1
Q
What pipe sizes standards give
A
Nominal Pipe Size
NOT ACTUAL SIZES
2
Q
The ____ the pipe the higher the schedule
A
Thicker
3
Q
The thicker the pipe the ____ the schedule
A
higher
4
Q
What different thicknesses of pipe are called
A
Schedule
5
Q
Schedule number equation
A
Sch = 1000 P/S
P = service pressure
S = allowable stress at these conditions
6
Q
Volume Flow Rate (Q)
A
Area * velocity
Q = Qv
7
Q
Volume Flow Rate (For a circular pipe) (Q)
A
Q = (pi * D^2/4) V
8
Q
Darcy - Weisbach Equation
A
hL = f * L/D * ρv^2/2
hL = pressure of fluid
f = friction factor
L= Pipe Length
D= pipe diameter
V= fluid velocity
9
Q
Darcy - Weisbach Equation (expressed as pressure)
A
ΔP = f * L/D * v^2/2g
hL = pressure of fluid
f = friction factor
L= Pipe Length
D= pipe diameter
V= fluid velocity
10
Q
Pressure exerted by a fluid at equilibrium due to the force of gravity. It increases with depth in a fluid, as the weight of the fluid above exerts additional pressure
A
Hydrostatic pressure
11
Q
Hydrostatic pressure equation
A
P = ρgh
12
Q
Moody friction factor equation
A
Moody friction factor = 4 * Fanning Friction Factor
13
Q
In the ____ region, pipe roughness has no effect on friction factor
A
Laminar
14
Q
In the laminar region, pipe roughness has ________ on friction factor
A
No effect
15
Q
Friction factor (2000<Re) equation
A
f = 64/Re
16
Q
Relative roughness equation
A
absolute roughness/diameter
17
Q
Reynolds Number Equation
A
Re = ρvD/μ
18
Q
The rate at which material is delivered by the pump
A
Flow
19
Q
The pressure provided by the pump for that flow as measured in terms of height
A
Head
20
Q
Point of highest efficiency of the pump
A
Best Efficiency Point
21
Q
K factor in Darcy Equation
A
hL = K v^2/2g
22
Q
known as resistance coefficient or velocity head loss in the Darcy Equation
A
K factor
23
Q
Length of a straight pipe that would produce the SAME pressure drop as a particular pipefitting or valve
A
Equivalent length
24
Q
Inlet vs outlet pump pressure equation
A
P2-P1 = ρgh - ρg(z2-z1) -1/2*ρ(v^2 - v^2)
v2-v1
25
________ velocity leads to lower head/pressure drop
Higher
26
Lower
Higher velocity leads to ________ head/pressure drop
27
The impeller is subject to ________ which get greater the further away the operating point is from the Best Efficiency Point
axial and radial forces
28
The impeller is subject to axial and radial forces which get____ the further away the operating point is from the Best Efficiency Point
greater
29
The impeller is subject to axial and radial forces which get greater the ________ the operating point is from the Best Efficiency Point
Further away
30
The lowest flow that the pump can operature without being damaged and/or overheating
Minimum flow
31
Minimum point of the head, maximum flow of the pump - beyond this the pump cannot operate
The Run-Out Point
32
End of curve conditions
- NPSHr (cavitation risk) increases
- Drive system may become overloaded because of increased power consumption
## Footnote
AVOID OPERATING AT RHS OF PUMP CURVE
33
The ________ the diameter of impeller, the greater the pressure and flow rate capabilities
Bigger
34
The bigger the diameter of impeller, the ____ the pressure and flow rate capabilities
greater
35
Power transferred to liquid equation
Power transferred to liquid = Q * H * ρ * g
## Footnote
Q = volumetric flow
H = head
ρ = density
g = gravitational acceleration
36
If liquid pressure in a centrifugal pump is ____ its vapour pressure bubbles form
below
37
If liquid pressure in a centrifugal pump is below its vapour pressure ____ form
bubbles
38
What bubbles in a centrifugal pump lead to
1. Noise
2. Loss of capacity
3. Damage
39
Pressure required to boil a liquid at a given temperature
Vapour pressure
40
Crucial process that ensures the pump is filled with fluid before it starts operating
Priming
41
Minimum net pressure required at the pump inlet nozzle to prevent the pump cavitating
Net Positive Suction Head Required
## Footnote
NPSHr
42
Absolute pressure at the pump inlet
Net Positive Suction Head Available
## Footnote
NPSHa
43
NPSHa must be ____ than NPSHr to avoid cavitation
greater
44
Occurs when the pressure at the pump inlet is below the vapour pressure of the liquid
Cavitation
45
____ pump speed increases flowrate and head
Higher
46
Higher pump speed ____ flowrate and head
Increases
47
Give the power required to operate the pump within a certain flowrate range
Power curves
48
The NPSHr required ____ as flow increases
increases
49
The NPSHr required increases as flow _____
increases
50
Pipes & fittings the liquid is pumped through
System
51
Total vertical distance the pump raises water
Static head
52
Ability of a pump to adjust its head output based on the flowrate and pressure requirements of a system
Variable head
53
What the plot of the system curve is
H vs Q
54
What H means on the system curve
Total frictional and static pressure loss requirement in pipe and fittings
55
Distance between y intercept of system curve and the bottom of the graph
static head
56
Increase in H from static head on system curve
variable head
57
Static head is zero.
Variable head increases with flowrate.
Due entirely to frictional losses
No height change between reservoirs
58
Mostly static lift.
Little friction loss
First reservoir is below second
59
Negative static lift
First reservoir is above second
60
Pressure required by pump equation
ΔP = (Pd + Hd)-(Po-Ho)+(Discharge pipework ΔP) + (Inlet Pipework ΔP)
61
For the pump to not cavitate
NPSHa > NPSHr
62
Can be used to change the system curve
Control valve
63
Minimum net pressure required at the pump inlet nozzle to prevent the pump cavitating
NPSHr
| Units: Absolute meters of fluid
64
NPSHa equation
NPSHa = (Po+Ho) - (Suction Pipework ΔP) - (Vapour pressure of fluid at operating temperature)
| Only considers inlet side
65
NPSHr ____ with flow, so you need to calculate at the maxi,u, flow that you are designing for
Increases
66
Frictional losses ____ with pipe diameter decrease
Increase
67
At a fixed impeller speed, volumetric flow is proportional to...
Impeller diameter
## Footnote
(Q1/Q2) = (D1/D2)
68
At a fixed impeller diameter, volumetric flow is proportional to...
Impeller speed
## Footnote
(Q1/Q2) = (N1/N2)
69
At a fixed impeller speed, pressure is proportional to...
Impeller diameter^2
## Footnote
(H1/H2) = (D1/D2)^2
70
At a fixed impeller diameter, power is proportional to...
Impeller speed^3
## Footnote
(P1/P2) = (N1/N2)^3
71
At a fixed impeller diameter, pressure is proportional to...
Impeller speed^2
## Footnote
(H1/H2) = (N1/N2)^2
72
At a fixed impeller speed, power is proportional to...
Impeller diameter^3
## Footnote
(P1/P2) = (D1/D2)^3
73
Pump affinity laws
Flowrate
Q1/Q2 = N1/N2
## Footnote
N is impellor speed
74
Pump affinity laws
Head/pressure
H1/H2 = (N1/N2)
## Footnote
N is impellor speed
75
Cause the system curve to intersect higher up pump flow curve
Throttled systems
76
The speed of an electric motor depends on
Frequency of electrical supply
77
How to control flowrate & pressure
1. Manipulate the pump
2. Manipulate the system ( pipes and fittingd are fixed but control valves have variable pressure drop)
78
Speed of motor equation
Electrical supply frequency/number of pairs of pole in motor
79
Modify the frequency of electricity supply to the pump motor
Variable Frequency Drives (VFDs)
80
Can operate anywhere under the curve
Variable speed pump
81
Can operate ONLY on the curve
Fixed speed pump
82
Change in flow varies in proportion to
speed
83
Change in head varies in proportion to
speed^2
84
Change in power varies in proportion to
speed^3
85
Equation for scaling pumps up/down (flowrate)
Q1/Q2 = (N1/N2)(D1/D2)
86
Equation for scaling pumps up/down (Head/pressure)
H1/H2 = (N1/N2)^2(D1/D2)^2
87
Equation for scaling pumps up/down (power)
P1/P2 = (N1/N2)^3(D1/D2)^3
88
Multiple pumps in series...
Increase in pressure but not flow
89
Multiple pumps in parallel...
Increase in flow but not pressure
90
Pressure drop through a valve
Flow coefficient Cv
91
Flow coefficient Cv equation
Cv = 1.16Q √(SG/ΔP)
92
Closing this in the pump discharge line increases frictoinal pressure drop and reduces flow
Throttling valve
93
Increases pump power required and wastes energy.
Not used in suction lines as NPSHa is reduced as it is likely to damage the pump
Throttling
94
Used to relieve flowrate/pressure output from a pump
Flow restriction orifice
95
Orifice plate flowrate change equation
Q=CdAo √(2ΔP)/(ρ(1-β^4))
96
Three types of control valve plug/seat arrangement
- Quick opening
- Linear
- Equal percentage
97
Large change in flowrate for a small valve lift (% travel) from the closed position
Fast opening
98
Valve plug is shaped so that the flowrate is directly proportional to the valve lift (% travel)
Linear
99
- Valves have a plug shape so that each increment in valve lift (%) increases the flowrate by a certain % if previous flow
- The relationship between valve lift & orifice size is not linear but logarithmic
- Change in flowrate increases with valve opening
Equal percentage
EG-332 Process Equipment Selection & Control
flashcards
Decks in class (2)
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