Main Turbine Lube Oil

Question 1

State the purpose of the main turbine lube oil system.

Answer 1

1) Provide lube oil to the main turbine and generator bearings
2) provide lube oil to the bearing lift oil pumps
3) supply oil to the generator seal oil system

Question 2

How is the main shaft oil pump driven?

Answer 2

It’s mounted on and powered by the main turbine shaft.

Question 3

Which pump is normally used to supply oil to the suction of the main shaft oil pump?

Answer 3

the booster oil pump that is located in the lube oil reservoir.

Question 4

What drives the booster oil pump?

Answer 4

Oil from the discharge of the main shaft oil pump.

Question 5

What do the booster nozzle and baffler valves do?

Answer 5

Reduce the main shaft oil pump discharge pressure down from 235psig to 190 psig to drive the oil driven turbine that turns the booster oil pump shaft.

Question 6

What does the motor suction pump do?

Answer 6

it supplies oil to the suction of the main shaft oil pump until the turbine shaft reaches 90% of rated speed at which time the main shaft oil pump discharge pressure is high enough to run the booster oil pump turbine.

Question 7

What pressure does the oil header relief valve maintain at turbine centerline?

Answer 7

25psig regardless of system dips or surges

Question 8

What supplies cooling water to the main turbine lube oil coolers?

Answer 8

TC

Question 9

What is the power supply for the emergency lube oil pump?

Answer 9

NK

Question 10

When is the turning gear oil pump used?

Answer 10

it provides bearing oil to the turbine’s bearings while the turbine is on the turning gear or when it’s coming up to speed

Question 11

What will cause the turning gear oil pump to start when it’s in Auto?

Answer 11

Main shaft oil discharge pressure low at 190psig or bearing oil pressure low at 15 psig

Question 12

Where can the test of the auto start function for the turning gear oil pump be performed from?

Answer 12

Two buttons in the control room

Two buttons at the main lube oil reservoir

Question 13

What pump would be used to supply oil to the turbine if there were a turbine trip and a loss of off site power?

Answer 13

The emergency lube oil pump that is powered by NK would be used.

Question 14

What causes the emergency lube oil pump to start if it’s in AUTO?

Answer 14

Main shaft lube oil pressure low at 180psig in CONJUNCTION with Turning gear oil pump low discharge pressure at 15 psig.
Low voltage on the power supply to the turning gear oil pump will also auto start the emergency lube oil pump.

Question 15

Where are the main lube oil coolers?

Answer 15

they are mounted vertically inside the lube oil reservoir with a portion sticking out of the reservoir.

Question 16

How is main lube oil temperature maintained in band?

Answer 16

automatically by a valve on the cooler TC water outlet throttling flow.

Question 17

How can an operator tell if a lube oil cooler is full of oil prior to placing it in service?

Answer 17

By opening the cooler inlet bypass valve for the cooler you want to place on service and observing oil flow from a constant vent on the cooler that can be seen by lifting a hatch on the reservoir.

Question 18

What does the vapor extractor do?

Answer 18

pulls air, oil vapor, hydrogen, and moisture from the main lube oil reservoir through a mist eliminator. This causes some flow of cool air to move through the shaft bearing oil deflectors and prevents the accumulation and carbonization of oil between the deflector teeth and on the turbine shaft.

Question 19

What does the mist eliminator do?

Answer 19

it uses fiberglass filters and a pressure blower to remove oil from the vapor and returns the oil to the OW system.

Question 20

Where is the vapor extractor operated from?

Answer 20

the handswitch at the vapor extractor outside of the turbine building 176’

Question 21

Why are the bearing lift oil pumps used?

Answer 21

to reduce torque requirements of the turning gear motor.

Question 22

How many lift oil pumps are there and where are they located?

Answer 22

8 and they are located by the bearings that they supply oil to.

Question 23

How much does the oil lift pump lift the rotor?

Answer 23

2-5 mils

Question 24

When will the oil lift pumps start in Auto?

Answer 24

when the turning gear oil pump discharge pressure is at least 10psig

Question 25

Which lift oil pumps are interlocked to shut off if the turning gear motor is running and rotor speed < 2 RPM?

Answer 25

7 and #10 to provide sufficient load to stop the turning gear from disengaging.

Question 26

Describe the supply header piping that is located in the vicinity of hot turbine parts.

Answer 26

The supply header piping is enclosed in the drain header piping in case there is a rupture, the oil will spray into the drain piping and back to the sump.

Question 27

In regards to main turbine lube oil, what will cause a turbine trip?

Answer 27

main shaft oil pump discharge pressure less than 100 psig OR bearing header oil pressure less than 12 psig.

Question 28

What are the temperature limits for the journal bearings? the thrust bearing?

Answer 28

journal bearings- NTE 240F

Thrust bearing- NTE 190F

Question 29

What should you do with the turning gear if the lube oil temperature exceeds 110F?

Answer 29

ensure the turning gear is in the “pull to lock” position.

Question 30

What should be done is lube oil is < 102F?

Answer 30

place the turbine on the turning gear.