pttchem-sp-p-602-000 underground piping construction.pdf

PTT CHEMICAL PUBLIC CO., LTD. BRANCH I-1: OLEFINS PLANT

STANDARD SPECIFICATION FOR

UNDERGROUND PIPING CONSTRUCTION WORKS

DOCUMENT NO. PTTCHEM-SP-P-602

REV. ISSUED DATE DESCRIPTION REV. TO

SHEET

ADDED

SHEET

MADE

BY

CHECK

BY

APPROVE

0 7 Dec 05 First Issued Prathanwit Chayan

TOTAL PAGES 39

(INCLUDED THIS PAGE)

UNDERGROUND PIPING CONSTRUCTION WORKS PTTCHEM-SP-P-602

PAGE 2 OF 39

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SECTION CONTENT PAGE

1. SCOPE 4

2. APPLICABLE CODES 4

3. RELATED ENGINEERING SPECIFICATIONS 4

4. DRAWINGS AND REFERENCES FOR WORKS 5

5. WORK FLOW 5

6. EXCAVATION 6

7. BURYING 6

8. CUTTING AND BENDING 8

9. THREADING 8

10. WELDING 9

11. PREHEATING AND HEAT TREATMENT 18

12. ASSEMBLY 19

13. FLANGED JOINTS 21

14. PROTECTIVE COATING AND WRAPPING 22


PAGE 3 OF 39

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SECTION CONTENT PAGE

15. INSPECTION 22

16. PRESSURE TEST 27

17. PRESERVATION 33

18. FLUSHING 35

19. DOCUMENTATION 37

APPENDIX-1 SUPPLEMENTARY RT REQUIREMENTS 38


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1. SCOPE

This specification covers the general quality requirements for the fabrication, inspection and testing of

underground piping system on the plant site, excluding transfer pipe line.

2. APPLICABLE CODES

ANSI / ASME B 31.3 : Chemical Plant and Petroleum refinery Piping (up to B31.3b-1986)

3. RELATED ENGINEERING SPECIFICATIONS

The following Engineering Specifications are related to herein :

(1) PTTCHEM-SP-P-

103

Piping Materials (Underground Pipings)

(2) PTTCHEM-SP-P-

605

Welding Procedure Specifications of Underground Pipings

(3) PTTCHEM-SP-P-

805

Welding Performance Qualification Test of Underground Pipings

(4) PTTCHEM-SP-P-

121

Protective Coating and Wrapping for Underground Steel Piping


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4. DRAWINGS AND REFERENCES FOR WORKS

4.1 The following drawings and references necessary for the work will be prepared by PTTCHEM.

(1) Plot plan

(2) Piping Arrangement Drawings (Plan and Elevation)

(3) Piping Material Classifications

(4) Notes for Piping Drawings

(5) Others, if any

4.2 All drawings and related documents shall be in English language and the metric units of measurement

shall be used except for pipe sizes, flanges and flange bolting.

4.3 Welding symbols, terms and definitions shall be in accordance with AWS A2.4 and A3.0. (PTTCHEM-

SP-T-003, Par. 4.1)

5. WORK FLOW

Underground construction works shall normally be performed in the following sequence.

Step Work Description

1. Check & confirm the pipe route & measure pipe length & level

2. Coating work for straight pipe & fitting

3. Pin hole test

4. Carry out the excavation work

5. Provide the Bell Hole at the each pipe joint for welding activities

6. Laying the pipe on the temporary support for the welding work

7. Welding work

8. Radiographic & visual inspection for welds


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9. Hydrostatic test

10. Proper cleaning on the pipe surface for the wrapping work

11. Coating / wrapping work for joint portion

12. Pin hole test

13. Provide the pipe support & remove the temporary support

14. Backfilling work with proper compaction

6. EXCAVATION

6.1 Depth of burial of pipes shall be as indicated in Piping Arrangement Drawings. Excavation shall be

done considering safety of the work. Especially, if depth of vertical excavation is deep, the piping

works shall be done after protective measure is taken to prevent landslide.

6.2 Before the excavation work, Contractor shall confirm that there is no other buried object around the

place of excavation.

6.3 Pipe casings shall be provided according to the Piping Arrangement Drawings.

7. BURYING

7.1 When works of burying pipe are carried out, protective measures to prevent accident such as

landslide, flooding of water, downfall of workers, ect. shall be taken into consideration fully.

7.2 During underground piping works, full care shall be taken to prevent soil and sand from flowing into

pipes and to prevent pipes from refloating due to underground water or rainwater.

7.3 When back-filling is carried out, small-grain sand shall be used for the parts directly contacting with

pipes.

7.4 Back-filling work shall be done so that the coated and wrapped surface of the piping will not be

damaged.


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7.5 Back-filling with small-grain sand shall be done as shown in Fig. 7.5

7.6 Additional soil and sand containing gravel, crushed stone or similar can be used only for upper portion

of underground pipes as shown Fig. 7.5.

7.7 Back filling shall be done with appropriate tamping and to have 5 - 100 mm overheaping. Tamping

method may be any one of the followings.

(1) Water binding method

(2) Rammer method

(3) Vibrator method

(4) Compact roller method

(5) Combination of above method

FIG. 7.5


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8. CUTTING AND BENDING

8.1 Pipes and fittings shall be cut with cutting machine and beveled by machine, grinding, etc. according

to the shapes specified in the WPS.

8.2 Cutting surfaces shall be cleaned with grinder.

8.3 Butt weld end preparation is acceptable only if the surface is reasonably smooth and true and all slag

from oxygen or arc cutting is cleaned from flame-cut surfaces. Discoloration which remains on a

flame-cut surface is not considered to be detrimental oxidation. (B31.3, Par. 328.4.2(a) (1))

8.4 Preheating may sometimes be instructed prior to thermal cutting according to Par. 11.

8.5 In case pipe cutter shall be used for piping works, the inner surface of pipe at cut-end shall be well

finished by reamer or file.

8.6 Seamless pipe having nominal size up to 1.1/2 inch shall be bent with a radius of 5 times the outside

diameter of the pipe in cold state as a rule, and this work shall be made by pipe bender.

9. THREADING

9.1 Thread to be used for pipe be "American Standard Taper Pipe thread (NPT)" stipulated in ANSI

B1.20.1.

9.2 Seal tape or liquid gasket shall be used for threaded joints as a rule.

9.3 In case where pipes are seal-welded after screwed-in, lubricant, seal tape, etc. shall not be used, and

all exposed threads shall be covered by the seal weld.


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10. WELDING

10.1 General

(1) No welding shall be commenced without the welding procedures qualified.

(2) Welders involved shall be qualified by PTTCHEM prior to the start of production welding in

accordance with Engineering Specification PTTCHEM-SP-P-805, Welding Performance

Qualification Test of Underground Pipings.

(3) Welding shall be performed in accordance with Engineering Specification PTTCHEM-SP-P-

605, Welding Procedure Specifications of Underground Pipings.

(4) All welds shall be immediately after completion of welding provided with the welder's

identification stamp. For such cases where stamping will be deleterious to the parent material

(thin materials, notch sensitive materials, stainless steel, non-ferrous materials, ect.) stencil

stamping / marking may be Substituted for such die-stamping and shall be maintained until

PTTCHEM's inspection complete.

(5) Welding materials such as electrodes and fillers shall be properly stored, and shall be properly

heated/dried before use.

(6) Peening is only permitted to the extent necessary to clean the weld. (PTTCHEM-SP-P-T-003,

Par. 7.5)

Peening is not permitted on the root pass and final pass of the weld.

(7) Fillet welds (including socket welds) may vary from convex to concave. The size of fillet weld s

determined as shown on Fig. 10.1.A. (B31.3, Par. 328.5.2)

Typical weld details for slip-on flanges and socket welding components are shown in Fig. 10.1B

and Fig. 10.1C. (B31.3 Par. 328.5.2(a))

UNDERGROUND PIPING CONSTRUCTION WORKS PTTCHEM-SP-P-602 PAGE 10 OF 39

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(8) No weld shall be covered/concealed by external attachments such as pads.

(9) Grounding wire shall be firmly fastened by screw or clamp to the material to be welded.

(10) The root pass of single butt joints shall be welded such the complete penetration to be attained.

Equal Leg Fillet Weld Unequal Leg Fillet We

NOTE

:

The size of an equal leg fillet weld is

the length of the largest inscribed

isosceles right triangle (theoretical

throat = 0.707 X size).

NOTE : The size of an unequal leg fillet weld leg

lengths of the largest right triangle which

can be inscribed within the weld cross

section (e.g. 1/2 in. x 3/4 in.) (B31.3, Fig.

328.5.2A)

FIG. 10.1A FILLET WELD SIZE


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FIG. 10.1B - TYPICAL DETAILS FOR DOUBLE-WELDED SLIP-ON

AND SOCKET WELDING FLANGE ATTACHMENT WELDS

FIG . 10.1C - MINIMUM WELDING DIMENSIONS FOR SOCKET WELDING

COMPONENTS OTHER THAN FLANGES

(11) No welding shall be done if there is impingement on the weld area of any rain, snow, sleet, or

excessive wind, or if the weld area is frosted or wet, unless an appropriate protection s

provided. (B31.3, Par. 328.5.1 (e))

(12) Welding shall not be performed when the ambient temperature is below 5 °C, unless the pipe is

preheated as per Par. 11.

(13) internal and external surfaces to be welded shall be clean and free from paint, galvanized paint,

oil, rust, dirt, loose scale, or other material that would detrimental to either the weld or the base

metal under welding conditions. the adjacent base metal surfaces shall be cleaned, too, within

25 mm from the edge of the joint. (B31.3, par. 328.4.1) (PTTCHEM-SP-T-003, Par. 7.3)


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(14) Inside of circumferential weld bead shall not have any burr or fragment of welding rod and all

adhering substances shall be removed once located.

(15) Spatter, slag, etc. shall be thoroughly removed.

(16) Weld defects shall be completely removed by chipping, gouging, grinding, or other methods

(suitable for the type of material being repaired) to sound metal, and the excavated area shall

be examined by liquid penetrant methods to assure complete removal of defects.

(17) Repair welds shall be made using the same Welding Procedure used for the original weld or

any other previously approved Welding Procedures.

(18) The repaired welds shall be re-examined as required for the original welding.

(19) Any weld repairs of solid material (plate, forging, pipe, etc.) need the approval of PTTCHEM

and shall be performed using such procedures only, that are approved by PTTCHEM.

(20) All site-welding activities shall be done under proper protection against weather conditions to

the satisfaction of PTTCHEM.

(21) Contractor shall maintain proper records containing all relevant information on each and every

welder performance as the work progresses.


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10.2 Edge Preparation and Alignment

(1) Circumferential Welds

(a) If component ends are trimmed as shown in Fig. 10.2A. for correcting internal misalignment,

such trimming shall not reduce in a finished wall thickness below the required minimum wall

thickness, "tm". Where necessary, weld metal may be deposited on the inside or outside of the

component to provide alignment. It is also permissible to size pipe ends of the same nominal

size to improve alignment, if the above wall thickness requirements are maintained. When a

girth weld joints components of unequal wall thickness and one is more than 1.1/2 times

components of the other wall, end preparation and geometry shall be in accordance with

acceptable designs for unequal well thickness in ANSI B16.5.

(B31.3, Par. 328.4.2(b) (1), (4) & (5))

FIG. 10.2A - TRIMMING AND PERMITTED MISALIGNMENT

(b) Inside surfaces of components at ends to be jointed in girth or miter groove welds shall be

aligned within the limits in the WPS. If the external surface of the two components are not

aligned, the weld shall be tapered between them. (B31.3, Par. 328.4.3 (a) (1) & (2))

(2) Branch Connection Welds


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(a) Branch connections which abut the outside surface of the run wall shall be contoured for grove

welds which meet the WPS requirements. (B31.3, Par. 328.4.3(c) (1)) (See Fig. 10.2B)

FIG. 10.2B PREPARATION FOR BRANCH CONNECTIONS

(b) Run opening for branch connections shall not deviate from the required contour by more than the

dimension "m" in Fig. 10.2B. In no case shall deviations of the shape of the opening cause the root

spacing tolerance limits in the WPS to be exceeded. Weld metal may be added and refinished if

necessary for compliance. (B31.3, Par. 328.4.3(c) (3))

10.3 Tack Welding

Tack welding shall be done as followings :

(1) Avoid unreasonable set-up or other factors which would cause residual stress.

(2) Keep adequate root opening by using spacer, etc.

(3) Select welding rood of appropriate size for tack welding so as to fit the root opening.


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(4) Adopt dummy plate or start with backstep method when an arc is struck.

(5) Provide jigs (bridges or clamps)) in minimum number necessary for setting up. Use jigs (bridges or

clamps) made of material whose quality is the same as or better than base metal.

(6) Remove the jigs by grinder or gas cutting and, in case of gas cutting, cut it at upper part of its weld toe

and finish by grinder down to the surface of base metal. Jigs shall never be struck down by hammer

or plucked off.

10.4 Branch Connections

All branch attachment welds shall be of full penetration groove type. When the branch pipe is welded

directly to main pipe, welding shall be performed, unless otherwise specified, as shown in the

following figures.

NOTE These sketches show minimum acceptable welds.

Welds may be larger than those shown here.

Remarks:

1. Throat thickness "tc" shall be the lesser of 0.7 x "Tn" or 1/4 in. (6.4 mm).

2. The symbols used herein are as follows:

Th: nominal thickness of main pipe

Tb: nominal thickness of branch pipe

Tr: nominal thickness of reinforcement pad

3. At first, weld the part (a) and finish off the weld surface with grinder and then weld the part (b).


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4. Where reinforcement pad is necessary, it is indicated in the Piping Arrangement Drawing and

Notes for Piping Drawings.

5. If pads or saddles are used, a vent hole shall be provided at the side (not at the crotch) in the

ring or saddle to reveal leakage in the weld between branch and main run and to allow venting

during welding. Pads or saddles may be made in more than one piece if joints between pieces

have adequate strength and if each piece has a vent hole. A good fit shall be provided between

reinforcing pads or saddles and the parts to which they are attached.

6. Examination and any necessary repairs of the completed weld between branch and run shall be

made before adding reinforcing pads or saddles. (B31.3, Par. 328.5.4(h))

7. If reinforcement pads for branches should be made out of two segments, the segments shall be

welded in location away from the main pipe and the weld shall not run parallel to the main pipe's

axis.

8. Location of vent hole which is equipped in the reinforcement pad plate is shown is shown as

below;


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10.5 Half Coupling Join

Half coupling joint shall be welded as shown in the following figures:

10.6 Miscellaneous

(1) When welded pipe is used in horizontal line, the pipe shall be laid so that the longitudinal weld line

comes to upper side of the pipe (gas side). Arrangement of circumferential,

longitudinal and other (branch, support, etc.) weld lines shall be as shown in the following figures :


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Remarks : 1. L and L1 show the distance between both toes of bead.

2. L shall be the larger of three times of the pipe wall thickness or one outer diameter

of opening.

3. L1 shall be five times the pipe thickness or over.

(2) If fabrication aids such as temporary fixtures are removed after welding, the attachment locations on

the main pressure part shall be properly ground to eliminate surface stress risers.

11. PREHEATING AND HEAT TREATMENT

11.1 Pre-heating

(1) Preheating shall be performed by propane flame or by other appropriate method prior to commencing

the welding.

(2) Materials to be preheated and recommended preheating temperature shall be as follows :


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TABLE 11.1 - PREHEAT TEMPERATURES

Base Metal

P-Number

Weld Metal

Analysis

A-Number

Base Material

Group

Nominal Wall

Thickness,

(mm)

Minimum

Temperature

(°C)

1 1 Carbon Steel <25.4 10

Remarks :

1. The preheat temperature required according to the Welding Procedure Specifications shall be

checked by use of temperature-indicating crayons or other suitable methods to ensure that the

required preheat temperature is obtained prior to and maintained during the welding operation.

2. Heating width shall be three times the pipe wall thickness to each side from the bevel end. But it

is not necessary to exceed 100 mm.

11.2 Postweld Heat Treatment

No postweld heat treatment is required.

12. ASSEMBLY

12.1 Unless otherwise specified in the Drawings, valves shall normally be mounted with their stems upward

for horizontal line, to access way for vertical line.

12.2 Class designation and construction of each value as mounted in the piping system shall be as shown

in the Piping Arrangement Drawing, Piping Material Classifications and Piping Material Dimensions.

For all materials supplied, confirm that they are in conformity to the description of Piping Materials

Classification.


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12.3 Each fabricated component of piping shall be cleaned the inner surface and then both ends shall be

protected with suitable caps.

12.4 Valves shall be installed as closed after cleaning, and shall not be opened during installation of piping

systems.

12.5 In installing, flanged joints shall be fastened, after checking for the alignment of flange center and the

parallelness of flange face, so that the gasket contact faces bear force uniformly and then made up

with relatively uniform bolt stress.

12.6 Piping works shall be accurately performed in checking horizontal and vertical directions and mutual

distances between parallel pipelines, using level, plummet, etc.

12.7 When assembling flanged connections, the gasket and bolt nut, shall be give paste for prevention of

seizure, leakage, or adherence. Especially, asbestos sheet gasket be given paste amply.

Recommended pastes are as listed below :

Service of Piping Object Paste

air, steam, hot water

nitrogen, etc.

Joint sheet

gasket

VALQUA #5

oil, gasoline and other

solvents

Metal gasket

VALQUA #6

piping system of low

temperature

LOWTEN PASTE 100

piping system of 100 °C and

over

Bolt, Nut

SMOCON OR MOLY KOTE

piping system of below

100 °C

piping system of low

temperature

LOWTEN PASTE 100

Remark : VALQUA, LOWTEN, PASTE, SMOCON, AND MOLY KOTE are brand names.


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12.8 When works are done in the vicinity of piping made of, or lined with special materials such as plastic,

rubber, glass, etc., care shall be taken not to give them damage by fire, impact, etc.

12.9 All general aspects such as cleanliness and safety requirements as regard fabrication including

welding and cutting shall be ensured in accordance with standard and sound engineering practices, to

the satisfaction of PTTCHEM.

12.10

13. FLANGED JOINTS

13.1 Before bolting up, flange faces shall be aligned to the design plane to within 1/16 in./ft (0.5%)

maximum measured across any diameter; flange bolt (B31.3, par. 335.1.1(c))

13.2 Any damage to the gasket seating surface which would prevent gasket seating shall be repaired, or

the flange shall be replaced. (B31.3, Par. 335.2.1)

13.3 In assembling flanged joints, the gasket shall be uniformly compressed to the proper design loading.

(B31.3, Par. 335.2.2(a))

13.4 Bolts should extend completely through their nuts. Bolts that fail to do so are considered acceptably

engaged if the lack of complete thread engagement is not more than one thread. (B31.3, Par.

335.2.3)


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13.5 The bolt holes of flanges shall be located symmetrically from vertical center line in horizontal piping

line, and from plant north-south center line in vertical piping line, unless otherwise indicated in the

drawing.

Vertical Centerline Plant North-South Centerline

Horizontal Piping Vertical Piping

14. PROTECTIVE COATING AND WRAPPING

Protective coating and wrapping shall be in accordance with Engineering Spec. PTTCHEM-SP-P-121,

Protective Coating and Wrapping for Underground Steel Piping.

15. INSPECTION

15.1 General

(1) Safety requirements as regards testing and inspection including radiography shall be ensured

in accordance with standard and sound engineering practices to the satisfaction of

PTTCHEM.


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(2) PTTCHEM's final inspection shall be performed in accordance with PTTCHEM's drawings

and Engineering Specifications. Contractor shall not be released from his responsibility

before getting approval by PTTCHEM, even after the completion of the inspection.

(3) Prior to, during and after completion of the works, the tests and inspection as listed in Table

15.1 shall be performed by the Contractor.

TABLE 15.1

Stage Inspection and Test Check Points

(1) Prior to commenting work (a) Check of materials 1) Color Code, Material Designation,

Lot No. REQ. No.

(b) Welder's performance

qualification

1) Welder's performance qualification

certificates

(c) Welding procedure

qualification

(d) Welding rod 1) Brand name & size

(2) Prior to welding work (a) Edge preparation 1) Shape & dimensions

2) Cleanliness

(b) Shape of Pipe end 1) Out of roundness

2) Thickness

(c) Tack welding 1) Misalignment, Root opening

(d) Preheating 1) Method of preheating

2) Width of heating

3) Temperature measurement

4) Heating temperature

(e) Welding rod 1) Drying temperature

2) Drying time

3) Brand name & size


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Stage Inspection and Test Check Points

(3) During Welding (a) Welding condition 1) Welding parameters

2) Protecting measure for welding

3) Weather condition

(4) After completion of

welding work

(a) Visual examination 1) Inside surface misalignment, if

accessible

2) Outer surface misalignment

3) Inside surface weld protrusion, if

accessible

4) Wave irregularity

5) Uneven leg length

6) Irregular height of bead

7) Undercut

8) Overlap

9) Bead center shift

10) Height of reinforcement deposit

11) Throat thickness of fillet welds

(b) Non-destructive

examination

1) radiography (RT)

(5) During and after

completion of work

(a) Visual inspection

(6) After (a) Hydrostatic test

completion of work


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15.2 Non-Destructive Examination & Visual Examination of Welds

(1) Extent of Required Examination

The required weld examination shall be in accordance with Table-15.2.

TABLE 15.2

Type of weld Examined

Material Flange

Class

Type

Examination

Girth Butt

Weld

Branch

Weld

Socket

Weld

Attachment

Weld

Piping Class

Description

Carbon

Steel

150 Visual

RT

100%

2%

100%

-

100%

100%

-

150B13

150B03

Remarks : 1. Non-destructive examination is not required for the piping system designed for internal

pressure less than 1.0 kg/cm2g, such as vents, drains, etc.

2. Percentage figures indicated shall be the sampling of welds made by each welder. The entire

length of the selected welds shall be examined.


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(2) Radiographic Examination (RT)

(a) Method :

Radiography of welds shall be in accordance with ASME Code Sec. V, Article 2 and

the supplementary procedures described in Appendix-1.

(b) Acceptance criteria :

Limitations on imperfections in welds shall be as stated in ANSI/ASME B31.3, Par.

341.3.2 for the degree of service condition involved.

(c) Visual Examination

After completion of welding, all welds shall be visually inspected on the outside and

to the maximum extent possible also on the inside. The sequential execution of the

welding operations shall be such as to enable maximum possible extent of visual

inspection of the welds on the inside: for example, welding the pipe onto a socket

coupling only after the weld between the coupling and the main pipe has been

visually inspected on the inside for freedom from defects.

Followings shall be met, checking visually or in using measuring instrument.

(a) Inside surface misalignment : 1.5 mm or less

(b) Outside surface misalignment : 3.0 mm or less

(c) Under cut :

Undercut shall be finished smoothly with grinder or file not to leave any notch,

even when the value is within the limit. After finishing, the thickness of pipe

shall not be less than the minimum design thickness.

(d) Overlap : Grinding off


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15.3 Visual Inspection

Visual inspection shall be made for :

(1) Correction for jig mark

(2) Removal of spatter and slag

(3) Any harmful flaw on the flange face, inner and outer surface of pipe

(4) Shape and size of branches and other attachments shall comply with the Drawings.

16. PRESSURE TEST

16.1 GENERAL

(1) Prior to initial operation, each piping system shall be pressure tested to ensure tightness.

(B31.3, Par. 345.1)

(2) If any weld of a piping system remains concealed, gas leak test at test pressure equal to that

for a pneumatic test shall be conducted in lieu of hydrostatic test for the concealed weld.

(3) In case partial hydraulic pressure tests are applied for sections of underground piping,

connection points between the two parts (sections) may be checked using non-destructive

examination method, after obtaining approval by PTTCHEM.

16.2 Test Fluid

Hydrostatic testing shall be performed using clean water in general for all cases steels.

(1) If there is a possibility of damage due to freezing, or if the operating fluid or piping material

would be adversely affected by water, any other suitable liquid may be used.


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(2) If hydrostatic testing is not considered practicable, a pneumatic test maybe substituted, using

air or another nonflammable gas.

16.3 Test Preparation

(1) All joints, including welds, are to be left uninsulated and exposed for examination during the

test, except that joints previously hydro tested in accordance with the Code may be insulated

or covered.

(B31.3, Par. 345.3.1)

(2) Piping designed for vapor or gas shall be provided with additional temporary supports, if

necessary, to support the weight of the test liquid. (B31.3, Par. 345.3.2)

(3) Expansion joints shall be provided with temporary restraint if required for pressure load during

the test, or shall be isolated from the test. (B31.3, Par.345.3.3)

(4) Equipment which is not to be subjected to the pressure test shall be either disconnected from

the piping or isolated by blinds during the tests. A valve may be used provided the valve

(including its mechanism) is suitable for the test pressure. (B31.3, Par. 345.3.4)

(5) A flanged joint at which a blind plate is inserted to isolate other equipment during the test

need not be pressure tested.

(6) If a pressure test is to be maintained for a period of time and the test liquid in the system is

subject to thermal expansion, precautions shall be taken to avoid excessive pressure. (B31.3,

par. 345.2.1 (b))

(7) In case where the piping to be tested is connected to other piping in outside of battery limit,

the piping shall be isolated by blind plate or valve.


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(8) In case where orifice, control valve, positive displacement type of area type flow meter,

strainer, etc. are installed in the piping line to be tested, Contractor shall, prior to the test,

obtain instruction of PTTCHEM.

(9) When the test of piping system is to be carried out separately for each part divided at the

position of flanged joint, blind plate shall be inserted between the flanges. Minimum thickness

of such blind plates shall be as shown in Table 16.3.

(10) All piping and equipment shall be properly provided with vents to remove air completely when

filled with water. Provide vent and drain connections at the highest and lowest part of the line,

respectively. These connections may be closed with blind flange after completion of the test.

(11) At least two pressure gauges, having the range of 1.5 - 2 times the test pressure, shall be

provided, one of them being installed at the pump discharge. However, for piping within 1.0

m of length, one or more pressure gauge(s) shall be used.

Pressure gauges shall be installed at those high and low points as near as possible to the

highest and lowest of the piping to be tested, on order to prevent overstress in the piping.

(12) In case of piping with check valve, the source of pressure shall be located in the upstream of

the check valve. If this is not possible, check valve disc shall be removed or lifted up by lever

(the latter is in case of valve equipped with lever) before the test. If valve disc was removed,

it shall be confirmed, after completion of the test, that the disc was restored perfectly.

(13) A grip shall be fixed to outside of each blind plate to be used for the test, and shall be painted

in red to distinguish them from those for other use. A list of all blind plates and blind flanges

installed for the purpose of the test shall be made and , before start-up of the plant, it shall be

checked according to the list, whether such blind plates and blind flanges were removed

without fail.


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Table 16.3 Minimum thickness of blind plates for pressure testing unit : mm

Test

Pressure

Flange Size (B)

kg/

cm2

1-

1/2

2 3 4 6 8 10 12 14 16 18 20 24

7 1.6 2.3 3.0 3.2 5.0 6.0 7.5 8.5 9.5 10.5 12.0 13.0 15.5

14 2.3 2.6 4.5 5.0 7.0 8.5 10.5 12.0 13.0 15.0 17.0 18.5 21.5

21 3.2 3.2 5.0 6.0 8.5 10.5 12.5 15.0 16.0 18.5 20.5 22.5 26.5

28 3.2 4.0 6.0 7.0 9.5 12.0 14.5 17.0 18.5 21.0 23.5 26.0 30.5

35 4.0 4.5 6.5 7.5 11.0 13.5 16.5 19.0 20.5 23.5 26.5 29.0 34.5

42 4.0 4.5 7.0 8.5 12.0 15.0 18.0 21.0 22.5 26.0 29.0 31.5 37.5

49 4.5 5.0 7.5 9.0 12.5 19.0 19.0 22.5 24.5 28.0 31.5 34.5 40.5

56 5.0 5.5 8.5 9.5 13.5 17.0 20.5 24.0 26.0 29.5 33.5 36.5 43.5

63 5.0 5.5 9.0 10.0 14.5 18.0 21.5 25.5 27.5 31.5 35.5 39.0 46.0

70 6.0 7.0 10.5 12.0 17.5 21.5 26.5 31.0 33.5 38.5 43.0 47.0 56.0

77 6.5 7.0 11.0 13.0 18.5 23.0 27.5 32.5 35.0 40.0 45.5 49.5 58.5

84 6.5 7.5 11.5 13.5 19.0 24.0 29.0 34.0 36.5 42.0 47.0 51.5 61.0

91 7.0 8.0 12.0 14.0 20.0 25.0 30.0 35.0 38.0 43.5 49.0 53.5 63.5

98 7.0 8.0 12.5 14.5 20.0 26.0 31.0 36.5 39.5 45.5 51.0 56.0 66.0

105 7.5 8.5 13.0 15.0 21.5 27.0 32.5 38.0 41.0 47.0 53.0 58.0 68.5

112 7.5 8.5 13.5 15.5 22.0 27.5 33.5 39.0 42.5 48.5 54.5 59.5 70.5

119 8.0 9.0 14.0 16.0 22.5 28.5 34.5 40.0 43.5 50.0 56.0 61.5 73.0

126 8.0 9.0 14.0 16.5 23.5 29.5 35.5 41.5 45.0 51.5 58.0 63.5 75.0

133 8.5 9.5 14.5 17.0 24.0 30.0 36.5 42.5 46.0 53.0 59.5 65.0 77.0

140 8.5 9.5 15.0 17.0 24.5 31.0 37.0 43.5 47.0 54.0 61.0 66.5 79.0

175 9.5 11.0 16.5 19.0 27.5 34.5 41.5 48.5 53.0 60.5 68.0 74.5 88.0

210 10.5 12.0 18.0 21.0 30.0 38.0 45.5 53.5 58.0 66.0 74.5 81.5 96.5


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Remarks 1. In case where piping diameter is 1B or under,

Test Pressure (kg/cm2) Thickness of Blind Plate (mm)

40 or under 2.3

41 - 60 3.2

61 - 115 4.5

116 - 210 6.0

2. In case where piping diameter is 26B or over, following formula shall be applied to determine the

thickness of blind plate.

-

thickness of blind plate (t) mm = D ( 3P / 16SE )1/2

where,

D : Outer diameter of gasket (mm)

P : test pressure (kg/cm2)

SE : allowable stress (kg/cm2)

16.4 Hydrostatic Test

(1) The pump for pressure test shall be attended constantly during the test by suitable members

of operators.

(2) Procedures for hydrostatic pressure test shall be as follows.

(a) After filling the piping to be tested with water and purging air from there, the pressure

shall be increased gradually in the steps as shown in table 16.4, maintaining for at


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least 3 minutes in each step and no abnormal conditions such as leakage, etc. shall be

confirmed.

(b) After the pressure test, the pressure value shall be decreased down to max. operating

pressure x 1.1. Then welded joints shall be checked against leakage.

16.5 Test Pressure

The hydrostatic pressure at any point in the system shall be as shown in Piping Line Schedule.

16.6 Pressure Releasing and Draining

(1) After completion of the test, pressure shall be released by opening the valve gradually so as

not to endanger personnel or damage equipment.

16.7 Others

(1) Piping always open to atmosphere, such as vent pipe, drain pipe, outlet pipe of safety valve,

etc. are not tested.

16.8 Test Records

Records shall be made of each piping system during the testing period.


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17. PRESERVATION

17.1 Preservation with Full Water

After completion of the hydrostatic test, the piping shall be kept preservation with full water until water

flushing carries out, in order to prevent inside rust of piping.

Table 16.4

PRESSURIZING STEP AND HOLDING TIME OF HYDROSTATIC PRESSURE TEST

Steps Pressure(kg/c

m2g)

Pressurizing Method Measuring

Instrument

Holding Time

(minutes)

Step 1 2 by test pump, etc. Pressure gauge in each step : 3

at least press. : 30

Step 2 10 “ “ “

Step 3 20 “ “ “

Step 4 30 “ “ “

Step 5 40 “ “ “

Step 6 60 “ “ “

Step 7 100 “ “ “

Step 8 200 “ “ “

Step 9 300 “ “ “

Remarks: 1. Holding time may be extended if checking is not completed within the specified

holding time.


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2. The piping shall not be left at pressurized condition for a long period.

17.2 Curing

(1) Nozzle of aboveground shall be covered with metal sheet to prevent incoming dust.

(2) The red-colored protection box shall be placed to the following parts, in order to prevent

damage during construction.

- Valve stem of aboveground

- Nozzle of aboveground

- Cathodic protection cable of aboveground (lead to test box)


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18. FLUSHING

18.1 Flushing Method

Flushing shall be made by water flushing method.

18.2 General Requirements for Cleaning and Flushing

(1) Cleaning at Fabrication Work

(a) Vinyl caps or other end protections which cover ends of pipes shall not be removed

until the fabrication work is started.

(b) For valves, fittings and other parts, the same as above item (a) shall be observed.

(c) Inside surface of fabricated piping shall be made free from slag, scale and other foreign

matter, with grinder, chisel, wire brush, etc. After completion of cleaning, ends of the

piping shall be covered with caps until the installation in the field.

(2) Preparation for Flushing

(a) Following preparation works shall be carried out according to Flushing Plan.

1) Temporary piping work

2) Countermeasure for safety

3) Coordination procedure and assignment of man concerned

4) Prevention of pubic nuisance

5) Cooperation with operator

6) Judgment criteria of flushing

7) Treatment of piping accessories

8) Confirmation of support (slide or fix)


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(b) Support shall be attached to exhaust piping to prevent accident caused by the reaction

force during flushing.

18.3 Water Flushing

(1) Water for Flushing

As a rule, industrial water will be used.

(2) Degree of Water Flushing

Flushing shall be performed till the water becomes free from foreign materials, scale, etc.

This shall be decided by PTTCHEM upon observing turbidity of water taken out into beaker or

cup.

(3) Procedure for Water Flushing

(a) Water flushing shall be perform in the method of running by pressurized water, or rapid

draining with water filled.

(b) Where instruments are including in the piping system to be flushed, the instruments

shall, as a rule, be removed and spool pipe (distance piece) shall be inserted of the

instrument. When flushing is carried out in the condition with instrument. When

flushing is carried out in the condition with control valve connected, the procedure shall

be as follows.

1) Disconnect the companion flange at upstream side of the control valve and cover

opening of the control valve.

2) Flush the piping of upstream side.


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19. DOCUMENTATION

The records pertaining to all inspection and testing activities shall be diligently and meticulously

maintained by the Contractor.


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APPENDIX-1

SUPPLEMENTARY RT REQUIREMENTS

1. Personnel Qualification

Technicians who perform the radiographic inspection of welds must have the knowledge of method

and apparatus there of and, at the same time, the sufficient Technique and experience of taking and

processing of photograph. Those who make the judgment for non-destructive inspection shall be

those appointed by PTTCHEM.

2. Safety (Radiation Protection)

Prior to the radiographic examination, the scattering radiogractive ray around the area shall be

measured and the controlled area of the radioactive ray shall be established, providing the sufficient

countermeasure to prevent hazard of radioactive ray.

3. Recommended Identification System (Marking)

A permanent identification system is preferred to provide on the radiograph as follows :


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Where,

(a) Diameter of pipe (inch)

(b) Weld No. (Isome Dwg. No.)

(c) Thickness (mm)

(d) Put symbols A, B, C... in clockwise sequence, looking in the direction same as that of flow, starting

from the top (horizontal pipe) or the plant north (vertical pipe).

(e) In case of re-photographing, put symbol "R" which means re-inspection and for cut out is "C O"

(f) Date

(g) Welder No.

(h) Arrow mark

(i) A-lead marked tape

(j) Penetrameter

(k) Effective length mark (Location Markers)

(l) Contractors symbol mark

pttchem-sp-p-602-000 underground piping construction.pdf

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