instruction, operation and maintenance manual-turbine

g GE Oil & Gas Nuovo Pignone

03-09-E 110.2307/190.0531 P. 1-1

MOD. INPR/SVIL/ P.F. 01/01

INSTRUCTION, OPERATION AND MAINTENANCE MANUAL

(CENTRIFUGAL COMPRESSOR 3MCL 1805, STEAM TURBINE SAC 1-15)

Volume III Description & Operation – Steam Turbine

NUOVO PIGNONE JOBS : 110.2307/190.0531 N.P. SERIAL NUMBERS : C13422 - V01685

CUSTOMER : SAUDI POLYMERS COMPANY PLANT LOCATION : AL JUBAIL (SAUDI ARABIA) PLANT : UNIT 41 - ETHYLENE PLANT ITEM N° : 41K/KT14 MANUFACTURER : GE Oil & Gas Nuovo Pignone Via F. Matteucci, 2 50127 Florence - Italy Telephone (055) 423211 Telefax (055) 4232800

g GE Oil & Gas Volume III Nuovo Pignone

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STEAM TURBINE DESCRIPTION & OPERATION

MAIN INDEX

Contents Section - GENERAL 1

General Overall dimensions and main weights Design data Steam consumption diagram Steam turbine insulation Turbine data sheet

- SYSTEM DESCRIPTION 2

Steam turbine type SAC - Typical drawing Turbine type SAC - General description Simplified dwg and denomination SAC 1-15 Turbine casing: outer casing Inner casing H.P. Inner casing L.P. Guide blade carrier Packing gland Turbine rotor Blading Front bearing support Thrust bearing Journal bearing Rear support Bearing seal ring Control valves Governing system – General Control system - General Actuator Protective equipments Emergency stop valve Oil system – General Steam and condensate Piping systems for turbines Barring system


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Contents Section - SAFETY INSTRUCTIONS 3

Introduction Symbols used in the manual Definitions Intended use of a machine Identification of hazardous zones Acoustic enclosure access practice information Putting the machine in safe conditions prior to maintenance Lock-out and tag-out practice information Safeguarding (safety devices and guards) and stop devices Residual risks Generic residual risk Residual mechanical risk Risks during hoisting and handling operations Residual electrical risks Residual thermal risks Residual risks generated by noise Residual risks from materials and substances Description of symbols used for signaling residual risks, prohibition and obligation Information on hazards in case of failure General information of warning European Atex directive information Appendix A.1 Personal protection equipment (PPE) Appendix B.1 Classification, symbology and labeling of the products according to their features

- OPERATION 4 Foreword Preliminary safety check Stop devices General Setting-up dgm H.P. Steam flow diagram L.P. Steam flow diagram Start-up diagram Allowable power variation Variation in live steam temperature Steam purity


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NOTE

Contents Section

Protective compound and cleaning solvent 4 Turbine start-up Shut-down Operating oil pressure and temperature Condensate drains Control during operation Safety devices Checking during operation

- MAINTENANCE 5 Foreword General Servicing and testing schedule General washing instructions Turbine washing (condensing) Blade breakages Salt and silica deposits, their inhibition and removal Tools – Parts list Tools – Sketches

- DISMISSION AND ENVIRONMENTAL IMPACT 6 Environmental impact Dismission

For the parts “INSTALLATION“, ’’OIL CHARACTERISTICS’’, AND “PRESERVA-

TION” Refer to Volume I “DESCRIPTION & OPERATION - CENTRIFUGAL COM-PRESSOR”

g GE Oil & Gas Nuovo Pignone General Section 1

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GENERAL, SPECIFICATION AND DESCRIPTION

Contents Page - GENERAL 1-1 - OVERALL DIMENSIONS AND MAIN WEIGHTS 1-3 - DESIGN DATA 1-5 - STEAM CONSUMPTION DIAGRAM SOL 19491/4 - STEAM TURBINE INSULATION 1-6 - TURBINE DATA SHEET SOK 6757523/4

g GE Oil & Gas Nuovo Pignone General 1-1

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GENERAL The instructions contained in this manual are referred to a steam turbine that is part of a "Ammonia Synthesis unit". The instructions contained in this volume are referred to the steam turbine of type SAC 1-15 which drives a centrifugal compressors of type 3MCL 1805 by means of a coupling. The steam turbine and the centrifugal compressors are assembled in a common baseplate. At normal operation the live steam pressure of the turbine is 41.7 kg/cm² g. The arrangement of the machines is shown on the simplified drawing at the following page. The operation conditions of the steam turbine are shown in the following pages of this sec-tion. This volume of the instructions manual comprises: the description of the manufacturing features and the control, safety and monitoring equipments; the instructions of the opera-tion and maintenance; the description of the lube oil system; the instructions for the as-sembling/disassembling tools. The instructions of the "Auxiliary Equipment" and the "Instrumentation" supplied by Nuovo Pignone for this turbine are comprised in separated volumes of this manual. For the arrangement of the machines and for installation dimensions refer to "Machinery Foundation Loads & Notes" dwg. included in the Section 1, Volume II of this manual.


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Compression unit arrangement simplified drawing


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OVERALL DIMENSIONS AND MAIN WEIGHTS

For the overall dimensions see drawing at following page.

DENOMINATION WEIGHT

kg N

Turbine assembly SAC 1-15 145000 1421964.5

Rotor of turbine SAC 1-15 20000 196133

Compressor, 3MCL 1805 280000 2745862.6

Rotor, 3MCL 1805 23000 225553


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Compression unit arrangement simplified drawing


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TURBINE TYPE: SAC 1-15 JOB: 190.0531

TURBINE OPERATING DATA

(DESIGN DATA)

RATED POWER (A.P.I. POWER) kW 63607

MAXIMUM CONTINUOUS SPEED RPM 2939

LIVE STEAM PRESSURE

- NORMAL kg/cm² g 42.7

- MAXIMUM kg/cm² g 46

- MINIMUM kg/cm² g 41.7

LIVE STEAM TEMPERATURE

- NORMAL °C 390

- MAXIMUM °C 391

- MINIMUM °C 380

EXTRACTION PRESSURE - NORMAL kg/cm² g 15.7

EXHAUST PRESSURE

- NORMAL kg/cm² g 0.203

STEAM CONSUMPTION DIAGRAM SOL 19491


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STEAM TURBINE INSULATION The insulation consists in covering the turbine walls with partially overlapped quilts to avoid and direct contact with the environment. These quilts shall be fastened to each other by means of stainless steel wire hooks. Insulation execution The insulation concerns the whole turbine casing (excluding the discharge casing of K type-condensation turbine ), the control and emergency stop valves casing and the steam lines located over the baseplate. The balancing lines shall be insulated by means of zinc-plated rock wool. Particular care shall be paid in applying the insulating quilts that shall adhere perfectly without forming any air pocket.

Regarding flanges and tubes the insulation shall be applied according to their profile. The heads of all probes shall project from the insulation. When it is thick, tunnel-shaped comes from plate shall be provided. As for III Series Turbines (type: SC, SANC, SAC, SNC, SANC, SGC, SGDF) the tie rods connecting the outer casing and the front inner support shall be insulated by means of rock wool plait or the like. The insulation shall be applied at side after verifying that there is no leakage from the flanges. Quilts selection a) In the areas with live steam temperature < 450°C (840° F), quilts 60 mm. thick should be used. b) In the areas with live steam temperature > 450° C (840° F), quilts 90 mm. thick should be used.

g GE Oil & Gas Nuovo Pignone System description Section 2

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DESCRIPTION

TURBINE DESCRIPTION

Contents Page - STEAM TURBINE TYPE SAC - TYPICAL DRAWING 2-1 - TURBINE TYPE SAC - GENERAL DESCRIPTION 2-2 - SIMPLIFIED DWG AND DENOMINATION SAC 1-15 2-6 - TURBINE CASING: OUTER CASING 2-9 - INNER CASING 2-11 - TURBINE CASINGS: GUIDE BLADE CARRIER (H.P.) 2-12 INNER PACKING GLAND 2-13 - TURBINE CASINGS: GUIDE BLADE CARRIER (L.P.) 2-15 - PACKING GLAND 2-16 - TURBINE ROTOR 2-19 - BLADING 2-21 - FRONT BEARING SUPPORT 2-27 - THRUST BEARING 2-29 - JOURNAL BEARING 2-30 - REAR SUPPORT 2-32 - BEARING SEAL RING 2-34 - CONTROL VALVES H.P. 2-36 - CONTROL VALVES L.P. 2-38

g GE Oil & Gas Nuovo Pignone System description Section 2

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Contents Page - GOVERNING SYSTEM – GENERAL 2-40 - STEAM TURBINE CONTROL SYSTEM – GENERAL 2-41 - ACTUATOR (HYDRAULIC CYLINDER) 2-43 - SOLENOID VALVE FOR REMOTE TRIP 2-48 - EMERGENCY STOP VALVE 2-49 - OIL SUPPLY SYSTEM 2-53 - STEAM AND CONDENSATE/COOLING WATER – GENERAL 2-54 - GENERAL PIPING SYSTEMS 2-56 - BARRING SYSTEM 2-66

g GE Oil & Gas Nuovo Pignone System description 2-1

01-95-E SAC P. 1-1


6

5

2

3

4

1

STEAM TURBINE TYPE SAC TYPICAL DRAWING

1 ROTOR 2 OUTER CASING 3 FRONT SUPPORT 4 REAR SUPPORT 5 CONTROL VALVES ASSEMBLY 6 NOZZLES HOUSING CASING


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TURBINE GENERAL DESCRIPTION Type ranges SAC Design: turbine casings and guide blade carries Steam flows through the turbine is in the axial direction. After leaving the body of the emergency stop valve, the live steam enters the valve chest which the control valves which form an integral casting with the upper half of the outer casing. The valve chest is designed as a transverse tube with openings at both ends for as-sembly.

The turbine casing is divided into an admission and an exhaust section. Back-pressure as well as condensing turbines have admission sections of identical design. Depending on the initial steam conditions, the admission sections of comparable size are designed with cast-ing of different wall thickness. The admission section will be completed by an exhaust sec-tion of adequate size. Turbine of type ranges SAC have the exhaust section assembled to the admission section by bolts.

The turbine casing is horizontally split. The upper and lower casing halves are flanged and assembled by bolts. Inner casing

Turbine of type ranges SAC have an inner casing which is normally axially split, but may be of barrel type in some exception.

Owing to a virtually symmetrical design of the inner casing, all its cross sections show practically the same amount of thermal expansion.

Substantial thermal stresses in the inner casing need not be expected.

At the level of the shaft axis, the inner casing is supported on shims and is free to yield to thermal expansion. Eccentric guide pins in the upper and lower halves of the outer casing prevent lateral deviations of the inner casing.


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Similar eccentric elements between the inner and outer casing on the left and right side make an axial displacement impossible.

The inner casing is connected with the control-valve nozzle through steam-tight rings of L section which allow for thermal expansion.

The lower part of the inner casing incorporates two pressure-balancing areas for compen-sating the vertical downward thrust generated in the five nozzle chambers of the inner cas-ing.

Because lower initial-steam pressure and temperature the type ranges SAC are equipped, with either a nozzle block or a steam chamber, connected with the outer casing.

The nozzle block is designed as a half shell and is kinematically supported by outer casing. In the regulating stage, the corresponding lower half in the outer casing is designed as a simple blinding shield in order to avoid excessive windage losses. The nozzle groups are inserted into the nozzle block.

The nozzle block is connected with the steam chamber and serves also as guide for balance drum gland.

The guide blade carriers are inserted with a lathe-turned circumferential groove into corre-sponding webs of the outer casing. They are positioned in the lateral direction by eccentric guide pins and adjusted to the correct height by shims. Supports

In the turbine of type ranges SAC, the outer casing is supported by its brackets, on the front support and on the rear supports at the right and left side of the exhaust section, inde-pendently from the bearing housings.

The vertical position of the outer casing is determined by adjustable positioning elements located between the brackets and the supporting plane of the front and rear supports.

The clearance left between the underside of the assembly-bolt head and the bracket allows for both axial and lateral expansion of the outer casing with respect to the supports.


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The central position is ensured by guide ways in the bottom half of the casing. They leave the casing free to expand also in the vertical direction.

The fixed reference position of the casing is at rear-end support brackets. The casing is thus free to yield to thermal expansion by moving forward on special slide elements be-tween the front-end brackets and the front bearing support, or by moving forward of the front bearing support which slides on a special key.

The turbine rotor is supported in the bearing housing and is radially independent from the outer casing. The radial journal bearings are of the multi-wedge type (two or four oil wedges uniformly spaced on the circumference) or of the tilting pads type. The bearings are babbit-lined.

The correct axial position of the turbine rotor is ensured by a thrust bearing incorporated in the front bearing housing. It is intended also for taking up the residual axial thrust. For this reason it is designed as double-acting bearing of the segment type.

The tiltable bearing segments are likewise babbit-line. The heated rotor expands in the di-rection towards the exhaust casing. As the turbine casing with its fixed reference at the rear support expands into the opposite direction, the resulting differential expansion will be only small on condition that rotor and casing are heated to approximately the same tem-perature. Turbine rotor and blading

The turbine rotor is forged. Except for the control stage, the blading is of the reaction type. The running blades have their root, air foil and shroud milled from the solid forging.

Only exception to this rule are the twisted blades of the low-pressure and row of the con-densing turbine that are drop forged.

The running blades in the drum stages have roots of the intervented-T type. The roots of the control-stage blades and the roots of the condensing turbine types final stage blades are forked.

The guide blades are manufactured from drawn bar material and have pronged roots.


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Blade tip sealing and shaft glands Radial steps machined on the circumferential surfaces of both the stationary and moving blade rows together with oppositely situated sealing strips in the guide blade carrier and on the turbine rotor are forming labyrinth seals.

The points at which the shaft passes through the casing are likewise provided with laby-rinth seals. The shells of these glands are mounted in the outer casing in a manner which leaves them free to follow thermal expansion.

In the central portion of the gland, leak steam is drawn off to a region of lower pressure. This limits the amount of leak steam discharged into the atmosphere.

Turbine of condensing type turbines are designed for live-steam supply at this point in or-der to maintain an adequate vacuum. Governors and controls One or two emergency stop valves provided at the entrance of the turbine gives the initial steam access to the admission chest.

During normal operation, the stop valve is held open by oil pressure against the counter-acting force of a compression spring. In an emergency, pressure in the trip-oil circuits is suddenly relieved and the stop valve will close immediately.

The control valves of the turbine regulate the steam flow to the amount which is required for obtaining the desired output and/or speed. The H.P. control valves regulate the live steam flow; the L.P. control valves regulate the steam flow downstream the steam extrac-tion.

They are hydraulically actuated by servo oil. The control valves are adjustably suspended from a valve beam. By means of two spindles and via a lever system, the beam can be moved by the actuator which is mounted on the steam chest (s).

The control element serving as transmitter for the control impulses to the governor system is incorporated in the front bearing pedestal.


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DENOMINATION OF MAIN PARTS STEAM TURBINE SAC 1-10 (See simplified dwg. in the following pages) ITEM DENOMINATION 1 FRONT SUPPORT OUTER 2 OUTER CASING ASSEMBLY 3 EXHAUST CASING 4 H.P. CONTROL VALVES ASSEMBLY 5 M.P.1 CONTROL VALVE ASSEMBLY 6 M.P.2 CONTROL VALVE ASSEMBLY 7 EMERGENCY STOP VALVE ASSEMBLY 8 FRONT JOURNAL BEARING 9 REAR JOURNAL BEARING 10 AXIAL THRUST BEARING 11 ROTOR ASSEMBLY 12 H.P. INNER CASING 13 INTERMEDIATE STEAM SEAL RING 14 GUIDE BLADES CARRIER ASSEMBLY H.P. 15 GUIDE BLADES CARRIER ASSEMBLY H.P. 16 GUIDE BLADES CARRIER ASSEMBLY H.P. 17 GUIDE BLADES CARRIER ASSEMBLY L.P. 18 FRONT STEAM SEAL RING OUTER 19 REAR STEAM SEAL RING OUTER 20 SUPPORT FOR FRONT PICK-UP 21 SUPPORT FOR REAR PICK-UP


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SAC 1-15 STEAM TURBINE LONGITUDINAL SECTION SIMPLIFIED DRAWING


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SAC 1-15 STEAM TURBINE TRANSVERSAL SECTION SIMPLIFIED DRAWING


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TURBINE CASING: OUTER CASING

The following subassemblies are accommodated in the outer casing: Inner casing, H.P., diffuser holding ring, inner casing L.P., guide blade carrier L.P. and sealing glands.

The outer casing is composed of a front, intermediate, and rear section. Those sections are integrally cast (HP plus intermediate), or assembled by screws.

The mentioned designs offer the possibility of employing different materials for the rear sections.

In addition, the outer casing is divided up into several portions, which can be designed for different pressures. In each portion the pressure compartment is limited by webs into which the different types of inner casing or guide vane carriers are inserted.

Through an appropriate combination of guide-vane carriers of varying length and by a con-formable design of the blading, it becomes possible to adapt the steam pressure in the indi-vidual compartments to a given set of live and exhaust steam conditions and thus to meet the requirements with regard to extraction pressures.

The outer casing is axially split in two halves. The H.P. top part rests with its brackets on the forward casing support. while the bottom part is assembled to the top part at the flanged joint by screw and studs. The exhaust section bottom part rests with its brackets on the rear supports, while the top part is assembled to the bottom part at the flanged joint by screw and studs.


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1 Bore for control-valve spindle 2 Buttress lug for Inner casing L.P. position-fixing device 3 Exhaust section 4 Web carrying rear sealing gland 5 Ledge supporting rear bearing housing 6 Rear casing guide 7 Hole for flanges screws 8 Web accomandating Inner casing L.P. 9 Front casing bracket 10 Web carrying front sealing gland 11 Live-steam intake 12 Control-valve seats

Fig. 1 - Turbine casing: Outer casing


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INNER CASING The nozzles chamber, divided in two halves, along the horizontal center plane, contains the nozzle groups and supports the packing gland around the balance drum. It serves for guiding the steam flow from the control valve nozzles into the wheel cham-ber. The nozzles chamber is assembled in the outer casing. Eccentric guide arranged between nozzles chamber and outer casing at bottom, as well as shims (plates) under the right and left side of nozzles chamber bottom halve serve as radial adjustment. It is inserted with its circumferential groove into a corresponding supporting web of the outer casing; the web assures also axial position.


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TURBINE CASINGS: GUIDE BLADE CARRIER H.P. The guide blade carrier accommodates the guide vanes of the turbine blading. It is inserted with its circumferential groove into a corresponding supporting web of the outer casing. The web is used also for axial positioning. The guide blade carriers are adjusted to the cor-rect height by appropriate thickness which are placed upon the mounting lugs as shown in Detail A-A of this dwg. Eccentric guide pin(s) projecting from the lower half of the outer casing permits the align-ment in radial direction and serves also for locking the carrier against rotation.


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INNER TURBINE CASINGS: INNER PACKING GLAND With extraction turbines, the inner packing gland serve as a seal between two consecutive range of expansion. The pressure differential existing between the two expansion ranges is being used, in addi-tion, for balancing the axial thrust exerted on the blading by the steam forces. For this rea-son, the bore of the packing gland, in which the sealing are accommodate, has been de-signed with a diameter which corresponds to the amount of thrust that has to be compen-sated. The inner packing gland is composed by a support ring and a seal ring. The supporting is horizontally split to form two half-rings assembled by screws and dow-els. It is inserted with its circumferential groove into a corresponding supporting web of the outer casing. The web is used also for axial positioning. The supporting is adjusted to the correct height by appropriate supporting keys placed at the right and left sides of the lower half-ring, near the horizontally split, and is aligned in the lateral direction by a centering pin that serves also for locking the support ring against rotation. The seal ring is horizontally split and is inserted with its supporting web into a correspond-ing circumferential groove of the support ring. Two locking screws lock the upper half of the seal ring to the upper half of the support ring. The two screws permit the raising of the upper half of the support ring and the upper half of the seal ring as one piece and prevent the rotation of the seal ring. Sealing strips are caulked into appropriate grooves of the seal ring by means of caulking material. Together with the appropriate profile of the rotor surface, the series of sealing strips of the seal ring form a contact-free seal.


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Inner packing gland - Simplified dgm.


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TURBINE CASINGS: GUIDE BLADE CARRIER (L.P.) The guide blade carrier (L.P.) accommodates the guide vanes of the turbine blading. It is inserted with its circumferential groove into a corresponding supporting web of the outer casing. The web is used for axial positioning. The guide blade carrier is adjusted to the correct height by appropriate shims which are placed upon the mounting lugs shown in detail A-A of this dwg. Adjusted spacers and setting screws help to maintain the correct height by locking the guide blade carrier to the upper half of the outer casing (Detail B-B).


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PACKING GLAND Purpose The packing gland shell carries on the periphery of its inner surface caulked-in sealing strips which, together with the edges of corresponding sealing strips or comb-like projec-tions on the rotor shaft, are forming a seal without mechanical contact between the moving rotor and the stationary turbine casing.

Such series connection of consecutive sealing edges constitutes a seal of the labyrinth type which acts on the principle of transforming potential energy (pressure) into kinetic energy (velocity of flow) and subsequently dissipating the kinetic energy by the formation of ed-dies.

With sealing devices, which have no mechanical contact with the rotating member, a slight flow of leakage steam has to be accepted. Fig. 1 - Packing gland: rotor shaft with caulked-in sealing strips Fig. 2 - Packing gland: rotor shaft with comblike projections Design The shell of the packing gland is axially split into two half-shells. It is effectively locked against rotation in the turbine housing and against displacement of the half-shells with re-spect to each other.

The sealing strips of stainless steel have been caulked into grooves on the periphery of the inner shell surface by means of a special tool with square cross section.


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Packing for sealing against positive pressure With packing glands intended for sealing against a higher pressure prevailing in the turbine casing, the major part of the leak-steam flow will be exhausted from the middle section of the gland shell.

Only a very small part of the leak -steam flow is thus allowed to penetrate into the collect-ing groove provided at the downstream end of the gland from where it will escape via the gland-steam stack into the atmosphere.

A disc-shaped small annular fin on the shaft, which extends into the collecting groove, as-pirates air by centrifugal action from the atmospheric end of the packing gland and delivers it into the gland-steam stack.

This is an effective means for preventing the sealing steam, which may be leaking out of the packing gland, from blowing against adjacent bearing sections and heating them up. Packing glands for sealing against negative pressure

Packing glands intended for sealing against negative pressure reigning in the turbine casing have to block the penetration of air into the casing.

The respective passage of the packing gland, instead of serving for sucking off leak steam will be connected to a steam supply of slight positive pressure.

The flow of this sealing steam will be split into two parts. One part of the steam goes into the turbine casing, the other to the gland-steam stack from where, together with air, to the steam gland condenser.


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1 Casing 2 Gland bush 3 Caulking material 4 Packing ring 5 Turbine shaft

This dwg is valid only for type HG

Fig. 3 - Design of the packing gland Condensate drain Condensate accumulating in those passages of the packing gland, where the gland steam is flowing, will be effectively drained through a hole drilled at the lowest point of the gland.


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TURBINE ROTOR (Single-Flow Condensing Turbine) Design The turbine rotor consists of three principal portions: Front portion (3 to 6), blading portion (7 to 9), and rear portion (10 to 14). Function The blading of the turbine converts the thermal energy into mechanical energy which by the moving blades provide rotor movement. Construction Fig. 1 show the rotor of the SC turbine and the special feature which can be incorporated. The rotor is a single forged piece together with the control stage wheels (7) and thrust bearing collar (3). The rotor is supported in two pressure lubrificated journal bearings (4 and 11). After the front journal bearing come the strips for the outer gland bush (5) and the inner bush (6). The main balancing planes are located in front of the inner gland bush, after the final row of moving blades, and between the two (16). In addition there are secondary balancing planes in front of the outer gland bush (17).


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3 Thrust-bearing collar 4 Contact surface of front radial bearing 5 Outer front packing-gland section 6 Inner front packing-gland section 7 Impulse wheel blade rim of regulating stage 8 Drum-blading section 8A H.P.-blading section 9 L.P.-blading section 10 Rear packing-gland section 11 Contact surface of rear radial bearing 14 Coupling-flange cone 16 Main balancing plane 17 Supplementary front balancing planes

Fig. 1 - Turbine Rotor - Typical drawing


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BLADING GENERAL The turbine blades convert the thermal energy of the steam into mechanical power. The blading is thus of primary importance for the efficiency and operational reliability of the machine, and no effort is spared in determining the most favorable profile and in pro-viding for the necessary mechanical strength, accuracy of manufacture and surface quality. All the inserted blades of the regulating and reaction stages are designed in such a way that frequency tuning is not required since the shrouds are located close together and thus pro-duce an effective damping effect which prevents vibration of detrimental amplitude.

Fig. 1 - Section of a bladed rotor


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For this purpose the twisted low-pressure blades are provided with damping wires of steel or titanium (Fig. 1). Stainless steel is employed for the entire blading. Regulating stage Turbines designed for regulating the steam flow through nozzle groups are provided with a regulating stage, with impulse blading allowing partial admission. The regulating stage is missing in the case of turbines with throttle control, the steam being admitted direct with full admission to the first expansion stage through the control valves. Two forms of blades for the regulating stage Blade root with single fork Blade root with multiple fork

Fig. 2 Reaction stages The reaction stages following the regulating stage are designed for 50% reaction. The guide blades and rotor blades have the same profile and blade angle.


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Fig. 3 - Rotor blade

Fig. 4 - Group of guide blades


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Rotor blades The inverted-T-root rotor blades with shrouding (Fig. 3) are milled from solid material and are the bottom-caulked with brass after insertion in the shaft groove. The roots are so designed that-after assembly the specified blade spacing is obtained with-out the need of fitting spacers. A locking blade, which is secured to the rotor by means of threaded dowels, closed off the bladig gate without forming a gap. Guide blades The guide blades are manufactured from drawn bar material. They have a pronged root, the correct inter-blade spacing being obtained by means of spacers fitted in the blade groove. The shrouding is riveted and combines several guide blades into a group. Low-pressure stages The last two or three stages of the L.P. turbines are combined in groups with standard-size blades. The sizes of these blades are so selected that-whatever the number of turbine flows-a permissible axial velocity in the end stage and thus an economical leaving loss are obtained for any volume flow. The difference between the circumferential velocity at the blade root and tip is quite con-siderable and is taken into account by twisting the blade along its length. The rotor-blade roots take the form of fork-type or T-shape, are inserted in the radial grooves of the rotor and are secured by taper dowels or bottom-caulking. The trailing edges are machined to a thin profile to avoid any stall patches and the forma-tion of large water drops. The axial clearance from the last row of rotor blades is kept large to facilitate atomizing of water drops released from the leaving edges and to provide for a sufficiently long accelera-tion path for any droplets remaining. The impact velocity of the water drops impinging on the leading edges of the blades is thus reduced.


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Fig. 5 - L.P. stage with T-root blades

Fig. 6 - L.P. stage with fork-root blades


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Tip sealing In case of turbines with a 50% reaction component, a pressure gradient is produced both at the guide and rotor blades. The pressure difference generates a flow in the gap between the stationary and rotating components, and losses are thus caused. To keep these leakage losses low, effective blade-tip sealing has to be provided. Cylindrical blades (guide and rotor blades) are therefore provided with continuous shroud-ing strips with radial recesses which form an effective labyrinth seal together with the seal-ing strips (Fig. 7).

Fig. 7 - Blade - tip seals The shroud strip of rotor blades is formed by abutting strip sections which are milled from the solid together with the blades. The guide blades are fitted with riveted shroud strips. The shroud strips which are caulked into the guide-blade carrier or shaft opposite to the shrouds are made of a stainless steel. They are designed to accommodate the maximum pressure difference occurring. On the other hand, the heat produced in the event of contact occurring at the sealing tips and transferred to the guide-blade carrier or shaft remains low enough to prevent deformation of these components. The sealing strips can be replaced easily. Replacement of sealing strips which may have worn down as a result of rubbing and correction of the clearances may be carried out dur-ing a routine inspection without great difficulty.


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FRONT BEARING SUPPORT Function The front support serves both for supporting the turbine shaft by a journal bearing and a thrust bearing, and for sustaining the turbine casing. Design The front bearing support is split in an horizontal plane. Its lower parts is attached to the turbine baseplate by screws. Spacing washer under the heads of the fastening screws pro-vide for a clearance. The holes (9) in the bearing support, through which screws are in-serted, have been machined as elongated holes. 2 Opening for emergency tripping device

4 Supporting web of journal bearing

6 Oil inlet to journal bearing

7 Keyway for sliding key of support plate

8 Oil drain

9 Elongated hole for bearing pedestal mounting screw

10 Oil inlet to thrust bearing

11 Tapped hole for turbine-casing fastening screw

12 Supporting web of thrust bearing

13 Flange for emergency speed governor adjustment

Fig. 1 - Front bearing support


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These oblong give the bearing support freedom to follow the axial expansion of the turbine casing under the thermal stress while transversal displacement of the support is prevented by an axially extending key sliding in the keyway (7). At the points where the turbine shaft penetrates the bearing, the oil flow is sealed off by a bearing seal ring. Flange connections (6, 8, 10) serve for attaching oil inlet and drain pipes. Attachments The upper part of the support is provided with bored holes intended for the attachment of the emergency tripping device (2) as well as of several monitoring devices, such as ther-moelements and vibration pickups. Two openings (13) which are ordinarily blanked off by a blind flange, serve for adjusting the emergency speed governor.


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THRUST BEARING Purpose The thrust bearing takes up the residual axial thrust forces of the turbine that have not been compensated yet by the labyrinth-sealed balance drum (piston) and also any thrust forces possibly transferred through the gear-tooth coupling and transmits these forces to the front-bearing housing.

The magnitude of the axial forces thus exerted on the thrust bearing is determined chiefly by the turbine load. In addition, the thrust bearing serves the purpose of fixing the rotor in its axial position with respect to the turbine housing.

For complete details see the drawing and instructions included in "Auxiliary Equipment" Volume.


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JOURNAL BEARING

Typical dwg

The journal bearings have the function to support the turbine rotor, they are mounted on each inner support (or bearing housing).

The journal bearings are of the tilting pad type with forced lubrication. Oil under pressure reaches the bearings radially, goes through holes to lubricate pads and blocks. It is laterally discharged.

Bearings pads (A) are of steel, internally lined with white metal. They are integral with blocks of steel (B), and are located into the proper seat formed by the shell (C) and by two oil guard rings (F).


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The pads can swing inside the shell both in the direction of the movement and in the axial direction for maximum dampening of radial vibration of the rotor. The rotation of pads inside the shell is prevented by pins protruding from screws (D) screwed in the shell. The shell (C) is made of steel and is divided into two halves along the horizontal center plane. Both halves containing the blocks and pads, are positioned with pins and then fixed together with bolts. The rotation of the bearing inside its housing is prevented by a pin installed between the support and the lower half of the shell.


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REAR SUPPORT (Condensing turbine) Function The rear support elements - bearing housing and support brackets of the exhaust casing, rear inner bearing support, support plates - serve for supporting the turbine casing and the turbine rotor and for their alignment relative to each other.

Design

Turbine casing is supported at the rear side, by means of the exhaust casing support brack-ets. The brackets are attached to the turbine baseplate by screws.

Spacing washer under the heads of the fastening screws provide for a clearance. The holes in the brackets are larger than the fastening screws diameter to permit the thermal expan-sion of the exhaust casing.

The support plates assembled between the support brackets and the baseplate held a key sliding in the keyway machined under the support brackets. That is the rear fixed point of the turbine casing, relative to which the turbine casing expands towards the front end.

The rear inner bearing support is attached to the exhaust casing by stud-bolts and is aligned vertically and longitudinal by adjusting elements. It is transversely aligned by the casing guide situated below the lower half.

The rear inner bearing support is split in an horizontal plane. It houses the rear journal bearing supporting the turbine rotor. Towards the turbine the bearing support is sealed by the oil seal ring.

The upper part is provided with the opening for the attachment of the electrohydraulic and manual barring gear as well as instrumentation.


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1 Seating surface for journal bearing

2 Flange for vapour duct

3 Exhaust casing

4 Baseplate

5 Oil inlet

6 Bearing casing

7 Casing guide

Fig. 1 - Rear support: condensing turbine


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BEARING SEAL RING (FRONT) Purpose The bearing seal ring has the function of sealing the bearing housing against the turbine casing at the point where the rotor shaft penetrates the casing. Design The bearing seal ring is axially split. It is fixed to the bearing housing (1) and is thus in its axial position. At the point where the rotor shaft passes out from the casing, the bearing seal ring carries caulked-in seal strips (4). Together with a knife edge (9) on the surface of the rotor shaft (5), which has a profile fitting into a recess of the bearing seal ring, the seal strips prevent seepage of lubricating oil to the outside. The additional provision in the lower bearing-seal-ring half (6) of radially drilled holes (7) emanating from the interspace between adjacent seal strips, allows possibly accumulated lubricating oil to flow back into the bearing housing. Annular heat shields (2) are mounted on the outer face of the bearing seal ring in order to protect the bearing housing against excessive heat transfer. 1 Bearing housing 2 Heat protection shield 3 Bearing seal ring, upper half 4 Seal strips 5 Turbine rotor 6 Bearing seal ring, lower half 7 Oil drain holes 8 Journal bearing 9 Sealing edge

Fig. 1 - Bearing seal ring


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BEARING SEAL RING (REAR) Purpose The bearing seal ring has the function of sealing the bearing housing against the turbine casing at the point where the rotor shaft penetrates the casing. Design The bearing seal ring is axially split. It is fixed to the bearing housing (1) and is thus in its axial position. At the point where the rotor shaft passes out from the casing, the bearing seal ring carries caulked-in seal strips (4). Together with a knife edge (9) on the surface of the rotor shaft (5), which has a profile fitting into a recess of the bearing seal ring, the seal strips prevent seepage of lubricating oil to the outside. The additional provision in the lower bearing-seal-ring half (6) of radially drilled holes (7) emanating from the interspace between adjacent seal strips, allows possibly accumulated lubricating oil to flow back into the bearing housing. Annular heat shields (2) are mounted on the outer face of the bearing seal ring in order to protect the bearing housing against excessive heat transfer. 1 Bearing housing 2 Heat protection shield 3 Bearing seal ring, upper half 4 Seal strips 5 Turbine rotor 6 Bearing seal ring, lower half 7 Oil drain holes 8 Journal bearing 9 Sealing edge

Fig. 1 - Bearing seal ring


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CONTROL VALVES H.P.

Purpose

By regulated opening of the control valves the steam flow can be adjusted to the desired turbine output. In conformity with the output requirements, the different sectional admis-sion areas of the valves have to be opened to a larger or smaller degree.

The valve seats have been designed in the form of venturi nozzles in order to keep fluid losses to a minimum.

Design

The valve cones (6) are freely suspended in a valve beam (5) which is accommodated in the valve chest (3). The valve beam is connected with a lever (1) via two valve spindles (4) and flexibly jointed links (3).

The lever, which is operated by an actuator (9), is at the same time subjected to the action of a helical compression spring (8). The entire valve actuating mechanism is movably at-tached to a console (7) which is flange-mounted on the valve chest.

Mode of operation

As long as the turbine remains at standstill, the valve cones are being pressed down upon their seats by the joint forces of the compression spring and of the steam pressure prevail-ing at the upstream side of the valve chest.

Upon arrival of an appropriate control impulse from the governor, the actuator is going to pull the longer arm of the lever downwards so that the valve beam will be lifted by the valve spindles. The loosely suspended cones of the individual valves will thus be opened in succession according to the predetermined sequence.


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1 Lever 2 Link 3 Valve chest 4 Valve spindle 5 Valve beam 6 Valve cone 7 Console 8 Compression spring 9 Actuator

Fig. 1 - Control valve operating mechanism


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CONTROL VALVES L.P. Purpose Regulated opening or closing of the control valves allows matching of the steam flow to the desired turbine output. This will be done by successively opening flow passages of ap-propriate cross section to the steam. The valve seats (11) have been designed as venturi type diffuser in order to reduce the hy-drodynamic losses to a minimum Design The valve cones (10) are loosely suspended from a valve beam (8) which is accommodated in the valve chest (12). The valve beam is connected to the levers (2 and 4) by means of two valve spindles (7) and freely articulated shackles. The one of the levers (2) is moved by an actuator (15). This lever, is at the same time under the action of one compression spring (1) which has always the tendency to keep the control valves closed. A bracket (14) is flange-mounted to the valve chest (12) and carries the actuator (15) which is attached to the bracket by a flexible mount. Mode of operation As long as the turbine is at standstill, the force of the compression spring will be pressing the valve cones upon their seats. As soon as the actuator receives a valve-opening signal from the turbine governor (secondary-oil pressure), the actuator will pull the lever down-wards so that the valve spindles with the valve beam are lifted. The loosely suspended individual valves are thus allowed to open in the pre-determined order. The sequence and amount of that opening can be adjusted by spacer bushes of vari-ous height which are inserted into the valve beam.


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1. Compression spring 2. Lever 3. Shackle link 4. Lever 5. Shackle link 6. Shackle link 7. Valve spindle 8. Valve beam 9. Steam inlet 10. Valve cone 11. Valve seat 12. Valve chest 13. Valve spindle 14. Bracket 15. Actuator

Fig. 1 - Control valve operating mechanism


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GOVERNING SYSTEM GENERAL The SAC 1-15 steam turbine governing system is composed by the following parts: 1. Turbine speed governor and governor-electronic control system. 2. Current to hydraulic pressure converter - (For H.P. control valves). 3. Current to hydraulic pressure converter - (For L.P. control valves). 4. Hydraulic cylinder and actuator for H.P. control valves. 5. Hydraulic cylinder and actuator for L.P. control valves. 6. H.P. control valves. 7. L.P. control valves. The instructions proper of the Electronic governor are included in the proper volume. For further details of the overmentioned equipments see the relative para. of this section.


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STEAM TURBINE CONTROL SYSTEM - GENERAL

Refer to simplified dgm. included in this para. and to "Control oil" dgm SOS 8628237/1 (sheet 1/2) included in the Section 5, volume II of this manual.

The control oil is supplied by the lube oil system. It flows to the H.P. control valve actua-tors, and to the testing valve of the emergency stop valves.

If the solenoid valves 41XY50317, 41XY50318, 41XY50314, 41XY50315 in the trip oil line are energized and the emergency trip device gear is resetted, the control oil flows to the one current to hydraulic pressure converters, to the trip oil entrance (under the piston disk) of the emergency stop valves and to the control valves actuator.

The control oil will operate in the overmentioned equipments as shown in the relative para. of this manual.

The steam turbine speed is controlled by an electronic governor complete with two current to hydraulic pressure converters.

The electronic governor receives input signals from the speed pick-ups assembled on the turbine and from the panels, according to a predetermined logical process.

The electronic governor sends output signals to the current to hydraulic pressure converter which convert the received signals into modulated hydraulic signals corresponding to opening or closing the H.P. control valves in order to obtain the required speed and turbine output.

The operating instructions of the control system are included in the "Operation" section of this volume.


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Control oil simplified dgm - Refer to proper drawing SOS 8628237/1 (sheet 1/2) included in the “Drawings”

Section 5 Volume II of this manual.

5 H.P. CONTROL VALVES 2 EMERGENCY STOP VALVES 6 L.P. CONTROL VALVES ACTUATOR 3 EMERGENCY STOP VALVES TEST 7 L.P. CONTROL VALVES 4 H.P. CONTROL VALVES ACTUATOR 8 EMERGENCY TRIP VALVE (SOLENOID) 9 STARTING SOLENOID VALVE


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ACTUATOR (Hydraulic cylinder) Purpose The actuator serves for transmitting the positioning impulses for the control valves to the valve-operating leverage. The lever system lifts or lowers the control valves of the turbine in such a way that the steam flow will always be adequate to the preset or required turbine output. 1 Eyebolt joint head 2 Reset bar 3 Piston rod 4 Servo cylinder 5 Servo piston 6 Connection piece 7 Pilot sleeve 8 Pilot piston 9 Pilot valve 10 Lever 11 Adjusting screw 12 Bell-crack follower 13 Pressure roller

Fig. 1 - Actuator


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The pilot valve of the actuator receives its control impulses from the secondary oil circuit.

However, the actual servo power for positioning the control valves is derived from the pressure of the oil which flows either to the top or to the underside of the actuator piston.

Design

The principal parts of the actuator are the pilot valve (9) with pilot piston (8), the connec-tion piece (6), the servo cylinder (4) with servo piston (5) and piston rod (3), and the reset-ting mechanism.

The piston rod carries the reset bar (2) and the eyebolt joint head (1) for connecting the ac-tuator with the lever system of the control valves.

Several sleeves (7), in which the pilot piston (8) slides, are fitted tightly into the pilot valve housing. The pilot valve has on its periphery turned annular grooves which coincide with corresponding oil pockets in the bore of the sleeves (7).

The top end of the pilot carries a wheel disk (16) with evenly spaced passages drilled in radial and tangential direction.

The upper side of the wheel disk has in its center a pivot pin which engages with an axial thrust bearing (15).

The bearing is under the action of a compression spring (14) situated on its top. The pre-load of the spring is determined by the respective positions of a lever (10) and an adjusting screw (11).


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14 Compression spring 15 Axial thrust bearing 16 Wheel disk 17 Slide piston 18 Secondary oil 19 Oil drain 20 Drain hole 21 Set screw for vibration 22 Small drilled hole 23 Pressure oil 24 Set screw for rotation 25 Drilled radial hole 26 Aluminum insert 27 Drilled radial passage Fig. 2 - Pilot valve (servo cylinder)

Mode of operation Any change in secondary-oil pressure brings about a corresponding stroke of the pilot pis-ton. The annular grooves and oil pockets in the pilot and sleeves, respectively, are arranged in such a manner, that with increasing secondary-oil pressure the pilot piston is moved up-wards thus opening the pressure oil arriving at connection (23) a channel for flowing to the upperside of the servo piston. By its resulting downward stroke, the piston is thus opening the control valves through the lever system. By means of a reset bar (2) the piston stroke is fed back to the lever (10) via a bellcrank follower (12). The action of that lever on the compression spring goes in a direction opposite to the pilot piston stroke. Hence, the pilot piston (8) is going to yield to the spring force and returns to its neutral position. The functional relationship between secondary-oil pressure and piston stroke can be changed by adjusting the inclination of the reset bar to the desired position with the help of a set screw.


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Such adjustments will affect only the amount of proportional gain while, with the design of reset bar here under consideration, the secondary-oil pressure vs. piston stroke relationship will always remain a linear function. However, in cases where control requirements warrant it, it will be possible to provide also for non linear control characteristics through an appropriately shaped cam profile of the re-set bar. The resetting mechanism serves for stabilizing the control action. The functional chain ex-tends between the piston rod (3) and the pilot piston (8); these parts are interconnected by the bell-crank follower and the lever (10). The pressure roller (13) carried by one arm of the bell-crank follower (12) is pressed the reset bar (2). The other arm of the follower is connected with the lever (10) and, through the adjusting screw (11), it transmits its motion to the compression spring (14).

Fig. 3 - Oil flow through wheel disc


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ROTATION AND VIBRATION OF VALVE PISTON Pressure oil entering at pipe connection (23) arrives through drilled passages in the hous-ing of pilot valve (9) to the upper part of pilot piston (8). From there, it flows through four radial holes (25) into cavity of the hollow pilot piston where it has access to the drilled ra-dial and tangential passages (27) of wheel disc (46) from which it escapes. The permanent flow of the oil leaving the wheel disk in tangential direction imparts a con-tinuous rotational motion to the pilot piston. The set screw (24) allows adjustment of the rate of turning by either increasing or reducing the volume of the oil flow. The speed rate can be measured by means of a special device which is located in the aluminum insert (26). The secondary-oil pressure acting on its underside imparts to the pilot valve additionally an alternation motion also in axial direction. This is achieved by a small hole drilled into the lower part of the pilot piston. During every complete revolution of the piston, this hole will momentarily overlap with a drain hole (20) in the housing. The quantity of secondary oil, which thus is allowed to espace causes a small pressure drop in the secondary-oil circuit with the result that the pilot piston is moved downwards by a small amount. When the drilled hole is obturated once more through further turning of the pilot piston, the piston will be lifted again until the overlap position of the next cycle is reached. During each of these momentary strokes of the pilot piston, a minute volume of pressure oil is given access to the servo piston (5). This causes slight vibration of the servo piston and, consequently, also of the control-valve spindles, thereby ensuring immediate response of these components to the control impulses of the governor. The stroke amplitude of pilot piston vibration can likewise be adjusted by means of the set screw (21).


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PROTECTIVE EQUIPMENTS SOLENOID VALVE FOR REMOTE TRIP The solenoid valve (s) is (are) intended for installation in the pressure oil circuit to the automatic emergency trip gear (trip-oil), and to the emergency stop valve (s) (starting oil). When operated, they will interrupt the oil flow in these lines. At the same time, the trip-oil circuit and the starting oil circuit will be connected to the oil drain whereby emergency tripping is released. The solenoid valves are remote controlled electrically, i.e. they can be operated either from the control room or by a protection device. For details of manufacture and operation features of the solenoid valves see the manufac-turer’s instruction in the ”Instrumentation” volume.


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EMERGENCY STOP VALVE Purpose The emergency stop valve is the main shut-off organ between the steam network and the turbine. It can off the steam supply to the turbine in a minimum of time, which is of par-ticular importance in the event of a fault. Design The emergency stop valve consists basically of a steam section and a hydraulic section which are joined by a bonnet (5) which is flanged to the side of the valve chest admission section of the turbine, thus sealing off the steam section. Most of the steam forces acting on the bonnet are transferred directly to the admission sec-tion of the turbine. 1 Main valve cone 8 Piston disc D Steam inlet 2 Relief cone 9 Spring cap E Trip oil 3 Steam strainer 10 Piston F Start-up oil 4 Guide bush 11 Compression spring H Test oil 5 Valve bonnet 12 Test piston K Leakage steam 6 Labyrinth bush 13 Pressure-gauge connection T1 Drain oil 7 Valve spindle 14 Hand valve T2 Leakage oil

Fig. 1 - Section through the emergency stop valve


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The valve spindle (7) is located in the bonnet in two guide bushes (4). The steam-side end of the valve spindle is a relief cone (2) and is mounted on the main cone (1) with an inter-ference fit. The other end of the valve spindle carries the piston disc (8). The valve spindle penetration is effectively sealed by the guide and labyrinth bushes. The steam-side guide bush is also provided with a sealing edge. With the emergency stop valve open, the steam pressure acting in the direction of the hy-draulic section forces the valve cone with its specially provided backseat against this edge to from a steam-tight seal. In this way, leakage steam cannot escape via the labyrinth bushes while the emergency stop valve is open, At the same time, this ensures that as long as the valve is open, the valve cone will not rotate. Any leakage steam arising while the valve is closed is led away into a leakage-steam line (K) located near the rear guide bush. The hydraulic section, which is also bolted to the connection part, is the active component of the emergency stop valve. It is a piston consisting of two parts, one disc-shaped, one bell-shaped. The disc-shaped section is fixed to the valve spindle while the bell-shaped section moves in a surrounding cylinder. A compression spring (11) which acts at one end on the inside of the bell-shaped part and at the other on the valve spindle via a spring cap (9) provides the connection between the two piston parts. The two parts are pressed against each other when trip oil (start-up oil F) acts on the bell-shaped pushing it towards the disc. Mode of operation: hydraulic section The emergency stop valve is opened hydraulically by oil and closed by spring action. The opening operation s initiated by starting device. For this purpose, trip oil (start-up oil F) flows into the space behind the piston. As it overcomes the action of the spring, the piston moves in the direction of the spring cap and is eventually pressed against the cap to form a seal. Controlled by the starting device, the trip oil pressure E now builds up ahead of the piston disc.


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While the oil pressure increases, here the oil pressure behind the piston will be slowly de-creasing. This causes the piston disc and the piston to move jointly to their ultimate posi-tion in front of the test piston, thereby opening the valve. Whenever a tripping operation is released, the trip oil circuit and thus also the space ahead of the piston disc become depressurized and the valve is immediately closed by the com-pression spring. Any remaining trip oil flows into the valve compartment and from there into the drain line T1, provided it has not already flowed back into the supply line. During the process, the piston remains in its ultimate position. Mode of operation: steam section The steam D1, after the inlet flange and the steam strainer (3), flows through holes in the main cone (1), to the relief cone (2). When the piston in the hydraulic section moves the valve spindle towards the open posi-tion, the relief cone is the first lifted from the cone. The force required to open the emergency stop valve is thereby considerably reduced. Testing device A testing device is provided to allow the proper functioning of the emergency stop valve to be checked even during normal turbine operation. The principal components of the device are test piston (12) in the hydraulic section, a pres-sure oil connection H with a mini-valve, and a connection (13) for the test pressure gauge for observing the test pressure. If the mini-valve is opened, pressure oil will be admitted to the space behind the test posi-tion which will then be pushed against the piston (10) and will move the piston and the valve spindle towards the closed position.


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Test pressure

The test pressure P1 required for the above checking operation must be red on the pressure gauge (22) at the first start-up of the turbine. After that recorded pressure, at every check, will be red on the pressure gauge the actual test pressure P2. If the test pressure P2 is in ex-cess of the permissible test pressure P1 this will be indicative for deposits of salt or oil car-bon having formed on the valve spindle or piston rod, respectively.

In order to restore the smooth condition of the spindle surfaces, the test must be repeated a number of times. If this fails to reduce the actually required test pressure P2 to the permissible test pressure P1 value, the emergency stop valve has to be disassembled for clearing the defect.


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OIL SUPPLY SYSTEM GENERAL The oil is supplied to the steam turbine by the lube oil console (supplied by N.P. Job 110.2307/190.0531) common to the compressor. The elements which form said console are described in the compressor instruction volume, section “Lube oil” and on dwg. SOS 8628231/1 (sheet 1/1) and SOS 8628232/1 (sheet 1/1) included in the "Compressor Drawings" volume of this manual. The oil that reaches the turbine is conveyed to assure the bearing efficiency, lubricating them, and to circulate in the hydraulic mechanism required for the turbine control and safety. This oil must be always under pressure, moreover two pressure levels shall be considered one related to the control oil pressure and the other, which is lower, related to the bearing pressure. The control oil pressure shall be of 9 kg/cm2 g The lube oil pressure to journal bearing shall be of 1.5 and 2.5 kg/cm2 g

The lube oil pressure to thrust bearing shall be of 1.5 kg/cm2 g It is to be noted that the absolute compliance with these pressures is not imperative to guar-antes the good operation of the oil system it is necessary that, once these pressures are reaches, they do not vary noticeably as long at the turbine speed remains constant. Slightly pressure variations can be due to temperature variations.


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STEAM AND CONDENSATE COOLING WATER General Refer to a simplified diagram in the following page and to steam condenser dgm. SOS 8628250/1 (sheet 1/1) included in the Section 5, Volume II of this manual. The live steam flows through two steam strainers assembled to the body of the emergency stop valves and then through the H.P. control valve, actuated by means of the "Turbine control system". At the end of the medium pressure section a part of the steam flow through the valves for the extraction utilities and the other part flows through the L.P. control valves in the low pressure section of the turbine than discharges into the main condenser. The extraction steam flow is controlled downstream of the hydraulic operated check valve. The turbine control system controls the steam flow, as a predetermined logical process, to meet there guired turbine out put and the preseetted extraction steam pressure. The control system is equipped by a gland condenser but the main condenser is not supplied by Nuovo Pignone.


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Steam simplified dgm.

Refer to proper drawing SOS 8628250/1 (sheet 1/1) included in the “Drawings” Section 5, Volume II of this manual.


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PIPING SYSTEMS FOR TURBINES General

The purpose of these recommendations is to explain the requirements stipulated for the piping by the turbine manufacturer in order to ensure satisfactory operation of the turbine.

Special attention is drawn to the fact that all moments and forces exerted on the turbine by the piping must be kept as small as possible to safeguard the stability of the machine.

These forces and moments should be calculated by the designers and manufactures of the piping and submitted to the turbine manufacturer for checking and approval.

Permissible force and moment values at inlet and discharge flanges of the turbine are shown on the dwg. "Machinery Assembly and Foundations" included in the Volume II of this manual.

It is desirable to ensure as early as the design stage that steam and oil lines are spaced it is recommended that the steam pipes be provided with splash guards to protect them against any dripping oil.

Initial steam, backpressure and extraction lines Stop valves and fittings The stop valves and fittings in the steam lines should be located as close as possible to the turbine to permit the greatest possible length of piping to be warmed up. The remaining piping up to the turbine is warmed up when the turbine is started up.

A turbine will be corroded by steam seeping into the casing when it is not in operation. Therefore the stop valves and fittings in the steam lines must be capable of sealing the line tightly to prevent this. Three possible methods of sealing the lines are given below:

- Valve with vented body (Fig. 1)

This form of valve has two disks with the space between them being vented and drained when the valves are closed. It should be possible to operate the stop valves and the venting and drain valves from the turbine house floor.


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1 Inlet steam 2 Vent 3 Drain 4 Drain 5 Exhaust steam 6 Vent 7 Drain 8 Drain

Fig. 1 - Valve with vented body - Fitting two standard stop valves (Fig. 2)

In this case the closed section between the two valves must be vented and drained.

It is not necessary for the two valves to be directly adjacent to one another. If one valve is located close to the turbine the other can be at some distance on a header. However, there must be no other steam connections within this closed section. 1 Inlet steam 2 Vent 3 Drain 4 Drain 5 Exhaust steam 6 Vent 7 Drain 8 Drain

Fig. 2 - Fitting of two stop valves


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- Fitting blank flanges (Fig. 3)

The blank flanges are fitted in the pipelines after the machine has been shut down. This method is normally only used when a turbine which usually runs continuously in discon-nected from the steam system for a long inspection period. 1 Inlet steam 2 Blank flange 3 Drain 4 Blank flange 5 Exhaust steam 6 Drain

Fig. 3 - Fitting of blank flanges 1 Removable pipe section 2 Steam system 3 Drain 4 Turbine

Fig. 4 - Piping configuration with inlet or exhaust branches at top of turbine


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Inlet and exhaust branches on top of turbine (Fig. 4) Steam inlet and exhaust branches located on top of the turbine should have provision for easy removal. This is necessary for inspection of the turbine. Care should also be taken that the whole steam piping system does not drain back into the turbine. The piping must be drained separately since water in the turbine could cause se-vere damage. An additional drain should be fitted to the exhaust line close to the turbine, particularly for condensing turbines, to reduce the flow of water through the exhaust casing as much as possible. Extraction stop valves (Fig. 5-6) These valves must be arranged as close as possible to the turbine so that the steam in the system up to the valve is insufficient to cause overspeeding of the turbine after a full-load trip when the extraction stop valves close. The piping between valve and turbine should also be sufficiently flexibly mounted to prevent the piping exerting any force on the tur-bine. The extraction valves are normally suspended so that they are free to move horizon-tally in all directions. 1 Handwheel pedestal 2 Operating floor 3 Hangar 4 Extraction stop valve

Fig. 5 - Extraction stop valve suspension permitting horizontal movement in all directions


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1 Handwheel pedestal 2 Operating floor 3 Flexible pipe hanger 4 Extraction stop valve 5 Handwheel pedestal support 6 Clearance to suit pipe movement

Fig. 6 - Extraction stop valve suspension permitting horizontal and vertical movement in directions

If vertical movement of the extraction valve is also necessary because of the pipe move-ment (e.g. with large size pipes), the handwheel pedestal must be mounted on the valve body, thus being supported by the pipe. THE NECESSARY FLEXIBLE HANGERS OR MOUNTINGS FOR THE PIPING SYSTEM (INCLUDING EXTRACTION VALVE) ARE NOT PART OF THE SUPPLY.

Washing connections After long periods in operation salt or silicate deposit mast build up in the turbine depend-ing on the purity of the steam. In this case the machine must be washed with wet steam to which certain chemicals, depending on the type of deposit involved, can be added. There-fore, it is advisable to make allowance for these connections at the planning stage. It is necessary to fit an inlet stub complete with stop valve and blank flange (nominal size 40 to 80 mm depending on the size of the turboset) in the initial steam line between the stop valve and the turbine inlet branch. The condensate from the washing steam is passed through the normal drains. A DRAIN SHOULD BE FITTED BETWEEN THE WASHING CONNECTION AND THE TURBINE TO PERMIT EXCESS WASHING WATER TO BE DIVERTED BEFORE REACHING THE TURBINE.

NOTE

NOTE


07-91-E 1-51-00-01-220 P. 6-10


1 Inlet steam 2 Drain 3 Exhaust steam 4 Drain 5 Washing connection 6 Blank flange

Fig. 7 - Washing connections Air-drying connection (Fig. 8) If a turbine is to be dried out with warm air preparation for a long stationary period, a nominal size NW 80 connecting stub should be fitted in the backpressure line between the machine and the stop valve. The vents fitted on the turbine should be opened to allow the air to escape. 1 Air vent 2 Drying air 3 Blank flange 4 Exhaust steam

Fig. 8 - Air-drying connection


07-91-E 1-51-00-01-220 P. 7-10


Drains When fitting drains the following should be noted: - Drain lines must not bypass any stop valves or fittings, particularly those related to

the emergency stop system. - Neither water nor low temperature steam must be able to enter the turbine through

the drains. The runs of the drain lines are determined on size to fit in with the plant layout. The drain valves must always be easily accessible.

The minimum nominal size of the drains should be NW 15. Drain lines which are also used to warm through pipelines and the turbine should be NW 40 minimum size. Backpressure turbine drains The drain lines should be led to a drain channel or an atmospheric drain tank. Condensing turbine drains The drains from all spaces which are under vacuum during start-up must be led to the con-denser.

It is recommended, however, that the drains are not led direct to the condenser but to a standpipe arranged adjacent to it. At the top the standpipe should be connected to the steam space and at the bottom to the hotwell of the condenser. The hot drains may thus flash out here without endangering the condenser tubes. 1 Drains 2 Standpipe 3 Condenser 4 Maximum water level 5 Hotwell 6 Minimum distance of 250 mm 7 Drain manifold

Fig. 9 - Example of drain connections at condenser


07-91-E 1-51-00-01-220 P. 8-10


The inlet of the drains to the standpipe must be a minimum of 250 mm above the max. wa-ter level in the condenser.

THE DRAINS SHOULD BE CONNECTED TO THE DRAIN MANIFOLD IN THE COR-RECT ORDER, I.E. THE DRAINS FROM H.P. SPACE MUST BE FURTHEST FROM THE CONDENSER AND THE DRAINS FROM THE L.P. SPACES NEAREST TO IT. THIS WILL PREVENT THE H.P. DRAIN RESTRICTING THE FLOW OF THE L.P. DRAINS.

The pipelines leading to the turbine main steam stop valve should be drained to atmos-phere or to an atmospheric tank.

For turbines with top exhaust as already described above. It should be mentioned once again, however, that the turbine drains must be led with a constant far to a vacuum vessel.

Since with turbines of this design the condenser is usually mounted adjacent to the turbine, or above it if air is used as the condensing medium, care must be taken to see that con-denser hotwell is arranged sufficiently low down to permit easy flow in the drains.

If this arrangement cannot be achieved then the drains must be led to a separate vessel at the required level and the condensate pumped into the condenser. Miscellaneous

It must be possible to drain and vent all pipelines. Suitable connections must be fitted at both the high points and low points of all pipelines for the purpose.

It is also recommended to provide mounting channels of the foundation and turbine house ceiling to ensure adequate support of the pipelines. They should be planned and installed by the building contractor.

The following temperatures should be taken as the permitted local temperatures when de-signing the foundation and deck reinforcement:

- Foundation, exterior + 20°C - 68°F

- Foundation, opening under h.p. turbine + 70°C - 158°F

- Foundation, opening under l.p. turbine + 60°C - 140°F

- Foundation, opening under generator + 40°C - 104°F

NOTE


07-91-E 1-51-00-01-220 P. 9-10


Fig. 10 - Pipe hanger mountings

If hot pipelines runnings in close proximity to the foundation are likely to cause the tem-peratures given above to be exceeded, lagging must be applied to the foundation as protec-tion.

The final decision on the type of foundation lagging is the responsibility of the building contractor based on details of the maximum temperatures of the pipes outside the lagging supplied by the pipe installation firm.

1 Metal plate 2 Insulating slab 3 Foundation 4 Foundation bolt 5 Spacing sleeve

Fig. 11 - Example of foundation lagging


07-91-E 1-51-00-01-220 P. 10-10


In the case of turbines with high steam temperatures our erection drawing indicates where foundation lagging is recommended.

After completion or repairs, the steam lines must be carefully cleaned and blown out with high-velocity steam.

The temperature of the steam used must be varied during the process. Final cleanliness of the line is checked by holding a copper sheet in front of the outlet from the blow-out line.

There must be no appreciable marks made on the sheet by particles being ejected from the pipe.

If the ambient temperature of a turbine can fall below 0°C the following lines should be provided with trace heating:

- Lines which may freeze (e.g. drain lines, measuring lines).

- Oil lines in which the oil may become too sluggish (e.g. control oil lines).

Trace heating systems are not included in our scope of delivery. The should be suited to local conditions.


10-91-E 1-72-00-01-000 P. 1-4


BARRING SYSTEM (see typical drawing attached here to) The rotor barring system consists of two barring gears (ratchet), one actuated by hand, the other electrohydraulically.

The barring gear is used to rotate the turbine shaft during preheating and cooldown of the machine.

Under said conditions the rotor, if not rotated cyclically, can suffer more or less strong strains (depending on changes in temperature as well as on the duration of said conditions), such as to cause scores against the stator parts of turbine during its startup.

The barring system is designed to avoid these troubles, allowing turbine to be started up without any danger.

The two barring gears (manual and electrohydraulic) are arranged on the rear support cover (in the "G" backpressure turbines) or the rear bearing cap (in the "K" condensing steam turbines).

MANUAL BARRING GEAR Description and operation

The main components of the manual barring gear are: the gear wheel (18), mounted on the turbine shaft, the catch (7) and the gear lever (4).

The barring gear will be actuated being sure that the rotor has fully stopped; then take off the safety cover (6), after loosening the nuts (8) holding it fastened to the support cover (or bearing cap), and raise the latch (9) of the catch (7).

Put an extension into the gear lever (4) and rotate it in the same direction of rotation of tur-bine; the lever (4), swinging around the pin (5), makes the catch (7) engage with one tooth of the gear wheel (18) thus setting the rotor to rotation.

Once barring has finished, bring lever (4) back to its stop position and lock it again with the latch (9); then put the safety cover (6) on barring gear. NEVER REMOVE THE SAFETY COVER WHILE THE TURBINE IS IN OPERATION. SAFETY HAZARD

! DANGER


10-91-E 1-72-00-01-000 P. 2-4


ELECTROHYDRAULIC BARRING GEAR Description and operation The electrohydraulic barring gear shall operate only after turbine stop; should it work be-fore the rotor has completely stopped, serious damages would affect the barring system.

The electrohydraulic barring gear is switched on by a key-switch, while the permission to work is given by a tachometer mounted on the machine thus assuring that the barring gear operates only with rotor fully stopped.

The electrohydraulic barring gear is stopped by the key-switch.

To assure that catch (15) is on down-position (gear not engaged), the oil pump will auto-matically stop in over 15 seconds, after the barring gear has been switched off.

Besides, for further safety, a proximity switch (13) detecting the position of the catch (15) is mounted on the barring gear, giving the permission to start up the turbine only when the catch (15) is on down-position.

The cyclic operation of the barring gear is assured by a panel-mounted timer sending cur-rent to the solenoid, three-way valve (1) which actuates the directional valve (2) pneumati-cally; in such a way the control piston (19) will be pushed to its farthest right, so that the pressurized oil can flow through the groove (B) under the piston (11); than it will be pushed up along with the rod (17) and catch (15).

When catch (15) goes up, the pin (16) on it engages with one tooth of the gear wheel (18) making the rotor rotate by a determined angle.

When piston (11) reaches its top point, the timer deenergizes the solenoid valve (1) which vents the pneumatic signal formerly sent to the directional valve (2), to the atmosphere.

In consequence, the compression spring (20) of the directional valve puts the control piston (19) back to its farthest left, the pressurized oil (P) flows through the groove (A) onto the piston (11) pushing down the barring gear catch (15).


03-09-E 1-72-00-01-000-190.0531 P. 3-4


Electrohydraulic barring gear 1 Solenoid valve 7 Catch 13 Proximity switch 2 Directional valve 8 Nuts 14 Hinge pin 3 Support plate 9 Latch 15 Catch 4 Gear lever 10 Cylinder 16 Pin 5 Pin 11 Piston 17 Piston rod 6 Safety cover 12 Spring 18 Gear wheel

A Oil on the piston B Oil under the piston P Oil inlet T Oil discharge


10-91-E 1-72-00-01-000 P. 4-4


Functional diagram showing mode of operation of directional valve 19 Control piston 20 Compression spring 21 By-pass Pressure oil A Oil on the piston B Oil under the piston Oil P Oil inlet discharge T Oil discharge

g GE Oil & Gas Nuovo Pignone Safety instructions Section 3

03-09-E 190.0531 P. 1-1


SAFETY INSTRUCTIONS Contents Page - STEAM TURBINE SOM 6607109/4

SAFETY INSTRUCTIONS 1. SAFETY INSTRUCTIONS 521

1.1 INTRODUCTION 521 1.2 SYMBOLS USED IN THE MANUAL 523 1.3 DEFINITIONS 524 1.4 INTENDED USE OF A MACHINE 527 1.5 IDENTIFICATION OF HAZARDOUS ZONES 530 1.6 ACOUSTIC ENCLOSURE ACCESS PRACTICE INFORMATION 532 1.7 PUTTING THE MACHINE IS SAFE CONDITIONS PRIOR TO MAINTENANCE 537 1.8 LOCK-OUT AND TAG-OUT PRACTICE INFORMATION 539 1.9 SAFEGUARDING (SAFETY DEVICES AND GUARDS) AND STOP DEVICES 543 1.10 RESIDUAL RISKS 546

1.10.1 Generic residual risk 546 1.10.2 Residual mechanical risk 550 1.10.3 Risks during hoisting and handling operations 552 1.10.4 Residual electrical risks 554 1.10.5 Residual thermal risks 557 1.10.6 Residual risks generated by noise 558 1.10.7 Residual risks from materials and substances 559 1.10.8 Description of symbols used for signaling residual risks, prohibition and obligation 561

1.11 INFORMATION ON HAZARDS IN CASE OF FAILURE 564 1.12 GENERAL INFORMATION OF WARNING 565 1.13 EUROPEAN ATEX DIRECTIVE INFORMATION 568

APPENDIX 574

A.1 PERSONAL PROTECTION EQUIPMENT (PPE) 574 B.1 CLASSIFICATION, SYMBOLOGY AND LABELING OF THE PRODUCTS ACCORDING TO THEIR FEATURES 594

g GE Oil & Gas Nuovo Pignone Operation Section 4

03-09-E 190.0531 P. 1-2


OPERATION

GENERAL

Contents Page - FOREWORD 4-1 - PRELIMINARY SAFETY CHECK 4-2 - STOP DEVICES 4-3 - GENERAL - SETTING-UP DGM - SOL 07853/4 - H.P. STEAM FLOW DIAGRAM - SOL 07851/3 - L.P. STEAM FLOW DIAGRAM - SOL 07852/3 - START-UP DIAGRAM - SOL 19686/4 - ALLOWABLE POWER VARIATION 4-6 - VARIATION IN LIVE STEAM TEMPERATURE 4-9 - STEAM PURITY 4-10 - PROTECTIVE COMPOUND AND CLEANING SOLVENT 4-12 - TURBINE START-UP 4-18 - SHUT-DOWN 4-22 - OPERATING OIL PRESSURE AND TEMPERATURE 4-23 - CONDENSATE DRAINS 4-24

g GE Oil & Gas Nuovo Pignone Operation Section 4

03-09-E 190.0531 P. 2-2


Contents Page - CONTROL DURING OPERATION 4-26 - SAFETY DEVICES 4-29 - CHECKING DURING OPERATION 4-30

g GE Oil & Gas Nuovo Pignone Operation 4-1

06-89-E 03-00-00-S P. 1-1


OPERATION FOREWORD THE PERSONNEL ENTRUSTED WITH THE INSTALLATION, OPE-RATION AND MAINTENANCE OF NUOVO PIGNONE PRODUCTS SHALL HAVE THE NECESSARY TECHNICAL CHARACTERISTICS AND SUITABLE TECHNICAL TRAINING FOR THE TASK IT HAS TO ACCOMPLISH. THESE TECHNICAL CHARACTERISTICS SHALL BE IN COMPLIANCE WITH INTERNATIONAL STANDARD CLASSIFICATION OF OCCUPATIONS, GROUPS 9-61 AND 9-69. ANY DAMAGE, EVEN PARTIAL, ASCRIBABLE TO FAILURE TO COMPLY WITH AFORESAID ESSENTIAL CHARACTERISTICS SHALL BE ATTRIB-UTABLE TO THE PURCHASER AND NUOVO PIGNONE WILL BE DIS-CHARGED OF ANY LIABILITY AND INDEMNIFICATION THEREOF. These instructions describe a detailed procedure for the operation of the machine.

Since the instructions do not provide for every possible contingency to be met in connec-tion with operation, slight different procedures can be used.

Regardless of the procedure used only qualified and experienced personnel shall be en-trusted with this task.

ANY INJURY OR DAMAGE RESULTING FROM OFF DESIGN OR IMPROPER OPERATION, NEGLIGENT PROCEDURE AND MAINTENANCE DEFICIENCY OR EFFECT OF CORROSION, EROSION, DEPOSIT OF SCALE AND WEAR AND TEAR ARE EXCLUDED FROM NUOVO PIGNONE WARRANTY.

! WARNING

! WARNING


03-09-E 190.0531 P. 1-1


PRELIMINARY SAFETY CHECK Before performing any operation, a general check of safety conditions must be carried out; such inspection must follow instructions given herein after Any actual or potential risk must be removed, before any operation. Preliminary inspection must be carried out as follows : - Learn all special emergency procedures concerning each system. - Note the location and learn the operation of the fire fighting system and of any other

emergency or protection appliance. - Note dangerous areas for escape of gases, acid gases, condense collection, drainage line,

high voltage, high pressure, other predictable risks. - Ensure the appliance and the adjacent area are in good conditions, and without obstacles

and that vent lines are not obstructed. - Check if other personnel is operating in the area and if their work is so dangerous to

preclude the operation of the compressor.


03-09-E 190.0531 P. 1-1


STOP DEVICES The appliance is fitted with four types of stop devices: - Work cycle stop device: it is controlled through a PLC for stopping the compressor, and keeping all auxiliary

circuits electrically supplied. - Work shift end stop device: it is operated when the appliance must be completely dumped, before a period of inac-

tivity. - Emergency stop device: it is operated in emergency conditions, from an emergency control which immediately

cuts out electric supply, and keeps software controls operational. Emergency stop can also be activated by pressing the stop pushbutton.

- «Trip» stop device: it is automatically activated through the control software each time an anomalous opera-

tion of the compressor is detected.


11-89-E 3-01-00-01-220 P. 1-2


GENERAL - Delivery of the equipment - Unpacking of the equipment - Storage of the equipment - Turbine operating personnel Delivery of the equipment The machines after testing at the factory are inspected, cleaned and the internals and ex-posed parts coated with a protective oil. Care is taken to ensure safe transit to its place of installation where the machines are shipped completely assembled. Unpacking of the equipment Before unpacking the equipment it is recommended that adequate measure for storage are taken. It is recommended that shipment damages are checked. Any damage should immediately be reported to both the carrier and the supplier. Storage of the equipment If the equipment received is not to be installed at once it should be carefully stored pref-erable in a weather-tight building or enclosure.


11-89-E 3-01-00-01-220 P. 2-2


Only by strict adherence to the values laid down in the test report of first commissioning and by observance of the supplemental instructions following hereafter, can permanently satisfactory and troublefree operation of the turbine be ensured while taking into account the particular requirements inherent to its design. Turbine operating personnel

The turbine personnel must keep a written record of all readings and checks it is going to carry out during the period of service. Particular attention should be given to any irregular-ity and to all repair work which has to be performed on the turbine during the period of ac-tual operation.

The hours of starting and shutting down, as well any intervals of non-operation, should likewise be recorded.

However, in addition to keeping a written record on these data, it is indispensable to check the measured values continuously against the values laid down in the test report of first commissioning, as this is the only sound way for deciding whether the observed deviations are admissible or not. In the latter case, the machine operator in charge should immediately take the measures required for re-establishing normal operating conditions. If he feels that the encountered situation is unfamiliar or that he will not be able to control it, he must in-form his superior without any delay.

However, before taking measures of greater consequence, the measuring device in question should previously be checked for proper functioning and consistency with the calibrated quantities.

THE OPERATION DATA NOT AUTOMATICALLY RECORDED BY INSTRUMENTS SHALL BE INDICATED IN THE LOG DATA SHEET. ALL DATA RECORDED BY THE INSTRUMENTS OR STATED IN THE LOG SHEET BY THE OPERATOR ARE OF NO USE IF THEY ARE NOT COMPARED WITH THE DATA PREVIOUSLY READ AND IF IMMEDIATE STEPS, WHEN NECESSARY, ARE NOT TAKEN.

IMPROVEMENT OF OPERATION RELIABILITY SHOULD BE ACHIEVED BY SPE-CIFIC TRAINING OF THE USER'S PERSONNEL WHO SHOULD ATTEND TRAINING COURSES AT NUOVO PIGNONE'S OR AT USER'S SHOP HOLD BY NUOVO PIGNONE SPECIALISTS.

NOTE

NOTE


09-90-E 3-02-11-01-220m P. 1-3


ALLOWABLE POWER VARIATION

For the proper running of the machine, in event of an increase in power under constant live steam conditions, the diagram n. 1 (included in the following page) has to be adhered to strictly. The diagram is based upon the evidence that the former operating conditions were stationary.

There is the possibility of determining the max. percent power to which the unit can be brought from any stationary operating condition. This range is obtainable from the initial percent power, by moving horizontally till the auxiliary curve is met and going up again to the limit curve.

Should it become necessary for the machine to be brought from the initial percent power value to a greater one than the instantaneous, a D T* time lag will be required while chang-ing from the latter percent value to that desired.

The necessary D T* is obtained taking the difference between the intersection abscissas of the desired power value and the initial power, with the limit curve and auxiliary curve re-spectively. For instance

When running on 35 percent of max. power and intending to reach 90 percent, the rise to 73 percent of max. power will be instantaneous, after which a D T* time lag (as the prod-uct of the difference between TB time lag and TA) will necessary to get the desired power value.

For decreasing the power, the diagram n. 2 (included at the end of this para.) is to be fol-lowed, bearing in mind the above-mentioned diagram n.1.

When running on 70 percent of max. power and intending to decrease down to 20 percent, the drop to 43 percent of max. power will be instantaneous, after which a D T* time lag will be necessary to get the desired power value.


09-90-E 3-02-11-01-220m P. 2-3


Diagram n° 1

Pmax = Rated power of turbine

Tmax = Max. loading time obtainable from start-up (curve) diagram (taking the difference between the total time necessary to reach 100% rotation speed and the minimum control speed).

00

10%

10%

20%

20%

30%

30%

40%

40%

50%

50%

60%

60%

70%

70%

80%

80%

90%

90%

100%

100%

AUXILIARY CURVE

AUXICURV

LIMIT CURVE

P

T T T

max

AUXILIARYCURVE


09-90-E 3-02-11-01-220m P. 3-3


Diagram n° 2

00

10%

10%

20%

20%

30%

30%

40%

40%

50%

50%

60%

60%

70%

70%

80%

80%

90%

90%

100%

100%

AUXILIARY CURVE

AUXILIARYCURVE

LIMIT CURVE

P

Tmax*

max

TB*

TA*


09-90-E 3-02-12-01-220 P. 1-1


VARIATION IN LIVE STEAM TEMPERATURE

On stationary outlet power condition, a sudden temperature drop of live steam temperature by + 30°C is allowable.

For a further variation in live steam temperature it will be imperative to adhere strictly to the following diagram where a temperature variation in degrees Cent/minute is a function of the percent value for the opening of control valves.

For instance: When running on 50 percent of control valves opening a gradual rise in temperature by 6.5°C/min. is possible till the temperature desired is attained within the range provided for by design data. °C/MIN. 0 20 40 60 80 100% a.v. (v.o.)

a.v. (v.o.) = Valves opening Diagram

10

9

8

7

6

5

4

3

2

1


06-90-E 3-03-10-01-220 P. 1-2


STEAM PURITY

The deposit which occur in a turbine due to impure steam, can lead to thermodynamic and mechanical inefficiencies and, in the presence of chlorides, also to blade breakages. The corrosion stressing caused by active deposits is worst when the steam is slightly saturated and adversely affects the fatigue strength of the blade material.

Recommended values of steam purity for continuously operating turbines are given by ”Society if the Operators of Large Boilers in Germany”. These values are amended from time to time in accordance with appropriate advances in technology.

These recommended values (see table overleaf) are the ultimate values which should be aimed for, but in many cases these cannot be attained with an economical outlay. This is particularly applicable to the commissioning of new plant but is also valid for starting-up and shutting down operations.

In industrial power stations, which nearly always have a make-up water requirement greater than 50%, the conductivity of live steam only reaches values of 1 µS/cm (1 µohm-1/cm) despite considerable expenditure on water treatment. This expenditure how-ever, should be seen in the light of the costs involved when a turbine fails due to impure steam conditions and must be repaired.

It should be noted in this connection, to avoid confusion, that even if the recommended values are rigidly adhered to, it is not possible to completely eliminate deposits in the tur-bine. Amongst other factors the proportions of the impurities play an important part, al-though this is not yet fully understood. In cases where the steam purity of a plant can be raised above the recommended value, every effort should be made to do so.

It is also strongly recommended that a recording instrument should be used to continuously monitor the electrical conductivity of the live steam and turbine condensate following a strongly acid action-exchange unit. In the events of serious contamination saturated steam should immediately be passed through the turbine in order to remove the chlorides which will have been deposited on the blades.


06-90-E 3-03-10-01-220 P. 2-2


Recommended values for live steam condensate

Quantity Unit Recommended value

Continuous* Starting up** Conductivity at 20° C µS/cm

Circulation boiler < 0.3 < 1.0

Once-trough boiler < 0.2 < 0.5

Silicic acid (Si O2) mg/kg < 0.02 < 0.05

Total (Fe) mg/kg < 0.02 < 0.05

Copper (Cu) mg/kg < 0.003 < 0.01

Sodium + Potassium mg/kg < 0.01 < 0.02 * VGB recommend values February 1974 (Siemens instructions 01-90) ** There should be a discernible tendency for this value to fall.

When commissioning new plant the recommended values for continuous should be reached after 2 to 3 days and with starting-up operations after 2 to 3 hours.


02-89-E 3-03-30-01-220 P. 1-6


PROTECTIVE COMPOUND AND CLEANING SOLVENT TECTYL 506 Application

Tectyl 506 is an anti-corrosion agent used for protecting machine parts exposed to corro-sion, i.e. shafts, couplings, tools and other devices, as well as machined castings and for-gings.

Anti-corrosion protection is particularly important for parts which are to be sent overseas and to tropical regions, and for the storage of parts outdoors. Proprieties Marketed as Light-brown liquid solvent carrier Thinner White spirit Yeld 12 to 17 m2/litre, depending on the nature of the surface

(shape, coarseness and porosity of the surface)

Specific gravity 0.9 kg/dm3 Dying period 1 to 2 hours at ambient temperature; agent then becomes

waxy and dry to the touch

Temperature constancy -40 to + 100°C Duration of protection Up to 2 years, depending on the thickness of the film and on

the wear and exposure to which the part is subjected

Transparency The inscription on metal parts remains legible

Tectyl does not affect the hands even after long contact, but they should be washed with ordinary cleansing pasta and warm water.


02-89-E 3-03-30-01-220 P. 2-6


Application of anti-corrosion agent Clean and dry the surface to be protected, carefully removing fingerprints and grease. Tec-tyl should not be heated, but applied at ambient temperature. Method Brushing of application: Spraying Dipping

Brushing Apply Tectyl uniformly with a clean, soft paintbrush. It is not absolutely necessary to ap-ply several coats.

In the surface is coarse, paint Tectyl well into the pores and furrows. Coat all bare parts properly.

Spraying For small quantities, the Lichtenberg spray gun Type LM 54n is suitable and for larger quantities, the Valvoline spray set. Which can be connected direct to the drum.

Dipping Small parts can be protected by dipping them in Tectyl. THE THICKNESS OF THE COAT SHOULD BE AS UNIFORM AS POSSIBLE IN THE CASE OF PARTS TO BE STORED OUTDOORS OR SHIPPED BY SEA. THE DRIED TECTYL COAT IS NOT IMMUNE TO BLOWS OR SCRATCHES. ATTENTION SHOULD BE PAID TO THIS POINT WHEN HANDLING OR TRANSPORTING PARTS.

Flammability Soften with paraffin for 3 minutes and wipe off with a rag. Volatile solvents (petrol, tri-chlorethylene) are less suitable for this purpose, since they evaporate too quickly. Due attention should be paid to the flammability of thinners and solvents.

NOTE


02-89-E 3-03-30-01-220 P. 3-6


DO NOT SMOKE OR HOLD A NAKED FLAME NEAR TO FLAMMABLE SOL-VENTS AND THINNERS. OBSERVE FIRE REGULATIONS. Manufacturer Valvoline Ol-Gesellschaft m. b. H., 2000 Hamburg 36. Neur Wall 75, Federal Republic of Germany. MOLYKOTE PASTE G General

Molykote Paste G is used for reducing friction between metallic surface subjected to high pressures and temperatures. The joining together of parts when erecting machines often results in one metal part rub-bing against another, e.g. when reaming drilled holes, drawing in retaining bolts, and driv-ing in wedges, etc. In braking waterwheel generators excessive friction may also occur be-tween the brake ring of the rotor and the brake linings; this can be reduced by applying Molykote Paste G to the brake linings. Treating machine parts with Molykote Paste G leads to the formation of a durable surface film which protects them against wear even when they are subject to heavy stresses: it also prevents rubbing, seizing, and metal-to-metal-contact. Molykote Paste G is used to finish friction surfaces. I. e. it should be rubbed on to form a thin lubricating film. DO NOT MIX MOLYKOTE PASTE G WITH OIL OR GREASE.

Properties

Molykote Paste G is highly stable chemically, hinders corrosion, is highly resistant to age-ing and does not resinify. Temperature range: -25 to + 450°C with unimpeded exposure to air . It is a concentrated paste of pure, natural molybdenum disulphide combined with a high-grade paraffin mineral oil.

! WARNING

NOTE


02-89-E 3-03-30-01-220 P. 4-6


Application Do not use an excessive amount of Molykote Paste G as with grease or oil lubricants, but apply it thinly and uniformly. Clean the metallic surfaces. Remove excess lubricants with trichlorethylene or a similar agent. Then rub a thin layer of paste vigorously into the metallic surfaces in all directions using a leather glove, stiff paintbrush or Moltopren (synthetic) sponge. Molykote Paste G can be applied to parts immediately before joining them if need be. Manufacturer Molykote KG, Kraus, Kuhn-Weiss & Co., 8000 Munchen 19, Arnulfstrasse 71, Federal Republic of Germany. TRICHLORETHYLENE General Trichlorethylene is also marked under such names as trilene, ethylene-trichloride, Triol, Triolin, Vestrol, Benzonol, Petrazinol, Westrosol etc. PERCHLORETHYLENE (ALSO TETRACHLORETYLENE OR PERAWIN) IS A SOLVENT SIMILAR TO TRICHLORETYLENE BUT IS LESS DANGEROUS. HOWEVER, THE SAME PRECAUTIONARY MEASURES SHOULD BE TAKEN. Application Trichlorethylene is used chiefly for cleaning and removing grease from machine parts. PARTS TREATED WITH TRICHLORETHYLENE TEND TO CORRODE AND SHOULD THEREFORE BE GREASED IMMEDIATELY AFTER BEING CLEANED.

NOTE

! WARNING


02-89-E 3-03-30-01-220 P. 5-6


Properties Trichlorethylene is non-flammable but its vapours can be harmful if inhaled. Precautionary measures Never leave heated trichlorethylene in open containers without taking measures to see that the vapour condensers or is drawn off. Small quantities of cold trichlorethylene in containers without condensing or suction facili-ties can be used on building sites (both indoors and outdoors). IT IS ABSOLUTELY IMPERATIVE THAT VAPOURS BE EFFECTIVELY DRAWN OFF FROM PITS AND SHAFTS SINCE - BEING FOUR AND A HALF TIMES AS HEAVY AS AIR - THEY TEND TO ACCUMULATE AT THE BOTTOM. IF NECES-SARY, SUITABLE BREATHING APPARATUS (RESPIRATORS, GAS MASKS ETC.) SHOULD BE MADE AVAILABLE. MAKE SURE THAT TRICHLORETHYLENE VAPOURS DO NOT PENETRATE INTO OTHER ROOMS WHERE WORK IS BEING CARRIED OUT. DO NOT SHUT OFF THE SUCTION EQUIPMENT OR REMOVE THE BREATH-ING APPARATUS WHILE THERE IS STILL A STRONG SMELL OF SOLVENT. WEAR PROTECTIVE GOGGLES IF THERE IS A DANGER OF TRICHLORE-THYLENE SPLASHING. Procedure Only brushes or cloths should be used for cleaning parts with trichlorethylene. Never expose trichlorethylene to high temperature (over 110°C, perchloretylene over 150°C, dampness, radiation with bright light and contact with red-hot parts, otherwise there is a danger of decomposition into hydrochloric acid and the formation of the highly toxic phosgene. Explosive decomposition is possible in the presence of light alloy chips, dust or powder. Trichlorethylene should not be kept in transparent containers.

! WARNING


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Health protection Avoid alcohol and nicotine. Alcohol and nicotine aggravate the harmful effects of trichlo-rethylene. Take good and regular care of the skin. Before working with trichlorethylene, rub a suitable nongreasy protective ointment into the hands, followed by a greasy skin cream. DO NOT WASH SOILED HANDS WITH TRICHLORETHYLENE. First aid for trichlorethylene poison cases Bring persons suffering from trichlorethylene poisoning at once into a well ventilated room, remove clothing from upper part of body, wrap in blankets and call a doctor. Do not try to force liquids down in the case of person who have lost consciousness. Carefully rub the flats of the hands and soles of the feet. In the case of persons who have already stopped breathing, apply artificial respiration by hand, with oxygen equipment or, best of all, by the mouth-to-mouth or mouth-to-nose method. Flush out any trichlorethylene splashed into the eyes with a 2 percent solution of sodium bicarbonate or with plenty of tap water.

! WARNING


03-09-E 3-13-00-01-190.0531 P. 1-2


STARTING AND SHUT-DOWN TURBINE START-UP General

Before proceeding with the start-up of the turbine it is recommended the efficiency of all plant components be checked.

The starting procedure has a notable effect on shortening turbine life because the major thermal and mechanical stresses are experienced during this stage. This applies particularly for cold starts.

Optimum conditions will therefore be obtained when the temperature of the live steam dur-ing the starting period can be matched to the temperature of the turbine casing as closely as possible. The turbine is normally warmed-up sending steam to the end seals.

For starting a cold turbine which has cooled to below 200°C (390°F) it is recommended to use a live steam temperature as near to the casing temperature as the limits set by the boiler requirements or by other parts of the turbine plant as a whole will permit.

However, the temperature of the live steam must always be at least 30°C (85°F) higher than the saturation temperature corresponding to live steam pressure. Oil system The oil for the steam turbine is supplied from the joint lube oil console (N.P. Job 110.2307/190.0531). The description of the lube oil console components is included in the compressor instruc-tions manual (see section 2 of volume I). For putting the oil system into operation refer to the operating instructions of the compres-sor (these instructions are given in volume I section 4, "Operation"). Check the oil supply to bearings, and that the drain holes on the bearing blocks are not clogged by dirty.


03-09-E 3-13-00-01-190.0531 P. 2-3


Steam piping The live steam gate valve, as well as any by-pass valves, must be closed where as the drains between them and the turbine must be full open. The pipe drains between those valves and the turbine, must be open. This applies to drain lines leading into the condensate collecting tank as well as those leading into the open or into separate drain collecting tanks under atmospheric pres-sure. Have the steam flowing to the front and rear steam seal rings. The pipe drains from the turbine to the condenser must be closed. During the warming-up time it is necessary to rotate the turbine rotor by means of the barring gear in order to prevent rotor strain. The rotor must be rotated of about one turn every 10 minutes. Open the main live steam valve After having thoroughly drained the live steam line downstream from the main line valve, open that valve so that the live steam line to the turbine will be gradually pres-surized and warmed up. If the main live steam valve is equipped with a by-pass valve this has to be opened first in order to relieve the pressure on the main valve. As a matter of a principle, and irrespective of the turbine temperature, one should start from the front end for warming up the turbine. Opening of the emergency stop valves and the control valves For the complete instructions of the start-up sequence see the “Control oil diagram” SOS 8628237 (sheet 1/2) included in the “Compressor Drawings” volume of this manual, the “ELECTRONIC GOVERNOR” volume of this manual, and the docu-ment "Control System Functional Description" included in the “Unit Control Panel“ Volume.


03-09-E 3-13-00-01-190.0531 P. 3-4


The live steam drains may gradually be throttled or even closed on condition that there is a sufficient continuous flow of steam to the turbine; in addition the tempera-ture at the turbine casing inlet side must be at least 50°C, 120°F above the steam saturation temperature in these conditions. The total start-up time of a turbine is composed of the actual start-up period begin-ning with the acceleration of the rotor from standstill up to rated speed and of the loading period from zero to full load. The start-up and loading periods are limited by the thermal stresses created in the turbine during these operations. The necessary starting time is shown on the “Start-up diagram” as a function of the preceding standstill period of the turbine. However, these times are valid presuming that the rotor is not strained when the tur-bine is to be started up from stand-still. Warping of the rotor may be avoided turning the rotor by means of the barring gear. If the turbine has to be started again before it has cooled completely the rotor will have to be turned by fitting a barring gear. During the first 11 hours of stand-still, the rotor must be rotated.

NEVER REMOVE THE SAFETY COVER ON THE MANUAL TURNING GEAR WHILE THE TURBINE IS IN OPERATION. SAFETY HAZARD!

If warping has occurred in spite of these precautions, it becomes necessary to consid-erably extend the turning time and hence the start-up time of the turbine in order to eliminate the defect. A warped rotor can be immediately identified by its accentuated vibrations. If this happens to be the case, the speed of the rotor has to be reduced until the vibra-tions disappear.

! DANGER


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The turbine should be kept at that speed until it is found advisable to bring it up to a higher speed again. It might prove necessary to repeat this process several times with resulting warming-up times considerably in excess of the times indicated on the “Start-up diagram”. While the turbine is being warmed up, particular attention has to be paid to the abso-lute values of casing expansion and to bearings oil temperature, to any vibrations and on the front support bracket bolts being free to move. Bringing the turbine up to speed For a further increase in speed reference must be made to the Start-up diagram and any turbine vibration, must be given due attention. On no account may the maximum permissible values for casing expansion, tempera-tures, etc. be exceeded. During speeding up, there will sometimes be a tendency for the control oil and espe-cially the bearing lubricating oil pressures to drop a little bit. This should be considered as normal and is caused by a change in oil temperature and by the increase suction effect of the journal bearings as a result of the increase in speed. Speed control operation The speed and the output of the steam turbine is then related to the requirements of the compressor unit governed by the ELECTRONIC GOVERNOR CONTROL SYSTEM.


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SHUT-DOWN Reduce down to “zero” the load requests to the steam turbine. Set the speed controller to the minimum control speed. Press the STOP push-button, when the turbine speed is reduced to the minimum control speed. This closes the emergency stop valves and the control valves as a result of the con-trol oil pressure dropping to zero. Close the isolating valve on the live steam line and open all drains on piping completely. During the first 11 hours after shut-down the rotor is to be turned by means of the barring gear. After the turbine has been shut-down, keep the oil supply system in operation as long as this is necessary to prevent the bearing temperatures from exceeding 70°C (155°F) after the oil pump has been shut-down. Open all drains on the turbine casing. In the case of an emergency stop, de-energise the solenoid valves 41XY 50317, 41XY 50318, 41XY 50314, 41XY 50315 and/or energise the solenoid valve 41XY 50313. All devices should always be set in the start-up position. The complete instructions of the shut-down sequence are included in the document "Control System Functional Description" included in the “Unit Control Panel” Volume.


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OPERATING OIL PRESSURE AND TEMPERATURE THE DATA GIVEN IN THIS TABLE ARE APPROXIMATE. THE CORRECT OIL PRESSURE TO THRUST BEARING IS THAT REQUIRED TO DE-LIVER THE OIL FLOW ADEQUATE FOR THE LUBRICATION AND DISSIPATION OF THE HEAT GENERATED. THE FINAL DATA WILL BE DETERMINED DURING COMMISSIONING.

OIL PRESSURE PRELIMINARY

FINAL kg/cm² g kPa g

Turbine control oil header 9 882

Journal bearing (front) 1.5 147

Thrust bearing 1.5 147

Journal Bearing (rear) 2.5 245

OIL TEMPERATURE (during normal running)

PRELIMINARY FINAL

°C °F

Minimum Bearing oil inlet 35 95

Normal Bearing oil inlet 50 120

NOTE


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CONDENSATE DRAINS General

When a turbine is started from the cold, the admitted hot steam condenses at the inner walls of the pipes and casings and forms water. Mechanical damage to the blades has to be expected where larger amounts of such condensate are exceeded and are carried into the turbine.

If the water accumulating at the lowest point of the system is not drained, off, this may cause temperature differences in the casing walls which may lead to objectionable thermal stresses with resulting deformation of the casings and its serious consequential damage.

Draining when starting

Prior to and during the starting period the steam admission pipes, the turbine casing, and all connected pipe lines should be drained until it becomes unlikely that any more conden-sate will form at their inner walls.

With pipes in which the steam is stagnant, the drain must remain open until the moment when adequate steam flow will be ensured.

Draining when shutting off

After shutting off the turbine plant, it is advisable to open all drains, provided it has been ensured that neither wet steam nor cold air have the possibility of penetrating into the heated turbine.

Where such a hazard exists, the drains should be opened when the imperiled turbine parts have cooled down, but in any event at the moment when condensation of leak steam is ei-ther observed or likely to occur.


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Installation of drain pipes

Installation of drain pipes has to be carried out in conformity with the conditions of the site.

When dimensioning and installing drain lines, one should make it a fundamental principle that any reverse flow of steam, water or air in the direction towards the turbine must be prevented, be it at standstill or during operation.


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CONTROL DURING OPERATION Introduction: availability

Economical operation of a turbine plant is largely dependent on its operational safety. A criterion for operational safety is the availability of the machine.

The availability is principally affected by the damages occurring with the main parts of the turbine: the casing and the rotor.

Rather trivial original damage or service trouble with these primary parts may result in ex-tensive consequential damage entailing major repair work with resulting considerable ex-penses in cost and time.

Types of damage Leaving aside damage attributable to foreign bodies the following principal damage groups may be discern: - Damage caused by overspeed; - Bridging of radial design clearances at the blading or shaft packing glands; - Bearing troubles which may be the primary cause underlying the aforementioned

troubles; - Damage to or attrition of casing, blading, or other parts and attributable to incorrect

running methods; - Wear and tear of parts which, owing to the unusually high load stresses to which

they are exposed, have a shorter natural life expectancy than the main turbine parts.

The monitoring of the operations serves the purpose of preventing such damages and trou-bles or, at least, of reducing their extent.

Operational likely to result in damage either immediately or after a few recurrences, have to be remedied by an appropriate change in the operating schedule as soon as the hazard becomes apparent.

Safety or protective devices should be employed for monitoring those operational quanti-ties which in the case of a disturbance are changing at a particularly quick rate.

Appropriate counter-measures will thus be automatically released by these devices as soon as the monitored quantities are attaining a critical limit.


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Supervisory functions of operating personnel

The supervisory functions of the operating personnel are confined to ascertaining those faults and irregularities which are affecting the operating conditions at a comparatively slow rate.

As first thing, the operating personnel should attempt to apply the measures described in the present instructions, in order to safeguard the turbine plant against the hazards of dam-age, of automatically or manually released shutdown, or of outage.

In the fulfillment of their task, the personnel has the current recordings of the operational values at their disposal. The actual readings of the instruments should be compared with the normal reference values in order to obtain reliable information on the actual operating conditions of the turbine.

If the measures taken by the operating personnel for protecting the turbine form a danger-ous condition are failing, the specified emergency measures have to be taken. This must be done even in cases where the correctness of the instrument reading or alarm release value is in doubt.

Inadmissible transgression of limit values

Except where expressly specified in the Test Report, no use must be made of the safety margin left between the extreme Test Report values and the presumptive zone of actual damage. This rule applies even in cases where the operating personnel have previously attained such excessive values when internationally pushing the turbine test beyond the normal op-erating range under conditions of calculated risk and their personal responsibility.

Reference to following instructions The section ”Monitoring of Operations” in the present instructions contains instructions for the behavior of the turbine or turbine set under normal service conditions and in case of disturbances. The instructions are listed according to the quantities measured.

Attention has been drawn to hazardous operating conditions. Such hazardous conditions may refer to the turbine itself, as well as to the monitoring instruments and the safety and protective devices.


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Furthermore is explained, in which way the safety and protective devices are interfering with normal operation in the case of a disturbance and which measures have to be taken by the operating personnel in case of an emergency.


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SAFETY DEVICES Emergency speed governor test

The emergency speed governor shuts down the turbine when speed exceeds 10% of max continuous speed.

Taking account of the importance of this device, it shall be subject to a careful control in-spection, regularly about every four weeks.

This frequency is recommended either if the emergency speed governor is provided with relevant test device or if when overspeeding, the turbine delivers an output higher than out-put required by the turbine operating at such speed.

To the contrary the emergency speed governor may be tested at longer intervals, however whenever there is a shutdown of the turbounit before the following putting into operation.

Before carrying out the overspeed trip test, the emergency trip gear shall be manually actu-ated in order to check the proper operation of control valves and emergency stop valve.

After checking the emergency trip gear operation, the emergency speed governor test may be performed. - For this purpose the turbine may reach the trip speed acting only on the suitable handle of the speed governor - This allows an increase of the secondary oil pres-sure and of the control valve opening, consequently a further increase speed.

If at a 10% overspeed of max continuous speed the emergency speed governor does not operate, it is necessary to stop the test and to check above device.

If these measures should be unsuccessful, please contact the Manufacturer in order to have the emergency speed governor repaired.


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CHECKING DURING OPERATION Steam temperature The steam temperatures for which a turbine has been designed and the temperature permis-sible max. values are listed under the heading "Designed data, Customer'data sheet". Temperatures greater than max. permissible temperature result in a reducing of the useful life of certain basic components of the turbine. For this reason ,every effort to be made for avoiding steam temperature higher than the de-sign ratings. The rate at which steam temperature is changing has also a decisive influence on the life of machine parts. The higher the change rate, and the absolute steam temperature variations, the higher will be the thermal stresses in the material which will be temporarily superimposed on the basic mechanical stress. The extra stresses caused by temperature changes together with the basic mechanical stress may lead to elastic, sometimes to plastic deformation of machine parts even to crake, espe-cially in the turbine casing. Deformation occurring during service may affect the radial clearances and different ther-mal expansion may affect axial clearances. The clearance variations may be temporary or permanent, but they must always be within the unit clearances tolerance: (See "Clearance data sheet" included in the "Turbine Drawings" of this manual). Major changes in steam temperature with resulting distortion of casing parts, partially re-duced pretension in the shrink fits, and rotor warping caused by uneven temperature: all these trouble may affect the normal running of the turbine. Absolute amounts and change rates of temperature are admissible only as shown in the "Variation in live steam temperature dgm" included in this section. Since, besides the temperature changes themselves, the frequency at which they are occur-ring is also of influence on the life of machine parts, this is sufficient justification for the rule that in stationary service the steam temperature is to be kept as constant as possible.


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Changes in load are accompanied by corresponding temperature changes in the highly stressed parts of the machine: for this reason it is recommended to avoid simultaneous changes in load as well as in steam temperature if the temperature change resulting from either of these operations would work in the same direction. When starting, the live steam temperature is to be adapted to the casing temperature. Pre- warming of the turbine from the cold state should therefore be begun already as long as the boiler output temperature is still low. It has to be avoided, however, that the steam conditions in the turbine during the pre-warming period are corresponding to wet steam or saturated steam because the drain lines will be unable to deal with the accruing amount of condensate. The steam temperature at the admission point should for this reason be kept 50°C above the saturated steam condition. With very high pressures, the superheated temperature is to be adjusted even higher (plus 100° C). After short interruptions of service, when the turbine has not yet cooled down ap-preciably re-starting may be made at the full steam temperature. In the some cases, if it is necessary, the starting period of pre-warming with low steam through-put has to be extended. The undesirable consequences of major changes in load with accompanying high rates of temperature change can be attenuated by an appropriate application of inversely directed steam temperatures. In the same way, the effect of large temperature changes can be re-duced to a tolerable amount by appropriate load changes. It goes without saying, that such corrective compensations may be carried out only within the possible margin left by the requirements of the other parts of the turbine plant.

g GE Oil & Gas Nuovo Pignone Maintenance Section 5

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MAINTENANCE

Contents Page - FOREWORD 5-1 - GENERAL 5-2 - SERVICING AND TESTING SCHEDULE 5-3 - GENERAL WASHING INSTRUCTIONS 5-9 - TURBINE WASHING (CONDENSING) 5-15 - BLADE BREAKAGES 5-21 - SALT AND SILICA DEPOSITS, THEIR INHIBITION AND REMOVAL 5-34 - TOOLS – PARTS LIST 5-44 - TOOLS – SKETCHES 5-47

g GE Oil & Gas Nuovo Pignone Maintenance 5-1

06-89-E 4-00-00-S P. 1-1


FOREWORD THE PERSONNEL ENTRUSTED WITH THE INSTALLATION, OPERATION AND MAINTENANCE OF NUOVO PIGNONE PRODUCTS SHALL HAVE THE NECES-SARY TECHNICAL CHARACTERISTICS AND SUITABLE TECHNICAL TRAINING FOR THE TASK IT HAS TO ACCOMPLISH. THESE TECHNICAL CHARACTERISTICS SHALL BE IN COMPLIANCE WITH INTERNATIONAL STANDARD CLASSIFICATION OF OCCUPATIONS, GROUPS 9-61 AND 9-69. ANY DAMAGE, EVEN PARTIAL, ASCRIBABLE TO FAILURE TO COMPLY WITH AFORESAID ESSENTIAL CHARACTERISTICS SHALL BE ATTRIBUTABLE TO THE PURCHASER AND NUOVO PIGNONE WILL BE DISCHARGED OF ANY LI-ABILITY AND INDEMNIFICATION THEREOF. These instructions are provided as a guide to establish an inspection planning and inspec-tion procedure. They cover also the assembly and disassembly procedures providing the essential steps in maintenance of components of the machine. The instructions are written assuming that the personnel performing the maintenance is familiar with this type of work, therefore, information provided includes the essentials only. A LOG BOOK SHOULD BE KEPT FOR EACH MACHINE, IN WHICH REASONS FOR MAINTENANCE, WORK PERFORMED, NUMBER OF HOURS AFTER WHICH MAIN-TENANCE WAS REQUIRED, AS WELL AS ANY INSPECTIONS PERFORMED ON THE MACHINE ON SUCH OCCASION SHOULD BE LISTED EVERY TIME SAID MAINTE-NANCES ARE CARRIED OUT. THIS INFORMATION WILL PROVIDE BACKGROUND MATERIAL ON MACHINE PERFORMANCE AND AID IN SETTING UP THE MOST APPROPRIATE MAINTE-NANCE PROGRAM POSSIBLE WHETHER OR NOT IT CORRESPONDS TO RECOM-MENDATIONS.

! WARNING

NOTE


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GENERAL

The chapter ”Maintenance” deals chiefly with the measures and checking operations which are necessary for ensuring reliable operation of a turbine.

In this connection, we should like to direct your attention especially to the instructions un-der the heading ”Servicing and Testing Schedule” as they do not only describe the required servicing operations, but deal also with the sequence and time intervals at which they have to be performed.

Moreover, the chapter includes instructions on the rinsing and flushing of industrial tur-bines with sufficient information for an operator desiring to undertake the rinsing and flushing operations on his own account.

We are advising, however, that where this is possible, a specialist from our erection de-partment must be called in for that operation.

This appears all the more advisable in cases where, in spite of regular and correct servicing irregularities or damage are showing up with possible consequences which it would be be-yond the competence of ordinary operating personnel to evaluate in their full extent.

The instruction dealing with the causes of blade fracture and of salt or silica deposits will make the operator acquainted with the extensive experience the turbine manufacturer has gained in this field.

The hints regarding the chemical composition of the steam and feedwater will prove help-ful in avoiding hazards similar to the damages described.

IMPROVED OF MAINTENANCE EFFECTIVENESS SHOULD BE ACHIEVED SPE-CIFIC TRAINING OF THE USER'S PERSONNEL WHO SHOULD ATTEND TRAINING COURSES AT NUOVO PIGNONE'S OR AT USER'S SHOP HOLD BY NUOVO PIG-NONE SPECIALISTS.

NOTE


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SERVICING AND TESTING SCHEDULE The checks on the protective, safety, and monitoring equipment must be carried out at regular intervals. The attached tables show the test schedule categories (1 to 4) and the categories for additional checks (A to C) pertaining to each apparatus. The intervals at which the checks have to be repeated may be gathered from the assigned category. Supplementary tests - possibility as a substitute for other checks - should be carried out every time the turbine is shut down or started as long as such tests do not interfere with op-erational safety and will be compatible with the loading and unloading programs. Prefera-bly such testing programs should be carried through during shutdown periods as the oper-ating conditions of the turbine are then better comparable to those prevailing in continuous service. Another point in favor of choosing the shutdown period is that defects which have been as-certained as a cause of malfunctioning can be remedied at once during the subsequent pe-riod of standstill. Interruptions of service offer a welcome opportunity for checking the proper functioning of all elements. After inspections, the checks on all facilities and the required adjustments have to be made with particular care. All tests should be filed for record. The following data must be contained in the record: - Date of test - Test result - Release or trip value (where available), and after inspections - The value to which adjustments have been made.

Test schedule Category for additional check

1 every day A Test when shutting down

2 every month B Test when starting

3 every 3 months C At time of inspection

4 every year


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Test

condition

Test schedule category

Category for addition checks

Equipment 1 2 3 4 A B C Instructions Emergency governor

Service speed

Can be checked only with the help of an emergency governor testing device (see also Section 1 - Description).

Overspeed By means of speeder lever increase tur-bine speed unto the overspeed tripping speed. Compare actual speed value to the reference value given in the Test Report of First Commissioning. This functional test has to be repeated at least a second time in order to get satisfied that the test values are correct. This test can be dispensed with, when an emer-gency governor testing device is pro-vided.

Shaft position indicator

Service

Pull measuring spindle into the stop. Compare actual value with reference value given in Test Report of First Commissioning.

Differential ex-pansion meas-uring service

Starting Observe indicated value. If it happens to be excessively high, stop starting opera-tions immediately.

Service

Additional checks have to be made after major load changes.

Temperature measuring de-vices

Starting Service

Monitor oil temperatures at bearing in-lets and outlets. Compare indicated tem-peratures with the values noted in the Test Report of First Commissioning. Where contact thermometers are pro-vided, check them by allowing the tem-perature to rise a few degrees above the adjusted value with oil cooler kept closed. Re-calibrate thermometers now and again, because of the serious conse-quences of incorrect readings which may be responsible for malappropriate decisions.


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Test

condition



Equipment 1 2 3 4 A B C Instructions Pressure gauges (manometers)

Service Compare indicated pressure with the value noted in the Test Report of First Commissioning. With steam conditions of live and exhaust steam being the same as in the Test Report, the pres-sures in the impulse-wheel chamber and in the intermediate stages - as far as ac-cessible for measurement - ought to be the same as in the Report on condition that the steam throughput is identical in both cases. If appreciable derivations are observed, the flow sections at the blades are likely to be clogged by deposits of salt, silicate or other contaminants. RESTRICTED STEAM FLOW IN-CREASES THE NON BALANCED PART OF THE BLADING THRUST. THIS RISKS TO JEOPARDIZE THE THRUST BEARING AND THE BLADES. FLUSH TURBINE AS PRESCRIBED IN THE TURBINE FLUSHING IN-STRUCTIONS.

Pressure moni-tors

Starting Check whether all pressure monitors are operating properly at their adjusted value (as shown in the Test Report of First Commissioning).

Emergency trip gear

Standstill

Test emergency trip gear for proper functioning a) by operating the knob or lever at the

trip gear b) by remote operation Observe the reponse of the emergency stop valve, extraction valve and servo valve.

Emergency stop valve

Standstill Open or close emergency stop valve by means of the starting device. Observe response. Further testing possibilities see above under Emergency trip gear.

! WARNING


02-89-E 4-02-00-01-220 P. 4-6


Test

condition



Equipment 1 2 3 4 A B C Instructions Service Checking becomes possible only when

using the special testing device (Look up under Section 1 - Description).

Control valves

Standstill Check for easy and smooth operation of the spindles. Adjust oil pressure so that entire valve stroke will be covered (Take pressure values from Test Report of First Commissioning).

Service If turbine is operated for protracted peri-ods with unaltered valve opening check for smooth and easy operation of the spindles by a short actuation of the speeder lever.

Valve actuator Standstill Compare available residual closing ca-pacity of the actuator beyond the closing position of the control valves with the value noted in the Test Report of First Commissioning. If such a reserve is lack-ing, there is the risk of the turbine run-ning up spontaneously. The test can be carried out only by using an auxiliary oil pump. The servo piston will then move noticeably some millime-ters further in the closing direction. The correct adjustment has to be made by the appropriately skilled erection shaft of the manufacturer.

Oil level Standstill Service

Check the oil level in the tank both at standstill and under service conditions of the turbine.

Trip system Standstill Check the trip system as for GE-OIL & GAS – Nuovo Pignone technical specifi-cation n° ITN02201

Oil quality Standstill At appropriate intervals have the quality of the oil thoroughly tested by either a laboratory of the plant at which the tur-bine is installed or by the supplier of the lubricant. If found necessary, drain the water which may have accumulated in the oil tank during a period of standstill.


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Test

condition



Equipment 1 2 3 4 A B C Instructions Oil quality Standstill

IN ORDINARY OPERATION NO WATER IS EXPECTED TO COLLECT IN THE OIL TANK. LOOK FOR POS-SIBLE CAUSE AT ONCE AND REM-EDY.

Oil strainer Standstill The oil strainer has to be either cleaned or exchanged, depending on the degree of contamination.

Oil filter Service Look for the pressure across the oil filter. If pressure difference exceeds the per-missible value operate the change-over valve and clean the contaminated filter.

Oil cooler Service Check indicated temperatures across oil cooler! If temperature differential be-tween oil inlet and outlet is decreasing while quantity and temperature of the cooling water remain constant, the tube banks are likely to be contaminated. Op-erate the change-over valve and clean the cooler.

Auxiliary oil pump

Standstill Service

When the turbine is operated with the auxiliary oil pump, the oil pressures in the governor and bearing oil circuit must show the values listed in the Test Report of First Commissioning Take into ac-count the fact that these pressures are dependent on such factors as oil tempera-ture, the degree of opening of the shut-off valve for the hydraulic turning gear (where provided), and, to no small de-gree, on whether one or several oil cool-ers are connected. Check storage battery where a d.c. pow-ered auxiliary oil pump is installed.

Automatic oil pump control

Standstill May be checked after shutting down when the turbine is running out.

! WARNING


02-89-E 4-02-00-01-220 P. 6-6


Test

condition



Equipment 1 2 3 4 A B C Instructions Bleeder or ex-traction stop valves

Standstill Stop valves for bled steam - uncontrolled steam extraction: - Where a change-over valve is provided, turn its handwheel in the opening or closing direction after having made sure that the emergency-trip-oil circuit, and consequently also the secondary-oil circuit, has attained the prescribed pressure. Stop valves for steam extraction - con-trolled extraction:

Bleeder or ex-traction stop valves

Standstill after trip-oil circuit has attained the pre-scribed pressure, check smooth operation of the valve by means of its handwheel. Test reserve-flow check for smooth op-eration by operating the weighted lever.

Washer under-neath casing bracket and bearing pedes-tal hold-down bolts

Standstill Service

The washers or, where Belleville wash-ers are being used, the cup-spring bushes, must be easily movable. The play left between the head of the bolt and the washer should amount to approx 0.1 mm.

Casing expan-sion

Service The slide-mounted bearing housing not assume its new position in a jerky man-ner when the turbine load is changing.


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GENERAL WASHING INSTRUCTIONS FOR STEAM TURBINES General

Careful supervision of a turbine includes continuous checking the individual stage pres-sures which depend on the steam throughput and output power at any time.

If these stage pressures vary with respect to the reference pressure the turbine passages have been chocked up by deposits unless mechanical defects inside the turbine are present.

Deposit on the valve stems affect the controllability of the turbine. In the event of sudden load rejection the turbine may tend to overspeed if easy movement of the control valves and combined emergency stop valves is no longer insured.

Pressure drop for clean turbine blades Pressure drop for h.p. blades fouled by salt and silica deposits • • • • • • • Pressure drop for l.p. blades fouled by salt and silica deposits

Fig. 1 - Pressure drops and contamination zone of a multi-casing turbine


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Generally, any turbine type is in the same way liable to fouling by salts and silica. The harmful, under given circumstances even dangerous consequences of increasing blade de-posits differ in type.

The efficiency of the blading is reduced, to begin with by the fact that the turbine blade passages are changed and the resulting rougher surface of the blades produces even thicker boundary layers in the steam current.

Furthermore, as a result of the chocked up passages the steam is checked in the turbine blades.

This can lead to an increase in the stage pressure drop and consequently higher blade stresses on the one hand and, on the other hand, substantially reduce the steam absorption capacity of the turbine in the event of a noticeable increase in the wheel chamber pressure, thus materially reducing the maximum turbine power.

The second case usually occurs on topping turbines whose wheel chamber pressure is gen-erally so high that the pressure drop in the nozzles becomes subcritical at the full through-put.

In Fig. 1 the blading of those zones in which salt and silica deposits are mainly experi-enced in the turbine blades are indicated by shading. Curve 1 (blue) shows the pressure drop for clean turbine blades, curves 2 (red) and 3 (yellow) for h.p. blades and l.p. blades fouled by salt and silica deposits.

The salt and silica deposits in the turbine vary with the pressure and temperature of the working steam. Silica (SiO2) and silicate deposits occur in the temperature range from 380°C to 60°C and other salt deposits in the range from 480°C to 80°C. The latter are soluble in water and can be relatively easily removed by washing out the turbine with satu-rated steam or hot condensate.

SiO2 deposits such as Na2Si2O5 can be soluble in water depending on their composition or, in pure form, cause hard deposits insoluble in water.

In the latter case the silica deposits can be removed by the use of a suitable solvent.

In the turbines with a live steam pressure up to 40 bar gauge the coatings will mainly con-sists of salt deposits while at higher live steam pressures they consist of salt and silica de-posits.

When it is found that a turbine has been fouled it is recommended to remove, to begin with, the water-soluble constituents. If SiO2 and salt deposits occur at the same time these may be removed by washing the turbine with condensate or saturated steam. Should this washing method be useless complicated chemical washing must be resorted to.


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As already mentioned, water-soluble constituents can be removed by washing the turbine with condensate. As experience has shown this washing method requires a greater expen-diture than washing by the use of saturated steam. Furthermore, the turbine casing must previously be cooled down about to the temperature of the condensate to be used, which takes an appreciable time.

Also from the economic point of view washing by the use of saturated steam is preferable as is definitely shown by the following comparison of the time taken by the two washing methods:

Washing by the use of condensate

With the turbine casing insulated by mats and at live steam temperature of about 450°C it takes 1,5 days to cool the casing to about 120°C.

With block or sprayed insulation it requires 2,5 days. In addition to this, washing the tur-bine by the use of condensate takes another 6 hours if the washing equipment has been adequately prepared. This means that this method requires a shutdown time of 2 days or 42 hours under the most favorable conditions. 1 Emergency stop valve 2 Control valve 3 Safety valve 4 Back-pressure valve 5 Drains 6 Drain valve 7 Live steam valve 8 Condensate injection valve 9 Blanked off in normal operation 10 Live steam valve

Fig. 2 - Washing scheme of a backpressure turbine


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1 Emergency stop valve 2 Control valve 3 Extraction valve 4 Safety valve 5 Hotwell 6 Drains 7 Drain valve 8 Live steam valve 9 Condensate injection valve 10 Blanked off in normal operation 11 Live steam valve

Fig. 3 - Washing Scheme of a condensing turbine

Washing by the use of saturated steam

The steam cooler and necessary pipe connections, except the washing steam connection to the live steam mains, can already be prepared while the turbine is still on the line. After shutdown of the turbine the preparatory work will take 2 to 3 hours. Cooling the casing with external steam takes about another 2 hours and washing half a day. A well prepared washing operation with saturated steam therefore requires a standstill period of about 11 hours.

Apart from a few special cases where Cu or Fe deposits in the turbine blades where deter-mined which called for washing by the use of condensate, in our opinion washing should always be carried out by the use of saturated steam since the same equipment can be used for washing with saturated steam and for washing with caustic solution.

Generally, one speaks of ”washing by the use of saturated steam, however, dry saturated steam produces no washing effect at all; instead a water-steam mixture, i. e. wet steam, must be used.

For this reason we will speak of ”wet steam” in the following washing instructions.


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Prior to washing, the turbine casing must be cooled down to the temperature of the wash-ing steam or caustic-steam mixture to be used to avoid inadmissible deformations.

Unless casing temperature-measuring points are provided, the casing temperature can read-ily be determined by the use of a sticktype thermometer which is inserted as deeply as pos-sible between the thermal insulation of the casing.

If it is intended to wash the turbine immediately after it has been shut down it is recom-mended to reduce the casing and shaft temperatures by reducing the live steam temperature in the low-load range during the shutdown of the turbine set, in order to shorten the subse-quent cooling time.

This is however only possible with boiler-turbine units, i. e. when the turbine is not sup-plied from a steam header. Otherwise, the cooling process can be appreciably shortened by the use of the washing equipment if the external steam-connection at the steam cooler has approximately the same temperature as the live steam. This process is already a part of the washing operation and is described in the following section.


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CAUSTIC WASHING It is recommended to complete the preparatory work for caustic washing of the turbine be-fore the turbine has cooled down. Depending on the type of turbine this work takes a cer-tain time; it is detailed in the special washing instructions. When washing by the injection of caustic solution it is advantageous if the commencement of the washing operation the whole of the turbine blading it at a definite uniform temperature. In post-cooling of the turbine proceed as follows (see also Fig. 2 and 3).

a) The auxiliary oil pump and the turning gear, if any, are put in operation.

b) The drains (5) on the casing and piping are opened by about one turn.

c) The turning speed is adjusted to 15 to 30% of the rated speed by opening the live steam valve (8) correspondingly.

The drain valve (6) is lightly vented.

d) The steam temperature is reduced at a rate of 2 to 3°C per min. by discretely opening the condensate injection valve.

Prior to washing by caustic injection check with what materials the caustic solution will come in contact. All zinc compounds (brass) and aluminum are deteriorated by caustic soda solution. Turbines in which austenic material is used must not be washed with caustic soda solution.


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WASHING A CONDENSING TURBINE BY THE USE OF WET STEAM General instructions The casings of condensing turbines should as far as possible be cooled down to 110°C ei-ther by a prolonged standstill period or by post-cooling with external steam. Washing with wet steam is effective only if the wash steam is admitted to the turbine with-out being throttled. For this reason the section of the pipe from the steam cooler to the tur-bine must be large enough. Throttling of the steam cannot be completely avoided owing to the differing pipe sections. Care must be taken that wet steam of a sufficiently high mois-ture content is produced in the steam cooler. Since in this case the moisture percentage of the wet steam cannot be supervised, it is nec-essary to measure once more the pressure and temperature of the steam used for washing just before the turbine inlet (see the accompanying washing scheme, Fig. 1). Care should be taken that always some condensate emerges at the end of the steam, cooler drain outlet which should be visible. Experience has shown that this is the case in the wet steam range since the injected condensate is not completely absorbed by the steam. Example Assume that a steam pressure of 9 bar gauge and a temperature of 175°C is measured in the steam cooler at an assumed wetness of 15%. Just before the turbine inlet the steam pressure is only 2.5 bar gauge. The associated steam temperature should than be 127°C. Under these steam conditions the wetness is still 11.3% (see Fig. 5). During washing the condensate salt solution is drained off through the normal drains of the turbine casing, the extraction of back pressure lines and any specially arranged drains.


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1 Emergency stop valve 2 Control valve 3 Extraction valve 4 Safety valve 5 Hotwell 6 Drain valve 7 Drain valve 8 External steam valve 9 Blanked off in normal operation 10 Condensate injection valve 11 Live steam valve

Fig. 1 - Washing scheme of a condensing turbine

Washing with wet steam of constant steam conditions is not very effective. After a certain time the turbine blades reach the temperature of the wash steam and the steam condensa-tion effecting the washing action ceases. To attain the highest possible washing effect in the shortest time it is necessary to increase the temperature of the wash steam in steps by increasing the steam pressure during the washing operation. The turbine speed will be in-creased as the pressure at the wash steam inlet is increased. It is therefore expedient to start washing with wet steam at a during speed of 10 to 15% of the rated speed.


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Fig. 2 - Steam cooler

There is no need for limiting the turning speed during washing to any speed than the rated. However, care should be taken to see that the turbine is not operated at any critical speed for a long time. It may occur that the rated speed is already attained at a low increase in pressure of the washing steam. In this case the turbine casing is cooled by means of the washing equipment and washing is started once more. If it this is repeated several times the same washing effect can be ob-tained as with a continuous increase in steam temperature. With the aid of the general washing diagram (see Fig. 3) a special diagram for the particu-lar turbine should be prepared on the basis of the results of the first washing operation. A temperature difference of 30 to 50°C, referred to the duration of the washing operation, will be sufficient. This value corresponds to a pressure difference of 2.5 to 7.5 bar gauge. Enclosed is a washing diagram recorded on a 2.5 MW turbine (see Fig. 4).

Fig. 3 - General washing diagram

0

20

40

60

80

100

WASHING TIME 50% 100%

% AVAILABLE PRESSURE OR TEMPERATURE DIFFERENCE OF THE WASH STEAM


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Fig. 4 - Washing diagram of a 2.5 MW turbine

Washing is completed when the effluent from the drain outlets is clear and the analysis of samples shows that only very slight traces of salt are contained in the drains. Samples for determining the salt content in the condensate should be taken at intervals from 15 to 30 min. If, after a certain washing period, the salt content in the condensate samples obtained during a period of more than 30 min. remains constant the wash steam temperature is in-creased by a few degrees. A few minutes later another sample is taken if its analysis shows that the values remained unchanged, washing can be stopped. Washing can be expected to take 3 to 5 hours. Preparatory work 1. A steam cooler corresponding to the turbine size is built, (see Fig. 2). The flanged connection for wash-steam, supply must be NW 40 for turbines up to a

rating of 4 MW, NW 50 for turbines up to 10 MW, and NW 65 for turbines above 10 MW rating. The flanged connection for the external steam supply must be determined to suit the pressure head of the steam to be used.


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2. With wet steam the second flanged connection NW 15 is not needed and is therefore blanked off.

3. A condensate line is connected to the other flanged connection NW 15. The conden-

sate pressure must be at least 3 bar gauge above the maximum expected wash-steam pressure in the steam cooler. A connection from the feedwater pump will be of par-ticular advantage. A finedosing valve is provided in this line.

4. The steam cooler drain pipe is provided with a valve. The outlet of this drain pipe

should be visible. 5. The steam cooler is provided with an external-steam connection fitted with interposed

valve. 6. The steam cooler is connected to the wash-steam tap on the live-steam mains. 7. Suitable instruments for measuring pressure and temperature are provided on the

steam cooler. 8. The wash-steam pressure is measured just before the turbine inlet. Since the service

instrument which is generally connected just before the combined emergency stop valve has a too large measuring range, a suitable gauge is provided on the check flange of this pressure indicator or used to replace the service instrument.

9. The service thermometer in the live-steam mains or in the steam chest is replaced by a

stick type thermometer with a suitable measuring range. 10. The turbine drains and the drains of the back-pressure lines before the extraction valve

are separated behind the valve they are connected to a header. With welded-in drain valves it is sometimes easier to break the drain header just be-

fore the condenser. It will be advantageous to provide a flanged connection or an in-termediate piece at this point.


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Fig. 5 - Representation of the washing operations in the i-s diagram


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BLADE BREAKAGES (In the condensing zone) Introduction Blade breakages in steam turbines continue to occur in isolated cases. Only in a very few cases is a breakage the result of a material, design or manufacturing fault. The breakages seldom occur in the high temperature part of the turbine, nearly always at the beginning of the condensation zone. Depending on the steam throughput, the initial steam conditions and the condenser vacuum, the position of this zone varies over several blade rows. Most broken blades exhibit fatigue features (Fig. 1). Sometimes the fatigue fracture is initiated by a non-deformed fissured crack (Fig. 2). Deposits from the steam are almost always found on the blades and when examined are found to contain small quantities of chlorides.

Fig. 1 - Fatigue fracture in an l.p. blade

Fig. 2 - Non-deformed fissured crack, the starting point of a fatigue fracture


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Chemical composition (mean values) in % Material C Si Mn Cr Mo Ni V Ni X20 Cr 13 0.20 0.30 0.45 13.5 - - - - X20 CrMo 13 0.20 0.30 0.45 12.5 0.8 - - - X22 CrMoV 121 0.21 0.30 0.5 12 0.8 0.40 0.30 - Mechanical composition (mean (values) in %

Material 0,2% yield strength Tensiel strength Elongation Notch impact strength DVM test or*) ISO test (Kpm/mm2) (Kpm/mm2) (Kpm/mm2) % (Kpm/mm2) X20 Cr 13 60 80 15 4 X20 CrMo 13 60 80 15 4 X22 CrMoV 121 60 80 15 5

Fig. 3 - Chemical composition and mechanical properties of 11-14% Cr steels for turbine blades.

Blade material All turbine manufactures use blade steels with an 11 to 14% Cr contents. Siemens and N. Pignone select their steels from the table shown in Fig. 3 depending on the stresses and temperatures involved. At the beginning of the condensation zone mainly X20 Cr 13, and 20 CrMo 13 steels are used.

Steam quality and blade deposits It has been shown that the steam quality and the related blade deposits have a considerable influence on the life of the turbine blades. The view was often expressed in the past that such deposits were quite normal and could not be prevented. Since then, however, developments in the steam boiler field have led to the necessity for feed treatment which has made a great contribution towards the elimination of blade de-posits. With once-through boilers the same purity is demanded of the boiler feedwater as


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of the initial steam, since practically all salts pass straight through the boiler and will oth-erwise be deposited in the turbine. With natural circulation boilers on the other hand, the salts are separated in the boiler drum and concentrate there. Of course there is the danger that the salts will be carried into the turbine with the steam if the boiler should prime and, if the density of boiler water be-comes excessive, there is the possibility of some salts, mainly silica, becoming fully dis-solved and being carried over with the steam. The VGB have issued recommendations for feedwater, boiler water and turbine steam. Ex-perience has shown that the blade breakages will seldom occur if these values are adhered to closely. There are also target values for steam quality which will result in practically a complete absence of deposits if they are attained (see 3-03-10). The VGB recommendations are usually maintained only by the large power stations. Smaller stations particularly the industrial power stations which require a large amount of make-up water, often ignore these values for economic reasons. However it must be re-membered that the factors which lead to blade damage are only dependent on the steam quality and not on size of the station. The substances deposited on the blades from the steam (Fig. 4) restrict the blade channels and roughen the blade surfaces which causes a reduction in efficiency, an increase in stress and interference with the thrust. The blades are particularly susceptible to corrosion when the deposits contain chlorides. At the beginning of the condensation zone, and at places of moderate steam wetness, silicic acid is most commonly found, usually in amorphous form but also as crystals and as sili-cates. It is assumed that the amorphous silicic acid absorbs, amongst other substances, chloride ions. The first droplets of condensate formed, although very small, are sufficient to dampen the salt deposits on the blades. Sufficient quantities of condensate to wash away the deposits only occur in the later rows of blades, so that the chloride salt solutions of a concentration perfectly suited to corrosion attack are formed on the blades in that zone of the turbine in which condensation begins to occur.

Fig. 4 - Deposit on turbine blades


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There are also other reason why this zone is particularly liable to corrosion attack. It is common practice in modern boiler plant to absorb any residual oxygen in the boiler water with hydrazine.

The excess hydrazine also acts as an alkalization agent, but only up to approx. 350°C. Above this temperature the hydrazine in the boiler breaks down into ammonia and nitrogen and only traces of hydrazine are found in the turbine condensate. Ammonia is an effective alkalization agent above 350°C. Because of its very high partition coefficient, ammonia remains largely in the gas layer so that the first small droplets of condensation are not alka-lized. Also, if calcium chloride and magnesium chloride are present in the circuit, they break down and form hydrogen chloride.

The partition coefficient of hydrogen chloride is less than unity which means that it tends towards the liquid layer as condensation begins and hence forms and acid solution which, to begin with, cannot be neutralized by the ammonia.

This results in the first droplets of condensation having a low pH value and hence they are corrosive. The pH value in the affected zone can be raised by injecting hydrazine or an-other volatile alkali into the turbine when the temperature is under 350°C, but before reaching the saturated steam limit. Blade corrosion Corrosion in turbine blades takes various forms. Depending on the corrosive agent, the re-sistance of the material to corrosion and the stress conditions, the attack can take the form of

Pitting Corrosion fatigue Stress corrosion. Pitting

The resistance to corrosion of the Cr steels results from their passive surface film of chro-mium oxide. This film can be destroyed by halide ions, in particular the chloride ions. The attack which occurs under the deposit on the blades concentrates at a large number of small areas so that very small anodic areas are opposed by very large cathodic areas. The small areas quickly reach a considerable depth. Because of the mechanism of the at-tack, this form of pitting corrosion is also called chloride ion corrosion. Pitting is most frequently found under blade deposits in the wet steam range (Fig. 5). Blades free of deposits are not attached at all or perhaps only slightly.


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Pitting can also occur when the machine is not running if steam is leaking into the cold tur-bine.

Fig. 5 - Blades covered with deposit and pitting occurring underneath

Fig. 6 - Blades pitted through standstill corrosion Fig. 7 - Cracks originating from pitting corrosion (after magnetic crack detection)


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Quite considerable damage can be caused (Fig. 6) which is then known as standstill corro-sion. Corrosion of this type can occur on all blades of the turbine, there appears to be no particular preference for the blades in the wet steam zone. In the wet steam region, cracks are often found which clearly originate from the pitting (Fig. 7). The notch effect of the small pits assists the formation of these cracks. The possi-ble higher concentration of the chloride ions in the pitting also plays a role but, in fact, the pitting and cracks must be considered separately.

Pitting is clearly related to corrosion alone whereas the cracks arise as a result of corrosion fatigue. Corrosion Fatigue

When a component is subjected to stress reversals without the presence of corrosion, a definite value of stress will be withstood indefinitely without a fracture occurring, this is called the endurance limit (the horizontal leg of curve a in Fig. 8).

If the stress reversals are accompanied by corrosion attack, however, not only will the fa-tigue strength be reduced but the curve will also continue at a slight angle to the horizontal axis.

The result is simply a fatigue strength of finite life depending on the number of stress re-versals (curves b and c, Fig. 8).

All metals are subjected to corrosion fatigue, even the stainless blade steels.

The occurrence of corrosion fatigue is not necessarily combined with the appearance of corrosion on the outside surface of the metal.

It is found on blades which have no deposit or visible signs of corrosion. However, in this case only one crack is found in contrast to Fig. 7.

The damage caused by corrosion fatigue in the internal structure of the metal is sub-microscopic, which makes evaluation difficult.

In appearance, the fracture always resembles a fatigue fracture (Fig. 1). The corrosion is caused by the wet steam condensate whose impurities play a very important role in the pro-cess.


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Fig. 8 - S-N- Diagram in air and subject to corrosion

The stress reversal fatigue strength is not at all so sharply reduced (curve b, fig. 8) by con-densate droplets free of chlorides (pH value: 6.5 - 8, conductivity: 2 - 5 mS/cm) as with droplets containing chlorides (curve c).

The effect of the chloride ion concentration on a carbon steel has been examined by Glik-man. The results show that even an NaCl content of 0.0025% has a considerable effect.

The corrosion fatigue strength becomes greater as the NaCl content becomes less. This means, if the very slight slope of the curve in the S-N diagram is taken into account, that by reducing the NaCl content of the steam the possibility of a blade breakage can be de-layed by a considerable time.

All sources quoted on this problem are generally of the opinion that all NaCl concentra-tions over 1% have a strong damaging effect.

For many years our laboratories have been studying the various factors involved in these processes by means of tests on both flat bar test pieces and actual blades.

Some results had already been published and these were subsequently confirmed. Only the most important results have been selected from the extensive research program and for the sake of simplicity they are presented in diagrammatic form.

The results obtained with flat bar test pieces of X 20 Cr 13 steel are shown in Fig. 9. The determination of the corrosion fatigue strength is based on 5-107 stress cycles.

10

0

20

30

40

50

104 105 10 6 107 10 8

Air

Chloride-free condensatecorrosion

NaCl solution

Stress cycles n

Maximum stress

ºbw(kgf/mm )

2a

b

c


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The following conclusion can be drawn from the test results: 1. The stress reversal fatigue strength of X 20 Cr 13 with the surface ground in the

same direction as the stress application is, in air, + 40 kgf/mm2, i. e. approx. 0.5x ten-sile strength.

2. If the surface is ground at right angles to the direction of stress application the stress

reversal fatigue strength falls only slightly to + 34 to + 36 kgf/mm2. 3. The fatigue strength of the un-notched test piece in clean condensate is between +

28 and + 32 kgf/mm2. 4. In chloride solutions (NaCl content > 1%) the corrosion fatigue strength of the un-

notched test piece is reduced very sharply to + 12 to + 14 kgf/mm2. This means a re-duction of the stress reversal fatigue strength by approx. 65% over the value obtained in clean condensate.

5. When the test piece is notched, the stress reversal fatigue strength without the pres-

ence of corrosion is reduced to + 16 kgf/mm2. 6. When the notched test piece is subjected to a salt solution with a NaCl content >1%

the corrosion fatigue strength is reduced even further to + 5 to + 7 kgf/mm2.

The result obtained with blades of X 20 Cr 13 are shown in Fig. 10. The values differ from those obtained with flat bar test pieces (Fig. 9) because the form factor of the undamaged blades is>1.

The following may therefore be stated: 1. The stress reversal fatigue strength of transversely ground undamaged blades of X 20

Cr 13 is + 30 kgf/mm2 in air. 2. The corrosion fatigue strength of undamaged blades in chloride solutions in again

sharply reduced to + 12 kgf/mm2. 3. In air, a notched blade still has a stress reversal fatigue strength of + 22 kgf/mm2. 4. The corrosion fatigue strength of notched blades in chloride solution is + 7 to 12

kgf/mm2 clearly higher than that of the notched flat bar test pieces (+ 5 to + 7 kgf/mm2).

This is explained by the notch not being at the most highly stressed part of the blade.


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1. Un-notched test piece, ground longitudinally 2. Un-notched test piece, ground transversally 3. Notched test piece (from form factor ak = 2,4) 4. Un-notched test piece, ground transversally, in condensate free of Cl 5. Un-notched test piece, ground transversally, in NaCl solution 6. Notched test piece (from form factor ak = 2,4) in NaCl solution

Fig. 9 - Stress reversal fatigue strength of flat bar test pieces of X20Cr 13 steel

Fig. 10 - Stress reversal strength of VN26735 blades of X 20Cr13

75

75

2020

Un-notched test piece

Test piece shape:

Notched test piece

0

± 10

± 20

± 30

± 40

1 2 3 4 5 6

~65%

NaCl content >1%

Condensate free of Cl

Scatter of results

In air Subject to corrosion

Deteriorationcaused by

ºbw(kgf/mm )2

Test piece shape: Un-notched test piece

Notched test piece 2

3030

0

± 10

± 20

± 30

± 40

1 2 3 4

~60%

Scatter of results

In air Subject to corrosion

Deterioration causedby NaCl content>1%

ºbw(kgf/mm )2

1. Un-notched blade, ground transversally 2. Notched blade, Iso V notch (2 mm deep) at the trailind edge 3. Un-notched blade, ground transversally, in NaCl solution 4. Metched blade, as in 2 NaCl solution


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Stress corrosion Three conditions must be fulfilled before stress corrosion can occur: 1. The component must be subjected to static tensile stress (including internal stress). This is the case with turbine blades which are subjected to a tensile load by centrifu-

gal force. Internal stress plays little part. 2. The material must be susceptible to stress corrosion. Generally speaking, the 11 to 14% chrome steels are known to be resistant to stress

corrosion. It can be seen from the references that these steels will only be effected by stress corrosion if they are tempered below 600°C.

The turbine blade steels, however, are tempered at 650-740°C. 3. A corrosive medium must be present. With the 11 to 14% chrome steels, both anodic and cathodic stress corrosion occurs.

The latter is better called hydrogen embrittlement because the hydrogen liberated by the corrosive action diffuses into the metal and causes embrittlement which may sub-sequently lead to a brittle fracture.

Cathodic stress corrosion is mainly observed under attack by weak acids, particularly hydrogen sulfide. An excess of hydrochloric acid in the first droplets of condensate within the turbine has the same effect.

Fig. 11 - Stress corrosion cracks in a blade


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Anodic stress corrosion occurs mainly in chloride solutions but also in other salt solutions. Tests on a standard blade steel in a boiling 3% NaCl solution resulted in no cracks.

If the metal had been tempered at under 600°C, however, intercrystalline cracking oc-curred. In spite of this, however, blade damage has occurred in isolated cases which was most probably the result of stress corrosion. Fig. 11 shows cracks found in a blade at the beginning of the condensation zone.

Characteristically, a high proportion of iron (III) chloride was contained in the deposit found on the blades. It can be concluded that there was a reaction between the hydrochloric acid and the blade material (see «Steam quality and blade deposits»).

Our own tests on X 22 Cr MoV 12 1 have shown that a tempering temperatures of 700 + 740°C, stress corrosion (Figs. 12 and 13) only occurs in boiling solutions of: 1. 40% CaCl2 + 0.1% HgCl2 2. 40% MgCl2

3. 1% FeCl3 + n10

HCL


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Fig. 12 - Stress corrosion crack, boiling 40% MGCl2 solution

Fig. 13 - Stress corrosion crack, boiling 40% CaCl2 solution

Summary and conclusions

Pitting is easily recognizable. More difficulty is experienced in distinguishing between corrosion fatigue and stress corrosion. However, it is not so important to determine whether the fracture has been caused by corrosion fatigue or by stress corrosion as to rec-ognize the cause of the corrosion and to take appropriate corrective action.

Without doubt, the best solution to the problem would be to operate with steam completely free of salts so that no deposits form on the blades.

Referring to corrosion fatigue, this would correspond to curve b in Fig. 8. In actual fact, a low salts content and occasional heavy carryovers must be reckoned with so that the result will be a corrosion fatigue strength lying between curves b and c.

Thus it can be seen that every successful attempt made to improve the purity of the steam/water in the system results in an increase in the corrosion fatigue strength. The test durations are plotted on a logarithmic base which means that even a very small increase re-sults in a substantial gain in time, and hence a considerable increase in the life of the tur-bine blades.


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The operator is, therefore, in a position to exert a considerable influence on the life of the blades by the manner in which he operates the turbine. The costs of feedwater treatment must be weighed against those incurred in the event of blade damage, including damage to other components and the reduced availability.

Continuous monitoring of the water/steam system is essential to avoid, or possibly, evalu-ate corrosion damage to the turbine blades.

Turbine operators and builders are unanimous in strongly recommending the recording of the electrical conductivity of the live steam and turbine condensate after a strongly-acid ac-tion exchange water treatment plant.

This permits even the slightest leaks of cooling water into the circuit to be detected. If salts should gain access to the turbine, flushing with saturated steam according to our special in-structions should be carried out immediately in order to remove any chlorides which may have deposited themselves on the blades.

If such measures are not taken, there is a danger that the fatigue strength of the blades will be reduced by more than half and the possibility of a fracture is correspondingly greater.


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SALT AND SILICA DEPOSITS IN STEAM TURBINES, THEIR INHIBITION AND REMOVAL General introduction

In the thirties when a change was made from high pressure steam to superpressure steam and pressures substantially above 50 kg/cm2 gauge were reached, the shortcomings in wa-ter treatment and partially as a consequence of these, the effects of turbine blade deposits become very noticeable.

Since then feed water treatment has been considerably improved by the use of evaporating plants and demineralization plants; however, there still are loud complaints about turbine blade fouling by salt or even silica deposits which deteriorate the turbine power and the operational availability of the existing turbines.

Deposits in turbine blades are rightly feared since these can noticeably upset turbine opera-tion. Such deposits choke up the passages of the guide blades and moving blades, causing a noticeable loss in the efficiency and power.

In addition to a reduction of the turbine power they can also cause mechanical defects such as an increase in the axial thrust and hence overloading of the turbine thrust bearing and jamming in the control valves and emergency stop valves.

Furthermore mention should be made of the chemical effects corroding the blade material.

Kinds of deposits For a better under standing of the salt and silica deposits in steam turbines it will be expe-dient to follow the steam on its passage from the superheater outlet to the condenser inlet. In all boiler plants of any type of construction a small amount of water is carried over in the form of very fine water droplets from the boiler drum or evaporator section into the su-perheater when its temperature is raised to a level which lies substantially above that of boiling water.

Here the greatest part of the water is evaporated so that a high salt concentration. The man-ner in which the salt deposits in the turbines are effected is still disputed. At present, the following four theories are advocated: 1. The agglomeration theory by Straub


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2. The salt-melting theory by Michel

3. The slippery-ice Theory by Werner

4. The main-forces theory by Wickert

A discussion of these theories is beyond the scope of these instructions. It should only by noted that the four theories are not applicable to all salt and silica deposits, but apply in special cases only.

On the basis of the experience gained during recent years and the results form analyses of the salt and silica deposits in turbines a new theory of deposits is obtained which will be dealt with below.

As the superheated steam leaves the superheater of the boiler and is passed on to the tur-bine it contains some salts in crystalline form such as salt dust, salt melts in the form of droplets in addition to a small quantity of salts dissolved in the steam.

This mixture of salt and stean enters the turbine and its velocity with which it passes through the individual turbine stages is raised to several hundred meters per second in the nozzles, depending on the steam pressure and on the type of turbine.

Owing to their adhesive forces (stickiness), the salt melts suspended in the form of very fine liquid droplets in the steam stream are deposited in the individual stages (see Fig. 1).

They remain in the liquid state if the salt melts mainly consists of sodium hydroxide (NaOH), or solidify in the case of composite salt mixtures in an undercooled state.

Separation of the latter is prompted by the fact that the temperature of the melt particles suspended in the steam stream is always higher than the temperature of the associated tur-bine stages.

In this process salt particles are caught by a stickly layer acting as a «fly-trap» and are in-corporated in the growing deposit layer.

The results of an investigation on 36 turbine plants about the qualitative composition of the deposits are shown in Fig. 2. The deposits were taken from turbine parts in temperature range between 50 and 500°C.


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A Turbine inlet B Nozzle outlet C Inlet to h. p. turbine stages D Inlet to l. p. turbine stages E Inlet to condenser 1 Light deposits of salt melts and dust 2 Salt dust deposited 3 Salt melts deposited 4 Salt dust deposited (mainly insolube in water) 5 Light separation of salt dissolved in steam 6 Heavy separation of salts dissolved in steam

Fig. 1 - Salt steam through the turbine The results from this investigation show that silica is the dominant constituent which was found in 80% of the samples, NaCl deposits were found in about 22% of all samples. The remaining compounds occur very seldom and to a very limited extent only. The following turbine blade deposits dealt with below are: SiO2 Silica or quartz NaCl Sodium chloride (salt) Na2SO4 Sodium sulphate (Clauber’s salt) NaOH Sodium hydroxide (caustic soda) Na3PO4 Sodium phosphate


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Fig. 2 - Turbine deposits

From a multitude of turbine blade deposits a typical graph (Fig. 3) could be developed for most turbine deposits, showing the distribution and composition of the salt deposits.

Here, the two antagonist are NaCl and SiO2 SiO2 increases in the same proportion as NaCl decreases. Assuming a narrow channel of NaOH being interposed at the boundary between the two main salts, a reaction zone is obtained between NaOH and SiO2 which leads to the forma-tion of Na2 Si2O5 which is soluble in water. In the early turbine stages only a limited amount of SiO2 is deposited so that a NaOH surplus occurs which is indeed traceable in the first turbine stages.


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With increasing silica deposits, however, more and more the NaOH is bond until finally the process is reversed and the NaOH deposits suffice only to neutralize a limited amount of SiO2.

The water-soluble silica content is practically reduced to zero and the zone of silica depos-its sets in the more so the greater the decrease of the NaCl content in the deposits.

Specific salt concentration in turbine steam Checks on numerous turbines disclosed that salt deposits in turbines are more frequent with drum type natural-circulation boilers than with forced-circulation boilers.

This may be due to the fact that in the case of the forced-circulation boiler the total salt content of the feedwater is rather low.

The checks also showed that turbines remain practically free from any salt deposits if the salt concentration does not exceed a definite value which is known as the specific salt con-centration.

Fig. 3 - Schematic representation of turbine salt deposits


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The operating companies will in the first place follow the instructions of the boiler manu-facturers which prescribe a certain degree of purity for the feedwater and steam.

For guidance in practical operation useful mean values were compiled in the form of a ta-ble (Fig. 4).

Based on the experience gained in practical turbine operation the total specific salt concen-tration was divided into a permanent and a temporary component.

The permanent specific salt concentration (a) designates the quantity of salt at which the turbine, after 8000 hours of continuous operation, does not show any appreciable signs of salt deposits.

The temporary specific salt concentration (b) designates the salt content resulting from op-erational conditions (frequent starting and stopping).

Finally, for reason of completeness, a salt limiting value (c) is specified at which the tur-bine blading will be partially choked up in a short time.

The values specified should not, however, be considered as absolute values, but vary within certain limits.

The steam pressure and temperature as well as the turbine design have an additional effect on the specific salt concentration; however the influence of these factors is not as large as that between the groups a, b, and c.

The above table will give very useful values for the operation of steam turbine plants.

NaCl

As Can be seen from Fig. 4 the specific permanent salt concentration (a) is about 0,4 mg per liter. At this value the turbine can be operated with certainty for 8000 hours.

The temperature range and the amount of the NaCl deposits are mainly dependent on the superheated-steam conditions.

On superpressure turbines (120 kg/cm2 gauge and higher) salt is deposited at a high rate and this starts already at a high temperature (about 450°C) and reduces appreciably with decreasing temperature.

On m.p. turbines (40 to 60 kg/cm2 gauge) the deposition of salt layers starts already at a lower temperature, and at a lower rate.

This is connected with the limiting salt content of saturated steam dependent on the steam pressure, i. e. high-pressure steam has a higher salt concentration capacity.


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Salt content in steam [mg/l]

a Permanent specific salt concentration b Temporary specific salt concentration

c Salt limiting value

Fig. 4 - Specific salt concentration in steam turbines SiO2

As already mentioned, the tendency of silica to cause turbine fouling is particularly high there exists no limiting salt content, but only a limiting solubility in steam, which depends on the steam pressure and temperature.

On its passage through the boiler silica is already dissolved in the satured steam, the solu-bility in the superheated steam being a multiple of that in the saturated steam.

The steam admitted to the turbine precipitates more and more silica from the gaseous phase at falling pressure and falling temperature. This means that silica is deposited in the turbine blades irrespective of the silica content of the steam.


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The less the SiO2 content of the steam, the more are these deposits shifted towards the tur-bine end and to the zone of lower temperatures if the turbine is only kept running for a suf-ficiently long time. In the absence of any companion salts the turbine end blading would be fouled completely by silica. However, in the presence of other salts such as NaOH or NaCl the probability of the silica deposits being dissolved is more or less greater. In the presence of NaOH the silicate changes to Na2 Si2 O5 which is soluble in water and can be washed out during the shutdown of the turbine. If only NaCl is present a conglom-erate builds up of SiO2 and NaCl crystals which also insures a certain solubility of the SiO2 deposits since, on stopping and starting the turbine, the sodium chloride (NaCl) is detached from the crystal combinations and the remaining SiO2 crystal structure disingrates.

However, in the presence of only limited NaCl or NaOH quantities the turbine blading will be fouled by heavy insoluble silica deposits. Na2 SO4 In boiler plants whose boiling temperature is appreciably above 250°C (50 kg/cm2 gauge) practically all the Na2SO4 dissolved in the boiler water carried along is precipitated in the superheater since during the subsequent evaporation the water droplets attain the tempera-ture at which Na2 SO4 is precipitated earlier in their passage than the increase in salt con-centration at which different solubility conditions obtain. This applies particularly in the presence of an appreciable NaCl concentration. Only at boiler pressures below 40 kg/cm2 gauge, at which the associated superheated-steam tem-peratures are relatively low, the increase in the salt concentration takes effect earlier than the temperature increase of the salt solution. Less Na2 SO4 in then precipitated in the boiler so that the greater part of the salt is passed to the turbine. Na OH

Since the boiler water nearly always contains NaOH, there must also be an enrichment of NaOH in the water droplets. As a result of the steady heat absorption in the superheater the boiling point and the concentration of the salt solution are further increased until the steam leaves the superheater and enters the turbine.

If the boiler water were free from NaOH any salt whose solubility limit is exceeded would be precitated from the solution in the form of salt deposits in the superheater or be carried as salt dust by the steam into the turbine.


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The presence of NaOH, however, changes the conditions fundamentally. NaOH is not pre-cipitated, but forms melts at the temperatures prevailing in the superheater.

The boiling temperature of these melts increases with increasing concentration and in-creasing steam pressure.

In superpressure turbines the NaOH deposits will be very limited as a result of the low al-kalinity of the feedwater. In i. p. turbines, however, the rate of NaOH deposits will be far higher.

Na3 PO4 With regard to its tendency towards the forming of deposits in the blading this salt ranges between NaCl and NaOH as a result of its chemico-physical nature.

It is added to the feedwater of all drum type natural circulation boilers to attain protection against temporary hardness surges.

Summary

The composition of the matter coating the blades of low-pressure turbines differs widely; it mainly consists of water-soluble salts, scale forming agents (Ca and Mg compounds), ero-sion and corrosion products.

At the highest steam pressure the blade deposits contain water-soluble salts, first of all NaCl and to a lesser degree NaOH and silicates. Na2 SO4 is already precipitated in the su-perheater of the boiler. The insoluble compounds mainly consists of SiO2.

The salt deposits on the turbine blades vary with the temperature of the particular turbine stage. On the basis of a great many investigations the following series could be deter-mined: sodium sulfate, sodium disilicate, sodium chloride and silica with its sub-groups such as quartz, cristobalite and amorphous silica. The specific temperatures of the individ-ual compounds however overlap substantially.

The amount of salt deposits in the turbine blades does not depend very much on the pres-sure. However, the water-soluble salts generally occur in large quantities only at low steam pressures whereas quartz and amorphous silica are preponderant only at high and extra high pressures. This is due to the NaOH contained in the boiler feedwater, which is present in ample quantities at low pressures, but in small quantities or not at all at high and super-high pressures since it is generally replaced by other alkalizing substances such as ammo-nia or hydrazine.


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Appreciable turbine blade fouling can be avoided if the salt content of the steam is so low that the specific salt concentration is not exceeded. Depending on the composition of the boiler water salts it is higher or lower.

Even substantially smaller quantities than those corresponding to the specific salt concen-tration lead to damages to the blades by reducing the alternating bending strength of the blade material.

The salt content of steam in natural-circulation boilers not only depends on the boiler water concentration but also on the kinetic energy with which it enters the boiler drum and on the effectiveness of the drum internals.

The maintenance of the correct drum water level and the avoidance of hardness surges is imperative from the operating point of view.

In forced-circulation boilers the salt content of the steam depends on the degree of care given to the operation of the evaporators or demineralization plants.

Great importance has also be attached to the condenser being leak-free. With these types of boiler the salt content of the feedwater is generally less than the permissible capacity re-duction of the associated steam turbine so that for this reason turbine blades will rarely be fouled except by silica deposits.

Even in the presence of only a trace of salt dissolved in the steam there will practically al-ways be some folding, if the turbine is kept in operation for a sufficiently long time.

This can be kept at a minimum if sufficient care is exercised in boiler control and in water treatment so that no or only a limited downtime will be experienced. As already mentioned, it is always necessary to remove any silica and salt deposits from time to time.


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Parts List: SLO 0502835

GENERAL LIST OF THE ASSEMBLING/DISASSEMBLING TOOLS STEAM TURBINE TYPE: SAC 1-15

NAME AND USE N.P.CODE Q.TY

ASSEMBLING TOOL SLO 0502853 1 for control valves

ASSEMBLY TOOL SLO 0502806* 1

ASSEMBLY TOOL SLO 0502840* 1

BOLT HEATING SOL 26539 2 RRO 00162


BOLT HEATING SOL 26539 2 RCO 00141


EYEBOLT Ø10 ITN 33105 2 FHD 01010






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Parts List: SLO 0502835

GENERAL LIST OF THE ASSEMBLING/DISASSEMBLING TOOLS STEAM TURBINE TYPE: SAC 1-15

NAME AND USE N.P.CODE Q.TY


EYEBOLT Ø36-PF ITN 33105 2 FHD 01136


EYEBOLT Ø48-3PF ITN 33105 2 FHD 01148

SCREW Ø20 ITN 32215 2 GSB 20160

SCREW Ø56 ITN 32215 2 GSB 56650

SCREW Ø12 ITN 32215 2 GSB 12160

SCREW Ø30 ITN 34050 2 FFE 06030 THE SIMPLIFIED DRAWINGS OF THE TOOLS FOR GENERAL USE ARE INCLUDED IN THE FOLLOWING PAGES OF THIS SECTION. THE ASTERISK (*) IN THE MARGIN OF NP CODE (PARTS LIST) INDICATE “SPE-CIAL DEVICE”. THE ASSEMBLY DRAWINGS ARE INCLUDED IN THE “TURBINE DRAWINGS AND PARTS LIST”, VOLUME OF THIS MANUAL.

NOTE 1

NOTE 2


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Part List: SLO 0502853

ASSEMBLING/DISASSEMBLING TOOLS FOR CONTROL VALVES

STEAM TURBINE TYPE: SAC 1-15

NAME AND USE N.P. CODE Q.TY BUSH SOL 34755 for control valves seats assy./disassy. RBP 12918 1 PLUG ITN 33504 RTQ 21488 1


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SCREW - use: it serves for control valves ITN 32210

SAC 1-15


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BUSSOLA - uso: serve per il montaggio/smontaggio delle

sedi valvole di regolazione BUSH - use: it serves for control valves seats

assy./disassy. SOL 34755

SAC 1-15


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ATTREZZO - uso: serve per il montaggio/smontaggio della

sede valvola chiusura rapida TOOL - use: it serves for emergency stop valve seat

assy./disassy. SOL 37397

SAC 1-15


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RISCALDATORE ELETTRICO - uso: serve per il bloccaggio della bulloneria di

unione orizzontale della cassa esterna tur-bina

BOLT HEATING - use: it serves for the locking of the horizontally

union bolts and nuts of the turbine outer casing

SOL 26539

SAC 1-15


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EYE BOLTS - use: it serves for components lifting. ITN 33105

SAC 1-15

g GE Oil & Gas Nuovo Pignone Dismission and environmental impact Section 6

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DISMISSION AND ENVIRONMENTL IMPACT Contents Page - ENVIRONMENTAL IMPACT 6-1 - DISMISSION 6-2

g GE Oil & Gas Nuovo Pignone Dismission and environmental impact 6-1

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ENVIRONMENTAL IMPACT During operation, the Turbine emits vapour and/or a mixture of uncondensable gases (toxic gases such as H2S) depending on the vapour employed. The superintendent should thus evaluate the environmental impact of such emissions and take suitable measures aimed at minimising such impact. Emissions also include oil vapours produced by the lubricating fluids. Once the plant is installed and during its whole life, the user is responsible for keeping emissions within the levels established by relevant regulations in force. Waste, derived from maintenance operations, must be stocked and threated according to the local law in force and by referring, if necessary, to the safety card of the product itself (as concerns lube oils in particular) and the related filters in order to prevent any risks for the people and environment.

g GE Oil & Gas Nuovo Pignone Dismission and environmental impact 6-2

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DISMISSION According to the principles of the EN ISO 14000 standard and the ISO EN 14040, in par-ticular, about Life Cycle Assessment, GE Oil & Gas Nuovo Pignone, in the planning stage, has performed a series of devices to facilitate the reutilization and recycling of the materi-als and components of the Turbine and its auxiliary systems, and reduce the environmental impact of the product in each one of its life cycles. In case of turbine dismission, perform the following operations: - Reduce to the minimum the materials to be dumped by their reutilization and recycling

(according to the related local law in force). GE Oil & Gas Nuovo Pignone is special-ized in the recovery, reconditioning and reutilization of machines.

- Contact GE Nuovo Pignone qualified technical personnel for turbine disassembly pro-

cedures. - Recover oils and other liquids from the related tanks and dispose of them according to

the local laws in force.

instruction, operation and maintenance manual-turbine

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