4. h2 Cooling & Seal Oil System Stage-2

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4. HYDROGEN COOLING AND SEAL OIL SYSTEM- STAGE II 4.1 GAS SYSTEM  The gas system consists of the following following assemblies: 

CO2  distributor



H2  distributor



Gas dryer



Gas unit

4.2 HYDROGEN DISTRIBUTER  The hydrogen for the generator is supplied from the hydrogen distributor. The hydrogen cylinders are connected to the manifold on the dist distri ribu buto torr. Vale ales s on the the cyli cylind nder er and and al ales es on the the manif anifol old d allo allow w repla replacem cement ent of indi indiidu idual al cylind cylinders ers during during operat operation ion.. The hydro hydrogen gen gas aaila aailable ble in the manifo manifold ld at cylind cylinder er press pressur ure e is passed passed to two parall parallel el-connec connected ted pressu pressurre reduc reducer er combin combinati ations ons for e!pans e!pansion ion to the press pressur ure e re"uired for generator operation. #elief ales on the low-pressure side of  the $rst pressure reducer are connected to an outlet pipe system through which which e!ces e!cess s hydro hydrogen gen is passed passed to the atmosp atmospher here. e. The two press pressur ure e reducers are of identical design. The combination of two reducers ensures a constant pressure een in low or no %ow condition. On the other hand& the arrangement of two combinations allows large "uantities of hydrogen to be reduced in pressure during hydrogen $lling procedure.

4.3 CARBON DIOXIDE DISTRIBUTOR To preent a potentially potentia lly e!plosie mi!ture being formed& hydrogen and air must neer be allowed to come in contact with each other either during charging of hydrogen or scaenging s caenging of hydrogen from the generator. generator. 'n both cases& CO2 is used as an intermediate medium. The CO2 is also supplied in steel cylinders in li"uid state. The arrangement of the CO 2 distributor corresponds corresponds to that of hydrogen distributor. distributor. The li"uid CO2& which is stored under pressure& pressure& is fed to the gas unit ia a shut o( ale. )t the gas unit the li"uid CO2 is eaporated and e!panded in a CO2 apori*er. The heat of apori*ation is supplied to the apori*er electrically. One relief ales each on the high pressure pressure and a low-pressure side protects the pipe system against inadmissible high pressure. pressure.

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+or remoing the CO2 from the generator& a compressed air supply with compressed air $lter is connected to the instrument air system of the power plant. ,nder all conditions of operation e!cept for CO2 purging& the compressed air hose between the $lter and the generator pipe system should be disconnected. This isible brea is to ensure that no air can be admitted into hydrogen $lled generator.

4.4 GAS UNIT +or measuring and checing the gas pressure in the generator& the gas unit is proided with pressure transmitter and one pressure gauge for local measurements. The purity is also measured by a purity meter. This meter system functions only at rated speed.

4.5 GAS DRIER ) small amount of hydrogen circulating in the generator for cooling is passed through a gas drier. The gas inlet and gas outlet pipes of the gas drier are connected at points of the generator with di(erent static heads di(erential fan pressure/ so that the gas is forced through the drier due to the di(erential pressure only. 0rying of hydrogen is ensured by two driers proided with silica gel& which can be reactiated with the help of built-in heaters .The drier consists of gas tight cylindrical body with silica gel in a perforated container at the top. ) heater is proided in the central portion of  the drier& which is completely isolated from hydrogen *one. ) thermostat is embedded which cuts o( supply to the heater at 12 3C& automatically indicating thereby that the drier is ready for reuse. The colour of silica gel can be obsered through two glass widows proide at the top. ) local control cubicle is proided for electrical control of heaters of both the driers. The following lamp indications are proided on the cubicle for each drier. 

Heater on



Heater o( 



#egeneration complete.

4ormally out of two& one drier is in operation while other is in reactiation. The continuous circulation of hydrogen through drier is facilitated by the di(erential pressure created by fan mounted on the generator shaft across which the drier is connected .The hydrogen from inlet connection enters silica gel from bottom and moisture is gien up to the

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silica gel while it passes through. The drier hydrogen is led away to outlet connection from the outer annular space in the drier. 5ilica gel in drier needs reactiation as it becomes saturated with moisture. 5aturation state of silica gel can be seen through glass window at the top/ by its colour& which transforms from blue to pin. 6hen silica gel is saturated& closing inlet ales isolates the drier and other drier is commissioned by opening the respectie ale. +or reactiation of silica gel& heater is switched on and as the temperature goes up& the moisture eaporates and condenses on inside of  the outer cylinder& which tricles down to the bottom of the drier where there is a proision for draining o( the water collected. 6hen the temperature of  the silica gel reaches 123C the thermostat cuts o( the supply to the heater automatically indicating that the drier is ready for re-use. The supply for the heater is 22V ).C. single phase& 76atts.

4.6 TECHNICAL DATA #ated hydrogen pressure inside the generator casing g;cm 2 di(erence in readings of pressure gauges ?G-8 ?G->/ and ?G-B includes the static hand ale of .@ g;cm 2./ b/ 5ITT'4G O+ 0?#V N F The seal oil $lter 5+ is $lled by means of changeoer ale V->=;V->B and the $lter is ented by opening the ent plug. The ).C. seal oil pump is stopped .The 0?#V-F is adDusted by adDusting nut for di(erential pressure of  2.1 g;cm2 di(erence in readings of pressure gauges ?G-8 ?G->/ and ?G-B to obtain seal oil pressure of 1.2 g;cm 2 aboe the gas pressure at generator shaft seals./ 4ormally 0?#V-) ale remains in operation and in case of the failure of pumps and as soon as the di(erential pressure at generator shaft seals drops to 1.2 g;cm2  and the 0?#V-F opens and the oil from goerning oil system %ows to the shaft seals. 0?#V- F is set at alue less by .8 g;cm 2 from the actual set ale of  0?#V-).

4.15 SETTING O# RING RELIE# OIL "RESSURE The ring relief oil pressure is set by means of ales V-22 and V-28 to a alue of .9 g;cm 2 aboe seal oil pressure at shaft seals that is operating alue as read on pressure gauges ?G-9;?G-7 shall be 7.>g;cm 2  with rated gas pressure of 8.9 g;cm2. )ll the contacts for the starting of the standard ).C. seal oil pump& 0C seal oil pump& and annunciations are set. The leel switches at seal oil unit& seal oil storage tan and pre-chambers are checed and adDusted. 'n the seal oil cooler& the cooling water is regulated for maintaining the seal oil temperature below > 3C. The thermostat T5-' is set for >93C.  The seal oil system is thus commissioned.

4.16 TAING SEAL OIL SYSTEM INTO SER%ICE  5eal oil system is re"uired to be taen into serice when the generator is 

 To be $lled with hydrogen or&



 To be $lled with air for the leaage testing.

 The following instructions are to be carried out for starting a system.

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1/ ?rior to starting& it should be ensured that all indicating instruments;deices are ready for operation. 2/ Insure that the seal oil leel is obserable at the leel gauge of intermediate oil tan and sight glass of seal oil tan. 'f not $ll the seal oil according to the instructions gien for commissioning of the seal oil system. 8/ Chec and ensure that the following pressure gauge;?ressure 5witch isolating ales are open. a/ V->7 for pressure gauge at inlet of goerning oil. b/ V-8= for pressure gauge after seal oil pump. c/ V-8B for pressure switch at the outlet of ).C. seal oil pump. d/ V-= for pressure gauge after 0.C. seal oil pump. e/ V-89 for acuum gauge. f/ V-8@ for pressure gauge after duple! $lter. g/ V-77 MV-7= for di(erential pressure switch across duple! $lter. h/ V->9 for pressure gauge for ring relief oil on TI. i/ V-> for pressure gauge for ring relief oil at II.  D/ V->8 MV-=2 for pressure switches for seal oil pressure at TI. / V->> for pressure gauge for seal oil pressure at TI. l/ V->1for pressure gauge for seal oil pressure at II. m/ V->2 M V-=1 for pressure switches seal oil pressure at II. n/ V-@1 for pressure transducer for seal oil pressure at TI. o/ V-B@ for pressure transducer at seal oil pressure at II. >/ Chec and ensure that the following stop ales are open. 'f not& the ales are to be opened in the speci$ed se"uence.

4.17 AT GENERATOR a/ V-99 in $lling pipe.

4.18 AT SEAL OIL UNIT a/ V-8 after 'OT. b/ V-19 before 5OT. c/ V-1 before ).C. 5O?. d/ V-2 before 0.C. 5O?. e/ V-17 before 0?#V - F. f/ V-2 after 0?#V - F.

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g/ V-2= before acuum pump. h/ V-21 after 0?#V - ). i/ V-B after seal oil pumps.  D/ V-1 for ring relief oil. / V-22 for ring relief oil at TI. l/ V-28 for ring relief oil at II. m/ V-81 for seal oil supply at TI. n/ V-82 for seal oil supply at TI. 9/ Chec and ensure whether the following stop ales at seal oil unit& on the impulse lines are open. a/ V-8 gas impulse to 0?#V N F. b/ V-29 oil impulse to 0?#V N F. c/ V-2@ gas impulse to 0?#V N ). d/ V-2> oil impulse to 0?#V N ). 7/ 't is to be checed and ensured that the acuum pump is suciently $lled with special oil 472. =/ The ).C. seal oil pump is to be started. 'n order to aoid the build up of  an e!cessie pressure in the piping system air cushions;locs in the piping must be displaced with the oil ).C. seal oil pump should be started and immediately stopped again until all in cushions hae been positiely remoed from the piping system. 5ubse"uently the pump is to be ept in continuous operation. The following pressure gauges are to be monitored. i.

?G-1 after ).C. seal oil pump.

ii.

?G-2 after duple! seal oil $lter.

iii.

?G-8 for TI seal oil.

i.

?G-> for II seal oil.

B/ 6hen the ).C. seal oil pump is started& the acuum pump and the acuum e!tractor must be started simultaneously. @/ 6hen the oil foam rises aboe the upper edge of oil sight glass in the 5OT V-2= is to be closed and once again V-2= is to be opened on its disappearance. 1/

't is to be checed and ensured that all the oil pressure alues

are normal.

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11/

The interlocs for auto starting of the standby ).C. seal oil pump

and the 0.C. seal oil pump are to be checed. 12/

The gas tightness of 5OT including the connected pipelines and

the ales is to be checed. The alue of the acuum should be between 8 to 1 torr and this should not change for a period of at least 2> hours. 18/

The seal oil coolers are to be ented by opening the ent ale of 

operating cooler until oil emerges. The ent ale is to be closed. The standby cooler is to be brought into serice and the aboe process is to be repeated. 1>/

Foth the seal oil $lters are to be brought into operation and the

$lters are to be ented by opening the ent plugs. On completion of  enting one of the seal oil $lters is to be taen out of serice. 19/

The seal oil $lters are to be checed for contamination& and if 

necessary to be cleaned. The degree of $lter contamination can be seen at the di(erential pressure switch 0?5-1/. 'n case of red indication $lter cleaning will be re"uired. 17/

The seal oil coolers are to be $lled on the waterside and the

coolers are to be ented. 1=/

't is to be checed whether the following ales are open. i.

V->7 pressure gauge for goerning oil.

ii.

V-2 after 0?#V N F ale.

iii.

V-17 Fefore 0?#V N F ale.

i.

V-8 Gas impulse to 0?#V N F.

.

V-29 Oil impulse to 0?#V N F.

i.

V-1@ Goerning oil supply.

't is also to be checed that the $lter 5+ is set for operation. Fy isolating the electric supply to ).C. and 0.C. seal oil pumps& the seal oil supply must be taen oer by the turbine goerning system when the seal oil pressure in the deliery pipe has dropped by .8 g;cm 2. 1B/

't is to be checed whether the seal oil supply is at the normal

operating alue. 'f not& the oil impulse line to 0?#V N F is to be ented/.

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1@/

The seal oil supply is to be changed oer top the main ).C. seal

oil pump. 2/

To bring the ring relief oil into serice& the following al8es are

to be adDusted until the normal operating alues are reached. i.

V-22 for ring relief oil at TI.

ii.

V-28 for ring relief oil at II.

4.19 NOTE$  The $nal adDustment of pressure for ring relief oil can only be made when the generator has been $lled with H2 at rated pressure and the machine is running at rated speed. 21/

6hen the seal oil temperature has reached 83C& the cold water

supply to the serice cooler is to be turned on.

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