Power Engineering 3B2 - Chapter 2

An electronic-hydraulic governor system uses: a. High pressure oil from the turbine oil system. b. A separate fluid power unit for high pressure oil. c. Oil pressure of approximately 3000-4000 kPa. d. Pressure oil from the turbine oil system and boosts it to approximately 8200-11000 kPa. e. Flyweights similar to a mechanical-hydraulic governor.

B

Back pressure and extraction turbines use _________ in connection with ___________. 1) pressure sensitive governor 2) throttle governing 3) speed sensitive governor 4) by-pass governing a. 1, 2 b. 1, 3 c. 2, 3 d. 3, 4 e. 4, 1

B

If left at a standstill, while the turbine is still hot, the lower half of the rotor will cool off faster than the upper half and the rotor will ______________________ or "hog". a. turn on it's own b. bend upwards c. twist d. bend downwards e. stall

B

In a turbine circuit, feed heaters and deaerators serve to: a. Use up excess steam. b. Increase efficiency. c. Provide load during low demand periods. d. Lighten the load on the condenser. e. Increase turbine output.

B

Oil in a typical turbine lube oil system is supplied to various components at _____ pressure/s. a. 1 b. 2 c. 3 d. 4 e. 5

B

Turbines fall under two general classes, _____ or _____. 1. Condensing. 2. Tandem. 3. Those that exhaust at or above atmospheric pressure. 4. Compound. a. 1, 2 b. 1, 3 c. 1, 4 d. 2, 3 e. 2, 4

B

With _________ a series of nozzle valves opens in sequence as the load increases. This type of governing is most efficient and is used for impulse turbines. a. throttle governing b. nozzle governing c. speed governing d. by-pass governing e. overload governing

B

_________________ is the percent change in speed required for load change equal to the rated. a. Speed governor b. Governor speed drop c. Governor speed increase d. Throttle governing e. Integral band

B

When starting up a turbine it is not necessary to open trap bypasses as the traps will remove condensate as it is produced. a. True b. False

B - This must be done prior to startup

When a hydraulic overspeed trip operates: 1) High pressure oil forces the main steam valve shut 2) High pressure oil supply is shut off 3) The stop valve oil cylinder drain is closed 4) The stop valve oil cylinder drain is opened 5) A spring closes the main steam valve 6) The pilot drain is closed a. 1, 3, 6 b. 2, 4, 5 c. 3, 4, 6 d. 2, 4, 6 e. 3, 4, 5

B

On startup of a large condensing turbine, the cooling water to the oil cooler is turned on: a. Before the jacking oil pump. b. At the same time as the lubricating oil pump. c. When the oil reaches normal operating temperatures. d. When the jacking oil pump is shut down. e. When it is convenient.

C

Overspeed trips: a. Are an optional device on a turbine. b. Are linked to the speed pickup. c. Are independent of the governing system. d. Can be disabled to test critical speeds. e. May be mechanical, hydraulic, or mechanical-hydraulic.

C

Steam that has passed through a turbine may pass directly to: 1. A superheater. 2. A reheater. 3. A feed heater. 4. An economizer. a. 1, 2 b. 3, 4 c. 2, 3 d. 1, 2, 3 e. 2, 3, 4

C

The high-pressure oil system of a typical turbine supplies oil to: a. Bearings. b. Gears. c. Emergency stop valves. d. The oil purifier. e. The auxiliary oil pump.

C

The warm-up time required of a turbine is dependent on: a. How quickly the turbine is required. b. The manufacturer's instructions. c. The size of the turbine. d. The type of turbine. e. Whether the steam is dry or wet.

C

Turbines used to drive auxiliary equipment are usually lubricated by: a. Grease nipples. b. Oil impregnated bushings. c. Ring-oiled bearings. d. Self-lubricated sealed bearings. e. Hand.

C

When starting a large condensing or extraction turbine, the lubricating oil pump is usually started: a. Just before the turbine is rotated. b. One half hour before the turbine is rotated. c. 2-3 hours before the turbine is rotated. d. 6-8 hours before the turbine is rotated. e. The pump is left running at all times.

C

The overspeed trip a turbine is usually set to trip the mechanism when it reaches _____ of operating speed. a. 100%. b. 105%. c. 110%. d. 115%. e. 120%.

C - Book says 10 to 12% above normal operating speed

The jacking oil pump supplies oil at a pressure of _____ kPa. a. 8000. b. 9000. c. 10,000. d. 11,000. e. 12,000.

C - There's a section in the book that says 8,000 to 10,000

When starting a turbine, a speed of 200-300 rpm is maintained for what purpose? a. To allow the barring gear time to disengage. b. To allow the operator time to listen for rubbing or other unusual noises. c. To ensure all controls are functioning. d. To warm up the rotor and casing. e. To ensure the lube oil system is operating correctly.

D

A speed sensitive governor may be: 1. Proportional. 2. Mechanical. 3. Mechanical-hydraulic. 4. Electronic-hydraulic. a. 1, 2 b. 3, 4 c. 1, 2, 3 d. 2, 3, 4 e. 1, 2, 3, 4

D

In a mechanical-hydraulic governor system, what is the purpose of the auxiliary oil pump? a. It provides oil pressure in case of a main pump failure. b. It provides oil pressure to the bearings. c. It provides oil pressure to the governor system. d. It provides oil pressure during start-up of the turbine. e. It boosts the main pump's pressure.

D

In an overspeed trip the spring loaded tripping bolt has a center of gravity: a. Concentric with the shaft b. Towards the nut end of the bolt c. Towards the condenser end of the shaft d. Towards the head end of the bolt e. Towards the centre of the bolt

D

In order to supply oil at two different pressures, a typical turbine lube oil system has: a. One centrifugal pump and one reciprocating positive displacement pump. b. One shaft driven pump comprising both high and low pressure sections. c. One shaft drive high pressure pump and an electric low pressure pump. d. A pressure reducing valve. e. A separate pump for each system.

D

Sealing steam to the turbine glands is admitted ___________ is put in operation. a. before the extraction pump b. before the condenser circulating water pump c. after the air ejector d. after the extraction pump e. after the throttle valve is open

D

The advantage of mechanical-hydraulic governors is: a. No flyweights are required. b. A separate high pressure oil system is not required. c. A low amount of control air is required. d. Mechanical losses are greatly reduced. e. There is no direct linkage to the turbine shaft.

D

The barring gear: a. Is started when the lube oil temperature reaches 35-40C. b. Is started when the jacking oil pump pressure reaches 3000-4000 kPa. c. Is used only when starting a turbine. d. Should disengage and automatically shut down steam admission starts the turbine shaft turning. e. Should be disengaged before turning over the turbine.

D

The jacking oil pump is shut down when the turbine reaches a speed of approximately _____ rpm. a. 5-10 b. 20-30 c. 40-50 d. 50-60 e. 0-80

D

The jacking oil pump supplies lubricating oil to the: a. Side of the bearing b. Top of the bearing c. Center of the shaft d. Bottom of the bearings e. Thrust bearing

D

The main oil pump supplies lubricating oil to the: a. Side of the bearing b. Center of the turbine shaft c. Thrust bearing d. Top of the bearings e. Bottom of the bearings

D

A jacking oil pump is used to: 1. Make slight adjustments to the turbine bearing housings during overhaul to maintain alignment. 2. Supply oil under the shaft of the bearing for a specific time. 3. Supply oil to the bearings under the shaft at all times so lubrication is assured. 4. Supply a low volume of oil at high pressure. a. 1, 2, 3. b. 2, 3, 4. c. 1, 3, 4. d. 3, 4. e. 2, 4.

E

In a back-pressure turbine the governor is _____ sensitive. a. Speed b. Temperature c. Flow d. Time e. Pressure

E

In an/a ____________ , the spring loaded tripping bolt has a center of gravity slightly off the centre of the shaft. a. electric turning gear b. nozzle c. barring gear d. shear pin coupling e. overspeed trip

E

Overload governing is used on ________ turbines. a. small b. impulse c. low pressure d. reaction e. impulse and reaction

E

When shutting down a turbine, the first thing done is: a. Turn off the lube oil cooling water. b. Test the emergency trip. c. Start the auxiliary oil pump. d. Shut off the steam supply. e. Reduce the load to zero.

E

A barring gear turns a turbine over via: a. Reduction gears. b. Direct drive. c. A hydraulic coupling. d. A limited slip clutch. e. A hand operated crank.

A

In a nuclear power station a _____________ supplies heat through a _________ to the working fluid in place of a steam plant boiler. 1) reactor 2) heat exchanger 3) burner 4) pump a. 1, 2 b. 1, 3 c. 3, 2 d. 1, 4 e. 2, 4

A

Lubricating oil for a turbine may: 1. Lubricate bearings. 2. Lubricate gears. 3. Operate throttle valves. 4. Be supplied to a governor. a. 1, 2 b. 3, 4 c. 1, 2, 3 d. 2, 3, 4 e. 1, 2, 3, 4

A

The extraction (condensate) pump is put into operation ______ the ______. 1) before 2) after 3) air ejector 4) jack oil pump 5) condenser circulating water pump a. 1, 3 b. 2, 3 c. 1, 4 d. 1, 5 e. 2, 5

A

The two types of Governors used on steam turbines are: 1) Flow sensitive governor 2) Pressure sensitive governor 3) Temperature sensitive governor 4) Speed sensitive governor a. 2, 4 b. 1, 3 c. 1, 2 d. 3, 4 e. 2, 3

A

Throttle governing uses a single large control valve so when the steam is throttled the _______ , thus increasing turbine efficiency. a. superheat will increase b. superheat will decrease c. pressure will increase d. pressure will stay the same e. temperature will decrease

A

When first starting a turbine, the purpose of admitting only enough steam to turn the turbine over very slowly is to: a. Allow the operator time to listen for rubbing or other unusual noises. b. Eliminate hogging. c. Ensure that the jacking oil system is up to pressure. d. Warm up the turbine. e. Make sure the control room is ready for the turbine.

A

A barring gear consists of an electric motor and several sets of reducing gears to turn the turbine shaft at a low speed. It is used: 1) After stopping a hot turbine to prevent "hogging" 2) Only on small turbine 3) Continually when the turbine is not operating 4) Prior to start-up for approximately 3 hours a. 1, 2, 4 b. 1, 2, 3 c. 1, 4 d. 2, 3 e. 2, 4

C

A simple mechanical governor uses a _____ attached to the end of the turbine shaft. a. Governor. b. Speed pickup. c. Set of weights. d. Gear. e. Pressure sensor.

C

Bypass governing allows: a. Increased load at increased efficiency. b. Decreased load at increased efficiency. c. Increased load at decreased efficiency. d. Decreased load at decreased efficiency. e. No change on load and efficiency.

C

In a nuclear power plant circulating coolant picks up heat in the reactor and rejects it to the _______________ in the steam cycle by means of a heat exchanger. a. hotwell b. condenser c. working fluid d. turbine e. feed pump

C

Nozzle governing is _____ throttle governing. a. Less efficient than b. Required with c. More efficient than d. Mandatory with e. As efficient as

C

A mechanical overspeed trip is designed to _____ in the event of an overspeed condition. a. Prevent the turbine's speed from exceeding 150% of its rated speed. b. Activate an alarm. c. Drop the turbine's load. d. Shut off the turbine's steam supply. e. Throttle the inlet steam.

D

A jacking oil pump is used to: 1) Make slight adjustments to the turbine bearing housings during overhaul to maintain alignment 2) Supply oil to a hydraulic motor for the turning gear 3) Supply oil to the bearings under the shaft at all times so lubrication is assured 4) Supply a high volume of oil at high pressure a. 1, 2, 3 b. 2, 3, 4 c. 1, 3, 4 d. 1, 2, 3, 4 e. None of the above

E - It supplies oil under the bearings but not "at all times." Only before startup. It is shut off when the speed is above 50-60 rpm