Generator Auxiliary Systems

• Primary Water System

• Seal Oil System

• Gas System

NEED

• Generators cooled with Hydrogen are provided with Seal Oil System.

• To arrest the escape of hydrogen from inside the Generator.

• Shaft seals are provided at both sides (TE/EE) of Generator.

Seal Oil System• The shaft seals are supplied with seal oil from two seal oil circuits 1.Air side seal oil circuit. 2.Hydrogen side oil circuit.

• By dividing into two separate circuits entry of air to hydrogen compartment is kept minimum.

• Vacuum treatment of seal oil and resulting continuous H2 loss is avoided.

• Hydrogen losses between rotating shaft and seal ring is prevented by maintaining a continuous film of oil.

Shaft seal

Seal Ring

• Seal ring is housed inside the seal body which is bolted to end shield.

• Seal ring is free to move in radial direction but is restrained from rotating by use of a pin.

• Oil is supplied to the seal ring at three different pressures.

• Clearance is maintained between seal ring and shaft such that frictional losses are minimized and oil film of sufficient thickness is maintained

Air Side Circuit

Principal components • Seal oil storage tank• Seal oil pump 1• Seal oil pump 2• Stand by seal oil pump• Oil cooler 1• Oil cooler 2• Seal oil filter• Differential pressure valve ‘A1’• Differential pressure valve ‘A2’

Air side circuit

• Pump suction is from SOST.

• Air side seal oil pressure is controlled by differential pressure valve A1.

• When only DC sop is in service DPR A2 comes into service automatically.

• DP=seal oil pressure (AS)-Hydrogen pressure.

Pumps details

Seal oil pump Air side• Kind of pump : screw pump

• Capacity : 258 lpm

• Discharge pressure : 12 ksc

• Rating : 7.5kw/15.6A/415V/1500RPM

DC SOP

• Kind of pump : screw pump

• Capacity :258 lpm

• Discharge pressure :12ksc

• Rating :11kw/220DC/1450rpm/82A

Seal oil filter

• The DP setting to be maintained by the valve is done by corresponding pre loading of main bellows.

• Pre loading is adjusted with a compression spring.

Ring Relief

• To balance the oil and gas pressures acting on the seal ring.

• Oil is forced between seal ring and seal ring housing from air side through annular groove.

• Seal ring is free to adjust its radial position which is important during start up and shut down period.

• It needs to allow axial displacement of shaft which is caused by turbine expansions.

Hydrogen side circuit

Principal Components• Seal oil tank• Seal oil pump• Oil cooler• Oil filter• Differential pressure valve ‘C’• Pressure equalizing valve TE• Pressure equalizing valve EE

H2 SOP

• kind of pump : screw pump

• capacity : 130 lpm

• discharge pressure : 12 ksc

• rating : 4.85kw/10.6A/415V/945 rpm

H2 side circuit

• Pump suction is from SOT.

• SOT level is maintained by two float operated valves.

• Pump discharge pressure is controlled by C valve (DPR).

• Equalizing valves maintain the DP between air side and H2 side seal oil pressures at seals.

Seal Oil Skid

Seal oil drains

• Oil drains from air side of shaft seals discharges to generator bearing space and is returned to MOT via SOST together with bearing oil.

• Oil drained from hydrogen side of shaft seals is discharged to generator pre chambers, from there to SOT.

Pressure Regulation

• Air side seal oil pressure is kept 1.5ksc more the H2 pressure.

• Air side seal oil pressure at shaft seal is kept slightly more(20mbar) than the H2 side seal oil pressure at shaft seal by Equalizing valves.

• H2 SOP discharge pressure is kept 2ksc more than Air side SOP discharge pressure.

DC SOP

DC SOP

H2 SOP