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Plant Auxiliaries > Review > Flashcards

Review Flashcards

(60 cards)

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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
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

Plant Auxiliaries (1 decks)

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