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Flashcards in Review Deck (60)
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1

Internal elements of a valve

Trim

2

Define:

Seat

Provides seating surface

3

Define:

Packing

Prevents leakage between stem and bonnet

4

Define:

Bonnet

Second principal pressure boundary

5

What operates the stem and disk?

Actuator

6

Define:

Body

Primary pressure boundary and sometimes called the shell

7

What provides the capability for permitting and prohibiting fluid flow?

Disk

8

What is responsible for positioning the disk?

Stem

9

What is also known as an operator?

Handwheel

10

What supports the actuator?

Yoke

11

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

-Gate
-Butterfly
-Ball
-Rotary plug and dowel pivot

12

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

Compressibility

13

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

Temperature

14

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

Counter flow

15

Pneumatic cylinders speed control valve should be on the...?

Outlet side

16

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

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

17

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

It opens and allows excess oil to return to the reservoir

18

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?

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


5400 in3/min
= ———
231 in3/gallon


= 23.37 gpm

19

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

P = F/A

P = 2500 lbs / 15 in2

P = 166.7 psi

20

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

A = pi x r2

A = (3.14) x (1.875)2

A = 11.04 in2

21

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

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

127.5 + 14.7 = 142.2 psia

22

What are the internal elements of a valve?

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

23

What connects the actuator and disk?

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

24

Name 5 types of valves.

-Globe
-Gate
-Plug
-Ball
-Needle
-Butterfly
-Diaphragm / Pinch
-Check
-Safety
-Relief
-Reducing

25

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

Gate valve

26

What does a butterfly valve need for throttling purposes?

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

27

What is the purpose of a relief valve?

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

28

What type of fluid is a relief valve used for?

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

29

What is the purpose of a siphon breaker?

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

30

Describe the sequence of the siphon breaker.

-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

What are some hazards of CO2?

-eye or ear injury
-loss of balance
-asphyxiation
-CO2 will settle at low points of the plant
-frostbite

32

What are advantages of CO2?

-electrically non conductive
-inexpensive
-easy to clean
-extinguishes fire quickly
-harmless to equipment

33

List 4 things that service air supplies air to.

-brakes
-tools
-pneumatic controls
-rotary strainer backwash
-effluent water supply

34

What does cooling water go to?

-thrust tub
-guide bearing tub
-pump bearing tub
-air surface coolers
-seal water

35

What does “WOG” mean?

Water, oil, gas

36

What valve has the highest k factor?

Globe

37

On a valve, what does seat mean?

Component of the valve that seals off the flow of liquid

38

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

The WSP (working steam pressure)

39

What is the coupling gallery used for?

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

40

What does the suction elbow drain?

-suction elbow
-scroll case
-pump extension

41

What does the gantry crane do?

-operates the trash rack
-place/remove stop logs

42

Name 5 things that the DC bus distributes power to.

-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

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

-HVAC
-telephone
-sewage system
-potable water system
-elevator
-call bell
-lights

44

What is the deluge system of a transformer for?

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

45

True or false

Cooling water is supplied from the afterbay.

False

46

True or false

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

False

47

True or false

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

False

48

True or false

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

True

49

True or false

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

False

50

True or false

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

True

51

True or false

The butterfly valve can be used to throttle.

True

52

What does SEG stand for?

Standby emergency generator

53

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

Rotary strainer

54

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

Multi-stage compressor

55

Where does the water that leaks from equipment drain to?

Sump

56

What does the potable water tank supply water to?

-compressors
-packing boxes
-transformer deluge
-fire hydrants

57

What is used to clean oil?

Centrifuge

58

What is Northfield criteria used for?

Emergency water supply to close the downstream seat

59

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

Howell-Bunger blow off valve

60

Describe the operation of the siphon breaker.

-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