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Process Design and Safety > Pumps and Valves > Flashcards

Pumps and Valves Flashcards

1
Q

What are the most common types of valves?

A

Control
Pressure Relief
On-off
Check

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2
Q

On-off valves are used for stopping the _____.

A

Flow

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3
Q

On-off valves provide _____ _____ when being closed.

A

tight shutoff

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4
Q

On-off valves provide _____ _____ _____ when fully opened

A

low pressure drops

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5
Q

Most control valves can be used for on-off duty, especially ____ valves

A

ball

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6
Q

_____ valves are often used in of-off service

A

gate

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7
Q

Check valves prevent the _____ of flow

A

reversal

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8
Q

Check valves ____ with forward flow and _____ against reverse flow

A

open;close

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9
Q

What are three types of check valves?

A

lift check
swing check
tilting-disk check

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10
Q

Lift check valves depend on _____ for operation

A

gravity

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11
Q

Lift check work with ______ pressure services

A

high

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12
Q

Swing check valves have a closure member that swings about a _______

A

hinge

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13
Q

Swing check valves are employed along with ____ valves

A

gate

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14
Q

Swing check valves work with ____ fluid velocities

A

low

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15
Q

With Swing Check valves flow reversal is _________

A

infrequent

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16
Q

Tilting-disk check valves have a closure member that rotates about a point between the ______ and the edge of the disc.

A

center

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17
Q

Tilting-disk check valves are _______ loaded

A

spring

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18
Q

Tilting-disk check valves are more _________

A

expensive

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19
Q

Tilting-disk check valves are more difficult to _____.

A

repair

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20
Q

control valves are used to ______ the flow automatically to any desired amount

A

regulate

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21
Q

control valves help with ____ pressure drops

A

high

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22
Q

Name four different control valves.

A

globe
ball
butterfly
plug

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23
Q

Globe valves have a _____ stem motion

A

linear

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24
Q

Globe valves have significant pressure ____

A

drops

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25
Q

globe valves _____ the flow

A

control

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26
Q

globe valves are good at servicing fluids containing no ____

A

solids

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27
Q

ball valves have ______ stem motion

A

rotary

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28
Q

ball valves have _____ friction

A

small

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29
Q

ball valves have a ____ pressure drop

A

small

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30
Q

ball valves have ____ flow capacity

A

high

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31
Q

ball valves provide a ______ shutoff

A

tight

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32
Q

ball valves are well suited for _____ ____ service

A

on-off

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33
Q

ball valves are not good for _______ services

A

throttling

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34
Q

butterfly valves have _____ stem motion

A

rotary

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35
Q

butterfly valves have ____ pressure drop

A

small

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36
Q

butterfly valves can handle ______ flow capacity

A

large

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37
Q

butterfly valves provide good service with fluids with or without ______.

A

solids

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38
Q

Butterfly valves can or cannot handle on-off duty?

A

can

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39
Q

butterfly valves can or cannot handle throttling duty?

A

can

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40
Q

Plug Valves have _____ stem motion

A

rotary

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41
Q

plug valves provide a _____ shutoff

A

tight

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42
Q

______ plug valves can be used to simplify the piping system

A

multiport

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43
Q

Plug valves are well suited for ____ ____ service

A

on-off

44
Q

What happens to temperature when mu jt is postitive

A

decreases

45
Q

what happens to temperature when mu jt is negative

A

increases

46
Q

pressure relief valves operate at pressures below _____

A

10,000 psia

47
Q

Pressure relief valves operate at temperatures below ____

A

1,000 F

48
Q

What are two types of pressure relief valves

A

direct-loaded

pilot operated

49
Q

A positive displacement pump can be what kind?

A

rotary
reciprocating (pistons)
miscellaneous (peristaltic)

50
Q

What are the advantages of a positive displacement pump?

A

self-priming
can work in two directions
can pump liquids with gases for a small amount of time

51
Q

What are the disadvantages of positive displacement pumps?

A

most of them cannot operate with closed discharge

might produce oscillations in discharge

52
Q

Peristaltic Pump is used to move tank to _____

A

tank

53
Q

Peristaltic pumps are used in what industries?

A

food, batch, paper

54
Q

What are some types of centrifugal pumps?

A

volute (shell and simple impeller)
diffuser (diffuser vanes around the impeller)
turbine pump
propeller pump

55
Q

what are some advantages of centrifugal pumps?

A 
low cost - easy maintenance
do not produce a lot of noise
uniform discharge (no oscillations)
56
Q

What are some disadvantages of centrifugal pumps?

A

do not produce large heads (cannot increase pressure a lot)

do not work well with high viscosity fluids

57
Q

You can change the _____ size to modify centrifugal pumps

A

impeller

58
Q

If Hs = Hp, pick the Hs curve close to ______ open, at maximum flow

A

80%

59
Q

Where the Pump Curve and System Curve intersect there is _____ pressure drop and the valve cannot control flow

A

0

60
Q

The head Hs goes up as you _____ the valve

A

close

61
Q

Hs =

A

-[(P4-P3)+(P2-P1)]

62
Q

As the Reynold’s number increases, the _____ losses decrease

A

friction

63
Q

To increase the pressure head, you can ____ the level of the fluid

A

raise

64
Q

efficiencies are ______ of the impeller

A

independent

65
Q

You can select the ______ _____ when selecting a pump.

A

Impeller diameter

66
Q

When selecting a pump you should look at maximum efficiency and that NPSHA ______NPSHR

A

>

67
Q

A large impeller size ______ the pressure drop

A

increases

68
Q

Centrifugal pumps are chose because they can operate in a wider range of what?

A

flowrates

69
Q

Using a positive displacement pump uses more _____ and ______ the fluid.

A

energy; heats

70
Q

What kind of pump give an approximate constant flow?

A

positive displacement

71
Q

Ps is usually what? Suction pressure

A

constant

72
Q

You can increase the discharge pressure by ______ the vertical distance

A

increasing

73
Q

Why do the pump curves decrease?

A

Friction takes over as flow rate increases.

74
Q

You can calculate the suction pressure using what?

A

An energy balance

75
Q

The available net positive suction head must be ______ than the required net positive suction head

A

greater

76
Q

NPSHR is a required value suggested by whom?

A

the manufacturer

77
Q

Pumps will not cavitate if what is positive?

A

NPSHA

78
Q

What is it called when pressure increases inside the pump causing bubbles to collapse?

A

cavitation

79
Q

Cavitation reduces _____ and _____ the pump

A

capacity; damages

80
Q

NPSHA =

A

(Ps/rho gravity) - (Pv/ rho gravity)

81
Q

We want Ps to be _____ than Pv

A

greater

82
Q

If NPSHA is negative the fluid enters the pumps with what?

A

bubbles

83
Q

Total dynamic Head =

A

Pd-Ps

84
Q

Hydraulic horsepower W =

A

(Q*TDH (psi))/(rho gravity)

85
Q

shaft efficiency, aeta =

A

Wh/Wb

86
Q

saft efficiency is always less than 1 because of what?

A

friction losses that transform irreversibly to heat

87
Q

Mechanical Energy Balance is defined as what?

A

Static pressure plus pressure change plus acceleration is equal to the change of work done - friction losses

88
Q

What has rotating gears, lobes, or screws?

A

Rotary pumps

89
Q

Centrifugal pumps do not have large what?

A

Pressure heads

90
Q

Total Dynamic head of a pump is what?

A

The discharge pressure minus the suction pressure

91
Q

What is the hydraulic power of a pump equal to?

A

Volumetric flow rate times total dynamic head

92
Q

NPHSA is the difference between what?

A

The suction head and the vapor pressure head

93
Q

NPHSR is provide by what?

A

The manufacturer

94
Q

NPHSR has to be smaller than what?

A

NPHSA

95
Q

Two equal pumps in a series have what?

A

Double the head

96
Q

Two equal pumps in parallel have a smaller head than what?

A

One pump

97
Q

If NPHSA is zero what can happen?

A

The pump can cavitation

98
Q

What is the function of check valves?

A

To prevent the reversal of flow

99
Q

Gate valves are not usually used for what?

A

Control

100
Q

Control valves have what kind of pressure drops?

A

Large

101
Q

Closing a control valve increases what?

A

The pressure drop of the system

102
Q

What kind of inherent flow characteristics do we want?

A

Linear

103
Q

What type of valve has inherently linear flow characteristics?

A

Globe

104
Q

Why do we want linear flow characteristics?

A

PID controllers need linear

105
Q

What kind of valve is linear when installed?

A

Equal percentage

Process Design and Safety (6 decks)

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