Pumps and Valves Flashcards
1
Q
What are the most common types of valves?
A
Control
Pressure Relief
On-off
Check
2
Q
On-off valves are used for stopping the _____.
A
Flow
3
Q
On-off valves provide _____ _____ when being closed.
A
tight shutoff
4
Q
On-off valves provide _____ _____ _____ when fully opened
A
low pressure drops
5
Q
Most control valves can be used for on-off duty, especially ____ valves
A
ball
6
Q
_____ valves are often used in of-off service
A
gate
7
Q
Check valves prevent the _____ of flow
A
reversal
8
Q
Check valves ____ with forward flow and _____ against reverse flow
A
open;close
9
Q
What are three types of check valves?
A
lift check
swing check
tilting-disk check
10
Q
Lift check valves depend on _____ for operation
A
gravity
11
Q
Lift check work with ______ pressure services
A
high
12
Q
Swing check valves have a closure member that swings about a _______
A
hinge
13
Q
Swing check valves are employed along with ____ valves
A
gate
14
Q
Swing check valves work with ____ fluid velocities
A
low
15
Q
With Swing Check valves flow reversal is _________
A
infrequent
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
17
Q
Tilting-disk check valves are _______ loaded
A
spring
18
Q
Tilting-disk check valves are more _________
A
expensive
19
Q
Tilting-disk check valves are more difficult to _____.
A
repair
20
Q
control valves are used to ______ the flow automatically to any desired amount
A
regulate
21
Q
control valves help with ____ pressure drops
A
high
22
Q
Name four different control valves.
A
globe
ball
butterfly
plug
23
Q
Globe valves have a _____ stem motion
A
linear
24
Q
Globe valves have significant pressure ____
A
drops
25
globe valves _____ the flow
control
26
globe valves are good at servicing fluids containing no ____
solids
27
ball valves have ______ stem motion
rotary
28
ball valves have _____ friction
small
29
ball valves have a ____ pressure drop
small
30
ball valves have ____ flow capacity
high
31
ball valves provide a ______ shutoff
tight
32
ball valves are well suited for _____ ____ service
on-off
33
ball valves are not good for _______ services
throttling
34
butterfly valves have _____ stem motion
rotary
35
butterfly valves have ____ pressure drop
small
36
butterfly valves can handle ______ flow capacity
large
37
butterfly valves provide good service with fluids with or without ______.
solids
38
Butterfly valves can or cannot handle on-off duty?
can
39
butterfly valves can or cannot handle throttling duty?
can
40
Plug Valves have _____ stem motion
rotary
41
plug valves provide a _____ shutoff
tight
42
______ plug valves can be used to simplify the piping system
multiport
43
Plug valves are well suited for ____ ____ service
on-off
44
What happens to temperature when mu jt is postitive
decreases
45
what happens to temperature when mu jt is negative
increases
46
pressure relief valves operate at pressures below _____
10,000 psia
47
Pressure relief valves operate at temperatures below ____
1,000 F
48
What are two types of pressure relief valves
direct-loaded
| pilot operated
49
A positive displacement pump can be what kind?
rotary
reciprocating (pistons)
miscellaneous (peristaltic)
50
What are the advantages of a positive displacement pump?
self-priming
can work in two directions
can pump liquids with gases for a small amount of time
51
What are the disadvantages of positive displacement pumps?
most of them cannot operate with closed discharge
| might produce oscillations in discharge
52
Peristaltic Pump is used to move tank to _____
tank
53
Peristaltic pumps are used in what industries?
food, batch, paper
54
What are some types of centrifugal pumps?
volute (shell and simple impeller)
diffuser (diffuser vanes around the impeller)
turbine pump
propeller pump
55
what are some advantages of centrifugal pumps?
```
low cost - easy maintenance
do not produce a lot of noise
uniform discharge (no oscillations)
```
56
What are some disadvantages of centrifugal pumps?
do not produce large heads (cannot increase pressure a lot)
| do not work well with high viscosity fluids
57
You can change the _____ size to modify centrifugal pumps
impeller
58
If Hs = Hp, pick the Hs curve close to ______ open, at maximum flow
80%
59
Where the Pump Curve and System Curve intersect there is _____ pressure drop and the valve cannot control flow
0
60
The head Hs goes up as you _____ the valve
close
61
Hs =
-[(P4-P3)+(P2-P1)]
62
As the Reynold's number increases, the _____ losses decrease
friction
63
To increase the pressure head, you can ____ the level of the fluid
raise
64
efficiencies are ______ of the impeller
independent
65
You can select the ______ _____ when selecting a pump.
Impeller diameter
66
When selecting a pump you should look at maximum efficiency and that NPSHA ______NPSHR
>
67
A large impeller size ______ the pressure drop
increases
68
Centrifugal pumps are chose because they can operate in a wider range of what?
flowrates
69
Using a positive displacement pump uses more _____ and ______ the fluid.
energy; heats
70
What kind of pump give an approximate constant flow?
positive displacement
71
Ps is usually what? Suction pressure
constant
72
You can increase the discharge pressure by ______ the vertical distance
increasing
73
Why do the pump curves decrease?
Friction takes over as flow rate increases.
74
You can calculate the suction pressure using what?
An energy balance
75
The available net positive suction head must be ______ than the required net positive suction head
greater
76
NPSHR is a required value suggested by whom?
the manufacturer
77
Pumps will not cavitate if what is positive?
NPSHA
78
What is it called when pressure increases inside the pump causing bubbles to collapse?
cavitation
79
Cavitation reduces _____ and _____ the pump
capacity; damages
80
NPSHA =
(Ps/rho gravity) - (Pv/ rho gravity)
81
We want Ps to be _____ than Pv
greater
82
If NPSHA is negative the fluid enters the pumps with what?
bubbles
83
Total dynamic Head =
Pd-Ps
84
Hydraulic horsepower W =
(Q*TDH (psi))/(rho gravity)
85
shaft efficiency, aeta =
Wh/Wb
86
saft efficiency is always less than 1 because of what?
friction losses that transform irreversibly to heat
87
Mechanical Energy Balance is defined as what?
Static pressure plus pressure change plus acceleration is equal to the change of work done - friction losses
88
What has rotating gears, lobes, or screws?
Rotary pumps
89
Centrifugal pumps do not have large what?
Pressure heads
90
Total Dynamic head of a pump is what?
The discharge pressure minus the suction pressure
91
What is the hydraulic power of a pump equal to?
Volumetric flow rate times total dynamic head
92
NPHSA is the difference between what?
The suction head and the vapor pressure head
93
NPHSR is provide by what?
The manufacturer
94
NPHSR has to be smaller than what?
NPHSA
95
Two equal pumps in a series have what?
Double the head
96
Two equal pumps in parallel have a smaller head than what?
One pump
97
If NPHSA is zero what can happen?
The pump can cavitation
98
What is the function of check valves?
To prevent the reversal of flow
99
Gate valves are not usually used for what?
Control
100
Control valves have what kind of pressure drops?
Large
101
Closing a control valve increases what?
The pressure drop of the system
102
What kind of inherent flow characteristics do we want?
Linear
103
What type of valve has inherently linear flow characteristics?
Globe
104
Why do we want linear flow characteristics?
PID controllers need linear
105
What kind of valve is linear when installed?
Equal percentage
