CO2 EE-00100-CO2-002

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QURAYYAH COMBINED CYCLE PLANT

Sargent Sargent & Lundy Lun dy LLC

SYSTEM DESCRIPTION DOCUMENT NO. EE-00100-CO2

DOCUMENT NO. EE-00100-CO2 QURAYYAH COMBINED CYCLE PLANT CARBON DIOXIDE DIOXIDE SYSTEM DESCRIPTION DESCRIPTION

Revision 000 001 002

Date 14 May 10 21 Sep 10 25 Apr 11

Purpose Issued For Approval Issued For Approval Issued For Approval

Prepared AJM AJM AJM

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Reviewed KB KB KB

Approved PMK PMK SSG

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1.

CARBON DIOXIDE SYSTEM

1.1

System Function


The carbon dioxide system is required to supply carbon dioxide for the purging of air and hydrogen from the main generators prior to the filling of hydrogen and subsequent shutdown respectively. The Generator has a large open volume internally. This volume contains hydrogen during normal operation. It contains air during maintenance outages. An inert gas is put into the generator volume as an intermediate gas so that air and hydrogen do not mix inside the generator casing. Carbon dioxide gas is used as the inert gas because it has a substantially higher density and lower thermal conductivity compared to hydrogen or air. For detailed P&ID of Carbon dioxide (CO2 ) System refer to Dwg. No. EA-682813.

1.2

General Description General

Purging of generator is carried out to remove the hydrogen gas prior to a maintenance activity. This results in effective inerting the generator. Prior to personnel working inside the generator, the CO2 gas must be purged with instrument air. The second instance a CO2 purge is performed after the generator has been opened up and maintenance has been completed. In this case CO2 is used to purge the generator cavity of air prior to refilling with hydrogen gas. The substantially different properties are used by the gas analyzer (inside the hydrogen cabinet) so that gas concentration during purging can be monitored. The carbon dioxide is supplied from a centralized carbon dioxide storage where carbon dioxide gas is stored in dip tube type cylinder. Open cycle loose carbon dioxide cylinder that are located in CO 2 & N2 shelter of Project-B (Item no# 42 in site layout) will be relocated in centralized carbon dioxide gas storage shelter (Item#233 in Site layout) of Project-C. CO2 gas from centralized storage is supplied to both open cycle and combined cycle generators for purging. Combined Cycle carbon dioxide cylinder manifolds are arranged in five groups with each group having dual redundant headers to facilitate removal and replacement of cylinders on one manifold whilst the other manifold is in use. CO2 cylinder are kept in racks with each rack consisting of 16 cylinders. Open Cycle carbon dioxide bottles are also kept in racks with each rack consisting of 16 cylinders. Open cycle carbon dioxide dioxide cylinder manifolds manifolds are arranged in ten (10) groups groups with each group having dual redundant headers to facilitate removal and replacement of cylinders on one manifold whilst the other manifold is in use, similar to combined cycle.

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The redundant header of each rack is connected to redundant main header (C00-025QJK-011-Q0605,C00-025-QJK-012-Q0605) and these redundant main headers are connected to redundant streams each of them provided with a waterbath heater (C00QJK-50-AC-001/002).Downstream QJK-50-AC-001/002).Downstream of waterbath waterbath heater, heater, redundant redundant central central pressure reduction station (CPRS) (C00-QJK-50-AA-081/082) are provided. From CPRS, CO2 gas is supplied to STG area pressure reducing stations (two STG STG PRS - one (C00-QJK-50AA-084) for STG block#1,2,3 and other (C00-QJK-50-AA-083) for STG block 4,5 & 6 (future)) from where CO2 is supplied to Generator Gas Control Station of individual steam turbine generators at required pressure.

002

A low pressure side interconnection is provided from combined cycle header to open cycle enabling supply of CO 2 gas supply to Open cycle Gas turbines. Interconnection is provided from downstream of central pressure reducing station (CPRS) and extended to GTG area. Pressure reducing stations (PRS) (C10/20/30/40/50-QJK-50-AA-081) are provided at GTG area (One PRS for each block GTGs) to supply CO2 gas to generator at required pressure. Each GTG area PRS has one orifice in bypass header .A spool pipe with a NRV is added at low pressure side of open cycle CO2 piping. before flow transmitter on pipeline connecting to GE terminal point LE002. QCPP interconnection pipe is connected to this spool pipe (after NRV). At each main header header a safety relief valve (C00-WJK-50-AA-195/ (C00-WJK-50-AA-195/196) 196) is provided provided to protect the system from overpressure. Carbon dioxide system consist of following major components /equipments /equipments •

•

•

•

•

•

Five (5) banks of QCCPP Carbon dioxide dip tube type cylinder for generator purging. Each bank consists of 40 cylinders. Two (2 x 100%) capacity waterbath heaters (C00-QJK-50-AC-001/ (C00-QJK-50-AC-001/002) 002) One (1) redundant pressure reducing stream (C00-QJK-50-AA-081/082) to supply carbon dioxide gas to the generator terminal point at the pressure required for STG / GTG. Two (2) redundant pressure reducing station (C00-QJK-50-AA-083/084) for STG area is provided to supply CO 2 to STG at required pressure. Each pressure reducing stream is having orifice (C00-QJK-50-BP-001/002 respectively) in bypass header. Five (5) Pressure Reducing station (C10/20/30/40/50-QJK-50-AA-081), one (1) for each block GTGs is provided to supply CO 2 to GTG at required Pressure. Each pressure reducing stream is having orifice (C10/20/30/40/50-QJK-50-BP001 respectively). Ten (10) banks of QCCPP Carbon dioxide dip tube type cylinder for generator purging. Nine (9) banks consist of 40 cylinders and One(1) bank consists of 30 cylinders.

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002

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1.2.1


Carbon dioxide cylinder and storage racks Carbon dioxide cylinders of dip tube type will be stored in a storage rack. The cylinders are segregated in storage rack separately for STG purging & open cycle purging. Number of carbon dioxide cylinder is estimated considering three (3) air and three (3) hydrogen purging for each of the five (5) steam turbine generators. Additionally 5% margin is provided to cover leakages. Total 200 cylinders (40 per block) in are kept at central CO2 storage in racks consisting of 16 cylinders each. Total 390 Open cycle cylinders are relocated to central CO2 storage and are kept in racks of 16 cylinders each Number of QCPP cylinder cylinder racks - 13 Number of OCPP cylinder cylinder racks - 25 Carbon dioxide gas will be supplied from centralized storage shelter (item#233 in Site layout) with dual manifold arrangement to facilitate removal and replacement of cylinders on one manifold whilst the other manifold is in use.

1.2.2

Electrically heated waterbath type evaporators (C00-QJK-50-AC-001/002) with temperature gauges, alarms, thermostats and water level gauges.

1.2.3

Central Pressure reducing station, consisting of one self regulating pressure reducing valve (in each header) reduces the carbon dioxide gas pressure to required pressure suitable for distribution to the generator.

1.2.4

STG and GTG area pressure reducing station consist of one self regulating pressure reducing valve which reduces pressure to required pressure suitable for distribution to the generator. A ball valve along with orifice is provided in bypass line. Carbon dioxide gas is supplied from storage at 74 barg and pressure is reduced to 11 barg at central pressure reduction stage. Further pressure is reduced to 8.62 barg (required pressure at Generator) at STG and GTG area PRV stations.

1.2.5

Relief valves are located downstream of pressure-regulating pressure-regulating valves to protect protect the system from overpressure. Vents of relief valve will be routed to safe height approximately 1 m above the building/facility. building/facility.

1.2.6

Piping is designed per ANSI/ASME B31.1, Power Piping.

1.2.7

Generator purging requirement and interconnecting piping between STG modules are as per STG Supplier recommendations. recommendations. Low pressure side interconnection is provided between combined cycle and open cycle.

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pipe sizing of pipe line up to interconnection junction point is sized considering six(6) generator (5 STG+1GTG) simultaneously at any point of time. CO2 Consumption data Total Carbon Dioxide (CO2) gas required for air and hydrogen purge for each generator (at STP condition)

3

247 m

The carbon dioxide gas is stored in cylinder at central storage area. From the storage unit, CO2 will be supplied to combined cycle steam generator terminal point and open cycle CO2 gas supply low pressure side (interconnection junction) at 8.62 barg. See GE’s product literature (Attachment 1.11.2) for details of carbon dioxide operating pressure range for each generator design.

1.3

System Operation Normal Operation

The operation of the system is manual and as required by the generator manufacturer’s operating instructions. Carbon dioxide gas flows from the centralized bulk storage through watebath heater and Pressure reducing station (PRS) for distribution to respective generators at required pressure, i.e., 8.62 barg One local control panel will be supplied by Vendor for operation, control and monitoring of waterbath heaters.

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Abnormal Operation

In case CO2 Gas is being supplied supplied from bottles and sufficient pressure is not available downstream of CPRS, low pressure alarm is provided. In case CO2 Gas is is being supplied supplied from bottles bottles and high pressure is available available downstream of CPRS, High pressure alarm is provided. In case CO2 Gas is being supplied supplied from bottles and sufficient pressure is not available downstream of STG pressure reducing station, low pressure alarm is provided. In case CO2 Gas is is being supplied supplied from bottles bottles and high pressure is available available downstream of STG pressure reducing station,high station,high pressure pressure alarm is provided. In case CO2 Gas is being supplied supplied from bottles and and sufficient pressure is is not available at open cycle supply header, low pressure alarm is provided. In case CO2 Gas is is being supplied supplied from bottles bottles and high pressure is available available at open cycle supply header, High pressure alarm is provided. High and low temperature alarm provision is provided at downstream of CPRS. Start-up Operation

None Shutdown Operation

None

1.4

Interlock & Protection:

None

1.5

Major Controls

None

1.6

Instrumentation Description Instrumentation & Measurement Process

Pressure Transmitter (C00-QJK-50-CP-013/014) at main header in CO 2 shelter, is provided for indication of header pressure in the DCS . Pressure Transmitter (C00-QJK-50-CP-001) downstream of waterbath heater and upstream of CPRS, is provided for indication of header pressure in the DCS .

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Pressure Transmitter (C00-QJK-50-CP-007) downstream of CPRS, is provided for indication of header pressure in the DCS and high pressure alarm and low pressure alarm in the DCS. Pressure Transmitter (C00-QJK-50-CP-010) downstream of CPRS at interconnection header, is provided for indication of header pressure in the DCS and high pressure alarm and low pressure alarm in the DCS. Pressure Transmitter (C00-QJK-50-CP-011/012) downstream of STG PRS, is provided for indication of STG supply header pressure in the DCS and high and low pressure alarm in the DCS. Temperature Element (C00-QJK-50-CT-004) downstream of CPRS, is provided for indication in the DCS and high and low temperature alarm in the DCS. Temperature indicator (C00-QJK-50-CT-502) downstream of CPRS is provided Local Pressure Gauges (C00-QJK-50-CP-508, C00-QJK-50-CP-509) at redundant main header (C00-025-QJK-012/011-Q0605 (C00-025-QJK-012/011-Q0605 respectively) Local Pressure Gauges (C00-QJK-50-CP-502, C00-QJK-50-CP-505) upstream of PRVA, PRV-B respectively are provided. Local Pressure Gauges (C00-QJK-50-CP-503, C00-QJK-50-CP-506) downstream of PRV-A, PRV-B respectively are provided. Local Pressure Gauges (C11-QJK-50-CP-501) at interconnection to OCPP CO 2 system low pressure side for generator -1 of block-1 Local Pressure Gauges (C12-QJK-50-CP-501) at interconnection to OCPP CO 2 system low pressure side for generator -2 of block-1 Local Pressure Gauges (C13-QJK-50-CP-501) at interconnection to OCPP CO 2 system low pressure side for generator -3 of block-1 Local Pressure Gauges (C21-QJK-50-CP-501) at interconnection to OCPP CO 2 system low pressure side for generator -1 of block-2 Local Pressure Gauges (C22-QJK-50-CP-501) at interconnection to OCPP CO 2 system low pressure side for generator -2 of block-2 Local Pressure Gauges (C23-QJK-50-CP-501) (C23-QJK-50-CP-501) at interconnection interconnection to OCPP CO2 system low pressure side for generator -3 of block-2 Local Pressure Gauges (C31-QJK-50-CP-501) (C31-QJK-50-CP-501) at interconnection interconnection to OCPP CO2 system low pressure side for generator -1 of block-3 Local Pressure Gauges (C32-QJK-50-CP-501) (C32-QJK-50-CP-501) at interconnection interconnection to OCPP CO2 system

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low pressure side for generator -2 of block-3 Local Pressure Gauges (C33-QJK-50-CP-501) (C33-QJK-50-CP-501) at interconnection interconnection to OCPP CO2 system low pressure side for generator -3 of block-3 Local Pressure Gauges (C41-QJK-50-CP-501) (C41-QJK-50-CP-501) at interconnection interconnection to OCPP CO2 system low pressure side for generator -1 of block-4 Local Pressure Gauges (C42-QJK-50-CP-501) (C42-QJK-50-CP-501) at interconnection interconnection to OCPP CO2 system low pressure side for generator -2 of block-4 Local Pressure Gauges (C43-QJK-50-CP-501) (C43-QJK-50-CP-501) at interconnection interconnection to OCPP CO2 system low pressure side for generator -3 of block-4 Local Pressure Gauges (C51-QJK-50-CP-501) (C51-QJK-50-CP-501) at interconnection interconnection to OCPP CO2 system low pressure side for generator -1 of block-5 Local Pressure Gauges (C52-QJK-50-CP-501) (C52-QJK-50-CP-501) at interconnection interconnection to OCPP CO2 system low pressure side for generator -2 of block-5 Local Pressure Gauges (C53-QJK-50-CP-501) (C53-QJK-50-CP-501) at interconnection interconnection to OCPP CO2 system low pressure side for generator -3 of block-5 Valves

Self regulating Pressure Reduction valves (C00-QJK-50-AA-081 and C00-QJK-50-AA082) at central pressure reducing station to reduce the downstream pressure to 11 bar(g). Self regulating Pressure Reduction valves (C00-QJK-50-AA-083 and C00-QJK-50-AA084) at STG area pressure reducing station station to reduce the downstream pressure to 8.62 bar(g). Self regulating Pressure Reduction valves (C10-QJK-50-AA-081,C20-QJK-50-AA(C10-QJK-50-AA-081,C20-QJK-50-AA082,C30-QJK-50-AA-083,C40-QJK-50-AA-084,C50-QJK-50-AA-085) at GTG area pressure reducing station to reduce the downstream pressure to 8.62 bar(g).

1.7

Design operating parameters

Design pressure & Design Temperature of Carbon Dioxide system piping is as follows, Description

Design Pressure (barg)

From Centralized Carbon Dioxide storage to waterbath heater From waterbath heater to centralized storage.

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88.8

Design Temperature (Deg C) 60

PDT

QCC 0605

85.50

60

QCC 0605

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Description

Design Pressure (barg)

From Centralized Carbon Dioxide storage STG Pressure reducing station From STG Pressure Reducing Station to Generator Terminal Point From Centralized Carbon Dioxide storage GTG Pressure reducing station From GTG Pressure Reducing Station to OCPP low pressure side

1.8

13.20

Design Temperature (Deg C) 60

PDT

QCC 0105

10.344

60

QCC 0105

13.20

60

QCC 0105

10.344

60

QCC 0105

Technical Particulars For Generator purging Item No 1.

2. 3. 4. 5. 6. 7.

Units

Description

Number of CO2 cylinders per generator Number of generator Total number of CO2 cylinders for generators Capacity of CO2 dip tube type cylinder Useable CO2 within dip tube type cylinder (80%) Gas pressure in CO2 dip tube type cylinder Design temperature

Particulars

Number

40

Number Number

5 200

Kg

45

kg

36.29

barg

74

Dec C

50

Waterbath Heaters Item No 1. 2. 3.

Units

Description

Number of waterbath heaters Flow Capacity of waterbath heater Maximum operating Temperature of

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Number Scfm Deg C

Particulars

2 720 57.22

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4.

1.9


carbon dioxide gas at the outlet of waterbath heater Pressure Drop across waterbath heater

Bar

2.5

Standards

The standards listed below are the design codes used for design and construction of the Industrial gases system. American National Standards Institute (ANSI) ANSI/ASME B31.1 ANSI B16.5 ANSI B16.9 ANSI B16.11 ANSI B16.34 ANSI B36.10

Power Piping Pipe Flanges and Flanged Fittings Factory Made Wrought Steel Butt welding Fittings Forged Fittings, Socket Welded and Threaded Valves Flanged, Threaded, and Welding End Welded and Seamless Wrought Steel Pipe

American Society for Testing Materials (ASTM) ASTM A105 ASTM A106 ASTM A216

1.10

Drawings

EA-682813 EE-00045 EE-00037B EA-682700 EA-682909 GEK 103763d 357A2258 EE-01655 ED-680427

1.11

Forgings, Carbon Steel, for Piping Components Seamless Carbon Steel Pipe for High Temperature Service Steel Castings, Carbon Suitable for Fusion Welding for High Temperature Service

Piping & Instrumentation Diagram – Carbon Dioxide System Calculation for Carbon dioxide Plant Capacity Pipe Sizing Calculation for Carbon dioxide System General Arrangement Site Development General Arrangement STG CO2 Shelter Hydrogen and Carbon dioxide Control System for Non Packaged Units Generator Gas System Installation Design Specification Generator P&ID CO2 system logics

Attachment

1.11.1 Chemtron High Pressure CO2 purging system Drawing D54946 1.11.2 GEK 103763d - Hydrogen and Carbon dioxide Control System for Non Packaged Units.

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A t t a c h m e n t 1 .1 1 .1

L I n o t w e r P c o r e n s n s e u c r t i e o S n i o f d e r m

C

30621127-000-3BD-EE-00100-CO2 REV 002

ATTACHMENT 1.11.2

GEK 103763d Revised August 2008

GE Energy

Hydrogen and Carbon Dioxide Gas Control System for Non Packaged Units Operation Operation and Maintenance Maintenance Instructions Instructions

These instructions do not purport to cover all details or variations in equipment nor to provide for every possible contingency to be met in connection with installation, operation or maintenance. Should further information be desired or should particular problems arise which are not covered suf ¿ c ¿ciently iently for the purchaser’s purposes the matter should be referred to the GE Company. © General Electric Company, 2008. GE Proprietary Information. All Rights Reserved. 13 of 56

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GEK 103763d

Hydrogen and Carbon Dioxide Gas Control System for Non Packaged Units

The below will be found througho throughout ut this publication publication.. It is important important that the signi¿cance signi¿cance of each is thoroughly thoroughly understood by those using this document. The de¿nitions are as follows: NOTE

Highlights an essential element of a procedure to assure correctness. CAUTION

Indicates a potentially hazardous situation, which, if not avoided, could result in minor or moderate injury or equipment damage.

WARNING INDI INDICA CATE TES S A POTE POTENT NTIA IALL LLY Y HAZA HAZARD RDOU OUS S SITUA SITUATIO TION, N, WHICH, WHICH, IF NOT AVOIDED VOIDED,, COULD COULD RESUL RESULT T IN DEATH DEATH OR SERIOUS INJURY

***DANGER*** INDICA INDICATES TES AN IMMINENT IMMINENTL LY HAZARDO HAZARDOUS US SITUASITUATION, TION, WH WHICH ICH,, IF NOT AVOIDE VOIDED D WILL WILL RESUL RESULT T IN DEATH OR SERIOUS INJURY.

2

© General Electric Company, 2008. GE Proprietary Information. All Rights Reserved. 14 of 56

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GEK 103763d

TABLE OF CONTENTS

............ ....... ....... ........ ....... ....... ........ ........ ........ ....... ....... ........ ....... ....... ....... ....... ........ ........ ........ ........ ....... ....... ....... ....... ........ ........ .... I. GENERAL GENERAL DESCRIPTI DESCRIPTION ON ........ A. Why Hydrog Hydrogen....... en........... ........ ........ ........ ........ ........ ........ ........ ....... ....... ....... ....... ........ ........ ........ ........ ....... ....... ....... ....... ........ ........ ........ ........ ....... ....... ....... ....... ........ ........ .... B. Explos Explosion ion Hazard...... Hazard......... ....... ........ ........ ........ ........ ....... ....... ....... ....... ........ ....... ....... ........ ........ ........ ....... ....... ........ ....... ....... ....... ....... ........ ........ ........ ........ ....... ....... ....... ... C. Inert Inert Interme Intermedia diate te Gas....... Gas........... ........ ........ ........ ........ ........ ........ ....... ....... ........ ....... ....... ........ ........ ........ ....... ....... ........ ....... ....... ....... ....... ........ ........ ........ ........ ........ .... D. Essent Essential ial Parts Parts of the Gas Contro Controll System..... System......... ....... ....... ....... ....... ........ ....... ....... ....... ....... ........ ....... ....... ....... ....... ........ ........ ........ ........ ....... ..... E. Gas Storag Storagee ........ ............ ........ ........ ........ ........ ........ ....... ....... ........ ........ ........ ....... ....... ........ ....... ....... ........ ........ ........ ....... ....... ........ ....... ....... ....... ....... ........ ........ ........ ........ ........ .... F. Gas Valve alve Statio Station n ....... ........... ....... ....... ........ ........ ........ ....... ....... ........ ....... ....... ....... ....... ........ ........ ........ ........ ....... ....... ....... ....... ........ ........ ........ ........ ....... ....... ....... ....... ...... ..

5 5 5 5 5 8 8

II. WARNINGS CONCERNING CONCERNING THE USE OF HYDROGEN HYDROGEN..... ........ ..... ..... ...... ...... ...... ..... ..... ..... ..... ...... ...... ..... ..... ...... ...... ...... ..... .. A. Genera Generall Rules Rules for Safe Safe Handli Handling ng of Hydrog Hydrogen en ........ ........... ....... ....... ....... ........ ........ ........ ........ ....... ....... ....... ....... ........ ........ ........ ........ ....... ..... B. Unknow Unknown n Contam Contamina inant nt is Assume Assumed d to be Air.... Air....... ....... ....... ....... ........ ....... ....... ....... ....... ........ ........ ........ ........ ....... ....... ....... ....... ........ ........ .... C. Rules Rules for Safe Safe Handli Handling ng of Hydrog Hydrogen... en...... ....... ....... ....... ....... ....... ........ ........ ........ ........ ....... ....... ....... ....... ........ ....... ....... ........ ........ ........ ....... ....... ...... .. D. Mainte Maintenan nance ce on Hydrog Hydrogen en Equipm Equipment ent.... ........ ........ ........ ....... ....... ........ ........ ........ ........ ....... ....... ....... ....... ........ ........ ........ ........ ....... ....... ....... ....... ...... .. E. Hydrog Hydrogen en Zone... Zone...... ....... ....... ....... ........ ....... ....... ....... ....... ........ ........ ........ ........ ....... ....... ....... ....... ........ ....... ....... ........ ........ ........ ....... ....... ........ ....... ....... ........ ........ ........ ....... ...

8 8 8 9 9 9

...... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... III. GENERAL GENERAL DESCRIPTION DESCRIPTION OF THE GAS CONTROL SYSTEM SYSTEM .... A. The Rotor Rotor Fan ........ ............ ........ ........ ........ ........ ....... ....... ....... ....... ........ ........ ........ ........ ....... ....... ....... ....... ........ ........ ........ ........ ....... ....... ....... ....... ........ ....... ....... ........ ........ ...... B. CO2 as Intermediat Intermediatee Gas..................... Gas............................. ................ ................ ................. ................. ................ ................ ................ ................ ................. ............ ... C. Distribut Distribution ion Pipes.............. Pipes...................... ................. .................. ................. ................ ................. ................. ................ ................ ................ ................ ................ ............ .... D. Gas Control Control Valves........... alves................... ................. ................. ................ ................. .................. ................. ................ ................ ................. ................. ................ ............ .... E. Casing Casing Liquid Liquid Detect Detector or ........ ............ ........ ........ ........ ........ ........ ....... ....... ....... ....... ........ ........ ........ ........ ....... ....... ....... ....... ........ ........ ........ ........ ....... ....... ....... ....... ...... .. F. Shaft Sealing Sealing ................ ......................... ................ ................ ................. ................ ................ ................. ................. ................ ................ ................ ................. ................. .......... G. Seal Oil Draining.... Draining............ ................ ................ ................. ................ ................ ................. ................ ................ ................ ................ ................ ................. ................. ........ H. Oil DeÀect DeÀectors ors ....... ........... ........ ........ ........ ....... ....... ....... ....... ........ ....... ....... ........ ........ ........ ....... ....... ........ ....... ....... ....... ....... ........ ........ ........ ........ ....... ....... ....... ....... ........ ....... ..... I. Gas Flow Flow Betwee Between n Caviti Cavities es ....... .......... ....... ....... ....... ........ ........ ........ ........ ....... ....... ....... ....... ........ ........ ........ ........ ....... ....... ....... ....... ........ ....... ....... ........ ........ ...... J. Scaven Scavengin ging g to Retain Retain H 2 Purity Purity in the End Caviti Cavities.... es........ ........ ....... ....... ........ ........ ........ ....... ....... ........ ........ ........ ........ ........ ........ ...... .. K. Vacuum acuum Seal Seal Oil System Systemss ........ ............ ........ ........ ........ ........ ....... ....... ....... ....... ........ ........ ........ ........ ....... ....... ....... ....... ........ ........ ........ ........ ....... ....... ....... ....... ...... .. L. Gas Purity Purity Monito Monitorin ring... g....... ........ ........ ........ ........ ....... ....... ........ ........ ........ ........ ....... ....... ....... ....... ........ ....... ....... ........ ........ ........ ....... ....... ........ ....... ....... ........ ....... ..... ..

10 10 10 10 10 10 11 11 11 11 11 16 16

IV. IV. GAS CONTROL VAL VALVE EQUIPMENT ........ ............ ........ ........ ........ ........ ........ ....... ....... ........ ........ ........ ....... ....... ........ ....... ....... ....... ....... ........ ........ .... A. Featur Features es of the Gas Contro Controll Valve alve Assemb Assembly ly ........ ............ ........ ........ ........ ........ ....... ....... ....... ....... ........ ........ ........ ........ ....... ....... ....... ....... ...... .. B. Featur Features es of Bottle Bottle Manifo Manifolds. lds..... ........ ........ ........ ........ ........ ....... ....... ........ ........ ........ ........ ....... ....... ....... ....... ........ ....... ....... ........ ........ ........ ....... ....... ........ ....... ..... C. Featur Features es in the Gas System System Piping.. Piping...... ........ ........ ........ ........ ....... ....... ........ ....... ....... ....... ....... ........ ........ ........ ........ ....... ....... ....... ....... ........ ........ ........ ...... .. D. Featur Features es of the Liquid Liquid Detect Detector or Assemb Assembly.. ly...... ........ ........ ........ ........ ........ ........ ........ ....... ....... ........ ....... ....... ........ ........ ........ ....... ....... ........ ....... .....

16 16 19 19 19

V. OPERATION OPERATION ................ ........................ ................ ................ ................. ................ ................ ................. ................ ................ ................. ................. ................ ................ ................ ........ A. Operat Operator or Activi Activitie tiess Start Start Up / Shut Shut Down Down ........ ............ ........ ........ ........ ........ ....... ....... ........ ........ ........ ........ ....... ....... ....... ....... ........ ....... ....... ....... ... B. Genera Generator tor Gas Purgin Purging g and Normal Normal Operat Operation..... ion......... ....... ....... ........ ....... ....... ....... ....... ........ ....... ....... ........ ........ ........ ....... ....... ........ ....... ..... C. Settin Setting g the Scaven Scavengin ging g Flow Flow Rates.... Rates........ ........ ........ ........ ....... ....... ........ ........ ........ ....... ....... ........ ....... ....... ....... ....... ........ ........ ........ ........ ....... ....... ....... ... D. Operat Operating ing the Genera Generator tor at Full Full Speed Speed with with Air Inside Inside.... ........ ........ ........ ........ ....... ....... ....... ....... ........ ....... ....... ....... ....... ........ ........ ....

19 19 21 27 28

........................ ................. ................ ................ ................. ................ ................ ................. ................. ................ ................ ................ ........ VI. ALARM ALARM RESPONS RESPONSES ES ................ A. Low-Lo Low-Low w and Low Generat Generator or Gas Purity Purity Alarms..... Alarms......... ........ ........ ........ ........ ........ ........ ....... ....... ........ ........ ........ ....... ....... ........ ....... ..... B. Genera Generator tor Gas Tempera emperatur turee High High ........ ............ ........ ........ ........ ........ ........ ........ ........ ....... ....... ....... ....... ........ ....... ....... ....... ....... ........ ........ ........ ........ ....... ..... C. Genera Generator tor Gas Pressu Pressure re High High ........ ............ ....... ....... ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ....... ....... ........ ........ ...... D. Genera Generator tor Gas Pressu Pressure re Low..... Low......... ........ ........ ........ ........ ....... ....... ........ ....... ....... ........ ........ ........ ....... ....... ........ ....... ....... ........ ........ ........ ....... ....... ........ ....... ..... E. Hydrog Hydrogen en Supply Supply Pressu Pressure re Low.... Low........ ....... ....... ........ ....... ....... ........ ........ ........ ....... ....... ........ ....... ....... ....... ....... ........ ........ ........ ........ ....... ....... ....... ....... ...... .. F. Liquid Detection... Detection............ ................. ................ ................. ................. ................ ................ ................ ................ ................. ................. ................ ................ ................ ..........

30 30 31 31 32 32 32


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........................ ................. .................. ................. ................ ................ ................. .................. ................. ................ ................ ................. ............... ...... VII. MAINTENAN MAINTENANCE CE ................ A. Leak Testing esting ................ ....................... ................ ................. ................ ................ ................. .................. ................. ................ ................ ................. .................. .................. ......... B. Regula Regularr Mainte Maintenan nance ce ....... .......... ....... ........ ........ ........ ....... ....... ........ ........ ........ ........ ....... ....... ........ ........ ........ ....... ....... ........ ........ ........ ........ ........ ........ ........ ....... ....... ...... C. Specia Speciall Mainte Maintenan nance ce ........ ............ ........ ........ ........ ........ ........ ....... ....... ....... ....... ........ ........ ........ ........ ........ ........ ........ ....... ....... ........ ........ ........ ....... ....... ........ ........ ........ .... D. If the Hydrog Hydrogen en Contro Controll Cabine Cabinett is Floode Flooded d with with Oil or Water..... ater......... ........ ........ ........ ....... ....... ....... ....... ....... ....... ....... ..... .. E. Materi Materials als and Design Design Condit Condition ionss ........ ........... ....... ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ...... ..

34 34 34 35 36 36

VIII. VIII. OPERATION OPERATION AND DESIGN REQUIREMENTS REQUIREMENTS FOR THE H 2 AND CO2 GAS SUPPLIES ................ ........................ ................. ................ ................ ................. ................ ................ ................ ................ ................ ................. ................ ................ ................. ................. ............ ... A. Requir Requireme ements nts on Gas used used in the the Genera Generator...... tor.......... ........ ........ ........ ........ ....... ....... ....... ....... ........ ....... ....... ....... ....... ........ ....... ....... ....... ....... .... B. Charac Character terist istics ics of Compre Compresse ssed d Gas...... Gas.......... ....... ....... ........ ........ ........ ........ ........ ....... ....... ........ ........ ........ ....... ....... ........ ....... ....... ........ ........ ....... ....... ...... C. Carbon Carbon Dioxid Dioxidee in Pipes Pipes and Valves..... alves......... ....... ....... ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ....... ....... ........ ........ ........ ...... D. Sizing Sizing the Carbon Carbon Dioxid Dioxidee Flow Flow Ori¿ce.. Ori¿ce..... ....... ....... ....... ........ ....... ....... ....... ....... ........ ........ ........ ........ ....... ....... ....... ....... ........ ........ ........ ........ ...... .. E. The Hydrog Hydrogen en Flow Flow Ori¿ce Ori¿ce ....... ........... ........ ........ ........ ........ ....... ....... ....... ....... ........ ........ ........ ........ ........ ........ ........ ....... ....... ........ ........ ........ ....... ....... ........ ...... .. F. Sizing Sizing the Manifo Manifold ld Pressur Pressuree Regula Regulator tor Valves.... alves........ ........ ........ ........ ........ ........ ........ ....... ....... ....... ....... ....... ....... ........ ........ ........ ........ ...... .. G. Calculatin Calculating g the Quantity Quantity of CO 2 Bottle Bottless Requir Required ed to Purge Purge a Genera Generator... tor....... ........ ....... ....... ....... ....... ....... ....... .... H. Calculati Calculating ng the Quantity Quantity of H 2 Bottle Bottless to Purge Purge and Fill Fill the Genera Generator.. tor..... ....... ........ ....... ....... ........ ....... ....... ....... ...

37 37 38 40 41 42 42 42 43

LIST OF FIGURES

Figure Figure 1. Figure Figure 2. Figure Figure 3. Figure Figure 4.

Repres Represent entss a typica typicall genera generator tor gas contro controll system system with with all possib possible le access accessori ories es ........ ............ ........ ........ .... Gas Control Control Valve Assembly Assembly .................. .......................... ................ ................ ................. .................. ................. ................ ................ ................. ............... ...... H2 or CO2 Bottle Bottle Manifo Manifold ld ........ ............ ........ ........ ........ ........ ........ ........ ........ ........ ........ ....... ....... ....... ....... ........ ........ ........ ........ ....... ....... ........ ........ ........ ........ ...... Liquid Liquid Level Detector Detector Assembly Assembly .................. .......................... ................ ................ ................. ................. ................ ................ ................ ................. ...........

7 13 14 15

LIST OF TABLES

Table 1. Purge Purge Activity Activity Parameters.... Parameters............. ................ ................ ................. ................ ................ ................ ................ ................. ................ ................ ................ ......... ..

4

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I. GENERAL GENERAL DESCRIPTIO DESCRIPTION N

This manual provides operation and maintenance instructions for the H 2/CO2 piping and other equipment which is external to the generator. This manual applies to unpackaged generators. Such generators are all generators with water cooled stators, all 390H generators, all hydrogen cooled Leads Down generators, and 324 Leads Up generators. A. Why Hydro Hydrogen gen

The generator interior components are cooled by convection whereby a gas transports heat to the generator gas/water heat exchanger. exchanger. Generator windage losses are greatly reduced with with hydrogen rather than air as the gas inside the generator because hydrogen has a lower density. In addition, compared to air, hydrogen has greater thermal conductivity and convection coef¿cients. The generator gas thermal capacity is further increased by the use of pressurized hydrogen. The sealed environment necessary to contain hydrogen has the secondary bene¿t of keeping the generator parts clean. Also, hydrogen, rather than air, greatly reduces armature insulation deterioration caused by corona. B. Explos Explosion ion Hazard Hazard

Hydrogen must be handled carefully to prevent catastrophic oxidation. The gas control valves provide a means for safely handling hydrogen. C. Inert Intermediat Intermediatee Gas

An inert gas, carbon dioxide, is used as an intermediate gas so that air and hydrogen do not mix inside the generator. The purging procedure for the generator has carbon dioxide introduced to displace the air, air, then hydrogen hydrogen introduced introduced to displace displace the carbon carbon dioxide. dioxide. The generator generator is then pressurize pressurized d with hydrogen and the pressure is maintained automatically with a control valve. The generator may remain pressurized with hydrogen during short outages even if the shaft is not on turning gear. Prior to opening the generator for maintenance, the hydrogen is depressurized, and then carbon dioxide is introduced to displace the hydrogen. Air is then introduced to displace the carbon dioxide, and the end shields can be opened. During an emergency it is important to at least purge the generator of hydrogen by introducing carbon dioxide. Gas control during the purge operations is performed manually at the gas control valve station. D. Essential Essential Parts Parts of the Gas Control Control System System

The gas control control system has these primary parts: Generator, with gas piping connections Gas Piping with Valving Gas Control Valve Assembly Hydrogen Control Cabinet, primarily for gas purity analysis Hydrogen Gas Storage


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Carbon Dioxide Gas Storage Liquid Level Detectors

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© G e n e r a l E l e c t r i c C o m p a n y , 2 0 0 8 . G E P r o p r i e t a r y I n f o r m a t i o n . A l l R i g h t s R e s e r v e d .

P H a y c d k r a o g g e e d n U a n n i d t s C a r b o n D i o x i d e G a s C o n t r o l S y s t e m f o r N o n

F i g u r e 1 . R e p r e s e n t s a t y p i c a l g e n e r a t o r g a s c o n t r o l s y s t e m w i t h a l l p o s s i b l e a c c e s s o r i e s

G E K 1 0 3 7 6 3 d

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E. Gas Storag Storagee

The source of the hydrogen or carbon dioxide is out of the scope of the equipment provided with the generator generator.. Some power plants have bulk supply systems, systems, some use bottle manifolds, manifolds, other have a combination of the two systems. GE does offer bottle manifolds if requested by the customer, and for those facilities which use those manifolds, instructions are provided in this document. The bottle bottle manifo manifolds lds for CO 2 orforH2 may may or may may not not be loca locate ted d near near the the gas gas cont contro roll valv valves es,, depe depend ndin ing g on the design of the facility. F. Gas Valve Station Station

The gas control valves are located in the gas control valve station of the power plant. It is good to place the gas dryer (if there is one), liquid level detectors, seal oil drain Àoat trap and other equipment in the vicinity of the gas control valves to reduce the number of hydrogen zones in the power plant. The hydrogen control cabinet, or a generator gas purity display, or other means of monitoring hydrogen purity should be available at the gas control valve station. II. WARNINGS ARNINGS CONCERNIN CONCERNING G THE USE OF HYDROGEN HYDROGEN

Hydrogen and air form a highly explosive mixture if concentrations are between 4.1% and 74.2% hydrogen by volume in air. When completely assembled and operated in the proper manner, the generator casing, which forms the hydrogen container, is a gas tight enclosure. In the very unlikely event of an explosion, the casing is strong enough to limit the destructive effect to the generator casing and the enclosed parts. A. General General Rules for Safe Safe Handling Handling of Hydrogen Hydrogen

Precautions must be taken to safeguard against a hydrogen explosion. 1. Never permit permit an explosive explosive mixture mixture to exist. 2. Eliminate Eliminate any possible possible source source of ignition. ignition. B. Unknown Unknown Contaminant Contaminant is is Assumed Assumed to be Air

Any unknown unknown contaminant contaminant in the hydrogen hydrogen gas shall be assumed to be air. air. The exception exception is that if the hydrogen is supplied directly from a hydrogen generation device, which derives the hydrogen from splitting water to hydrogen and oxygen, then the policy may be to assume that any unknown contaminant taminant will be assumed assumed to be pure oxygen. oxygen. Hydrogen Hydrogen and oxygen form an explosive explosive mixture with approximately 96% hydrogen (4% oxygen) by volume. During the carbon dioxide purge the contaminant is known to be carbon dioxide. If the seal oil is not being vacuum treated and the seal oil system is operating normally, the contaminant may be assumed to be air. At any other time, the contaminant contaminant is not known and shall be assumed to be air except as noted immediately above.

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C. Rules for for Safe Handling Handling of Hydrog Hydrogen en

The proced procedure ure for purgin purging g the genera generator tor is design designed ed to preven preventt explos explosive ive mixtur mixtures. es. The The purgin purging g steps steps of removing spool pieces, disconnecting bottles, and disconnecting the air supply must be strictly adhered to. In additio addition n 1. Do not have a permanent permanent air supply connected connected to the generator generator,, the hydrogen hydrogen control cabinet, cabinet, or any other device connected to the generator or gas piping. This practice prevents the possibility of an explosive mixture inside the generator due to operator error or valve leakage. 2. The generator and all piping must be pressure tested with with air or CO 2 for leaks prior to pressurizing the generator with hydrogen. 3. Hydrogen Hydrogen pressure pressure inside the generator generator must always be higher than ambient ambient to prevent air from leaking leaking in. If automatic automatic controls controls are inoperativ inoperative, e, the operator must manually manually maintain maintain pressure. pressure. Additionally, the seal oil systems requires a casing pressure of 2 psig minimum to drain correctly from the seal drain enlargemen enlargementt tank to the bearing bearing drain enlargement enlargement tank. tank. Please Please note that the Àoat trap will have to be bypassed until a casing pressure of 15 psig has been attained. 4. No welding welding may be done on the gas system system or seal oil system while there there is hydrogen in the generator. 5. The hydrog hydrogen en is sealed sealed at the shaft shaft to casing casing interf interface ace by oil ¿lm seals. seals. The operato operatorr must must be familiar with the shaft seal oil system prior to operating the generator gas system. 6. Avoid having having high pressure pressure hydrogen hydrogen escape to the room because because it can ignite ignite itself due to self generated static charges. 7. Hydrogen Àame is is nearly invisible. invisible. If an operator suspects suspects hydrogen is escaping into into the work area and desires to feel for a gas escape Àow, he should not use his hand or anything combustible, such as clothing. D. Maintenance Maintenance on Hydrog Hydrogen en Equipment Equipment

Components of the gas control system, which are intended for maintenance while the generator is pressurized, surized, are listed listed in a later section. Prior to maintenance, maintenance, the operator should should use, if available, available, two valv valves es rath rather er than than only only one one to isol isolat atee the the work work area area from from high high pres pressu sure re hydr hydrog ogen en.. Also Also,, prio priorr to open openin ing g a joint in a gas line, the operator should use, if available, a vent valve to depressurize the equipment. Some components might not have the vent valve or the second set of isolation valves close to the work site. E. Hydro Hydrogen gen Zone Zone

Electrical equipment in the vicinity of joints in hydrogen piping should not be sources of ignition. The local or national codes pertaining to explosive atmospheres vary, and should be investigated if the operator is suspicious of potentially sparking electrical equipment located in the vicinity of the hydrogen equipment. As a minimum, a Division 2 (or Zone 2) H 2 atmosphere extends for 1.2 meters for 5 psig to 60 psig (35 to 414 kPa–g, 0.352 to 4.22 kg/cm 2) piping and 1.8 meters for 75 psig to 150 psig (517 to 1034 kPa–g, 5.27 to 10.55 kg/cm 2) piping. It extends extends down 0.2 meters and up 4.2 meters. Potential Potential small small


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leak sites are non–welded joints in piping, including Àanges, valves, threaded joints, and O–rings and compression ¿ttings. The extent of the explosive atmosphere does not penetrate walls or other similar barriers. Each piece of electrical equipment in the explosive atmosphere should have one of the following: explosion proof housing with conduit or cable sealing, intrinsically safe circuit, hermetically sealed contacts, non–sparking components, non–incendive circuit, forced ventilation from a non–contaminated air source, or purging with pressurization. III. GENERAL GENERAL DESCRIPTI DESCRIPTION ON OF THE THE GAS CONTROL CONTROL SYSTEM SYSTEM A. The Rotor Rotor Fan

The generator generator gas is circulated circulated inside inside the generator generator by a fan on each end of the rotor. rotor. The fan creates a different differential ial pressure pressure of several several inches of water. water. The fan blown hydrogen hydrogen cools the generator rotor windings, armature windings (unless these are separately cooled by water), and armature magnet laminates. laminates. The fan blown hydrogen also is forced through a cooler, cooler, where it loses the heat it picked up from cooling the generator electro–magnetic components. The fan differential pressure is used by exte extern rnal al gas gas syst system em comp compon onen ents ts,, which which requ requir iree a smal smalll Àow Àow rate rate and and need need to retu return rn the the gas gas to the the gene generrator. Examples of possible equipment are (not necessarily supplied with every generator): gas dryers, over–heating particle detectors, and gas analyzers. B. CO2 as Intermediate Gas

The generator has a large open volume internally (1000 cubic feet (30 m 3) or more). more). This This volume volume contains hydrogen during normal operation. It contains air during maintenance outages. An inert gas is put into the generator volume as an intermediate gas so that air and hydrogen do not mix inside the casing. Carbon dioxide is used as the inert gas because it has a substantially higher density and lower therma thermall conduc conductiv tivity ity compar compared ed to hydrog hydrogen en or air. air. The substa substanti ntiall ally y differ different ent proper propertie tiess are used used by the gas analyzer (inside the hydrogen cabinet) so that gas concentrations during purging can be monitored. C. Distributi Distribution on Pipes Pipes

Along the top of the generator interior is a long pipe with holes, which acts as a manifold for admitting hydrogen. Similarly, along the bottom of the generator interior is a long pipe with holes for admitting carbon carbon dioxide. dioxide. These are called called the hydrogen distributi distribution on pipe and the carbon carbon dioxide dioxide distribution distribution pipe, respectively. respectively. During a purge operation, when gas enters the generator through one of the pipes, the gas, which is being displaced from the generator exits out the other pipe. D. Gas Contro Controll Valves Valves

The piping between the gas supply source and the generator typically has a set of valves, which the operator operator uses for purging purging the generator. generator. During During this purge operation, operation, the operator operator will look at the hydrogen control cabinet (or a remote display) so that he knows when the gas concentration is high enough to stop purging. E. Casing Casing Liquid Liquid Detector Detector

Drain ports are located in the low points of the generator. Liquid that enters these ports is routed to the generator casing liquid detector.

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GEK 103763d

F. Shaft Shaft Sealin Sealing g

The rotor of each generator extends beyond the generator casing at both the turbine end (TE) and the collector end (CE). These two shaft to casing interfaces are sealed against hydrogen escape with oil ¿lm shaft seals. seals. The shaft seals seals are located to the inside inside of the bearings. The shaft seals seals require a continuous supply of clean cool oil as supplied by the seal oil system. G. Seal Oil Draining Draining

Used Used seal seal oil oil insi inside de the the gene genera rato torr will will drai drain n to seal seal oil oil drai drain n enla enlarg rgem emen ents ts (one (one on the the CE and and one one on the the TE) where hydrogen bubbles can come to the surface of the oil, and then to a common Àoat trap valve which reduces the oil pressure from generator pressure down to bearing drain pressure and prevents hydrogen from escaping with the oil. H. Oil Oil DeÀectors

There are three gas cavities inside the generator, called: 1. The Turbin Turbinee End Seal Cavity Cavity,, 2. The Generator Generator Casing (where (where the generator generator windings windings are), and 3. The Collector Collector End Seal Seal Cavity Cavity. Seal oil is restricted to the end cavities. These cavities are separated from each other by oil deÀectors, whic which h are are exte extens nsio ions ns of the the casi casing ng that that have have a smal smalll clea cleara ranc ncee betw betwee een n the the stat static ic hard hardwa ware re and and the the roto rotorr. I.

Gas Flow Flow Betwe Between en Cavi Cavitie tiess

Gas Àow into and out of the cavities is limited to: 1. New clean hydrogen hydrogen being introduced introduced to the generator generator casing. 2. Gas to the hydrogen cabinet, cabinet, en route to the scavenging scavenging valves and the cell blocks, being taken taken from all three cavities but especially the end cavities because of the scavenging valves. (Vacuum treatment seal oil system generators might not have a scavenging capability). 3. The end cavities cavities are not connected connected to each other to the extent extent that gas cannot travel travel from one end to the other. Therefore gas Àow is limited to traveling from the generator casing to the end cavities. J. Scaven Scavengin ging g to Retain Retain H2 Purity in the End Cavities

The end cavities include include the seal oil drain enlargemen enlargements. ts. In these containers containers there is a net transfer transfer of air escaping solution from the oil and also hydrogen entering solution into the oil. The resulting effect is that the end cavities have a relatively high concentration of air. For generators, which have non–vacuum treated seal oil, the hydrogen cabinet has scavenging valves through through which the contaminat contaminated ed hydrogen is slowly exhausted exhausted to a vent. New clean hydrogen hydrogen from another another part of the hydrogen hydrogen system piping enters the generator generator casing to replace replace the scavenged scavenged gas. By this process, the air contamination in the end cavities remains at a safe low level to avoid the gas from being a combustible combustible mixture. mixture. Also, Also, the Àow of gas across across the thin gap of the inner oil deÀector


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retards the passage of the air contamination from entering the generator casing. Air contamination in the generator casing region decreases generator performance.

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P H a y c d k r a o g g e e d n U a n n i d t s C a r b o n D i o x i d e G a s C o n t r o l S y s t e m f o r N o n

F i g u r e 2 . G a s C o n t r o l V a l v e A s s e m b l y

G E K 1 0 3 7 6 3 d

1 3 25 of 56

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G E K 1 0 3 7 6 3 d

1 4


F i g u r e 3 . H

H y d r o g e n a n d C a r b o n D i o x f d i o r e N G o a n s P C a o c n k a t r g o l e S d U y s n t e i t s m

2

o r C O

2

B o t t l e M a n i f o l d

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Figure Figure 4. Liquid Liquid Level Detector Detector Assembly Assembly


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K. Vacuum Seal Seal Oil Systems Systems

Some generators have the seal oil treated in a vacuum chamber prior to the oil being exposed to the generator gas. These generators would not require the scavenging valves to be open except during the abnormal operation when the vacuum chamber does not have a vacuum or otherwise is not being used. The hydrogen control control cabinets cabinets provided with these generators generators might might not be connected connected to the seal oil drain enlargements. L. Gas Purity Purity Monito Monitoring ring

The generator gas in the end cavities should be monitored in generators, which do not have vacuum treated treated seal oil. If the seal oil is vacuum treated, treated, then, it would would be acceptable acceptable to monitor only the generator casing gas. During the purging operation, the gas purity of the venting gas (the gas exiting the generator) should be monitored. IV. IV. GAS CONTROL VALVE ALVE EQUIPMENT

The gas control control valves provide the operator operator with an ef¿cient ef¿cient and safe means of handling handling hydrogen. hydrogen. The gas control valves can be roughly placed into these categories: H2 Gas Storage

(perhaps nothing more than a bottle manifold)

CO2 Gas Storage

(perhaps nothing more than a bottle manifold and Àow ori¿ce)

H2 Gas Control Valves

(part of the gas control valve assembly)

CO2 Gas Control Valves


Purging Gas Control Valves


Liquid Detectors Interconnecting Piping and Valves A. Features Features of the Gas Control Valve Valve Assembly Assembly

The gas control valve assembly, assembly, Figure 2, is the operator’s control station during purging. purging. There are two main runs where gas Àows from left to right. H 2 is on the top run, and CO 2 or air is on the bottom run. There are two 3–way valves which operate in tandem. The top port of each 3–way valve connects to the generator directly, the outside ports connect to H 2 (on left) and CO 2 (on right) and the inside ports connect to the main vent. With the 3–way valve handles pointing down, the CO 2 run will be connected to the generator. With the 3–way handles pointing to the right, the H 2 run will be connected to the generator. Speci¿c features on the gas control valve assembly are: 1. H2 Gas Control Valves a. Hydrogen Inlet Pressure Pressure Relief Valve Valve (PSV-2923). Pressure will be automatically relieved to the piping design pressure if there is a pressure regulation malfunction, such as a leaky valve seat, in the hydrogen supply system upstream of the gas control valves. b. Hydrogen Pressure Breaker Valve (HV-2925). The operator can de–pressurize the hydrogen supply system by opening this valve.

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GEK 103763d

c. Hydrogen Spool Piece. The operator is required by by the equipment equipment con¿guration con¿guration to remove this segment of hydrogen pipe in order to connect an air supply to the generator. d. Hydrogen Inlet Pressure Instrumentation Instrumentation (PI-2930). A gauge provides provides information to the operator that there is hydrogen pressure available for the generator. A low pressure switch will inform the operator that the supply system has insuf¿cient pressure and that maintenance, such as replacing hydrogen bottles, is required. e. Connection Connection for Hydrogen Hydrogen Cabinet Cabinet Calibratio Calibration n (LE004). (LE004). A port is provided provided on the gas valves so that pure hydrogen hydrogen can be supplied to the hydrogen cabinet cabinet for calibrating the gas analyzers. f. Connection Connection for for Portable Portable Gas Analyzer Analyzer (LE033). (LE033). A port for providing providing pure pure hydrogen hydrogen for cali brating an auxiliary gas analyzer is provided for customer convenience. g. Generator Gas Flow Flow Control Pipe Pipe Restriction. This ori¿ce regulates the Àow rate of hydrogen during the purging step that has hydrogen being admitted to the generator. It is manufactured inside the piping to reduce the number of joints. h. Generator Generator Gas Pressure Pressure Regulator Regulator (PCV-2935). (PCV-2935). A pressure pressure regulator regulator is provided provided as an automatic pressure control to replace small amount of generator internal gas used by the gas analyzer, gas that has gone into solution with the draining seal oil, and gas which may slow leak out the casing casing joints. When carbon dioxide dioxide is being being admitted into the generator an isolation lation valve in series series with this regulator regulator is closed. During During purging purging,, the gas goes through this regulator, and it is full open because during purging generator gas pressure is well below the regulator set point. i. Genera Generator tor Gas Pressu Pressure re Regula Regulator tor Bypass Bypass Valve alve (HV (HV-29 -2935) 35).. The Genera Generator tor Gas Pressu Pressure re RegRegulator is not used during the initial generator pressurization. During this operation the bypass valve is open. j. Hydrogen Secondary Block Valve Valve (HV-2936). A second block valve is provided for redundant hydrogen isolation. It would be closed if the Generator Gas Pressure Regulator is removed for maintenance. 2. CO2Gas Control Valves a. Carbon Dioxide Pressure Pressure Relief Valve Valve (PSV-2940). Pressure will be automatically automatically relieved to the piping design pressure if there is a pressure regulation malfunction, such as a leaky valve seat, in the CO 2 supply system upstream of the gas control valves. b. Carbon Dioxide / Air Spool Piece. Prior to air being admitted to the generator, this spool piece will have have to be removed removed from the carbon dioxide dioxide line and placed into into the air line. When in the air line, it will be impossible for either hydrogen or carbon dioxide to be admitted to the generator. c. Carbon Dioxide Supply Pressure Gauge (PI-2944). A gauge indicating carbon dioxide dioxide supply pressure is provided for the operator performing the purging operation. d. Other Other Ports in the Carbon Carbon Dioxid Dioxidee Line. Line. In the carbon carbon dioxid dioxidee line line there there are utilit utility y ports ports which, might not be used: hydrogen cabinet gas analyzer calibration (LE055), gas dryer purge


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(LE008), (LE008), and one un–assigned un–assigned.. A port for portable portable gas analyzer calibration calibration (LE013) (LE013) is provided for customer convenience. e. Carbon Dioxide Shut Shut Off Valve Valve (HV-2946). The carbon dioxide shut off off valve is closed closed except when carbon dioxide is admitted to the generator. If it is open during normal operation, carbon dioxide may leak into the generator. f. Air Shut Off Valve Valve (HV-2947 (HV-2947). ). The air shut off valve valve is closed except except when air is admitted to the generator. g. Temporary Air Connection (LE009). (LE009). A port is provided for clean dry dry air so that the generator can be ¿lled with air prior to opening a cover on the generator. 3. Purging Purging Control Control Valves Valves a. Three–W Three–Way ay Valves Valves (HV-2952/ (HV-2952/HV-29 HV-2955). 55). Each of the two three–way three–way valve handles handles should always be in the same position as the other. In one con¿guration the hydrogen control valves are connected to the generator and in the other con¿guration the carbon dioxide control valves are connected connected to the generator generator.. In both con¿gurations con¿gurations the generator generator is connected connected to the vent valve. b. Check Valves (CV-2950/CV-2940). There is a check valve in the supply line immediately adjacent to the three–way valves. The check valve prevents generator gas from back–Àowing up the hydrogen or carbon dioxide supply lines. c. Vent Valv Valvee (HV-2954 (HV-2954). ). The main main vent valve valve has 2 modes of operati operation: on: (a) Fully Fully open to depressurize the generator, (b) Partially open during the purge operation to maintain generator internal pressure a few psi (several kPa, a fraction of a kg/cm 2) above ambient. d. Port in Vent Vent Line for Gas Analyzer (LE056). The port in the vent line line for the gas analyzer has a projection into the vent line so that it senses total pressure (which equals pressure plus the kinetic energy of the gas Àow). It is ported to the hydrogen cabinet gas analyzer for use by the operator during purging so that he knows when to stop purging. e. Port in Vent Vent Line for Portable Gas Analyzer Analyzer (LE034). An additional port is placed placed in the vent line with a total pressure pressure port for use with a portable portable gas analyzer. analyzer. It is provided provided as a convenience to the customer. f. Generator Gas Gas Pressure Instrumentation (PI-2950/PT-2950/PSL-2 (PI-2950/PT-2950/PSL-2950). 950). A gauge and high/low pressure switches for generator gas pressure are provided on the assembly. assembly. g. Generator Generator Gas Pressure Pressure Relief Valve Valve (PSV-2950) (PSV-2950).. A relief valve is provided provided so that during during normal operation, generator casing pressure does not increase above the capability of the seal oil system. There is a Àow restriction upstream of it so that it has more Àow capability than a failed open generator gas pressure regulator, but not so much that the generator depressurizes rapidly if it itself fails open. The Àow restriction is inside the pipe so that the number of piping joints is reduced. h. Vent Stack Drain Valve Valve (HV-2943). A valve is provided on on the bottom of the vent stack stack so that condensat condensation ion can be removed. Water condensed condensed in the pipes leading to the generator generator would

18


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also drain down to this valve during during outage times. A slight bit of oil may be mixed with the water. B. Features Features of Bottle Bottle Manifolds Manifolds

If a hydrogen gas bottle manifold is provided, it has these features. The carbon dioxide bottle manifold has the same features: 1. Pigtails, Pigtails, one for each hydrogen hydrogen gas bottle. bottle. There is a check valve on the manifold manifold end ¿tting ¿tting of each pigtail. 2. Globe Globe Valve, Valve, one for each hydrogen hydrogen bottle. bottle. 3. Pressure Regulator Valve. Valve. These valves drops the the pressure from the high bottle manifold pressure pressure down to approximately 125 psig (862 kPa–g, 8.79 kg/cm 2) as required by the downstream Àow regulation restriction. Gauges are provided on the regulator valve. 4. Pressure Pressure Regulator Regulator Bypass Valve. Valve. The bypass bypass valve should be opened or closed completely completely and not put into a partially open position. C. Features Features in the the Gas System System Piping Piping

1. CO2 Flow Regulatio Regulation n Ori¿ce. The CO 2 piping upstream of the gas control valves should have a Àow regulation ori¿ce to control Àow rate during the purge step which admits CO 2into the generator. Downstream of this ori¿ce there should be a section of large diameter pipe where solid CO 2 precipitation can accumulate. 2. Drip Legs. Legs. Low points points in pipe runs are provided provided with one one or two valves. Accumulate Accumulated d liquid can be drained. If there is only one valve, then either the pipe must be isolated or the generator degassed prior to draining the liquid. If there are two valves, then the liquid can be drained by alternating the valves between open and closed. Drip legs are placed in piping so that condensation and other contamination is routed away from sensitive equipment. 3. Valves on the Underside Underside of the Generator. Generator. There are several types of gas gas connections to the the generator: low point drains, gas feeds and vents, and pipes to gas sensing and gas processing equipment. Many of these have isolation valves at the generator connection to assist in maintenance. 4. Equipment Equipment Isolatio Isolation n Valves Valves.. Most pieces pieces of equipment equipment have isolatio isolation n valves so that they may be repaired on line. D. Features Features of the Liquid Liquid Detector Detector Assembly Assembly

The liquid detector detector assembly has these features features for each detector: detector: isolation isolation valve, valve, drain valve, valve, sight sight glass, ¿ll port for test, and the sensor. V. OPERATION OPERATION A. Operator Operator Activities Activities Start Start Up / Shut Down Down

1.

PrePre-St Star artt-Up Up


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Read the warnings warnings concerning the explosiveness explosiveness and combustibility combustibility of hydrogen, which is in an earlier section of this document.

b. Ensure the piping to the cabinet and the piping of the gas valves used for gas control are correctly installed. c.

Ensure Ensure the external external wiring wiring of gas system electrical electrical equipmen equipmentt is correctly correctly installed. installed.

d. Inspec Inspectt the gas system system equipm equipment ent for damage damage.. Drain Drain out liquid liquid,, which which may have have accumu accumulat lated ed in the piping. e.

Be familiar familiar with the operatio operation n of the seal oil system system and the generator generator gas control control system. system.

f.

Be familiar familiar with the use use of the hydrogen hydrogen control control cabinet cabinet for gas purity purity monitori monitoring. ng.

g. Ensure Ensure ther theree is enoug enough h CO 2 available to purge out the air plus enough CO 2 to purge out hydrogen should there be an emergency. h. Ensure Ensure the gas valves are in the correct correct position position for the admissi admission on of carbon dioxide. dioxide.

2.

i.

Energize Energize the the hydrogen hydrogen control control cabine cabinett and prepare prepare it it for use. use.

j.

Energize all seal oil pump motors, including all AC and DC, and all primary, primary, backup, and emergency pump motors.

Leak Leak Test Piping Piping.. After installation and prior to introducing hydrogen to the gas system equipment, all parts of the gas system should be air tested to ensure there is no leakage. A similar, perhaps coinciding, test should be performed to the generator casing and end shields. The air test may be performed with CO2 after purging out the air if additional CO 2 is available to be used to increase the pressure to a usable level for leak testing. Leaks can be identi¿ed identi¿ed by applying a soapy solution to the joints joints and welds. welds. A typical solution solution would be liquid soap, glycerin and water. Bubbling will indicate leakage.

3.

Star Start– t–Up Up.. The seal oil system should be started when the admission of carbon dioxide into the generator casing has raised the internal pressure to 2 psig. The pressure forces the seal oil to drain through the Àoat trap valve valve Àow restriction restriction.. Initially Initially,, as pressure builds, builds, seal oil may begin begin to Àood the seal oil drain enlargement. It is important that the seal oil not build up to the extent that it Àoods the generator. Theref Therefore ore an operat operator or should should manual manually ly bypass bypass the Àoat Àoat trap trap tempor temporari arily ly until until the genera generator tor casing casing pressure is 15 psig. Start–Up Steps: a.

20

Manually Manually open open the Àoat Àoat trap bypass bypass valve. valve. (See Section Section V. V. B. 5 Page 2 6 for further Àoat trap bypass instruction details.)


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b. Start pressurizing the generator casing with CO 2. c.

Turn Turn on the seal oil supply supply system system once once the carbon carbon dioxide dioxide pressure pressure reaches reaches 2 psig.

d. As the pressure inside inside the generator generator increases, the the Àoat trap trap bypass valve should be manually closed, starting no earlier than 5 psig and reaching full closed position at 15 psig. 4.

Purging Purging and Other Normal Normal Operat Operations ions.. Please see below for other operator activities.

5.

Shut Shut–D –Dow own. n. Prior to turning off the seal oil system, the generator should be purged so that hydrogen is not present in a dangerous concentration. If maintenance activity is required inside, beneath, or near the generator, or if the down time will be more than a few hours, then the carbon dioxide should be purged out and replaced with air. After the purging steps are complete: a.

Reduce Reduce the Carbon Carbon Dioxide Dioxide pressu pressure re by venting. venting.

b. As the pressure inside the casing falls to 15 psig, begin to open manually the Àoat trap bypass valve. The valve should be completely open when the internal pressure reaches 5 psig. c.

Turn Turn off the seal seal oil supply supply system system when the internal internal pressu pressure re reaches 2 psig. psig. This prevent preventss Àooding of the generator or hydrogen control cabinet with oil.

d. Open the generator generator vent valve. valve. e.

Do not open open the generator generator end shields shields or other other access covers covers until until the operator operator is sure that that there is no pressure inside the generator.

f.

Use compressed compressed air or large large fans to blow blow CO 2 out of low spots in the generator after opening the generator.

B. Generator Generator Gas Purgin Purging g and Normal Normal Operation Operation

The generator is purged with gases before and after normal operation of the generator. 1. Purge Purge Table able

Perform the operations per the following chart. Please read the clarifying notes below. 2. General General Inform Information ation on Purging Purging

Estimated Time of Purge = Volume of Generator *Amount of Gas / Flow Rate Reco Recomm mmen ende ded d Flow Flow Rates Rates of CO2 and and H2. The The reco recomm mmen ende ded d carb carbon on diox dioxid idee Àow Àow rate rate is 120 120 scfm scfm 3 3 (3.4 s m /minute) for a 2800 ft3 (80 m ) generator internal volume. The recommended hydrogen Àow rate is 50 scfm (1.4 s m 3/minute) for a 2800 ft3 (80 m 3) generator internal volume. *

Please see comments concerning concerning allowable allowable gas speeds unders section B in paragraph paragraph 2.


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Please note that hydrogen is purging the carbon dioxide out of the machine in preparation for normal operation. operation. The gas speed in the feed piping shall be 300 feet per second maximum. maximum. Higher Higher speeds speeds are permitted permitted in the vents if compressib compressible le gas friction friction affects are considered. considered. These Àow rates are approximate, and for generator volumes greatly different from 2800 ft3 (80 m 3), the recommended Àow rate would change proportionally with generator volume (for example, twice the Àow rate if the generator is twice as large). Gas Àow rates during purging shall be slow enough to take advantage of the buoyancy effect of the gases inside the generator so that mixing is avoided. This will minimize the customer’s gas usage during the purge.

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Table 2. Purge Activity Parameters Activity

Air to CO2

CO2 to H2

H2 ¿ll

Normal

degas

H 2 to CO2

CO2to Air

Estimated Time (hrs)

0.5

2.0

1

N/A

0.5

1

N/A

Recommended Flow Rate* (s m 3/hr) (scfm) (minutes per bottle)

3.4 120 3

1.4 50 5

N/A N/A N/A

N/A N/A N/A

N/A N/A N/A

3.4 120 3

N/A N/A N/A

Amount of Gas (x Generator Volume)

1

2

n

N/A

0

2

>3 >3

Purge

Purge

N/A

Normal

N/A

Purge

Pu Purge

H2in CO2

H2 in Air

H 2in Air

H2 in Air

H2in CO2

CO2 in Air

70% CO2

90% H2

N/A

N/A

N/A

5% H 2 5% CO2

3–Way Valves

down

right

right

right

either

down

do down

Main Vent Valve

partially open

partially open

closed

closed

full open

partially open

partially open

Generator PCV Isolation Valve

closed

open

open

open

closed

closed

closed

Generator PCV Bypass Valve

closed

closed

open

closed

closed closed

closed

CO2Shut–Off Valve

open

closed

closed

closed

closed open

closed

Air Shut–Off Valve

closed

closed

closed

closed

closed

closed

open

H2 Spool Piece

out

H2 line

H2 line

H2 line

H2 line

either out position

CO2Spool Piece

CO2 line

CO 2 line

CO2 line

CO2 line CO2 line

Hydrogen Control Cabinet Controls “Mode” Selection “Function” Selection Stop %

CO2 in Air

Gas Valve Station Valve Positions


CO2 line

air line

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Automatic Flow Control of CO 2 and H2 During Purging. The Àow rate during purging is automatically controlled by the size of Àow restrictions which are integral with the equipment. Bottle Bottless May Be Discha Discharg rged ed Simult Simultane aneous ously ly.. Two bottle bottless would would decrea decrease se in pressu pressure re in about about twice twice the time, three bottles in about thrice the time, relative to the time given on the table above. Manual Generator Pressure Control During Purging. Because of the gas strati¿cation due to buoyancy, which occurs inside the generator, there will be very little if any change in gas mixture in the venting gas for the ¿rst 2/3 of the purge time. During the last 1/3 of the purge, the gas concentrations will change rapidly. The generator vent valve (HV-2954) should be positioned and adjusted to hold between 2 and 5 psig (13.8 to 34.5 kPa–g, 0.14 to 0.35 kg/cm 2) inside the generator generator.. The generator generator pressure will change, and the valve may need adjusting, during the ¿nal 1/3 of the purge because during that time the gas density may change dramatically. Quantifying Gas Quantity. Because gas is compressible and buoyant it is dif¿cult to measure and unnatural to perceive the concept of gas quantity. The mass of a sample of gas does not change, although its volume may change due to the interactions of pressure, temperature, and density. Therefore fore the the best best way way to quan quanti tify fy gas gas quan quanti tity ty is by unit unitss of mass mass.. Howe Howeve verr, beca becaus usee gas gas has has litt little le weig weight ht and deforms and diffuses, the mass cannot be determined by measurement on a weight scale. And units of mass do not have direct importance because gas is used for its volume, not its mass, in most applications in mechanics. Therefore, it has become the industry standard to describe gas quantity in units of “standard” volume. The “standard” “standard” means that pressure pressure and temperature temperature are assumed assumed to be at 14.7 psia (1 atmosphere at sea level, 101.4 kPa–a, 1.034 kg/cm2–a) and 77°F (25°C), respectively. Sometimes the temperature standard is different, so it is important to know the speci¿c standard pressure and temperature, which are being used whenever a standard gas volume is given. The actual pressure or temperature of a gas sample may be substantially different from the “standard” conditions, however, the mass of the gas sample can be quanti¿ed by pretending it is at “standard conditions”. For example, a bottle of compressed gas may have only a few cubic feet of physical volume, but have hundreds of cubic feet of “standard” volume worth of gas because the gas can expand to the “standard” pressure. This measurement system works because there is only one gas density corresponding to a pressure/temperature combination for a particular type of gas. Therefore there is only one “standard” density for a type of gas. The “standard” volume of a particular gas can therefore be considered a measurement of mass. “scfm” means “standard cubic feet per minute”. “Standard” means the gas mass Àow is equivalent to the volumetric Àow if the gas were at 25° C (77°F) and 1 atmosphere (14.7 psia, 101.4 kPa–a, 1.034 kg/cm 2, which is 0 psig at sea level). level). The “s” in front of “m 3/hr” also means “standard”. 3. Purgin Purging g With With CO2

Low Pressure Means Less Gas Used. During the purge process the generator gas pressure should be between 2 and 5 psig (13.8 to 34.5 kPa–g, 0.14 to 0.35 kg/cm 2), preferably 2 psig (13.8, kPa–g, 0.14 kg/cm 2) by throttling valve HV-2954. A lower generator gas pressure requires less purge gas. This is because purging is a gas displacement phenomena, which is volume driven, and higher pressure gasses have more mass (more gas) per a given volume. For example, a 2800 ft3 (80 m 3)

24


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generator will require one additional CO 2 bottle of gas to displace H 2 for each psi (each 7 kPa, each 0.07 kg/cm 2) additional gas pressure. Low Flow Rate Means Less Gas Used. Flow rate during the purge is kept low to avoid mixing the gasses inside the generator. The gasses are naturally separated by buoyancy. Nitrogen Content of Air. The 70% CO 2 in Air concentration is acceptable because it results in only about 6% O2, the remainder being the inert gases N2 and CO 2 Purge Dead Cavities with CO 2. After the generator generator is purged purged with carbon carbon dioxide dioxide to 70% CO 2 in Air or 95% CO 2 in H2, the generator gas pressure of a few psig (several kPa–g, a fraction of a kg/cm2) should be used to purge the dead cavities cavities of the generator generator.. Most importantl importantly y, the seal oil drain enlargements should be purged by simultaneously opening the scavenging valves long enough to vent out 35 ft3 (1 m 3) of gas. If there are volumes of air or H 2 which cannot be purged using generator CO 2 pressure, then a portable CO 2 supply should be used. Purge Out H 2 after Rotor has Slowed Down. Down. Prior to admitting admitting CO 2, it is necessary to wait until the rotor has decelerated decelerated to turning turning gear or stand still. still. A rotating shaft will mix the gasses gasses inside the generator. The mixing will destroy the buoyancy layering which keeps CO 2 on the bottom and H2 on the top. If the generator is to be purged while the shaft is rotating, there should be suf¿cient CO2 available available to account for the mixing. mixing. This can be several times the normal amount amount of CO 2 required for a purge. Water Vapor Vapor Fog Layer. Layer. During During the purge purge where cold CO 2 replaces ambient temperature air, a layer of condensed condensed water vapor fog forms at the boundary boundary of the two gasses. gasses. The optimum optimum CO 2 Àow rate was originally calculated based on witnessing the movement of this fog layer. 4. Placin Placing g Air Air into into Genera Generator tor

The Removable Spool Pieces are designed to (a) inhibit the introduction of air while there is hydrogen in the generator and (b) provide a means of absolutely preventing the inÀow of dangerous gas while personnel are inside the generator performing maintenance. Air Can Have a High Flow Rate Rate .Air is relatively relatively inexpensi inexpensive ve compared compared to H 2 and and CO2. Therefore, Therefore, the generator and the purge procedure are not designed to minimize the quantity of air needed. So that that there there is no chance chance of mixin mixing g H 2 and air together together,, air is introduc introduced ed into the the generator generator through through the CO2 distribution pipe on the bottom of the generator interior. Thus the lighter air is below the heavier CO 2, and the gasses thoroughly mix during purging. Because mixing cannot be avoided, a very high Àow rate of air can be used. Air Supply Must Be Typically Typically Disconnected. All air connections to the generator should be disconnected when CO 2 is admitted, and especially when H 2 is inside the generator. Remove Bottles and Spool Pieces Prior to Admitting Air. Prior to admitting air into the generator, totally disable the CO 2 and the H 2 feed lines, which connect CO 2 or H 2 bottles to the generator, to the hydrogen cabinet, and to all other equipment, such as a gas dryer. Closing valves is not suf¿cient. The bottles should be removed, removed, or the piping disassembled at a spool piece or other other ¿tting. If a workman is working on the generator, a dangerous situation can develop by gas leakage through valves. CO 2 is poisonous at moderately low concentrations and H 2 is explosive at concentrations above 4%.


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Blow out CO 2 from Low Spots in Generator. After the generator is purged with air, some CO 2 will remain in the generator low points. After the end shield, bushing box cover, or other access plate is removed, the generator should be blown free of CO 2, either with a compressed air hose or large fans. Contro Controll Conden Condensat sation ion During During an Outage Outage.. During During a genera generator tor outage outage the the valves valves in the pipi piping ng should should be closed so that humid atmospheric air does not enter the piping. Humid air will cause condensation to form internal to the piping as ambient temperature Àuctuates day to night. Speci¿cally, Speci¿cally, the valves on the underside of the generator should be closed. This will prevent corrosion internal to the pipe and water build–up. Water which freezes could cause pipe rupture and a resulting gas leak. Alternatively, to route condensed water to the vent stack, the three way valve handles should be to the right. 5. Turn urning ing On On and Off the the Seal Oil Oil Supply Supply

Turning on the Seal Oil System. The seal oil system should not be turned on prior to the generator internal pressure reaching 2 psig of CO 2. At this low pressure, the Àoat trap bypass valve must be open to prevent Àooding of the generator or the hydrogen control cabinet. Then the seal oil system may be turned on for the purge. purge. While While the bypass bypass is used, it is critical critical that the oil level not fall below the Àoat trap. If this happens and there is hydrogen inside the generator, hydrogen could enter the bearing area through through the bearing bearing drain enlargement. enlargement. As the generator generator internal internal pressure pressure rises above 5 psig, the bypass valve should be throttled, until it is fully closed when the generator internal pressure reaches 15 psig. Shutting Shutting Down the Seal Oil System. Under no circumstance circumstance should should the seal oil system be shut down while while there is hydrogen hydrogen in the generator generator.. This procedure procedure refers to after the hydrogen has been purged out with CO 2. As the the air air purg purgee redu reduce cess the the gene genera rato torr inte intern rnal al pres pressu sure re to 15 psig psig,, the the Àoat Àoat trap trap bypa bypass ss valv valvee shou should ld be manually opened, such that it is completely open when the internal generator pressure drops to 5 psig. The seal oil system should should be shut off when the pressure pressure inside the generator generator drops to 2 psig. The seal oil system should not be kept operating if the pressure in the generator drops below 2 psig because the Àow restriction of the Àoat trap may cause Àooding of the generator with oil. 6. H2 Purging, Filling, Normal Operation, and degassing

CO2 Must Always Always Be Available. vailable. The CO 2 feed system for the generator should be continuously operational during the H 2 purge purge and normal operation. operation. It may be necessary necessary to emergency emergency purge out the H 2 at any time. Pressurize the Generator with H 2 to a Slightly Slightly Lower Pressure. Pressure. The generator generator does not need to be ¿lled to the full operating pressure, but rather about 10% low (relative to absolute pressure). The gas temperature shortly after the purge and ¿lling will be nearly ambient because of the huge thermal mass of the generator electrical components. During operation the generator gas is much warmer. warmer. By the perfect perfect gas law, law, the pressure pressure will increase as the temperature temperature increases increases given a constant constant volume volume for the gas. Therefore, Therefore, the pressure pressure at the end of a ¿ll should should be per the table below. below.

26

Pressure During Operation

psig

15

30

45

60

75

Pressure After H 2 Fill

psig

12

25.5

39

52.5

66


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GEK 103763d

Pressure During Operation

kPa–g

103

207

310

414

517


kPa–g

83

176

268

361

454

Pres Pressu sure re Duri During ng Oper Operat atio ion n

kg/c kg/cm m2

1.05

2.11

3.17

4.22

5.28


kg/cm 2

0.84

1.79

2.74

3.69

4.64

Close H2 Feed When De–Pressurizing the Generator. Generator. When the operator opens the vent valve to depressurize the generator, he should also close the hydrogen feed valve in the pipe leading to the generator. 7. Hydrogen Hydrogen Contro Controll Cabinet Cabinet Use Use During During Purge Purge

Hydrogen Hydrogen Control Cabinet Settings. Settings. The hydrogen control control cabinet cabinet is the device which monitors generator gas purity. “Purge” selection will control valves such that the gas sample is taken from the generator vent. “Normal” selection will control valves such that the gas sample is taken from the generator itself. CO2 Contamination of Filters. Be sure the “purge” setting and not the “normal” setting is applied to all applicable gas sensors of the hydrogen control cabinet when purging. This will prevent CO 2 from entering entering the ¿lter dryers, which are molecular molecular sieves. If CO 2 enters the ¿lter dryers it will slowly bleed out over the ¿rst day of normal operation with H 2 in the generator. generator. If this happens the reading will be inaccurate, in that it will indicate more air contamination in the generator gas than is actually present during the ¿rst day of operation. C. Setting Setting the Scavenging Scavenging Flow Rates Rates

Generators Generators which which do not have have vacuum vacuum treated treated seal oil should should be provided provided with a means of conti continuou nuously sly bleeding out a small Àow of generator gas from each of the two seal oil drain enlargements. The seal oil drain enlargement enlargementss are where air contaminat contamination ion will be introduced introduced into the generator generator because because air comes out of solution from the seal oil. The gas control valves will automatically introduce clean hydrogen into the generator casing when gas is bled out, with the result of maintaining generator gas purity at an acceptable level. The scavenge Àow rate visual meters and hand operated control valves are typically located on the hydrogen hydrogen control control cabinet. cabinet. The Àow rates should should be set so that the end cavity generator generator gas purity is maintained substantially above the Upper Explosion Level for H2 in air, see Table 1 above. The exact value is dependent on the accuracy of the purity monitoring equipment and the operating philosophy of the power plant (Refer to the international standard IEC 842 for guidance if no philosophy exists). 1. Star Start– t–Up Up

Initially, before there is any data or precedence on which to base the actual Àow rate set point, the valves should be set for removing about 1 scfh (472 ml/min) from each seal oil drain enlargement. After several hours, which is a long time duration to ensure the system has stabilized, the Àow rate can be changed. changed. Higher Higher Àow rates rates will improve improve gas purity purity,, lower Àow Àow rates will will degrade degrade gas gas purity purity..


27

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A high Àow rate is not desired from an economic perspective because the scavenged gas is lost to a vent. 2. After After a Low Purity Purity Alarm Alarm

There There are three three settin settings gs for scaven scavenged ged gas purity purity:: Contro Controll Set Point, Point, Low Low Alarm, Alarm, Low– Low–Low Low Alarm. Alarm. The Low–Low Alarm point should not be below 80% H2 in Air by volume purity. If the hydrogen purity in an end cavity drops to the low alarm, the operator should re–adjust the scavengin scavenging g rates to achieve achieve the control control set point. It may happen happen that the Àow rate cannot be increased further, in which case the generator should be shut down and purged of hydrogen so that the cause of the problem can be ¿xed. 3. Tren rendin ding g

It is unusual unusual to have a need to increase increase scavenging. scavenging. Records Records should be kept and plotted plotted so that the two end cavity scavenging rates can be trended over long periods of time. Generator shaft seal health, CO 2 valve leaks, and other problems can be identi¿ed in this way. 4. Jumpy Jumpy Flow Flow Gauge Gauge

If the Àow gauge for scavenging gas is jumpy, meaning the Àow indicator moves every second or so by itself, then the equipment can continue to operate until the next outage, at which time the cause for the jumpy reading can be investig investigated ated and corrected. corrected. The correct reading reading of Àow is the average of the jumpy readings. Jumpiness is caused by liquid in the lines (so all drip legs should be drained), or light solid blockage that moves back and forth. Flow through thermister based gas analyzers is also permitted to have some jumpiness. D. Operating Operating the Generator Generator at Full Speed Speed with Air Inside Inside

During commissioning or another special circumstance, the generator may be required to operate at full speed with air inside the casing. The shaft seals will need oil for lubrication during this operation mode, and therefore the seal oil system must be operating, with the Àoat trap bypass valve manually opened. Without Without the valve opened, the seal oil, which drains to the generator side and out the Àoat trap, may back up into and Àood the generator. Therefore, the generator should be pressurized with air to 2 to 5 psig (13.8 to 34.5 kPa–g, 0.14 to 0.35 kg/cm2) and the Àoat trap bypassed so that the oil will drain properly. properly. A higher pressure, about 15 psig (103.5 kPag), is necessary, if it is not possible to manually monitor the Àoat trap performance. NOTE

It may not be possible to produce any electrical power under these circumstances. Contact GE Power System Product Services to determine operational limits. The generator fan differential pressure will increase proportional proportional to gas density. density. Therefore it may be 3, 4, maybe 8 times as high as during normal operation with hydrogen inside the generator. The generator fan differential pressure gauge may not be designed for the high differential service, and may be required to be isolated so that its mechanisms do not get damaged. In particular, if the fan differential gauge is a manometer, it must be isolated so that the heavy bromine liquid does not get blown into the generator where it would cause corrosion.

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The greate greaterr fan differ different ential ial pressu pressure re may cause cause oil to be drawn drawn into into the genera generator tor unless unless:: (a) the the pressu pressure re is kept high and (b) the vent lines, typically used for scavenging, on the two seal oil drain enlargements are slightly open such that air is being vented from out of the generator through them. The air supply supply should be clean and dry. dry. A ¿lter and an air dryer should should be used. If a hydrogen gas dryer is provided with the generator, it should be isolated from the system and not used unless the gas dryer manufacturer speci¿cally approves of its use as an air dryer. VI. ALARM ALARM RESPON RESPONSES SES

Activation of any alarm requires prompt attention by the operator. Excessive delay in correcting an alarm condition could result in damage to the generator and equipment, and possible injury to personnel. Alarms in the hydrogen gas system are summarized below. 1.

Operator Operator Investigat Investigation: ion: Further deteriora deterioration tion will will not cause a generator generator load reductio reduction n nor an unsafe condition: Small accumulation of liquid in drip legs Indications concerning humidity or the gas dryer equipment (if part of the gas system)

2.

Operator Operator Investigat Investigation: ion: Operator attentio attention n is necessary necessary at the soonest soonest convenien convenience: ce: High Generator Gas Pressure Low Hydrogen Supply Pressure High Generator Casing Liquid Detection

3.

Operator Operator Investiga Investigation tion:: A generator generator load reductio reduction n or an unsafe conditi condition on is possible possible with with further further deterioration: Low Generator Gas Pressure Low Generator Gas Purity High Generator Gas Temperature High–High Generator Casing Liquid Detection High Seal Oil Drain Enlargement Liquid Detection Insulation Overheating Particle Detection Alarm (Not provided with all generators)

4.

Manual Shutdown Shutdown of Turbine Turbine–Gene –Generator rator Low–Low Generator Gas Purity

5.

Automatic Automatic Shutdown Shutdown of Turbine Turbine–Gene –Generator rator::


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None 6.

Automatic Automatic Trip Trip of Turbine Turbine–Gene –Generator rator None

A. Low-Low Low-Low and Low Generator Generator Gas Gas Purity Alarms Alarms 1. Assume Assume Air Air is the the Conta Contamin minant ant

Please read the warnings concerning hydrogen contamination as provided in the beginning of this document. document. In particular particular,, the contaminant contaminant is assumed to be air unless there is a reason to suspect pure oxygen may be introduced. A condition to suspect pure oxygen is if the hydrogen source is a hydrogen generation device. 2. Explos Explosion ion Danger Danger

Low purity is a concern primarily because of the hydrogen explosion danger. 3. Eff Effect ect of Low Low Purit Purity y in Casin Casing g Gas

Low purity gas in the casing will slightly raise generator winding temperatures because air has a relati relativel vely y low therma thermall conduc conductiv tivity ity (about (about a tenth tenth that that of hydrog hydrogen’ en’s) s) and air forms forms larger larger bounda boundary ry layer thickness thickness which reduces reduces convectio convection. n. Also, Also, air in the generator generator casing casing increases windage windage losses and noise. Most generators have fan differential pressure indicators, which will be reading noticeably high if the generator casing gas purity is below 90%. 4. Gas Puri Purity ty Readi Reading ng has has a Time Time Lag

There is a time lag between the generator gas purity change and the monitoring of that change due to the volume of gas in the interconnecting piping and the Àow rate through that piping, as well as contaminate diffusion which will occur in the piping. Given the Àow rate, pipe size and length, gas pressure ratioed to ambient, and a factor of 2 to account for diffusion, the operator can calculate the time lag. For example, a sensing line of 50 feet of pipe 0.5 inch diameter and a generator pressure of 60 psig with a gas Àow rate of 2 scfh will have a time lag of 2 * 50 feet * (0.25 * pi * 0.5 * 0.5) in2 * (74.7 psia / 14.7 psia) * X / 2 scfh = 21 minutes X = unit conversion factors (therefore X = 1) For example, a sensing line of 15.24 meters of pipe 12.7 mm diameter and a generator pressure of 414 kPa–g (4.22 kg/cm 2) with a gas Àow rate of 944 ml/minute will have a time lag of 2 * 15.24 m * (0.25 * pi * 12.7 * 12.7) mm2 * (414 + 101.4 / 101.4) * X / 944 ml/min = 21 minutes X = unit conversion factors (therefore X = 1) Therefore, while troubleshooting, the operator should remember that the purity reading is not current.

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5. Non–Vacuum Non–Vacuum Treat Treated ed Seal Oil Oil Systems Systems

If there is a purity–low–alarm in an end cavity (not the generator casing), the rate of scavenging should should be increased increased to reestablish reestablish the desired set point reading. If purity cannot be maintained maintained between the desired set point and the low–alarm and if scavenging is at a maximum, then the generator should be shut–down and the source of the contamination contamination identi¿ed and corrected. Do not operate the generator for more than a few minutes with purity less than the low–low–alarm point. 6. Vacuum Treat Treated ed Seal Oil Systems Systems

Systems with vacuum treated seal oil are not susceptible to contamination in the end cavities and therefore do not require scavenging from the drain enlargements. It is possible that the gas purity monito monitorin ring g equipm equipment ent will will only only sample sample gas from from the genera generator tor casing casing.. The desire desired d set point point of gengenerator casing gas will be very high, approximately 95-98% and will not be adjustable because there is no scavenging. scavenging. The low–alarm point initiates initiates operator operator investigati investigation on and the low–low– low–low–alarm alarm point would be used to advise the operator to shut down the generator. generator. If the vacuum treatment processing of the seal oil is being bypassed or is inoperative, then the operator operator will have to scavenge scavenge gas from the seal oil drain enlargements enlargements.. 35 standard standard cubic feet 3 3 3 (1 m ) (about 1/6 of a bottle), (17.5 ft3 (0.5 m ) TE and 17.5 ft (0.5 m ) CE), of gas should be scavenged every hour. 7. Sources Sources of Contaminat Contamination ion

Possible sources of contamination of the end cavity gas are (a) excessive seal oil Àow, (b) poor seal oil draining, (c) insuf¿cient scavenging, and (d) excessive air in the seal oil supply. The low purity in the casing may be due to a leaky CO 2 valve. CO 2 valves often corrode due to an interaction of CO 2 with humidity causing an acid to form, and so are susceptible to internal leaks. Moisture in the gas analyzer probe may cause erroneous readings. An alumina moisture indicator should be upstream of the gas analyzer probe, and will warn of moisture contamination. Moisture Moisture is often removed removed from the gas sample by a molecular sieve ¿lter. ¿lter. This special special type of ¿lter traps carbon dioxide and bleeds it out over a day or so. Therefore, if the carbon dioxide from the purge operation was inadvertently routed to the ¿lter, then the reading will erroneously show low purity for about a day. B. Generator Generator Gas Temper Temperature ature High High

If the generator casing gas temperature is too high there is a possibility of damage to the winding insulation insulation.. The generator generator casing gas temperature temperature alarm is part of the generator generator equipment, equipment, and not part of the hydrogen gas system. Typically the alarm point is 2°C (3.5°F) above normal operating gas temper temperatu ature. re. After After the alarm, alarm, coolin cooling g water water Àow should should be increa increased sed,, or other other action action taken taken immedi immediate ately ly to lower the gas temperature. If the cause cannot be immediately corrected, the load on the generator should be reduced until the normal gas temperature is obtained. C. Generator Generator Gas Gas Pressur Pressuree High

The generator generator gas pressure pressure is maintained maintained by a control control valve in the gas control valve assembly assembly.. If the control valve is found to be non–adjustable or otherwise malfunctioned, it can be isolated and repaired.


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The generator can continue to operate with hydrogen being periodically provided through the bypass valve valve around around the contro controll valve. valve. Alterna Alternativ tively ely,, if a two–st two–stage age pressu pressure re regula regulator tor is provid provided ed on the bottle bottle manifold, that regulator can be adjusted and used to control generator gas pressure temporarily. The primary concern with high generator gas pressure is that it will rise above the capability of the seal oil system. By system design, this situation is unlikely. unlikely. D. Generator Generator Gas Gas Pressur Pressuree Low

A low low gene genera rato torr gas gas pres pressu sure re of only only a few few psi psi (sev (sever eral al kPa, kPa, seve severa rall hund hundre redt dth’ h’ss of a kg/c kg/cm m 2) will will caus causee several degrees C of elevated temperature in the rotor windings. Therefore it is important to reestablish nominal generator gas pressure or else reduce load after a low generator gas pressure alarm. The generator pressure low alarm should be set within 2 psi (13.8 kPa, 0.14 kg/cm 2) below nominal nominal generator gas pressure. The generator generator gas pressure is maintained maintained by a control control valve in the gas control control valve assembly. assembly. If the control valve is found to be non–adjustable or otherwise malfunctioned, it can be isolated and repaired. The generator can continue to operate with hydrogen being periodically provided through the bypass valve valve around around the contro controll valve. valve. Alterna Alternativ tively ely,, if a two–st two–stage age pressu pressure re regula regulator tor is provid provided ed on the bottle bottle manifold, that regulator can be adjusted and used to control generator gas pressure temporarily. The other likely cause of a gradual lowering of generator gas pressure is low hydrogen supply pressure or an extremely leaky vent valve. If the pressure is dropping rapidly, the cause is possibly a failed open relief valve, a shaft seal failure, a casing or pipe failure, failure, or a failed failed open Àoat trap valve in the seal oil drain system. system. In case there is a rupture of hydrogen containment, the generator should be shutdown immediately, and it should be determined that the area is free of H 2 or CO2 hazards before an operator approaches or enters the equipment. equipment. Generators Generators with autopurg autopurgee feature will put CO 2 into the generator generator automatically automatically.. The concentrat concentrations ions of hydrogen in air, which are explosive explosive,, are between 5% and 75% hydrogen. hydrogen. During During this emergency period, while the generator is still charged with hydrogen, the seal oil system should be operating, in spite of the fact it may be pumping oil into the generator. generator. As the pressure drops below 15 psig of CO 2 or air, if it is possible possible to do so, the Àoat trap bypass valve should should be opened. As the pressure of CO 2 or air drops below 2 psig, the seal oil system should be shut down. E. Hydrogen Hydrogen Supply Supply Pressur Pressuree Low

An indication of low hydrogen supply pressure is provided so that the operator can be prompted to replace depleted hydrogen bottles and avoid the more critical event of a low generator gas pressure alarm. F. Liquid Liquid Detection Detection

Liquid inside the generator indicates that there is an oil or water leak, or else the seal oil drain is backed up. Liquid oil and oil vapor (which easily condenses) create a sticky surface on the generator internal surfaces including including the insulatio insulation. n. Dirt particles particles then have a tendency tendency to cling cling to the insulatio insulation n and may eventually damage it. Liquid water on the insulation will degrade the quality of the insulation.

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A High Generator Liquid Detection Alarm may indicate a slow leak of liquid into the generator casing which should be investigated when convenient. A slow leak of oil is possible due to the interaction of seal oil with rotor rotation while on turning gear. A fast leak is evident if there is a High–High Generator Liquid Detection Alarm. The fast leak should be immediately identi¿ed and corrected, or else the generator should be shut down prior to generator casing Àooding. A High Seal Oil Drain Enlargement Liquid Detection Alarm is provided so that the operator will know the reason for an impending High Generator Liquid Detection Alarm and can take proper corrective action. 1. Invest Investiga igatio tion n

After an alarm, the liquid detection device can be drained to determine if the liquid is water or oil. 2. Water ater

There are two sources sources of water: The hydrogen hydrogen coolers and the stator stator cooling water system (if the armature bars are direct water cooled). A recent abnormal requirement for make–up water for the stator cooling water system indicates a possible leak. To determine if a hydrogen cooler is leaking, valves on the underside of the generator may be intermittently closed and opened. Also the operator could shut off the Àow of water to one cooler at a time if running at 80% of rated load capacity. capacity. If a cooler cooler leak is severe, severe, the defective defective cooler cooler may be left out of service until repairs can be made. Generators are typically designed to operate at rated power factor at 80% rated load capacity with one hydrogen cooler out of service. The hydrogen gas dryer, if provided, does not have the capability to dry the generator if there is a generator internal water leak. 3. Oil

Oil may enter the generator from the shaft seals or else from Àooding of the hydrogen detraining tank. Do not shut down the seal oil supply until after H 2 has been purged out of the generator with CO 2. Oil may be Àowing quickly into the detector during the purging process. During the generator gas purge process, draining seal oil may have a tendency to back up in the drain system if the generator pressure becomes abnormally low. A bypass valve is typically provided so that an operator can increase the drain Àow rate. Oil from the shaft seal area may be due to a leaky Àange, or an extremely large seal oil Àow, or anothe anotherr proble problem. m. It can be isola isolated ted to be eithe eitherr the turb turbine ine end end or the coll collect ector or end by interm intermitt ittent ently ly closing the drain valves located near the end shield on either side of the underside of the generator. Shaft seals may become unseated if there is a temporary reversal of pressure on the gas side seal ring. This may occur during during a transfer transfer from one seal oil supply pump to another, another, either either due to a


33

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time time lag lag betw betwee een n pump pump stop stop and and star startt or due due to a time time lag lag in the the pres pressu sure re cont contro roll valv valvee resp respon onse se.. An unseated seal may cause an extremely large oil Àow, which might not drain through the generator’s internal internal drains to the seal oil drain enlargement enlargement.. This event is more typical typical when the shaft is not turning. turning. Field experienc experiencee has shown that the seals often re–seat after several minutes minutes when the shaft is rotated at turning gear speed. VII. VII. MAINTE MAINTENAN NANCE CE A. Leak Testing esting

After a joint has been adjusted or otherwise loosened or tightened, such as after a component is re placed, the joint must be pressure tested to ensure it will not leak hydrogen. Testing may be performed with air or CO 2, typically at approximately 20 psig (14 kPa–g, 0.14 kg/cm 2). Leaks can be identi¿ed by applying a soapy solution to the joints and welds. A typical solution would be liquid soap, glycerin and water. water. Bubbling will indicate leakage. B. Regular Regular Maintenanc Maintenancee

An operator should be available in the control room to receive alarms at all times. Each mechanism in the gas control system should be inspected periodically to ensure it is functioning properly. properly. 1. Daily Daily Inspec Inspectio tions ns

Once a day the operator should review the transmitter signals from the gas system and compare them them with with standa standard rd values values.. The standa standard rd values values will will be establ establish ished ed from from previo previous us operat operation ion experi experi-ence. Also the transmitter signals should be compared with the previous days’ readings to identify any trends. The gas control system transmitter signals signals are: Generator Gas Pressure Generator Gas Purity Core Monitor (Not provided with all generators) Hygrometers (Not provided with all generators) Once a day the operator should walk around the gas system equipment to look for anything abnormal. The gas control system system features to be daily inspected inspected are: All valves should be in the proper position Check the sight glass in the gas dryer (if a gas dryer is provided and it has a sight glass) Compare the reading on all the pressure gauges with standard values Hydrogen control cabinet settings and indicators should be normal. Core monitor and pyrolysate collector should be operating normally (if provided with generator)

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Check the sight glass in both liquid detectors and the seal oil drain system Àoat trap Drain condensate or other liquid out of the main vent line 2. Weekly Inspection Inspectionss

Visually inspect the moisture indicators (MI-2971, MI-2972, and MI-2973). A blue medium indicates dry hydrogen, while a pink medium indicates excessive moisture in the hydrogen gas sample that may affect the stability of the Generator Gas Analyzers (GGA). Replace or regenerate the Moisture Indicator and replace the Gas Puri¿er if the medium is pink. Refer to Removal of Moisture Indicators Indicators and Gas Puri¿ers. Puri¿ers. Blow down puri¿ers puri¿ers by ¿rst removing removing cap at the base of the isolation valve and then open the valve itself. It is advisable to have a container available to collect any Àuid contained within the puri¿er. Please refer to the provided Hydrogen Control Panel Operation and Maintenance manual for further details covering how to perform maintenance activities. CAUTION

The Puri¿ers May Contain Hydrogen Gas; Use Proper Safety Precautions 3. Inspection Inspectionss Every Every Six Months Months

Calibrate or otherwise perform maintenance on the hydrogen control cabinet as required. Perform a Core Monitor system test. (Core Monitor is not provided with all generators). Check the calibration and operation of all the alarm devices and contacts. 4. Inspection Inspectionss to be Done After After Every Schedule Scheduled d Purge with with Carbon Dioxid Dioxidee

Check all drip legs and other drains for liquid accumulation accumulation.. If the generator generator is purged purged with air, close isolation isolation valves in piping piping at the generator generator and elsewhere to prevent prevent humid humid atmospheri atmosphericc air from entering the piping. 5. Generator Generator Maintenance Maintenance Outage Outage

Test all the relief valves for a possible leakage into the vent lines. All gauges should be calibrated every three years minimum. C. Special Special Maintenance Maintenance 1. Gas System System Component Componentss Designed Designed for Maintenan Maintenance ce Activity Activity

Tag all valves, switches, or other devices, which are important to be in a particular state during the maintenance duration. Do not disable the CO 2 supply supply system at anytime anytime for maintenance. maintenance. CO 2 must be continuously available for an emergency purge. Read the warnings concerning concerning hydrogen hydrogen which are at the beginning beginning of this document. The following gas system Àuid processing components have been designed for maintenance while the generator is operating normally: © General Electric Company, 2008. GE Proprietary Information. All Rights Reserved. 47 of 56

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Hydrogen supply pressure sensing devices Generator gas pressure sensing devices Pressure Regulating Valve Pressure Relief Valves Liquid Level Detectors Core Monitor (Not provided with all generators) Gas Dryer (if a gas dryer is provided) Hygrometer Probes (if provided) Hydrogen control cabinet (short duration only) Because there are no compressed air sources permitted to be connected to the generator, it is unlikely that a fast air contamination of the generator gas can occur. Therefore the hydrogen control cabinet can be isolated for a short duration for simple maintenance activity (for example, changing the ¿lter cartridge). D. If the Hydrogen Hydrogen Control Control Cabinet Cabinet is Flooded with Oil or Water Water

If the generator is Àooded with oil or water, then there is the possibility that the hydrogen cabinet may also have been Àooded. After a Àooding accident, all the tubing and components of the hydrogen cabinet should be cleaned and dried. Oil Àooding Àooding will require require cleaning with alcohol alcohol or similar solvent solvent (not methanol methanol CH3OH because it deteriorates elastomeric seals). This will require some dis–assembly at tubing and NPT joints. The ¿lter–dryer cartridges will have to be replaced. The silica–gel will have to be replaced if it was contamina contaminated ted with oil. The cell blocks blocks will have have to be removed removed and Àushed Àushed with alcohol alcohol to remove oil from inside the thermister chamber. The cleaning should extend at least back to the last drip leg in the piping. E. Materials Materials and and Design Design Conditio Conditions ns

The The gas gas syst system em pipi piping ng and and comp compon onen ents ts are are made made of AS ASTM TM A105 A105/A /A10 106 6 carb carbon on stee steel, l, AISI AISI 304/304L/316/316L stainless steel, or bronze. The design pressure pressure of the piping and assemblies assemblies is 150 psig (1034 kPa–g, kPa–g, 10.55 kg/cm2). Bottle Bottle manifolds are designed to a higher pressure. VIII. VIII. OPERATION OPERATION AND AND DESIGN DESIGN REQUIREMEN REQUIREMENTS TS FOR THE H2 AND CO2 GAS SUPPLIES

The gas system equipment supplied with the generator does not include the H 2 and CO2 gas storage equipment nor the piping to connect the gas storage equipment to the gas system gas control valves. This equipment is not provided because there are many alternative gas storage systems available to the power plant designers and they should choose one, which best ¿ts their needs.

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The following following section section gives instructions instructions on the design design of the gas storage equipment equipment and piping. piping. It also provides instructions to operators on how to use equipment, which is designed to these requirements. A. Requirements Requirements on on Gas used in in the Generator Generator

The The sour source cess of gas gas shou should ld be able able to prov provid idee gas gas to the the gas gas cont contro roll valv valves es to the the foll follow owin ing g requi require reme ment nts: s: 1. Carbon Carbon Dioxid Dioxidee

Phase: Vapor Phase. This includes the emergency event of a loss of AC power. Purity: Commercially available purity grade. Flow rate: 120 scfm (3.4 s m3/min) m3/min) for a 2800 ft3 (80 m3) generator. generator. Flow rate changes changes proporproportionally with generator volume. Pressu Pressure: re: 125 psig psig +/-10 +/-10 psig psig (861.8 (861.8 kPa-g kPa-g +/- 68.9 68.9 kPa-g kPa-g or 8.79 8.79 kg/cm kg/cm 2 +/- 0.70 0.70 kg/cm kg/cm2) (betwe (between en the pressure reducing valve and the CO 2 Àow ori¿ce). The CO 2 pressure at customer connection LE049 shall be approximately 2 psig (13.8 kPa–g, 0.14 kg/cm 2) as determined by the generator internal pressure. Temperature: Low temperatures are acceptable. Gas Quantity: There should be enough carbon dioxide available for an operator to purge the generator of hydrogen during an emergency. Bottles should be stored near the manifold. The Àow rate and pressure requirements can be satis¿ed by the use of an ori¿ce when designed to the design requirements given below. Please note ori¿ce is already provided for CO 2 gas Àowing from the GE designed CO 2 bottle manifold system. 2. Hydr Hydrog ogen en

Purity: 99.9% or better.(note that hydrogen manufactured from some processes may contain measurable hydrogen sul¿de and should not be utilized) Humidity: Humidity: maximum maximum of 0.1 gram of water per cubic meter of gas (0.00007 (0.00007 lbm/ft3) (Gas should should be desiccant dried.) Flow rate: 50 scfm (1.4 s m 3/min) during purging for a 2800 ft3 (80 m 3) generator. generator. Higher Higher Àow rates are permitted permitted during the generator ¿ll operation. operation. The gas Àow rates in feed pipes shall be limited to 300 feet per second maximum. Pressure: 125psig +/-10 psig (861.8 kPa-g +/- 68.9 kPa-g or 8.79 kg/cm 2 +/- 0.70 kg/cm 2) during purging and normal operation. During the generator ¿ll operation the gas control valves have no Àow restriction smaller than a 1 inch (25.4 mm) diameter pipe, so the pressure downstream of PCV-2935 will be between 2 psig (13.8 kPa–g, 0.14 kg/cm 2) and full generator gas pressure as determined by generator internal pressure. Temperature: Low temperatures as experienced during the discharge of bottles are acceptable.


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3. Air

Humidity: Air should be desiccant dried. Cleanline Cleanliness: ss: Air should be ¿ltered. No oil vapor is permitted. permitted. Flow rate: No upper limit on Àow rate. Maximum Maximum Àow rate based on the pipe size restricti restriction on is expected to be 150 scfm (4.2 m 3 /min) Pressure: Pressure: Approximat Approximately ely 2 psig (13.8 kPa–g, 0.14 kg/cm kg/cm 2) as determined determined by generator generator pressure. pressure. The gas valve piping has no Àow restriction smaller than 1 inch (25.4 mm) diameter pipe. Temperature: Should be between -20 and 120°F (-28.9 to 48.9°C). Gas Quantity: Several generator volumes of gas will be necessary to purge the generator. B. Characteri Characteristics stics of of Compressed Compressed Gas Gas

It is important that the operator become familiar with the behavior of compressed hydrogen and carbon dioxide. Compressed Compressed gas is dangerous. dangerous. Be cautious cautious when using compressed compressed gas. gas. Be alert to kinked Àexible Àexible pigtails, especially at the ¿ttings, and to over–stressed metal tubing–type pigtails. Replace damaged pigtails immediately. Be cautious of high pressure gauges by minimizing the amount of time an operator stands in front of them. Read all warnings provided by the gas supplier. 1. Gas Bottle Bottless and and Regula Regulator torss Regulators

Connecting Connecting Bottles: Bottles: Prior to attaching attaching a bottle, bottle, the the dirt dirt and and dust in the valve valve outlet outlet and in in the pigta pigtail il ¿tting ¿tting should be completely completely removed. removed. Dirt in a pressure pressure regulator regulator will cause it to leak internally internally when it should have a tight shut off. Slowly Open Valve. Valve. Bottle pressure should be applied to a pressure regulator by slowly opening the bottle’s hand valve. This avoids damage to the regulator or a gauge by a pressure shock. Replace Leaky Valve Valve Seats. If the pressure downstream of the pressure regulator increases when there is no Àow, then the pressure pressure regulator regulator valve seat may leak. The seat should should be replaced replaced if it leaks. leaks. If the pressure pressure at the gas control control valve assembly assembly is at the pressure pressure relief valve setting, setting, then the seat of the pressure regulator is likely leaking. Low Flow Delivery Delivery Pressure. Pressure. Single Single stage regulators regulators (which (which have more Àow capacity than two stage regulators) have their delivery pressure set point established at a high Àow rate. During low or no Àow, the delivery pressure set point is much higher. Therefore, if the gas system is designed so that a tight shut–off is necessary (ie, the manifold globe valves are open in a “ready” mode), then the low or no Àow delivery pressure should be deliberately set below the gas system relief valve setting. Otherwise, the gas from the bottles will seep out the relief valve and not be available when needed.

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H2 Bottles

Hydrogen bottle size: 239 standard cubic feet (6.77 m 3) per bottle (about 200 ft3 (5.7 m 3) is usable because the pressure drops off during discharge). At 70° F (21°C) the pressure is 2400 psig (16.5 MPa, 169 kg/cm 2). Minimize Number of Active H2 Bottles. For safety reasons, as few bottles of hydrogen as possible should be used during any one time during normal operation. Do Not “Crack” “Crack” Hydrogen Hydrogen Bottles: Bottles: Unlike Unlike non–Àammable non–Àammable gasses, it is not recommende recommended d to “crack” hydrogen bottles prior to connecting them to a regulator of manifold since “self–ignition” of the released hydrogen is likely to occur. CO2 Bottles

Use Gaseous CO 2 Only. Only. Only bottles which discharge the vapor phase of carbon dioxide should be used. Bottles which have a siphon tube so that they discharge liquid, or bottles with the discharge port on the bottom so that they discharge liquid, are not to be used with the generator. generator. Liquid carbon carbon dioxide is extremely extremely cold and may adversely adversely affect the welds in the piping. Also, Also, it will easily form solid carbon dioxide after dropping in pressure in a Àow restriction and potentially block the piping. Carbon dioxide bottle size: 50 lbm (50 pounds mass, 22.7 kg) of gas per bottle. At 70°F (21.1°C) the pressure is 850 psig (5.86 MPa, 59.8 kg/cm 2) and the contents is about 45 lbm (20.4 kg) liquid and 5 lbm (2.3 kg) gas. At 110°F (43.3°C) a full CO 2 bottle will have 1800 psig (12.4 MPa, 127 kg/cm2) of pressure, at 140°F (60°C), 2600 psig (17.9 MPa, 183 kg/cm 2). The pressure pressure inside inside a carbon dioxide bottle decreases during discharge because the evaporating liquid cools the bottle contents, thus lowering the vapor pressure. Usable CO2 — Freezing. A 50 lbm (22.7 kg) bottle has 435 standard standard cubic feet (12.3 m 3) of gas. However, However, the CO C O 2 may freeze freeze during the the bottle bottle discharg discharge. e. A portion portion of the content contentss in a CO 2 bottle will be liquid for bottle pressures between approximately 60 psig (414 kPa–g, 4.22 kg/cm 2) and 1050 psig (7.24 MPa, 73.9 kg/cm 2). During During a bottle bottle discharge, discharge, the Àuid contents contents at 60 psig (414 2 kPa, 4.22 kg/cm ) will be at approximately -56° C (-68.7°F). As gas continues to be depleted from the bottle, the liquid will transform into a solid. Bottles initially at 30° F (-1°C) will discharge only 63% of their contents; bottles initially at 110°F (43.3°C) (43.3°C) will discharge discharge only 85% of their contents. contents. The relationshi relationship p between available available % and initial temperature is approximately linear (a mid point is 73% at 70° F (21°C)). Bottles which are disconnected from the manifold will not continue to discharge their gas to the generator as they warm up. Therefore, in systems with all the CO 2 bottles connected to bottle manifold connections, the bottle freezing phenomena has less of an effect. Bottles Bottles which are partially partially depleted depleted will return to the full bottle pressure pressure of 850 psig (5.86 MPa, 2 59.8 kg/cm ) at 70°F (21° C) after they warm up if they have about 30% or more of the CO 2 still inside.


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C. Carbon Carbon Dioxide Dioxide in Pipes and Valve Valvess

During the purge step of admitting CO 2 to the generator, the carbon dioxide should go through two stages of pressure drop. The ¿rst is through a pressure regulator, the second is through an ori¿ce. The two two coul could d be comb combin ined ed into into one one ori¿ ori¿ce ce,, but but Àow Àow rate rate woul would d then then vary vary cons consid ider erab ably ly with with bott bottle le pres pressu sure re.. CO2 Feed Piping Should Have a Region Where Solid CO 2 Can Form. Carbon dioxide will form solid precipitation as it goes through a Àow restriction (such as a valve or ori¿ce) if the pressure on the discharge of the restriction is below approximately 60 psig (414 kPa, 4.22 kg/cm 2) and the gas is cold, such as during the second half of a bottle discharge. Therefore the piping should be designed to accommodate a build–up of solid carbon dioxide and operating procedures should be set up to periodically vaporize it by admitting warm CO 2 or heat from another source. The ori¿ce which regulates carbon dioxide Àow rate should be designed so that the precipitation accumulates mulates in a large diameter pipe. The large diameter diameter pipe provides provides surface surface for heat transfer transfer from the ambient environment and will greatly extend the time before the solid carbon dioxide accumulation restricts Àow rate. Precipitation should not be directed into a globe valve or small diameter pipe elbow. A well designed system will accommodate solid CO 2 accumulation without forming a blockage if the operators simultaneously open all the CO 2 bottles which are connected to manifolds. If there is a pressure regulator on the bottle manifold, then it should be designed to have a discharge pressure substantially higher than 60 psig (414 kPa–g, 4.22 kg/cm 2), such as 100 psig (690 kPa–g, 7.0 kg/cm2) or 125 psig (862 kPa–g, 8.79 kg/cm 2). In addition, addition, it should have have a Àow rate capacity capacity (in scfm’s) greater than the Àow rate expected through the ori¿ce. If it does not have a high enough Àow rate capacity, then it will not pass enough Àow to maintain the 100 psig (690 kPa–g, 7.0 kg/cm2) or 125 psig (862 kPa–g, 8.79 kg/cm 2), and there will be a possibility of solid CO 2 accumulating in the small bore piping immediately downstream downstream of the pressure regulator. More than one bottle manifold pressure regulator can feed the ori¿ce which regulates carbon dioxide Àow rate. See regulator sizing instructions below. below. Vaporizing Solid CO 2 Blockage. Blockage. If the operator experiences experiences blockage blockage due to solid solid carbon dioxide dioxide build–up in the piping, there are several methods of vaporizing it. 1. More Bottles Simultaneously Simultaneously to Avoid Rapid Boiling of CO 2. Bottles which discharge too quickly will have rapid boiling boiling inside the bottle. The rapid boiling boiling causes foam and splatter splatter which will transport transport liquid liquid to the top of the bottle. bottle. If it is suspected suspected that some liquid is being being discharged discharged from the bottle, then more bottles should be discharged simultaneously simultaneously.. By having more bottles discharge simultaneously, they each will discharge more slowly, and the boiling will not be so rapid. 2. Less Bottles Simultaneously Simultaneously to Periodically Vaporize Vaporize Solid CO 2 Build–Up. If blockage is due to solid carbon dioxide forming after a Àow restriction, then less bottles should be discharged simultaneously taneously.. For example, example, if the blockage occurs occurs during the last few minutes minutes of ¿ve bottles bottles being discharged, then there will be less blockage after four bottles are discharged. When the next four bottles are initially discharged, the relatively warm carbon dioxide will vaporize the solid carbon dioxide, which had accumulated. 3. Heating Pipes With With Water. Water. Water can be dripped onto pipes pipes and valves to provide heat to vaporize solid carbon dioxide.

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CO2 Heaters Heaters May Not Operate Operate In An Emergency Emergency.. Even if the carbon dioxide is being electrically electrically heated, the system and operating procedures should be designed to accommodate solid carbon dioxide precipitation and the operators should be familiar with effects of solid carbon dioxide. The heater may not be available during an emergency situation if the AC electrical power is lost. Optimal CO 2 Storage Storage and Piping Piping Design. The best carbon dioxide supply supply system is one where there are enough carbon dioxide bottles connected for fully purging the generator. The advantages are that (a) the operator operator will not be busy removing removing and installin installing g bottles in the event of an emergency emergency purge, purge, and (b) the full contents of the bottles are available because bottles which have had solid CO 2 form will eventually warm up and discharge their remaining gas. It would also be advantageous if the piping is designed so that all the bottles can be opened simultaneously without the possibility of solid carbon dioxide accumulating to the extent that it blocks the pipe to the generator. D. Sizing Sizing the Carbon Carbon Dioxide Dioxide Flow Flow Ori¿ce

The CO2 ori¿ce should be sized to provide the optimum Àow rate of CO 2 into the generator during the purge process. A Àow rate, which is too high will waste CO 2 because CO 2 will mix with H 2. A Àow rate, which is too low will cause the process to outlast the DC seal oil pump battery life, assuming the purge is being done because of an emergency after AC power is lost. Optimum Àow rate is 120 scfm (4.2 m 3/min) for a 2800 ft3 (80 m 3) generator interior. interior. The optimum Àow rate is approximately proportional to generator volume. The ori¿ce will have an upstream pressure between 115 psig (792.9 kPa–g, 8.09 kg/cm 2) and 135 psig (930.8 kPa–g, 9.5 kg/cm 2) and a downstream pressure between 2 psig (13.8 kPa–g, 0.14 kg/cm 2) and 5 psig (34.5 kPa–g, 0.35 kg/cm 2). Therefore Àow through the ori¿ce is choked (Mach Number = 1), greatly simplifying the calculation. Use the Àow function relationship for choked Àow, which is: mass mass Àow Àow = area area *

(total (total pressu pressure re / sqrt sqrt (tot (total al temper temperatu ature) re) ) * X

X = sqrt sqrt ( k / R ) *

sqrt sqrt ( ( 2 / ( k+1 k+1 ) ) ^ ( ( k+1 k+1 ) / ( k–1 k–1 ) ) )

where

R = 35.04 lbf*ft / lbm*R (0.1889 kJ/kgK) for CO 2

and

k = 1.29 for CO 2

Given average upstream conditions of 125 psig (862 kPa–g, 8.72 kg/cm 2) and -10°F (-23.3°C) and a desired mass Àow rate of 120 scfm ( 4.2 s m 3/min), the effective area of the ori¿ce is 0.0536 in2 (35.0 mm2). “The discharge co–ef¿cient, Cd, for large pressure ratios such as this situation is 0.85 per “The Dynamics and Thermodynamics of Compressible Fluid Flow” by Ascher H. Shapiro (page 100). Actual Area = Effective Area / Cd The The actu actual al area area of 0.06 0.063 3 in2 in2 (42. (42.5 5 mm2) mm2),, the the phys physic ical al diam diamet eter er of the the Àow Àow rest restri rict ctio ion n shou should ld be betw between een 0.283 (7.2 mm). A standard manufacturing tolerance can be applied to the ori¿ce diameter. The calculation method is given so that generators with gas volumes substantially different from 2800 ft3 (80 m 3 can have their ori¿ces custom custom sized. Note that area is proportio proportional nal to Àow and inversely inversely proportional to pressure.


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E. The Hydro Hydrogen gen Flow Flow Ori Ori¿ce

Because hydrogen does not form solid precipitation inside the pipe, the ori¿ce may be in the vicinity of valves. Therefore it is included in the gas control valve assembly, and does not have to be provided by others. F. Sizing the Manifol Manifold d Pressure Pressure Regulator Regulator Valves Valves

The The pres pressu sure re regu regula lato torr valv valves es have have to be size sized d larg largee enou enough gh to pass pass enou enough gh Àow Àow so that that the the down downst stre ream am ori¿ce is the most restrictive component of the circuit, and therefore the ori¿ce is the device which controls controls the Àow rate. This is especially especially critical critical for the CO 2 circui circuit. t. If the the CO 2 manifold pressure regulator valve is too restrictive, then the pressure immediately downstream of the regulator will be below 60 psig (414 kPa–g, 4.22 kg/cm 2) and solid CO 2 precipitation would form in the thin pipe after the bottled CO 2 becomes cold. A typical manifold regulator is the Victor SR–703–ME–996 SR–703–ME–996 (0780–0805). The Victor catalog provides 2 data points for air with 125 psig (862 kPa–g, 8.79 kg/cm 2) delivery pressure: pressure: (50 scfm at 200 psig) 2 (1.4 s m3/min at 1.380 MPa, 14.07 kg/cm ) and (183 scfm at 2000 psig) (5.1 s m 3/min at 13.8 MPa, 140.7 kg/cm 2). The conversion conversion factors factors from the catalog are 0.81 for CO 2 and 3.79 for H 2. Therefore, for CO2, the Àow rates are (40 scfm at 200 psig) (1.1 s m 3/min at 1.380 MPa, 14.07 kg/cm 2) and (150 scfm at 2000 psig) (4.2 s m 3/min at 13.8 MPa, 140.7 kg/cm 2). Given 40 scfm at 200 psig (1.1 s m 3/min at 1.380 MPa, 14.07 kg/cm 2), there would have to be three (3) of this style regulator for 120 scfm (3.4 s m 3min). Below 200 psig psig (1.380 MPa, 14.07 kg/cm 2), some solid CO 2 precipitat precipitation ion may form near the regulator regulator. If only two (2) regulators regulators are used, used, solid solid CO2 precipitation may form with bottle discharge pressures up closer to 400 psig (2.76 MPa, 28.15 kg/cm2). If there is one pressure regulator for each bottle manifold, then the operator should open bottles from each of the manifolds simultaneously, so that all the regulators are in use simultaneously. G. Calculati Calculating ng the Quantity Quantity of of CO2 Bottles Required to Purge a Generator

It is important to have enough gas immediately available for a carbon dioxide purge of the generator of hydrogen. hydrogen. A typical typical CO 2 bottle, when fully charged, has 50 pounds (22.7 kg) of carbon dioxide. When expanded and heated to ambient inside the generator, the typical bottle has 435 cubic feet (12.3 m3) of gas. Of this gas, a fraction, x, is available prior to the bottle being removed from the manifold. If the bottle is not removed, x = 1. The fraction, x, may be less than 1 because of CO 2 which freezes in the bottom of the bottle. Because some mixing of gas will occur during purging, twice the generator worth of bottled CO required to purge out hydrogen.

2

is

# bottles of CO 2 = 2 * generator volume / ( x * volume of gas in a bottle) Example: Example: Therefore, Therefore, for a generator generator of 2800 ft3 (80 m 3) and bottles originally at 32°F (0°C) for which x=0.64, 2*2800 / (0.64*435) = 21 number of bottles of CO 2 are required to be available in the event of an emergency purge.

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H. Calculatin Calculating g the Quantity Quantity of H2 Bottles to Purge and Fill the Generator

The typical H 2 bottle has about 200 cubic feet (5.7 m 3) of usable hydrogen when warmed to ambient temperature temperature inside inside the generator. generator. Because Because some mixing mixing of gas will occur during during purging, purging, twice the generator worth of bottled H 2 is required. # bottles for purging = 2 * generator volume / volume of gas in a bottle Additional bottles of hydrogen are required to pressurize the generator. Conservatively, Conservatively, this quantity is. # bottles for ¿lling = n * generator volume / volume of gas in a bottle where n is chosen from the chart below: generator pressure (psig)

(kPa–g)

(kg/cm2)

1

15

100

1

2

30

200

2

3

45

300

3

4

60

400

4

5

75

500

5

n

¿nal

The total number of hydrogen bottles which should be available prior to putting hydrogen into the generator is # bottles of H2 = # bottles for purging + # bottles for ¿lling Example: Example: To purge and pressurize pressurize a generator generator of 2800 ft3 (80 m 3) to 60 psig (about 400 kPa or 4 2 kg/cm ), there should be 2*2800/200 + 4*2800/200 = 84 number of bottles available.


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GE Energy General Electric Company Company www.gepower.com

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CO2 EE-00100-CO2-002

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