500MW Turbine O&M Manual Part_1of3[1]

º]ÉÒàÉ ]®¤ÉÉ<ÇxÉ |ÉSÉÉãÉxÉ A´ÉÆ +ÉxÉÖ®FÉhÉ ÉÊxÉnæ¶É STEAM TURBINE 0PERATION & MAINTENANCE INSTRUCTIONS

NO.STETF--2 26 63 633-MS NO.STE-TF -TF -2 -MS

MEJIA - DVC 2X500 MW

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£ÉÉ®iÉ cä´ÉÉÒ <ãÉäÉÎBÉD]ÅBÉEãºÉ ÉÊãÉÉÊàÉ]äb ®ÉxÉÉÒ{ÉÖ®, cÉÊ®uÉ® BHARAT HEAVY ELECTRICALS LIMITED RANIPUR, HARIDWAR – 249403 (INDIA)

Steam Turbine General

Preface

This manual contains information on the operation and maintenance of steam turbine. The information has been prepared with the assumption that the O&M personnel have basic knowledge of power plant engineering and operation.

turbine. Bharat Heavy Electricals Limited can not be responsible for any malfunction occurring as a result of operation beyond rated limits and such operation, if undertaken by utilities, must be at their own risk.

It is an essential prerequisite for satisfactory operation and maintenance of the steam turbine that the operating and maintenance personnel are fully familiar with the design of the steam turbine plant and receive thorough training in operating and maintaining the unit.

The part numbers of components, indicated in the Description section of the manual should not be used for ordering spare parts. Please refer the chapter on Ordering of spares for spares for that purpose.

Extensive operation beyond rated design values will eventually result in increased maintenance expenses or a corresponding reduction in the useful life of the steam

Mejia-DVC,Uni Mejia-DVC,Unit-1,2 t-1,2 500 MW: Prepared by

SM

Issued by

BHEL Haridwar

VS

Effort has been made to include adequate information in this manual. For any further information or clarification please contact: Field Engineering Services, Steam Turbine Engineering, BHEL, Haridwar– 249403, Uttarakhand, India.

Document No. STE-TF-263-MS

SRP Checked by

STE (FES), BHEL, Haridwar

PCK

Approved by

Issue Date

SB

19.08.2009

5.0-0001-63

0

Steam Turbine Description

Subject

Document No

GENERAL ■

Preface

5.0-0001-63/1

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Contents

5.0-0002-63/4

Fixed points

5.1-0003-02/2

Technical Data ■

Construction, speed &

■

Steam pressure Steam and casing

5.1-0100-63/3

Casing supports and guides

5.1-0350-01/2

Control fluid system and control fluid pumps

5.1-0104-63/4

■

Limit curves: HP stop &

5.1-0110-01/1

■

control valve casing Limit curves: HP casing

5.1-0111-01/2

■

Limit curves: HP shaft

5.1-0112-01/2

■

Limit curves: IP shaft

5.1-0113-01/1

Steam purity values Oil specification standard

5.1-0120-01/1 5.1-0130-04/2

Fire resistant fluid (FRF) for turbine control system

5.1-0140-04/2

Valve arrangement

Casing Blading ■ ■

■

Shaft seals Rear bearing pedestal

5.1-0450-01/1 5.1-0460-02/1

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Journal bearing

5.1-0470-00/2

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Turnin g Gear Gear ■

5.1-0205-00/1 5.1-0210-01/3 5.1-0220-02/1

■

5.1-0240-01/2

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Rear bearing pedestal

5.1-0250-02/2

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Combined journal and thrust

5.1-0260-01/2

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bearing Journal bearing, HP front

5.1-0270-01/2

5.1-0520-01/1 5.1-0530-63/2 5.1-0600-01/2

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Start-up procedure

5.1-0610-01/2

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Speed control Electrical speed measuring

5.1-0620-01/2 5.1-0621-02/1

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Protective devices

5.1-0630-01/2

Over speed trip test

5.1-0631-01/1

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Testing of stop valves Electro hydraulic LP bypass

5.1-0632-02/1 5.1-0640-00/1

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control system (general) Electro hydraulic LP bypass

5.1-0641-00/2

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Control (electrical system) Electro hydraulic LP bypass Control (hydraulic system)

5.1-0642-00/2

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Extraction check valve

5.1-0650-01/1

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Swing check valve (CRH)

5.1-0651-01/1 5.1-0651-01/ 1

Testing of check valves in cold reheat line

5.1-0652-02/1

Automatic turbine tester

5.1-0660-00/1

■

■

general Automatic turbine tester for protective devices

5.1-0661-00/7

Automatic turbine tester stop and control valves

5.1-0662-01/4

HP actuator

5.1-0665-00/1

Electro hydraulic seal steam pressure control

5.1-0670-01/4

■

Governing scheme

5.1-0680-05/1

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Control system diagram

■

■

5.1-0280-01/2

■ ■

Casing

5.1-0310-01/3

Blading

5.1-0320-02/1

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Shaft seals

5.1-0330-01/2

■

Rear bearing pedestal

5.1-0340-02/1

BHEL Harid Harid war

Manual turning gear Hydraulic lifting device General description

■

piston Front bearing pedestal

■

5.1-0510-01/1

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■

5.1-0230-01/2

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Hydraulic turning gear

Control System 5.1-0103-63/2

Shaft seals and balance

Casing supports and guides IP Turbin e

5.1-0420-00/1 5.1-0430-01/1 5.1-0440-01/2

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■

■

Atmospheric relief Blading, drum stages Blading, LP stages

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HP Turbi Turbi ne ■

5.1-0410-00/4

diaphragm

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5.1-0102-63/1

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■

5.1-0101-63/2

Bearing metal temperatures, vibration, weights Oil supply, oil pumps

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5.1-0345-01/2

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temperatures

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Journal bearing IP rear

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■

■

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Brief Description ■

■

Document No

DESCRIPTION

5.1-0001-04/1 5.1-0002-04/2

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Subject

LP Turbine Casing ■

Sectional arrangement General description

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Contents

5.1-0681-01/5 5.1-0681-05/5

legend

5.0-0002-63/1

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Subject

Document No

Lubrication chart

5.1-0690-05/3

Control System Parts

■ ■

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Hydraulic speed governor with

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starting and load limiting device Adjusting gear

5.1-0710-00/2 5.1-0720-00/1

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Electro hydraulic converter

5.1-0730-02/3

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for turbine control system Hydraulic amplifier for

■ ■ ■

■

turbine control system ■ ■

Electrical speed pick-up Pressure converter

5.1-0760-01/1 5.1-0761-00/1

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Main oil pump with hydraulic

5.1-1020-01/2

Test valve for emergency stop valve

5.1-0813-00/1

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■

Combined reheat stop &

5.1-0814-00/2

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control valves Hangers for reheat stop &

■ ■ ■

main & reheat control valves

speed transmitter

5.1-0815-01/1

■

■ ■

■ ■

5.1-1050-00/2

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Oil throttle Oil throttle

5.1-1080-00/1 5.1-1081-00/1

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Three way control valve for

5.1-1090-01/1

5.1-0840-00/1

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5.1-1110-00/1

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LP extraction Plate-type filter

5.1-1120-00/1

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Duplex filter for pilot control

5.1-1130-00/3

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of control valves Regenerating plant

5.1-1140-00/3

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Drain system (MAL)

5.1-1210-63/2

System diagram index Component diagram index

5.1-1220-63/3 5.1-1230-63/11

Shaft seal system Operation

5.1-1240-63/5

5.1-0841-00/2 5.1-0853-01/1

Pilot valve for rotary vane

5.1-0854-00/1

reheat swing check valve Gland steam control valve

Jacking oil pump

Control Fluid Supply HP control fluid pump with

Rotary vane actuator for reheat swing check valve

Auxiliary pilot valve for rotary vane actuator of

■

Lubricating oil temp. control

actuator of swing check valve ■

5.1-1030-01/1 5.1-1040-01/1

5.1-0816-00/1

check valve ■

■

Auxiliary oil pump DC emergency oil pump

■

control valves

■

5.1-0855-00/1

Other Systems ■ ■ ■

5.1-0860-01/1

Leakage steam control valve Protective Devices

5.1-0870-01/1

Main trip valve Emergency trip valve for

5.1-0910-00/2 5.1-0911-00/1

Introduction Specification Specification of steam, oil & ■ ■

■

manual trip out ■

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control fluid Testing of turbine

5.2-0001-01/1 5.2-0002-00/1 5.2-0020-00/1

Components - General

Solenoid valve for remote trip out

5.1-0912-00/1

■

Over speed trip

5.1-0920-00/1

□

Turbine systems testing testing intervals

Controllers

□

5.0-0002-63/2

5.1-0980-00/1

■ ■

bleeder check valve Auxiliary valve of extraction

Changeover valve for testing device

5.1-1003-63/1 5.1-1010-01/2

5.1-0812-00/2

■

5.1-0960-02/2 5.1-0970-00/2

Oil purification purifica tion system Main oil tank

Hydraulic servomotor for

valve Changeover valve for

Vacuum breaker Pressure switch for injection

5.1-1001-63/2 5.1-1002-63/2

5.1-0811-00/1

Steam strainer

5.1-0940-00/1 5.1-0950-00/1

Oil vapor extraction system Oil discharge & vent system

Servomotor for main & reheat stop valves

■

5.1-0935-00/1

5.1-1000-63/4

5.1-0810-01/2

■

Low vacuum trip Condenser safety device Solenoid valve for tempera-

Oil supply system

■

Combined main stop and control valve

■

5.1-0921-00/2 5.1-0922-00/2

Oil Supply

accessories

■

Over speed trip releasing device Over speed trip test device

water

Steam Steam valves and ■

Document No

ture controlled interlock ■

5.1-0740-02/3

Subject


5.2-0021-01/1 5.2-0022-01/1

□ □ □

Subject

Document No


5.2-0023-01/1

Protective devices Safety devices

5.2-0024-01/1 5.2-0025-01/1

Valves

□

■ ■

■

■

Monitoring devices

5.2-0027-01/1 5.2-0027-01/ 1

■

Operating parameters Start-up

5.2-0028-01/1

■

Starting the turbine

5.2-0110-01/1

Startup & shutdown diagrams, symbols

5.2-0111-00/1

General Preparation for startup □

5.2-0112-00/2 5.2-0113-00/1 5.2-0120-00/1

□

manually operated valves Oil System & Turning Gear

5.2-0130-02/5

□

Control fluid system

5.2-0135-02/4

start-up diagram □

Condensing Plant Bypass System

□

Warm-up & startup of turbine 5.2-0160-02/6

Temperature criteria Controllers □

5.2-0440-01/2 5.2-0450-01/7

Automatic turbine turbine tester

5.2-0455-00/9

■

Oil system Control fluid system

5.2-0460-00/6 5.2-0470-00/3

■

Gland steam system

5.2-0480-01/1

■

Introduction Inspection schedule

■

Maintenance schedule

■

Operating position of

□

5.2-0430-01/5

MAINTENANCE

□

□

Turbine stress controller: measures to avoid Stop & control valves Protective devices

■

Startup diagram

□

Document No

impermissible operation

5.2-0026-01/1

□ □

■

Subject

5.2-0140-02/4 5.2-0150-00/3 5.2-0170-01/4 5.2-0180-00/4

Turbine Oil system, seal steam □ □

5.3-0001-01/1 5.3-0010-04/3 5.3-0021-02/1 5.3-0022-01/3

system, drains ■

FRF system Testing during start-up

5.3-0023-01/2 5.3-0030-02/7

■

Testing during power

5.3-0035-02/5

operation Acquisition & archiving of

5.3-0037-03/3

□

■

operating data ■

Remedial actions for off-

5.3-0040-01/6

■

normal operating conditions Measurement of internal

5.3-0050-02/3 5.3-0060-01/5

On-load On-load Running ■

Load operation, Introduction Synchronization and loading

5.2-0200-00/1 5.2-0210-00/5

■

Power operation, controllers

5.2-0220-00/9

■

efficiency Testing during shut down

Actions to prevent unallowable heat-up

5.2-0230-00/4

■

Testing during standstill

5.3-0061-02/6

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Testing of safety valves

5.3-0062-01/1 5.3-0063-00/2 5.3-0064-01/4

■

■

through blade wind age

■

Shut-down

■

Testing of signaling devices Testing of TSC

■

Steam washing of turbine

5.3-0070-02/3

■

Turbine Oil care Grease and Oil lubrication

5.3-0080-03/11 5.3-0081-00/1

■

Care of control fluid

5.3-0082-02/9

Determination of FRF purity

5.3-0083-01/2

Vibration dampers Instructions for overhaul

5.3-0100-00/2 5.3-0200-05/8

Turbine restart after boiler repairs

5.3-0210-00/1

Turbine restart after major

5.3-0220-00/3

■

Introduction Shutdown diagram ■

5.2-0300-00/1

General □ Turbine-generator □

5.2-0310-01/1 5.2-0320-02/5

□

Condensing plant

5.2-0330-01/2

■

□

Oil system

5.2-0340-01/2

■

Fast cooling down of turbine Preventing corrosion in

5.2-0350-01/1 5.2-0360-00/2

■ ■

■

■ ■

idle turbine ■

Fault Tracing Introduction

5.2-0400-00/1

■

Serious faults

5.2-0410-00/8

■

■

Vibration

5.2-0420-00/5

□

Bearing temperature Casing temperatures

5.2-0421-01/1 5.2-0423-02/2

■ ■

■

inspections or repairs 5.3-0250-00/1 5.3-0251-00/1

safety notice □ ■

5.0-0002-63/4

Environmental protection Fluorelastomer products Safe disposal of turbine oil Ordering of spares

5.3-0252-00/1 5.3-0300-00/1


BHEL Haridwar

Cross Sectional Arrangement

5.1-0001-04

Steam Turbine General

Preface

This manual contains information on the operation and maintenance of steam turbine. The information has been prepared with the assumption that the O&M personnel have basic knowledge of power plant engineering and operation.

turbine. Bharat Heavy Electricals Limited can not be responsible for any malfunction occurring as a result of operation beyond rated limits and such operation, if undertaken by utilities, must be at their own risk.

It is an essential prerequisite for satisfactory operation and maintenance of the steam turbine that the operating and maintenance personnel are fully familiar with the design of the steam turbine plant and receive thorough training in operating and maintaining the unit.

The part numbers of components, indicated in the Description section of the manual should not be used for ordering spare parts. Please refer the chapter on Ordering of spares for spares for that purpose.

Extensive operation beyond rated design values will eventually result in increased maintenance expenses or a corresponding reduction in the useful life of the steam

Mejia-DVC,Uni Mejia-DVC,Unit-1,2 t-1,2 500 MW: Prepared by

SM

Issued by

BHEL Haridwar

VS

Effort has been made to include adequate information in this manual. For any further information or clarification please contact: Field Engineering Services, Steam Turbine Engineering, BHEL, Haridwar– 249403, Uttarakhand, India.

Document No. STE-TF-263-MS

SRP Checked by

STE (FES), BHEL, Haridwar

PCK

Approved by

Issue Date

SB

19.08.2009

5.0-0001-63

Steam turbine Description

General Description

Construction, Steam Flow

LP Turbine

The turbine is a tandem compound machine with separate HP,IP and LP sections. The HP section being a single-flow cylinder and the IP and LP sections double-flow cylinders. The turbine rotors and the generator rotor are connected by rigid couplings. The HP turbine is throttle controlled. The initial steam is admitted ahead of the blading via two main stop and control valve combinations. A swing check valve is installed in the line leading from HP turbine exhaust to the Reheater to prevent hot steam from the reheater flowing back into the HP turbine. The steam coming from the Reheater is passed to the IP turbine via two reheat stop and control valve combinations. Cross around pipes connect the IP and LP cylinders. Connections are provided at several points of the turbine for feedwater extraction purpose.

The casing of the double-flow LP cylinder is of three-shell design. The shells are horizontally split and are of rigid welded construction. The innermost shell, which carries the first rows of stationary blades, is supported so as to allow thermal expansion within the intermediate shell. The intermediate shell rests at four points on longitudinal girders, independent of the outer shell. Guide blade carriers, carrying the last stationary blade rows are also attached to the intermediate shell.

HP Turbine, Barrel Type Casing The outer casing of the HP turbine is of the barrel type and has neither an axial nor a radial flange. his prevents mass concentration which would have caused high thermal stresses. The almost perfect asymmetric design of the casing permits moderate and nearly uniform wall thickness at all sections. The inner casing is axially split and supported so as to be free to move in response to thermal expansion. As only slight pressure differences are effective, the horizontal flange and joint bolts of the inner casing can be kept small. The barrel type casing permits flexibility of operation in the form of short start-up times and a high rate of change of load even at high initial steam conditions.

IP Turbine The IP turbine section is of double flow construction with horizontally split casings. Allowance is made for thermal movement of the inner casing within the outer casing. The inner casing carries the stationary blading. The reheated steam enters the inner casing from top and bottom. The provision of an inner casing confines high steam inlet conditions to the admission section of this casing, while the joint flange of the outer casing is subjected only to the lower pressure and temperature effective at the exhaust from the inner casing. BHEL Haridwar

Blading The entire turbine is provided with reaction blading. The stationary and moving blades of the HP and IP sections and the front rows of the LP turbine are designed with integrally milled inverted T -roots and shrouds. The last stages of the LP turbine are fitted with twisted drop -forged moving blades with fir-tree roots engaging in grooves in the shaft with last stage stationary blades made from sheet steel.

Bearings The HP rotor is supported on two bearings, a journal bearing at its front end, and a combined journal and thrust bearing immediately next to the coupling to the IP rotor. The IP and LP rotors have a journal bearing each at rear end. The combined journal and thrust bearing incorporates a journal bearing and a thrust bearing which takes up residual thrust from both directions. The bearing metal temperatures are measured by thermocouples directly under the babbit lining. The temperature of the thrust bearing is measured in two opposite thrust pads. The bearing pedestals are anchored to the foundation by means of anchor bolts and are fixed in position. The HP and IP turbines rest with their lateral support horns on the bearing pedestals at the turbine centerline level. The HP and IP casings are connected with the bearing pedestals by casing guides, which establish the centerline alignment of the turbine casing. The axial position of the HP and IP casings is fixed at the support brackets on HP-IP bearing pedestal.

5.1-0002-04/1

The fixed point for the LP casing is at the front point of support on the longitudinal girder. Thermal expansion of the casings originates from the fixed points. Shaft Seal and Blade Tip Sealing All shaft seals, which seal the steam in the casings against atmosphere, are axial-flow type. They consist of a large number of thin seal strips which, in the HP and IP turbines are caulked alternately into grooves in the shafts and the surrounding seal rings. In the LP turbine, the seal strips are caulked only into the seal rings. Seal strips of similar design are also used to seal the radial blade tip clearances.

Valves The HP turbine is fitted with two main stop and control valves. One main stop valve and one control valve with stems arranged at right angles to each other are combined in a common body. The main stop valves are spring-action singleseat valves; the control valves, also of singleseat design, have diffusers to reduce pressure losses. These valve combinations are located at both sides of the turbine with their stems horizontal. The HP valves are connected to the turbine by easily separable collar couplings, which contain self-sealing U-rings as sealing elements. The IP turbine has two reheat stop and control valves. The reheat stop valves are spring-action single-seat valves. The control valves, also spring-loaded, have diffusers. The control valves operate in parallel and are fully open in the upper load range. In the lower load range, they control the steam flow to the IP turbine and ensure stable operation even when the turbinegenerator unit is supplying only the station load. The reheat stop and control valves are supported free to move in response to thermal expansion on the foundation cover plate below the operating floor and in front of the turbinegenerator unit. All valves are actuated by individual hydraulic servomotors.

Turbine Control System The turbine has an electrohydraulic control system. An electric system measures speed and output and controls them by operating the control valves hydraulically via an electrohydraulic converter. The electrohydraulic controller ensures controlled acceleration of the turbine-generator up to rated speed and limits speed overshoot in the event of sudden load rejection. The linear power frequency droopcharacteristic can be adjusted in fine steps even when the turbine is running.

Turbine Monitoring System In addition to measuring and display instruments for pressure, temperatures, valve lifts and speed, the monitoring system also includes instruments for measuring and indicating the following parameters: 

 



Rotor expansion measured at the rearbearing pedestal of the LP turbine Axial shift measured at the HP-IP pedestal Bearing pedestal vibration, measured at all turbine bearings Shaft vibration measured at all turbine bearings

Oil Supply System A common oil supply system lubricates and cools the bearings . The main oil pump is driven by the turbine shaft and draws oil from the main oil tank. Auxiliary oil pumps maintain the oil supply on start-up and shutdown, during turning gear operation and when the main oil pump is faulted. DC Emergency oil pump supplies oil to the bearings during AC power failures. A Jacking oil pump forces high-pressure oil under the shaft journals to prevent boundary lubrication during turning gear operation. The Jacking oil pump also supplies the high pressure oil to the Hydraulic Turning gear motor. The lubricating and cooling oil is passed through oil coolers before entering the bearings. The control fluid pumps situated on a control fluid tank supply the hydraulic turbine and bypass control system and the protective devices and valve actuators with HP and LP control fluid.

5.1-0002-04/2

Steam Turbine Description Design of the supports for the turbine has to allow for the expansion of the turbine during thermal cycling. Constrained thermal expansion would cause overstressing of the components. The method of attachment of the turbine components is also critical to the magnitude of the differential expansion between the rotor and turbine casings which is given careful attention in the determination of internal clearances.

The following components form the fixed points for the turbine: The HP, IP and LP turbine bearing bearing pedestals IP  The horn supports of the HP and turbine at HP- IP Pedestal of the  At turbine end of longitudinal girder LP Turbine The thrust bearing in the HP turbine rear  bearing pedestal 

Casing Expansion The bearing pedestals are anchored to the foundation by means of anchor bolts and are fixed in position. The HP and IP turbines rest with their lateral support horns on the bearing pedestals at the turbine centerline level. The HP and IP casings are connected with the bearing pedestals by casing guides which establish the centerline alignment of the turbine casings. The axial position of HP and IP casings is fixed at the HP-IP pedestal. Thermal expansion of the casings originates from the fixed points. The LP Turbine outer casing is held in place axially, at turbine end of longitudinal girder by means of fitted keys. Free lateral expansion is allowed.

BHEL, HARIDWAR

Fixed Points Centering of LP outer casing is provided by guides which run in recesses in the foundation cross beam. Axial movement of the casings is unrestrained. Hence, when there is a temperature rise, the outer casings of the HP turbine expand from their fixed points towards Front pedestal. Casing of IP Turbine expand from its fixed point towards the generator. LP Casing expands from its fixed point at front end, towards the generator.

Rotor Expansion The thrust bearing is housed in the rear bearing pedestal of the HP turbine. The HP turbine rotor expands from the thrust bearing towards the front bearing pedestal of the HP turbine and the IP turbine rotor from the thrust bearing towards the generator. The LP turbine rotor is displaced towards the generator by the expansion of the shaft assembly, originating from the thrust bearing. Differential Expansion Differential expansion between the rotors and casings results from the difference between the expansion of rotor and casing originating from the HP-IP pedestal. The largest differential expansions of the HP and IP turbines thus occur at the ends farthest from the thrust bearing. Differential expansion between the rotor and casing of the LP turbine results from the difference between the expansion of the shaft assembly, originating from the thrust bearing and the casing expansion, which originates from the fixed points on the LP turbine longitudinal beams.

5.1-0003-02/1

solenoid valve so that the auxiliary trip fluid circuit is connected to drain. Trip initiation is monitored downstream of the main trip valves by pressure switches MAX51CP209 and MAX52CP211 in the auxiliary trip fluid circuit. In addition, the limit switch of each main trip valve must annunciate successful completion of the test. Latching -in On successful completion of testing, remote trip solenoids MAX52AA001 and MAX52 AA002 are de-energized. The reset program is then started.

drain, thereby depressurizing it. The loss of auxiliary trip fluid pressure causes the main trip valve to drop which in turn causes the trip fluid pressure to collapse. To activate the over speed trip at rated speed, as the test routine performed by the automatic turbine tester requires, a specific force, equivalent to the increase in centrifugal force between rated speed and preset trip over speed, is needed .For testing, this force is exerted by the test oil pressure, acting on the flybolt /striker (2) .On the basic of the existing defined geometry, the test oil is reproducible measure for the trip speed, and can therefore be used to check whether the over speed trip responds at the desired setting.

Overspeed Trips

Test Sequence

MAY10AA001/MAY10AA002

The test oil pressure is produced using the hydraulic test signal transmitter, which is also used for manual testing. First the command is given to the actuator motor to go into the trip position (down). After a certain idling time, the test oil pressure builds up to act on the two over speed trip flybolts/strikers (2).

Function The two over speed trips are provided to protect the turbine against over speeding in the event of load rejection coincident with failure of the speed controller. As they are particularly important to the protection of the turbine, they can also be locally tested by manually with the aid of the over speed trip test device MAX62AA001 (hydraulic test signal transmitter) during turbine operation at rated speed. (For description see Over Speed Trip Test ). ).

Operation When the preset over speed is reached, the eccentric flybolt/striker (2) of each over speed trip activates piston (5) and limit switch (6) annunciate via pawl (4). This connects the auxiliary trip fluid circuit to

If the two bolts are functioning correctly, they will fly outwards into the trip position when the defined pressure is reached, thereby activating the main trip valve via pawl (4), piston (5) and the auxiliary trip fluid circuit. The two over speed trips are monitored for activation at the given test oil pressure by

the two pressure switches MAX62CP211 and MAX62CP212 in the test oil line, and the limit switch (6). Pressure switches MAX 62CP211 and MAX62CP212 are preset to respond at a certain level (approx.O.15 bar) below and above the test oil reference

5.1-0661-00/5

pressure respectively. This test oil reference pressure is determined during commissioning and entered in the commissioning test record. Limit switch (6) must respond within the pressure range between the settings of pressure switches MAX62CP211 and MAX62CP212. A slow buildup of pressure is required for this operation, that is why a relatively long monitoring period equivalent to the running time of the actuator, has to be selected. Premature response of the over speed trips is annunciated. Latching-in Once the trip has been initiated, the actuator of the hydraulic test signal transmitter is driven back until the limit switch annunciates that normal position has been reached. Monitoring must be continued until the test oil pressure at pressure switch MAX62 CP213 is less than 0.1 bar.

operation, the pressure in the condenser exceed a preset valve.

turbine

Operation When the condenser pressure exceeds the adjusted limit, the piston (6) is moved downwards by this pressure, which acts against diaphragm {4), and the spring force (3). Thereby pressure below piston (7) drops and this piston moves in its lower end position by spring force connecting the auxiliary trip fluid circuit to the drain. The resultant depressurization of the auxiliary trip fluid circuit actuates main trip valves MAX51AA005 and MAX51AA006, thereby closing all turbine valves.

This double check-back of the hydraulic test signal transmitter having returned to normal position ensures that, after completion of testing, the over speed at which the turbine will trip is not reduced due to test oil pressure remaining effective and that the over speed trip will not be set off prematurely in the event of load reduction. While test oil pressure is decreased, the two over speed flybolts/strikers spring back into their normal positions at a pressure well above 0.5 bar. Subsequently, piston (5) is brought back into its normal position by the pressure of auxiliary start-up fluid II and latched-in with pawl (4). At the same time, piston (5) shuts off drain channel IV, so auxiliary trip fluid III can build up pressure. Once this has been done, the auxiliary start-up fluid can be depressurized.

Low Vacuum Trip MAGO1 AAO11 Function The function of the low vacuum trip is to operate the main trip valve if, during normal

5.1-0661-00/6

Test sequence After energizing of test signal transmitter (solenoid valve) MAG01AA201, fitted in the signal line to the condenser, this signal line is blocked off and simultaneously the space above diaphragm (4) is connected to atmosphere. The air flow via orifice causes a slow increase of pressure by which the pistons (6) and (7) move to their trip position connecting the auxiliary trip fluid circuit to the drain.

The low vacuum trip is monitored for operation within the specified vacuum range by observing pressure switches MAG01 CP202 and MAG01CP204. Latching-in When test signal transmitter (solenoid valve) MAG01AA201 has been de-energized and the connection between low vacuum trip and the condenser re-established, condenser pressure builds up again above diaphragm (4). Piston (6) moves into its upper end position thereby opening the passage for the control fluid flow to piston (7). When piston (7) is in its upper end position, the auxiliary trip fluid circuit is closed again. Restoration of normal operating configuration is annunciated by the limit switch of the low vacuum trip and by pressure switches MAG01CP201

Dispersion of the auxiliary start-up fluid pressure is monitored by pressure switch MAX48CP201. The second reset solenoid MAX48 AA202 is then de-energized to disperse the pressure between the twosolenoid valves. This is monitored by pressure switch MAX48 CP202. The use of two reset solenoids ensures that main trip valve MAX51AA005 and MAX51AA006 and over speed trip will always be sure to be actuated if either one of the two reset solenoids is de-energized.

Reset Solenoids MAX48 AA201 and MAX48 AA202 Function The function of the reset solenoids is to restore the tripped protective devices to their normal operating positions during the ATT reset program. Operation The reset solenoids are two 2/3-way solenoid valves, fitted in the auxiliary startup fluid line. Both solenoid valves are energized in the course of the reset program conducted after each subtest, so that auxiliary start-up fluid II is supplied with control fluid III. The control fluid pressure forces all protective devices back into their normal operating positions and the trip fluid and auxiliary trip fluid pressure can build up again. When the protective devices have latched-in again, reset solenoid MAX48AA021 is deenergized first to shut oft the control fluid supply through this value.

1 Compression spring 2 Coil 3 Valve disc

I Aux. start-up fluid II Aux. start-up fluid to protective devices III Control fluid

Fig. 7 –Reset Solenoid

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The following description refers to a standard stop and control valve assembly. The same text applies analogously to both the main stop and control valves and the reheat stop and control valves. The valve assembly described is drawn in the closed position (ready for start-up). General The stop and control valves of the turbine are the final control elements actuated by the protective devices arid it is, therefore, equally important that these, as well as the protective devices, should function reliably. The testing of these valves in conjunction with testing of the protective devices, as already described in Automatic Turbine Tester, General ensures that all elements which must respond on turbine trip are tested for their ability to function reliably. Each stop valve is tested together with its associated control valve. The automatic turbine tester is designed so that only one valve assembly may be selected and tested at any time. Test Requirements To avoid turbine output changes and initial pressure variations due to the closing of the control valve under test during ATT, the electro-hydraulic turbine controller must be in operation prior to testing. To facilitate compensation by the controller, the closing time of the control valves is relatively long, and to enable initial pressure to be maintained constant, testing is only permissible when the turbine output is below a certain value. Special Conditions during Testing The main stop and control valves may only be tested if no other ATT subgroup is running. During testing the selected control valve (MAA10+20AA002) is closed completely

BHEL Hardwar

Automatic Turbine Tester Stop and Control Valves

by means of a motor operated actuator (-AA002M) acting on pilot piston (KA06) parallel to pilot value (KA05). This result in a closing movement simulating that which occurs when the associated secondary fluid pressure drops. The resultant, constant slow closing movement is necessary in order to keep the output constant. Thus the conditions for actuation of the valve are the same during testing as during normal actuation by the controller. The stop valves, which are held in the open position by trip fluid pressure during normal operation, are subjected to exactly the same hydraulic conditions during testing as would be the case in the event of actual turbine trip, as the action of the protective devices is simulated by the solenoid valve (MAX61AA211 and 212). The steam side conditions during testing are somewhat more severe than during actual trip, as the pressure downstream of the stop valve can not drop off during closure because the control valve is closed. This means that the steam pressure acting against the spring closure force is greater than in the event of normal trip. The automatic turbine tester intervenes only in the fluid circuits normally used to control the valves and uses only trip fluid to actuate the test valves (MAX47AA011 and 012) and to reset and open the stop valves. Thus closure of the valves cannot be impeded in the event of a genuine trip during testing, regardless of the stage, which the test has reached. This also applies to the control valves, as the ATT does not interrupt the secondary fluid circuit and secondary fluid can thus be depressurized in the normal manner in the event of a trip. Features of Automatic Turbine Tester The ATT has the following features: 

Separate part-testing of each valve assembly.

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Time-related monitoring of all program steps, and their implementation.









Interruption due to running exceeded or turbine trip.

time

Automatic reset of test program after a fault. Protection of the turbine during testing provided by special test protective circuits.

Setting Data The setting data for the pressure switches used to monitor the individual valve movements are listed in the setting record Pressure Switch settings . The actual set values are logged in the Commissioning Test Record . The test running times, etc., are entered in the functional diagram. Test Selection Units There are two nos. of combined main steam and control valves” and two nos. of combined reheat stop and control valves, each of which is tested as a separate unit and has a separate selection push-button on the ATT control panel. They are as follows: Selection1: Main stop and control valve (LHS) Selection 2: Main stop and control valve (RHS) Selection 3: Reheat stop and control valve (LHS) Selection 4: Reheat stop and control valve (RHS) Test Procedure Start of Test The test starts with the selection of subgroups by pressing the On/Off pushbutton. The subgroup remains on until it is switched off after the programme is

5.1-0662-01/2

concluded. When one subgroup program is running, the other subgroup is blocked. The On/Off push acknowledges signals:

button

also

Selection If the test requirements have been fulfilled, the valve, assembly (e.g. main stop and control valve (LHS)) to be tested is selected by switching in the subgroup by pressing title selection push-button. A separate selection push-button is provided for each combination of stop and control valve assembly. Only one selection may be made at a time. Selection of a further test is not possible until the programme already selected has ended. Operation Push-button The test run is started by pressing the Operation push- button in the Stop and Control valves valves tile. Shutdown Push-button This push-button can abort the current unit test and introduce the reset program, which has priority over the test programme. Lamp Test Push-button All lamps on the panel are tested by pressing the Test push-button. Test push-button. Closure of Control Valve If all the test requirements have been fulfilled and the selection and operation push buttons pressed, the control valve (MAA10 and 20AA002) is closed by means of the associated actuator (test motor –AA002M). Operation of the actuator (KA01) is continued until limit switch (-CG002C) and limit switch (AA002M S72, S73) on the actuator is tripped to annunciate that the control valve being tested is in closed position.

During this time, the turbine output controller compensates for the effects of closure of the valve being tested on the turbine output by opening the remaining control valves. The running time for closure of the control valve is monitored. If the control valve is functioning properly, it will close within the preset running time. Closure of Stop Valve Then the solenoid valve (MAX61AA211 and 212) energized. This allows trip fluid to flow to the space below changeover slide valve (MAX61AA011 and 012), which moves into its upper end position and connects the space below piston disc (KA02) with the drain. The pressure in this space drops rapidly and is monitored by pressure switch (MAX51CP223,228). When the pressure at this pressure switch has dropped slightly below the breakaway pressure of piston disc (KA02), monitoring of the stop valve closure time starts. The associated limit switch (-CG001E) annunciates entry of the valve into its position, thus making it possible to closed position, monitor the valve closing action for completion within the maximum permissible running time. Opening of Stop Valve Next, solenoid valve MAX47AA211 and 212 is energized (test position) and trip medium is admitted to the control surface of the piston in the test valve MAX47 AA011 and 012. The pilot moves into its lower end position against the spring force, thus permitting trip medium to flow to the space above piston KA01 of the stop valve. This piston is forced downwards by pressure of the medium, thereby tensioning the spring between piston KA01 and piston disc KA02 and finally pressing against piston disc KA02. Up to this point the medium pressure above piston KA01 is relatively low, being equal to the spring force acting against it. The spontaneous pressure rise when piston KA01 has made contact with piston disc KA02, and thus on completion of the spring tensioning action, is detected by

pressure switch MAX51CP222, 227. If all conditions are fulfilled within this relatively long monitoring period, solenoid valve MAX61AA211 and 212 is de-energized (operating position), so that trip medium is once again able to flow to test valve MAX47AA011 and 012 and the drain is blocked off again. The buildup of trip medium pressure is monitored by pressure switch MAX51CP221, 226. When the pressure is sufficiently high, the stop valve is opened by de-energizing solenoid valve MAX47AA211 and 212 (operating position). Test valve MAX47 AA011 and 012 switches over, admitting trip medium to the underside of the piston disc KA02 and after a certain amount of further travel, slowly connects the space above piston KA01 with the drain. The resultant pressure difference causes the tensioned piston relay to open the stop valve. As soon as the open position is reached, the full trip medium pressure builds up. This is monitored by pressure switch MAX51CP221, 228 and by limit switch –CG001D. Testing of the stop valve is now completed. Re-Opening of Control Valve If the conditions are fulfilled within the specified monitoring period, the control valve is reopened. The motor of positioner –AA002M is operated in the opening direction. Positioner –AA002M moves the control valve into its original position in the reverse sequence to the closing action. Again the initial pressure and output are kept constant by the appropriate controller. Operation of positioned -AA002M is continued until, after a certain amount of over travel, it has positively ceased to influence the controller. This position is detected by limit switch –AA002 MS61 or –AA002 MS62. If the control valve is functioning properly, it will open within the preset running time. Cancellation of Selection On conclusion of testing of each combination of valve assembly, the selection is automatically cancelled and the programme is shut down.

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Interruption Exceeded

due

to

Running

Time

The reset program is automatically initiated if the running time for any step in the test program is exceeded. If any running time is exceeded during the reset program, the program halts. In either case, the alarms Fails signal and and Time overrun generated. If the Faults in ATT alarm is displayed, the fault lies in the automatic tester itself.

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Interruption due to Turbine Trip If electrical turbine trip is initiated during testing, all solenoid valves are deenergized and positioner –AA002M is returned to its extreme position and the programme cancelled. All equipments associated with the automatic turbine tester are automatically returned to their normal position.

Steam Turbine Description The actuator is of the two-stage amplification type, i.e. it incorporates pilot and main control mechanisms. The actuating forces for movement of the HP control valve are generated, in the opening direction, by main actuator piston KA02 under the force of the control fluid and, in the closing direction, by the disc spring column. During actuation main pilot valve KA07 acts as a 3-way valve to allow the control fluid to flow to the space behind main actuator piston KA02. Main pilot valve KA07 is actuated via the resetting linkage by means of auxiliary pilot piston KA06 which is subject to control fluid pressure on both sides. The actuating signal given by the signal fluid pressure acts on the face of pilot valve KA05 pressing it against the resetting spring on the opposite side. Acting as a 4-way valve, the pilot valve allows fluid to flow to both sides of auxiliary pilot piston KA06. When

BHEL Hardwar

HP Actuator

the signal fluid pressure changes, pilot valve KA05 is displaced which results in movement of auxiliary pilot piston KA06. The movement of piston KA06 is transmitted via the resetting linkage of the pilot mechanism to the resetting spring, causing spool valve KA05 to return to the central position which establishes proportionality between the signal fluid pressure and the travel of auxiliary pilot piston KA06. At the same time, main pilot valve KA07 displaced via the resetting linkage system by auxiliary pilot piston KA06, effects displacement of main actuator piston KA02 whose movement returns main pilot valve KA07 to the central position via the resetting mechanism. Consequently the position of the pilot and main actuator pistons are proportional to the secondary fluid pressure in the steady state (on completion of the control action).

5.1-0665-00


Function With all shaft seals subject to a positive pressure difference, the escaping steam is throttled to a low pressure and fed into a header 1.1, which is common to all shaft seals. Those seals, which are under vacuum, must be supplied with seal steam to prevent the ingress of air. The supply of steam is taken from the header 1.1. The amount of leakage steam and seal steam required depends on the pressure at the seals, which, in turn, is primarily dependent on the turbine load. The function of the control system is to maintain the pressure at the bleed-off points of all seals at the same preset pressure. This is effected by exhausting steam from the header (e.g. to the condenser) or supplying extra steam to the header 1.1, according to operating conditions. Arrangement Leak-off control valve 1.3 is used for discharging surplus steam from the header 1.1 and seal steam supply control valve 1.4 for admitting extra steam to it. All valves are actuated by type HSA-1-K electro hydraulic actuators. The actuators 1.11 are under the continuous control of an electric controller 1.9 each via an electro hydraulic converter. The electro

BHEL Hardwar

Electro-hydraulic Electro-hydraulic Seal Steam Pressure Control hydraulic converter comprises a control coil, which adjusts the position of the impingement plate of the hydraulic preamplifier. Controller The function of the electric controller 1.9 in conjunction with the transducer 1.6 and the actuating elements (control valves) is to maintain a controlled variable at a preset valve by adjusting the final controlling elements. The actual valve of the control system is acquired continuously by the transducer 1.6 and compared against the set value in the electric controller 1.9. If the actual value deviates from the set value, one of the final controlling elements (either the leakoff or steam supply control valve) is adjusted until the actual value again agrees with the set value. Only if there is a large control deviation, e.g. during a fullload trip, are all valves operated simultaneously. The electric controller is realised in digital technology. Mode of Operation The input signal coming from the controller flows through the solenoid (31). The magnetic field of the solenoid together with the magnetic field of the permanent magnet system (42) exercises a force on the freely pivoted armature (30). This force reacts against the force generated by b y the

5.1-0670-01/1

tension of the return spring. If the input signal is changed, the equilibrium will be disturbed and, therefore, there will be a deflection of the armature retained by the spring (32) and return spring (36). The baffle plate (29) then covers the tworebound nozzle tips (15) to an unequal extent. In the oil flow that flows through two-choke valves (21) to the rebound nozzles (16), a pressure differential is created. The oil pressure existing in the rebound nozzles is applied to the face of the slide gate (1a). The slide gate is deflected and releases the oil flow to or from the hydraulic cylinder (5.1). The deflection of the slide gate is dependent

5.1-0670-01/2

upon the magnitude of an input signal change. The greatest amount of deflection and, therefore, the fastest change in the Hydraulic cylinder’s position is already achieved with an input signal change of delta I ≥ 3 mA. Following smaller changes in signal, the hydraulic cylinder operation is correspondingly slower. The servo-valve enables an extremely sensitive control by virtue of its special construction. The main cylinder piston moves and in so doing changes the position of the coupled actuator. At the same time, the tension in the return spring (36) changes via the return rod (44) and the adjustment lever

5.1-0003-02/2

(39), until the tension of the springs and magnetic forces reach a state of equilibrium. The armature returns to its mid position, the pressures on the faces of the slide gates (1a) are of equal magnitude. The slide gate moves to its mid position, the oil flow to the cylinder is initially reduced and, when the slide gate (1a) reaches its middle setting it is completely shut off, and the main piston of the hydraulic cylinder is in its set position. The position of the main piston or rather the actuator is directly proportional to the input signal on the servo valve. Double Blocking Valve

A double blocking valve is connected to the outlet side of the servo-valve. The pump pressure opens the hydraulically operated check valve (8). the connections to the hydraulic cylinder (5.1) are free. If the oil supply fails, both hydraulically operated check valve close. The hydraulic cylinder’s piston will be retained in its last position. Display of control deviation /Adjusting the set value

The control deviation is displayed on each of the two desk tiles for the valves. The two instruments are connected in parallel. The set value for steam pressure in the header can be adjusted between 0 and 22 mbar at the controller by means of the set value push-button.

Electric manual control

The controller can be switched off by the push button “Controller on/off”. Then the valves can be controlled directly by hand by means of the push-button “Higher/Lower” below the valve position display with the aid of the remote-control manual control setter of the electrical equipment. The inscription “Higher/Lower” refers to the change in pressure when the push-button is operated, e.g. “Higher” means increasing the pressure (the leakoff steam control valve closes or the seal steam control valve opens). Manual control is disconnected during automatic control; the manual control setter is then automatically tracked to the controller output voltage by the equalizing controller so that when changing over from automatic control to manual control the manual control setter is already in the correct position. Under manual control the equalizing controller automatically tracks the output voltage of the disconnected controller 1.9 to the manual control voltage. If the control deviation has been reduced to zero by positioning the valves before the controller is switched on, the change-over from manual control to automatic control will be bump less; otherwise the controller regulates the pressure to the preset value after it has been switched on. Thus, it is quite easy to switch the controller on and off during operation.

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5.1-0670-01/4

Power Plant identification System

Steam Turbine

Control System

Description

Diagram Legend

Title

Coordinete

LBC10 AA001 KA01 LBC10 CG001 B C D E

Swing Check Valve of CRH Rotary Servomotor Limit Switch, Open Position Limit Switch, Closed Position Limit Switch, Open Position Limit Switch, Closed Position

E7 E7 E7 E7 E7 E7

LBS21 AA001 KA01 LBS21 CG001A

Extraction Check Valve A2 Servomotor Remote Position Indicator

E12,13 E12,13 E12,13



E13 E13 E13

LBS31 AA002 LBS31 CG002 A

Extraction Check Valve A3 Remote Position indicator

E13 E13

LBS41 AA001 KA01 LBS41 CG00 1A


C10 C10 C10



C10 C10 C10



AB11 A 11 B 11



AB1 1,12 A12 B12

LBQ50AA001 KA01 LBQ50CG001 A


E9 E9 E9

LBQ5OAA002 LBQ50 CG002A

Extraction Check Valve A5 Remote Position Indicator

E9 E9


MAA10 + 20 CG001 B,F,H C,G,J D E MAA10+ 20 AA002 KA01 KA02 KA05

Main Stop Valve Piston Piston Disc

ABC7 AB7 B7

Limit Switch, Open Valve Position B7 Limit Switch, Closed Valve Position B7 Limit Switch, Open Valve PositionATT B7 Limit Switch, Closed Valve PositionATTB7

Main Control Valve Servomotor Piston Pre Control Pilot Valve

BHEL Haridwar

BC7,8 C7,8 C7 C7

Coordinete

KA06 KA07 KA09 M AA002 MS61

Relay Piston for Pre Control Pilot ValveC7 Main Pilot Valve C7 Hand wheel for Testing Device B7 Electrical Motor for Testing Device B7 Torque limit Switch, Testing Device 100% ATT B7 MS62 Travel Limit Switch, Testing Device 100% ATT B7 MS72 Torque Limit Switch, Testing Device 0% A TT B7 MS73 Travel Limit Switch, B7 Testing Device 0% ATT

MAA10 + 20 CG002 A C MAB10 +20 AA001 KA01 KA02 MAB10 + 20 CG001 B,F,H, C,G,J D E

MAB10+ 20 AA002 KA01 KA02 KA05 KA06 KA07 KA09 M MS61 MS62 MS72

MAA10 + 20 AA001 KA01 KA02

Title

MS73

MAB10 + 20 CG002 A C MAD12 CY011,012,013 MAG01 AA011 MAG01CG01 B C E MAG01AA016

Remote Position Indicator C7 Limit Switch, Closed Valve Position ATT C7

Reheat Stop Valve Piston Piston Disc

ABC9 A9 A9

Limit Switch, Open Valve Position A9 Limit Switch, Closed Valve Position A9 Limit Switch, Open Valve Position ATT A9 Unlit Switch,Closed Valve Position ATT A9

Main Control Valve

BC9,10

Servomotor C10 Piston C10 Pre Control Pilot Valve C10 Relay Piston for Precontrol Pilot ValveC10 Main Pilot Valve C10 Hand wheel for Testing Device B10 Electrical Motor for Testing Device B10 Torque Limit Switch, Testing Device 100% ATT B10 Travel Limit Switch, Testing Device 100% ATT B10 Torque Limit Switch, Testing Device 0% ATT B10 Travel Limit Switch, B10 Testing Device 0% ATT

Remote Position Indicator C10 Limit Switch, Closed Valve Position C10 ATT Electrical Thrust Bearing Trip

D8

Low Vacuum Trip. Limit Switch, Not Reset Limit Switch, Alarm Limit Switch, Alarm ATT Condenser Safety Device (Bypass Control)

B5 B5 B5 B5 G9

5.1-0681-05/1


Title

Coordinete

Power Plant identification System MAX32BT021

MAV21 AP001

Main Oil Pump

MAV21BT001

Oil Filter (Hydraulic Control Equipment Rack)

MAX31 BB011, 016

E1 MAX32BT081 D4

Accumulator for HP Servomotor, Main Control Valves

B7

MAX31 BB21, 26

Accumulator for HP Servomotor, Reheat Control Valves

B9

MAX31 BB021 BB041,049

Accumulator for HP Servomotor, Bypass Control Valves

C11

MAX32 BT011 +012

Fluid Filter for Pre Control. Main Control Valves

A7

Coordinete

Fluid Filter for Pre Control, Reheat Control Valves

A10

Fluid Filter for Pre Control, Bypass Control Valves

C11

MAX41 CP50l

Pressure Gauge. Control Fluid (Hydraulic Control Equipment Rack) C2

MAX42AA001

Slide Valve for Swing Check Valve Cold Reheat

D7

Slide Valve for Swing Check Valve Cold Reheat

D8

MAX42AA011

Non-Return Valve

B1

MAX42BT001

Fluid Filter (Hydraulic Control Equipment Rack)

C1


C2


B4

Fluid Filter (Hydraulic Bypass Control Equipment Rack)

G6

MAX42AA002

MAX42BT002

MAX42BT003

MAX42BT021

MAX42BT022

Fluid Filter for Water Injection Valves (Hydraulic Bypass Control Equipment Rack) A12

MAX42CP501

Pressure Gauge, Control Fluid (Hydraulic Bypass Control Equipment Rack)

F6

MAX42CP511

Pressure Gauge, Control Fluid Water Injection Valve Open B12

MAX42CP512

Pressure Gauge. Control Fluid Water Injection Valve for Sequential Water Injection Open B13

MAX44AP001

Hydraulic Speed Transmitter

E1

MAX44CP501

Pressure Gauge, Primary Oil

A5

MAX45BB001

Accumulator for Extraction Valve Relay

E4

MAX45BY001 KA01 KA02 KA04 KA05 KA06 KA08 KA10 KA11

5.1-0681-05/2

Title

Electro-Hydraulic Electro-Hydraulic Converter Follow-Up Piston for Main Control Valves Follow Up Piston for Reheat Control Valv8S Sleeve Piston Helical Spring Piston Adjusting Device Control Valves Manual Adjusting Device

F4 F5 F5 F4 F4 F4 F4 F5 F5

Power Plant identification System MAX45 CG001

A K T B C

Title

Coordinete

Remote Position Indicator F4 Remote Position Indicator F4 Solenoid F4 Limit Switch Operating Without Bypass Valves and Adjusting Device Device Blocked F5 Limit Switch, Displacement of Control Valves F5

MAX45BY011 MAX45BY011 KA01 KA02

Hydraulic Converter F2 Follow-up Piston for Main Control Valves F3 Follow-Up Piston for Reheat Control F3 valve KA04 Sleeve G3 KA05 Piston G3 KA06 Helical Spring F3 KA07 Pilot Valve G2 KA08 Piston G3 KA09 Proportional Band Adjustment G2 KA10 Adjusting Device Control Valves F4 KA11 Manual Adjusting Device F4 MAX45CG011 B Limit Switch, Operation without Bypass Valves and Adjusting Device Device Blocked F3 C Limit Switch, Displacement of control valves F4 MAX45CP501

Power Plant identification System MAX47CG001F MAX47CG001F MAX47CP501 MAX47CP501 MAX48 CP501

G1 G1

MAX51 AA005 +006

Main Trip Valve

B2

MAX 51 CG005+006 C E

Limit Switch, Alarm Limit Switch, Alarm, ATT

B2 B2

MAX51 AA011 KA01 KA02

Extraction Valve Relay Valve Valve

D5 D5 D5

MAX51AA041 MAX51AA041

Slide Valve for Extraction Check Valve A2

MAX51 AA044


A 11


C12


A11


E9


Changeover Valve

B3

MAX51 CG211B C

Limit Switch, up Normal Position ATT B3 Limit Switch, Down- Test Position ATT B3

MAX51CP501 MAX51CP501

Pressure Gauge, Trip Fluid

MAX51 CP522 527

Pressure Gauge, Trip Fluid above piston Main Stop Valve A6

F2

MAX 51 CP523 528

Pressure Gauge, Trip Fluid below piston Disc Main Stop Valve B6

F2

MAX51 CP542 547

Pressure Gauge, Trip Fluid above Piston Reheat Stop Valve A9

MAX51 CP543 548

Pressure Gauge, Trip Fluid below Piston Disc Reheat Stop valve B9

MAX52AA005 MAX52AA005 MAX52 CG005 C E

Local/Manual Trip Valve Limit Switch, Alarm Limit Switch, Alarm ATT

B2 B2 B2

MAX 52 CP501

Pressure Gauge, Aux, Trip Fluid

D3

MAX51 AA048

Pressure Gauge, Secondary Fluid Reheat Control Valves

E2

MAX 51 AA051

MAX46BY001 MAX46BY001 KA01 KA02 KA03 KA04 KA05 KA06 KA07 KA08 KA09 M

Hydraulic Speed Governor Hand wheel Speed Setting Spring Link Sleeve Piston Helical Spring Overspeed Tester Lever Auxiliary Follow-up Piston Governor Bellows Electrical Motor

G1 F2 F1 F1 F2 F2 F2 F2 F2 G1 F1

MAX46CG001 A B

Remote Position Indicator Limit Switch 100% (Start-Up Automatic)

F2

MAX47 AA011 +012 MAX47 AA021 +022

Test Valve for Main Main Stop Valves

E12

C12

MAX51 AA047

MAX 51 AA 050

Pressure Gauge. Auxiliary Secondary Fluid Fluid

E3

Slide Valve for Extraction Check Valve A3 Slide Valve for Extraction Check Valve A4

F2

MAX46CP501

Coordinete

Limit Switch, 56% Pressure Gauge, Start-up Fluid Pressure Gauge, Auxiliary start-up fluid fluid

Pressure Gauge Secondary Fluid Main Control valves

MAX45CP511

Title

B6

Test Valve for Reheat Reheat Stop Valves Valves

A9

MAX47BY001 MAX47BY001 KA01 KA02 M

Starting and Load Limit Device Hand wheel Valve Electrical Motor

F1 F1 F1 F1

MAX47CG001 A B C D

Remote Position Indicator Limit Switch, 100% Limit Switch, 0% Limit Switch, 42%

F1 G1 G1 G1

MAX 51 AA056

E13

A3

5.1-0681-05/3

Power Plant Identification System MYA01 CS011-013 MAG01 AA201 MAX42AA001 MAX42AA001


Title

Coordinate

Electrical Speed Transmitter Solenoid Valve for Testing Low Vacuum Trip Solenoid Valve, Adjustment of Control Valves

Power Plant Iden- Title tification System

E1 B4 F5

Solenoid Valve for Load Shedding Relay in Secondary Fluid to Reheat Control Valves E5 MAX46AA011 MAX46AA011

MAX47 AA211 +212 MAX 47 AA221 +222

MAX48 AA201 +202




MAX51 AA028

MAX51 AA030

MAX51AA031 MAX51AA031 MAX61 AA011 +012

Test Valve for Main Main Stop Valves

Solenoid Valve for Load Shedding Relay in Auxiliary Secondary Fluid G2

Solenoid Valve for start -up Fluid, Main Stop Valve

B5

Solenoid Valve for Start-up Start-up Fluid, Reheat Stop Valves

B8

Solenoid Valve for Auxiliary Start-Up Fluid

B1,2

Solenoid Valve for Extraction Check Valve

E12

Solenoid Valve for Extraction Check Valve

E13

Solenoid Valve for Extraction Check Valve A4.1

C 12


A10


C12

Solenoid Valve For Extraction Check Valve A4.2

A11

Solenoid Valve for Extraction Check Valve A5

E9

Solenoid Valve for Control Fluid Supply during Test

B3

Solenoid Valve for Control Fluid Supply During Test

B4

B6 MAX51 AA036

MAX61 AA021 +022

Coordinate

Test Valve for Reheat Reheat Stop Valves Valves

B8

MAX62AA001 MAX62AA001 KA01 KA02 KA03 KA001M

Overspeed Trip Test Device Valve for Test oil Valve for Auxiliary Start-up Fluid Valve For Auxiliary Trip Fluid Electrical Motor

C4 C4 C4 C4 C4


Remote Trip Solenoid

C2

MAX62CG001 B C

Limit Switch, up-Normal position ATT C4 Limit Switch, Down- Test Position ATT C4


Remote Trip Solenoid

C2

MAX62CP501 MAX62CP501

Pressure Gauge, Test Oil Overspeed D1


Solenoid Valve for Sequential Trip Water Injection

MAX51 AA201

MAY10 AA001 +002 KA01

MAY10 CG001 +002 C E

Overspeed Trip Releasing Device

E2 E2

Limit Switch, Alarm Limit Switch Alarm ATT

E3 E3

5.1-0681-05/4



C13

Solenoid Valve for Changeover Changeover from Trip Fluid to Control Fluid C3

Power Plant identification System MAX61 AA211 +212

MAX61 AA221 +222

LBS42 CP002

MAG01CP201

MAG01CP202

MAG01CP203

MAG01CP204

MAG10CP011

MAG 10CP012

MAG10CP013

MAG10CP016

MAX45 CP211

MAX48 CP201

Title

Coordinete

Power Plant identification System MAX48 CP202

Solenoid Valve for Testing of Main Stop Valves

Solenoid Valve for Testing of Reheat Stop Valves

Differential Pressure Monitor for Extraction Check Valve-A4 (Batron -Cell)

Pressure Switch, low-Vacuum Trip, Vacuum min. Pressure Switch, low-Vacuum Trip, Vacuum max. Pressure Switch, low-Vacuum Trip, Vacuum min. Pressure Switch, low-Vacuum Trip Vacuum max. Pressure Switch, Electrical Low Vacuum Trip. Signal Pressure to high Pressure Switch, Electrical low Vacuum Trip, Alarm

C5,6 MAX51 CP001 +002 C8

B11

Pressure Switch For Reheat Control Valves Secondary Fluid Pressure Switch For Auxiliary Start-up Fluid

MAX51 CP207 +208

MAX51 CP209 +210 B4

B4

B5

B5

E13

E13

Pressure Switch Electrical low Vacuum Trip Interlocking MAG10CPO12 E14 Pressure Switch for Energizing of Vacuum Breaker

MAX51 CP205 +206

E13

E2

Title

Coordinete

Pressure Switch for Auxiliary Start-up Fluid Between Solenoid Valves MAX48AA201 and202

B1

Pressure transmitter for Trip fluid

A1

Pressure Switch for Trip Fluid Between Solenoid Valves MAX51 AA201 and 202 B3

Pressure Switch for Trip Fluid Ahead of Changeover Valve MAX51 A211 B3

Pressure Switch for Trip Fluid Ahead of Changeover Valve MAX51 AA211 B2,3

MAX51CP 221 +226

Pressure Switch for Trip Fluid ahead of Main Stop Valve, Test Valve B6

MAX51CP222 +227

Pressure Switch for Pressure above Piston of Main Stop Vale

B7

MAX51 CP223 +228

Pressure Switch for Pressure below Piston Disc of Main Stop Vale

A7

MAX51CP242 +247

Pressure Switch for Trip Fluid above Piston of Reheat Stop Valve

A9

MAX51 CP243 +248

Pressure Switch for Trip Fluid Below Piston Disc of Reheat Stop Valve

B9

MAX52CP211

Pressure Switch for Auxiliary Trip Fluid

B3

Pressure Switch for Test oil of overspeed Trip max

D1

Pressure Switch for Test oil of overspeed Trip max.

D1

Pressure Switch for Test oil of overspeed Trip Pressure Collapsed

D2

MAX62 CP 211

MAX62 CP 212

MAX62 CP 213

C2 MAX45 AA031

Pressure Converter for IP secondary Oil

E4

5.1-0681-05/5

Steam Turbine Description No.

1 2

3 4 5 6

7

8

9

10 11 12

13

14

15

16

17

Lubrication Point Overspeed test device Reduction gear of overspeed trip test device Bearing of low vacuum trip Main control valve stem Main stop valve stem Limit Switch attachment on main stop valve Limit Switch attachment on main control valve Hinge of main control valve position indicator LAWA actuator VR 16 VR 16 of main control valve Reheat control valve stem Reheat stop valve stem Limit switch attachment on reheat stop valve LAWA actuator VR 16 VR 16 of reheat control valve Hinge of reheat control valve position indicator Limit switch attachment on reheat control valve Hinge of extraction swing check valve Adjusting gear of starting and load limit device

BHEL Haridwar

Filling Quantity

Lubrication Chart

Lubricant

Turbine oil* 200g

Grease Servogem-2 Turbine oil*

10g

≈

Molykote M30 Molykote M30

Every 1 to 2 months

Use no oil or grease

Molykote M30

Every 1 to 2 months


Calypsol SF7-026

Every 104 Operating hours After every dismantling After every dismantling Every 1 to 2 months

0.4 kg

0.4 kg

Molykote M30

Every 104 Operating hours Every 1 to 2 months

Molykote M30

Every 1 to 2 months

Molykote U Molykote U Molykote M30 Calypsol SF7-026

Molykote U

200g

Remarks

Use no oil or grease Use no oil or grease Use no oil or grease

Molykote U

0.4 kg

Every 1 to 2 months Every 1 to 2 months

Top-up Quantity

Every 1 to 2 months After every dismantling After every dismantling Every 1 to 2 months

Molykote U

0.4 kg

Lubrication Interval

Grease Servogem-2

Use no oil or grease Use no oil or grease Use no oil or grease

Use no oil or grease Use no oil or grease

After every dismantling Every 1 to 2 months

Use no oil or grease 10g

≈

5.1-0690-05/1

No.

18

19

20 21

22

23

* **

Lubrication Point Journal for hydraulic speed governor Adjusting gear of reference speed setter Bearing of trimming device Hinge of cold reheat swing check valve Stem guides of shaft seal steam valve

Shaft seal steam valve actuators

Filling Quantity

Lubricant

Turbine oil*

200g

Grease Servogem-2 Turbine oil* Molykote U

7 to 9 kg

Lubrication Interval

Top-up Quantity

Every 1 to 2 months Every 1 to 2 months

10g

≈

Every 1 to 2 months After every dismantling

Molykote U

After every dismantling

Hydraulic oil to DIN 51517 and VDMA 24318 H-LP oils**

1stoil change after 6 months, thereafter every12 months.


7 to 9 kg

Turbine oil 46/Servoprime 46 of IOC, Turbinol 47 of HPCL or equivalent HLP 46 (VG) ISO of IOC

5.1-0690-05/2

Remarks

Use no oil or grease. Lubrication point not shown Lubrication point not shown


Technical Data Construction, Speed & Steam Pressure

Load Rated Load

500 MW

Maximum Load under valve wide open (VWO) condition

524.9 MW

Construction Three cylinder reheat condensing turbine Single flow HP Turbine with 17 reaction stages

Type : H30-100-2

Double flow IP Turbine with 12 reaction stages per flow

Type : M30-63

Double flow LP Turbine with 6 reaction stages per flow

Type : N30-2x10-2

2 Main Stop and Control valves (HP casing mounted)

Type : EV 320-1

2 Reheat Stop and Control Valves (Floating)

Type : IV 560

1 Swing Check Valve in cold reheat line

DN-800 Make : BHEL, Trichy

2 LP Bypass Stop and Control Valves (EHA Based)

Make : CCI, Switzerland

Extraction Swing Check Valves Extraction 1

: No valve

Extraction 2

: 1 Swing Check Valve with actuator and 1 Swing Check Valve without actuator

DN 800 Make : BHEL, Trichy

Extraction 3



Extraction 4.1 : 2 Swing Check Valves with actuator


Extraction 4.2 : 2 Swing Check Valves with actuator


Extraction 5



Extraction 6

: No valve

BHEL Haridwar

5.1-0100-63/1

5.1-0690-05/3


Hydraulic Speed Governor with Starting and Load Limiting Device

Function The function of the hydraulic speed governor is to operate the control valves to give the appropriate turbine steam throughput for the particular load condition. The arrangement and functioning of the governor within the overall governing system is described in the section on governing. Construction The principal components of the speed governor are the bellows (8), the link (11), the speed setting spring (13), the sleeve (5) and the follow-up piston (4). The primary oil supply from the hydraulic speed transmitter is available at connection ‘a1‘. A fire resistant fluid is used as the hydraulic fluid in the governing system. An additional bellows (9) prevents primary oil getting into the control fluid circuit if there be a leakage in the governor bellows (8). In this case, the leakage oil can be drained off via connection ‘c1 ‘. In case a leak in the bellows (9) occur, the control fluid that has leaked in will also be drained off via connection ‘c1’. The primary oil pressure (connection ‘a1‘) is dependent on the speed and determines the position of the link (11) via the bellows (8) and the push rod (10). The speed setting spring (13) opposes the primary oil pressure. Its pre-compression can be varied either by hand or remotely by the motor (16). The sleeve (5) which can slide on the bottom end of the follow-up piston (4) is attached to the link (11). The follow-up piston is held against the auxiliary secondary fluid pressure (connection ‘b’) by the tension spring (3). The follow-up piston and the sleeve have ports, which at normal overlap allow sufficient fluid to escape to produce equilibrium between the auxiliary secondary fluid pressure and the force of the tension spring (3). Each steady-state position of the link (11) and hence of the sleeve (5) corresponds to a specific force from the tension spring (3) and hence to a specific secondary fluid pressure which in turn determines the position of the control valves.

BHEL Haridwar

Mode of Operation If the primary oil pressure falls (as a result of increasing load and the resulting drop in speed), the link (11) and the sleeve (5) sliding on the follow-up piston (4) are moved downwards by the speed setting spring (13) so that the overlap of the ports in the sleeve and the follow-up piston is reduced. This causes the pressure in the auxiliary secondary fluid circuit to rise and the followup piston follows the movement of the sleeve against the increasing force of the tension spring (3) until normal overlap of the ports and equilibrium are restored. The lift of the control valves is increased in this manner by the increased secondary fluid pressure. Conversely, a rise in primary oil pressure causes the lift of the control valves to be reduced. When the pre-compression of the speed setting spring (13) is varied with the reference speed setter it changes the relationship between the primary oil pressure and the secondary fluid pressure and hence the relationship between speed and power output. Lever (12) allows the link (11) to be depressed by hand to give a lift signal to the governor, e.g. to provide a second means of overspeeding the machine for testing the overspeed trips in addition to the overspeed trip tester. Starting and load limiting device Before start-up, the pilot valve (21) is brought to its bottom limit position either by hand or remotely by the motor (20). This causes the bellows to be compressed via the lever (6) and the pin (7) until the governor assumes the position “Control ”. With the pilot valve (21) in valves closed ”. the bottom limit position, control fluid from connection ‘a’ can flow simultaneously to the auxiliary start-up fluid circuit (connection ‘u1‘) and as start-up fluid via connection ‘u’

5.1-0710-00/1

to the stop valve to prepare these for opening. When the pilot valve (21) is moved back the auxiliary start-up fluid circuit is depressurized and subsequently the start-up fluid connection ‘u’ is opened to the return ‘c’. This opens the stop valves. Further upward movement of the pilot valve (21)

5.1-0710-00/2

causes the pin (7) to release the bellows as with falling primary oil pressure and the control valves are opened. The release of the bellows can be limited by the pin (7) so that the control valves do not open any further despite a further reduction in primary oil pressure.

Steam Turbine Description Function The adjusting gear is used for manual or motor operation of the reference speed setter and the starting and load limiting device. Mode of Operation The speed/load adjusting gear is operated either manually or by means of motor (28). The rotary movement of the motor shaft is transmitted to worm wheel (15) via worm wheel (9) and the worm attached to it. Wormwheel (15) is located axially on the threaded portion of the hand wheel spindle (16) by insert (5) and the gear casing (11). The spindle (16) is connected with bushing (4) by a feather key so as to permit the

BHEL Haridwar

Adjusting Gear

spindle to slide axially in the bushing (4), which can rotate in cover (19). Spring (6) forces the thrust rings (18) against bushing (4) which prevents bushing (4) and spindle (16) from turning. Spindle (16) however, can be moved axially by turning the worm wheel (15). Spindle (16) can be moved up or down depending on which direction wormwheel (15) turns. The limit of travel is set by limit rings (14 and 17). If either stop has been reached the thrust rings operates as a slip coupling. The thrust rings also protect the motor (28) from overload in the event of restrictive movement within the adjusting gear.

5.1-0720-00


Electro-hydraulic Converter for Turbine Control System

Function The electro-hydraulic converter is the connecting element between the electrical and hydraulic parts of the turbine control system. It converts the signals from the electric controller into the hydraulic signals and amplifies them before transmitting them to the actuating devices. Construction The principal components of the converter are moving coil system (12), sleeve (10), pilot valve (6), amplifier piston (3), follow-up pistons (21), differential transformer (1) and actuator (17). Bushings and follow-up pistons ‘A’ are connected to each other via the adjusting screws (24), spring end pieces and the springs (22). The control signals from the electro-hydraulic controller operate the sleeve (10) via the moving coil system (12). This sleeve slides up and down on the top end of the pilot valve (6) and determines the position of the valve in the manner of a follow-up piston. The pilot valve and sleeve have ports which depending on the overlap, control the amount of trip fluid flowing from connection ‘x’. In the steady-state condition, the pilot valve is in its center position and the trip fluid pressure acting on the face of the pilot valve is in equilibrium with the force of compression spring (9). The pilot valve is kept in rotation by control fluid flowing from tangential holes in an integral collar to give greater freedom of reciprocal motion and achieve high response sensitivity. When the pilot valve is deflected from its center position, control fluid from connection ‘a’ is admitted to the space above or below the amplifier piston (3) with the opposite side of the piston opened to the fluid drain. The resulting motion of the amplifier piston is transmitted via lever (13) to the sleeves (20) which in turn can slide on the following-up pistons (21). The secondary fluid circuits, which are fed from the trip fluid circuit via throttles and supply the various actuating devices, are connected at point ‘b’. The secondary fluid pressures are determined by the tension of springs (22) which

BHEL Haridwar

counter balance the fluid pressure acting on the follow-up pistons (21). Each follow-up piston and sleeve (20) has ports, which control the secondary fluid flow according to their overlap. When the throttling area is changed by the movement of the sleeve (20), it also changes the pressure in the follow-up piston causing it to follow the movement of the sleeve. This varies the tension of springs (22) until equilibrium is regained between the spring force and the new secondary fluid pressure. Each position of the amplifier piston (3) thus corresponds to a specific position of the sleeves (20) and,

5.1-0730-02/1

Controlling action hydraulic Converter

with

the

Elctro-

When the electric controller gives a command to open the control valves, the sleeve (10) is moved upwards by the moving coil system (12), thus decreasing the fluid drain area. This causes the pressure below the pilot valve (6) to increase and the pilot valve moves upwards and opens the way for control fluid from connection ‘a’ to flow to the space below the amplifier piston (3). The following movement of the amplifier piston (3) then slides the sleeves (20) downwards over the levers (13,19) reducing the drain area between the sleeves and the follow-up pistons, causing the pressure in the follow-up pistons and secondary fluid circuits to rise.

therefore, the follow-up pistons (21). The position of the follow-up piston is the determining factor for the secondary fluid pressure at point ‘b’. The initial tension of the follow-up piston springs can be varied by means of the setscrews (24).

The motion of the amplifier piston (3) produces a simultaneous feedback action on the pilot valve (6) via the differential transformers (1). The sleeve (10) is moved back until the new position of the amplifier piston causes the pilot valve (6) to assume its center position and equilibrium is restored between the fluid pressure below the pilot valve and the compression spring force (9). When a command is given to close the control valves, the controlling action is similar but in the reverse sequence.

Adjusting Device for Valves The follow-up pistons ‘B’ and the lever (14)

5.1-0730-02/2

of the rotary shaft (15) situated above it are connected by the springs (22) of follow-up pistons ‘B’, the guide pin (16) and the setscrews (30). During normal operation an energized solenoid valve allows control fluid ‘a1’ to flow under the piston (25) of the actuator (17). The piston (25) is moved upwards against the forces of the spring (26). Stop (34) locked in normal position by pin and the initial tension of the tension springs (22) of the follow-up pistons ‘B’ is adjusted by means of the lever (28, 14) which results in the IP control valves opening in relation to the HP control valves as intended for this operation.

Setting Device Bypass Valves

for

start-up

without

If the plant is started up without bypass system, the IP/reheat stop and control valves must open before the main steam stop and control valves. For this purpose, the hand wheel (32) is set in the upper end position. Signal from limit switch (33): Setting device in operation without bypass system position.

If the condition turbine load less than a set minimum load and the ratio of HP exhaust steam pressure to main steam pressure greater than the set pressure ratio is fulfilled, for example after load shedding, the solenoid valve will be deenergized. This blocks the flow of control fluid to the actuator (17) and allows control fluid under the piston (25) to flow into the return pipe. The force of the spring (26) moves the piston into the lower end position and the tension springs (22) of the follow-up pistons ‘B’ are adjusted so that the IP control valves do not begin to open until the HP control valves are wider open. The lever (28) then rests on the precisely set stop (34). Limit switch (29) indicates: Setting device engaged.

5.1-0730-02/3


Function The function of the hydraulic amplifier is to amplify the signals from the hydraulic speed governor (connection ‘b1’) so that they are sufficient for the actuating devices.

Hydraulic Amplifier for Turbine Control System

auxiliary secondary circuit and the force of spring (8) are in equilibrium. The pilot valve is kept in rotation by control fluid flowing from tangential holes in an integral collar to give greater freedom of reciprocal motion and high response sensitivity.

Construction The principal components of the amplifier are amplifier piston (1), pilot valve (7), follow-up piston (2) with sleeves (3), mechanical feedback system (6) and actuator (21). Bushings and follow-up pistons ‘A’ are connected to each other via the setscrews (10), spring end pieces and springs (11). Auxiliary secondary fluid flows

When the pilot valve is deflected from its center position control fluid from connection ‘a’ is, admitted to the space above or below the amplifier piston (1) with the opposite side of the piston opened to the fluid drain. The resulting motion of the amplifier piston is transmitted via lever (5) to the sleeves (3) which in turn, slide on the follow-up piston (2). The secondary fluid circuits, which are

over the pilot valve (7) via connection ‘b1’. In the steady-state condition, the pilot valve is in its center position and the pressure in the

fed from the trip fluid circuit via throttles and supply the various actuating devices, are

BHEL Haridwar

5.1-0740-02/1

connected at point ‘b’. The secondary fluid pressures are determined by the tension of springs (11), which counterbalance the fluid pressures acting upon the follow-up pistons. Each follow-up piston (2) and sleeve (3) has ports, which control the secondary fluid flow according to their overlap. When the throttling area is changed by movement of the sleeve (3), it also changes the pressure in the follow-up piston causing it to follow the movement of the sleeve, This varies the tension of spring until equilibrium is regained between the spring force and the new secondary fluid pressure. Each position of the amplifier piston (1) corresponds to a specific position of the sleeve (3) and the follow-up piston (2). The position of the follow-up piston is the determining factor for the secondary fluid pressure at point ‘b’.

5.1-0740-02/2

The initial tension of the follow-up piston springs can be varied by means of the adjusting screws (10, 14), and the levers (15, 16).

Controlling action with the Hydraulic Governor The pressure above the pilot valve (7) is varied by the hydraulic governor via varying the auxiliary secondary fluid pressure connected at ‘b1’. An increasing auxiliary secondary fluid pressure causes the secondary fluid pressure at the connection ‘b’ to rise and open the actuating devices; a

reduction in the secondary fluid pressure causes the actuating device to close. The motion of the amplifier piston produces a simultaneous feedback via lever (6) and causes the pilot valve to assume its center position when the new position of the amplifier piston is reached. Each auxiliary secondary fluid pressure corresponds to a certain position of the piston (1) which, in turn, results in a certain secondary fluid pressure at connection ‘b’ with each auxiliary fluid pressure. The degree of proportionality of the hydraulic governor can be adjusted by varying the position of lever pivot (6) with the setscrew (9).

If the condition Turbine load less than a set minimum load and the ratio of HP exhaust steam pressure to main steam pressure greater than the set pressure ratio is fulfilled, for example after load shedding, the solenoid valve will be de deenergized. This blocks the flow of control fluid to the actuator (21) and allows control fluid under the piston (20) to flow into the return pipe. The force of the spring (19) moves the piston into the lower end position and the tension springs (11) of the follow-up pistons ‘B’ are adjusted so that the IP control valves do not begin to open until the HP control valves are wider open.

The follow-up piston ‘B’ and the lever (15) of the rotary shaft (12) situated above it are connected by the springs (11) of follow-up pistons ‘B’, the guide bolts (13) and the setscrews (14).

The lever (16) then rests on the precisely set stop (25). Limit switch (17) indicates: Setting device engaged.

During normal operation, an energized solenoid valve allows control fluid ‘a1’ to flow under the piston (20) of the actuator (21). The piston (20) is moved upwards against the force of the spring (19). Stop (25) locked in normal position by pin and the initial tension of the tension spring (11) of the follow-up piston ‘B’ is adjusted by means of the lever (15, 16) which result in the IP control valves opening in relation to the HP control valves as intended for this operation. o peration.

Setting Device for Start-up without bypass valves If the plant is started up without bypass system, the IP/reheat control valves must open before the main steam steam control valves. For this purpose, the hand wheel (24) is set in the upper end position. Signal from limit switch (23): Setting device in operation without bypass system position.

5.1-0740-02/3

Speed Rated speed

50.0 c/s

Speed limitation in load and station operation Max. Speed, no time limitation

51.5 c/s

Min. Speed, no time limitation

47.5 c/s

Permissible for maximum 2 hours during the life of LP blading Speed below Speed above

47.5 c/s 51.5 to 60 c/s

Speed exclusion range at operation without load *

7 to 47.5 c/s

Standard over speed trip setting

Max. 55.5 c/s

* This speed range should be passed through in one smooth operation to avoid endangering the blades due to resonance

Steam Pressures Rated Initial Steam

♦

Long time operation

♣

Short time operation

♥

Unit

166.7

166.7

200

bar

Before 1 HP drum stage

154.4

169.8

169.8

bar

HP cylinder exhaust

44.0

50.63

52.84

IP cylinder stop valve inlet

39.6

45.97

47.56

Extraction 6

44.0

50.63

52.84

bar

Extraction 5

16.8

20.08

20.08

bar

Extraction 4

6.94

8.36

8.36

bar

Extraction 3

2.744

3.36

3.36

bar

Extraction 2

1.469

1.81

1.81

bar

Extraction 1

0.342

0.42

0.42

bar

LP cylinder exhaust

0.1013

0.3

0.3

bar

st

♠

bar

♠

bar

♦

These values correspond to 500 MW load with 3 % make-up and 0.1013 bar back pressure with all heaters in service and rated steam conditions.

♠

The safety valves must be set so that short time values are not exceeded.

♣

Long time operation: Upper limit value, permissible without time limit.

Short time operation: Permissible momentary value. The aggregate duration of such swings must not exceed 12 hours in any one year All pressures are absolute pressures

♥

5.1-0100-63/2


Construction and Mode of Operation The electrical speed pick-up located in the front bearing pedestal indicates the exact speed through all speed ranges of the turbine. The measuring procedure functions as follows: A toothed wheel (1) is mounted on shaft (2) of main oil pump. The speed probes are installed around the periphery of the

BHEL Haridwar

Electrical Speed Pick-Up

toothed wheel, which rotates, with the rotation of the turbine shaft. On rotation of the toothed wheel (1), electrical impulses are generated as a result of alternating effect between the speed probe (3) and the toothed wheel (1). The output frequency is conducted to the speedmeasuring unit.

5.1-0760-01


Pressure Converter

Function The pressure converter is installed in the IP secondary oil circuit. It does not permit to raise the IP secondary oil pressure beyond certain value. Construction The pressure converter is provided with a follow up piston (3), which slides in the bushing (6) at the top, and in the sleeve (2) at the bottom. The bushing and follow up piston are connected to each other via the set screw (9, 10) and the spring (4). There are drainage slots in the follow up piston (3) and sleeve (2), through which a larger or smaller amount of fluid can flow into the fluid return line ‘c’ depending on how much they overlap. The fluid pressure prevailing in the follow up piston (3) is connected to the reheat control valves for speed control via connection ‘x’. Mode of Operation When the setscrew (9) of the pressure converter has been appropriately set, IP secondary fluid pressure is permitted to increase to certain value.

1 Ring 2 Sleeve 3 Follow up piston 4 Spring 5 Casing 6 Bushing 7Cover

BHEL Haridwar

8 Cap 9 Set Screw 10 Set Screw

c Return flow x IP secondary fluid

5.1-0761-00


Combined Main Stop and Control Valves

Function and Arrangement

Stop Valve

One stop and one control valve are combined in a common body. The main stop valve provides a means of isolating the turbine from the main steam line and can rapidly interrupt the supply of steam to the turbine. The function of the control valve is to regulate the flow of steam to the turbine according to the prevailing load.

The steam enters the valve casing (13) via the Inlet connection and remains above the stop disc (1). The main valve disc incorporates a pilot disc formed from the end of the valve steam (3). The valve stem is sealed by packing rings (6). On the back of the valve disc is a raised seat which comes into contact with a neck bush (4) when the

BHEL Haridwar

5.1-0810-01/1

valve is fully open and so provides extra sealing at this point for the stem. Both stem and disc are secured against torsion. The valve body cover (2) is held in the valve casing (13) by a threaded ring (8). There is a U-shaped gasket (5) between cover and casing. The two legs of the gasket are pressed against the sealing face to give a tight joint .The stop valve is opened hydraulically and closed by spring force.

Testing Main Stop Valve Each stop valve must be tested at regular intervals to ensure proper functioning. A testing valve is provided for this purpose.

5.1-0810-01/2

Control Valves The stem and disc (16) of the control valve are in one piece. Balancing holes in the valve disc reduce the operating force required. The valve stem and disc (16) are guided in the cover (17) and the stem is sealed by packing rings (20). When the valve is fully opened, the raised seat of the valve disc rests against the neck bushing (18) and provides additional sealing. As with the stop valve, the valve body cover (17) is held in the casing by a threaded ring (21) and is sealed by U-shaped gasket (19). The control valve is actuated by the piston of the servomotor (26) that is operated by a cup spring in the closing direction and hydraulically in the opening direction.


The operative part of the servomotor consists of a two-part piston, the lower discshaped part of which is connected via piston rod to the valve stem. The other part of the piston is bell-shaped and moves within the housing, which is in the form of a cylinder. Two spiral springs are placed between the two halves of the piston at the lower end a spring plate is interposed between the springs and the piston disc. When trip fluid is admitted to the space above the bellshaped part of the piston, it moves this half of the piston downwards, compressing the springs, until it seats against the piston p iston disc.

Servomotor for Main and Reheat Stop Valves

the piston and the piston disc connected to the valve stem moves to close the valve. Just before the valve disc seats, the piston disc enters a part of the cylinder where the diametral clearance is reduced. This arrangement restricts the flow of fluid past the piston disc and so produces a braking action, which causes the valve disc to seat gently. All fluid connections are routed through a test valve. All operations can be controlled by means of the test valve and the starting & load limiting device and main trip valve.

After the main stop valves have been opened, the turbine is started by the control valves. Before the main stop valves can be opened, however, they must be “pressurized”, i.e. prepared for opening, by admitting trip fluid from the trip fluid circuit to the space above the piston to press it down against the piston disc after overcoming the resistance of the springs. The edge of the bell-shaped half of the piston is designed to produce an fluid tight seal with the piston disc. To open the valve, fluid from the trip fluid circuit is admitted to the space below the piston disc and, simultaneously, the space above the bell-shaped half of the piston is opened to drain. This causes both halves of the piston to move together in the direction, which opens the valve. In order to reduce fluid leakage past the bell-shaped part of the piston when the valve is open, a back seat is provided in the housing against which the collar of the piston can seat. When the valve is tripped, the pressure in the trip fluid circuit, and hence in the space below the piston disc, falls, with the result that the springs separate the two halves of

BHEL Haridwar

5.1-0811-00


Hydraulic Servomotor for Main and Reheat Control Valves

The flow of steam to the turbine is regulated by varying the lift of the control vale by means of its servomotor.

order to ensure that the valve moves freely at all times.

The control valve is actually moved by the piston (9), which is loaded, on one side by the disc springs (10) and on the other side by hydraulic pressure. The position of the valve is determined by the secondary fluid pressure, which is controlled by the governor. Since large operating forces are required, the servomotor is of the highpressure type (approx. 32 bar) and has a pilot control system. The supply of secondary fluid (connection ‘b’) controls the auxiliary pilot valve (14) which directs control fluid from connection ‘a1’ to the appropriate side of the pilot piston (4). The pilot piston operates the main pilot valve (3) through lever (5) so that when the valve is being opened, control fluid from connection ‘a’ is directed to the underside of piston (9). When W hen the valve is being closed, fluid drains through the main pilot valve.

The movement of the pilot piston (4) deflects the main pilot valve (3) from its center position by means of lever (5) so that either, control fluid from connection ‘a’ is directed to the underside of piston (9) and the control valve opens, or the underside of piston is opened to drain so that the disc springs can close the control vale. Shortly before the main valve disc actually comes into contact with the seat, the servomotor piston (9) enters a recess turned in the body and throttles the flow of fluid draining from the underside of the piston. This slows down the valve closing motion and the disc seats gently. The spring (1) pre-loads the linkage and prevents any slackness or lost motion m otion at the pivots. The straight feedback cam (7) mounted on the end of the servomotor piston rod (8) returns the main pilot vale (3) to its center position by means of a lever system. The slope of the feedback cam is in two stages to give two degrees of proportionality, which produce good linearity of the steam flow characteristics.

Pilot Control System When the turbine is running and the valve is steady at any particular value of lift, the auxiliary pilot valve (14) will be in the center position shown in the drawing. In this position the force exerted by the spring (13) and the secondary fluid pressure acting on the auxiliary pilot valve are in equilibrium. When the governor varies the secondary fluid pressure to open or close the control valve, the auxiliary pilot valve is deflected from this center position. This allows control fluid (connection’ a1 ‘) to flow to one side of the pilot piston (4) while the other side of the piston is opened to drain. The movement of the pilot piston returns the auxiliary pilot valve to its center position by means of the feedback linkage (12) thus giving proportionality between secondary fluid pressure and pilot piston travel. The degree of proportionality of the pilot control system can be adjusted by varying the position of the feedback lever pivot (12). The auxiliary pilot valve is continuously rotated by the action of fluid issuing from tangential drillings in a disc mounted on its spindle in

BHEL Haridwar

Main Control System

Testing Device The control valve can be operated either by hand or under power independently of the governor by means of the testing device (11) in order to check the free movement of the valve. The testing device acts on the lever (5) in the same manner as the pilot piston (4); the system demanding the smaller valve lift being in control, Damping Device Fig.2 illustrates the auxiliary pilot valve (14) and the damping device in the secondary fluid circuit. Any signals in the secondary fluid circuit are damped out by passing the secondary fluid through capillary tube (16) before it enters the auxiliary pilot vale (14). Any air carried by the secondary fluid is conducted to the free space in the actuator via the screw plug (18) and holes in the casing of the damping device and pilot valve.

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Function

Test Valve for Emergency Stop Valve

The function of the test valve is to open and close the emergency stop valve, either by start-up fluid circuit or manual operation especially when the emergency stop valve is being checked for easy movement.

lowering the pressure in the start-up fluid circuit or by manually turning the hand wheel (3). The trip fluid can now flow from connection ‘x’ to connection ‘x2’ via the auxiliary valve (5) and ducts in the casing, and thus under the piston disc.

Arrangement

Testing the Emergency Stop Valves

Each test vale (6) and auxiliary valve (5) is arranged in series behind a solenoid valve (1, 2).

For testing the emergency stop valve, the valve (6) is moved slowly downwards by means of the hand wheel (3). In this way, trip fluid is admitted to connection x1, and then connection x2 Iinked to drain c, which closes the emergency stop valve. After this, the hand wheel (3) is slowly turned back and the emergency stop valve opens again. This procedure is accordingly the reverse of the closing procedure.

Each emergency stop valve is served by one test valve, whereby a test valve (6) is combined with an auxiliary valve (5) in a common casing. These blocks of test valves are arranged in frames immediately next to the relative emergency valve groups. Opening of the Emergency Stop Valve In order to open the emergency stop valve, the valve (6) must first be forced downwards against the force of the spring (7). This can either be done by start-up fluid (connection ‘u’) or manually with the hand wheel (3). Trip fluid (connection ‘x’) can then flow to connection ‘x1’ and on over the piston in the emergency stop valve. The valve must then be returned to the upper position, either b y

BHEL Haridwar

Closing the Emergency Stop Valve by Automatic Testing Device When trip fluid is admitted under the auxiliary valve (5) via connection v, this will be forced upwards against the force of the spring (4). This links connection x2 with drain ‘c’ via valve (5). Fluid thus drains under the piston disc in the emergency stop valve and the valve closes suddenly.

5.1-0813-00

Steam Turbine Description Function and Construction One stop and one control valve are combined in a common body with their stems arranged at right angles to each other. The stop valve can interrupt the supply of steam from the reheater to the IP and LP turbines extremely quickly. The control valve controls the steam flow to the IP and LP turbines on load rejection, start-up & shutdown and remains fully open in the upper load range to eliminate any throttling losses. Further details of the arrangement of the valve combination in the control system can be seen under section “Governing system”. Reheat Stop Valve The stop valve is a single seat valve with integral pilot valve. Steam enters via the

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Combined Reheat Stop and Control Valves inlet of the valve body (2) and remains above the valve disc (7) when the stop valve is closed. A pilot valve, integral with the valve stem (6) is provided for relieving, thereby reducing the force necessary for opening. The valve disc (7) slides in the bushing of the valve cover (4) and has a bead on the back which lies against the base bushing (5) and provides additional sealing at this point. Metal packing rings (3) seal the valve stem. The stop valve is opened hydraulically and closed by spring force. Testing Stop Valves Each stop valve must be checked for correct operation at regular intervals. A test valve is provided for this purpose. The checking procedure is described in section “Test valve”.

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Control Valve

The control valve has a pipe-shaped valve disc (14) that is bolted to the valve stem (13) and slides in the bushing in the valve cover (11) The valve disc is provided with relieving holes to reduce the necessary controlling force. A ring fixed in the bushing of the valve cover prevents the valve disc from rotating. This valve disc also has a back sealing that operates

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when the valve is fully open. Asbestos/graphite packing rings (10) seal the valve stem (13) in the valve cover (11). The control valve is operated by the piston of the servomotor (9) i.e. is opened hydraulically and closed by disc springs. In the event of a disturbance in the system or on trip-out, both stop valve and control valve close rapidly.

Low vacuum trip, standard setting Hydraulic low vacuum trip

0.3 bar

Electrical low vacuum trip

0.3 bar

Electrical low vacuum trip bypass operation

0.6 bar

Seal steam supply system Pressure in seal steam header (above atmospheric)

35 mbar

Axial shift Alarm

± 0.5

mm

Trip

± 1.0

mm

Direction of rotation Anti clock wise when viewed from Front Pedestal towards the Generator

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The reheat stop and control valves arranged beneath the turbine operating floor in front of the turbine-generator unit are suspended at three points from girders in the upper foundation plate in such a way that they can follow thermal expansion of the steam lines. The ball-and-socket design of the tie caps (5) and spring body (9) and the disk spring stack (8) arrangement permit free movement of the reheat stop and control valve (3) in all

BHEL Haridwar

Hangers for Reheat Stop and Control Valves

directions. Tensile forces are taken up via the disk spring (8) and tie rod (6) by girders (1) that rest horizontally on shims in a recess in the foundation and are connected to the foundation via clamping plates. Tie rod (6) is screwed into rod cap (5) and when the correct elevation of the reheat stop and control valve (3) has been established, is secured to prevent turning.

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Steam Turbine Description Function

Steam Strainers are installed in the main steam lines and in the hot reheat lines from the boiler. They protect the admission elements of the HP and IP turbines from foreign objects, which could be picked up in the boiler or associated piping. Construction

Steam Strainer

parts. The end turns of the corrugated strip are then tacked to the T -section intermediate rings (3). The maximum mesh size of the strainer, which inner diameter determined by the height of the corrugations, is 1.6 mm. The effective area is made atleast three times the crosssectional area of the pipe. The strainer is used for both initial commissioning of the turbine and for regular operation.

The strainer screen (2) is made of corrugated strip wound on a frame. This

design offers a high degree of resistance, even to particles impinging at high velocity. The frame consists of two rings (1, 6) and a number of rods (5) welded between the rings. The rods are additionally held by reinforcing rings (4) welded inside them. The strainer is designed for a single direction of flow from the outside inwards. For longer strainers, the screen is made up of several BHEL Haridwar

Fig. 3 Corrugated metallic` strip

5.1-0816-00


Changeover Valve for Bleeder Check Valve

Function The function of the changeover valve is to manually operate the actuator of the bleeder check valve. Mode of Operation The trip fluid (connection x) holds the valve (10) in the upper end position (illustrated) against the force of the spring (8). The trip fluid flows via the holes in the valve to connection x 1 and then on to the actuator of the bleeder check valve. The valve can be moved downwards by means of hand wheel (1). In this way connection x1 is connected to the fluid drain ‘c’ and the fluid drains away from the actuator of the bleeder check valve. The spring of the actuator can then initiate the closing of the check valve. If the pressure drops at the trip fluid connection x, the spring (8) pushes the valve (10) downwards. In this way the fluid drain of the actuator is also freed. 1 2 3 4 5

Hand wheel Spindle Cap nut Bush Lip ring

6 Cover 7 Bush 8 Spring 9 Ball 10 Valve 11 Cover

c Drain fluid x Trip fluid x1 Trip Trip fluid to actuator

BHEL Haridwar

5.1-0840-00


Auxiliary Valve of Extraction Check Valve

Function The auxiliary valve controls the fluid supply to the extraction check valve actuators and its function is to give the check valves a signal to close in the case of a drop in load or trip-out so that steam can not flow out of bleeder lines back to the turbine. The auxiliary valve serves several check valves. Mode of Operation Trip fluid is admitted through connection ‘x’ on the body (10) (section A-B). Secondary fluid from follow-up pistons of main control valves is admitted to the spaces above and below the valve (11) through connection ‘b2’ As the pressure above and below the valve (11) are equal under normal conditions, the valve is held in the lowest position by the force of the spring (7).

BHEL Haridwar

With this position of the valve, the trip oil ‘x’ can flow to the other valves and as soon as these valves have been switched to the upper position by secondary fluid from follow-up piston of reheat control valves-on to the changeover valves of the extraction check valves (connection ‘x1‘). The check valves are then free to open. On a reduction in load, as mentioned above, the pressure above the valve (11) is reduced accordingly while the Pressure below the valve is retained for a while. This is made possible by the fact that the pressure reduction below the valve is retarded by the ball (15) and the pressure in the accumulator (connection ‘b’) until the equilibrium is re-established

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between the pressure in the accumulator and the new pulse fluid pressure (connection ‘b2’) via the equalizing passage in the cover (12). Owing to the brief differential surge, the valve (11) is forced upwards against the action of the spring (7), thus cutting off the trip fluid supply to the check valves and opening the fluid return. As a result of this, the check valves receive a closing impulse and close at reduced or reversed differential steam pressure. The valves (16), (section C-D) are acted upon from below (connection ‘b1’) by the load -dependent secondary fluid pressure of the control valves. If the secondary fluid pressure exceeds the value set by adjusting the springs, these valves are forced

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upwards against the action of the springs and open the path for the trip fluid to the changeover valves of the extraction check valves. The lift of the valves is limited by a collar at their lower end. By appropriately setting the springs (14) to the valves, it can be ascertained at which secondary fluid pressure i.e, at which turbine load, the check valves open or receive an impulse to close. If the pressure in the secondary fluid circuit drops, the valves are pushed downwards by the force of the springs and the inlet ports from the trip fluid circuit are cut off, the bleed valves thus receiving an impulse to close. The fluid in the line to the changeover valves can drain off through the opened fluid return ‘c’.


Rotary Vane Actuator for Reheat Swing-Check Valve

Function The function of the rotary vane actuator flanged to the swing-check valve is to open or close the swing-check valve fitted in the cold reheat line. Operation When the pilot valve operated by the transformer of the speed controller passes control fluid via connections ‘d’ to the interior of the actuator, the adjacent connection ‘d1’ is depressurized. The control fluid then flows through bores in the body into the two diametrically opposite chambers turning rotary vane (2) on actuator shaft (8) into contact with the

BHEL Haridwar

segments (1). This rotary movement, transmitted by actuator shaft (8) to shaft (3) of the swing-check valve via coupling (5;6) closes the swing-check valve. Conversely, the swing-check valve is opened when control fluid is admitted through connections ‘d1’ Seals, Fixing Actuator shaft (8) is guided in bushings (11) at both ends of the segments (1) and is sealed off by seal ring (10). The segments (1) are fixed in body (12) and in cover (13) by means of fitted pins. Leaking fluid ‘c’ is drained to the header.

5.1-0853-01


Pilot Valve for Rotary Vane Actuator of Swing-Check Valve

Function The function of the pilot valve is to control the admission of control fluid to the moving vane actuator in such a way that the swingcheck valve is operated in accordance with the pressure in the secondary fluid circuit. Mode of operation The swing-check valve is kept open as long as the pressure in the secondary fluid circuit does not drop below a definite limit value. If signal fluid enters the body via connection ‘b’, the valve (10) is lifted against the action of the spring (5). The initial tension of this spring and thus the point at which the swingcheck valve opens can be adjusted. If the valve (10) is lifted beyond the center position illustrated, the control fluid entering at connection ‘a’ flows on to a chamber of the actuator via connection ‘a2’ to open the swing-check valve. Connection ‘a1’ then communicates with the fluid return ‘c’ via passages in the body, permitting the fluid to drain away from the actuator chambers not supplied with control fluid. If the valve (10) drops below the center position illustrated, the control fluid will then be conversely admitted to the actuator chambers in such a way that the swing-check valve closes. To prevent the valve (10) from seizing in its sleeve (9) during operation control fluid is passed through the center bore and out through the tangential bores at the wheel disc (8) to impart rotary movement to the valve (10). For this reason, a thrust ball bearing (7) and a ball (13) is fitted for this purpose. 1 Throttle capillary tube 12 Slotted nut 2 Cap nut 13 Ball 3 Setscrew 4 Hood 5 Compression spring 6 Spring disc 7 Thrust ball bearing 8 Wheel disc 9 Valve bush 10 Valve 11 Bush c Return a Control fluid b Signal fluid a1 Control fluid(closes swing check valve) a2 Control fluid(opens swing check valve)

BHEL Haridwar

5.1-0854-00


Auxiliary Pilot Valve for Rotary Vane Actuator For Reheat Swing-Check Valve

Function The function of the auxiliary pilot valve for the pilot valve for the reheat check valve actuator is to control the admission of control fluid to the pilot valve in such a way that the swing-check valve is actuated in accordance with the pressure in the secondary fluid circuit. Operation The swing-check valve is kept open as long as the pressure in the secondary fluid circuit does not drop below a definite limit value. Secondary fluid entering body (9) via connection ‘b’ lifts spool (7) against the action of the spring (3). The initial tension of this spring and thus the point at which the swing-check valve opens can be adjusted. If spool (7) is lifted beyond its central position as illustrated, the control fluid entering at connection ‘a’ flows on via connection ‘a1” to connection ‘b’ of the pilot valve to open the swing- check valve via the rotary actuator. If spool (7) drops below its central position as illustrated, control fluid is admitted to the opposite chambers of the rotary actuator, so that the swing-check valve closes. To prevent spool (7) from seizing in its sleeve (6) control fluid is passed through the center bore in the spool during turbine operation and out through tangential bores in the upper part of spool (7) to impart rotary motion to the spool. A deep-groove ball bearing (5) between spool (7) and spring retainer (4) reduces friction from the rotary motion.

BHEL Haridwar

5.1-0855-00


Gland Steam Control Valve

Function One function of the gland steam control valve, which is situated in the gland steam pipe of the seal steam system, is to supply the shaft seals with seal steam during startup and in the lower load range. A further function is to keep the set pressure in the header constant in order to prevent air penetrating the vacuum of the shaft seals. Construction and Mode of Operation The control valve is operated by the piston of the electro-hydraulic actuator, which is moved in the open and closed direction by the pressure of the control fluid. The piston rod (2) is connected to the valve stem (7) via the coupling (4), the threaded cap (5) and cover (6). The steam flow is regulated by the internal pilot valve, which is integral with the valve stem, and the main cone (13). The position of the valve is shown on the lift scale (3). The valve stem (7) and valve cone (1 3) are guided in the bushing (11). Any leakage steam arising in the upper part of the bushing (11) is conducted to the header. 1 Electr-hydraulic actuator 2 Piston rod 3 Lift scale 4 Coupling 5 Threaded cap 6 Cover 7 Valve stem with pilot valve 8 Packed stuffing box 9 Valve yoke 10 Base ring with packing rings 11 Bushing 12 Valve cover 13 Valve cone 14 Valve casing c Leakage steam

BHEL Haridwar

5.1-0860-01


Leakage Steam Control Valve

Function The function of the leakage steam control valve, which is situated in the leakage steam pipe of the seal steam system, is to drain excessive steam from the header. Construction and Mode of Operation The control valve is operated by the piston of the electro-hydraulic actuator, which is moved in the open and close direction by the pressure of the control fluid. The piston rod (3) is connected to the valve stem (8) via the coupling (4). The packing rings (10) and the bushing (12) seal the passage of the rod to the outside and guide the valve stem (8) during the opening and closing movement. 1 Electrohydraulic actuator 2 Valve yoke 3 Piston rod 4 Coupling 5 Threaded piece 6 Cover 7 Lift indicator 8 Valve stem 9 Stuffing box 10 Base ring with packing rings 11 Valve cover 12 Bushing 13 Valve casing

BHEL Haridwar

5.1-0870-01


Technical Data Steam & Casing Temperatures

Steam Temperatures Rated value, Annual average

Long-term value, subject to annual average

400 hrs. per year

80 hrs. per year Max. 15 min in individual case

Main steam at HP stop valve inlet

537.0

545.3

551.0

565.0

°

HRH steam at IP Stop valve inlet

537.0

545.3

551.0

565.0

°

Unit C C

Steam Temperatures Rated value ♦

Long term operation

80 hrs. per year, Max. 15 min. in individual case

In special cases at no load

HP turbine exhaust

336.2

338.2

428.2

500.0

Extraction 6

336.2

338.2

428.2

500.0

Extraction 5

410.6

415.6

450.6

°

Extraction 4

288.2

298.2

338.2

°

Extraction 3

189.9

202.9

249.9

°

Extraction 2

132.5

152.5

197.5

°

Extraction 1

72.2

92.2

142.2

°

LP turbine exhaust

46.1

70.0

70.0

°

Unit

♥

°

♥

°

C C C C C C C C

Long-term operation: upper limit value permissible without time limit. ♦

These values correspond to 500 MW Load with 3% makeup and 0.1013 bar back pressure with all heaters in service and rated steam conditions.

♥

Only valid for the no load period with high reheat pressure after trip-out from full load operation. For individual case approx. 15 minutes. The turbine is immediately re-loaded or the boiler immediately reduced to minimum load if no load operation is maintained.

Casing Metal Temperatures Wall Temperatures

Alarm at

Machine must be shut down at

HP turbine casing exhaust

485

500

Outer casing of LP cylinder

90

110

Unit °

C

°

C

0

Spray water to LP turbine must be switched on at 90 C

BHEL Haridwar

5.1-0101-63/1

Steam


Function The Function of the main trip valve is to open the trip fluid circuit in the event of abnormal conditions, thereby closing the valves and thus shutting off admission of steam to the turbine. Construction The main trip valve consists of mainly two valves (12) that slide in the casing (11) and are loaded by the springs (5,6). The valves

BHEL Haridwar

Main Trip Valve

(12) are designed as differential pistons being forced tightly against the body assemblies (10) by the rising pressure of the fluid. Control fluid flows into the casing (11) via connection ‘a ’ and with a tripping device latched in (in the position shown), into the trip fluid circuit via connection ‘x ’. ’. The trip fluid circuit leads to the stop valves and the secondary fluid circuits. Via passage drilled in the body (11) (Section A-A) fluid flows to the auxiliary trip fluid circuit, which leads to the hydraulic protection devices.

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Operation When starting the unit, the valves (12) are lifted by the aux. start up fluid (connection ‘u1 ‘) against the force of the springs (5,6) and forced tightly against the assemblies (10). In this way pressure is build up in the trip fluid circuit ( x ) and the auxiliary trip fluid circuit (x1 (x1). ). The pressure in the auxiliary trip fluid circuit keeps the valve in the position shown while the aux. start up fluid drains through the start up device. Should the fluid in the pressure in the auxiliary trip fluid circuit drop below a specific value for any reason (e.g. by tripping of a protection device) the valves

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(12) move downwards due to the spring force and their own weight, thus connecting connections ‘x ‘x’ and ‘x ‘x1’ with the fluid back flow ‘c ’. ’. This depressurizes the trip fluid circuit which causes the main and reheat stop valves to close. The fluid supply to the secondary fluid circuits is also shut off, thus causing the control valves to close. The two valves (12) work independently of each other so that even if one valve fails the function of the tripping device is not impaired. The limit switches (1) transmit electrical signals to the control room.


Emergency Trip Valve for Manual trip out

The emergency trip valve enables the machine to be manually tripped out. The valve consists of the valve cone (8), which slides in the bushing (9) and is loaded by the spring (7), and the ball head (1) with the spindle (4). During normal operation the valve (8) is forced tightly against the bushing (6) by the pressure of the auxiliary trip fluid arising at connection ‘x1 ‘. To actuate the trip, the ball head (1) is pushed downwards. This opens the valve and connects the auxiliary trip fluid circuit (connection ‘x1 ‘) with the fluid back flow ‘c’, The drop in pressure in the auxiliary trip fluid circuit actuates the emergency tripping device. The limit switch (2) shows the tripping of the valve. On start-up, before the auxiliary trip fluid is pressurized, the valve (8) is forced upwards against the bushing by the auxiliary start-up fluid (connection ‘u1‘). 1 2 3 4 5 6 7 8 9 10 11

Ball head Limit switch Cover Spindle spring Bushing Spring Valve cone Bushing Casing Cover

x1 Auxiliary trip fluid u1 Auxiliary start-up fluid c

Return fluid

BHEL Haridwar

5.1-0911-00


Solenoid Valve for Remote Trip-out

Function The solenoid valve is installed in the auxiliary trip fluid line to the automatic trip gear and, when operated, causes the auxiliary trip fluid circuit to be opened and the turbine stopped, The solenoid valve is remote-controlled electrically, e.g. from the control room or from a protective device. Construction The directions of flow are indicated by arrows on the body. The solenoid sleeve (4) is bolted to the casing (6) and is inserted in the magnet casing (1) with the armature (3). The complete valve element is placed in the body (6) and held by the plug (11). The two valve discs (8) seal the valve seats (9). The solenoid valve and the line to the automatic trip gear are ventilated by means of the screw (12). Mode of Operation When the solenoid (1) is not energized, the armature (3) is moved downwards by the spring (2) so that the valve disc (8) is pressed against the valves seats (9) to provide sealing. The solenoid valve is operated by energizing the solenoid (1). The armature and the valve discs are drawn upwards against the force of the spring (2) so that the auxiliary trip fluid ‘a’ is linked with the drain ‘c’ and the pressure in the line to the automatic trip gear collapses. 1 2 3 4 5 6 7 8 9 10 11 12 a c

Magnet casing Spring Armature Solenoid sleeve Hexagonal nut Casing Ring Stem with two valve discs Valve seat O-ring Plug Ventilation screw Auxiliary trip fluid to automatic trip gear Drain

BHEL Haridwar

5.1-0912-00


Over speed Trip

Function and Construction The function of the overspeed trip is to stop the turbine when the permissible speed is exceeded. It is fitted in the turbine rotor (7) and consists of the eccentric bolt/striker (4), adjusting screw (6), spring (5) and the screw plug (1). Mode of Operation The overspeed trip mechanism is set by the adjusting screw (6). By appropriate adjustment of the screw, the center of gravity of bolt/striker (4) is positioned eccentrically to the turbine shaft so that below the tripping speed the bolt is held in the position shown by the spring (5) against the centrifugal force. In this position, the bolt bears against the screw plug (1). If the turbine rotational speed exceeds the overspeed setting, the centrifugal force overcomes the force of the spring (5) and forces the bolt/striker (4) out of the turbine rotor (7). This activates the turbine automatic stop mechanism.

1 2 3 4

Screw plug Guide bushing Guiding foil Bolt/striker

5 Spring 6 Adjusting screw 7 Turbine rotor 8 Guide ring

Fig. 1 Arrangement of overspeed trip in turbine rotor

BHEL Haridwar

5.1-0920-00


Overspeed Trip Releasing Device

Function

Turbine Trip by Overspeed Trip Device

The function of the overspeed trip releasing device is to open the auxiliary trip fluid circuit and thereby shut down the turbine when an overspeed is reached which would subject the rotor to high centrifugal force.

When the overspeed trip operates, the eccentric bolts/striker fly out radially and strike pawls (12). The impact of the bolt/striker rotates the pawls outwards against the force of torsion springs (11). The latches of the pawls release rod (8) which, in turn, moves towards the shaft (13) due to the force of spring-loaded pilot valve (3) and force of the auxiliary trip fluid ‘x 1’. This movement opens fluid drain ‘c’ to the auxiliary trip fluid and the resulting loss in pressure and trips the turbine. The electrical trip signal is transmitted to the control room by the limit switches (1).

Construction The overspeed trip releasing device located in the bearing pedestal consists of valve bodies (4,10), pilot valve and rods (3,5,7,8), pawls (12) and limit switch (1). The bellows 16) on the pilot valves and rods prevent hydraulic control fluid from entering bearing pedestals and lubrication system. When the turbine is started up, the pilot valve, rods and pawls are latched by auxiliary start-up fluid ‘u1 ‘.

BHEL Haridwar

5.1-0921-00/1

Testing the Overspeed Trips for Free Movement Proper functioning of the overspeed trips is important since severe damage may result from excessive over speeds. The overspeed trip test device makes it possible to check the bolts/strikers as well as pilot valves and rods (3, 5, 7, 8) without interrupting operation of the turbine.

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Start-up Before restarting the turbine following a trip, latch in the overspeed trip. This is done by admitting auxiliary startup fluid ‘u1’ into pilot valve body (4) and forcing the respective pilot valve (3) outwards until rod (8) engages the latch of the pawl. The auxiliary start-up fluid flow is interrupted and auxiliary start-up fluid flows via a hole to fluid drain ‘c’.

Steam Turbine Description Function The function of the overspeed trip test device is to test and exercise the overspeed trip. The overspeed trip consists of bolts/strikers which protrude against the force of a spring under the effect of centrifugal force during an overspeed condition. The bolt/striker strikes a pawl and thus opens the auxiliary trip fluid circuit and in turn trip fluid circuit so that the stop and control valves immediately interrupt the admission of steam to the turbine. Perfect

BHEL Haridwar

Overspeed Trip Test Device

functioning of the overspeed trip is of the utmost importance. Construction The overspeed trip test device consists of three pilot valves (4,10, 11) combined in valve block (12). Pilot valve (11) is held in the position by spring (9), which bears against guide piece (15) and rod (7). In this position auxiliary trip fluid can pass to the overspeed trip release device via connection ‘x’ and ‘x1‘. If the pilot valve (11) is pushed

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inwards and held by means of the knob (6), the auxiliary trip fluid circuit (connection ‘x’ and ‘x1’) is separated from the overspeed trip release apart from a small quantity of fluid which is permitted to pass to fill up the empty pipe after the test operation. This prevents the emergency trip from being actuated by the overspeed trip.

bore of the pilot valve. By means of handwheel (5), the pilot valve (10) can be moved inwards so that the passage from connection ‘a2’ is blocked from drain ‘c1’. Control oil can now flow from connection ‘a1’ via the bushing (13) and the pilot valve (10) to connection ‘a2’ and the bolts/strikers of the overspeed trip.

Pilot valve (10) performs the function of admitting test oil to the eccentric bolts/strikers of the overspeed trips, causing them to protrude from the turbine shaft during the overspeed trip test operation. Pilot valve (10) is guided in guide bushings (13,14). A center bore with radial openings is provided in the pilot valve. An annular chamber in the bushing (13) is connected to test oil connection ‘a1’. In the position shown oil is prevented from entering the

Pilot valve (4) is used for resetting the overspeed trip release device after the test operation. When pilot valve (4) is pushed inwards against the force of spring (3), control fluid can flow from connection ‘a’ to ‘u1, thus latching in the overspeed trip device. During start-up, connections ‘u’ and ‘u1’ provide a passage for auxiliary start-up fluid for latching in the overspeed trip release device. After the test operation, the pilot valves (4,11) are blocked.

5.1-0922-00/2

Steam Turbine Description Function The purpose of the low vacuum trip is to operate the main trip valve when a failure of vacuum occurs in the condenser, thus tripping out the main and reheat stop and control valves and shutting off the supply of steam to the turbine within the shortest possible time. Operation The condenser vacuum is connected via ‘I’ (connection to condenser) to the top side of the diaphragm (8). The space below the diaphragm is at atmospheric pressure. Upon failure of the condenser to maintain proper vacuum, diaphragm (8) is forced downwards by the increase in pressure and the force of the spring (7) against the force of spring (10), thus moving valve (9) downwards. This establishes a connection between ‘x1’ (control fluid) and drain ‘c’ so that the auxiliary trip fluid circuit is

BHEL Haridwar

Low Vacuum Trip

depressurized and the main trip valve operates. Concurrently, valve (11) actuates the limit switches (15), which initiates an alarm contact. The range in which the vacuum safety device operates can be varied by adjusting the initial tension of the spring (7) by means of the adjusting screw (5). In order to isolate the auxiliary trip fluid circuit during starting, auxiliary pilot valve (9) is lifted by means of the spring (10) so that drain ‘c’ is shut off, thereby establishing pressure in the auxiliary trip fluid circuit when no vacuum exists. As primary oil pressure builds up with the increase in turbine speed, piston (2) is forced into the lower position. This lower position is reached when the speed is still far below the rated value at which time the low vacuum trip safety device is ready to operate.

5.1-0935-00


Technical Data Bearing Metal Temperatures Vibration, Weights

Bearing babbit metal temperatures Alarm at °

Operation temperature below 75 C

°

90 C

°

100 C

°

110 C

Operation temperature 75 to 85 C Operation temperature 85 to 90 C °

Operation temperature above 90 C

Machine must be shut down at °

130 C

°

130 C

°

130 C

°

130 C

115 C

°

°

°

Vibration Absolute bearing housing vibration Standard alarm setting

Absolute shaft vibration 50 µm above normal level

Maximum alarm setting

84 µm

200 µm

Limit value for tripping

106 µm

320 µm





The normal level is the reproducible vibrational behaviour typical for the machine & dependent on the operating conditions. Vibration readings indicated in control room are peak to peak. The above values are also given in peak to peak.

Weights HP turbine, completely assembled

95 T

IP turbine, top half outer casing

26 T

IP turbine, top half inner casing, complete with blading

16 T

LP turbine, top half outer casing complete

43 T

LP turbine, top half inner outer casing, complete with blading, guide blade carriers & diffusers

37 T

HP turbine rotor, complete with blading

16 T

IP turbine rotor, complete with blading

23 T

LP turbine rotor, complete with blading

100 T

Main stop and control valve, complete with servo motors, without bend & pipe section

22 T

Reheat stop and control valve, complete with servo motors, without bend & pipe section

32 T

All weights have been calculated with safety allowances. Slings chosen must provide sufficient security.

BHEL Haridwar

5.1-0102-63


Condenser Condens er Safety Device

Function Function The function of the condenser safety device situated in the control fluid circuit of the bypass control system is to protect the condenser, when there is an excessive increase in pressure in the condenser, by opening the control fluid lines so that the resulting drop in pressure causes the bypass valves to close. Mode of Operation The steam space in the condenser is connected with the spring space above the diaphragm (5) via connection ‘I’. The space below the diaphragm is at atmospheric pressure. If the pressure in the condenser increases excessively, the diaphragm (5), and thus the valve (6), is forced downwards out of the upper end position by the increasing pressure and the force of the spring (4). This shuts off the connection ‘a 1” to the bypass valve from connection. ‘a’ which is from the converter and connects it to drain ’c’. The pressure range in which the vacuum safety device operates can be varied by adjusting the initial tension of the spring (4) by means of the adjusting screw sc rew (2). During commissioning the valve (6) is automatically moved into the upper end position, where it keeps the control fluid circuit closed, as soon as the negative pressure in the condenser falls below the preset value. In order to be able to close the control fluid circuit when there is still insufficient vacuum in the condenser, the valve is lifted via the lever (10) and cam (9) but is not yet brought into its upper end position. As already mentioned, this end position is not reached until there is sufficient vacuum. After this, the lever (10) and cam (9) drop down and do not impair the functioning of the vacuum safety device. Any leakage fluid can drain off through passages in the valve sleeve (7) and the casing (8).

BHEL Hardwar

5.1-0940-00


Solenoid Valve for Temperature Controlled Interlock

Function When there is an unallowable rise in condenser temperature due to lack of injection water a temperature sensor situated in the condenser dome sends electric signals to the solenoid valve which open the signal fluid circuit of the bypass valve actuators, thereby closing the bypass valves so that the steam flow to the condenser is interrupted. Mode of Operation During normal operation, the control fluid ‘a’ holds the main control valve (7) against the force of the compression spring (8) in the center position as shown here, This provides the connection between the signal fluid from pressure switch for injection water ‘b’ and the stop and control valve operator of the bypass stop valve ‘b1 “, If the temperature in the condenser rises to an unallowable value, the solenoid valve (3) is moved downwards against the force of the compression spring (4) so that the control fluid ‘a’ arising before the main control valve (7) is connected with the drain ‘c’. Simultaneously, the control fluid ‘a’ can flow behind the main valve (7) so that the main valve moves forwards against the force of the compression spring (6) and the signal fluid circuit ‘b1’ is opened and connected to the drain ‘c’ and the bypass stop and control valve closed’.

BHEL Hardwar

5.1-0950-00

Vacuum Breaker for Reducing the Running Down Time of the Turbine


Function With normal shut down or tripping of the machine, the function of the vacuum breakers is to cause an increase in condenser pressure by conducting atmospheric air into the condenser together with bypass steam flowing into the condenser from the bypass station. When the pressure in the condenser increases, the ventilation of the turbine blading is increased, which causes the turbo set to slow down so that the running down time of the turbo set and the time needed for passing through critical speeds are shortened. Total Vacuum Breakers In special cases requiring a rapid shut down of the turbo set, the total vacuum breaker is employed. Electrical Breaker

Control

of

Total

Vacuum

So that the vacuum can also be broken without limitation due to condenser pressure, a manual key is provided. This key opens the vacuum breaker valve. However, it can not go into the closing position until the close key provided for closing is used. This control enables a complete equalization of condenser and ambient pressure. Automatic Control The vacuum breaker is also actuated automatically by the turbine fire protection system to shut the turbo set down more quickly. It is switched back manually using the close key in this case. Mode of Operation of Vacuum Breaker When the magnet is not excited, the solenoid valve is switched to open. The control medium arising holds the vacuum breaker valve in the closed position by means of the power piston. When the pressure drops the vacuum breaker is opened by spring force.

BHEL Haridwar

5.1-0960-00/1

Opening Process When the magnet is excited the control medium is without pressure so that the control medium in front of the solenoid valve is connected with the drain ‘c’. The piston (3) and thus the valve disc (19) are moved upwards by the force of the spring (5) (Fig. 2). Closing Process When the magnet is not excited the valve is closed by the control medium arising. The pressure of the control medium ‘a’ via the piston (3) presses seal ring (17) arranged in the valve disc (19) on to the valve seat (20) against the force of the compression spring (5). 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Piston cover Stop Piston Valve stem Compression spring Piston bottom Limit switch Spacer column Cap nut Gland seal Pecking Valve cover Bushing Valve calling Screw coupling Divided ring Seal ring Disc guide Valve disc Valve seat

a Control medium I Inlet for atmospheric air I1 Atmospheric air flowing into condenser

5.1-0960-00/2

Fig. 2 Drawing Showing Function of Vacuum Breaker


Function The pressure switch monitors the injection water pressure. When the injection water pressure drops below the set rated value, the control fluid is interrupted and thus the LP bypass valve closed. Construction The pressure switch consists of a casing in which a measuring system, a counterconnected system for adjusting the rated value, a knife-edged lever (4), a nozzle (11) and a slide valve (12) are installed. The measuring system consists of bellows (2) upon which the injection water pressure ‘I’ acts and these influence the knife-edged lever (4) via a pushrod (3). The cylindrical pin (10) is the pivot point of knife-edge lever (4). The compression spring (6), the tension

BHEL Hardwar

Pressure Switch for Injection Water

of which is set to the appropriate rated value, is provided as a counter force. Mode of Operation The lever (4) diverts the fluid jet leaving the nozzle (11) so that there is no fluid pressure above the piston surface of the slide valve (12). If the pressure drops below the rated value, however., the lever allows the jet of fluid to enter the bushing (13) which subjects the piston surface of the slide valve (12) to fluid pressure, The slide valve is thus pushed downwards against the force of the spring (14) into the shut-off position in which control fluid ‘a2’ is connected to the return flow ‘c’, This process causes the signal fluid to be cut off and thus the bypass valves to be closed. If necessary, the knife-edged lever (4) can be fixed in its end position by means of the lever (17).

5.1-0970-00


Changeover Valve for Testing Device

Function The function of the changeover valve is to shut off the flow of trip fluid into the trip fluid circuit while the protective devices are being tested for proper operation by means of the Automatic Turbine Tester (ATT) and to allow control fluid ‘a’ to flow in so that the stop valves do not close when the safety devices respond. Mode of Operation During normal operation, the control fluid ‘a1’ in the space under the lower piston (8) of the changeover valve keeps the valve in the upper end position shown here. In this way, connection ‘x’ is connected with connection ‘x1’ and trip fluid can flow into the trip fluid circuit. The space above the piston (6) (connection ‘a’) remains depressurized during normal operation. When safety devices are checked for proper operation, the space below the lower piston (8) is depressurized by means of a solenoid valve and control fluid ‘a’ enters the space above the upper piston, which moves the valve into the lower position. Due to the connection now made between connections ‘a’ and ‘x1’, control fluid ‘a’ can flow freely into the trip fluid circuit, which keeps the stop valves open for the duration of the test. Two limit switches (1) transmit the position of the valve to the control room.

1 2 3 4 5 6 7 8

Limit switch Piston rod Seal Bushing Inset Upper piston Sliding bushing Lower piston

BHEL Haridwar

9 Body 10 Cover a Control fluid a1 Control fluid c Fluid drain x Trip fluid from tripping device x1 Trip fluid to trip fluid circuit

5.1-0980-00

Oil Supply System MAV System Description


Accompanying system diagram (Drawing No. 2-13100-91101 on Sheet No. On Sheet No.5.1-1000-63/4) Process engineering functions of the hydraulic and lubricating oil system

Description and function of components of the hydraulic and lubricating oil system The components of the hydraulic and lubricating oil system and their function are described below:

The hydraulic and lubricating oil system has the following process engineering functions: Lubrication and cooling of the turbine and generator bearings with turbine oil drawn from the main oil tank by the oil pumps and forwarded via cooler and filter to the bearings; pressures and flow rates are set with throttle valves.

Main oil tank The oil necessary for operation is stored in the main oil tank. The oil pumps draw the turbine oil from the main oil tank and forward it to where it is needed. Large solid contaminants in the returning oil are removed by the strainers in the main oil tank before the oil reaches the suction section of the main oil tank. Air and oil vapour are drawn out of the main oil tank by the oil vapour extractor. The main oil tank level is monitored. The turbine oil can be drained from the main oil tank. • Injector MAV21 BN001 

•

 

Supplying motive oil to turning gear. Backflow of the turbine oil to main oil tank.

Components of the hydraulic and lubricating oil system

MAV21 BN002

In addition to piping, manually operated valves, and monitoring equipment, the following tanks, pumps, drives, coolers, filters and valves are necessary for operation of the hydraulic and lubricating oil system: • Main oil tank and oil pumps Main oil tank Injector feeder pump MAV 21 BN001 Injector feeder pump MAV 21 BN002 Main oil pump driven by MAV 21 AP001 the turbine shaft Auxiliary oil pump 1 MAV22 AP001 Auxiliary oil pump 2 MAV23 AP001 Emergency oil pump MAV24 AP001 • Turning gear oil supply valve 

Oil coolers and oil filters .Oil cooler 1 Oil cooler 2 Double multiport butterfly valve Oil temperature control valve Lubricating oil filter

auxiliary oil pump 1 auxiliary oil pump 2

MAV51 AA001

MAV41 BC001 MAV41 BC002 MAV41 AA521 MAV41 AA001 MAV42 BT001

Lubricating oil supply to bearings MAV42 lubricating oil valve AA502 

upstream of turbine bearing 1 lubricating oil valve upstream of turbine bearing n lubricating oil valve upstream of generator bearing n

Injector is located upstream of the main oil pump, which is driven by the turbine shaft. The injector is a submersible pump, which draws the turbine oil directly from the main oil tank using turbine oil and forwards it to the main oil pump under positive pressure. • Main oil pump MAV21 AP00I The main oil pump is driven by the turbine shaft and assumes the function of oil supply just before the turbine generator unit reaches rated speed. • Auxiliary oil pumps



MAV22 AP001 MAV23 AP001

The auxiliary oil pumps are submersible pumps, which draw oil directly from the main oil tank. One of the two auxiliary oil pumps supplies the hydraulic and lubricating oil system with turbine oil as long as the main oil pump is unavailable when turbine generator speed is too low for supplying oil, e.g., during start-up or shutdown of the turbine. generator or during turning gear operation MAV24 AP001 Emergency oil pump The emergency oil pump is a submersible pump, which draws oil directly from the main 'oil tank. The turbine oil is forwarded by the emergency oil pump while bypassing the oil cooler and oil filter in the lubricating oil system when the auxiliary oil pumps are unavailable for turbine oil supply due to a fault in three-phase power supply.

see below see below

There is a lubricating oil throttle valve (coded according to the system diagram) in the lubricating oil line upstream of every turbine or generator bearing.

BHEL BHEL HARDWA HARDWAR R

5.1-1000-63/1

•

MAV51 AA001 Motive oil valve of the turning gear The motive oil valve of the turning t urning gear is actuated by the associated motor.

The bearing-specific oil flow rates are set with the throttle valves in the lubricating oil lines upstream of the turbine and generator bearings. Piping and valves



• Oil coolers

oil cooler 1 oil cooler 2

MAV41 BC001 MAV41 BC002

One oil cooler is always in operation to remove the heat generated by the turbine and generator bearings from the turbine oil. The second oil cooler is on standby. Changeover to the standby oil cooler must be made when the oil cooler in operation clogs or leaks., The maximum flow rate of the cooling water .through the oil cooler in operation must be maintained for good heat transfer and preventing deposits in the cooler tubes. 





MAV41 AA001 Oil temperature control valve The lubricating oil temperature upstream of the turbine and generator bearings is maintained by the oil temperature control valve.

The oil temperature control valve is a multiport valve in which hot and cold turbine oil is mixed to obtain the desired lubricating oil temperature of approx. 45-degree C downstream of the control valve. Duplex lubricating oil filters MAV42 BT001 lubricating oil filter

The differential pressure across the lubricating oil filter in operation is a measure of fil ter clogging. Double multiport butterfly valve The double multiport butterfly valve is the changeover valve for the lubricating oil filters. 

Piping, oil coolers, and oil filters are equipped with drain valves. Oil coolers and oil filters can be filled and vented. Air and oil vapour is extracted from the return lines. Sampling valves are provided for taking oil samples. Passive turbine fire protection The main oil tanks, oil pumps, oil coolers, oil filters, and important oil system valves are installed in separate compartment of the turbine building. This compartment is designed with a sump for catching leak oil. The sump volume is the same as that of the main oil tank. The oil lines are laid in ducts, which can collect leak oil and prevent it from contacting machine parts on which it can ignite.

MAV41 AA521 Double multiport butterfly valve The double multiport butterfly valve is the changeover valve for the oil coolers.

One element of the switchable duplex lubricating oil filter is always in operation to protect the turbine and generator bearings against solid contaminants.



The turbine oil is supplied to where it is needed through piping. The dimensions of the oil lines are a function of oil velocity and the oil pressure during operation.

Lubricating oil throttle valves upstream of turbine and generator bearings

Information for operation and maintenance Technical Data



The Technical information:

Data

contain

the

following

- nominal capacity of the main oil tank - reference values for the capacity of the lubricating oil system including the oil-side volume of the system tanks, coolers, filters, and piping, which are filled during operation - highest and lowest oil level in the main oil tank during turbine generator operation at rated ,s.peed - reference values for the amount of oil which must be filled into the main oil tank for operation of the hydraulic and lubricating oil system and for the amount of oil necessary for flushing the oil system during commissioning or inspection and overhaul - manufacturer, type designation, and design data of oil pump motors - setpoint and limit values of the lubricating oil temperature for operation and shutdown of the turbine generator unit

5.1-1000-63/2

-

-

manufacturer, type designation , and fineness of the lubricating oil system filter

-

reference values for oil heatup in the bearings and bearing-specific oil requirement

auxiliary oil pump must be switched off. Extended parallel operation of the main and auxiliary oil pumps shall be avoided. Sub-loop controls of the hydraulic and lubricating oil system.



Dimensioning of the main oil tank



The main oil tank is dimensioned so that the total oil in the tank is not recirculated more than 8-10 times per hour. The turbine oil in the system takes up air during every recirculation. This air is released from the turbine oil in the course of the dwell time in the main oil tank. Large amounts of air in the turbine oil are either due to an excessive turbine oil recirculation rate or due to an inadequate air release property of the turbine oil. 

-

All oil pumps of the hydraulic and lubricating oil system driven by electric motors are controlled by the switching commands of the associated sub-loop controls. The oil pumps should always be switched on in a certain sequence to ensure the lubricating oil supply to the turbine and generator bearings in the event of a drop in oil pressure in the hydraulic or lubricating oil system. The sub-loop controls of the oil pumps must be in AUTO mode as long as the line of shafting is driven by steam or the turning gear.

Setting of the throttle valves of the hydraulic and lubricating oil system

The throttle valve settings for the hydraulic and lubricating system are optimised during initial startup when the turbine generator unit is running at rated speed:

-

-

The INJECTOR (MAV21BN001 / MAV21BN002) ensure a positive pressure of approx. 0.2 bar in the suction line immediately upstream of the main oil pump.

Sub-loop controls for the oil Pumps





Changeover of oil coolers and filters Standby oil coolers and standby lubricating oil filters must be filled and vented before changeover. Venting of the oil coolers The oil-side vent of the oil cooler in operation must be open.

Lubricating oil throttle valves upstream of the turbine and generator bearings, e.g., lubricating oil throttle valve upstream of the first turbine bearing MAV42 AA501. The mass flows of the oil necessary for lubricating and cooling are set using the lubricating oil throttle valves upstream of the turbine and generator bearings in accordance with the reference values given in the Technical data. The lubricating oil throttle valve upstream of every bearing should be adjusted so that the turbine oil in the bearing heats up to approx. 20 K.



Characteristics of the main and auxiliary oil pumps are designed with respect to one another so that the main oil pump assumes the oil supply just before the turbine generator unit reaches rated speed. If the auxiliary oil pump is still in operation when the takeover criteria of the main oil pump are fulfilled, the

5.1-1000-63/3


Technical Data Oil Supply, Oil Pumps

OIL supply 3

Main oil tank, rated capacity

25/40

M

First oil filling (estimated)

53

M

Flushing oil quantity (estimated)

32

M

Oil cooler for operation, number

1

No.

Oil cooler for reserve, number

1

No.

38 45 47

°C

Oil temperature at cooler outlet, unit in operation

Min. Normal Max.

Oil temperature at cooler outlet, unit shut down

Max.

75

°C

Temperature rise of oil in bearings

Normal Max.

20 25

°C

Estimated oil requirement for Bearing 1

0.8

dm /s


15.4

dm /s


4.55

dm /s


9.29

dm /s

Estimated oil requirement for Generator front bearing

7.92

dm /s

Estimated oil requirement for Generator rear bearing

7.92

dm /s

Estimated oil requirement for Exciter bearing

0.70

dm /s

Estimated oil requirement for Hydraulic Barring at 4.5 – 5.0 bar

57.4

dm /s

Duplex oil filter- full flow, Type: RFLD W 4020ZAV 25 VZ 1.0 Make: MS HYDAC FILTER TECHNIK GMBH.

1

No.

Filtration particle size of duplex filter element

37

µm

Filtration particle size of main oil tank filter element

250

µm

Safety valve in jacking oil system, setting

200

bar

Pressure limiting valve in jacking oil system, setting

178

bar

BHEL Haridwar

3

3

3

3

3

3

3

3

3

3

5.1-0103-63/1

Steam Steam Turbine Description

Accompanying system diagram

(Drawing No. 2-13100-91103 on Sheet No. 5.11001-63/2 Process engineering function of the oil vapour extraction system Oil vapour forming, for example, due to turbulent flow of turbine oil in the bearing pedestals and due to release of entrained air in the oil return lines and main oil tank is removed by one of the two extractors of the oil vapour extraction system. The negative pressures above the oil surface in the bearing pedestals, oil return lines, and main oil tank prevent turbine oil or vapour from escaping into the atmosphere. Turbine oil and oil vapour are separated in the oil separator of the oil vapour extractors so that the air released into the atmosphere is virtually free of oil. Components of the oil vapour extraction system In addition to piping piping the following equipment is necessary for operation of the oil vapour extraction system :

Oil System MAY Oil Vapour Extraction System System Description Oil vapour extractors oil vapour extractor 1 MAV82 AN001 oil vapour extractor 2 MAV82 AN002 check valve of MAV82 AA001 oil vapour extractor 1 check valve of MAV82 AA002 oil vapour extractor 2 One of the two single-stage oil extractors, whose characteristic is matched to volumetric flow of oilenriched air, must be in operation as long as the generator is filled with hydrogen. The check valves downstream of the oil vapour extractors prevent the extractor in operation from drawing in air tough the standby extractor. Oil separator MAV82 BT001 Virtually all of the turbine oil in the vapour phase is removed by the oil separator. Inadequate oil separation is usually caused by excessive volumetric flow of oil vapour. Consequently, the throttle valves in the oil vapour extraction lines must not be opened too far and the lid of the main oil tank must be airtight. Adjustable throttle valves in the oil vapour extraction lines Volumetric flow in the oil vapour extraction lines is adjusted with throttle valves so that negative pressures in the bearing pedestals equal the reference value of approx. 5-10 mm of water column. The negative pressures in the oil return lines and main oil tank must be matched to this reference value without degrading oil separation in the oil separator due to excessive volumetric flow. If the pressure in one bearing pedestal or in the main oil tank is considerably lower than the reference value, there is a risk of dust, moisture, or leak off steam from the immediate atmosphere being drawn into the oil system. 



Oil vapour extractors and oil separator oil vapour extractor1 MAV82 AN001 oil vapour extractor2 MAV82 AN002 throttle valve upstream of MAV82 AA511 oil vapour extractor1 throttle valve upstream of MAV82 AA512 oil vapour extractor2 check valve of MAV82 AA001 oil vapour extractor1 check valve of MAV82 AA002 oil vapour extractor2 oil separator MAV82 BT001 Throttle valves downstream of bearing pedestals bearing pedestal 1 MAV81 AA501 bearing pedestal 2 MAV81 AA503 bearing pedestal 3 MAV81 AA505 gen. brg. pedestal MAV81 AA507 exciter bearing pedestal MAV81 AA511 Throttle valves of oil return lines throttle valve MAV81 AA521 throttle valve MAV81 AA522 





Description and function of components of the oil vapour extraction system The components of the oil vapour extraction system and their function are described in the following :

BHEL, Hardwar

Notes on operation of the oil vapour extraction system During extended shutdowns the oil system fills with air as the oil slowly flows back into the main tank. When the system is started up again by activating the pump, resuming oil flow, the air is driven out and accumulates in the bearing pedestals. Pressure build-up in the bearing pedestals and discharge of oil through the seal rings can be prevented by filling the system using the emergency oil pump.

5.1-1001-63/1

Duplex oil filter for jacking oil, Type: DFDK 330

1

No

37

µm

Make: M/s HYDAC Filtration particle size of jacking oil filter

Jacking oil pump, cut-in and cut-out speeds 



Jacking oil pump must be in operation at turbine speeds below approx. 510 rpm to avoid avoid damage to bearings. Jacking oil pump pump should should be cut-out at speeds above approx. 540 rpm.

Oil pumps Main oil pump

Auxiliary oil pump

DC emergency oil pump

Jacking oil pump

Quantity

1

2

1

AC: 1

Make

BHEL

KBL

M&P

Tushaco

Type

350m3/hr

KPDS 125/26L

4/5 SR 12KL Model 70

T 38/46

Rated Capacity 87.48

100

30

1.85

dm /s

Discharge pressure

8.4

6.3

2.3

178

bar gauge

Speed

3000

2970

1500

Drive

Turbine

AC motor

DC motor

5.1-0103-63/2

DC: 1

2900 AC motor

DC motor

3

rpm


Technical Data Control Fluid System & Control Fluid Pumps

CONTROL FLUID SYSTEM A Fire Resistant Fluid (FRF) is used for the control system 3

Control fluid tank, rated capacity

10/16

M

First fill quantity (estimated)

15

M

Flushing fluid quantity (estimated)

12

M

Control fluid cooler for operation

1

No.

Control fluid cooler for reserve

1

No.

3

3

Control fluid regeneration system Gear pump

Make: Tushaco

Fluid flow

0.25

dm /s

Gauge pressure

3

bar

speed

23.42

rpm

Motor power

0.55

KW

Control fluid purification system

Make: M/s Hilliard corporation, Type:82119550973001

1 No. Drying filter 2 Nos. Fuller’s earth filter 1 No. Fine filter

BHEL, HARIDWAR

3

5.1-0104-63-1 5.1-0104-63-1

Control Fluid Pumps Control fluid pumps

2

Nos.

Manufacturer

KSB, Type: WKVM80/1+3

Speed

2982

Drive

A.C. motor, Manufacturer – Siemens AG Type: ILG4313-2AB94-Z

Enclosure

IP 55

Voltage

415

V

Frequency

50

Hz

Motor rating (at 50ºC)

132

KW

Motor rating (at 40ºC)

148

KW

Rated current

217

A

Starting current

1614

A

rpm

Fluid flow 3 (dm /s)

Discharge Pressure (bar)

Low pressure leakage fluid

7.6

11.5

High pressure leakage fluid

6.16

38.5

Control fluid pumps operating characteristics

Operating point I (normal operation)

Operating point II (during start & opening of stop valve servomotors) Low pressure leakage fluid & low pressure control fluid

20.60

10.8

High pressure leakage fluid

6.16

37.8

Low pressure leakage fluid

7.60

10.6

High pressure leakage fluid & high pressure control fluid

16.16

31.6

Operating point III (during opening of CV servomotors)

All pressures are gauge pressures.

5.1-0104-63-2

Steam Turbine Operation

Technical Data

Limit Curves

Permissible temperature difference ∆θ in the wall of HP stop and control valve casing during Sliding Pressure Operation Mode 140 14 0 ∆θ = f (θm )

120 12 0 Heating up

100 10 0 F 80 N

60

S

40 OPERATION MODE F=Fast N=Normal S=Slow

∆θ[K]

20 0 -20 -2 0 -40 -4 0

Cooling down

-60 -6 0 -80 -8 0 100 10 0

0

200 20 0

300 30 0

40 0

500 50 0

600 60 0 θm [° [°C]

BHEL Haridwar

∆θ

=

(θi - θm) on the wall temperature sensor

θi

=

temperature of inner layer

θm

=

temperature of middle layer

5.1-0110-01


Technical Data

Limit Curves

Permissible temperature difference ∆θ in the wall of HP casing during Sliding Pressure Operation Mode 140 ∆θ = f( θm)

120 Heating up

100 80

F

60 N 40 OPERATION MODE F=Fast N=Normal S=Slow

∆θ[K]

20

S

0 -20 -40 Cooling down

-60 -80 100

0

200

300

400

500

600

θm [° [°C] ∆θ = θi

=

θm =

BHEL Haridwar

(θi - θm) on the wall temperature sensor temperature of inner layer temperature of middle layer

5.1-0111-01/1

Permissible temperature difference ∆θ in the wall of the HP casing during Constant Pressure Operation Mode

140 14 0 ∆θ = f (θm )

120 12 0 100 10 0

Heating up

80

F

60

N

40

S

OPERATION MODE F=Fast N=Normal S=Slow

20 ∆θ[K]

0 -20 -2 0 -40 -4 0 Cooling down

-60 -6 0 -80 -8 0 0

100 10 0

200

3 00

400 40 0

500 θm [° [°C]

5.1-0111-01/2

∆θ

=

(θi - θm) on the wall temperature sensor

θi

=

temperature of inner layer

θm

=

temperature of middle layer

60 0


Technical Data

Limit Curves

Permissible temperature difference ∆θ in the HP turbine shaft during Sliding Pressure Operation Mode 200 180

∆θ

160

= f (θ ) m

Heating up

140 120

F

100 ∆θ[K]

80

N

60

S

40

OPERATION MODE F = Fast N = Normal S = Slow

20 0 -20 -40

Cooling down

-60 -80 0

100

200

300

40 0

500

600

θm [°C]

220 200 180 160 ∆θ[K]

140 120 100 80 60 0

∆θ θo θm θax

BHEL Haridwar

= = = =

20

40

60

80

100

120

θax [° C]

(θo - θm) on the wall temperature sensor outer layer temperature of the shaft temperature of middle layer in the shaft (calculated) temperature of axis in the shaft (calculated)

5.1-0112-01/1

Permissible temperature difference ∆θ in the HP turbine shaft during Constant Pressure Operation Mode 180 160

∆θ =

140

f (θ ) m

Heating up

120 100

F

80 ∆θ[K]

60

N

40

S

20


0 -20 -40 -60

Cooling down

-80 -100 0

100

200

300

400

500

600

θm [°C]

200 180 160 140 120 ∆θ[K]

100 80 60 40 0 ∆θ θo θm θax

5.1-0112-01/2

= = = =

20

40

60

80

100

120

θax [° C]

(θo - θm) on the wall temperature sensor outer layer temperature of the shaft temperature of middle layer in the shaft (calculated) temperature of axis in the shaft (calculated)


Technical Data

Limit Curves

Permissible temperature difference ∆θ in the IP turbine shaft during Sliding Pressure Operation Mode 200 180

∆θ =

160

f (θ ) m

Heating up

140 120

F

100 N

80

∆θ[K]

60

S

40


20 0 -20 -40

Cooling down

-60 -80 0

100

200

300

400

500

θm [°C]

600

0 0 0 0 0

∆θ[K]

0 0 0 0 0

∆θ θo θm θax

BHEL Haridwar

= = = =

20

40

60

80

10 0

12 0

θax [°C]

(θo - θm) on the wall temperature sensor outer layer temperature of the shaft temperature of middle layer in the shaft (calculated) temperature of axis in the shaft (calculated) 5.1-0113-01

Steam Turbine Description The deposits which occur in turbines due to impurities in the steam can lead to thermodynamic and mechanical inefficiencies and, with the presence of salts, especially chlorides, and sodium hydroxide also cause damage to turbine parts. The corrosion stressing caused by active deposits, for example, has an adverse effect on the fatigue strength of the blade material when the steam is in the transition zone between the superheated and the saturated state. Compliance with the target values is mandatory in continuous operation, with the values in the normal operation column preferable. With the commissioning of a new plant and starting-up operation, however, these values cannot be attained with an economical outlay. The values listed in the column “starting-up operation “are then valid. It should be pointed out that adherence to the target values does not rule out deposition in the turbine with absolute certainty. Wherever possible every effort should be made to

Steam Purity values for main steam condensate achieve the values in the normal operation column. A recording instrument may be used to continuously monitor the electrical conductivity of the main steam and turbine condensate following a strongly acid cation exchange unit. In order to determine slight impurities, the sodium concentration should be measured in addition to this. Should saline contamination occur, the turbine is to be immediately washed with saturated steam to remove salt deposits. Whether an alkaline, neutral or combined method is used for conditioning, the water steam circulation is for the customer to decide. If an alkaline method is used, the oxygen content in the main steam condensate can be max. 0.02 mg/kg and the pH value in the turbine condensate max.9.3 with brass condenser piping. When the condenser piping is of copper-nickel alloys, the pH value must not exceed 9.5. There is no limitation for the pH value with noncorroding steel or titanium.

Recommended values for main steam condensate Quantity

Target Value *

Normal Operation

Start Up **

Conductivit Conduc tivity y at 25°C, down stream st ream of highly hi ghly acidic sampling cation exchanger, continuous measurement at sampling point

µS/cm

< 0.2

0.1

< 0.50

Silica

(SiO2)

mg/kg

< 0.020

0.005

< 0.050

Total iron

(Fe)

mg/kg

< 0.020

0.005

< 0.050

Total copper

(Cu)

mg/kg

< 0.003

0.001

< 0.010

Sodium

(Na)

mg/kg

< 0.010

0.002

< 0.020

* To avoid any drop in efficiency, it is recommended that values be kept below the target values and into the range of the values for normal operation. ** The target values must show a noticeable downward trend. On initial start-up of new plants the values given for normal operation must be achieved within 2 to 3 days and within 2 to 3 hours for other start-ups.

BHEL Haridwar

5.1-0120-01


Oil Specification Specification Standard

Introduction

Compatibility

This standard specifies the turbine oil recommended for use in governing and lubrication systems of BHEL make steam turboset.

For topping up of the oil system, it is preferable if the oil used is of the same brand and quality as that already in the system. However, if the same brand of oil is not available and where it is intended to mix in different products that individually conform to this standard, a compatibility test should be conducted before actually mixing the oils. Samples of both the oils in equal volume should be mixed and centrifuged for about 40 hrs. and then mixture must comply fully with the requirements of this standard.

Description Oil of viscosity class ISO VG 46 shall be used. The oil shall be a petroleum product with or without additives to meet the requirement of this standard. The finished oil shall be clear and free from water, suspended matter, dust, sediment and other impurities. The turbine oil shall not contain additives having any negative effect on the materials of the oil system. The turbine oil must be capable of withstanding bearing temperature of max. max . 130°C and oil tank t ank tem perature peratu re of max. 80°C without with out physical ph ysical and an d chemical chem ical degradation. The properties of the oil shall not be affected by centrifuging, water washing or filtering.

Properties The oil should comply with the requirements given in table below when tested according to the test methods given in the respective standards mentioned against each property. For obvious reasons, we do not give any special recommendation to a particular brand of oil to be used in the oil system of our turbo sets. Any brand of the oil complying with the above standards may be used.

Properties of turbine oil ISO VG 46 shall be as follows: Sl. No.

Properties

Value

Unit

1.

Kinematic Viscosity at 40ºC Kinematic Viscosity at 50ºC

41.4 – 50.6

cst

28

cst

2.

Viscosity Index

98

Min.

3.

Neutralization No. acidity)

4. 5.

mg KOH/g

IS: 1448, P-25

ASTM D445

IS: 1448, P-56

-----

IS: 1448, P-1

ASTM D974

≤

0.20

Colour

≤

2

Max.

IS: 1448, P-12

ASTM D1500

Specific gravity at 50 ºC Specific gravity at 15 ºC

0.85

---

IS: 1448, P-32

ASTM D1298

0.90

---

6.

Flash point (Cleveland open cup)

> 200

°C

IS: 1448, P-69

ASTM D92

7.

Copper strip corrosion test at Not worse than No.1 100 ºC for 3 hrs.

---

IS: 1448, P-15

-----

8.

Pour point

≤

-6

°C

IS: 1448, P-10

ASTM AST M D97

9.

Rust preventing characteristics

≤

0-B

---

DIN: 51585

ASTM D665

BHEL Haridwar

(Total

Test Method

5.1-0130-04/1

Properties contd.

Sl. No.

Properties

Value

Unit

Test Method

10.

Emulsion characteristics

≤

20

minute

DIN: 51599

ASTM D1401

11.

Total acidity after 2500 hrs oxidation

≤

0.2

mg KOH/g

DIN: 51587

ASTM D943

12.

Foaming characteristics at 25°C - Foaming tendency

-----

ASTM: D892

minutes

DIN: 51381

ASTM: D3427

- Foaming stability

≤ 400 ≤ 450

cm s

3

s

13.

Deaeration Deaerat ion capacity capaci ty at 50°C

≤

4

14.

Ash (by weight)

≤

0.01

%

IS:1448, P-4

-----

15.

Water content by weight

≤

0.01

%

DIN: 51777-1

ASTM: D1744

16.

Solid particles by weight

≤

0.05

%

DIN: 51592

-----

17.

Particle distribution

-/17/14

Minimum

ISO: 4406

(Class-8)

18.

Water release

≤

(NAS: 1638)

300

s

DIN: 51589-1

Following brands of oil are acceptable Supplier

Brand

Supplier

Brand

lOC

Servo Prime 46

Castrol lndia Ltd.

Castrol Perfecto T-46-Superclean

Gulf Oil India Ltd

Gulf Crest 46

Bharat Petroleum

Turbol 46

Apar Ltd.

Power Turbo-46

Indo Mobil Ltd.

Mobil DTE Medium / DTE798

Caltex

Regal R&O 46

Savita Chemicals

Daphne Super Turbine oil 46

HPCL

Turbinol 46

Bharat Shell Ltd.

Shell Turbo oil T46

TOTALFINAELF

Total Preslia 46

Also refer to the following sections:

[1] 5.3-0080: Turbine oil Care

5.1-0130-04/2

Steam Turbine Description This specification is valid for Fire Resistant Fluids (FRF) recommended for BHEL make steam turbine control system. According to ISO 6743/4, FRF is a fluid based on triarylphosphate ester marked ISO-L-HFDR. General Requirements

Fire Resistant Fluid (FRF) for Turbine Control System should be no deterioration of the FRF in presence of such trace quantities. The air release of the FRF should not deteriorate in presence of fluoroelastomer seals and packing used in the FRF system. The FRF must be free of ortho-cresol compounds.

The FRF shall not cause corrosion to Steel, Copper and its alloys, Zinc, Tin or Aluminum.

The FRF must not pose a safety or health hazard to the persons working with it, provided that the requisite hygiene regulations are observed.

The FRF must provide sufficient corrosion protection to the materials used in the FRF system.

Limit values

The FRF shall be continuously regenerated with Fuller’s earth or an equivalent regeneration agent. Note :

Before using regeneration agents other than Fuller’s earth (e.g. ion exchangers) BHEL and FRF manufacturer or supplier shall be contacted.

The FRF must not cause any erosion or corrosion on the edges of the control elements. The FRF must be shear-stable. It should not contain any viscosity index improver. FRF leaking from the system, if any, must not ignite or burn in contact with hot surfaces (up to 550 ºC). The FRF must be capable of withstanding continuous contin uous operating oper ating temper t emperatures atures of 75 °C without physical or chemical degradation. The FRF must be miscible with traces (max. 3 % by vol.) of TXP of another brand. There

BHEL Haridwar

The following limit values are not to be exceeded during the life time : Kinematic viscosity - maximum variation ± 5% with reference to delivery condition. Neutralisation number - maximum increase 0.20 mg KOH/g with reference to delivery condition. Air release -maximum 12 minutes. Foaming Foami ng at 25 °C -Tendency -Te ndency maximum m aximum 200 ml, Stability maximum 450 sec.

Disposal Supplier to be contacted for ‘Buy ‘Buy Back ’ of used fire resistant fluid. In consultation with supplier, liquid material should be incinerated and material absorbed on sand should be disposed off as hazardous solid waste.

5.1-0140-04/1

Recommended Properties of new batches of FRF

Property

Numerical Value

Unit 2

Test method DIN / ISO

ASTM

Kinematic Kinem atic Viscosity Viscos ity at a t 40 °C (ISO VG 46)

41.4 - 50.6

mm /s

DIN 51 562-1

D 445

Air release rel ease at 50 5 0 °C

≤ 3

minutes

DIN 51 381

D 3427

Neutralisation number

≤ 0.1

mg KOH/g

DIN 51 558-1

D 974

Water content

≤ 1000

mg/kg

DIN 51 777-3

Tendency

≤ 100

ml

Stability

≤ 450

sec

Water separability

≤ 300

sec

DIN 51 589-1

Demulsification

≤ 20

minutes

DIN 51 599

D 1401

Densit Dens ity y at 15 °C

≤ 1250

kg/m

DIN 51 757

D 1298

Flash point (Cleveland open cup)

> 235

°C

DIN/IS DIN /ISO O 259 2592 2

D 92

Ignition temperature

> 550

°C

DIN DI N 51 794 79 4

Wick flame persistance time

≤ 5

sec

DIN/ISO 14935

Pour point

≤ −18

°C

DIN/IS DIN /ISO O 301 3016 6

Particle distribution *

≤ 15/12

Code

ISO 4406

Chlorine content

≤ 50

mg/kg

DIN 51 577-3

Oxidation stability

≤ 2.0

mg KOH/g

DIN 51 373

≤ 2.0

mg KOH/g

DIN 51 348

> 50

MΩm

IEC 247

Foam ing at 25 2 5 °C

Hydrolytic stability

D 892 (Seq. 1)

3

D 97

Change of neutralisation number Electrical resistivity

* The required system cleanliness is dependent upon the system design. Suitable measures (e.g. filtration, separation) have to be taken to achieve this cleanliness level.

Following fire Resistant Fluids are approved:

Brand

Supplier

1.

Reolube Turbofluid 46XC

M/s. Chemtura, UK

2.

Fyrquel EHC-N

M/s. Supresta, USA

Also refer to the following sections:

[1] 5.3-0082 : Care of control fluid

5.1-0140-04/2


HP Turbine Valve Arrangement

General Arrangement The HP turbine has 2 main stop valves and 2 control valves located symmetrically to the right and left of the casing. The valves are arranged in pairs with one main stop valve and one control valve in a common body.

Steam flow The main steam is admitted through the main steam inlet passing first the main stop valves and then the control valves. From the control valves the steam passes to the turbine casing(1).

BHEL Haridwar

The short length of the admission between the control valves and the results in a very low steam volume section, which has a beneficial effect shutdown characteristics of the generator unit.

section casing in this on the turbine-

Valve Actuation Each main stop valve and control valve has a dedicated hydraulic servomotor(3;5). The servomotors are mounted above floor level so that they are accessible and and can be easily easily maintained.

5.1-0205-00


Barrel type Casing The HP outer casing is designed as a barreltype casing without axial joint. An axially split inner casing (4) is arranged in the barrel-type casing(3) Because of its symmetrical construction, the barrel - type casing retains its cylindrical shape and remains leakproof during quick changes in temperature (e.g. on start-up and shut down, on load changes and under high pressures). The inner casing too is almost cylindrical in shape as the joint flanges

HP Turbine Casing

are relieved by the high pressure acting from the outside and can thus be kept small. For this reason, turbines with barrel type casing are especially suitable for quick start-up and loading.

Seals The pretensioned U-shaped seal ring(12), that is forced against the axial sealing surfaces by the steam pressure and the I shaped seal ring (16), that allows axial displacement of the inner casing (4), seal the space between the inner casing (4) and the barrel type outer casing (3) from the adjacent spaces.

Fig. 1 HP Turbine BHEL Haridwar

5.1-0210-01/1

Fig.2 Inlet Connection 3 4 6 7 8 9

Outer casing Inner casing U seal ring Cylindrical pin Breech nut Inlet pipe from main main stop and control valve

Connection to Main Stop and Control Valves V alves The steam lines from the main stop and control

3 Outer casing 4 Inner casing 11 Fitted Key

Fig. 3 Centering and support of Inne Innerr ca casi sin n Admis dmissi sion on side side 5.1-0210-01/2

valves are connected to the inlet connections of the outer casing by Breech Nuts(8) (Fig.2) through buttress threading. Sealing is achieved by U-seal rings(6) which is forced against the outer sealing surface by inlet steam pressure. The annular space around the sealing ring is connected to the condenser through a steam leak-off line. Cylindrical pins(7) located at the joint f lange prevent rotation of the inlet pipe with respect to the outer casing.

3 Outer casing 4 Inner casing 10 Fitted Key Fig. 4 Centering and support of Fig. 4 Centering and support inner casing (Exhaust side)

of

Attachment Attachment of Inner Casing The inner casing (4) is attached in the horizontal and vertical planes in the barrel-type casing(3) so that it can freely expand radially in all directions and axially from a fixed point when heating up while maintaining concentricity relative to the turbine rotor. On the admission side, four projections of the inner casing (4) and on the exhaust side three projections fit into corresponding grooves in the barrel-type casing (3). In the horizontal plane these projections rest on fitted keys (10) and in the vertical plane they are guided by the fitted keys (11) (Fig.3&4). Radial expansion is therefore not restricted by this suspension. As shown in fig.6 the axial fixed point of the inner casing is provided by a shoulder in the barrel-type casing (3) against which a collar of the inner casing(4) rests. The axial thrust to which the inner casing is subjected is transmitted to and absorbed by the thrust ring (14) via thrust pads(13). The thrust thrust ring is held in position by support ring (15).

Outlet Connections Connections The exhaust end of HPT has single outlet connection from bottom. At the flange connection a U-seal ring (19) is provided to prevent any leakage (Fig.1)

3 Outer casing 4 Inner casing 12 U- seal ring

3 4 16 17 18

Outer casing Inner casing I-seal ring Holding ring Hexagon head screw

Fig. 5 I-Ring seal (Detail A from Fig. 1)

13 Thrust pads 14 Thrust pads 15 Support ring

Fig. 6 Axial Retention ofInner casing and Centering in vertical plane (Detail E from Fig.1)

5.1-0210-01/3

HP Turbine Blading

Steam Turbine Description Moving and Stationary Blades The HP turbine with advance blading consists of 17drum stages. All stages are reaction stages with 50% reaction. The stationary and moving blades of all stages (Fig.1) are provided with inverted T-roots which

1

A

2 3

.

B 4

5

The moving and stationary blades are inserted into corresponding grooves in the shaft( 4) and inner casing (1) and are caulked at bottom with caulking piece (5) .The insertion slot in the shaft is closed by a locking blade which is fixed by taper pins or grub screws. End blades are used at the joint plane in L/H & U/H of inner casing along with predetermined interference.

Gap sealing Fig. 1 Drum Stages

1 Inner casing 2 Guide blade 3 Moving blade

4 Turbine shaft 5 Caulking piece

also determine the distance between the blades. The shrouds are machined integral with the blades and forms a continuous shrouding after insertion. st th From 1 . to 8 . stages are provided with ‘3DS’ th th blades, 9 . to 13 . stages with ‘TX’ blades and th 14 . to 17 th. stages with ‘F’ blades.

BHEL Haridwar

Sealing strips(6) are caulked into the inner casing(1) and the shaft (4) to reduce leakage losses at the blade tips. Cylindrically machined surface on the blade shrouds are opposite the sealing strips. The surfaces have stepped diameters in order to increase the turbulence of the steam and thus the sealing effect. Should an operational disturbance cause the sealing strips to come into contact with opposite surfaces, they are rubbed away without any considerable amount of heat being generated. They can easily be renewed at a later date to provide the specified clearance.

5.1-0220-02


Function

HP Turbine Shaft seals and Balance Piston

diameter is suited to the requirements for balancing the axial thrust.

The function of shaft seals is to seal the interior of the casing from the atmosphere at the ends of the shaft on the admission and exhaust sides.The HP Turbine has shaft seals in front and rear. The front shaft seal is of labyrinth type, while the rear shaft seal is of ‘see through’ type. The difference in pressure before and after the raised part of the shaft seal on the admission side serves to counteract the axial thrust caused by steam forces.The raised part is called Balance piston. The effective seal

Sealing between the rotating and stationary parts of the turbine is achieved by means of seal strip(6) caulked into seal rings (2,7,9) and into the rotor (3) (details D and E). The pressure gradient across the seal is reduced by conversion of pressure energy into velocity energy which is then dissipated as turbulence as the steam passes through the numerous compartments according to the labyrinth principles.

Fig. 1 Shaft Seal Admission side

Seal Rings

1 3 4 5 6

Inner casing 2 Seal ring Turbine rotor Shaft seal cover Caulking wire Seal strip

Gap Seals

The seal rings (2), the number of which depends on the pressure gradient to be sealed are divided into several segments as shown in Section A-A, B-B and C-C and mounted in T -shaped annular grooves in the inner casing (1 ) and shaft seal cover (4) such that they are free to move radially. Each segment is held in position against a shoulder by helical springs (11). This provides the proper clearance for the seal gaps. Should rubbing occur, the segment concerned can retreat. The heat developed by light rubbing of the thin seal strip (6)

Fig. 2 Shaft seal Exhaust side BHEL Haridwar

5.1-0230-01/1

is so slight that it cannot cause deformation of the rotor (3). When the turbine is started from the cold or warm state, the seal rings naturally heat up faster than the casing. However, they can expand freely In the radial direction d irection against the centering force of the helical spring spri ng (11). The shaft seals are axial-steam flow noncontacting seals. In the region subjected to the low relative expansion in the vicinity of the combined journal and thrust bearing, the seal strips are caulked alternately into the shaft and into spring-supported segmented sealrings in the casing, forming a labyrinth to impede the outflow of steam (Detail D). In the region subject to greater relative

5.1-0230-01/2

expansion at the exhaust end, see through seals are used in which the seal strips are located opposite each other, caulked into the shaft and into seal rings centered in the outer casing (Detail E). The outer seal rings can be removed for inspection and if necessary, seal strips can be replaced during short turbine shut down.

Steam Spaces Steam spaces are provided within the shaft seals. From spaces ‘Q’ and ‘R’ leakage is drawn off to another part of the turbine for further use. The steam seal header is connected to space ’S’. The slight amount of leakage steam which are still able to pass the seal ring are conducted from the space ‘T’ into the seal steam condenser.

Steam Turbine Description Arrangement The front bearing pedestal is located at the turbineside end of the turbine generator unit. Its function is to support the turbine casing and bear the turbine rotor. It houses the following components and instruments.

HP Turbine Front Bearing Pedestal Connection Foundation

of

Bearing

Pedestal

and

Journal bearing [1] Hydraulic turning gear [2] Main oil pump with hydraulic speed  transducer [3]  Electric speed transducer [4] Overspeed trip [5]  Shaft vibration pick-up  Bearing pedestal vibration pick-up  Details of casing supports and casing guides are given in description 5.1-0280.

The bearing pedestal (1) is aligned to the foundation by means of hexagon head screws that are screwed into it at several points. On completion of alignment, the space beneath the bearing pedestal is filled with special non-shrinking grout. The bearing pedestal is anchored to the foundation by means of anchor bolts (13). The anchor bolt holes are filled with gravel, which gives a considerable vibration damping effect. The defined position of the bearing pedestal on the foundation is established by a projection in the middle of the bearing pedestal base engaging in a recess in the Foundation. On completion of alignment, the remaining space in this recess is likewise filled with grout .

1 Bearing pedestal 2 Main oil pump 3 Hydraulic speed transducer 4 Electric speed transducer 5 Gear coupling 6 Over speed trip

7 Hydraulic 7 Hydraulic turning turning gear gear 8 Bearing 8 Bearing pedestal pedestal vibration vibration pick-up pick-up 9 Shaft 9 Shaft vibration vibration pick-up pick-up 1010 Journal Journal bearing bearing 11 11 HPHP turbine turbine rotor rotor 1212 Foundation Foundation

 

Fig.1 Axial Section through HP Turbine Front Bearing Pedestal BHEL Haridwar

5.1-0240-01/1

Fig. 2 Cross section of main oil pump

Fig. 3 Cross Section of Journal Bearing

10 Journal bearing Also refer to the following information i nformation 12 Foundation 13 Anchor bolts 14 Hex head screw

5.1-0240-01/2

[4] 5.1-0760 Electric Speed Transducer Also refer to the following information i nformation [1] 5.1-0270 Journal Bearing [2] 5.1-0510 Hydraulic Hydraulic Turning Gear [3] 5.1-1020 Main Oil Pump with Hydraulic Speed [1] 5.1-0270 Transducer Journal Bearing [4] [2]5.1-0760 5.1-0510Electric Hydraulic Speed Turning Transducer Gear [5] [3]5.1-0920 5.1-1020Overspeed MainOilPump trip with Hydraulic Speed Transducer [5] 5.1-0920 Overspeed trip

Staem Turbine Description

HP Turbine Rear bearing Pedestal

Arrangement The bearing pedestal is located between the HP and IP turbines. Its function is to support the turbine casing and bear the HP and IP turbine rotors. The bearing pedestal houses the following turbine components: Combined journal and thrust bearing Shaft vibration pick-up  Bearing pedestal vibration pick-up  Thrust bearing trip (electrical)  Details of casing supports and casing guides are given in descriptions 5.1-0280 and 5.1-0350. 

Connection Foundation

of

Bearing

Pedestal

and

The bearing pedestal is aligned on the foundation by means of hexagon head screws that are screwed into it. On completion of alignment, the space beneath the bearing pedestal is filled-in with special non-shrinking grout. The bearing pedestal is anchored to the foundation by means of anchor bolts. The anchor bolt holes are filled with gravel, which gives a considerable vibration damping effect. The defined position of the bearing pedestal on the foundation is established by a projection in the middle of the bearing pedestal base engaging a recess in the foundation. On completion of alignment, the remaining space in the recess is likewise filled with grout.

1 2 3 4 5 6 7 8

HP turbine rotor Combined journal and thrust bearing Bearing pedestal vibration pick-up Shaft vibration pick-up Thrust bearing trip (electrical) Coupling bolts IP turbine rotor Foundation

Fig. 1 Axial Section through the HP Turbine Rear Bearing pedestal

BHEL Haridwar

5.1-0250-02/1

8

9

2 Combined journal and thrust bearing 8 Foundation 9 Hex head screw Fig. 2 Cross Section through Combined Journal and Thrust Bearing

10 11 12 13 14 15

8

Straight pin Anchor bolt Plate Round nut Hex nut Guard cap

Fig. 3 Connection between Bearing Pedestal and foundation

5.1-0250-02/2


Combined Bearing

Function The function of the combined journal and thrust bearing is to support the turbine rotor and to take the residual axial thrust. The magnitude and direction of axial thrust to be carried by the bearing depends on the load conditions of the turbine. This bearing is located in the bearing pedestal between HPT & IPT. The thrust bearing maintains desired axial clearances for the combined turbine generator shaft system.

Construction and Mode of Operation The combined journal and thrust bearing consists of the upper and lower bearing shells (4, 12), thrust pads (6), cap (2), spherical blocks (14, 16) and keys (10, 17). The upper and lower halves (4, 12) of the bearing shell are bolted and doweled at the horizontal joint by means of 4 taper pins and 4 stocket-head screws. Section A-A

1 Bearing pedestal, upper 7 Bearing liner 2 Cap 3 4 5 6

Key Bearing shell upper Cowling with all baffle Thrust pad

BHEL Haridwar

8 Turbine shaft 9 Brg. pedestal lower 10 Key 11 Oil line

Journal

and

Thrust

The journal bearing is constructed as elliptical sleeve bearing. The bearing liners are provided with a machined babbit face; additional scraping is neither necessary nor allowable. In order to prevent the bearing from exerting a bending moment on the shaft, it is pivotmounted on spherical support (16). The spherical block (14) with shims (13,15), is bolted to the lower bearing shell (12). A transverse projection in the upper part of the cap (2) and the fitted key (3) prevent the bearing shells from rising. The bearing shells are located laterally by keys (10). The bearing is supported axillay against the bearing pedestal (1,9) by means of keys (17, 18) (Section H-H). This fixing is of great importance for axial clearance in the whole turbine. Located at each end of the bearing shell, babbitted thrust pads (6) form two annular surfaces on which the integralily machined shaft collars run. Section B-B

12 Bearing shell,lower 13 Shim 14 Spherical block 15 Shim 16 Spherical support 25 Key “a” Shaft jacking oil

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These collars and thrust pads permit equal loading of the thrust bearing in either direction. As shown in section N-N, the thrust pads are of the tilting type, secured in place by pins (23) and flexible mounted on split spring element (21). Temperature Measurement Metal temperature of the journal bearing and thrust pads is monitored by the thermocouples (19,20) (Section E-E and G-G).

19 Thermocouple 20 Thermocouple Oil Supply Lubricating oil is admitted to the bearing shells from one side via oil line (11) from where it flows to the oil spaces milled into the upper and lower bearing shells at the horizontal joint.

Oil leaving the journal bearing flows to the two annular grooves adjacent to the bearing surface and then to the thrust pads (6). Through the two oil return cowlings (5), oil is discharged into the drain area in the pedestal (9) JackingOil Passages are located at the lowest point in the lower bearing shell through which high pressure jacking oil is supplied under the journal at low speed of the turbine rotor (on start up or shutdown). Thus dry friction is prevented and the breakaway torque on start-up with turning gear is reduced. High pressure oil “a” flows under the journals

4 Bearing shell upper element 6 Thrust pad 12 Bearing shell, lower

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21 Spring 22 Key 23 Dowel pin

via the oil line and via openings in the lower bearing shell (12). O-ring (24) located between the bearing liner (7) and the lower bearing shell (12) prevents any oil from penetrating between the two elements (Detail “C”). Any leakage passing the seal will drain off to the bearing pedestal through a groove in the lower bearing shell. This arrangement ensures that no oil penetrates between the bearing liner and the bearing shell.

Steam Turbine Description Construction The function of the journal bearing is to support the turbine rotor. Essentially the journal bearing consists of the upper and lower shells (3,6), bearing cap (1), spherical block (7), spherical support (14) and the key (11) .The bearing shells are provided with a babbit face. The babbit surface of the bearing is precision machined and additional scraping is neither necessary nor permissible. Both bearing shells are fixed by means of taper pins and bolted together. In order to prevent the bearing from exerting a bending moment on the rotor (5), it is pivotmounted in the spherical support (14). For this purpose the spherical block (7) with shims (12,13) is bolted to the bearing shell (6) . A projection in cap (1) with shims (9) fits into a

Journal Bearing HP front bearing shells. Keys (8) are fitted on both sides of the projection. The bearing shells are fixed laterally by key (11) which are bolted to each other. Each key is held in position in the bearing pedestal (10) by two lateral collars. The temperature of the bearing bodies is monitored by thermocouples (19) as shown in section c-c. Oil Supply Lubricating oil is admitted to the bearing shells from one side and flows to oil spaces that are milled into the upper shell at the horizontal joint and are open to the rotor. The rotor (5) picks up oil from oil pocket machined into the babbitting .The oil emerges from the bearing shell where it is collected in the oil return cowling (4) and drained into the bearing pedestal(10).

corresponding groove in the bearing shell (3) and prevents vertical movement of the

1 2 3 4 5

Cap 6 Lower baering shell Tab Washer 7 Spherical block Upper bearing shell 8 Key Oil return Cowling 9 Shim Turbine Rotor 10 Bearing pedestal

BHEL Haridwar

11 12 13 14

Key Shim Shim Spherical support

15

Shim

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Jacking oil As shown in Detail B, a threaded nozzle( 17) is arranged at the lowest point of the lower bearing shell (6) through which high pressure lift oil is supplied to the space below the journals when the rotor is turning at low speed (on startup and shutdown).This high pressure oil floats the shaft to prevent dry friction and overcome breakway torque during start-up on the hydraulic turning gear. A seal (18) prevent high pressure oil from penetrating the space between threaded nozzle and ring (16) and thus from lifting the babbit. Any leakage oil can drain through passages in the bearing shell below the ring.

Removal of Bearing Shells Not only the upper shell(3) but also the lower bearing shell(6) can be removed without the removal of rotor (5). To enable this to be done the shaft is lifted slightly by means of jacking device but within the clearance of the shaft seals. The lower bearing shell can then be turned upwards to the top position and a nd removed.

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16 Ring 17 Threaded nozzle 18 Sealing ring 19 Thermocouple

Steam Turbine Description Supports The turbine casing is supported on the support horns such as to make allowance for the thermal expansion. It is essential for the casing to retain concentric alignment with the rotor, which is supported independently.

1 2 3

HP Turbine Casing Supports and Guides The turbine casing (2) is supported with its two front and two rear support horns on the horn supports of the bearing pedestal (1,3) at the turbine centerline level. This arrangement determines the height of the casing and also allows thermal expansion to take place in the horizontal plane by the support horns

Front bearing pedestal HP turbine Rear bearing pedestal

Fig.1 Connection between Turbine Casing and Bearing Pedestals BHEL Haridwar

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sliding on the sliding pieces (6) of the bearing pedestals (1 ;3). To prevent lift-off of the turbine casing (2), holders (4) hold down projections of the support horns which engage in mating recesses in the bearing pedestal. When the turbine is being erected, a clearance ’s’ is maintained between the thrust bar(5) and the turbine casing support horn projection. Guides

to the turbine centerline is provided by the guides shown in section B-B and E-E. These guides allow the turbine casing to expand freely.

Fixed Point The fixed point for the turbine casing (2) is located at the horn support on HP-IP pedestal at the turbine centerline level and is formed by the parrallel keys (16). Axial expansion of the turbine casing (2) originates from this point.

The central location of the turbine casing at right angle

1 Front bearing pedestal 2 HP turbine 4 Holder 5 thrust bar 6 sliding piece 7 Plate 8 parallel key 9 plate

10 11 12 13 14 15 16

Sliding piece Plate Parallel key Scale indicating indicating casing expansion Sliding piece Plate Parallel key

Fig. 2 Details of Casing Supports and guides

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Steam Turbine Description Double Shell Construction The casing of the IP turbine is split horizontally and is of double shell construction. A double-flow inner casing (3,4) is supported in the outer casing (2,5) (Fig.1) Steam from the HP turbine after reheating enters the inner casing from top and bottom through two admission branches which are integral with the mid section of the outer casing. This arrangement provides opposed double flow in the two blade sections and compensates axial thrust. The centre flow prevents the steam inlet temperature from affecting the support horns and bearing sections.

IP Turbine Casing The provision of an inner casing confines the steam inlet conditions to the admission section of this casing. While the joint flange of the outer casing is subjected only to the lower pressure and temprature effective at the exhaust from the inner casing. This means that the joint flange can be kept small and material concentrations in the area of the flange reduced to a minimum. In this way, difficulties arising from deformation of a casing with flange joint due to non uniform temperature rise e.g. on start-up and shut down, are avoided. avoided. The joint of the inner casing is relieved by the pressure in the outer casing so that this joint has to be sealed only against the resulting differential pressure.

.

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Steam Inlet and Extraction Connection The angle ring (9) are provided at the connection of admission and extraction branches with the inner casing (3,4) (Detail ‘D’ Fig. 2 & 3). 3). One leg of the angle ring (9) at such a connection bears against the back of the collar of the threaded ring (7) in the outer casing while the other fits into an annular groove in the inner casing. The threaded ring (7) is fitted in such a way that the short leg of the angle ring can slide freely between the collar of the threaded ring and the outer casing. The steam pressure prevailing on the inside, forces the angle ring against the face of the outer casing. . The tolerances of the annular grooves in the inner casing are dimensioned to allow the long legs of the angle ring (9) to slide in the groove. The angle rings are flexibly expanded by the pressure on the inside and their outer areas forced against the annular grooves to provide the desired sealing effect

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While providing a tight seal, this arrangement permits the inner casing to move freely in all directions. Attachment of Inner Casing Due to the different temperatures of the inner casing relative to the outer casing, the inner casing is attached to the outer casing in such a manner as to be free to expand axially from a fixed point and radially in all directions, while maintaining the concentricity of the inner casing relative to the shaft. The steam admission connections and the extraction connections are designed to avoid any restrictions due to thermal expansion. The inner casing is attached to the outer casing in the horizontal and vertical plane.

In the horizontal plane, as shown in details E and F (Fig. 4 & 5) the four support horns of the top half inner casing (3) rest on plates (13) which are supported by the joint surface of the bottom half outer casing (5). The shoulder screws (12) are provided with sufficient clearance to permit the inner casing to expand freely in all directions in the horizontal plane. Thermal expansion in the vertical direction originates from the point of support at the joint. This ensures concentricity of the inner casing relative to the rotor (1) in this plane. plane. The support horns provided at the bottom half inner casing (4), project into the recesses in bottom half outer casing (5) with clearance on all sides. Located on top of each support horn is a spacer disc (11) whose upper surface has a clearance ’s’ to the flange face of the top half outer casing (2). This clearance thus determines the lift of the inner c asing. As shown in details E, the inner casing is located axially by the fitted keys (10) arranged on both sides of the support horns of the bottom half inner casing (4). Thermal expansion in the axial direction originates from these points. Radial expansion is not prevented by these fitted keys, as they are free to slide in the recesses of the bottom half outer casing. Shoulders on the bottom half outer casing (5) project into corresponding recesses in the bottom half inner

casing (4) (4) and together with the fitted keys keys (14) provide a centering system for the inner casing (3, 4) in the transverse plane This arrangement allows axial and radial expansion of the inner casing relative to the outer casing while the fitted keys (14) maintain transverse alignment.

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IP Turbine Blading


Gap SealIng Sealing strips (7) are caulked into the inner casing (1) and the rotor (4) to reduce leakage losses at the blade tips. Cylindrically machined surfaces on the blade shrouds are opposite the sealing strips. These surfaces have stepped diameters in order to increase the turbulence of the steam and thus the sealing effect. In case of an operation disturbance, causing the sealing strips to come into contact with opposite surfaces, they are rubbed away without any considerable amount of heat being generated. They can then easily be renewed at a later date to provide the specified clearances.

Moving and Stationary Blades The IP turbine with advance blading consists of 2x12 (double flow) drum stages. All stages are reaction stages with 50% reaction. The stationary and moving blades of all stages are provided with inverted T -roots in moving blade and hook type roots in Guide blade which also determine the distance between the blades. All these blades are provided with integral shrouds, which after installation form a continuous shroud. The moving and stationary blades are inserted into appropriately shaped grooves in the rotor (4) and in the inner casing (1) and are bottom caulked with caulking material (5). The insertion slot in the rotor is closed by a locking blade which is fixed by grub screws. End blades, which lock with the horizontal joint are used at the horizontal joint of the inner casing (1).

1

1 Inner Casing 2 Guide Blade 3 Moving Blade 4 Turbine Shaft 5 Caulking piece 6 Sealing strip 7 Caulking wire

5

2

6

4

7 5

BHEL Haridwar

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Function The function of the shaft seals is to seal the interior of the turbine casing against the atmosphere at the front (thrust bearing end) and rear shaft penetrations of the IP turbine. The shaft seals are axial-steam-flow noncontacting seals. In the region subject to low relative expansion in the vicinity of the combined journal and thrust bearing, the seal strips are caulked alternatively into the shaft and into springsupported segmented rings in the casing, forming a labyrinth to impede the outflow of steam. In the region subject to greater relative expansion at the exhaust end, see-through seals are used, in which the seal strips are located opposite each other,

BHEL Haridwar

IP Turbine Shaft Seals

caulked into the shaft and into seal rings centered in the outer casing. The outer seal rings can be removed for inspection and if necessary seal strips can be replaced during a short turbine shut down keeping module in place. Gap Sealing Sealing between the rotating and stationary elements of the turbine is achieved by means of seal strip (9) ,caulked into seal rings (3;5) and into the rotor (4) (details A and C). The pressure gradient across the seal is reduced by conversion of pressure energy into velocity energy which is then dissipated as turbulence as the steam passes through the numerous compartments according to the labyrinth principle.

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Seal Rings The seal rings (3), the number of which depends on the pressure gradient to be sealed are divided into several segments as shown in Section BB and mounted in grooves in the rings such that they are free to move radially. Each segment is held in position against a shoulder by by helical springs (6) and by the steam pressure above the seal rings (3). This provides the proper clearance for the seal gaps. Should rubbing occur the segments concerned can retreat. The heat developed by light rubbing of the thin seal strips (9) is so slight that it cannot cause deformation of the rotor (4).

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When the turbine is started from the cold or warm state, the seal rings naturally heat up faster than the mounting rings. However. they can expand freely in the radial direction against the centering force of the helical springs (6). Steam Spaces Steam spaces are provided within the shaft seals. From space ‘P’ leakage is drawn off to the steam seal header. The slight amount of leakage steam which are still able to pass the seal ring are conducted from the space ‘R’ into the seal steam condenser.

IP Turbine


RearBearing Pedestal

Arrangement The bearing pedestal is located between the IP and LP turbines. Its function is to support the turbine casing and bear the weight of IP and LP rotors. The bearing pedestal houses the following turbine components: • • • •

Journal bearing Shaft vibration pick-up Bearing pedestal vibration pick-up Hand barring arrangement


of

Bearing

Pedestal

and

The bearing pedestal is aligned on the foundation by means of hexagon head screws that are screwed into it at several points. On completion of alignment the space beneath the bearing pedestal is filled with special non shrinking grout. The bearing pedestal is anchored to the foundation by means of anchor bolts. The anchor bolt holes are filled with gravel which gives a considerable vibration damping effect.

BHEL Haridwar

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Construction The function of the journal bearing is to support the turbine rotor. Essentially, the journal bearing consists of the upper and lower shells (3, 6), bearing cap (1), torus piece (7), cylindrical support (14) and the keys (10). The bearing shells are provided with a babbit face which is precision machined. Additional scraping is neither necessary nor permissible. Both bearing shells are fixed by means of taper pins and bolted together. In order to prevent the bearing from exerting a bending moment on the rotor (5), it is pivotmounted in the cylindrical support (14). For this purpose, the torus piece (7) with shims (12, 13) is bolted to the bearing shell (6). A projection in cap (1) with key (9) fits into a corresponding groove in the bearing shell (3) and prevents vertical movement of the bearing shells. Centering of the bearing shells in the vertical plane is achieved by means of keys (8).

BHEL Haridwar

IP Rear Journal Bearing

The bearing shells are fixed laterally by spacers (10) which are bolted to each other. Each spacer is held in position in the bearing pedestal (11) by two laterall collars. The temperature of the bearing bodies is monitored by thermocouples (15) as shown in section C-C.

Oil Supply Lubricating oil is admitted to the bearing shells from both sides, from where it flows to oil spaces milled into the upper and lower shells at the horizontal joint that are open to the rotor end. Oil from the oil space machined in the babbitting is carried through the rotor (5) and emerges from the bearing shell from where it is collected in the oil return cowling (4) and drained into the bearing pedestal (11).

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Jacking Oil As shown in section B-B, two threaded nozzles (17) are arranged at the lowest point of the lower bearing shell (6) through which high pressure oil is supplied to the space below the journal when the rotor is turning at low speed (on start-up and shutdown). This high pressure oil floats the shaft to prevent dry friction and overcome breakaway torque during startup, thus reducing torque requirements of the hydraulic turning gear. A seal (18) prevents high pressure oil from penetrating the space between threaded nozzle and ring (16) and thus from lifting the babbit. Any leakage oil can drain through passages in the bearing shell below the ring.

Removal of Bearing Shells Not only the upper shell (3) but also the lower bearing shell (6) can be removed without the removal of rotor (5). To enable this to be done, the shaft is lifted slightly by means of jacking device but with in the clearance of the shaft seals. The lower bearing shell can then be turned upwards to the top position and removed.

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IP Turbine Casing Supports and Guides

The turbine casing is supported on the support horns such as to make allowance for the thermal expansion.

It is essential for the casing to retain concentric alignment with the rotor which is supported independently

1 HP Turbine rear rear bearing pedestal pedestal 2 IP turbine 3 IP turbine rear bearing pedestal

Fig.1 Connection between turbine casing and bearing pedestal

BHEL Haridwar

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The turbine casing (2) is supported with its two front and two rear support horns on the bearing pedestals(1,3) at the turbine centerline level. This arrangement determines the height of the casing and also allows thermal expansion to take place in the horizontal plane by the support horns sliding on the sliding pieces (6;16) of the bearing pedestals (1,3). To prevent lift off the turbine casing (2), holders (4;15) hold down projections of the support horns which engage in mating recesses in the bearing pedestal. When the turbine is being erected, a clearance ’s’ is established between the thrust bars (5;14) and the turbine casing (2) support horn projection. Guides

Fixed Point

The central location of the turbine casing at right angles to the turbine centerline is provided by the guides shown in section B.B .These guides allow the turbine casing to expand freely.

The fixed point for the turbine casing (2) is located at the front horn support at the turbine centerline level and is formed by the parallel keys ((7;10). Axial expansion of turbine casing (2) originates from this point

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LP Turbine Casing

Construction The LP turbine casing consists of a doubleflow unit and has a triple shell welded casing. The outer casing consists of the front and rear walls, the two lateral longitudinal support beams and the upper part. The front and rear walls as well as the connection areas of the upper part are reinforced by means of circular box beams. The outer casing is supported by the ends of the longitudinal beams on the base plates of the foundation.

1 2 3 4

Outer casing, casing, upper half Diffuser, upper half half Inner outer casing upper half Inner- inner inner casing, upper upper half

Inlet Connections Steam admitted to the LP turbine from the IP turbine flows into the inner casing (4,5) from both sides through steam inlet nozzles before the LP blading Expansion bellows are provided in the steam piping to prevent any undesirable deformation of the casings due to thermal expansion of the steam piping.

5 6 7 8

Inner inner casing, casing, lower half Inner outer casing lower half half Diffuser lower half Outer casing lower half

Fig. 1 LP Turbine (Longitudinal section) BHEL Haridwar

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Arrangement of Inner Casing in Outer Casing The LP casing has a double-flow inner casing. This inner casing is a double shell construction and consists of the outer part (3,6) and the inner part (4,5). The inner shell is suspended in the outer shell to allow thermal movement and carries the front guide blade rows. The rear guide blade rows of the LP stage are bolted to the outer shell of the inner casing. The complete inner casing is supported in the LP outer casing (1,8) in a manner permitting free radial expansion concentric with the shaft and axial expansion from a fixed point (Fig.2). Support and Guiding of Outer Casing The outer casing rests with the brackets at the end of the longitudinal beam on the base plates fixed to the foundation crossbeam. The outer casing of the LP turbine is axially fixed at the respective front brackets (Fig.2). In the lower area of the circular beams which reinforce the front and rear walls of the outer casing, the casing is guided in the vertical centre plane (Fig.1, 3) which takes the radial and axial expansion into account.

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Two guide plates are welded vertically to the lower inner bend of each of the beams. The guiding piece (12) which is rigidly connected to the foundation crossbar, fits between these plates. Fitted pieces(11) inserted between the square guiding piece(12) and the plates maintain alignment of the casing in the centre plane and permit expansion transverse to the axis of the machine. Support and Guiding of Inner Casing in Outer Casing The complete assembled inner casing rests in the horizontal plane with 4 brakets on the sliding piece(15, 18) placed in the plates bolted to the longitudinal support beam of the casing. The two brackets (detail C Fig.5) on the turbine side are fixed in the axial direction by fitted keys (16) as opposed to the brackets on the generator side (detail D Fig.6) which are not fixed. Any thermal expansion in the axial direction thus originates from here. The spacer bolts( 17) prevent lifting of the inner casing. The clearance of these spacer bolts in the holes of the brackets is dimensioned to permit the inner casing to expand horizontally on sliding piece (15) of the fixed support transverse to the axis of the machine, and on sliding piece (18) of the nonfixed support transverse and parallel to the machine axis. As thermal expansion in the vertical direction originates at approximately the level of the horizontal.

Fig.3 Guiding of the Outer Casing joint, the concentricity of the inner casing with wit h the shaft is ensured in this plane. As shown in detail E (Fig.2,4) two casing guides are located at the lower half (6) of the outer shell to prevent any transverse displacement of the inner casing from the centerline of the turbine. Radial and axial expansions is not prevented by fitted keys(14) in these casing guides Suspension of the Inner Shell The inner shell (4,5) is suspended in the outer shell (3,6) in the horizontal plane and is guided axially in the vertical plane (Fig.7and 8). In the horizontal plane, the upper half (4) of the inner shell is supported by four brackets resting on the support plates (21,22) located at L and M of the joint face of the lower half half of the outer shell (Fig.9 & 10). The brackets of the upper part (3) of the outer shell which project over the cover plates (20) , prevent lifting of the inner shell. The slight clearance between these cover plates and the brackets permits free horizontal expansion of the inner shell in all directions at the support points. Thermal expansion in the vertical plane originates at the joint face. This ensures concentricity of the inner shell with the shaft in this plane.

serve to align the inner shell, lower half (5) in the outer shell, lower half (6) by the use of jacking bolts during erection. On the IP turbine side, 2 fitted keys (19) are inserted between each bracket and recess. As shown in detail L, these fitted keys fix the inner shell in the axial direction and thermal expansion thus originates from here

The brackets of the inner shell, lower half (5) project into recesses of the outer shell, lower half (6) These brackets are provided with clearance on all sides and

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3 Outer shell, upper half 4 Inner shell, upper half 5 Inner shell, lower half 6 Outer shell, lower half Fig. 7 Inner Casing, Longitudinal Section In the vertical plane 4 centering pins (26) which are guided in bushings (25) are provided for the suspension as shown in detail A Fig. 11. The lower ends of the centering pins are fitted into keys (27) which slide in axial grooves in the inner shell. This arrangement permits axial displacement of the inner shell relative to the keys (27) and vertical displacement along the axis of the centering pins(26) while displacement transverse to the axis of the unit prevented by the keys. Thermal expansion transverse to the axis of the unit originates from these keys so that concentricity of the inner shell with the shaft is also maintained in this plane. The bushings (25) have an eccentric bore and by turning them during alignment of the inner casing, the inner shell can be moved laterally. After the alignment has been completed, the bushings are fixed in position by grub screws.

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Atmospheric relief diaphragms are provided in the upper half of each LP exhaust end section to protect the turbine against excessive pressure. In the event of failure of the low vacuum trips the pressure in the LP turbine exhaust rises to an excessively high level until the force acting on the rupturing disc (1) ruptures the breakable diaphragm (2) thus providing a discharge path for the steam. The diaphragm

BHEL Haridwar

Atmospheric Relief Diaphragm

consists of a thin rolled lead plate. To insure that the remnants of the diaphragm and rupturing disc are not carried along by the blow-off steam a cage with brackets (5) is provided. As long as there is a vacuum in the condenser the atmospheric pressure forces the breakable diaphragm and the rupturing disc against the supporting flange (3).

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LP Turbine

Blading, Drum Blading

Arrangement The drum blading stages 1 to 3 of the double flow LP turbine are of reaction type with 50% reaction. They are Located in the inner-Inner casing and form the initial stages of the LP blading. The LP stages following these drum stages are described in detail in next chapter. Guide and moving blades All guide and moving blades of drum stages have integral shrouds, which after installation form a continuous shrouding. The moving blades (7) of the last drum stage are tapered and twisted. All stationary and moving blades have T -roots which also determine the distance between the blades. They are inserted into the matching grooves in the turbine shaft (5) and inner casing (1) and are caulked in place with caulking material (6). The insertion slot in the rotor is closed by means of a locking blade which is secured in its position by means of grub screws between shaft and lock blade .In casing, blades at joint planes are fixed by means of grub screws. Inter stage Sealing In order to reduce blade tip losses, tip to tip sealings are provided in these stages. Thin sealing strips (9) are caulked in inner casing (1) and turbine rotor (5). The sealing fins are machined on the shrouds of moving and stationary blades opposite to the sealing strips in inner casing or rotor (Detail A). In the event of rubbing due to a fault , little heat will be generated due to rubbing of thin sealing strips. These can be renewed at a later date to provide the correct radial clearances.

BHEL Haridwar

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Guide and Moving Blades The last three stages of the LP turbine are also reaction stages. Each stage is made up of guide and moving blades.

The stationary blade rows (2, 5, 7) are made by welding inner ring, blades and outer ring together to form Guide Blade Carriers in two halves, that are bolted to inner outer casing (1). The blades of rows 2 & 5 are of precision cast steels and the blades of row 7 are made

BHEL Haridwar

LP Turbine Blading, Low Pressure Stages

from steel sheets to form hollow blades. Suction slits are provided in the blades of row (7). Through these slits water particles on the surface of these last stage guide blades are drawn away to the condenser. The moving blades (3) of first LP stage are tapered,

twisted and have integral shrouds with T -root. The last two stages of moving blades (6,8) have curved fir-tree roots (View-X) which are inserted in axial grooves in the turbine shaft (4) and secured by means of clamping pieces (11). Axial movement of the blades

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is prevented by segments of locking plate segments (12) and the end segments are spot welded at joint. The difference in circumferential speed at the root and tip of the moving blades is taken into consideration by the twisted design of the blades.

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Inter stage sealing In order to reduce blade tip losses at the stationary blade rows (2,5,7). sealing strips (9) are caulked into turbine shaft. Opposite to this, sealing strips are also caulked on the inner ring of stationary blade rows as shown in Detail A. This arrangement permits favourable radial clearances to be attained. In case of rubbing, the thin seal strips are worn away without generating much heat. They can be easily replaced at a later date to restore the required clearances.


LP Turbine Shaft Seals

Function The function of the axial shaft seals situated between the bearing casings and the LP exhaust casing is to seal the inner space of the LP exhaust casing against atmospheric pressure at the passages through the shaft s haft. Gap Sealing The sealing effect between the moving and stationary parts of the turbine is achieved by means of sealing strips (4) which are caulked into the individual seal rings (2), The prevailing pressure is reduced according to the labyrinth principle by conversion into velocity with subsequent turbulence in many sections.

strips (4) due to this light pressure are so slight that it cannot cause deformation of the rotor (5). When the turbine is started from the cold or semi-warm state, the sealing rings naturally heat up more quickly than the steam seal casings. They can then expand radially without hindrance against the centering force of the helical springs. Steam Spaces Steam spaces are provided within the shaft seal. When the plant is started up and in operation, sealing steam enters space “Q” to prevent air penetrating the space, which is under a vacuum. The slight amount of steam that passes the center seal ring is drawn off from space “R” into the seal steam condenser.

Sealing Rings The sealing rings (2), the number of which depends on the pressure existing in the turbine, are split into several segments as shown in section A-A and arranged in Tshaped annullar grooves in the steam seal casing (1) so that they can move radially. Several helical sprir1gs (3) force each segment against a shoulder and hold it in this position. This permits the correct clearance in the sealing gaps. Should rubbing occur, the segments concerned retreat. The frictional heat developed by the thin

BHEL Haridwar

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LP Turbine Rear Bearing Pedestal

Arrangement The bearing pedestal is situated between the LP turbine and generator. Its function is to bear the weight of LP rotor. The bearing pedestal following turbine components:

contains

the

Bearing pedestal vibration pick-up Journal bearing Shaft position measuring device Shaft vibration pick-up • • •


of

Bearing

Pedestal

and

The bearing pedestal is aligned on the foundation by hexagonal screws that are bolted into the bearing pedestal. To overcome friction resistance, balls are arranged under the heads of these hexagonal screws. After alignment the space under the bearing pedestal is filled in with special nonshrink grout, resistant to expansion and contraction. The bearing pedestal is also connected to the foundation by means of anchor bolts.

BHEL Haridwar

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Journal Bearing

Construction The function of the journal bearing is to support the turbine rotor. Essentially, the journal bearing consists of the upper and lower shells (3, 6), bearing cap (1), torus piece (7), cylindrical support (14) and the keys (10). The bearing shells are provided with a babbit face. The bearing bore is precision machined and additional scraping is neither necessary nor permissible. Both bearing shells are fixed by means of taper pins and bolted together. In order to prevent the bearing from exerting a bending moment on the rotor (5), it is pivot-mounted in the cylindrical support (14). For this purpose, the torus piece (7) with shims (12, 13) is firmly bolted to the bearing shell (6). A projection in cap (1) with shims (9) fits into a corresponding groove in the bearing shell (3) and prevents vertical movement of the bearing shells.. Centering of the bearing shells in the vertical plane is achieved by means of keys (8).

1 2 3 4

Cap Tab washer Upper bearing shell Oil return cowling

BHEL Haridwar

5 6 7 8

Rotor Lower bearing shell Torus piece Key

The bearing shells are fixed laterally by the keys (10) which are bolted to each other. Each key is held in position in the bearing pedestal (11) by two lateral collars. The temperature of the bearing is monitored monitored by thermocouples (15) as shown in section C-C. Oil Supply Lubricating oil is admitted to the bearing shells from both sides, from where it flows to oil spaces milled into the upper and lower shells at the horizontal joint that are open to the rotor end. Oil from the oil space machined in the babbitting is carried through the rotor (5) and emerges from the bearing shell from where it is collected in the oil return cowling (4) and drained into the bearing pedestal (11). Lift Oil As shown in section B-B threaded nozzles (17) are arranged at the lowest point of the lower bearing

9 Shim 10 Key

13 Shim 14 Cylindrical support

11 Bearing Pedestal 12 Shim

5.1-0470-00/1

shell (6) through which high pressure oil is supplied during start-up. This high pressure oil relieves the bearing to overcome breakaway torque and prevent dry friction, thus reducing the torque requirements of the hydraulic turning gear. The lift oil flows into the above mentioned threaded nozzles (17) through passages in the lower bearing shell (6). A seal (18) prevents high pressure oil from penetrating the space between threaded nozzle and ring (16) and thus from lifting the babbit. Any leakage oil can drain through passages in the bearing shell below the ring. Removal of bearing shells

Not only the upper shell (3) but also the lower bearing shell (6) can be removed without the removal of the shaft (5). To enable this to be done, the shaft is lifted slightly by means of the jacking device but within the clearance of the shaft seals. The lower bearing shell can then be rotated to the top position and removed.

15 16 17 18

Termocouple Ring Threaded nozzle Sealing ring

Also refer to tne following sections [1] 5.1-0510 Hydraulic Turning Gear

5.1-0470-00/2

Steam Turbine Description Arrangement The hydraulic turning gear is situated between the main oil pump and the journal bearing in the HP turbine front bearing pedestal.

Hydraulic Turing Gear

Function The function of the hydraulic turning gear is to rotate the shaft system at sufficient speed before start-up and after shut-down in order to avoid irregular heating up or cooling down and thus avoid any distortion of the turbine rotors. The air flow set up by the blades along the inner wall of the casing during turning operation provides good heat transfer conducive to temperature equalization between upper and lower casing halves. Operation During turning gear operation, the shaft system is rotated by a blade wheel which is driven by oil supplied by the auxiliary oil pump. This oil passes via a check valve into the nozzle box (1) and from there into the nozzles (2) which direct the oil jet in front of the blading. Return Oil Flow After passing the blading, the oil drains into the bearing pedestal and flows with the bearing oil into the return flow line. Manual Turning Gear A manual turning gear is provided in addition to the hydraulic turning gear to enable the combined shaft system to be rotated manually. Lifting of Shaft To overcome the initial break-away torque on start-up and to prevent dry friction, the bearings are relieved during turning gear operation by lifting oil supplied from below i.e. the shafts are lifted slightly.

BHEL Haridwar

5.1-0510-01


Function The turbine generator is equipped with a mechanical barring gear, which enables the combined shaft system to be rotated manually in the event of a failure of the normal hydraulic turning gear. It is located at IP - LP pedestal

Construction The barring gear consists of a gear machined on the rim of the turning gear wheel (10) and pawl (6). This pawl engages the ring gear and turns the shaft system when operated by means of a bar attached to laver (1). The pawl (6) is shown disengaged and the lever (1) resting against a stop. The lever (1) is held in position by latch (7).

BHEL Haridwar

Mechanical Barring Gear

Operation Take the following steps to make the barring gear ready for operation: Remove cover (2) unlatches at (7) and attach a bar to lever (1). Barring of lever (1) will rotate the combined turbine generator shaft system. After barring has been completed, return lever (1) and pawl (6) to the position shown in figure and secure lever (1) by means of latch (7) Replace cover (2). The barring gear may only be operated after the shaft system has been lifted with high-pressure lift oil. If it is hard to start turning by means of the mechanical barring gear, this may be due to incorrect adjustment of the jacking oil system or due to a rubbing shaft. Before steam is admitted to the turbine. corrective action must be taken

5.1-0520-01

Steam Turbine Description Function When the turbine is started up or shut down, the hydraulic jacking device is used to maintain the oil film between rotor and bearings. The high-pressure oil is forced under the individual bearing, thus raising the rotor. The necessary torque from the hydraulic turning device or from the manual turning device is reduced in this way. The highpressure oil also provides motive force to hydraulic turning gear motor installed in front bearing pedestal . Speed Limit Values In order to avoid damage to the bearings, the jacking oil pump must be switched on below a certain speed. The exact speeds for switching on and off can be seen in the Technical data 2-0103. Jacking Oil Pump The jacking oil pumps, one number AC (13) and one number DC(14) are jack-screw immersion pumps situated on the tank (10) supply the high pressure oil for the lifting device. The oil is drawn off directly by one of the two pumps. The pressure oil piping of the jacking oil pump that is not in operation is closed by the check valve (12). In order

1 HP turblne 2 IP turblne 3 LP turblne 4 Generator 5 Exciter

6 Check Valve 7 Fine control valve 8 Pressure Pressure Limiting Device 9 Bypass Valve 10 Main Oil Tank

BHEL Haridwar

Hydraulic Jacking Device

to protect the jacking oil system from damage due to improper switching ON of the jacking oil pump when the check valve (12) is closed, a spring-loaded safety valve (11) is situated in the piping between the jacking oil pump (13) and the check valve (12). The necessary pressure in the system is kept constant by means of the pressure-limiting valve (8). The pressure-limiting valve can be relieved by the bypass valve (9). The superfluous flow from the pump is conducted into the main oil tank. The necessary jacking oil pressures are set for each bearing by the fine control valves (7) in the oil pipes. Check valve (6) in the jacking oil pipes p ipes prevent oil from flowing out of the bearings into the header during turbine operation when the jacking oil system is naturally switched off. Valve Arrangement The fine control valve (7) of the turbine bearings, the check valves (6) and the pressure gauges are arranged in boxes, which are connected laterally to the bearing pedestals.

11 12 13 14 15

AC Motor driven lifting oil pump 16 Valve DC Motor driven driven lifting oil pump c Drain Spring loaded safety valve Check valve Duplex filter 5.1-0530-63-1

Steam Turbine Description The turbine control system description for 500 MW steam turbine comprises the following: General Description Start-up Procedure Speed Control Electrical Speed Measuring Protective Devices Overspeed Trip Test Testing of Stop Valves Bypass Control System (General) Electro-hydraulic Bypass Control (Electrical System) Electro-hydraulic Bypass Control (Hydraulic System) Extraction Check Valve Swing Check Valve in CRH line Testing of Swing Check Valves in the Cold Reheat Line Automatic Turbine Tester, General Automatic Turbine Tester, Protective Devices Automatic Turbine Tester, Stop Valves HP Actuator Electro-hydraulic Gland Steam Pressure Control Control System Diagram List of Parts Lubrication Chart Lubrication Chart, Index Turbine generator unit MAA50HA001 MAB50HA001and MAC10HA001 comprises three-cylinder reheat condensing turbine with condenser MAG10BC001 and a directdriven three-phase a.c. generator. The turbine has a hydraulic speed governor MAX46BY001 and an electric turbine controller. The hydraulic speed governor adjusts control valves MAA10+20AA002 and MAB10+20AA002 by way of hydraulic amplifier MAX45BY011 whilst the electric turbine controller acts on these control valves by way of electro-hydraulic converter MAX45BY001. Hydraulic amplifier MAX45BY011 and electro-hydraulic converter MAX45BY001 are switched in parallel to form a minimum gate. The system not exercising control is in its maximum position.

BHEL Hardwar

General Description

The special operating conditions existing in reheat condensing turbines necessitate additional control elements. On start-up of the high-pressure boiler it is necessary to start up the turbine straight away with a considerable steam rate and, due to the high temperature in the reheater to admit steam to the reheater immediately. As long as the HP section of the turbine is unable to accommodate all the steam supplied by the boiler, the rejected steam is routed directly to the reheater via HP bypass valve. The steam from the reheater which cannot be accommodated by the IP section with its control valves MAB10+20AA002 and reheat stop valves MAB10+20AA001 is routed into condenser MAG10BC001 by way of LP bypass stop & control valves MAN11+12AA001 and MAN11+12AA002. The IP turbine must be fitted with its own control valves to prevent steam remaining in the reheater from entering the turbine via the IP and LP section and causing further acceleration of the turbine after the main steam control valves have been closed in the event of load rejection or trip. In addition, the steam pressure in the main steam line would increase after sudden closure of the main steam control valves, thus causing the HP by pass valve to open, with the result that even more steam would flow into the IP section of the turbine. It is the function of main oil pump MAV21 AP001, driven directly by the turbine shaft, to supply oil for bearing lubrication, for the oil circuit for the overspeed trip test, and for the primary oil circuit, pressure in which is generated by hydraulic speed transmitter MAX44AP001.Two Electrically driven auxiliary oil pumps are provided for auxiliary oil supply. The LP control fluid circuit (8 bar) and the HP actuators of the main steam control valves, reheat control valves, LP bypass stop & control valves (32bar) are supplied by two full-load control fluid pumps installed in the control fluid tank. The turbine is equipped with an electrohydraulic seal steam control system, an electro-hydraulic bypass control system, an

5.1-0600-01/1

automatic turbine tester for the protective devices, main and reheat “Stop & Control Valves” and an automatic functional group control.

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Mode of Operation The turbine is started up and brought up to speed with the assistance of the control valves MAA10+20AA002 and MAB10+20 AA002. If the hydraulic controller is to govern start-up, the reference speed setter MAX46BY001 must be set to minimum speed during this process. In this case the speed reference from the electric controller is at maximum. If conversely, start-up is to be governed by the electric controller, reference speed setter MAX46 BY001 is set to maximum and the speed reference from the electric controller to minimum. The combined stop and control valves are closed because the trip fluid circuit is not yet pressurized. Turning hand-wheel KA01 clockwise or operating motor MAX47BY001M of start-up and load limiting device MAX47BY001 in the close direction releases spring KA06 in auxiliary follow up piston KA08 via the linkage, thereby preventing a buildup of auxiliary secondary fluid pressure. The hydraulic amplifier MAX45BY011 with follow-up pistons KA01 and KA02 is now in the control valves closed position so that a buildup of secondary fluid pressure is prevented when main trip valves MAX51AA005 and MAX51M006 are latched in. Further turning of hand-wheel KA01 moves pilot valve KA02 of start-up and load limiting device MAX47BY001 further downwards, admitting control fluid first into the start-up fluid circuit and then into the auxiliary start up fluid circuit. The start-up fluid flows to the space above the pilot valve of test valves MAX47AA011+012 and MAX47AA021+ 022, forcing them down against the action of the springs. The auxiliary start-up fluid raises the pilot valves of main trip valves MAX51AA005 and MAX51AA006, thereby moving them into their normal operating position and permitting trip fluid to flow to test valves MAX47AA011+012 and MAX47AA021+022 of the main stop valves and reheat stop valves. At the same time, overspeed trip release devices MAY10AA001 and 002 are latched in if they have been tripped. The function of non return valve MAX42AA011 is to interrupt BHEL Hardwar

Start-up Procedure

transiently the fluid supply to solenoid valve MAX48AA202 from the connection downstream of filters MAX42BT001 and MAX42BT 002 during latching in of main trip Valves MAX51AA005 and MAX51AA006 by means of start-up and load limiting device MAX47BY001, because the pressure drops in this line considerably for a short time as a result of the high flow of fluid required to fill the drained trip fluid system during this latching in-period. The pressure upstream of solenoid valve MAX48AA202 is maintained via orifice MAX42BP022 during this period. This ensures that the solenoid valve remains in the position shown. The auxiliary start-up fluid circuit at the start-up and load-limiting device MAX47BY001 is fed from the system down stream of filter MAX42BT003 (fluid supply during testing), since the pressure in the system is subject to no significant change during start-up. It is not possible to supply the hydraulic fluid connection of solenoid valve MAX48AA202 from this system, as this would have an in admissible effect on the trip fluid system while the latching operation with the solenoid valves MAX48AA201 and MAX48AA202 during testing is taking place. After latching in, the trip fluid circuit is closed. The trip fluid now flows to the space above servomotor piston KA01 of stop valves MAA10+20AA001 and MAB10+20 AA001 forcing it down against piston discs KA002. Operation of the start-up and loadlimiting device is continued until their lower limit position is reached. When hand-wheel KA01 is turned back or motor MAX47BY001M of start-up and load limiting device MAX47BY001 is operated in the open direction, the control fluid is allowed to drain first from the auxiliary startup fluid circuit and then from the start-up fluid circuit. The pilot valve of test valves MAX47AA011+012 and MAX47 AA021+022 are forced upwards by the springs, whereupon the trip fluid above servomotor piston KA01 slowly drains off. The pressure difference thus created lifts both pistons together into their upper limit position, thus causing main stop valves MAA10+20 AA001 and reheat stop valves MAB10+20 AA001 to

5.1-0610-01/1

open. Main trip valves MAX51AA005 and MAX51AA006 are now held in their operating position by the fluid pressure beneath the differential piston. Once the main & reheat stop valves are open, further turning of hand-wheel KA01 or operation of motor MAX47BY001M of the start -up and load limiting device in the open direction will after passing through a certain dead range, cause lever KA03 and sleeve KA04 to move further downwards, as a result of which the auxiliary secondary fluid pressure begins to increase and acts via hydraulic amplifier MAX45 BY011 and follow up pistons KA01 and KA02 to gradually open control valves MAA10+20AA002 and MAB10+20AA002. This brings the turbine up to about 85 to 90% rated speed. Speed controller MAX46BY001 now cuts in to maintain turbine speed. Start-up and load limiting device MAX47BY001 is then brought into the fully open position. A pressure gauge MAX44CP501 and electric speed transducer MYA001CS011-013 are used to measure speed. Reference speed setter MAX46BY001 is used for further speed run-up for connecting the turbine-generator unit in parallel and for bringing it on load. Turning hand-wheel KA01 of the reference speed setter or operation of motor MAX46BY001M increase the tension of speed setting spring KA02 to increase speed. Since in interconnected operation speed is determined by grid conditions, actuation of the reference speed

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setter has the effect of changing turbine output. Load Limitation Start-up and load limiting device MAX47BY001 engages mechanically in controller bellow KA09 of hydraulic speed governor/controller MAX46BY001 so that it can serve simultaneously as a load-limiting device. This means that opening of the control valves MAA10+20AA002 and MAB10+20 AA002 is limited to an adjustable setting. This setting is made manually or from the control room via motor MAX47BY001M. Electro-hydraulic Turbine Controller If the turbine is to be started up with the electro-hydraulic turbine controller, the reference signal from the electric speed controller must first be set to minimum so that this takes over running up the turbine generator unit from turning speed. Start-up and load limiting device MAX47BY001 is brought into its open position once the stop valves have been opened. Slowly raising the speed reference from the electric controller cuts in the electric speed control system, and the turbine-generator unit is brought up to rated speed and synchronized. Further loading is governed by the electric power controller by increasing the load reference within the admissible rate of load change.


Speed control may be exercised either hydraulically or electro-hydraulically. Hydraulic Control Main oil pump MAV21AP001 supplies the bearing and primary oil circuits with control oil whilst hydraulic speed transmitter MAX44AP001 acts as a pulse generator for the control circuit, providing a primary oil pressure proportional to the speed. This oil pressure can also be read directly from speed indicator pressure gauge MAX44CP501. This primary oil pressure acts on diaphragm KA09 of hydraulic speed governor MAX46BY001 against the force of speed setting spring KA02 which is tensioned by reference speed setter MAX46BY001.The travel of diaphragm KA09, which can be limited by starting and load limit device MAX47BY001, is transmitted by linkage KA03 to sleeves KA04 of auxiliary follow-up pistons KA08, the pistons KA05 of which are held against the medium pressure by spring KA06. Medium drains off according to the amount of port overlap between piston and sleeve and a medium pressure corresponding to the tension of spring KA06 is built up. This auxiliary secondary medium pressure acts as a pulse signal via pilot valve KA07 of hydraulic amplifier MAX45 BY011. Piston KA08 of this hydraulic amplifier assumes a position corresponding to the auxiliary secondary medium pressure and operates the sleeves of follow-up piston KA01and KA02 via a linkage system. A feedback system stabilizes the position of pilot valve KA07 and piston KA08 of hydraulic amplifier MAX45BY011. As already described for auxiliary follow-up piston KA08, a secondary medium pressure corresponding to the position of the sleeves and to the related spring tension builds up in the follow up pistons of hydraulic amplifier MAX45BY011. Any change in the position of linkage KA03 results in a proportional change of the BHEL Hardwar

Speed Control

secondary medium pressures in the follow-up pistons of the hydraulic amplifier. The secondary medium circuits and the auxiliary secondary medium circuits are supplied from the trip medium circuit by way of orifices. The varying secondary medium pressure in the follow-up pistons of the hydraulic amplifier in turn effects changes in the positions of their associated control valves or other control devices. Electro-hydraulic Control The speed digitally. For transducers mounted on turbine shaft.

of the turbine is measured this purpose electrical speed MYA01CS011 to 013 are the high-pressure end of the

The electro-hydraulic converter constitutes the link between the electrical and hydraulic parts of the governing system. The electrohydraulic converter consists of the speed control converter MAX45BY001 and a plunger coil system CG001T. The signal from the electro-hydraulic controller actuates the control sleeve via the plunger coil system. The control sleeve determines the position of pilot valve KA07 in the manner of a follow-up piston. The further mode of action is the same as that of the hydraulic speed governor. Two differential transmitters CG001A and CG001K are located at piston KA08 of electro-hydraulic converter MAX45 BY001 as feedback transmitters to the electro-hydraulic controller. This stabilizes the control process. Change-over from Hydraulic to Electrohydraulic Control As already mentioned, Change-over from one control system to the other is possible even during operation as the two controllers are connected in parallel downstream of the associated follow up piston batteries, which form a minimum value gate. This means that

5.1-0620-01/1

it is always the controller with the lower set point, which leads. If the turbine is operated with the hydraulic governor, the speed set point of the electrohydraulic controller is set at “maximum speed” which prevents the electro-hydraulic control system from coming into action. To bring in the electro-hydraulic control system, the speed set point of the electrohydraulic controller must be reduced slowly until the secondary medium pressures drop slightly. When this occurs, the electrohydraulic controller has taken over. Then the reference speed setter of hydraulic governor speed MAX46BY001 is set to “maximum speed”. The electro-hydraulic controller is then fully effective and can operate over the entire load range. The hydraulic speed governor also acts as a speed limiter in the event of failure of the electro-hydraulic controller. In this case, operation of the turbine may immediately be continued by means of the hydraulic speed governor. Change-over from Electro-hydraulic to Hydraulic Control Change-over is performed in the reverse sequence. First reduce the set point at reference speed setter MAX46BY001 until the secondary medium pressures drop slightly. This indicates that the hydraulic speed governor has taken over. Then set the set point of the electro-hydraulic controller to maximum. The hydraulic speed governor is then completely effective and can operate over the entire load range. Adjusting Device for Valves An adjusting device, which makes it possible to change the setting response of the HP and IP control valves, is provided for limiting the HP exhaust steam temperature. In normal operation, control medium is admitted to the space below the pistons of

5.1-0620-01/2

regulating cylinders MAX45BY001 KA10 and MAX45BY011 KA10 by way of energizing solenoid valve MAX42AA051, whereby the pistons move into their upper end positions against the force of the spring and, via a linkage, tension the springs of follow-up pistons KA02 of the control valves in such a way that this produces the desired setting response of the IP control valves in relation to the HP control valves. If the condition “Turbine load less than set minimum load and the ratio of HP exhaust steam pressure to main steam pressure greater than a set value is fulfilled ”, ”, e.g. after a load rejection, solenoid valve MAX42AA051 is de-energised, thereby cutting off the flow of control medium to the regulating cylinders and allowing the control medium under the pistons to drain off. The pistons are moved into their lower end position by the restoring springs and the springs of follow-up pistons KA02 are adjusted so that the IP control valves do not begin to open until the HP control valves have opened to a greater extent, with the result that the HP exhaust steam temperature is lowered. For operation of the plant without the HP and LP bypass stations, a manual adjusting mechanism KA11 is also provided for adjusting the relationship between the valves such that the reheat valves open before the main steam valves. Under these operating conditions, solenoid valve MAX42AA051 is energised and an interlock is provided to prevent de-energisation. This adjustment may only be performed manually and must always be performed on both follow-up piston batteries MAX45BY001 and MAX45BY011, to ensure that changeover from hydraulic to electro-hydraulic control and vice versa is possible at all times. This manual adjustment must always be reversed before the HP or LP bypass station is brought into operation.


The electrical speed signals originate from the electrical speed transducers which consist of four ferromagnetic type speed probes, MAY01CS011 to 014 (one as spare) and a toothed wheel with 60 teeth made around its circumference located on the main oil pump shaft. The teeth of the wheel act upon the four stationary speed probes. When turbine rotates, square wave signals are generated in the probes. The frequency of these voltages is proportional to the rotational speed of the turbine. The output of these speed probes are fed to the input modules which provide digital output signals. The three values for the rotational speed obtained by this process are continuously monitored for failures. If one of the speed probes fail, the control circuit continues to operate without interruption, using two

BHEL Hardwar

Control System Electrical Speed Measuring

remaining speed probes. The output is then fed to the speed measuring unit, electrohydraulic controller and speed target unit. The speed-measuring unit incorporates two speed ranges. The lower range covers 0360 rpm and the upper range 0-3600 rpm. The changeover from one range to the other is completely automatic. A speed indicator mounted on the hydraulic control equipment rack provides local speed-readings. Indicating lights located near the speed indicator show which range is engaged. From the speed-measuring unit, speed signals are also provided to the turbine stress evaluator/controller, automatic turbine tester and recorders. Output signals are available for purchaser’s remote speed indicators and functional group automatic (FGA).

5.1-0621-02


Protective Devices

Overspeed Trip

Low-Vacuum Trip for Turbine Protection

Two overspeed trips MAY10 AA001 and 002 are provided to trip/shut down the turbine in the event of overspeed. Each trip device consists of an eccentric bolt/striker fitted in the emergency governor shaft with its center of gravity displaced from the axis of rotation and held In position against centrifugal force by a spring up to an adjustable preset speed of 10 to 12 % above the normal turbine operating speed. At the preset overspeed, centrifugal force overcomes the spring force and the eccentric bolt/striker flies outwards into its extended position. In doing so it strikes the pawl which releases the piston of the overspeed trip release device KA01. Through combined spring force and fluid pressure, the piston opens the auxiliary trip fluid circuit to the main trip valves MAX51 AA005 and MAX51AA006.

An increase of pressure in the condenser causes the valve of low-vacuum trip MAG01 AA011 to move downwards from its upper position under the force of the pre-tensioned spring. This action depressurizes the space below the right-hand valve. The right-hand valve is moved into its lower position by a spring and thus opens the auxiliary trip fluid circuit. Opening the auxiliary trip fluid circuit depressurizes the fluid below the differential pistons of main trip valves MAX51AA005 and MAX51AA006 and the differential pistons are activated by a spring. This closes the control fluid inlet to the trip fluid circuit and at the same time opens the main trip fluid circuit to drain, causing the trip fluid pressure to drop and all stop and control valves of the turbine to close. Limit switch MAG01CG011B signals to the control room that the low-vacuum trip is not in its normal operational position. Limit switch MAG01 CG011C indicates in the control room that turbine trip has been initiated by the lowvacuum trip.

Thrust-Bearing Trip Thrust bearing trips MAD12CY011/012/013 are tripped electrically in the event of excessive axial displacement of the turbine shaft. Pressure Switch Installed in the trip fluid circuit are two pressure switches MAX51CP011 and MAX51CP012 which bridge the longtime delayed relays of the reverse-power protection system in such a way that the generator is shut down by response of the short-time delayed relays as soon as it begins to motor. The annunciation Turbine trip initiated is transmitted simultaneously to the control room. Remote Solenoid Trip Remote solenoid trip is activated via solenoid valves MAX52 AA001 and MAX52 AA002. The remote solenoid trip may be initiated manually from the control room by push button, by the electrical low-vacuum trip or the thrust bearing trip or other protective devices.

BHEL Hardwar

To make it possible to latch-in the trip devices and thus to build up trip fluid pressure for adjusting and testing the control loop or similar purposes when the turbine is shut down and no vacuum exists, the lowvacuum trip has an auxiliary piston which is loaded with primary oil pressure above the adjustable compression spring. When the turbine is shut down there is no primary oil pressure and so the auxiliary piston is unable to tension the adjustable compression spring arranged above the diaphragm system. The spring below the diaphragm system lifts the valve, closing the auxiliary trip fluid circuit so that the trip devices can be latched in. As soon as the turbine is started up and brought up to speed, primary oil enters the space above the auxiliary piston, forcing in into its lower end position at a turbine speed far below rated speed. Thus the low-vacuum trip is reset for initiation of turbine trip before the turbine has reached rated speed.

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Solenoid Valves for Load Shedding Relay Solenoid valves MAX45 AA001 and MAX46 AA011 are provided to prevent the turbine from reaching trip-out speed in the event of a sudden load rejection. These solenoid valves are actuated by the load shedding relay if the rate of load drop relative to time exceeds a predetermined value. Solenoid valve MAX45AA001 opens the IP secondary fluid circuit directly. Solenoid valve MAX46 AA011 opens the auxiliary secondary fluid circuit. Pilot valve KA07 of hydraulic converter MAX45BY011 moves upward and allows the control fluid to flow to the area below piston KA08 of the converter. Piston KA08 moves to its upper end position, thereby depressurizing all secondary fluid circuits. Since the reheat IP secondary fluid circuit opens directly, the IP control valves (which control the major portion of the power output) close without any appreciable delay. A small delay is involved in closing all other control valves by depressurizing the auxiliary secondary fluid circuit, but his action is still performed before an increase in turbine speed causes the speed controller to respond. At the same time, the extraction check valves, which are dependent on secondary fluid via extraction valve relay MAX51AA011, close. After an adjustable interval, the solenoid valves are reclosed, permitting secondary fluid pressures corresponding to the reduced load to build up again. again. Turbine Trip Gear The trip fluid is taken from the control fluid

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via main trip valve MAX51AA005 and MAX51AA006 and flows both to the secondary fluid circuits and to the stop valves MAA10+20AA001 and MAB10+20AA001. The main trip valves serve to rapidly reduce the fluid pressure in the trip fluid circuit. If the pressure below the differential piston of main trip valves MAX51 AA005 and MAX51AA006 drops below a preset adjustable value, the piston in each valve is forced downwards by the spring, opening the drain passage for the trip fluid and closing the control fluid inlet. If the pressure in the trip fluid circuit drops below a predetermined value, spring loading separates the upper and lower pistons of main stop valves MAA10+20 AA001 and reheat stop valves MAB10+20 AA001, and all the stop valves close very rapidly. At the same time, the control valves and extraction check valves also close, as the secondary fluid circuits are fed from the trip fluid circuit. Thus on trip initiation, all turbine stop and control valves close. Manual local Trip Method of Initiating Turbine Trip Manual local initiation of turbine trip is performed by way of local trip valve MAX52 AA005. The valve must be pressed downwards manually, thus opening the drain passage for the auxiliary trip fluid. The two limit switches MAX52CG005C and MAX52 CG005E indicate in the control room that trip has been initiated locally by hand.


Testing with Condition

Turbine

under

Overspeed Trip Test

Load

Overspeed trips MAY10 AA001 and 002 can be tested using test device MAX62AA001 with the turbine running under load or noload conditions. To operate the test device, pilot valve KA03 is first pushed downwards and held in this position. This isolates the auxiliary trip medium circuit from the overspeed trips and prevents the main trip being initiated by the overspeed trips. Subsequent operation of hand-wheel KA01 moves the center pilot valve downwards. This action blocks the drain and allows the control oil to flow through the center bore of the pump shaft into overspeed trips. The control oil pressure thus builds up and moves the eccentric bolts/strikers outwards against the spring force, releasing the pawls of the overspeed trip releasing device, as a results of which the pilot valve moves rapidly inwards. The pressure in the auxiliary rip medium circuit, up to the over speed trip test device, then collapses. Operation is followed by observing the reading at pressure gauge MAX52CP501. The trip pressure is read off at pressure gauge MAX62CP501. If during operation at rated speed, this pressure should deviate from the baseline value as recorded in the test report, a defect in the overspeed trip may be assumed. If the trip pressure is too high, the bolt may be made to move freely by rapidly operating the pilot valve by means of hand-wheel KA01 several times in succession. If this measure does not have the desired result, the turbine must be shut down and the emergency governor to be inspected. As soon as the auxiliary trip medium pressure drops to 0 at pressure gauge MAX52CP501, the center pilot valve must be returned to its original position using hand-wheel KA01. The pressure in the test line should then return to 0, as can be read off at pressure gauge MAX62CP501. The bolts/strikers of the overspeed trips should return to their original position.

BHEL Hardwar

When this happened, pilot valve KA02 must be pushed downwards to admit control medium into the auxiliary start-up medium circuit to the differential pilot valve of the overspeed trip device. The pilot valve moves towards the right and latches the overspeed trip device in again. The buildup of pressure in the auxiliary startup medium circuit between the overseed trip test device and the overspeed trip release device can be followed at pressure gauge MAX48CP501. When pilot valve KA02 is then released, the auxiliary start-up medium pressure returns to 0 pressure. The auxiliary trip medium pressure must then remain at its full value (readable at pressure gauge MAX52CP501). If this is the case, pilot valve KA03 may be released. The test is completed. If, when valve KA02 is released, the auxiliary trip medium pressure collapses, pilot valve KA02 must be pushed downwards again and must be held in this position a little longer. It is essential that the auxiliary trip medium pressure must remain steady before valve KA03 is released. Testing with Turbine under No-Load Condition Overspeed trips MAY10AA001 and 002 must be tested at regular intervals by running the unloaded turbine up to trip speed. This is done by operating lever KA07 of hydraulic speed governor MAX46BY001, which presses linkage KA03 downwards, thus increasing the secondary medium pressures. This causes the control valves to open and the turbine starts to overspeed. The actual speed at which trip occurs can be read off at pressure gauge MAX44CP501. Limit switches MAY10CG001&002C of overspeed trip release device MAY10 AA001 and 002 indicate in the control room that main trip valves MAX51AA005 and MAX51AA006 have been actuated by overspeed protective device.

5.1-0631-01


Main Steam Stop Valves The stop valves can be tested for freedom of movement independently of each other even during operation with the aid of the test valves MAX47AA011 to 012 attached to each of them. The main stop valves MAA10 and 20AA001 may only be tested at a load that is less than 80% of the maximum output. If the test is conducted with the initial pressure controller out of operation, the main stop valves may only travel out of the open position to about 50% closed at the most and are to be reopened immediately. If the initial pressure controller is in operation complete closure of a main stop valve may be performed. This, however, is conditional upon the response time of the initial pressure controller being high enough to keep the initial pressure constant even during the testing procedure. First the main control valve concerned MAA10 or 20AA002, is to be closed by pressing of pushbutton in the supply unit. If in operation, the initial pressure controller opens the other main control valve accordingly. Once the control valve has been closed the stop valve can be closed. It is to be reopened immediately.

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Testing of Stop Valves

The main control valves may be closed for testing purposes for not longer than 4 to 5 minutes so that the unbalanced steam flow is only present for a short period to avoid significant effects on the HP turbine casing. It is a precondition for testing the main stop valves that there should be a mixing header in the steam leads between the boiler and the stop valves. Reheat Stop Valves Testing of a reheat stop valve must be conducted at a power output at which the reheat control valves MAB10 and 20 AA002 are fully open. First the associated reheat control valve is to be closed by pressing of pushbutton in the supply unit. Then the reheat stop valve MAB10 or 20 AA001 is closed by actuating test valve MAX47AA021 and 022 and reopened. On completion of the test the reheat control valve is to be reopened. As for the main steam stop valves it is a precondition for testing the reheat stop valves that there should be a mixing header in the steam leads between the boiler and the stop valves.

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Steam Turbine Description Function The function of the LP bypass control system is to monitor the pressure in the reheat system and to control it under certain operating conditions. During start-up and shutdown, and at operation below minimum boiler load, the volume of steam not utilized by the IP and LP cylinders of the turbine must be bypassed to the condenser via the LP bypass valves. This requires the bypass control system to maintain the pressure in the reheater constant in accordance with the preset reference value. In the event of disturbances, e.g. load shedding or trip out, the amount of excess reheat steam bypassed to the condenser depends on the capacity of the condenser. Mode of operation In the electro-hydraulic LP bypass control system, the electric controller governs a number of hydraulic actuators. The link between the electric controller and the hydraulic part of the control system is provided by the electro-hydraulic converter in the form of a jet pipe amplifier controlled by a plunger coil. In order to monitor the flow-dependent reheat pressure, irrespective of whether fixed-pressure or variable-pressure operation is used, the pressure before the HP drum blading, which is also flow

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Electro-hydraulic LP Bypass Control System (General) dependent, is used as the reference input for the electric controller. This variable reference value is replaced by a fixed reference value for certain operating sequences, such as start-up and shutdown. The controlled variable is the reheat pressure after the boiler outlet. The electric controller has a characteristic tailored to the pressure distribution within the turbine and monitors the reheat pressure. Monitoring is either a function of the reference input “Pressure before HP reaction blading” or a function of the fixed reference value under certain operating conditions. If the reheat pressure exceeds the reference value, the electric controller will act on the plunger coil of the electrohydraulic converter and initiate bypass operation. The bypass control system operates the combined LP bypass stop and control valves via various intermediate elements. This double shut-off arrangement separates the condenser from the reheater both during normal operation and when it can not accept any more bypass steam. The hydraulic part of the control system includes the necessary protective and safety devices for the condenser as well as the interlocks for the water side. See section: LP bypass control (hydraulic).

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Steam Turbine Description Measured Valve Acquisition Pressure transducers with bourdon tube movements measure the reheat pressure (controlled variable) and the pressure upstream of the HP balding (to form the reference variable). Set-point Formation Two set points, the fixed set point and the reference variable, are formed for the LP bypass controller, the effective set point under any set of operating conditions being the greater of the two, as selected by an auctioneer. The fixed set point can be set in the control room to any point between 0 and approximately 120% of the maximum LP bypass pressure with the aid of a motorized set point adjuster. It is normally used to set the lower limit for the pressure set point. The pressure upstream of the HP blading, required for reference variable formation, is measured by the dedicated pressure transducer and transmitted to a matching amplifier which sets the characteristic for the reference variable as a function of the pressure upstream of the HP blading. When both set points, fixed set point and reference variable, have been applied, they are compared in the auctioneer, the greater of the two being selected and taking effect in the controller. Provision is also made for limiting the reference variable to an adjustable level below the set pressure of the reheat safety valves. The actual value for reheat pressure is supplied by the pressure transducer as a proportion (between 0 and 120%) of the maximum LP bypass pressure. Pressure Controller The continuously acting electronic pressure controller consists of a DC amplifier and a power amplifier. The deviation is formed at the input to the DC amplifier by comparing the effective set point with the actual value. The pressure BHEL Hardwar

Electro-hydraulic Bypass Control (Electrical System) controller has a proportional integral (PI) characteristic. The power amplifier actuates the moving coil of the electro-hydraulic converter directly and through this, the LP bypass valves. There is a constant relationship between controller output voltage and valve position. If there is no voltage applied to the plunger coil, all LP bypass valves close. The LP bypass controller can be changed over to the manual mode from the automatic control mode using the controller ON/OFF push-button. It is then possible to actuate the valves directly using the open and close push buttons at the manual controller. This may be necessary in the event of defects in parts of the automatic system and is essential for testing valve actuator travel. The condenser protection device continues to be operative via the hydraulic LP bypass governor. Tracking Control In order to facilitate switching on and off of the automatic controller during operation, the control variable not taking effect in the controller (manual control voltage, or automatic controller output voltage, depending on the operating mode) is made to continuously follow up that effective in the controller. This function is performed by the tracking controller. When the automatic controller is effective, the manual controller is automatically made to follow up the automatic controller output voltage, the manual controller itself being inoperative. This permits the automatic controller to be switched off and the manual controller to take over operation at any time. When, on the other hand, the system is under manual control, the output voltage of the inoperative automatic controller is made to automatically follow up the manual control voltage. As long as the actual pressure value and the effective set point are identical, the changeover will be bumpless, if set point and actual value are not identical, the automatic controller will match the actual value to the set point on being switched on.

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Monitoring The electrical section of the electro-hydraulic LP bypass control is monitored for the following faults, which are annunciated at the control desk by means of the group alarms Fault in controller, Fault in automatic interface, Fault in reheat safety valve actuation circuit and Fault in condenser temperature protection system 1:

performed in the event of any of the faults listed under the group alarm Fault in controller, Items 1 to 6 above.

Fault in controller

This automatic charge-over to manual operation ensures, thanks to the tracking feature, that the valve position at the moment at which the above faults occur is retained. This prevents spurious automatic control actions and provides the operating personnel with sufficient time to intervene manually to avert operating disturbances.

1 Fault in power supply to controller 2 Insertion fault

Automatic Interface

3

Fault in power supply to transducer for measuring upstream of HP blading

pressure pressure

4

Fault in power supply to pressure transducer for measuring reheat pressure 5 Fault in power supply suppl y to Collins transmitters 6 Fault in power supply to binary signal conditioning section for solenoid valve for 2nd stage spray water.

The electro hydraulic LP bypass controller incorporates an automatic interface feature. In case of a cold or warm start-up, when reheat pressure is low, the fixed set point value is to be brought down to enable sufficient flow through reheater. This is done by switching on the auto control interface from the control desk. All command and alarm voltage signals are completely decoupled from other controller voltages.

Fault in automatic interface

Reheat Safety Valve Actuation Circuit.

1 Fault in power supply to automatic interface

The auxiliary control circuit for the reheat safety valves serves to prevent overheating of the reheater tubes by opening the safety valves, regardless of the reheat pressure, when there is insufficient flow through the reheater. The conditions at the reheater are reflected in the control deviation while the reheat flow is determined by the actual valve lift. Should the control deviation rise above a preset limit value without all stop valves being opened and before all control valves have attained a preset minimum lift, the reheat safety valves will be actuated to open after a short dead time of adjustable duration. The reheat safety valves can also be opened directly from the control desk. The limit switches on the stop and control valves are interrogated via input modules.

2 Insertion fault Fault in reheat safety valve actuation circuit

1 Fault in power supply to reheat safety valve actuator 2 Module fault Fault in condenser protection system 1

temperature

1 Module fault Automatic Change-over from Automatic to Manual Mode of Operation To increase operating reliability, automatic changeover to manual operation is

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Steam Turbine Description Description

Electro-hydraulic LP Bypass Control(Hydraulic Control(Hydraulic System)

Operation Electrical LP bypass controller MAN01 DP001 activities the plunger coil arranged on the left-hand side of transducer MAX53 BY001. In the event of voltage increases, jet pipe KA01 is swung to the right and piston KA08 of transducer MAX53BY001 is moved in the downward direction. This takes up a position proportional to the downward direction. This takes up a position proportional to the voltage change due to the rigid feedback. Sleeves KA04 of followup piston KA02 and KA03 connected to the piston are move in the downward direction and the fluid pressure in the follow-up pistons rises. At the beginning of the control process, injection valves MAN11and12AA003 and 004 by way of pilot valve MAX53 AA031+AA041 and the actuators to injection valve KA01 are opened first due to the rising pressure in follow-up piston KA03. The injection water reaches the pressure reducing orifice and is available for cooling down the bypass steam flowing into the condenser, with a slight delay compared to the injection valves, LP bypass stop valves MAN11and12 AA001 are fully opened as the fluid pressure in follow-up piston KA02 rises (assuming that the piston of the actuator to bypass limit controller KA07 is in the upper limit position) and following this, LP bypass control valves MAN11and12AA002 are opened taking up a defined position due to the feedback caused by the respective fluid pressure (proportional control action). LP bypass limit controller MAX53BY011 has priority over transducer MAX53 BY001. As soon as injection water is available at the required pressure and there is also a sufficiently high vacuum in condenser MAG10BC001, the jet pipe is swung to the right and the piston of the actuator to bypass limit controller KA07 moves into the upper limit position. As a result the pressure in follow-up piston KA02 is increased so that LP bypass stop and control valves MAN11and12AA001 and MAN11and12 AA002 are released for opening.

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If the vacuum in condenser MAG10BC001 drops or the pressure downstream of the LP bypass valves rises above the permissible value, or the pressure of the injection water is too low, the jet pipe of LP bypass limit controller MAX53 BY001 is moved to the left and the piston of the actuator to bypass limit controller KA07 moves downwards. In the bottom position of piston KA07, the spring of follow up piston KA02 is expanded to such an extent that the LP bypass valves are unable to open. By means of feedback to the measuring system “Pressure downstream of LP bypass valves” a certain piston setting and thus a certain setting of the LP bypass valves is allocated the each pressure deviation if the pressure allocated to the maximum permissible bypass rate is exceeded, thus limiting the bypass rate. This ensures that the volume limitation has a clear control behavior (Proportional control action). This feedback is only effective in volume limitation. It is not necessary for the other two limit pressures. To protect the reheater from the thermal damage as a result of heat accumulation, it must always have a minimum amount flowing through it. For this reason the reheater safety valves are actuated by the electro hydraulic LP bypass controller at a preset deviation. In normal bypass operation this signal is interlocked via limit switches MAN11and12 CG001D and MAN11and12 CG002B unless quick-closing LP bypass valves MAN11and 12AA001 are completely open and LP bypass control valves MAN11and12 AA002 are approx. 60% open. If only one valve fails to meet these conditions, the signal goes through and the safety valves open (thus they open at precisely the existing reheater pressure (below design pressure)). So that the safety valves do not respond unnecessarily as a result of delays present in the hydraulic control elements, the signal to them is passed via two parallel time delay relays which delay contact by approx. 5 sec.

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Second Low-Vacuum Trip A low-vacuum trip MAG01AA016 is installed in the signal line from follow-up piston KA02 to pilot valves KA02 and KA05 of the LP Bypass valves for the double protection of condenser MAG10BC001 during bypass operation. If the vacuum sinks below a preset valve during a fault in LP bypass limit controller MAX53 BY011, the pilot valve of low-vacuum trip MAG01 AA016 is moved in the downward direction from its upper limit position by the loaded spring. The pilot valve thus cuts off the signal line and simultaneously opens the drains so that signal fluid in the line between low-vacuum trip MAG01AA016 and pilot valves KA02 and KA05 is depressurized and the LP bypass valves close. As the vacuum increases again, bypass operation is released in the reverse sequence on attainment of the set limit value. Pressure Switch A spray water pressure switch MAN01AA011 in installed in the signal line from follow-up piston KA02 to pilot valves KA02 and KA05 of the LP bypass valves to protect condenser MAG10BC001 in the event that water injection fails. If the injection pressure drops below the adjustable value during a malfunction in LP bypass limit controller MAX53BY011, the pilot valve of the spray water pressure switch MAN01AA011 is moved from the upper limit position downwards. The pilot valve then cuts off the signal line and simultaneously opens the drains so that signal fluid in the line between pressure switch MAN01AA011 and pilot valves KA02 and KA05 is depressurized and the LP bypass valves close. As the injection pressure increases again. LP bypass operation is released in the reverse

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sequence when the preset limit value is reached. Solenoid Valves Thermocouples which transmit a switching pulse to associated solenoid valves MAX53 AA021and022 when a specified temperature is exceeded are fitted in the steam dome opposite the bypass steam inlet to protect condenser MAG10BC001. The solenoid valves shut off the signal fluid and at the same time open the drain so that the signal fluid in the line between solenoid spool valves MAX53AA021and 022 and pilot valves KA02 and KA05 of the LP bypass valves is depressurized and the LP bypass valves close. The LP bypass valves may only be opened manually from the control room when the temperature falls short of the limit value again. Staggered Water Injection In the present case, the entire maximum boiler steam flow is routed to the condenser. The injection water rate is staggered in two stages so that under normal start-up and shutdown conditions the condensate pumps do not have to supply the entire amount of injection water required for the full boiler flow and so that the excess water flow does not become too high. In this additional device, solenoid valve MAX53 AA051 is opened by way of pressure switch MAN01CP001 and injection valves MAN11and12 AA004 via pilot valves MAX53 AA041 when the steam pressure upstream of the pressure-reducing orifices exceeds a value allocated to an amount approx. 45% of the maximum bypass flow. This divides the injection water volume into two approximately equal quantities.


The function of extraction check valves LBQ50, LBS21, LBS31, LBS41 and LBS42 AA001and 002 is to prevent the backflow of steam into the turbine from the extraction lines and the feed water heaters. Two free-swinging check valves are installed in each extraction lines A2, A3, A4 and A5. In the event of flow reversal in the extraction lines, the valves close automatically, whereby actuator KA01 assists the closing movement of the disc. The mechanical design of the swing check valves is such that they are brought into the free -swinging position by means of trip fluid pressure via actuator KA01 and the disc is moved into the steam flow by means of spring force acting via the lever, shaft and disc lever and closes if differential pressure is either lowered or reversed. The trip supply to actuator KA01 is controlled by extraction valve relay MAX51 AA011, changeover valves MAX51AA028, MAX51AA031 etc. Extraction valve relay MAX51 AA011 actuates the swing check valves in accordance with the secondary fluid pressure, suitable adjustment of the spring in relation to piston KA02 sets the turbine load at which the swing check valves are released for opening or assisted in closing. The release setting for opening cannot be arbitrarily adjusted towards higher turbine output, as the swing check valve will open even without the release action if the steam pressure difference exerts a greater force than the closing spring.

Extraction Check Valve

there is a danger that the contents of the feed water heaters will flash into steam. In this case, closure of the swing check valves is assisted for a short time by means of pistons KA01 of auxiliary slide valve MAX51 AA011. In normal operation pilot valve KA01 passes trip oil to pilot valve KA02. In the event of an abrupt output drop, the pressure on the top side of pilot valve KA01 drops, where as depressurization beneath the piston is delayed by a check valve and the pressure in fluid accumulator MAX45BB001. The resulting differential pressure moves the piston upward to interrupt the trip fluid supply to the swing check valves, whose closing movement is assisted by the spring force of actuator via a flow restrictor. The pilot valve moves back into its original position to open the way for the trip fluid to release the swing check valves. Turning the handwheel on the changeover valves MAX51AA048, MAX51AA051 etc. close the associated swing check valves within the bounds of the effectiveness of the spring. The swing check valve in extraction lines A4 can also be triggered by differential pressure switch LBS42CP002. This differential pressure switches energizes solenoid valves MAX51AA028 and MAX51AA031 if the steam flow drops below a preset rate (differential pressure), thereby further assisting the closing action of the swing check valve. The position of all swing check valves is indicated via position transmitters-CG001A and CG002A.

In the event of major output drops above the opening point of the swing check valves,

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5.1-0650-01

Steam Turbine Description In order that the turbine may be completely separated from the steam when it is stationary, an additional check valve LBC10 AA001 is fitted in the line between the HP cylinder and the reheater and operating through pilot valve MAX42AA001 +002 and the rotary actuator KA01 depending on the pressure in the associated secondary medium circuit. The swing check valve opens fully when the control valves reached approx. 5 to 10% of their full-power travel. Only when the control valves reach this point again as they are being closed, the swing check valve brought into steam flow again by the hydraulic actuator. Thus when the steam flow in the normal direction ceases, the

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Swing Check Valve Cold reheat steam line check valve is closed by the actuator KA01 and prevent the steam in the cold reheat line from returning to the turbine. By removing the valve from the steam flow during operation above 5 to 10% of maximum power, additional pressure losses during normal operation are avoided. If, during start-up, the steam pressure on the inlet side of the valve and at the same time the secondary medium pressure is not yet sufficient to open the valve, the steam pressure will open the swing check valve against the medium pressure in the manner of a safety valve. The Open and Control Control position of the swing check valve are indicated in the control room via the limit switches.

5.1-0651-01


The check valve LBC10AA001 in cold reheat line is wide open during normal operation by its associated rotary servomotor KA01. For testing the movability, the check valve can be moved in closing direction by interrupting the connection between pilot valve MAX42 AA002 and HP secondary fluid line with closing of shut-off valve MAX45AA566 (pilot valve and shut-off valve are installed in the turbine hydraulic control rack). By closing the shut-off valve the pilot valve MAX42AA002 is reversing and rotary servomotor is moving the check valves in closing direction. Because the torque of these servomotor is limited, the check valves can not be closed completely. This

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Testing of Check Valves in Cold Reheat Line can be brought only in an intermediate position. When the check valve starts moving, the open position limit switch will change position, which is indicated in the control room. With this indicator the regular movement of the check valve can be checked after closing shut-off valve MAX45AA566 nearby upto this value. After this check the shut-off valve has to be reopened. The check valve is moved then in its wide-open position. At the position indicator in the control room it can be checked if the check valve has reached again its wide-open position.

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Automatic Turbine Tester General

Function Healthiness of the protective devices and the stop and control valves is vitally important for the operational reliability and availability of the turbine. Hence, it is essential that these equipments are always kept in a fully serviceable condition. Economy has dictated longer intervals between turbine overhauls, with the result that testing of the equipments and devices is now necessary at regular intervals during normal operation. There are manually operated devices for testing the free operation of the stop and control valves. However, these tests do not cover all components involved in an automatic trip with the result that the conditions only party corresponds to those prevailing during a real trip. The system Any possible mal-operation associated with manually operated devices are avoided with fully automatic tests by means of the automatic turbine tester. Full protection for the turbine during testing is also assured by suitable circuit arrangements. This increases the operational reliability and availability of the plant. The automatic turbine tester is realised in digital technology. System adaptation The system is subdivided into functional groups for each device. Each group contains the device itself and all necessary transmission elements for initiation of a normal trip. The automatic turbine tester is divided into the following 2 subgroups:

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1. Protective devices Description: “Automatic Tester, Protective device”.

Turbine

2. Main stop and control valves Description: “Automatic Turbine tester, stop and control valves”. The complete testing of all components which must operate when an automatic trip becomes necessary is assured, despite the subdivision into two testing groups (protective devices, stop and control valves), because the main trip valves which store the trip signal by mechanical hydraulic means are operated together with each protective device and subsequent satisfactory reduction of the trip oil pressure after the valves are monitored. Nature of the description The descriptions mentioned above contain the practical sequence of the tests on the individual devices and gives details of possible irregularities. The description of equipment contained in the automatic control cubicle (stepping switches, interlock modules, etc), the control panel in the control room and schematic circuit diagrams are contained in the separate electrical section of the “Operating “ Operating Manual ” for the automatic turbine tester. For the understanding of the automatic turbine tester from these descriptions it is assumed that the reader is fully conversant with the functioning of the individual protective devices and valves within the overall turbine governing and protection system.

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Automatic Turbine Tester for Protective Device

Scope of Testing The Automatic turbine tester (ATT) subgroup for the protective devices is divided into a preliminary test and the following four individual testing systems. 

Remote trip solenoid MAX52AA001



Remote trip solenoid MAX52AA002





Over speed trips MAY10AA001/MAY10 AA002 Low vacuum trip MAG01AA011

One or more systems can be selected for testing at the control panel and the selection is stored. The start of the test program automatically causes a preliminary test to be carried out on the protective channels which are to be effective during actual testing and then establishes the test circuit. Once the first test selected has been completed and the protective device has latched in again, the test circuit is restored to its normal operational configuration. Further selected tests must be started individually by pressing the Test push-button to start the program. General During normal operation, the protective devices act via main trip valves MAX51 AA005 and MAX 51AA006 on the stop and control valves and extraction swing check valves. The remote trip solenoids MAX52 AA001 and MAX52 AA002, over speed trips MAY10AA001/MAY10AA002 and low vacuum trip MAG01AA011 actuate main trip valves MAX51AA005 and MAX51AA006 by opening the auxiliary trip fluid circuit. For the duration of testing of the protective devices, a test circuit is established .In order to keep the trip fluid circuit effective, it is isolated from main trip valves MAX51 AA005 and MAX51AA006 by means of change-over valve MAX51AA211 and supplied with fluid via solenoid valves MAX51AA201 and MAX51AA202 (remote trip during testing ). ).

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Trip Initiation during Testing To provide normal protection for the turbine during testing, any trip initiation signals from the protective devices will de-energize the solenoid valves for remote trip during testing and the same time initiate the reset program. This also applies to all normal electrical remote trips such as generator protection, etc. For the duration of testing, two electrical speed signals are formed to provide protection against turbine overspend. During all electrical testing of the protective devices, the electric trip action is prevented however, all annunciations are activated as for actual trip. The appropriate section of the alarm annunciation system is thus also tested. Features of the Automatic Turbine Tester The automatic turbine tester is distinguished by the following features: 



Individual testing protective device.

of

each

turbine

Automatic testing, testing, upon selection of a test, of the devices that protect the turbine during that test. Testing of the protective devices for normal turbine operation can only be performed if the preliminary test has run without fault and the protection of the turbine during testing is assured.

Monitoring of all program steps for execution within a certain time.









Interruption if the running time of any program step is exceeded or if trip is initiated. Automatic reset of the test program program after after a fault. Protection of the turbine turbine during testing provided by special test protective devices.

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Setting Data

Individual Tests

The setting data for the pressure switches are listed in the setting record Measuring Point List . The actually set values are logged in the Commissioning Test Record.The test running times, etc. are entered in the functional diagrams.

The individual test is performed after completion of the preliminary test and after the test circuit has been established.

Test Sequence Start of Testing The test begins with the selection of the protective devices subgroup. This is performed by pressing the subgroup On/Off push button. The subgroup remains on until switched off when the program has been completed. While the protective devices subgroup program is running, the other subgroups are blocked. The On/Off push-button is also used to acknowledge alarms.

Successful completion of each individual test is annunciated by the limit switches on main trip valves MAX51AA005 and MAX51 AA006, pressure switch MAX52CP211 in the auxiliary trip fluid circuit and pressure switch MAX 51CP209 in the trip fluid circuit between change-over valve MAX51AA211 and the main trip valve MAX51AA006. The associated limit switch also annunciates when a protective device (except for the remote trip solenoids) has been activated. On completion of each individual test, all activated protective devices are returned to their normal operating position by reset solenoid valves MAX48AA201 and MAX48 AA202 and the test circuit is deactivated. Whenever several of the same types of protective device are provided, only one will be described in the following, as the test procedure is the same for all.

Selection After the subgroup has been switched on, the protective device to be tested is selected by pressing the selection push button for the individual device. A separate selection push-button is provided for each protective device. Only one selection may be made at a time. Selection of a further test is possible only once all other programs have ended Test Push-Button The automatic test program is started by pressing the Test push-button push-button Cancel Push-Button This push-button can be used to terminate the test program running at any time and to initiate the reset program. The reset program has priority over the test program. Lamp Test Push-Button All the signal lamps on the control panel can be tested by pressing the Lamp Test PushButton.

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Preliminary Test Pressing the Test push-button push-button automatically initiates a test of the protective circuits to be effective during testing. Function The function of the preliminary test is to detect any faults in the protective circuits to be used during testing, and, if any are detected, to inhibit testing of the protective device, as this would leave the turbine without protection. Test Sequence In the course of the preliminary test, solenoid valves MAX51AA201 and MAX51 AA202 (remote trip during testing) are automatically tested before the test circuit is established. These valves (MAX51AA201 and MAX51AA202) are first energized, resulting in a buildup of control fluid upstream of changeover valve MAX51AA 211.lnitiation of Schmitt triggers (in the speed measuring unit) de-energizes solenoid valve MAX51AA201 and the control

fluid up stream of changeover valve MAX51 AA211 is drained. Successful completion of testing is annunciated by pressure switch MAX51CP207 between solenoid valve MAX 51AA201 and changeover valve MAX51AA 211. Subsequently, solenoid valve MAX51 AA202 is de-energized via the second channel of its Schmitt trigger, thereby depressurizing the control fluid still present between solenoid valves MAX51AA201 and MAX51AA202. This process is monitored by pressure switch MAX51CP205. On successful completion of the preliminary test, the test circuit is automatically established, which permits realistic testing of the protective devices without initiating turbine trip. Solenoid valves MAX51AA201 and MAX51 AA202 (for remote trip during testing) are again energized whereupon control fluid is supplied to change over valve MAX51 AA211. Then solenoid valve MAX61AA201 is energized, effecting changeover from trip fluid to control fluid. The control fluid in this line drains off, and the pressure difference drives changeover valve MAX51AA211 into its test position (lower end position), thereby

actuating limit switch MAX51CG211C which annunciates this status. De-activating the Test Circuit The test circuit is deactivated in the reverse order on completion of the selected test and after automatic latching of the protective device concerned in its normal operating position. Hydraulic Test Signal Transmitters The function of the hydraulic test signal transmitters is to activate the related protective device (with the exception of the remote trip solenoids). Each protective device has an associated test signal transmitter. For testing the over speed trip device, the associated test signal transmitter builds up a test pressure relatively slowly and passes it to the overspeed trips, for testing the low vacuum trip, an air pressure signal is introduced to the device via an orifice. The testing signals to remote trip solenoids MAX52AA001 and MAX52AA002

are formed within the automatic turbine tester itself and not by a test signal transmitter.

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Main Trip Valves MAX 51 AA005 and MAX 51 AA006 Only one of the two main trip valves is described in the following, as they are constructional and functionally identical.

Function The function of the main trip valve is to amplify and store the hydraulic or mechanical (manually initiated local) trip signal. It must respond in the course of every successful protective device test. Operation Each main trip valve is kept in its position by auxiliary trip fluid pressure. If a protective device is actuated, the auxiliary trip fluid circuit is depressurized and the main trip valve is activated. This connects the trip fluid and auxiliary trip circuits to drain and shuts

off the control fluid supply to the turbine valves. At the same time, limit switch 1 is actuated. Auxiliary start-up fluid pressure forces differential piston (3) into its normal operating position. Control fluid IV is then free to pass through to buildup the pressure in the trip fluid and auxiliary trip fluid circuits.

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Pressure switches MAX48CP201 and MAX48CP202 monitor the orderly pressure collapse of auxiliary start-up fluid circuit after latching-in of main trip valves. Attention: The lever for manual actuation of the main trip valve must not be test operated during turbine automatic testing operation, as the electrical trip action is always initiated via the manual trip-out limit switch. Remote Trip Solenoids MAX52 AA001 and MAX52 AA002 The twin electrical remote trip feature consists of the two remote trip solenoid valves MAX52AA001 and MAX52AA002. 0ne trip channel is described here, as the test procedure is the same for both. Function The function of the remote trip solenoids is to depressurize the auxiliary trip fluid circuit in the shortest possible time, thereby bringing main trip valves MAX51AA005 and MAX51AA006 into their trip positions, in the

event of a malfunction requiring electrical trip initiation. During normal operation, the remote trip solenoid isolates the auxiliary trip fluid circuit from the drain. For testing, the automatic turbine tester switches over the

500MW Turbine O&M Manual Part_1of3[1]

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