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1
Q

Internal elements of a valve

A

Trim

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2
Q

Define:

Seat

A

Provides seating surface

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3
Q

Define:

Packing

A

Prevents leakage between stem and bonnet

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4
Q

Define:

Bonnet

A

Second principal pressure boundary

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5
Q

What operates the stem and disk?

A

Actuator

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6
Q

Define:

Body

A

Primary pressure boundary and sometimes called the shell

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7
Q

What provides the capability for permitting and prohibiting fluid flow?

A

Disk

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8
Q

What is responsible for positioning the disk?

A

Stem

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9
Q

What is also known as an operator?

A

Handwheel

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10
Q

What supports the actuator?

A

Yoke

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11
Q

For penstock valve shut-off purposes, name 4 types of valves that are used.

A
  • Gate
  • Butterfly
  • Ball
  • Rotary plug and dowel pivot
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12
Q

What is the property of gas that allows it to be stored in a small space?

A

Compressibility

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13
Q

Charles’ law states that if the pressure of a gas is unchanged, its volume will change along with a change in…?

A

Temperature

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14
Q

What heat transfer method is used in a shell tube heat exchanger?

A

Counter flow

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15
Q

Pneumatic cylinders speed control valve should be on the…?

A

Outlet side

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16
Q

How much pressure is required for a force output of 14,000 lbs, if the effective piston is 7 inches in diameter?

A 
A = pi x r2
A = 3.14 x (3.5in)2
A = 38.46 in2

P = F/A
P = 14000 lbs / 38.46 in2
P = 364 psi
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17
Q

In a hydraulic system, what does the relief valve do when pump output is greater than the system design?

A

It opens and allows excess oil to return to the reservoir

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18
Q

An unbalanced vane pump has 9 chambers. Each chamber has a volume of 0.5 inches and it revolves at 1200 rpm. How many gpm will it pump?

A

= (9 chambers) x (0.5 in3) x (1200 rpm)

5400 in3/min
= ———
231 in3/gallon

= 23.37 gpm

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19
Q

If a force of 2500 lbs is applied over an area of 15 in2, what is the pressure per square inch?

A

P = F/A

P = 2500 lbs / 15 in2

P = 166.7 psi

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20
Q

What is the piston area of a 3.75 inch diameter cylinder?

A

A = pi x r2

A = (3.14) x (1.875)2

A = 11.04 in2

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21
Q

What is the absolute pressure of a gauge reading of 127.5 psig?

A

(Gauge reading)+(atm pressure)=absolute pressure

127.5 + 14.7 = 142.2 psia

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22
Q

What are the internal elements of a valve?

A

Collectively referred to as a valve’s trim, it typically includes a disk, seat, and stem

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23
Q

What connects the actuator and disk?

A

The stem. It is also responsible for positioning the disk.

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24
Q

Name 5 types of valves.

A
  • Globe
  • Gate
  • Plug
  • Ball
  • Needle
  • Butterfly
  • Diaphragm / Pinch
  • Check
  • Safety
  • Relief
  • Reducing
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25
Q

What type of valve is not suitable for throttling applications and is prone to vibration in the partially open state?

A

Gate valve

26
Q

What does a butterfly valve need for throttling purposes?

A

A butterfly valve can be secured in intermediate positions, for throttling purposes, by a handle-locking device.

27
Q

What is the purpose of a relief valve?

A

It opens only as necessary to relieve the over-pressure condition and allows excess oil to return to the reservoir.

28
Q

What type of fluid is a relief valve used for?

A

Relief valves are typically used for incompressible fluids such as water or oil.

29
Q

What is the purpose of a siphon breaker?

A

The siphon breaker is designed to increase efficiency of the pump.

30
Q

Describe the sequence of the siphon breaker.

A
  • Air compressors supply 100 psi control air for opening pneumatic actuators that move the siphon breaker up and down
  • Seal pumps provide seal water to the priming vacuum pumps and the sustaining vacuum pumps
  • The priming vacuum pumps evacuate entrapped air over water in the pipeline during startup
  • The sustaining vacuum pumps continue maintaining a vacuum in the siphon and remove minor bubbles of air evolved or pumped w/ the mainstream water
  • The liquid level sensing electrodes and still well are used to sense water levels for vacuum pump controls.
31
Q

What are some hazards of CO2?

A
  • eye or ear injury
  • loss of balance
  • asphyxiation
  • CO2 will settle at low points of the plant
  • frostbite
32
Q

What are advantages of CO2?

A
  • electrically non conductive
  • inexpensive
  • easy to clean
  • extinguishes fire quickly
  • harmless to equipment
33
Q

List 4 things that service air supplies air to.

A
  • brakes
  • tools
  • pneumatic controls
  • rotary strainer backwash
  • effluent water supply
34
Q

What does cooling water go to?

A
  • thrust tub
  • guide bearing tub
  • pump bearing tub
  • air surface coolers
  • seal water
35
Q

What does “WOG” mean?

A

Water, oil, gas

36
Q

What valve has the highest k factor?

37
Q

On a valve, what does seat mean?

A

Component of the valve that seals off the flow of liquid

38
Q

On a valve, what is the highest steam pressure rating?

A

The WSP (working steam pressure)

39
Q

What is the coupling gallery used for?

A

It protects the plant from possible flooding due to a seismic event with watertight doors and a bypass to the forebay.

40
Q

What does the suction elbow drain?

A
  • suction elbow
  • scroll case
  • pump extension
41
Q

What does the gantry crane do?

A
  • operates the trash rack

- place/remove stop logs

42
Q

Name 5 things that the DC bus distributes power to.

A
  • emergency lighting
  • station service dc bus
  • plant annunciator
  • under voltage relay 27T
  • USA1 swithyard relaying
  • USA2 switchyard relaying
  • emergency lighting control
  • 13.2kV breaker test cabinet
  • CO2 system oil storage room
  • switchgear U1A
  • switchgear U1B
43
Q

Name 6 environmental systems that might be found in the plant.

A
  • HVAC
  • telephone
  • sewage system
  • potable water system
  • elevator
  • call bell
  • lights
44
Q

What is the deluge system of a transformer for?

A

When it senses over-temperature spray release occurs automatically to prevent/suppress a fire

45
Q

True or false

Cooling water is supplied from the afterbay.

46
Q

True or false

Used or dirty oil from the units should be drained to the clean filtered tank in the oil room.

47
Q

True or false

Oil can be gravity drained from the pump bearing, thrust bearing, and lower motor guide bearing.

48
Q

True or false

You should always valve out CO2 before entering the oil room.

49
Q

True or false

The coupling gallery fan should be turned on for 30 seconds before entering.

50
Q

True or false

The purpose of the hot water bypass is to carry water around the discharge valve during the starting process.

51
Q

True or false

The butterfly valve can be used to throttle.

52
Q

What does SEG stand for?

A

Standby emergency generator

53
Q

What device in the plant will automatically backwash when it senses a differential in its pressure?

A

Rotary strainer

54
Q

An air compressor that increases pressure in steps is called what?

A

Multi-stage compressor

55
Q

Where does the water that leaks from equipment drain to?

56
Q

What does the potable water tank supply water to?

A
  • compressors
  • packing boxes
  • transformer deluge
  • fire hydrants
57
Q

What is used to clean oil?

A

Centrifuge

58
Q

What is Northfield criteria used for?

A

Emergency water supply to close the downstream seat

59
Q

What valve is used at the base of dams, releases water from a reservoir, and referred to as a fixed cone dispersion valve?

A

Howell-Bunger blow off valve

60
Q

Describe the operation of the siphon breaker.

A
  • The siphon breaker function is to open and close a port at the top of the siphon
  • Allows a vacuum to be introduced over the pipeline water surface to evacuate entrapped air
  • It opens to atmosphere when the main pump is stopped
  • Closed and introduces a vacuum when pump starts

Plant Auxiliaries (1 decks)

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