7 The height of relief vertical pipeline is confirmed by reference of《Crude oil and natural gas engineering design fireproofing code》GB 50183.3.4.8 This term is according to 《Crude oil and natural gas engineering design fireproofing code》GB 50183.

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3.4.9 The stipulation of setting relief vertical pipeline in this term is mainly considered from the aspect of safety. The diameter of relief vertical pipeline is related to the relief volume. The diameter of educing pipeline of relief gas shall be confirmed according to the comprehensive consideration of the relief volume of safety valve and backpressure. Therefore this term regulates that the diameter of relief vertical pipeline shall be more than the maximum diameter of relief educing pipeline.

Siphon is not allowed to be set on the top of the relief vertical pipeline because the reversed thrust caused by ejected gas into atmosphere on the top will cause great bending quadrature to the bottom of the vertical pipeline, and may cause the relief vertical pipeline topple down. This kind of accident happened many times in stations. Therefore this term emphasizes.

The great and asymmetrical reversed thrust caused by gas relief on the vertical pipeline bottom ever caused the accident that the vertical pipeline shook and cracked. In order to prevent the vibrancy caused by this reversed thrust, the siphon between the vertical pipeline and horizontal pipeline and the horizontal pipeline segment near the siphon shall be anchored.

4 Routing

4.1 Routes Selection 4.1.1 This term is the requirement to routes selection put forward according to China’s trunkline construction experience. 4.1.1.1 The cost of pipeline engineering and the cost of steel products are respectively 60% and 85% of the total engineering (the statistics of SiChun and HanZhong trunkline engineering preliminary design). Therefore routes must be confirmed after investigation, analysis, comparison of each project and select the best one finally.

Routes selection shall consider the geographical position of gas admission and gas supply point along the trunkline and deal with the relationship between trunkline and branch line economically and reasonably.

The difficulty of pipeline construction depends on landform, engineering geological conditions and transportation situation along the pipelines. These are all the crucial elements of routes selection. 4.1.1.2 This term is put forward according to the specialty of few infield and big population in China and it embodies the guideline that agriculture is the base. 4.1.1.3 The relationship between the selection of routes, compressor stations, and crossing positions of big and medium-sized rivers shall be handled well on the premise of economy, with reason and safety. 4.1.1.4 Important military facilities and flammable and explosive storages are the attacking target in war. The mutual safety affects a lot. The important cultural relic protection unit in China will cause unredeemable damage to national culture and ancestor’s legacy once destroyed. Therefore, it is regulated that pipelines shall not go through such district which is defined. 4.1.1.5 Trunkline shall not go through by airport, railway station, sea (river) wharf, railway, road tunnel and bridge, national natural conservancy district. If it must go through, it shall get permission from the concerned department and protection measures shall be adopted as well. 4.1.1.6 《Road routes design regulations》JTJ 011-84 has the similar regulations: “Natural gas pipeline shall go through by bridges or tunnels. At special situation, both parties shall negotiate to

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reach an agreement and protection measures shall be adopted.” 4.1.2 The bad engineering geological sector refers to coast, landslide, rock pile, mud-rock flow, swamp, soft soil, gully, river-side sector and the sector with earthquake intensity grade peak acceleration >=0.1g. During many years’ practice, bypassing is generally adopted for the special sectors which affect pipeline safety, is difficult to renovated and need more investment on the engineering. However after engineering manipulation, the appropriate position can be gone through if rock and soil body stability have been ensured and the engineering investment has been economized obviously. 4.1.2.1 For coast of small dimension, after manipulated, appropriate part might be selected to go through in the way of spanning or shallow burying according to many years’ experience if rock and soil body stability have been ensured and the engineering investment has been economized. 4.1.2.2 The handling of trunkline going through sector of swamp and soft soil is regulated consulting the experience of railway perambulation routes selection. There is generally a layer of crust on the top of the soft soil of coastal areas in China, like ShangHai, TianJin, etc. Therefore where pipelines go through such sectors, the top crust shall be fully mad use of not only, but also the area with higher landform, lower underground water level and narrower scope shall be selected to go through in order to benefit construction and maintenance. 4.1.2.3 Where pipelines go through the sector of debris flow, according to the lesson of railway disaster, pipelines shall go through the area beyond the attacking range of debris flow. For individual sector with difficulty of bypassing, after perambulation design demonstration, single-hole spanning can be adopted to go through. 4.1.2.4 Where pipelines go through deep and narrow gully, i.e. the gully bed is narrow, the height difference of two banks is big, bank slope is steep (>25oC) and the shape is like “V”, spanning is more economical to be adopted to go through. Shallow burying might be adopted for shallow and wide gully, i.e. the gully bed is wide, the height difference of two banks is small and the bank slope is fewer than 25oC. 4.1.2.5 Beach, whose water level changes a lot due to tide effect, and desert, whose sand moves, will possibly cause displacement and damage for pipelines by buoyancy and impetus. Therefore this code regulates that pipeline-stabling measures shall be adopted in order to ensure pipeline safety. 4.1.2.6 In earthquake district with strong shock, earthquake will cause various deformation, like earth crack, swollen mound, rupture extrusion or pulling crash, fracture, earth falling, landslide, coast or fluidified sand and etc. Pipelines are not allowed to cross earthquake rupture belt, but China is a country with many earthquakes, geological formation is various and complicated and it is unavoidable to go through active rupture belt. Meanwhile, there are rules to follow about the earthquake position and land deformation. With the improvement of earthquake monitoring forecast level, it is achievable to prevent and reduce the earthquake disaster. Therefore this code regulates in condition of the above district, engineering judgment shall be made cautiously and the district with smaller and narrower faultage displacement shall be selected to go through and reliable engineering measure shall be adopted.

Base on the comparison of earthquake intensity grade to earthquake intensity peak acceleration at 《Seismic Zonation Maps of Ground Motion Parameters》 GB 18306-2001, earthquake intensity grade 7 is equal to earthquake intensity peak acceleration 0.1g.

4.2 Area grade classification

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4.2.1,4.2.2 The large-scale trunkline engineering construction in China started in the 1950s. The pipeline safety guarantee basically followed the large-scale trunkline design model of former-Soviet Union and certain safe distance shall be kept between buried pipelines and residential area, industrial and mining enterprise and independent constructions. Afterward, 《The minimum safe distance, fireproofing distance between buried pipelines and various constructions》 was constituted according to China’s situation. However during the process of implementing, plenty of contradictions were come across and some problems could not be solved even. In the middle 1970s, consulting America national standard ASME B31.8, different design parameters were adopted and corresponding pipeline design were made according to different area grade. At that time, the area grade was not classified according to resident density index, but based on constructions’ fireproofing type. Four types of area grade were classified correspondingly and the design quotiety is consistent with the stipulation of America national standard ASME B31.8. After practicing, it is workable still. This standard regulates to adopt controlling the pipeline’s own safety as the design principle of trunkline on the basis of analyzing abroad standard and summarizing domestic experience. It is stated as follows:

Firstly, two guiding thoughts of pipeline safety guarantee. There are two guiding thoughts of safety guarantee in trunkline construction: the first one is to control the pipeline’s own safety, like America national standard ASME B31.8. Its principle is to control strictly the intensity and strictness of pipelines and their components and run it through the whole process of pipeline design, facility material selection, construction, producing, maintenance, renovation and alteration. Controlling pipeline intensity is used to ensure pipeline system safety and to ensure the safety of constructions around. At present European countries and America mostly adopt this fortifying principle. The second one is to control safety distance, like the “large-scale trunkline” design standard of former Soviet Union. Although it has some requirements about trunkline system intensity, it mainly controls the distance between pipelines and constructions around in order to ensure the safety of the constructions around.

The trunkline design and construction practice of over 30 years in SiChuan province shows that because the population in China is big and the land construction is dense, the trunkline design and construction according to safety distance is very difficult. It is not only difficult to select routes, but even where safety distance has been ensured, it is still hard to ensure the safety of constructions and residents around. For instance, the trunkline (Φ720*8) in FuNa, SiChuan province exploded in 25th Nov. 1979. The pipeline pressure while exploding was 2MPa. The farmhouse which is 150-200m away from the pipeline exploded and caught fire because of the ember inside. 8 farmhouses were burned, and 1 cow and 5 pigs were burned to death. In 1980, the trunkline in Funa was rectified and the pressure retested reached 5MPa. The pipeline exploded and the 400mm*400mm*1000m bar stone in the pipeline dyke flied over 100m away. In April, 1965, the most serious trunkline explosion accident happened in Louisiana, U.S. 17 people died on the spot, 8m of the trunkline blew out, a big delve with length of 8m, width of 6m and depth of 3m was formed, and 5 pieces of steel plates with the weight of over half a ton flied over 100m away.

Secondly, strengthening pipeline’s own safety is the important guarantee of the safety of constructions around pipelines. For pipelines at any district, bearing the internal pressure is safe and reliable. If there is any unsafe element which may cause damage to pipelines, certain measure shall be adopted to ensure the pipeline safety. The main safety measures adopted by European countries

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and America for trunkline design are to reduce pipeline stress level with the increase of public activities, i.e. to increase the pipeline wall thickness, ensuring pipeline’s own safety by intensity in order to supply safety guarantee to constructions around trunklines. The quantity-fixing method of “public activity” is to confirm area grade and to combine trunkline design with the corresponding design quotiety. The OPSR statistics material of America shows that the possibility of pipeline outside force accident of commercial district, industrial district, residential district at areas of grade 3 and 4 is very low. At such areas, the method of reducing pipeline stress is mainly adopted to improve safety degree. According to different area grade, different design quotiety (F) is adopted to ensure the safety of constructions around trunklines. Obviously this method is more applicable than adopting safety distance. It is more flexible to select routes and it is more economical and reasonable.

Thirdly, intensity design quotiety (F). The judgment of pipeline safety is allowed stress valve, and the value will be different in different conditions. Even in the same condition, according to different situation of each country, the value might be different as well. America national standard ASME B31.8 has detailed stipulations about allowed stress value according to using conditions of pipelines. This standard regulates the allowed stress value is 0.4σs-0.72σs before 1992. The maximum allowed stress value (0.72σs) , compared to other using pipelines, is higher than the other pressure pipelines except that it is equal to the allowed stress value regulated in ASME B31.4 《Liquid transmitting pipeline system》. Because where trunkline design adopts design quotiety 0.72, the trunkline shall be at field or some area with few people. Once any accident happens, it will not damage the environment a lot. Meanwhile the pipeline form is simpler than factory pipelines and it is reasonable to have less safety. The minimum allowed stress value (0.4σs) is basically consistent with ANSI B31.3 《Chemical plant and refinery pipelines》. Where design quotiety 0.4 is adopted, pipelines shall be at areas with dense population and buildings and frequent transportation. Because trunkline gathers mass elastic pressure energy, it will cause great damage to environment around once it is broken. Therefore allowed stress value shall be reduced and safety shall be improved in order to ensure the safety of constructions around trunklines. Besides, the maximum distance between pipeline block valves of this district is 8km. If there is any accident happened with trunklines, the relief volume of gas is less than other districts. So the damage is reduced to the minimum. According to plenty of abroad and domestic practice, adopting different design quotiety to design trunkline is safe and reliable in accordance with different area grades. Using pipeline intensity with reason is economical. The design quotiety adopted in this code is consistent with America national standard ASME B31.8, i.e. 0.72, 0.6, 0.5, 0.4.

Fourthly, the classification of area grade. America national standard ASME B31.8 classifies four area grades along trunkline according to residents (constructions) density index. The specific method of classification is within the scope of 1\8 miles (201m) of both sides along the trunkline center, some pipeline segments are classified randomly at the length of 1 mile. Independent residential construction (family) number is calculated within the classified pipeline segment area and this is confirmed as the residents (construction) intensity index of this area and area grade is confirmed according to this index. France fuel gas pipeline safety regulations (version of 1977) just classified three area grades. The standard is within 200m of both sides along pipeline center, the intensity index of houses or dwelling houses are calculated per hectare. The classification standard of other countries and districts can be referred to in table 5.

China is a country with a vast territory and the area of east, west, south and north are quite

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different from each other. According to our many years’ working experience, it is appropriate to classify four area grades according to resident (construction) intensity index and conduct corresponding pipeline design. Meanwhile, based on the actual situation of China, some changes are made about the confirmation of resident (construction) intensity index.

This code adopts that within 200m of both sides along pipeline center, some pipeline segments are classified at the length of 2km. Resident (construction) intensity index is confirmed according to the number (the one with more numbers will count) of the independent residential constructions (family) (see table 4).

China is the most populated country in the world and the population has exceeded 1.1 billion. The distributing of the population is very asymmetrical. The population in the east is dense and there are 300 people per square km in coastal district; the population in the west is sparse and there are only 40 people per square km. On average there are 110 people per square km in China. The population in countryside accounts for about 73.8% of the total population and there are about 87 countryside people per square km. If the number of independent constructions is calculated by 4 people per family in countryside, the resident (construction) intensity index per square km is about 21.7. If calculated by pipeline segment classified sector (0.8 square km) put forward by this code, the index is 17.There are more population in the countryside of SiChuan province and sparsely populated. The pipeline design quotiety adopted before was mostly 0.6, equaling to area grade two. If according to the index stipulated in ASME B31.8, the pipeline length of area grade three in Sichuan improves more. This code regulates the resident (construction) density according to the actual situation in China (see table 3). The area grade classification standard of other countries and districts can be referred to in table 4.

In a conclusion, it is active to ensure the safety of the constructions around by improving trunkline’s own safety and it is more reasonable compared to ensuring the safety of the constructions around by safety distance. It has been adopted by many developed industrial countries. Therefore this code adopts the principle of improving pipeline’s own intensity safety.

AT the standards issued abroad during 1990s’ , there were some cases to increase the design index to 0.8.Canada national standard《Crude oil and Natural Gas Pipeline System 》CSA-Z662-99 regulated: the design index can select 0.8 for grade one area where the living house quantity is equal to or less than 10 families within the continuous length 1.6km and 200m width at 2 sides of pipeline range. At the same time, it regulated the steel pipe except that made according to the Canada standard <Pipeline steel pipe> CAN/CSA-Z245.1 and American standard <Pipeline steel pipe> API 5L, round pressure caused by the designed pressure cannot exceed 72% of the minimum yield pressure. International standard Crude oil and Natural Gas Industrial—Pipeline Transmitting System 》ISO13623:2000 (E) regulate: “where human rarely lived and permanent habitation (such as desert, frozen earth area), round pressure index of natural gas pipeline can increase to 0.83, but the calculation formula of wall thickness in this code is a little different. England and Europe standard <Natural Gas Supply System—basic requirement of the pipeline under maximum operational pressure exceed 16 bar> SB EN11594-2000 regulate the maximum design index <=0.72. From 1992, American regulation 《Gas Transmission and Distribution Pipeline System》 ASME B31.8 classified Grade one area to Grade one class one and Grade one class two, design index for Grade one class one area is larger than 0.72 but less than or equal to 0.8, and explained that this code regulated base on the gas transmitting pipeline operation experience of actual operational stress is higher than applicant stress recommended before B31.8, this regulated when design index is larger

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than 0.8 and test medium is water, intensity test pressure should achieve 1.25 times of designed index. United State compulsive regulation《US DOT regulations》49 CFR 192 natural gas part (1992 version) did not increase the design index for Grade one area, it still keep 0.72.《US DOT regulations》 49 CFR 192 is a United State regulation, 《Gas Transmission and Distribution Pipeline System》 ASME B31.8 is a American national industrial standard, in American, if any conflict between them, should follow《US DOT regulations》.

Increase the design index can reduce the wall thickness and save steel material, economic benefit is obvious. But when increase the design index, steel stress increased, relative safety index reduced, if metallurgy, pipe manufacturing, welding operation cannot assure the quality, large risk will exist. Current, domestic grade on area widely use pipeline which made in China, its metallurgy, pipe manufacturing quality have a deviation with the international standard, in the respect of the manufacture and welding quality inspection still do not achieve to the international level. Moreover, Chinese still have not practice experience of operate the natural gas transmitting pipeline under the allowed stress higher than 0.72. SO, consider of our actual condition, we did not list the design index of 0.8 to this code. 4.2.3,4.2.4 This code regulates that the design quotiety is respectively 0.72,0.6,0.5,0.4 in area grade one, two, three and four. For this kind of mutual relationship, there is some exception in certain circumstance. For instance, the pipeline design quotiety of the special sector of area grade one --- crossing (spanning) rivers, railways, roads and around trunkline stations, cannot be confirmed according to the corresponding area grade. In order to avoid confusion, this term gives clear regulations about various situations. So the appropriate pipeline design quotiety can be selected accordingly.

Where trunkline goes through railways and roads, the concerned abroad and domestic survey shows that setting crossing cover pipeline will have shield effect on cathode protection, improve investment and may cause asymmetrical sinking and some other unfavorable elements. America ASME B31.8 regulates that at area grade one and two, pipelines with or without cover can be adopted to go through railways and roads; at area grade three and four, pipelines without cover can be adopted to go through railways and roads. Former Soviet Union large-scale trunkline CHИП

2.05.06~85 regulates that steel protection pipeline cover shall be set for large-scale trunkline going through railways and roads. France fuel gas pipeline system safety regulations regulate that pipeline cover shall be set while trunkline going through railways and roads.

Each country cannot be consistent with each other about this point. The railway and road department in China cannot agree to the crossing trunkline segment without cover. 《Design code for crude oil long trunkline crossing engineering》(SY/T 0015) in China regulates that the protection pipeline cover shall be set while going through railways of grade I ,II and III and roads of grade I and II. In order to be consistent with the regulations of the active code and consider the suggestions of railway and road department, this term regulates that trunkline with cover shall go through railways, speedways and roads of grade I and II; trunkline with or without cover shall go through roads of grade III and IV.

Area grade classification standard adopted in this code Table 4

Resident (construction) density index Area grade <=15 One <100 Two

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>=100 Three The area where buildings with four floors or

above assemble, has frequent transportation and plenty of underground facilities

Four

Area grade classification standard Table 5

Standard Resident (construction) density

index

Area grade Design quotiety

Class 1 <=0.80 <=10 One Class 2 0.72

<46 Two 0.6 >=46 Three 0.5

America ASME B31.8

The area where buildings with four

floors or above assemble, has frequent

transportation and plenty of underground

facilities

Four 0.4

<=10 One 0.72 <46 Two 0.6

>=46 Three 0.5

Canada CSA Z184

The area where buildings with four

floors or above assemble, has frequent

transportation and plenty of underground

facilities

Four 0.4

<=4 One 0.73 <40 Two 0.6

>=40

Three 0.4

France Fuel gas pipeline safety regulations

Pipelines are in cities or residential districts

Four

<=10 One 0.72 <46 Two 0.5

>=46 Three 0.3

Britain IGE/TDI/1

The area where multiplayer buildings

assemble, has frequent transportation and

plenty of underground facilities

Four Maximum pressure 7 bar

4.3 Pipeline laying 4.3.1 Considering the safety of pipeline, easy maintenance, and no influence on transportation and farming, trunkline shall be buried. The special sector with difficulty of buried laying can adopt onshore laying or claybank laying after design and demonstration. 4.3.2 In order to ensure pipelines in good condition and keep them away from the outside damage

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and not to affect farming, the minimum thickness of earth upon pipelines regulated in this code is put forward according to the trunkline construction experience in China and by consulting the concerned regulations of America, former Soviet Union, Canada and France. 4.3.3-4.3.6 They are constituted by consulting 《Gas and Oil Pipeline Engineering Construction, checking and accepting code》(SY/T 0401-98). 4.3.9 There are few experience about claybank buried laying. It is mainly constituted by consulting the concerned regulations. The building height and width of claybank shall be confirmed according to pipeline diameter, burying depth, local landform, hydrology and geology, engineering geological condition, soil type and character. The building height and width of claybank shall not only satisfy the requirements of burying but also protect the safety of pipelines. 4.3.9.1 The requirement of the minimum thickness of earth upon pipelines in claybank 0.6m and top width not fewer than 0.5m, is confirmed according to the requirement of depth of burying and the border slope grade quotiety adopted by the claybank. 4.3.9.2 Pressing-solid quotiety is confirmed by consulting the requirement of filling groundsill quality controlling value. It is necessary and feasible as the stabling requirement of trunkline claybank construction and claybank border slope. The definition of pressing-solid quotiety is the rate of the controlling dry volume weight of soil rd to the maximum dry volume weight rmax.

The confirmation of border slope grade is mainly according to the physical mechanics character of general clay. The claybank border slope is required to have sufficient stability in natural environment. However there is still few practical experience in this field and more materials need to be accumulated for revision for the future. 4.3.9.3 The natural slope which the crude ground slope is more than 20%, needs to be calculated about its stability according to the railway groundsill design requirements. Although the requirement for pipeline claybank design is less than that of railway groundsill design, the claybank is required to be stable equally. Once the claybank loses stability, it may damage pipelines. Therefore stability calculation is essential. 4.3.9.5 This term is constituted by consulting railway groundsill embankment requirements. 4.3.9.6 The surface plants along claybank floor shall be cleaned up based on the requirements of claybank stability and pipeline erosion proofing. 4.3.11,4.3.12 They are put forward according to the stipulation of 《Steel pipelines and containers erosion proofing code》(SY 0007). 4.3.13 Currently, except the cold syphon, there is curve by intermediate frequency heating. The most economical and effective way to reduce elbow heat-expanding stress is to increase elbow curvature radius. The buried pipelines with bigger difference in temperature shall adopt siphon with big curvature radius. Considering the specific pipeline industry situation in China and pigging device can pass through, the curvature radius of prefabricated elbow shall be more than or equal to 4D.

The trunkline in foreign countries basically adopt siphon machine to cool the siphon on the spot and the minimum curvature radius is more than or equal to 18D. On-the-spot cooling siphon method shall be promoted to achieve pipeline turning if conditions allow. The minimum curvature radius of cooling siphon is put forward according to the siphon machine specifications and technical parameters introduced by ASME B31.8 and Pipeline Bureau of China Petroleum Natural Gas Corporation.

4.3.14 The formula (4.3.14) of this term is deducted based on pipeline’s continuous laying,

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bearing condition being at the middle state between simple crossbeam and embedding at both ends, and flexibility quotiety is 3/384.

4.4 Setting of block valve 4.4.1 The main purpose of setting block valves on trunklines at the interval of certain distance

is for the benefit of maintenance and to reduce damage and prevent accident from expanding Where dilapidation occurs on trunklines. Former Soviet Union 《large-scale trunkline》CHИП2.05.06-85 sets block valve at equal interval and the distance is not more than 30km. Furthermore, block valves shall be set on both banks of rivers, outside gas supply station and compressor station. The block valve interval is 20-30 km of the laid trunkline in Sichuan area. The concerned regulation of Europe and America is to set block valve at different interval and according to area grade. The interval is the longest at area grade one, the secondly is grade two and three, the shortest is grade four. This code is to design trunkline according to intensity safety principle. Therefore at different area, block valve shall be set at different interval according to different area grade and the interval shall be consistent with the stipulation of ASME B31.8.

4.4.2 Where dilapidation accident happens on trunkline, there are two kinds of method to turn off block valve: automatic and manual. According to the introduction of IGC/C-76 《Pipeline automatic block control》: there was a survey on 20 gas transmission corporations in America and the length of operating pipeline was about 225000km. And 12 corporations, whose length is 132000km, accounting for 60% of total, agreed to turn off block valve automatically by pipeline disrepair inspection instrument and manipulating facilities. The other 8 corporations did not adopt this way due to the possibility of misoperation; the fluctuation of system pressure is too big; inspecting system is complicated and this is consistent with PLE trunkline corporation in Germany. ASME B31.8 does not regulate rigidly about adopting automatic or manual way to turn off block valve. The pressure reducing velocity method are often adopted to turn off block valve by trunklines in Sichuan in recent years. This code does not regulate rigidly about this and in the engineering design, the design staff will decide it according to the specific situation.

5 The structure design of pipelines and pipeline auxilaries

5.1 Calculation of pipeline intensity and stability 5.1.1 Intensity design of buried pipelines 5.1.1.1 The intensity calculation of trunkline considers not only the normal internal pressure on

pipelines and external load, but also the external extra stress during earthquake for pipelines going through earthquake district. According to the material provided by Petroleum Trunkline Design Institute, the damage situation of Qin-Jing trunkline during the earthquake in TangShan in 1976 and the damage situation of HuaGe trunkline during the earthquake in HaiXi, QingHai in 1990 show that there is no damage on trunkline if the earthquake grade is below 7. According to the calculation of the term explanation of 《Design code for buried oil and gas pipeline anti-earthquake》SY/T 0450 constituted by China, and review meeting for this code version 1994 for review and finial: the

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earthquake intensity for pipeline protection is confirmed as grade 7 or above. The earthquake intensity was edited at 2002 reversion according to 《Seismic Zonation Maps of Ground Motion Parameters》GB 18306-2001, and confirmed the anti-earthquake design of gas pipeline should according to 《Design code for buried oil and gas pipeline anti-earthquake》.

5.1.1.2 The pipeline wall thickness regulated in this code is calculated according to the third intensity theory. Intensity calculation formula only considers pipeline round-direction stress. Where the transmitted medium has bigger difference in temperature, pipeline stress will increase and it is pressure stress. Therefore the combined equivalent weight stress shall be collated according to double-direction stress state in order to ensure pipeline operating safety.

5.1.1.3 The trunkline intensity calculation before considered a welding quotiety which is less than 1 due to the lack of strict requirement of pipeline producing level, construction and welding in order to ensure safety of gas transmission. This actually increased the steel quantity of pipeline engineering. At present, the pipeline producing techniques have been improved greatly and the new steel pipeline standard, like 《 Petroleum and natural gas industries--Steel pipe for pipelines--Technical delivery conditions》GB/T 9711, is constituted by consulting the standard of America API Spec 5L and the technical requirement is basically consistent. The tenth chapter of this code puts forward the strict requirement of construction, welding and inspection according to the concerned abroad and domestic standards in order to ensure the pipeline operating safety. Therefore this standard regulates that reducing steel products’ design stress because of welding is no more considered and the welding quotiety in intensity calculation is 1.

5.1.2 Intensity calculation of trunkline 5.1.2.1 Former Soviet Union adopted limit bearing capability and calculated intensity of

trunkline according to intensity limit of materials. America national standard ASME B31.8 adopted yielding limit to calculate and were learned by many European and American countries. It is more reliable to adopt yielding limit calculation for trunkline.

Countries in the world all adopt the third intensity theory to calculate the thickness of pipeline wall. In recent years, China has abroad discussion and academic communication about the oil gas trunkline wall thickness calculation and tends to be consistent with adopting the third intensity theory. This code regulates that the straight pipeline wall thickness calculation formula of ANSI B31.8 is adopted. This formula is simple and convenient and has been widely applied in trunkline design.

5.1.2.2,5.1.2.3 Where temperature changes a lot, buried restricted straight pipeline segment shall consider the axis-direction stress caused by the difference in temperature and the combined stress of round-direction stress σh and axis-direction σL shall be collated. There are different choices of the checking computation of pipeline bearing internal pressure and heat-expanding stress. ANSI B31.4 《Oil transmitting pipeline system》adopts the third intensity theory, i.e.:

σe=σh-σL<=0.9σs

Canada and Japan adopt the fourth intensity theory, i.e.: σe=σ2

h-σhσL+σ2L<=0.9σs

Generally speaking, the fourth intensity theory reflects the condition of elastic material causing damage more accurately and it will be a little bit safer if the third intensity theory is used for checking computation. In order to be consistent with pipeline wall thickness, this code recommends to adopt the third intensity theory for checking computation.

5.1.2.4 The fourth item of this term adopts the elbow intensity collation method put forward by

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professor Cai Qiangkang and Lv Yingming in East China Petroleum Institute in the article 《Internal force and stress calculation of buried heat trunkline》. This method is to let the danger calculation stress σe caused by heat-expanding and internal pressure combined be less than the intensity limit of materials σs. Where σh<[σ] is satisfied, σe=σh+σmax<=σs.

The heat-expanding curve square M can be calculated according to 《The approximate analysis of temperature-rising load of buried long trunkline level elbow》 by Cui Xiaobing, 《Internal force and stress calculation of buried heat trunkline》 by Cai Qiangkang and Lv Yingming, 《The intensity research on buried heat trunkline》 by Mechanics Department Mechanics staff room of East China Petroleum Institute or by adopting the electric computation program of Sichuan Petroleum Design Institute.

5.1.3 The minimum pipeline wall thickness. Generally when D/ δ>140, the instability of circle section will happen at normal transportation, laying and burying situation. The minimum nominal pipeline wall thickness (see table 5.1.3 of this code) put forward by this code will not exceed the upper limit of this range.

According to abroad and domestic research, where D/δis not more than 140, rigidity problem will not happen at normal situation.

The pipeline wall thicknessδconfirmed by formula (5.1.2) shall be collated according to various load conditions. If the condition cannot be satisfied, thickness shall be increased or other parameter shall be adjusted. The calculated thickness will be small in condition of smaller bearing internal pressure. At this time, the minimum nominal pipeline wall thickness shall accord with the stipulation of table 5.1.3 of this code in order to satisfy the requirements of transportation, hoisting laying pipelines and repairing.

5.1.4 Formula IOWA (see term 5.1.4 of this code) is recommended to be used to calculate pipeline distortion according to the steel pipeline radial stability of the subject report of this code 《Analysis and research on pipeline design value limit》(South West Petroleum Institute). Pipeline circle section instability collation shall be conducted where pipelines are buried deeper or the external load is bigger.

The △X calculated by formula IOWA shall not exceed 3% of the external diameter of pipeline. 5.1.5 Cold working can improve yielding intensity by 20%-30% no matter according to strain

rigidification phenomenon or deformation heat treatment theory and experiment. There is some difference according to different steel type.

The increase of yielding intensity value because of deformation will disappear gradually with the increase of the final backfire temperature. There will be a big mutual structure change at the temperature of about 300-320oC generally; while at the temperature of about 480-485oC, the intensified effect will disappear basically. The metal crystal grain displacement structure will encounter damage because the final backfire temperature is too high or heat preservation period is too long although the temperature is not very high (about 300 oC).

At the two temperatures and time conditions mentioned in this term, the pipeline of the minimum yielding intensity, which originally accord with the regulation, will lose strain intensity character, i.e. the yielding intensity will decrease by 20%-30%. It is reasonable for this code to regulate that the maximum pressure that the pipeline allows to bear cannot exceed the 75% of the value obtained from the formula (5.1.2).

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5.2 Materials 5.2.1 The selection of materials is very important while designing trunklines. There are plenty

of elements to consider selecting materials. Multi-aspect and comprehensive comparison shall be conducted. On the premise of satisfying the using conditions, safety reliability and economization shall be paid special attention to.

It is the flammable and explosive gas that trunkline transmit. Once accident happens, the result will be serious. While the trunkline is operating, mass elastic compressing energy is accumulated in trunkline. Once trunkline cracks, the crack of materials expands very quickly and cannot be stopped easily and the length of crack is quite big. Therefore, the steels adopted for steel pipelines and components shall have good anti-brittleness capability and good welding character in order to ensure the trunkline safety.

5.2.2 In order to ensure that the steel pipeline used for trunkline is advanced in technology and safe and reliable, this term regulates to adopt the steel pipeline produced according to the two standards of《Petroleum and natural gas industries--Steel pipe for pipelines--Technical delivery conditions》GB/T 9711 in China. This two standard is constituted by consulting America API Spec 5L standard. It is consistent with API Spec 5L on steel pipeline material’s mechanic character, chemical component, steel pipeline’s geometrical size, welding requirement, hydraulic pressure testing, undamaged crack detection and other technical requirements. The pipeline produced according to the above standard can economize the consumption of steels and ensure the operating safety.

In order to enlarge the scope of steels selection for trunkline, this code lists 《The weldless steel pipeline for transmitting liquid》(GB8163). Considering the transmitting pression of exist pipeline have achieved to 10 Mpa or above, the code for high pression weldless steel pipeline have issued.

5.2.4 Strike tenacity reflects materials’ plasticity deformation and energy absorbing capability while breaking process. It is the comprehensive reflection of material intensity and plasticity and the main guideline of anti-breaking and stopping breaking. Putting forward the guideline of controlling tenacity is the effective method of preventing pipeline brittleness damage. The economical and reasonable tenacity requirement is related with steel type’s intensity grade, pipeline diameter, wall thickness, welding method, using environment and temperature, etc. Designers shall make comprehensive analysis and judgment and put forward the testing project and guideline of controlling tenacity for the trunkline steels and pipeline auxiliaries materials in order to ensure pipeline safety.

In the condition of low temperature, metal material tenacity increases and brittleness decreases. Therefore, the trunkline and various facilities exposed to the ground temperature or the places of very low temperature shall be paid special attention to during designing. While selecting materials in these locations, its low temperature mechanics character shall be considered cautiously. At present, some countries in the world regulate that the low temperature confines is 0-30oC. In China the confines is 0-20 oC. Where the temperature is equal to or lower than such confines, the metal material low temperature tenacity shall be required. The value of anti-strike tenacity perform《Petroleum and natural gas industries--Steel pipe for pipelines--Technical delivery conditions》GB/T 9711.

5.2.5 The handling and testing of the harmful limitation on the steel pipeline surface 5.2.5.1 During transportation, installation and repairing, the pipeline wall thickness is reduced

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and the reduction shall not exceed 10%, i.e. the round-direction stress shall not exceed 10%. This limitation value is within the allowed range of pipeline wall thickness minus tolerance.

5.2.5.2 The partial damage caused during steel pipeline transportation, installation and repairing, like dent, slot and nick, etc, will become the source of craze and is the main reason of pipeline damage. Based on the opinion of rupture study, these limitations shall be prevented, got rid of and repaired. Sichuan trunkline exploded for many times, and besides the welding line quality problems, some craze sources were located at the places of nick and bump. This is the proof. Therefore strict regulations are made in order to ensure safe operating of pipelines.

Burnishing the “metallurgical nick” shall firstly burnish the electric arc burning mark and then smear 20% vitriolic amic liquor on the burnished surface. If there is any black point, burnish again.

5.3 Pipeline auxiliaries 5.3.1 Pipeline auxiliaries referred in this code are elbow, siphon, different diameter tie-in,

sealing head of pipe, pipeline flange, pipeline reflux, pigging device receiving and dispatching canister and its component. Pipeline auxiliaries have different geometrical shapes and the stress caused during using process is quite complicated and are the weak tache in trunkline structure. Therefore based on the whole trunkline structure, basic requirements shall be put forward about its material used, intensity, strictness, the capability to keep geometrical shape, producing quality and etc.

5.3.1.1 In order to endure the quality of forging material, the corresponding technical standard shall be abided by. Since the organization of cast steel material is not tight and equal enough, it shall be used as few as possible and shall observe the corresponding technical standard. The brittleness of cast iron is big and its organization is loose and it is not allowed to be used for trunkline.

5.3.1.2 At present China is constituting the standard for various pipeline auxiliaries by consulting the standard of some industrial developed countries. Some industries have constituted the standard on this aspect. In order to ensure the quality of pipeline auxiliaries selected, pipeline auxiliaries which are regulated to be selected shall accord with the active national and industrial standard.

5.3.1.4 Welding is the main connecting method in trunkline engineering. Therefore, the ninth chapter of this code regulates the welding process. But primarily the weldable character of welding material can ensure welding quality, except that has some direct relationship with welding process. This code regulates that the welding pipeline and pipe fitting shall be equal or similar to each other in material character, i.e. chemical components and mechanical character in order to supply basic guarantee for good welding quality of pipeline engineering.

5.3.1.5 If helix welding steel pipeline is used as siphon, the welding line cannot avoid the maximum round-direction stress district caused by siphons easily. If it is used at the location where bigger weariness load district may be caused, it is inappropriate obviously.

5.3.2 Where straight pipeline segment has no axis-direction restriction in trunkline system, because of liquid pressure effect and heat-expanding effect, certain force and moment can be caused on pipeline auxiliaries. Therefore in the design process the above pipeline auxiliaries shall be collated about the intensity according to the method regulated in Appendix E. The method listed in Appendix E is put forward by consulting the stipulation of America national standard ASME B31.8.

5.3.3 The distributing of the round-direction stress along siphon section, which is caused on elbow and siphon under the effect of liquid pressure, is very asymmetrical. SiChuan Petroleum

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Design Institute and East China Petroleum Institute recommend to use “round pipeline formula” to calculate the round-direction stress at each point of elbow and siphon according to theoretical deduction and experiments. The maximum round-direction stress caused is located at concaved point of elbow. This stress is bigger than the round-direction stress caused by straight pipeline. The increased multiple m is called as elbow or siphon’s stress increase quotiety under the effect of internal pressure, i.e. the increase quotiety of pipeline wall thickness of elbow or siphon to pipeline wall thickness of straight pipeline. This quotiety is the function of R/Do (the rate of curvature radius R of siphon or elbow to other external diameter Do). The bigger R/Do is, the smaller m is. Therefore curvature radius R shall be increased as many as possible. In the “round pipeline formula”, m=(4R-Do)/ (4R-2Do).

5.3.4 There are a lot of structure forms and producing methods of three-way pipe. The one listed in this term is the most basic and most commonly used one. With the continuous renovation of abroad and domestic producing methods, this code allows to adopt other three-way pipe and reinforcement method whose structure forms are reliable.

There are many ways to calculate the reinforcement design of the weakened part of opening a hole. At present the opening-hole reinforcement design calculation method in the concerned codes of many countries includes equal area method, limit analysis method, security theory and etc. The method regulated in Appendix F of this code is confirmed by consulting the reinforcement form of America national standard ASME B31.8 《Gas transmission and gas supply pipeline system》and by calculating the reinforcement using equal area method.

5.3.5 Pipelines are connected with taper by different diameter tie-in and will cause discontinuity of structure. This will definitely cause partial stress which is too great at the connection point. The bigger the cone angle of the different diameter tie-in is, the greater the partial stress is. From the aspect of liquid mechanics, the smaller the cone angle is, the smaller the liquid resistance is. Therefore the cone angle is expected to be small. Where the semi-cone angle is smaller than 15oC, the partial stress is smaller. But recent China code《Steeliness pressure container》GB 150 does not ignore the intensity for the different diameter tie-in whose semi-cone angle is smaller or equal to 15oC. So where the different diameter tie-in whose semi-cone angle is smaller or equal to 15oC, and its wall thickness and material is near to the steel pipeline which connected to large diameter terminal, the calculation of its intensity should according to《Steeliness pressure container》GB 150.

5.3.6 Sealing head of pipe for trunkline is seldom used. The structure form and calculation method regulated in the active national standard 《Steeliness pressure container》GB 150 can be used totally. Therefore this code recommends to design and calculate according to the above standard.

5.3.8 In order to ensure geometrical shape size, welding quality and the heat treatment at special situation satisfying the technical requirement, the combined piece like pipeline converging and pigging device receiving and dispatching canister, which are connected by steel pipeline, different diameter tie-in, three-way pipe (or opening hole partial reinforcement), sealing head of pipe and etc., shall be produced by factories which have the qualification of producing pressure containers because their structure is complicated, welding lines are more converged.

5.3.9. The fireproofing character shall be considered when using soft airproof structure at valves of some key positions in fireproofing district. The fireproofing character of valves mainly refers to in that where the soft airproof material is damaged by fire, this valve can still have good airproof character. The requirement of valve fireproofing character can be carried out according to

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the national active standard 《Current valve flange and welding connection steeliness ball valve》GB/T 12237 and by consulting the concerned requirement of American API 6FA 《Valve fireproofing testing code》.

6 Trunkline station

6.1 Setting principle of trunkline station 6.1.1 The setting of trunkline station shall firstly satisfy the requirement of gas transmission

process; secondly accord with the requirement of routes direction. The route direction referred here is the main direction of routes. Station position shall accord with the requirements of geography, geology, buildings, environment and flood controlling, etc., but the pipeline central line position may not accord with these requirements totally. In this kind of situation, the station position can be selected at the both sides of the central line if the main route direction is not influenced and the pipeline increase is not too much. In order to reduce the number of station fields, reduce management tache, and reduce cost of construction and management, all kinds of station field shall consider combined setting on the premise of satisfying the gas transmission process.

6.1.3 Trunkline station, especially compressor station, needs disassembling, assembling, hoisting and transportation because of big components maintenance; the driveway inside station shall be set in the pigging station during pigging task because vehicles need to transport pigging devices. For the station field which installs valve whose diameter is more than or equal to DN400, driveway inside station shall be set because the disassembling and maintenance of large-scale valves or hoisting need vehicles for transportation.

6.2 Pressure adjustment and measuring design 6.2.1 Trunkline station is set for the realization of gas transmission process. Therefore it needs

to carry out the special function according to the requirement of gas transmission process. The pressure adjustment and measuring process design inside trunkline station shall be consistent with gas transmission process, such as the requirements of pressure temperature, flux and changing working situation.

6.2.2 The setting regulation of pressure adjustment facility in trunkline station: in order to have stable operation, accurate measuring and safe operating of compressor in trunkline station, the gas admission pressure shall be controlled. In order to remain trunkline pressure and the comparative stability of flux, the transmitting pressure and volume of off-take station shall be controlled. In order to ensure the gas supply volume and pressure to users, pressure adjustment facility shall be set on each user pipeline in gas distribution station to adjust and control the pressure and flux. Adjustment facility not only adjusts pressure but also flux. Adjustment facility and measuring facility are set one by one, and flux adjustment can operate in the given range. Therefore adjustment facility is set before measuring facility. When adopt intellectualized electrical instrument with flux computer process technique, it can satisfy the site of pressure largely waved, if no more special demands, the pressure adjustment should be general done after flux meter measured. For the necessary of the pressure adjustment before flux meter measured, the design of the upright pipe segment before the measure instruments should meat with national current regulation.

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6.2.3 The setting regulation of trunkline station measuring facility: gas measuring on each pipeline and each gas source which go into trunkline station is the need of management and operation and at the same time the need of practicing economic accounting. Therefore measuring facility is required to be set. The off-take station gas-out gas and gas distribution station gas-out gas both belong to the gas for supply or sale. Therefore measuring facility needs to be set to measure gas. Measuring facility shall be set for self-consuming gas in trunkline station for the need of management and business accounting.

6.3 Pigging design 6.3.1 The interval between pigging facilities is generally above 100km. The pigging facilities

in foreign countries are mostly set in the compressor station or other station fields. 6.3.2 China trunkline pigging process develops from open pigging to gas non-stop obturation

pigging. By this means, gas is avoided to be relieved on a large scale and it is beneficial for environment protection. Therefore this code regulates to adopt gas non-stop obturation pigging process.

6.3.3 The purpose of gigging out of station go through the indicator is to carry out semi-automatic the pigging operation, so whether let the gigging out of station go through the indicator and transferring the indicating signal to station, wholly depend on the pigging method confirmed by process design.

6.3.5 When set the pigging facilities at where high human density or in factory, if limited by placement lead to cannot satisfy the safe interval regulated at this regulation, we can set a block wall at the appropriate position behind the pigging receiving axes to assure the safety.

6.4 Disposal of compressor set and design principle of workshop

6.4.1 Compressor set can be disposed in all-close-in, semi-open, open buildings or in the open air according to materials and producing practice.

All-close-in building: there are walls and windows and doors around. Semi-open building: there are half walls around. Open building: there are only roofs. The facility adopting setting in the open air shall be able to adapt to the requirement of

environment. Enclosed workshop construction is generally used for cold climate and large sand blown by

wind area, it can well protect the compressor unit, with good condition for the maintenance and inspection repairing. Where adopt the enclosed workshop, good ventilation facility should be used; the peripheral construction of the workshop should use the light material with decompression for roof, outer wall, door and windows, to assure enough decompression area. The decompression area should layout reasonably, and close to the possible exploration section as possible, should not face the site with centralized human and main traffic road.

6.4.4 This term is for that once there is accident happened, the on-the-spot staff can withdraw quickly. The content is constituted according to term 3.5.3 of 《Construction design fireproofing code》(GB16-87) in China and by consulting term 843.13 of America national standard ASME B31.8.

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6.4.6 The space inside the compressor workshop should be reasonably structured, except the and pipelines set by the demand of the process production, in order to the installation and inspection and repairing, enclosed and half enclosed compressor workshop should equipped with hoist correlate to the tonnage according to the requirement of compressor units inspection and repairing and installation; should reasonably layout the position for lifting span and inspection and repairing within the workshop according to the requirement of the installation and inspection and repairing, and the construction character; for combustion turbine when attached the hoist with itself, it is unnecessary to set fix hoist equipment; the compressor unit when set at open air, open workshop, generally it would not equip with the hoist; the installation and inspection and repairing of compressor all adopt auto crane or caterpillar crane, etc crane, the working interval for crane should be remained.

6.5 Compressor station process and the assisted system 6.5.1 The gas into the compressor set shall be got rid of solid impurity and coagulated liquid in

order to avoid damaging compressor set. This code does not put forward limit value of dust content and dust diameter of dust included because of no practical experience data and no reliable inspecting measures for dust included. According to the introduction of literature: the former Soviet Union scholar ever conducted abrasion experiments and research on supercharger of model 280-11-1.The size of the dust (calcium carbide, quartz) in the gas is 5-600um. It was discovered that the biggest abrasion intensity happens in the condition of dust diameter of 75um. With the increase of dust diameter, the abrasion is reduced a little instead. In condition of dust diameter of 10um, abrasion is almost reduced to 1/3 of the maximum value and in condition of below 5um, abrasion is so small that can be ignored. Where dust diameter exceeds 10-20um and dust content is above 1mg/m3, radial compressor cannot ensure the reliable work of 50000-60000h because of the abrasion of lamina. If according to the materials introduced in this literature, the dust diameter of dust included in the gas into compressor might be limited to 5um. In order to clean the residue in the natural gas at the inlet sector of the compressor, limit the dust diameter of dust included in the gas to less than 5um, base on the pipeline natural gas quality level, the abruption equipment must adopt grade one or grade two. 《Design code for QuanSu trunkline pipeline process》part 1 “Natural gas pipeline” regulate: dust cleaning for natural gas general adopt grade one; for the compression station after average go through 3~5 compression stations, dust cleaning for this natural gas general adopt grade two. During the construction of Chinese ShanXi to BeiJing compression station, base on the actual condition of too much dusty during the pipeline operation, the inlet sector of the compressor has adopted grade two abruption equipment.

6.5.2 Gas pressure is improved through compressor station by consuming power. Where pressure losing of the gas flowing in pipelines and facilities is too much, the power consumed will be more. Where pressure losing is regulated too few, pipeline diameter will be enlarged. Therefore an economical and reasonable limit value shall be set. The limit value regulated in this term is confirmed by the experience of ShanXi to BeiJing pipeline pressing gas station, the explanation of this term list out below abroad data for reference:

(1) One article of America 《How to select appropriate radial compressor used for trunkline》introduces that pressure reduction of entrance and exit pipelines of compressor is respectively 5Psi (34.53kPa). This pressure reduction has included the pressure reduction of the facilities of the pipeline segment.

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(2) Japan Qiandaitian Corporation regulates that the entrance pipeline pressure reduction of compressors of economical pipeline diameter is 0.069kg/cm2*100m, and compressor exit pipeline is 11.5kPa.100m (“engineering technical materials introduced by Wolong river decontamination factory ”).

(3) Esso standard (3) regulates that, the entrance pipeline pressure reduction of compressors whose pipeline diameter is confirmed according to economical requirement is 0.1 pound/inch2.100feet (0.689kPa.100m), and compressor exit pipeline pressure reduction is 0.2 pound/inch2.100feet (1.379kPa.100m).

(4) 《Germany city coal gas transmitting and distributing manual》regulates that pipeline diameter is selected according to that the total pressure losing of compressor entrance and exit pipelines (include the facility on the pipeline segment) is not more than 1 bar (100kPa).

(5) 《Design code for QuanSu trunkline pipeline process》part 1 “Natural gas pipeline” regulate, the pipeline pressure lost in compressor station can not excess the value at table 6.

Gas press lost internal of the pipeline of compressor station (Mpa) Table 6 Pressure lost

Total Amond Compressor inlet

Pressure at gas pipeline

(meter pressure)

Natural gas class 1 apart

Natural gas class 2 apart Natural gas

class 1 apart Natural gas class 2 apart

Compressor outlet

5.4 0.15 0.2 0.08 0.13 0.07 7.35 0.23 0.3 0.12 0.19 0.11 9.81 0.26 0.34 0.13 0.21 0.13 6.5.3 This term is issued refer to Britain and Europe standard 《Natural gas supplied

system—compressor station functional requirement》SB EN12583-2000 and cosmetic experience. The cool proofing layer outside the pipeline, pipeline bury environment such as cropper, permafrozen ground, etc, have different requirement for the pipeline temperature; reduce the transmitting gas temperature can increase the transmitting efficiency; during compressor station design abroad, after the technical and economic comparison, there is the case that only cooling surge proofing the cycle air, but not cooling the outside transmitting gas. So, this term does not special quantificationally regulate the outlet temperature of compressor, but can be confirmed by designer according to the actual engineering condition.

6.5.6 The oil system of centrifugal compressor 6.5.6.1 Along with the progress of compressor designing and manufacturing technique,

centrifugal compressor has been widely applied to dry air hermetic system instead of traditional oil hermetic system.

6.5.6.2 In the set startup process and after shutdown, lubrication oil and airproofing oil need to be supplied. At this time, the set is not operating normally. Motor power cannot drive oil pump to supply oil. Therefore assisted oil pump shall be set. This term recommends that its power may adopt compressed airmotor to drive oil pump. This facility has the advantages like simple structure, reliable working, and can obtain gas of sufficient pressure and flux to be the actuation airflow. It has been widely adopted in foreign countries and the technology is mature.

6.5.8 Cooling system. 6.5.8.1 Adopting air cooling device can reduce or cancel circulation water system and simplify

the cooling facility in its wake, and it is especially reasonable in the district where water supply is not convenient.

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6.6 Compressor set model 6.6.2 Compressor station is an important component of trunkline system. The investment of

compressor station accounts for bigger proportion of the total investment of trunklines. Compressor set accounts for bigger proportion of the total investment of the station. The annual running cost of compressor station accounts for bigger proportion of the total annual running cost of trunklines. Therefore selecting economical, reasonable, endurable and reliable compressor set is of great significance for reducing investment and gas transmission cost.

At present the available set mainly includes radial compressor and reciprocating compressor. The main advantages and disadvantages are as follows after comparison:

(1) Radial compressor: Main advantages: big eduction volume, more proportional flux (without impulse phenomenon),

lighter machine body, and simpler structure. Main disadvantages: easy to cause breathing vibration, and lower single level pressure

(2) Reciprocating compressor: Main advantages: higher efficiency, bigger range of adapting to gas admission pressure

changes, and no breathing vibration phenomenon. Main disadvantages: machine body is heavier, more complicated structure, bigger vibration,

and disproportional flux (with impulse phenomenon). In conclusion, the trunkline with more gas transmission volume and fewer changes in pressure

should adopt radial compressor. At special situation, for instance, the initial station of trunkline (is the last station of gas colleting of gas field and the gas admission pressure is influenced by gas field and might have bigger changes) and the station which has gas inputting halfway (for instance the gas admission pressure of the station which has gas inputting from gas field on trunkline halfway, might be influenced by gas supply pressure of gas field), have bigger changes in pressure or fewer gas transmission volume and they can select reciprocating piston compressor.

6.6.4 Along with the development of electrical technique and the improvement of power supply, there are many success cases to apply centrifugal compressor unit droved by large power Variable Frequency Motor to long distance natural gas transmitting pipeline, and take on upward trend; due to the advantage of electrical motor at the investment, efficiency, environment protection, operational maintenance, service life, so where the power can well be supplied and can save the synthetical cost, the drive facility for compressor station should consider to choose the Variable Frequency and Speed Adjustable Motor.

6.6.5 This term is issued refer to Britain and Europe standard 《Natural gas supplied system—compressor station functional requirement》SB EN12583-2000 and cosmetic experience. The actual on site power output of combustion turbine and combustion motor is closely related to the height value and environment temperature, after confirmed the station address, the height value is fixed, but the environment temperature is variable according to the season. The output of the combustion turbine and combustion motor have large different under different season with different environment temperature, in order to let the actual output power of driving equipments meet with the compressor’s power requirement, the designed environment temperature of driving equipment must be reasonably confirmed. The output of combustion turbine at ShanXi to BeiJing compressor station is confirmed with the local monthly maximum average temperature.

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6.7 Compressor set safety protection 6.7.2 The safety protection facility regulated in this term shall be provided to form a complete set by compressor set (refers to compressor, motor power and the assisted machines of them) producing factory. The technical requirement of compressor shall be confirmed according to the regulations of this code while ordering goods. 6.7.3 This term is issued refer to Britain and Europe standard 《 Natural gas supplied system—compressor station functional requirement》SB EN12583-2000.

6.8 Pipelines inside stations 6.8.2 To prevent the erosion of pipeline inner wall from polluting the transmitted medium inside the pipeline, then possibly damage the instrument and the compressor set, this term regulate: the pipeline for the hermetic gas used at the instrument in station and set, controlling, sampling, lubricating oil, centrifugal compressor, and the fuel gas for used at combustion turbine should adopt stainless steel pipe and pipeline component. 6.8.4 The normal operation of the centrifugal compressor set have strict requirement for the set installation and center symmetry. The stress to compressor connect flange generated by the centrifugal compressor inlet and outlet fit pipeline should be less than compressor allowed value, so as to prevent the compressor from abnormal operation and being damaged by installation press excess the maximum allowed value. The allowed withstand stress value of the compressor have regulated at API 617, but during products ordering, the user can have special requirement according to their demands. 6.8.6 Where pipelines are laid in pipeline dykes, safety might be influenced if flammable gas accumulates in the dyke because of leaking. Therefore this term regulates that pipelines in station should not adopt laying in dykes. If caused by the installation, it is necessary to lay in dykes of the pipeline for some sections, the measure should be adopted to avoid the gathering of flammable gas.

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7. GROUND EQUIPMENT FOR UNDERGROUND GAS STORAGE

7.1 General 7.1.1 Underground gas storage is a general measure for seasonal peak regulating gas volume, daily peak regulating gas volume or emergency gas reserves at large and middle size city, should investigate the different type fuel gas users in the city, to confirm the working index of different users, calculate the required peak regulating gas volume, where the underground gas storage is used as incident peak regulating, the constructor should provide the incident gas reserves volume under the trunkline incident. 7.1.3 Underground gas storage should close to the load center or long distance pipeline, this can reduce the pipeline construction cost, reduce the pressure difference along the pipeline, at aboard, it is not more than 150 km. 7.1.4 The collecting gas station and injection station at aboard is generally combine constructed to reduce the public system investment. 7.2 Ground process 7.2.1 Gas injection process 7.2.1.1 Inside the natural gas pipeline, it is unavoidable to exist the dust residues during the its transportation, construction, it is impossible to cleanly removed by pipe pigging, the dusty in natural gas is the main factor affect the compressor operation cycle, base on the reciprocating compressor character and current cosmetic filter manufacturing level, the dusty in natural gas at the inlet pipeline of compressor shall be less than 1ppm (grain diameter should less than 2um). Most compressors exist lube oil, in order to separate lube oil exist natural gas between grades and protect the compressor, the inlet of every grade should equipped with liquid separate facility. 7.2.1.2 According to the investigation, at the outlet of the aboard injection compressor, every 1000m3 natural gas have a content of 0.4~0.5g lube oil after pigging, our country DaZhangTuo underground gas storage has a content of 5ppm (weight) finally, Ban 876 underground gas storage has a content less than 1ppm(weight), this value is defined by geologic research institute according to the geological type of underground gas storage. 7.2.1.3 Calculate every single well’s gas inject value, so as to convenient the geologic monitor and measurement, data simulated research to deep the knowledge of the geologic. 7.2.1.4 Due to the higher pressure in injection pipeline, generally more than 10MPa, for safety purpose, it should be equipped with block valves for High Pressure and Low Pressure at outlet of station. 7.2.2 Gas production process 7.2.2.1 It is important to monitor the water content of underground gas storage during underground gas storage operation, the water and light hydrocarbon should be calculated and monitored separately.7.2.2.3 According to the geologic operation program, the component and pressure of the produced gas, select the cooling process, including: throttling cooling, coolant cooling or expansion cooling. 7.2.2.4 For the device that use throttling process to control the water dew point and hydrocarbon

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dew point, pressure regulation throttling device is the most important equipment, it should have backup. The fluctuation of peak adjustment of gas storage center is big; therefore it is important to control the noise of regulating valve. 7.2.2.5 When the injection well/production well and gathering station are close to each other, it is recommended to adopt combination method of injection/production in order to reduce the project investment.

7.3 Selection of equipment 7.3.1 The selection of compressor. 7.3.1.2 According to the working condition of Underground gas storage in domestic and international market, the pressure of underground storage center shall be changed according to the capacity of storage center. Reciprocating compressor can meet this wide range of pressure change more effectively. 7.3.1.3 In oversea market, the selection of gas injection compressor can work properly in gas injection phase as well in gas production phase. In USA, Blue lake natural gas Underground gas storage is situated in Michigan State, about 250 miles to the southwest of Detroit; Blue water-18A gas storage center is mainly used for seasonal peak regulation, with the working gas volume 46bcf, starting point is 7.5bcf, daily process volume is 690MMscfd, it is one of the biggest gas storage centers in USA. Blue lake-18A compressor station has 3 Dresser-Rand6000hp integral gas driven injection compressors. 6 juxtaposed compressor cylinders are operated by single step, with the outlet pressure 1400psig; when used in series, each step has 3 cylinders, outlet pressure can be as high as 4200psig. The main function of the compressor set is for gas injection. When the pressure of produced well drops, natural gas after purification can not enter local gas distribution network, the natural gas can be pressurized before export. The compressor set can be operated by single compressor during the operation cycle of gas storage center, which is also can be run in juxtaposition or in series. Gas injection compressor can be operated in gas production phase, which can keep the wellhead pressure during gas production phase to as low as possible, enlarging the working pressure range of underground gas center, increasing peak regulation gas volume and increase the use rate of gas injection compressor. 7.3.2 Selection of air cooler 7.3.3 Wind induced air cooler has the advantage of fast wind speed at the hot wind outlet of

cooler, it is very useful in improving the temperature site and hot circulation among many compressor air coolers and reduce the intervals of air coolers and the space.

8 Monitor and System Control

8.1 General Regulations 8.1.1 In order to ensure the safety of gas transmission pipeline system and stable transmission, necessary metering, monitoring and control system shall be built on process equipments and facilities on site of stations. This is to ensure that the operation parameter and the real-time status of pipeline transmission and distribution system conform to set requirements.

The monitor, control and data collection system (hereafter referred to as SCADA) mentioned in

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this Chapter is an automatic control system which is based on electronic computer and make up of advanced communication technology and remote terminal device of intelligentized functions.

In the past 10 years, thanks to the rapid development of computer and communication technology, pipeline control management has entered into a brand new era of automatic management. In the early 1960s and 1970s, the aim of automatic management was to reduce personnel of managerial level so as to reduce cost for management. From the mid 1970s to 1980s, automatic management combined electronic computer and economic mathematics methods, in an attempt to improve pipeline transmission, and reduce energy consumption and operation and management expenses. Take American Pacific Natural Gas Transmission Co Ltd for instance. APNTCL managed a gas transmission pipeline of 1150km. By adopting SCADA with electronic computer as its system basis, its pipeline could work under optimized condition, and thus saving 8% of total fuel. In addition, SCADA could predict the optimized operation methods in a few minutes, and thus evaluate the efficiency and benefit of newly adopted equipments. At the present time, SCADA is more and more applied to oil and natural gas long transmission pipeline systems by companies all over the world. This is based on good reasons:

(1) Increasing transmission quantum and reducing managerial personnel brings obvious benefit.

(2) Improve management level, provide timely regulating countermeasure, ad ensure safe and stable gas transmission.

(3) Keep collecting and accumulating experience, and create condition to optimize management.

In China, the application of SCADA to long transmission pipeline is still in cradle phase. Dong Huang Oil Transmission project introduced the first testing SCADA system in its reconstruction of multi track works (Total Length is 247km, and 5 stations). During our country’s “Ninth Five” plan Shan-Jing gas transmission pipeline project introduced aboard advanced gas transmission pipeline project system SCADA. Compared with aboard, our country’s construction of this type of project still at the underway stage, but the development is rapid.

Gas transmission Pipeline construction of China’s gas transmission system was started from the early years of 1960s, and slowly expanded year by year. Therefore, the equipments and outfit for each station varies quite much, which objectively brings considerable difficulties to the reconstruction and improvement of the system. With the development of China’s Four Modernizations of Agriculture, Industry, National Defense, and Science and Technology, natural gas industry is bound to have a bigger and brighter future. Especially in the oil and natural gas exploration and development of West China and inshore area, the construction of large-scale gas transmission Gas transmission Pipeline has come to the phase of planning and designing, and is now ready for execution. Due to the fact that these long distance large-scale trucnkline are located with bad natural conditions and with very complicated system, present control and management standard is a far cry from meeting the needs. Therefore, the application of SCADA system technology is imperative under the situation.

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It should be pointed out that whether to adopt the control and data collection system depends on environmental condition, managerial system, and the how complex the Gas transmission Pipeline process is, etc, and is eventually decided by economic benefit. As different situations can not be treated as the same, the standard language here is “suggested / recommended”. Emphasized the requirement that the complex system pipeline project should adopt the equipment and technique based on the computer, and centralized monitor and scatter controlling to the system to more definitude the requirements. According to the current more than 10 years’ experiences of our country’s pipeline project, for the system complex long distance transmitting gas project, it is necessary to carry out systemic SCADA, and have got the succeed experiences and have possessed the impersonal condition for the construction.

8.1.2 This term have detail explained the monitor and data gathering system set at item 8.1.1, its content include two parts: first part define the composition of the monitor and data gathering system. Due to the rapid development of electrical computer ant network technique, considering the pipeline project have been basically constructed and the requirement at future development, automatic system should have high reliability, and at the same time it should possess well adaptability. So, the supplied system is required to be open type network framework, which should have good universality, compatibility, extensibility. The construction of the system should consider the hardware and software supporting as possible as development of technique, but not been limited or less been limited by system suppliers. 8.1.3 Model selection for instrument and control system shall firstly accord to the demands of process (e.g. range change, the stability of process parameter, precision requirements, medium condition, centralized operation degree, response speed, etc.), and then is decided by many important factors such as economicalness, reliability, safety, maintenance transportation distance etc. In the same gas transmission pipeline system project, the category and specifications of control equipments and instruments shall keep as consistent as possible. This is because:

(1) Convenient for unified management and maintenance, thus improve maintenance standard.

(2) Convenient for unified training of personnel, thus reduce the outfit for auxiliary facilities. (3) Convenient for procurement and supple of spare parts, thus reduce cost, and improve

maintenance capability. 8.14 This item emphasizes on the requirement of dependability and practicability for monitoring and data colleting system. This requirement is fundamental, and also is very important for long distance gas transmission pipeline. To provide hot back-up to the instruments and control equipment at the places where are easy to occur accidents is an important measure to improve system’s dependability and practicability.

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Spare outfit is suggested to be prepared for the instruments and control facility that is liable to failure. Ordinary instrument and control system shall consider self-protection measures upon failure. For example, spare loop, alarm upon failure, chain protection upon failure etc. In addition to the spare outfit, according to the requirement of production operation, for instrument power and gas supply system or any part under failure condition, spare outfit hereby indicated shall also aim at the centralized monitor and control facility in the centralized control center, such as electronic computer or programmable controller etc. Online hot spare backup or redundancy spare backup can be applied in accordance with its importance. Whether the redundancy spare backup is undisturbed automatic switch over or manual operation is not specifically regulated. It can be decided by design personnel according to real time situation.

8.1.5 The selection of control plan shall be in favor of economizing on energy, which is especially meaningful to lone transmission pipeline. The reason is that many stations are situated in remote areas, and not convenient for power supply. To establish special power supply facility is very non economical. Therefore, from the angle of energy saving, it’s best to adopt a control plan that is beneficial to reduce energy consumption. Under the condition of ensuring precision requirements, it’s better to adopt instrument with low-pressure loss. In particular, energy-saving flow measuring device, e.g. compressor’s flow metering, is better not to use throttle device. On the other hand, as the system can make full use of the pressure energy of gas, if safety permits, the control gas supply for instrument shall give priority to utilize the pressure energy of Gas transmission Pipeline gas. As gas supply for instrument, it’s preconditioned that gas quality shall meet all the related requirements. 8.2 System Control Management 8.2.1 Basic requirements for monitor, control and data collection system: gas transmission pipeline’s SCADA system is composed of 3 parts the MTU of gas transmission control center located somewhere along the pipeline, remote terminal utility (RTU) of controlled station, and data transmission channel. Under common circumstances, there’s only one gas transmission control center, while there could be as many as 10 RTUs. The structural principle and control target of this system is as follows: 8.2.1.1 To efficiently expand the control and handling capacity of the system, especially the system with insufficient gas storage control capacity, it’s best to increase the proportion of brought-in gas transmission quantum that the system can control and manage. However, due to the restriction from geographic location and data transmission channel, normal brought-in controlled gas can’t reach 100% of the system. According to statistics, the normal ratio is over 80%. Take Qun-Shen pipeline design for instance. The brought- in gas takes up about 96%. The design of system structure shall make allowance of extra room for future development and expansion. This extra room is set for the future addition of controlled stations. According to statistics, the allowed room takes up about 20%. 8.2.1.2 Computer system shall have excellent real time response capability. The system, upon the receipt of information or data, is able to start processing with a sufficiently fast speed, and the processed results are able to execute a timely control over the monitored target or the controlled

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course. In the course of information processing and controlling, if several interruptions happen at the same time, computer system is able to judge interruption level, and thus make immediate response and processing to the one with highest priority, so as to ensure the liability and improve the performance of the system. In addition, the operation system software installed in computer system shall be abundant, consummate, practical, and can provide the user with timely analysis and decision report in order to exert its control function. 8.2.1.3 For the purpose of simple operation and use, computer control system shall provide intuitive and flexible man-machine dialogue facility. At present stage, many man-machine dialogue facilities on the control table have already been in extensive use, such as keyboard, controlled printer, light pen, Monitor (CRT), and operation menu prompt through software and so on. Furthermore, self diagnose program shall be equipped in order for timely maintenance. 8.2.1.4 Strong communication capability, On the condition to ensure transmission quality, it is required that SCADA can increase the exploitation rate for transmission pipelines, and provide an information exchange system with high quality, high speed and high efficiency. In addition, SCADA system shall bear excellent extension capability, and can connect network with higher-level systems or exterior systems for network control and coordination. 8.2.2 The setting of control center shall take the following points into consideration: 8.2.2.1 Control center, also called system control center, is the chief hinge of SCADA, and shall be built in regions where control, management and communication are convenient. In general, control center is in the neighborhood of big or medium sized cities. 8.2.2.2 Control center shall set up system general control room. In the general control room, there shall be host computer system control chamber, For the current case without relative code requirement, it is suit for design to conform to the Government standing standards – “The Technical Requirements for Computer Station Venue” GB 50174. It’s highly recommended to provide as a good running operation environment and condition as possible. It should also be noted: host computer chamber and exterior disk storage spot have higher requirements than control room and terminal room do. In particular, temperature, comparative humidity, sanitation degree, and temperature change rate etc, shall go through special treatment. 8.2.2.3 This item has further described to use twin-machine hot back-up system. For the computer system on importance occasions, except it is necessary to use twin-machine hot back-up, its main interface of operation will also need to use hot back-up, so as to ensure the dependability and practicability of system running.

In order to ensure SCADA system in working order, the host computer system in the control center shall be highly reliable. It must not happen that the failure of computer system negatively affects the operation of the whole system. Therefore:

(1) Host computer in control center general adopts twin computer operation system, with the two computers heat backup each other. When one computer is running, the other is in monitor status. Normally, the backup computer of twin computer system is setup as a

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complete single computer system. For example: each computer shall have its independent central process unit (CPU), RAM, communication controller, communication interface, operation calculator, local network interface, communication high-way interface between host computers, hard disk, tape driver, monitor, key board, etc.

(2) The terminal equipments of control center are mainly composed of color CRT, keyboard, and printer, which are placed on control center’s control operation table, and used for man-machine dialogue by controlling personnel while monitoring. On ordinary operation table, there are 3 color CRTs, which are respectively used for the display of pipeline operation status, the monitor of alarm, and display of tendency. In addition, there are 3 operation keyboards and 3 printers, used for the printing of pipeline system operation parameter, the printing of alarm and control instructions, and the printing of reports respectively.

(3) The man-machine interface in dispatch control room shall be high dependable and practical. Generally it can use hot back-up method for allocation. Each equipment shall have complete function. Under normal situation, the equipment with man-machine interface shall be one in the status of watching, one in the status of hot stand-by; or also can be one in the status of watching, one in the status of supervision and control. If one interface of them has any fault, another one can replace it to undertake all work.

(4) For general large and middle sized dispatch control center, because the supervised network system is relatively complicated, for the purpose to make the operation more flexible and to increase the parameters and objects of such supervision and control, let the operators to control the whole situation more systematically and completely, generally the terminal display of “one machine, multi display” style is adopted. This kind of allocation is widely used abroad in the same projects, which is no doubt an effective method of good applicability and dependability provided for the system.

8.2.2.4. This item is a supplement for the original specification. From the need of dispatch management, the dispatch control room shall provide flexible and multiple access to the operators. Generally, it is basic requirement and necessary to carry out periodical scan to each controlled station, but according to the needs of dispatch management, for the purpose to command the relevant parameters and status of these controlled stations timely and effectively, it is necessary to provide several kinds of access for selection. Except that of continuous periodical scan, according to the system’s requirement, it is necessary to carry out fixed time scan, priority scan, on-request scan, and confidence scan. The Primary function requirements of control management system:

(1) According to preset scan period, scan every controlled station continuously and in order, and monitor the operation status of all stations in the system. Generally, SCADA system doesn’t monitor controlled station by way of the running of “Abnormity Report”. Instead, SCADA will scan each station in order, make query, and collect real time operation parameter from each station. The trait of this continuous scanning method is that SCADA can receive practical analog value while scanning. If RTU adopt “Abnormity Report” operation mode, then there must be a certain analog difference change between the preset value and the actual metering value. Although system is in monitoring status, and scan

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period can be shortened, it still can not confirmative reflect the real time and actual operation analog value, and will only submit abnormity report while exceeding the regulated spectrum. Therefore, the SCADA system of gas transmission pipeline system normally adopts ordinal scan mode. The main function of SCADA system is: to execute ordinal communication among control center and each controlled stations; to take control of the main running technical parameter and status of each controlled station; to display real time parameter, status and results; to make abnormity report on operation parameter and status; to print or record the operation result. In addition, SCADA shall master the integrated parameter of the running of pipeline system such as: system pressure distribution and change, flow volume distribution status, the operation condition of system’s main technical equipments and so on.

(2) SCADA system control center shall also have the function to send control command and regulating command to controlled station’s the remote terminal unit. These commands are sent through the station first level centralized control system. According to present reports collected from overseas, these commands, as is to controlled station, are only minority pivotal parameter; for example, change the exit pressure preset value of gas compressor station, start / stop burner/compressor machine units etc. Whereas, the direct remote control mode is not yet applied extensively; for example, change the exit regulating pressure of pressure meter station etc.

(3) Control center shall also have the capability to make relative data analysis, and provide instructions on controlling personnel’s decision and order making, so that the controlling personnel can execute timely and effective control and management over pipeline system.

Along with the rapid progress and perfection of computer network technology and applicable software, at present SCADA system is not more the single function of supervision and control like it was before, but has achieved the great development on network management and control system, whose target is to realize systematic scientific management and optimization. 8.2.2.5 Control room host computer system shall be equipped with plenty and practical software. Software shall be installed in accordance with the development of the system. In the starting phase of the system, only basic software is needed. With the accumulation of operation and application experience, the software system can be gradually improved, especially the adding of application software. To name the software to be installed are:

(1) Operation System Software: This type of software, normally provided and installed by computer manufacturer, is very important to the application of SCADA system. In order to accomplish the complex tasks of host computer system, a program, which is large in scale, can coordinate and control all utilities, and can support many application programs to run in high efficiency, must be specially written. This program is expected to exert its chief command and controller function in the whole computer system, so that all the utilities and programs in the computer system can complete their missions on time under its uniform arrangement. In general it shall have the following functions:

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Administer Central Process Unit (CPU) Administer memory (RAM) Administer exterior (peripheral) utilities Administer documents (program and data) Ordinary operation system software includes: Computer system’s real time, multi-functional monitor and management software Support Fortran language calculation Practical program software to maintain and amend software system System security protection software System resource management and analysis software Main CPU network software System generation software Etc

(2) SCADA System Software: SCADA system software, also called control software during control procedure, is normally installed in accordance with the requirements for system function. It is specially provided by SCADA system vender. For example, American SSI Company can provide full set of SCADA system software for long transmission pipeline. SCADA system software is specially designed to realize its control function, and used by controlling personnel during monitoring and controlling the running of pipeline system. It includes the following software:

Remote Terminal Unit (RTU) Communication Control Software (Data collection, control and output) Display Control Software. To finish the display of RTU status, the display of alarm status, the display of analogue and data signal, the display of dynamic tendency and historical curve; to instruct decision making, and to generate software by reports, etc.

(3) Pipeline System Application Software: Application software is a program written by user in order to solve a certain type of problem by using computer and its system software. With the development of computer application and the accumulation of operation experience, pipeline system application software has gradually become standardized and modularized. In foreign countries, this type of program is normally made into software packs, and sold by expert software companies as merchandise. As there are variety kinds of software, it shall be installed according to basic needs. Some companies have to make research and development of certain software by its own to satisfy its special needs. Pipeline system application software general includes:

The display of pipeline system compressor station and machine unit operation The balanced calculation of pipeline system’s flow volume Pipeline gas storage analysis Leak inspection Instruction on operation control and decision-making

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Management of business plan Etc

8.3 Controlled Station 8.3.1 Along with the development of our country’s computer industry and instrument/meter industry, and the improvement of equipment’s dependability, as well as the accumulation of operation experience, it has created a favorable condition for the integrated control and management of our gas transmission trunks and stations. For the purpose to command the working status of the whole system timely, and make prompt decision base on various information. At present, we have complete capability to adopt industrial PLC to control the station, collect mass messages from the field and send them to control room through data channel, then carry out supervision, display, printing, and processing according to the collected data by the way of CRT. Through man-machine dialogue or auto control method in control room, give relevant orders to the control units at the field, by scattered control loops to finish the whole control function. This type of control has avoided the possible danger of that, in case in the highly concentrated computer system, if a computer is in failure, if would affect the normal operation of all control loops. It shows the advantage of “distributed danger” principle, greatly improves the dependability and auto-control level in the stations. At present in abroad, this kind of stations can completely realize capability of “unmanned control”, which only needs some personnel for watch work.

For long distance gas transmission pipeline, along the routes of pipeline there are a great number of remote control valve chambers and cathodic protection stations. Because of that most of these facilities are located at remote places, the nature condition is bad, they need unmanned management, so their dependability must be high. Along with the rapid development of electronic computer technology, the PLC with micro processor can have very mature signal processing function, has been widely used in gas distribution and long distant gas transmission both domestically and internationally, and it has been approved in the application of Shan-Jing project during our country’s “Ninth Five” plan.

Due to the importance of station control system within the whole system running, and that of the difficulties of system maintenance because of various elements, the equipment used in the station control system must be highly dependable, the key units also need heat redundance setting. The applications by the projects in our country and abroad have shown that the station control system shall use industrial micro computer and PLC unit. For general unmanned small size stations including remote valve chambers and cathodic protection stations can use RTU/PLC. 8.3.2 Basic Function of Controlled Station. Controlled station included in SCADA system shall send its main operation parameter and status to control center in accordance with system control and management requirements, and receive regulating and controlling command from control center. For control and management, the parameter of controlled station to be known is limited. On one hand, it’s restricted by the capacity of transmission channel. It’s impossible and no need to send all station information to control center. On the other hand, the purpose is to comply with the principle of “dispersive control, dispersive risk. Each station handles the operation of system independently, and is responsible for its own reliability. At present the SCADA management of long transmission

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system in foreign countries also place great importance on the centralized and united monitor over station’s main parameter. It just sends few control or regulation commands, and the station system executes the detailed control and regulation task. This is because the transmission channel is huge in dimension and very long in extent, and malfunction is almost inevitable. Dispersive control is able to make each station to be responsible for its own function, and thus avoid risk getting too concentrated. The control management level of controlled stations stipulated in this Criterion is based on the following principle: If gas compressor station is watched by people on duty, the pressure regulation meter station is not. To meet control management requirements, to ensure staff on duty can, if necessary, intentionally intervene the operation parameter of station in the station control room and make intentional contact with control center, and for the convenience of manual or automatic control over station operation, operation control table shall be set up, and control and monitor utility for man-machine dialogue shall be installed. As a result, station can have monitor and control function of higher level, and can create favorable conditions for its system to develop into control center’s remote automatic operation. The basic functions for controlled station stipulated in this Criterion apply to more complicated long distance gas transmission pipeline systems to be built in future. For ordinary, comparatively simple gas transmission pipeline system, the basic functions of controlled station can be simplified. 8.3.3 The design principle stipulated in this Criterion is based on station control. The following situation is taken into consideration. In the event that the channel or control center host computer of the pipeline SCADA system is malfunctioned, controlled station itself has self-contained monitor and control capability, and can maintain the normal operation of the station. Or when a certain loop of the station is malfunctioned, it will not affect the normal operation of other systems.

Therefore, the control utilities of gas transmission station generally shall have three control and operational functions, namely function for station centralized control, which is the function to operate upon receipt of the control signal sent by control room; function for on-the-spot automatic operation, which is the function to automatically start operation by manually pressing function key on the spot; and the function for manual operation and control. Whether utilities in the station shall be furnished with the three operational control functions at the same time shall depend on practical situation. For example, the control of heating utility only needs to monitor the heating temperature and the procedure of fire extinguishments, protection and intake into control room, while control task is accomplished by an on-spot control system. For another instance, the manual startup in the startup/stop procedure of burner compressor machine unit is the �auxiliary device to assist operator to start burner compressor unit, and gradually finish the startup, clean blow and ignition procedure of the gas turbine, and make wheel to speed up till rotate speed. 8.3.4 The operation control over centrifugal-flow compressor unit shall firstly satisfy the requirements of normal operation exchange work situation, that is, operate with high efficiency, prevent compressor unit from asthmatic vibration, and ensure safe and stable gas transmission. Exchange work situation requires the execution of the following:

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Firstly, centrifugal-flow compressor unit adapt to and meet the exchange work situation requirements, and realize flow regulation by rotate speed control system. Under normal operation condition, the exit pressure preset value of gas compressor station is the dominate control value, while inhale pressure value is subordinate monitor value. Under abnormal situations, when the gas consumption volume of the user become so enormous that even if machine unit is at highest rotate speed, the exit pressure preset value still can not be maintained, the inhale pressure value will perform dominate control function so as to maintain the lowest inhale pressure. In addition, in order to expand the regulation scope of centrifugal-flow compressor in some occasion, the performance curve of centrifugal-flow compressor is horizontally moved upwards. That is, to adopt the regulation method of changing the angle of pressure expander lamina, or changing the convolution of inhale gas current. But due to the complexity in its structure, this method is normally used as complementary subordinating regulation method. In addition to the abovementioned control through single machine changing rotate speed, to meet the exchange work situation requirement for station control system to adapt to gas compressor station, the cooperation of multi machines of the station shall also be selected so as to adapt to the changing requirements of big volume flow of gas compressor station.

On the side for the control system’s suitability to the varying duty of compressor station, except above single machine rotate speed control, it needs to make selection on multi-machine operation, only like this the system can be suitable for the variance of large flow rate.

For the compressor stations of multi-machine (same type) operation, the load distribution is finished by load distributor (programmable controller in the station), whose main control type is equal rotation speed control, to avoid complicated load distribution logic. The load distribution between each machine unit has relations with machine type, running efficiency, running stability, and controllability condition, etc. By relevant data description, the method to reduce the load when in centrifugal compressor multi-machine running is: to control the machine units by changing their operational parameters synchronously or orderly, the best scenario is to observe the running efficiency of the compressor station before making decision: when use orderly changing of the operation parameters to reduce the load, its general principal is that, the compressors with variable speed shall reduce the load firstly, followed by those constant speed compressors of lowest efficiency, at last followed by those constant speed compressors of highest efficiency; if the pressure gas volume in the station has great variance, the easiest way to increase or reduce the load is to open or close some machine units. It is reported that to use many small size machine units to be connected in parallel, can satisfy the requirement of flexible operation for flow increase or flow fluctuation. In short, station control system shall be able to meet the exchange work situation requirements, make control decision on machine unit’s changing load, and ensure machine unit to operate with high efficiency, stability and harmony. Machine unit shall provide on-spot control meter board and control room control board, which can live up to district anti-explosion level, and shall also provide all relevant utilities such as the instruments to control logics, alarm, record and monitor, the valves, rotative valves for PC system,

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and the control for subordinate system, and so on. The chief system functions of machine unit are as follows: 8.3.4.1 Program control over machine unit’s startup and shutdown, including subordinate system,

valve unit, and security interlock. Manual operation and half automatic operation mode shall apply to the startup/shutdown as well.

8.3.4.2 Machine unit main operation parameter, status display, record and alarm. 8.3.4.3 Receiving station control signal’s rotate speed regulation and load distribution. 8.3.4.4 Machine unit anti-asthmatic vibration, temperature protection, oil pressure protection,

mechanical protection, and startup/shutdown machine protection.

Thereinto temperature protection includes: inhale gas temperature protection of centrifugal-flow compressor vat and among segments; machine unit axletree temperature protection; and water temperature protection for mild cooling of lubricating oil. Oil pressure protection includes: oil pressure protection when centrifugal-flow compressor is working, water pressure protection (when setting water cooling), and hermetic seal oil pressure protection, etc. Mechanical protection includes; machine unit axes misplacement protection and mechanical vibration protection. In addition, there’s program automatic protection when starting up or shutting down machine. 8.3.5 Controlled station’s emergency shut down system. Gas transmission pipeline is a habitat for a large volume of high pressure and flammable gas, the gas transmission station of long distance pipeline in particular. Owing to its geographic condition, operation condition and other characteristics, many stations, especially pressure regulating meter station, are not watched. Gas compressor station in foreign countries normally adopts the managing method of “with engineer (minority) on duty, with no one to operate”. Therefore, although gas transmission pipeline is in hermetic condition, for such stations, safety monitor is very important and safety monitor system shall be very reliable. Station system is designed as a place where explosive gas mixture won’t appear under normal circumstances, and will only occasionally appear for a short period under abnormal circumstances. The potential risk can not be eliminated that gas mixture may form due to some unpredictable factors. Especially in places like gas compressor station, if machine unit and other pivotal utilities are installed in hermetic or half hermetic factories, it’s probable for flammable gas to congregate because of gas leak. Therefore, flammable gas leak detection system shall be equipped to the key parts where flammable gas may leak, and fire alarm detection system shall be equipped to the dangerous parts and regions where fire may happen. These two detection systems shall be taken into the emergency shut down (ESD) monitor control system. The system can send alarm right away upon discovering anything abnormal, and can immediately adopt automatic emergency measures and start up fire system upon noticing fire situation, so as to ensure the safety of the whole station.

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8.3.5.1 Emergency shut down system shall be automatic from the detection of dangerous situation to the startup of control. According to related reports, system will start alarm when the detected gas density reaches 20% of the minimum explosion limit, and shall ensure the immediate startup of emergency shut down system when gas density reaches 40% of the minimum explosion limit. In addition to the control spots (automatic) set in control room, ESD manual control switches shall be installed in compressor room and along the entrance and exit passages for station operation management staff, in an attempt to assure the sufficient reliability of emergency shut down system, and to achieve the purpose of manually on-spot startup of ESD. Certainly, these switches shall be installed in non-dangerous sectors, and a certain number of switches shall be in quite a few positions. This Article refers to the regulations stipulated in U.S.A. national standard 843.431 in ANSIB31.8. 8.3.5.2 After startup, emergency shut off system can accomplish the main functions stipulated in this Article reliably and in accordance with the prearranged logics requirements. Some data news deem that the whole ESD system shall be able to achieve: once emergency situation happens, 2 minutes after the startup of ESD system, all the pressure pipeline system in the station shall be relieved and blown down. 8.4 Monitor 8.4.1 Gas quality monitor. The gas quality required to enter gas transmission pipeline by this Criterion shall conform to the request of Item 3.1.2 and Item 3.2.6. The gas quality index shall be strictly controlled. In order for timely and efficient master of the changes of hazardous elements entering the main pipeline gas source, continuous automatic analysis and timely element analysis report shall be made for places which needs continuing monitor. For example, the receiving meter station entrance shall install online gas chromatogram device. Thus, once anything abnormal is discovered, the system can send alarm and, according to practical situation, adopt measures like cut off gas supply and blow off the underqualified gas etc. Places requiring general monitor can set up alarm when gas quality index exceeds limit. Furthermore, in gas compressor station, it has strict restrictions on the liquid content volume and mechanical impurity of the gas entering gas compressor unit. The fuel gas of gas turbine also has certain restrictions on the content volume of calcium, natrium and other metals, which shall be processed according to different requirements, and be properly controlled.

8.4.2 For the purpose to ensure the normal operation of equipment in gas transmission stations, the following parameters shall be kept continuous record and on-line supervision. 1) Key parameters in the course of technical processing; 2) Key parameters to ensure safety production; 3) The parameters of research and analysis for the purpose to improve technical process; 4) The parameters for business accounting or product quality control;. Generally the equipment of pressure adjustment and metering in gas distribution stations and gas

transmission stations are as simple as possible when their precision is ensured. But for gas compressor stations, because their system is complicated and the supervision parameters are many, the requirement of safety is relatively high, so they need to erect relevant meters for continuous supervision, indication and record.

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8.4.3 Pressure Monitor and Control 8.4.3.1 The transmission gas pressure of pipeline system transmission station shall be monitored and controlled, and shall not exceed the maximum operating pressure allowed. In addition to the installation of pressure regulating device with sufficient circulating capacity, pressure relief device, emergency shut down utility and pressure monitor and control utility with adequate power shall be equipped, in order to prevent lower system from over pressure. In transmission and distribution system, a verity model of pressure relief utilities can be selected. According to different situations, the following can be chosen respectively:

(1) Spring Pressure Relief Valve (2) Transmissional safety relief and blow-down valve (3) Monitor and Control Pressure Regulating Valve (normally set at the side of

downstream pipeline) series-mounted with operating pressure regulating valve

In general, safety shut down utilities are use with association with pressure regulating valve and blow-down valve in the control regulation loop, and perform the function of protecting downstream pipeline or utilities. Safety shut down utilities take the downstream station pressure as inductive and measuring signal, and are normally set at the upstream of regulating valve. In practical application, some important pressure control loops install 2 sets of series-mounting shut down valves, in order to ensure the absolute safety of downstream. Automatic shut down valve shall not be set up for object which has single loop regulating pressure gas supply and can’t allow interruption of gas supply, but shall turn to other control measures.

Station pressure control utility will inevitably become malfunctioned in the course of its

long-term operation. Therefore effective protection measures must be taken during design. In order to radically eliminate over pressure of downstream system during malfunction and ensure the reliable and continuous gas supply, monitor regulating control utility shall normally be set up, in addition to the pressure relief protection mentioned as above, so it can automatically start to operate upon the occurrence of accident. System switch upon accident shall strive to achieve smooth transition of each control loop or smooth control mode transition of each control loop itself. Drastic switch must not happen. 8.4.3.2 In foreign countries, ordinary small or medium sized gas distribution station and pressure regulating meter station is not managed by man. With the improvement of China’s pressure regulating control utility series and their performance, China has acquired the condition to realize “no man management”. The power supply for stations along the pipeline cannot always be secured. Whereas, the transmission medium of this system is natural gas, which has gas pressure energy to be utilized. Therefore the pressure regulating device (regulating valve) of station shall preferentially be self-powered, and normally don’t need instrument-controlled wind supply system unless specifically required. Self-powered pressure regulating device has many strong points such as simple structure, convenient maintenance, domestic products having basically formed series, and

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having mature application experience etc. It is mostly used in pressure regulating meter station. The transmissional regulating valve has better performance, and is fit for occasions with higher control pressure and larger flow. Small users of small flow can also use direct function regulator. The selection of regulator model shall sufficiently consider the requirements of regulated object, flow volume and pressure regulating performance. To prevent malfunction of pressure regulating system, the following measures are often taken (refer to regulator only):

(1) The important transmission and distribution system shall adopt the shunt-wound pressure regulating monitor system with over two loops. Once the operating loop breaks down, it will cut off, and the backup loop will automatically start up.

(2) Monitor and control utility (refer to pressure regulation only) shall be set on the loop where regulating valve is installed. The following methods can be taken:

(a) Set up monitor regulator (valve). In case the operating regulating valve is disabled, monitor regulating valve will automatically start up, and maintain the downstream pressure value to a slightly higher pressure value than normal. Generally the monitor regulating valve is set in the downstream of working regulating value, the benefit of which is to prevent mechanical impurity from aggrading on monitor regulating valve, and thus affect its normal action in emergency.

(b) Set up work monitor protection. This is to series-mount one working (operating) monitor regulator to a working pressure regulator, making it both in operation and monitor status. In case the working pressure regulating valve is malfunctioned, the working monitor regulating valve can bear the whole responsibility of pressure regulation. The regulation effect will be the same as (a).

(c) Series-mounting regulation protection. Series-mounting regulation protection is another monitor method. When the regulation valve at the side of upstream is malfunctioned, the second regulating valve takes over the entire regulation task. When the regulation valve at the side of downstream is malfunctioned, the first regulating valve takes over the pressure regulation responsibility. However, exit pressure is higher than two being sets series-mounting at the same time. Design shall make it within the maximum operating pressure scope allowed.

According to China’s specific application situation at present time, (a) and (c) are more adopted,

while (b) application is comparatively less. Those with bigger pressure decrease or requiring second level regulation can firstly adopt second level series-mounting pressure regulation and then monitor, or can use flexible combination according to practical situation.

In order to ensure the safety of the whole pressure regulating loop, the Criterion deem that pressure regulating valve, pressure control valve at the side of downstream, pressure blow-down valve and shut-down valve shall be selected according to the maximum pressure grade that it can endure in malfunction (Generally the valves in the same pressure regulation loop shall be selected with the same pressure grade).

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8.4.4 Temperature control. To avoid gas current temperature gets too low when downstream pipeline further reducing pressure, gas can be preheated before throttling. Special attention shall be paid to the gas with heavy hydrocarbon or with comparative high dew point.

(1) There are two ways for preheating: direct heating and indirect heating. For the sake of safety, indirect heating shall be used according to methods taken in foreign countries. For example, the heating of water set furnace. The effective way to control temperature is to feedback control the exit gas current temperature of pressure regulator, which shall be effective and automatic. In order to adapt to the changes of conditions (transmission volume and environmental condition, etc), the preset temperature value is required to be adjustable.

(2) As pressure drop is not big, some pressure reducing utilities don’t require the gas to be preheated before entering pressure regulating valve. However, for gas to enter the regulating and controlling utility command system, gas current ice block tends to happen, because the gas flow speed is comparatively slow, and the small pipeline line is prone to be affected by environmental temperature (especially in cold regions or cold winter). In case the above happens, partial heating method or low-volume electricity heating plus heating method can be taken. If condition permits, associated heating can be adopted.

Heating system shall set up reliable monitor control system. The following measures can be

taken:

(a) Ring Alarm upon temperature exceeding set limit. Extinguish fire to protect. (b) Emergency shut down system and blow down (upon fire accident) (c) Control of limited flow and limited pressure

8.4.5 Gas supply volume control. Gas volume distribution in gas transmission pipeline system must achieve supply-demand balance. When gas for civil use takes up a bigger portion among all the uses, or load increases, but there’s no other storage gas to coordinate, gas supply in the system shall be monitored and controlled. In stations where exceeding gas volume may incur accident, the flow volume shall be monitored as well. Normally flow control has the following measures:

For gas transmission Gas transmission Pipeline, flow control mainly focus on Gas transmission Pipeline’s gas distribution spots, where flow volume meter shall be set up. The flow volume meter shall have metering standards with national or industrial first level to keep to. When flow meter makes business accounting according to cubic flow volume, pressure, temperature, extra-compressing coefficient, expansion coefficient and other related coefficients shall be revised, and instantaneous and/or accumulated flow display shall be provided. Special attention shall be paid to the size of metering change and the suitable scope when selecting flow volume meter instrument. Different occasion shall use different type of flow volume meter instrument.

The metering of commodity gas requires a certain precision guarantee as precondition. To gas for civil use and gas for some industrial users and regions, its load has bigger change range, and thus requires for flow meter with a bigger range change spectrum. In China, the standard hole-board

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throttle device is most extensively used at the moment, which has a long history to trace and standards to follow. However, the ordinary usable range ratio of standard hole-board throttle device is 1:3 ~ 1:4, and range spectrum is limited. In order to adapt to the situation of big flow volume change, flow meter combination, which use multi loops to shunt-wound flow volume meters with same type but different sizes, is adopted for metering, and execute automatic meter loop switch according to the change of flow volume.

For situation where the change of gas consumption volume (gas supply volume) is big and needs to be restricted, or accident will be incurred if gas supply volume (gas consumption volume) exceeds limit, effective restriction measures on the exceeding of flow volume shall be taken. For example fuel gas consumption, startup gas consumption for gas compressor station, and gas consumption in other related occasions. The normal practice is as follows:

(1) For occasions where the maximum limit of flow volume shall be restricted within a certain preset range, flow restriction hole-board or flow restriction nozzle shall be used. For example fuel gas consumption, and startup gas consumption for machine unit, etc.

(2) To restrict the peak load of certain gas supply loop, pressure difference control method is always taken, that is, to achieve the limitation of flow volume by making use of controlling the difference pressure of hole-board. Another method is using the result of the flow metering to change the switch of an electric or pneumatic control valve, but the system is rather complicated. These two control methods have its own strong points. Whereas the latter is more convenient to operate, as the preset maximum limit value of flow volume can be changed manually at any time, and can accept remote setting.

8.4.6 This item is special for the safety control measures over the long distance transmission pipeline providing gas to various city stations. This kind of safety measure had been used in our country in the past gas transmission projects, but our country did not constitute relevant standards. In the other countries such as U.K., the Gas Engineers’ Association standard “Gas Transmission/Distribution System Construction Specification” IGE/TD/9; Germany “Inlet pressure 4-100 bar (including 100 bar) gas pressure adjuster design and installation” DVGWG491, have clear prescription on such kind of measure. In the design of pressure metering station in Shan-Jing project, Germany PLE company just used relevant DVGWG491 prescription to set the pressure adjustment and emergency cut off devices. When the gas pressure transmitting to the downstream direction has past the set value, the system will trigger instant cutoff; when the difference of possible highest inlet pressure and allowable highest outlet pressure is bigger than 1.6 MPa, and their ratio is bigger than 1.6, there are 3 combination measures. The pressure adjustment gas transmission device in Shan-Jing gas transmission pipeline project Bei Jing end station is using the first measure: each loop installed with 2 sets of safety cutoff devices in tandem, each such device can shut off the valve within 2 seconds after sensing abnormal pressure, the cutoff equipment is zero leaking. For the purpose of safety, 2 sets of cutoff equipment are sensing the same pressure signal in tandem, have same performance. Basically the gas transmission systems in Europe are using this rule, which has become a standard measure. For above three combination measures, the frequently used is generally the first one. For which one to choose at last, it needs to consider the real situation and to whom and to where the gas is provided, as well as consider the elements of equipment and price, etc., before making final decision.

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8.5 Communication 8.5.1 The communication system of gas transmission pipeline projects include voice communication, data communication, telautogram, fax and so on. Data communication, to be used in SCADA system, connect the host computer system located in gas transmission control center and remote terminal unit located in controlled station, and thus accomplish all fronts monitor control and data collection. Voice communication is to provide special telephone line service to gas transmission control center, maintenance center, gas compressor station and main pressure regulating meter station. Mobile wireless telephone system is the communication facility provided for pipeline patrolling, field accident handling and other occasions. In short, communication system shall be able to satisfy the needs for production operation and control management, and can live up to the requirements of being economical, feasible, speedy, accurate, reliable convenient, and of advanced technology. The design of communication system shall be able to meet the requirements that SCADA system of transmission pipeline holds for communication quality, for example the rate for code miscarriage of digital fax, transmission speed, channel numbers, transmission and operation mode, terminal interfaces etc. To be consistent with SCADA system, communication system shall meet requirements of both digital fax and voice communication. 8.5.1.1 The choice of communication method shall firstly consider the characteristics of long distance gas transmission pipeline system, and shall be able to:

Suitable for the catenulate communication of long distance gas transmission pipeline; Be a digital communication system with big capacity, high reliability and good quality; Long distance between stations, and long relay. Relay station shall have small power waste, and can achieve “no one on watch”; Have the capability to withstand natural disaster and industrial accident. Be an integrated communication system with multi modes and means; Flexible in building network, easy to expand, convenient in upper and lower communication channel, and capable of keeping confidentiality; Building network in a verity of communication modes and shall conform to the uniform regulations and criterion.

With the development of pipeline system, SCADA system of long distance transmission Gas transmission Pipeline will expend its controlled object considerably. Therefore, communication system shall leave sufficient room for future development. 8.5.1.2 The reliability of communication system’s channel is of vital importance to SCADA system. As onefold communication mode is hard to secure its operation reliability, pipeline system shall provide another communication mode as backup, in addition to one certain communication mode (microwave or fiber) under normal circumstances. For oil or gas pipeline, dispersive relay communication is a comparative economical means as backup. However, it has got problems such

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as bulky facilities, high power consumption, unstable signal etc.

The number of SCADA system date transmission channel has not been uniformly regulated so far. It is concerned with the process requirements of gas transmission control management such as scan period for petrol and inspection (the processing time requirement upon controlled station’s malfunction), and with the usage rate of central host computer and other factors. Take Qun-Shen pipeline for instance. Canada NuFa Company use single channel, and scan period to be 1 ~ 2 minutes; whereas German PLE Co. adopts 5 channels and scan period about 10 seconds. The host computer usage rate of the former is about 15%, while the latter is about 32% (at the same baud value). Generally speaking, the scan period of gas transmission pipeline, unlike that of oil transmission pipeline can be a bit longer with the precondition of a comparatively consummate station control system as guarantee. This is acceptable as long as the scan frequency is bigger than data update time under worst situation, so that central host computer can timely receive all the information from remote terminal. 8.5.1.3 Communication station shall be installed in all levels of gas transmission management units or controlled stations along the pipeline, purposed for union management convenient. 8.5.1.4 The operation types of communication. This Criterion deems administrative telephone can be used as conference telephone line, and no need to be set up separately. With the consideration of communication between stations during operation, in-between telephone among stations shall be installed, which is especially important for stations to keep in touch when they break away from SCADA system. 8.5.2 In-station Telephone. 8.5.2.1 For long distance transmission pipeline communication center, transmission control center, gas compressor station, large scale gas distribution station, large scale receiving meter station etc, due to their complicated system, there’s need for in-station control and contact, and need for regular contact with places outside the system. In light of the present managerial system of China’s long distance gas transmission management departments, these stations are suggested to use full automatic program controlled telephone exchange without watchman for automatic dialing internal control. If condition permits (e.g. close to local telephone bureau), 1 ~ 2 relay lines can be set up to connect with local telephone department, providing external contact telephone line. Gas compressor station, which doesn’t supply gas to external units, can do without relay line.

Ordinary small or medium sized gas distribution station, included in SCADA system, only needs to set up special telephone to keep contact with control center, neighboring station, and local relative departments (e.g. city gas supply station). 8.5.2.2 Station’s main installation area, workshop for auxiliary production and public utilities, fire fighting station, control room, transformer substation, gas collection / distribution station, water pump room, etc, as well as station office and other relative departments can set up extension. Explosion proofing communication facility should be equipped at explosion area, and prohibit non-explosion proofing facilities to be used at explosion production areas. Operational staff, who

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make in-station itinerant patrolling, inspection and maintenance, can carry potable transmitter receiver to keep in touch with station controlling staff. 8.5.3 Mobile Communication. In order to meet the convenient communication needs for pipeline itinerant inspection, accident reparation, daily maintenance, putting into production or expansion, mobile (normally carried by car) communication facility shall be set up, so that the mobile staff team can make contact with neighboring communication system and transmit to the department to be informed through wireless communication system.

9 Auxiliary Production Facility (pg 137 – 143)

9.1 Power Supply 9.1.1 Deriving power source from local power supply system to provide power for gas transmission station’s production and civil use is an effective way to reduce station construction investment, and simplify production management. Therefore, the Criterion firstly recommends that gas transmission station obtain electricity from local power supply system. When it’s impossible for the region where station locates to obtain such power supply, self-provided power source is allowed. The Criterion stipulates that self-provided power shall use gas to generate electricity. This not only is in keeping with China’s energy policy, but also simplifies the equipment and management of electricity self-generating facility. Furthermore, it’s more convenient for transmission station to obtain gas. 9.1.2 Power voltage of gas transmission station mainly indicates the power supply voltage and power consuming facility voltage of the electricity transmission line. For gas compressor station and other stations, which are not driven by electromotor, the voltage grade for electricity consuming facility normally is 220/380V. Gas compressor station, which is driven by electromotor, probably uses high voltage electromotor of 6000V. The design of station’s power voltage grade shall be decided with consideration of electricity consuming facility requirements, the grade of power grid voltage, the distance of electricity transmission line and other integrated factors. 9.1.3 The confirmation of gas transmission station’s power load grade bears very important meaning to ensure safe production, continuous gas transmission, and unite design standards. In addition to reference of the regulations stipulated in “Design Criterion for Power Supply System” (GB 50052), the Criterion decides station’s power load grade also in accordance with many important factors such as the operation characteristic gas transmission pipeline, the importance of normal production for all types of gas transmission stations etc. Gas transmission pipeline, especially long distance big caliber transmission pipeline, is the energy supply line for a certain region or a number of enterprises. It is in close connection with many important industrial productions and (or) the life of the vast city citizens. Although during power cut there won’t be casualties or serous damage to utilities in stations, due to the negative and extensive influence that power cut will bring forward, adequate attention shall be placed on station’s

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power supply grade. 9.1.3.1 The Criterion stipulates that gas compressor station using compressor driven by electricity shall be Grade Ⅰ Power Load. The reasons are as follows: Firstly, Voltage Increasing Station is the heart to gas transmission pipeline, and the utility to provide energy for gas to move. Once compressor stops working, gas transmission volume will be greatly reduced and even stopped, and thus will incur extensive impact on the downstream enterprises and civil gas use. Therefore the energy to drive compressor shall have practical and reliable guarantee. Secondly, as is stipulated by the Criterion, the power for compressor of gas transmission pipeline compressor station shall adopt gas turbine or gas generator. In regions where there is sufficient electricity, electromotor can be adopted as power facility. Under such conditions, it’s not difficult to obtain GradeⅠpower load, and won’t excessively increase construction investment.

Thirdly, such as Shan-Jing gas transmission pipeline project has the pressure stations which are driven by combustion turbine, within which the startup and lubrication pump in combustion turbine, compressor and other accessory machines are driven by electricity. The dependability of providing gas to Beijing must be high. These pressure stations which are driven by other kinds of power, but the requirement for the dependability of power supply is very high, still can be grade 1 workload power supply. 9.1.3.2 Other stations’ dependence on electricity is less than that of gas compressor station driven by electricity. Furthermore, in such stations there’s nearly no continuously running facility which use electricity power. In the event that gas transmission station located along the long transmission pipeline has difficulty obtain electricity power, and in order not to increase excessive investment, the Criterion stipulates that other gas transmission stations, with exception to electricity-driven gas compressor station, shall use Grade Ⅱ power load. Substation at branch, if the local user of gas supplied use Grade 3 power load, this substation can use Grade Ⅱ power load. 9.1.4 The degree of contingency lighting for accident in gas transmission station is stated in accordance with related regulations stipulated in “Industrial Enterprise Lighting Design Criterion” (GB 50034) and “Gas Field Natural Gas Refinery Design Criterion” (SY/T 0011). It shall be noted that as the operation of ordinary station is quite simple, the accident contingency lighting shall be installed in control room, compressor or compressor room in particular, and shall not be evenly installed. This can ensure the need for normal operation is met during power cutoff. 9.1.5 In gas transmission station with Grade Ⅱ power load, when power supply can’t guarantee uninterruptible power supply (UPS), storage battery unit , countercurrent power, or fast startup small scale gas generating facility are set up to backup station’s automatic control system, communication system, and accident contingency lighting system. This is to ensure and maintain the normal production order or smooth production stop upon sudden power cut.

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9.1.6 As is stated in the Criterion, the division of explosive dangerous regions in all types of stations along the gas transmission pipeline shall conform to the regulations stipulated in “Division for petroleum” (SY/T 0025). This is because that the regulation is in keeping with the practical status of China’s oil and gas field production, and the division methods is the same as international standard API RP 500. 9.1.7 According to our country’s many years of experience from engineering designing of natural gas transmission station, the air escape vertical pipes designed by this principle have never ever been damaged by thunderstroke, so this kind of lightning protection is workable.

9.2 Water Supply and Drainage

9.2.1 Mainly stipulates the principle for water resource selection. Due to that the water consumption for production and living in most gas transmission stations is not much, and not continuous, and most station also not set fire fighting water supply system, so under general situation, it is better to use a same water resource, so as to minimize the work of construction, and save the investment. 9.2.2 The Criterion stipulates the method to calculate the volume of production water. Two points need specific explanation as follows: Firstly, station’s production water usage volume is generally small, and site response to the index for water of living, stipulated in Government standing standards, is rather low. Therefore, the Criterion raises the unpredictable water usage volume to 15% ~ 20%, so as to expect the total water usage volume to be increased. Secondly, for water obtaining capacity of water transmission pipeline and water source, if gas transmission station has already built safety water pool, which can ensure adequate fire-fighting water not be used for other purposes, fire-fighting water consumption volume can be excluded from total water volume. By doing this, it won’t place negative impact on safe production, but also is beneficial to reducing the construction cost for water source project. 9.2.3 For gas transmission station requiring a large volume of water for production, normally safety water pool shall be built when water supply system is not practically guaranteed, for example the power supply grade for obtaining water is rather low, water is supplied by single water transmission pipeline etc. This is to ensure there is adequate water to maintain normal production and fire fighting once water supply system has accident. 9.2.3.1 Shall make full use of landforms, and build plateau pool, and shall do so wherever condition permits. Plateau pool can not only save energy, but also ensure the smooth use under accident condition (e.g. power cut). 9.2.3.2 Production and living water consumption in gas transmission station is relatively little, most stations are located at mountain and desert areas in where the traffic is difficult and rarely populated, equipment maintenance is hard. Original water reserve for these stations is 6-8 h, which would be too little. Consider their real geological and weather conditions, the water reserve for production and living shall be increased to 8-24h daily.

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9.2.3.2According to the regulations stipulated in Article Seven in Item 8.3.4 of “Construction Design Fireproofing Criterion” GBJ 16, safety water pool’s cubage shall satisfy fire fighting water usage volume, and must not be used for other purposes. Therefore, safety pool shall set up measures to prevent fire-fighting water from being used in other ways. 9.2.4 This item stipulates the standards for various waters of different quality. 9.2.4.1. It stipulates the water quality standards for production and living consumption. To follow

these requirements is to ensure normal production operation and workers’ health. So, in case the living consumption water can not meet the relevant standard, it must be necessary to erect a set of small-scale living water treatment device.

9.2.4.2. The specification of the quality and treatment method for circulate cooling water is “Design Specification for the Treatment of Industrial Circulate Cooling Water”.

9.2.5 Waste water drainage shall conform to the standards regulation by the nation Discharge of sewage shall conform to relevant state standards. By common design practice, the water discharged from inner-station production, living, and raining shall be separated according to clear and polluted parts, so as to effectively reduce the water volume that needing treatment process, and save the expense. The unpolluted water from ground washing and raining can be directly drained out of the station along the ground and roadside water ditch, while the polluted water such as equipment cleaning water and pipeline cleaning water may contain some oil or grease, they need to be treated before being drained out. Since the volume of these water is small, and they are not discharged continuously, so they are easy to dispose. For the living water discharge, such as toilet water and other washing water, they need to be treated by cesspool, then see whether they need further treatment before final discharge according to the station location, administration district, environment situation and the relevant drainage standard needed to follow, etc. 9.2.6 Under what circumstance the transmission stations need to set fire fighting water supply system, under what circumstance the transmission stations don’t need to set fire fighting water supply system, the scale of fire fighting water supply, and other fire fighting equipment such as the type of fire extinguisher, specification and number, etc, all these issues are quantitatively regulated in “Fire Fighting Specification for Petroleum and Natural Gas Project Designs ”, so this specification requires that all fire fighting designs shall follow the description of above specification. 9.3 Heating, Ventilation and Air Conditioning 9.3.2 Indoor Heating Temperature Calculation 9.3.2.1 The values listed in Chart 9.3.2 of the Criterion is decided in accordance with the principles stipulated in “Industrial Enterprise Sanitary Design Criterion” （TJ36）, and with reference to the related regulations stipulated in “Gas Field Gas Collection Project Design Criterion” (SYJ10), and “Design and Technology Regulations for Oil Refinery Heating, Ventilation and Air Conditioning”(SYJ1030). Winter indoor heating calculated temperature of compressor workshop shall be a bit lower than 12 ~ 14℃ as is stipulated in (SY/T 0010) and (SYJ1030). The

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reasons are as follows:

(1) Compressor workshop is an environment with high noise. Staff only does itinerant inspection over the workshop, and the continuous stay time is less than 2 hours. In the event that staff must monitor the operation status of the machine unit at any time, a duty room is normally built inside the compressor workshop. Therefore, if the winter indoor heating calculated temperature of compressor workshop is lower, it can satisfy the environment’s requirements.

(2) Gas compressor workshop is very big in dimension, and ventilation frequency per day for normal use is consequently higher. If the indoor heating temperature is high, it will definitely increase energy consumption.

9.3.2.2 Building with special requirements mainly refers to the building with installation of instrumentation for metering, controlling and regulating systems, or building with special requirements like computer room, etc. 9.3.2.3 Other buildings mainly refer to buildings for administration, office and medical. 9.3.4 Ventilation Design for Production Building 9.3.4.1 It is a fundamental principle for the design of industrial production and environmental protection that the processing courses which may produce deleterious element or gas shall be hermetically sealed. In case hermetical seal cannot be achieved, partial ventilation or all-round ventilation measures shall be taken, so as to ensure the air quality in the building reaches sanitation and safety requirements. The explosion minimum limit and density allowed for the deleterious element or gas emitted from stations of gas transmission pipeline are listed in Chart 7:

Deleterious Element and Gas’s Explosion Minimum Limit and Density Allowed Chart 7 Component Explosion Minimum Limit

(%) (Cubage) Density Allowed In workshop air (mg/m3)

Methane 5.0 -- Ethane 2.9 -- Propane 2.1 -- Butane 1.8 -- Pentane 1.4 -- Sulfureted Hydrogen 4.3 10 Carbon Monoxide 12.5 30 Hydrogen 4.0 -- In deciding building’s ventilation frequency, the density of deleterious element must reach the regulated value of sanitary standard. However, the density of gases, which are not regulated by sanitary standard, but prone to explosion, such as methane, ethane etc, must be controlled below safety density. China’s “Design Criterion for Heating, Ventilation and Air Conditioning” (GBJ 19)

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does not have specific regulation on the allowed density for explosive gas in building. As is stipulated in Item 4.101 of the construction law of former Soviet Union “Design Criterion for Heating, Ventilation and Air Conditioning” (CHHⅡ – 33 – 75): For partial ventilation system, which is to eliminate substances containing explosive dangerous elements, and all-round ventilation system with the same quality, the wind volume shall ensure that the density of explosive dangerous gas and steam not to exceed 5% of the explosion minimum limit. The Criterion deems that to decide the ventilation volume of the building containing explosive dangerous gas, it shall regulate the allowed density of explosive gas, and take it as calculation reference. The principle to regulate such a density shall aim at: not only ensuring production safety, but also not increasing the construction cost and energy consumption by excessively increasing ventilation facility. The regulations of former Soviet Union were so high and so strict that to meet the requirements they had to time the ventilation volume of the building. According to the following information, it is proper to regulate the explosive minimum limit density to be 20%.

(1) Article Two Item 2.2.3 of China’s “City Gas Design Criterion” GB 50028 regulates: When city gas adding smell degree is equivalent to the gas density of 20% of explosion minimum limit, it can be sensed.

(2) American Fire Fighting Committee regulates: When replacing flammable gas, it shall make sure the density of flammable element in the gas after replacement no higher than 20% of the element’s explosion minimum density, or replaced gas volume no lower than 5 times of the dimension.

(3) At present time, all kinds of flammable gas density detection alarm devices made in China normally set the alarm limit density to be 20% or 25% of gas explosion minimum limit density.

According to Item 10.3.2 of “Construction Design Fireproofing Criterion” (GBJ16 – 87), A

grade factory or place, which emits flammable gas or steam, shall install flammable gas density inspection and leak detection alarm device. The alarm density of leak detection device can be 20% or 25% of the flammable gas explosion minimum limit. When alarm device sends signal, the flammable gas density in the air is only 1/4 ~ 1/5 of the minimum limit density, and thus there is still adequate time to handle. Therefore, it is safe to regulate the density as the calculated density of replacement gas volume. 9.3.5 This Item is regulated in accordance with Item 4.4.9 of China’s “Design Criterion for Heating, Ventilation and Air Conditioning” (GBJ19). The ventilation times and system setting for compressor workshop’s accident ventilation is stipulated by combining the reference of Item 4.107 of former Soviet Union “Design Criterion for Heating, Ventilation and Air Conditioning” (CHHⅡ – 33 – 75), and the design criterion of China’s gas field collection and distribution and oil refining.

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10. Welding, Inspection, Pipeline Pigging and Pressure Test

(pg 144 – 145)

10.1 Welding and Inspection

10.1.3 For gas transmission pipeline, especially long distance gas transmission pipeline, the natural condition and construction condition of the regions that pipeline goes by differ considerably. New brands of high and strong low alloy steel pipe material are widely used. Therefore, construction company shall execute process test according to regional construction condition, the grade of pipe material steel, welding material and other factors, and shall compile welding process brochure. 10.1.6 The quality and choice of welding material is the key point to ensure welding quality. Welding material shall be selected in accordance with Item 3.0.4 and 3.0.5 of “Execution, Inspection and Approval Criterion for Site Equipments and Industrial Pipeline Welding Project” (GB 50236). 10.1.7 The selection of slope mouth type shall take into consideration several aspects including ensuring welding tie-in quality, saving filling metal, easy to operate, reducing welding distortion, and meeting pigging process requirements, etc. 10.1.8 The purpose of heating before welding and heat treatment after welding is to eliminate or reduce the residue stress of welding fitting tie-in, prevent welding seam or mother material from cracking, and improve metal organization and material performance within the heat impacted area of welding seam and metal. Whether welding seam can eliminate residue stress, in addition to structure, purpose, working condition, and material performance, thickness is a main factor. The thickness value stated in this Item is decided according to American national standard – ANSI B 31.8. 10.1.9 The inspection of welding seam quality is one of the key factors to ensure welding quality. The Criterion regulates three procedures to conduct the quality inspection of welding seam, that is, appearance inspection, non-destructive test and destructive test. 2. This item emphasizes that all welding joints shall carry out 100% no-damage crack inspection, to avoid missing because of the limitation of single detection method; and according to the progress of welding techniques and construction methods, the name of “Flow operation welding group” has been added. 3. Add this item is to suit the situation that because of large-caliber pipelines, weather or other objective causes, the number of welding points finished by each welder or each flow operation welding group per day may not satisfy the recheck rate requirement stipulated by the No. 2 clause in item 10.1.9.

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10.2 Pipeline Pigging and Pressure Test

10.2.3 The medium and pressure in strength test shall be decided in accordance with the related regulations stipulated in American national standard – ANSI B31.8. 1. (3) In light of America ASME.B31.8 (1999 revision) and America federal compulsory regulations “Federal Pipeline Safety Regulations” 49 CFR 192 natural gas part (1999 revision), the pipeline air pressure trial conditions for grade 3 and 4 areas and transmission stations are added.

10.3 Dry 10.3.1 This item is constituted referring to the current practice of the country, Royal Netherland Shell Group corporate standards DEP31.4.50.30—Gen “Pipeline Pre-commissioning” (1994), and America engineering construction practice, etc. 10.3.3 This item is constituted referring to Royal Netherland Shell Group corporate standards DEP31.4.50.30—Gen “Pipeline Pre-commissioning” (1994), domestic construction experiences, and item 3.1.2 of this specification on gas quality of pipeline transmission. Royal Netherland Shell Group corporate standards DEP31.4.50.30—Gen “Pipeline Pre-commissioning” (1994) prescribes:

when using air for drying, the dew point of injected dry air shall be at least 15℃ lower than the

pipeline dew point required by this project’s regulations; when using nitrogen gas for drying, the

dew point of injected nitrogen gas shall be lower than –50℃ under normal atmospheric pressure.

11. Energy saving, environment protection, labor safety/hygiene 11.1 Energy saving This section is constituted by referring to the relevant items of “Energy Saving Law of P.R. of China” , “China Energy Saving Techniques/policies outline – China Petroleum & Natural Gas Group Company Implementation Rules ”- Zhong You Zhi Zi (1999)No.33 (Oil field and long-transmission pipeline part)” , together with considering the characters of natural gas long-transmission pipeline. 11.2 Environmental protection This section is constituted by referring to the relevant items of “Environmental Protection Law of P. R. of China” and the “Water and Soil Conservation Law of P. R. of China”, as well as country’s other relevant standards, together with considering the characters of natural gas long-transmission pipeline. 11.3 Labor safety/hygiene This section is constituted by referring to the relevant items of “Safety Production Law of P. R. of China”, the “Petroleum/Natural Gas Pipeline Safety Supervision and Management Regulations” of state’s Economy & Trade Commission, the “Pressure Pipeline Safety Management and Supervision Regulations” of state’s Department of Labor, “Construction Project (Engineering) Labor Safety/hygiene Supervision Regulation”, “Petroleum/Natural Gas Industry Health, Safety and Environment Management System”, together with considering the characters of natural gas

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long-transmission pipeline.

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