Pumps v2 Flashcards
(152 cards)
1
Q
The discharge valve for a radial-flow centrifugal cooling water pump is closed in preparation for
starting the pump.
After the pump is started, the following stable pump pressures are observed:
Pump discharge pressure = 30 psig
Pump suction pressure = 10 psig
With the discharge valve still closed, if the pump speed is doubled, what will be the new pump
discharge pressure?
A
90 psig
2
Q
The discharge valve for a radial-flow centrifugal cooling water pump is closed in preparation for
starting the pump.
After the pump is started, the pump suction and discharge pressures stabilize as follows:
Pump suction pressure = 5 psig
Pump discharge pressure = 35 psig
With the discharge valve still closed, if the pump speed is doubled, what will be the new stable pump
discharge pressure?
A
125 psig
3
Q
The available net positive suction head for a pump may be expressed as…
A
suction pressure minus saturation pressure of the fluid being pumped.
4
Q
Which one of the following operations in a closed system will cause a decrease in available net
positive suction head for a centrifugal pump?
A
Throttling open the pump discharge valve.
5
Q
Refer to the drawing of a cooling water system (see figure below).
The available net positive suction head for the centrifugal pump will be increased by…
A
opening surge tank makeup valve A to raise tank level.
6
Q
Refer to the drawing of a cooling water system (see figure below).
The available net positive suction head for the centrifugal pump will be decreased by…
A
throttling pump discharge valve C more open
7
Q
Refer to the drawing of an operating cooling water system (see figure below).
Which one of the following will increase available net positive suction head for the centrifugal pump?
A
Positioning pump discharge valve C more closed.
8
Q
Refer to the drawing of a cooling water system (see figure below).
The available net positive suction head for the centrifugal pump will be decreased by…
A
increasing the heat loads on the cooling water system.
9
Q
Refer to the drawing of an operating cooling water system (see figure below).
Which one of the following will decrease available net positive suction head for the centrifugal pump?
A
Positioning pump discharge valve C more open.
10
Q
A cooling water pump is operating with pump suction parameters as follows:
Suction Temperature = 124°F
Suction Pressure = 11.7 psia
What is the approximate available net positive suction head (NPSH) for the pump? (Neglect the
contribution of the suction fluid velocity to NPSH.)
A
23 feet
11
Q
A centrifugal pump is operating at maximum design flow rate, taking suction on a vented water
storage tank and discharging through two parallel valves. Valve A is fully open and valve B is half
open.
Which one of the following will occur if valve B is fully closed?
A
The pump available net positive suction head will increase.
12
Q
Refer to the drawing of an operating cooling water system (see figure below).
Which one of the following will increase the available net positive suction head for the centrifugal
pump?
A
Reducing the heat loads on the cooling water system.
13
Q
A centrifugal pump is needed to take suction on a water storage tank and deliver high pressure water to
a water spray system. To minimize axial thrust on the pump shaft, the pump should have
__________ stage(s); and to maximize the available NPSH at the impeller inlet, the pump should have
a __________ suction impeller.
A
multiple opposed; double
14
Q
A centrifugal pump is taking suction on an open storage tank that has been filled to a level of 40 feet
with 10,000 gallons of 60°F water. The pump is located at the base of the tank, takes a suction from
the bottom of the tank, and discharges to a lake.
Given:
$ The pump is currently operating at its design flow rate of 200 gpm and a total developed head of
150 feet.
$ The pump requires 4 feet of net positive suction head.
How will the centrifugal pump flow rate be affected as the water storage tank level decreases?
A
Flow rate will gradually decrease until the pump becomes air bound when the tank empties.
15
Q
Refer to the drawing below of a centrifugal pump taking suction from the bottom of an open storage
tank containing water at 66°F. Pump and water level elevations are indicated in the figure. Assume
standard atmospheric pressure.
Assuming that pump suction head loss is negligible, what is the approximate value of net positive
suction head available to the pump?
A
20 feet
16
Q
Refer to the drawing of an elevated centrifugal pump taking suction from the bottom of an open
storage tank containing water at 66°F (see figure below). Assume standard atmospheric pressure.
The pump requires 4.0 feet of net positive suction head (NPSH). Assume that pump suction head loss
is negligible.
If tank water level is allowed to decrease continuously, at what approximate water level will the pump
begin to cavitate?
A
21 feet
17
Q
Refer to the drawing of a centrifugal pump taking suction from the bottom of an open storage tank
containing water at 66°F (see figure below). Pump and water level elevations are indicated in the
figure. Assume standard atmospheric pressure.
Assuming that pump suction head loss is negligible, what is the approximate value of net positive
suction head available to the pump?
A
45 feet
18
Q
Refer to the drawing of a centrifugal pump taking suction from the bottom of an open water storage
tank (see figure below).
Given:
$ The tank contains 60°F water.
$ The eye of the pump impeller is located 50 feet above the bottom of the tank.
$ The pump requires a minimum net positive suction head of 4 feet.
Which one of the following describes the effect on pump operation if tank water level is allowed to
continuously decrease?
A
The pump will operate normally until tank water level decreases below approximately 20 feet, at
which time the pump will cavitate.
19
Q
Refer to the drawing of a steam condenser, hotwell, and condensate pump (see figure below).
Given the following:
$ The eye of the pump impeller is located 6.0 feet below the bottom of the hotwell.
$ The pump requires 10.0 feet of net positive suction head (NPSH).
$ Condenser pressure is 1.2 psia.
$ Hotwell water temperature is 90°F.
$ Pump suction head losses are zero.
What is the minimum hotwell water level necessary to provide the required NPSH?
A
2.8 feet
20
Q
A centrifugal pump is taking suction on a water storage tank and delivering the makeup water to a
cooling water system. The pump will have the lowest net positive suction head requirement if the
pump is operated at a relatively __________ speed with a __________ discharge flow control valve.
A
low; throttled
21
Q
Refer to the drawing below of a centrifugal pump taking suction from the bottom of an open storage
tank containing water at 75°F. Pump and water level elevations are indicated in the figure. Assume
standard atmospheric pressure.
Assuming that pump suction head loss is negligible, what is the approximate value of net positive
suction head available to the pump?
A
23 feet
22
Q
Refer to the drawing of a steam condenser, hotwell, and condensate pump (see figure below).
Given the following initial conditions:
$ Condenser pressure is 1.2 psia.
$ Condensate temperature is 96°F.
$ Hotwell level is 10 feet above the condensate pump suction.
Which one of the following will provide the greatest increase in NPSH available to the condensate
pump? (Assume that condenser pressure does not change.)
A
Hotwell level increases by 6 inches.
23
Q
A centrifugal pump is taking suction on a water storage tank and discharging through a flow control
valve. The pump will have the highest net positive suction head requirement if the pump is operated
at a __________ speed with a __________ discharge flow control valve.
A
high; fully open
24
Q
An operating centrifugal pump has a net positive suction head (NPSH) requirement of 150 feet.
Water at 300°F is entering the pump. Which one of the following is the lowest listed pump inlet
pressure that will provide adequate NPSH for the pump?
A
127 psia
25
Refer to the drawing of a steam condenser, hotwell, and condensate pump (see figure below).
Given the following:
$ The eye of the pump impeller is located 6.0 feet below the bottom of the hotwell.
$ Hotwell water level is 6.0 feet.
$ Hotwell water temperature is 90°F.
$ Condenser pressure is 1.3 psia.
$ Fluid velocity and friction head losses are zero.
What is the net positive suction head available to the condensate pump?
13.4 feet
26
The current conditions for a centrifugal water pump are as follows:
Pump suction pressure = 140 psia
Pump suction temperature = 300°F
The pump requires a net positive suction head (NPSH) of 150 feet for pumping water at 300°F.
Which one of the following is the lowest listed pump suction pressure that will provide the required
NPSH for the current pump suction temperature?
128 psia
27
A centrifugal pump is taking suction from an open water storage tank. The pump is located at the base
of the tank, takes a suction from the bottom of the tank, and discharges to a pressurized system.
Given:
$ The tank is filled to a level of 26 feet with 60°F water.
$ The pump is currently operating at 50 gpm.
$ The pump requires 30 feet of net positive suction head.
Which one of the following describes the current pump status, and how the pump flow rate will be
affected as the level in the storage tank decreases?
The pump is currently not cavitating; pump flow rate will gradually decrease with tank level and
then rapidly decrease as the pump becomes air bound when the tank empties.
28
Refer to the drawing of a centrifugal pump taking suction from a reservoir.
The pump is located on shore, with the eye of the pump 4 feet higher than the reservoir water level.
The pump=s suction line extends 4 feet below the surface of the reservoir. Which one of the following
modifications would increase the pump=s available net positive suction head? (Assume the reservoir
is at a uniform temperature and ignore any changes in suction line head loss due to friction.)
Lower the pump and suction line by 2 feet.
29
Refer to the drawing of a centrifugal pump taking suction from a reservoir (see figure below).
The pump is located on shore, with the eye of the pump 4 feet higher than the reservoir water level.
The pump=s suction line extends 4 feet below the surface of the reservoir. Which one of the following
modifications would decrease the pump=s available net positive suction head? (Assume the reservoir
is at a uniform temperature and ignore any changes in suction line head loss due to friction.)
Raise the pump and suction line by 2 feet.
30
Refer to the drawing of a centrifugal pump with a water storage tank for its suction source. The
storage tank is open to the atmosphere and contains 20 feet of water at 60°F. The pump is currently
stopped.
If the temperature of the water in the storage tank and pump suction piping increases to 80°F, with the
accompanying water expansion, the suction head for the pump will __________; and the available net
positive suction head for the pump will __________.
increase; decrease
31
A centrifugal pump is taking suction from an open water storage tank. The pump is located at the base
of the tank, takes a suction from the bottom of the tank, and discharges to a pressurized system.
Given:
$ The storage tank is filled to a level of 26 feet with 60°F water.
$ The pump requires 45 feet of net positive suction head.
$ The pump is currently operating at 50 gpm.
Which one of the following describes the current pump status, and how the pump flow rate will be
affected as the level in the storage tank decreases?
The pump is currently not cavitating; pump flow rate will gradually decrease with tank level, and
then rapidly decrease when cavitation begins before the tank empties.
32
A centrifugal pump is operating normally in a closed cooling water system. If system pressure is
increased by 10 psi, the available net positive suction head (NPSH) for the pump will __________;
and the pump mass flow rate will __________. (Assume the water density does not change and the
minimum required NPSH for the pump is maintained.)
increase; remain the same
33
```
A centrifugal water pump is operating normally with the following parameters:
Inlet water pressure = 15 psia
Water temperature = 100°F
Pump head added = 100 feet
What is the pump discharge pressure?
```
58 psia
34
Refer to the drawing of a centrifugal pump with a water storage tank for its suction source. The
storage tank is open to the atmosphere and contains 20 feet of water at 90°F. The pump is currently
stopped.
If the temperature of the water in the storage tank and pump suction piping decreases to 70°F, with the
accompanying water contraction, the suction head for the pump will __________; and the available
net positive suction head for the pump will __________.
decrease; increase
35
In response to a loss of coolant accident, an emergency core cooling pump is taking suction from the
bottom of a vented water storage tank and discharging to the downcomer region of a reactor vessel.
Which one of the following will cause the pump to operate closer to cavitation?
The temperature of the water in the water storage tank increases.
36
Shutting the discharge valve on an operating motor-driven radial-flow centrifugal pump in a water
system will cause the motor amps to __________ and the pump discharge pressure to __________
decrease, increase
37
When starting an AC motor-driven centrifugal pump, the response of motor current will be...
high starting amps, decreasing to a lower equilibrium value of running amps.
38
A constant-speed radial-flow centrifugal pump motor draws the least current when the pump is...
at shutoff head.
39
A centrifugal pump was initially circulating water at 100°F in a cooling water system. Over several
hours, the water temperature increased to 150°F. Assuming system flow rate (gpm) was constant,
pump motor amps __________ during the heatup because __________.
decreased; the water density decreased
40
An AC motor-driven centrifugal pump was initially circulating water at 200°F in a cooling water
system. Over several hours, the circulating water temperature decreased to 120°F while system flow
rate (gpm) remained constant.
During the system cooldown, pump motor current __________ because __________
increased; the water density increased
41
A centrifugal pump is operating in a closed system with all valves fully open. If the pump discharge
valve is throttled 75 percent closed, pump motor current will...
decrease and stabilize at a lower value.
42
Which one of the following operating conditions for a motor-driven radial-flow centrifugal pump will
result in the most current being drawn by the pump motor?
The pump is operating at runout.
43
Initially, an AC motor-driven centrifugal pump was operating in a cooling water system with cooling
water temperature at 150°F. Over several hours, the cooling water temperature decreased and is
currently 100°F. Assuming pump flow rate (gpm) remained constant, the pump motor is drawing
__________ current because __________ is greater.
more; cooling water density
44
An AC motor-driven centrifugal pump is circulating water at 180°F with a motor current of 100 amps.
After several hours, system temperature has changed such that the water density has increased by 4
percent.
Assuming pump head and volumetric flow rate do not change, which one of the following is the new
pump motor current?
104 amps
45
Refer to the drawing of an operating cooling water system (see figure below).
Initially, centrifugal pump A is circulating water at 100°F. If the temperature of the cooling water
entering pump A increases to 200°F, the pump’s motor current will... (Assume the pump’s
volumetric flow rate is constant.)
decrease, because the density of the cooling water will decrease
46
A constant-speed radial-flow centrifugal pump motor draws the least current when the pump is...
at shutoff head with no recirculation flow.
47
A reactor coolant pump (RCP) was initially circulating reactor coolant at 100°F. Over several hours,
the reactor coolant temperature increased to 150°F.
Assuming coolant flow rate (gpm) was constant, RCP motor amps __________ during the heatup
because __________.
decreased; coolant density has decreased
48
A typical radial-flow centrifugal pump is operating at rated conditions in an open system with all
valves fully open. If the pump discharge valve is throttled to 50 percent closed, pump discharge
pressure will __________; and pump motor current will __________.
increase; decrease
49
A centrifugal pump in a cooling water system is operating with a motor current of 200 amps. After
several hours, the system water density has increased by 3 percent, while the pump head and
volumetric flow rate have remained the same.
Which one of the following is the new pump motor current?
206 amps
50
A constant-speed centrifugal pump motor draws the most current when the pump is...
accelerating to normal speed during start.
51
An AC motor-driven centrifugal pump was just started. During the start, motor current remained
peaked for 6 seconds before decreasing to standard running current. Normally, the starting current
peak lasts about 4 seconds.
Which one of the following could have caused the extended starting current peak?
The pump was initially rotating slowly in the reverse direction.
52
A cooling water pump is being driven by an AC induction motor. Which one of the following
describes how and why pump motor current will change if the pump shaft shears?
Decreases due to decreased pump work.
53
A centrifugal pump is circulating water at 180°F with a pump motor current of 200 amps. After
several hours, system temperature has changed such that the water density has increased by 6 percent.
Assuming pump head and volumetric flow rate do not change, which one of the following is the new
pump motor current?
212 amps
54
An AC motor-driven centrifugal water pump was just started. During the start, motor current
remained peaked for 2 seconds, and then decreased and stabilized at about one-fifth the standard
running current. Normally, the starting current peak lasts about 4 seconds.
Which one of the following could have caused the abnormal start indications above?
The coupling between the motor and pump shafts was left disconnected after maintenance
55
A radial-flow centrifugal cooling water pump is driven by an AC induction motor. The pump can
supply cooling water to several heat loads, all of which are in parallel alignment. The following
pump conditions initially exist:
Pump motor current = 100 amps
Pump flow rate = 400 gpm
Pump suction temperature = 70°F
Four hours later, the motor is drawing 95 amps. Which one of the following could be responsible for
the observed decrease in motor amps?
Cooling water flow was isolated from an out-of-service heat load with no change in the
temperature of the cooling water being pumped.
56
A radial-flow centrifugal cooling water pump is driven by an AC induction motor. The pump can
supply cooling water to several heat loads, all of which are in parallel alignment. Initially, the
following pump conditions exist:
Pump motor current = 100 amps
Pump flow rate = 400 gpm
Pump suction temperature = 70°F
Four hours later, the pump motor is drawing 105 amps. Which one of the following could be
responsible for the observed increase in motor current?
Cooling water flow was established to an additional heat load with no change in the temperature of
the cooling water being pumped.
57
A motor-driven centrifugal pump exhibited indications of pump failure while being started. Which
one of the following pairs of observations indicate that the pump failure is a sheared impeller shaft?
Lower than normal running current and no change in system flow rate.
58
Some large centrifugal pumps are started with their discharge valves closed to prevent...
excessive current in the pump motor.
59
Some large centrifugal pumps are interlocked so that the pump will not start unless its discharge valve
is at least 90 percent closed. This interlock is provided to minimize...
the duration of the pump motor starting current.
60
Which one of the following contains two reasons for starting a typical radial-flow centrifugal pump
with the discharge piping full of water and the discharge valve closed?
Prevent water hammer and prevent excessive duration of starting current.
61
Refer to the drawing of a cooling water system and the associated pump/system operating curves (see
figure below) in which pumps A and B are identical single-speed centrifugal pumps and only pump A
is operating.
If pump B is started, system flow rate will be __________ and common pump discharge pressure will
be __________.
higher; higher
62
Refer to the drawing of a cooling water system and the associated pump/system operating curves (see
figure below).
Pumps A and B are identical single-speed centrifugal pumps, and only pump A is operating. If pump
B is started, after the system stabilizes system flow rate will be...
less than twice the original flow.
63
A centrifugal pump is operating in parallel with a positive displacement pump in an open water
system. Each pump has the same maximum design pressure.
If pump discharge pressure increases to the maximum design pressure of each pump, the centrifugal
pump will be operating near __________ flow rate and the positive displacement pump will be
operating near __________ flow rate.
minimum; maximum rated
64
Refer to the drawing of a cooling water system (see figure below).
Pumps A and B are identical single-speed centrifugal pumps and both pumps are initially operating
when pump B trips. After the system stabilizes, system flow rate will be...
more than one-half the original flow.
65
Which one of the following is an indication of pump runout?
High pump vibration
66
Which one of the following is an indication of pump runout?
High pump flow rate
67
Which one of the following describes typical radial-flow centrifugal pump runout conditions?
Low discharge pressure, high flow, high power demand
68
A centrifugal pump is operating at its maximum design flow rate, delivering water through two
parallel valves. Valve A is half open, and valve B is one quarter open.
Which one of the following will occur if both valves are fully opened?
The pump will operate at runout conditions.
69
Refer to the drawing of centrifugal pump and system operating curves (see figure below).
Which point represents pump operation at runout conditions?
point C
70
Refer to the drawing of a cooling water system in which only centrifugal pump A is operating and the
common pump discharge valve is currently 90 percent open (see figure below).
An abnormal total heat load on the cooling water system is causing pump A to approach operation at
runout conditions. Which one of the following will cause pump A to operate further away from
runout conditions? (Assume that satisfactory available net positive suction head is maintained at all
times.)
Starting pump B.
71
A flow-limiting venturi in the discharge piping of a centrifugal pump decreases the potential for the
pump to experience...
runout
72
Refer to the drawing of a radial-flow centrifugal pump with a recirculation line in an open system (see
figure below). The recirculation line throttle valve is currently 50 percent open. The pump is
currently operating very close to runout.
To move pump operation farther away from runout, without reducing the pump’s available net
positive suction head, an orifice can be installed at point _____; or the pump’s recirculation line
throttle valve can be positioned more __________.
Y; closed
73
```
Refer to the drawing of a lube oil temperature control system and the associated pump/system
operating curves (see figure below).
The pump is initially operating at point B. If the temperature control valve modulates further open,
operating point B will be located on curve __________ closer to point __________.
```
1; D
74
```
Refer to the drawing of a lube oil temperature control system and the associated pump/system
operating curves (see figure below).
The pump is operating at point B on the operating curve. If the temperature control valve modulates
further closed, operating point B will be located on curve __________ closer to point __________.
```
2; A
75
Refer to the drawing of four sets of centrifugal pump and system operating curves (see figure below).
Each set of curves shows a combination of two pump/system operating conditions.
Initially, a centrifugal pump is operating with a partially open discharge valve in a closed system.
The discharge valve is then opened fully.
Which set of operating curves depicts the "before" and "after" conditions described above?
4
76
Refer to the drawing of four sets of centrifugal pump and system operating curves (see figure below).
Each set of curves shows the results of a change in pump and/or system operating conditions.
Two identical constant-speed centrifugal pumps are operating in series in an open system when one
pump trips.
Which set of operating curves depicts the "before" and "after" conditions described above?
3
77
Refer to the drawing of four sets of centrifugal pump and system operating curves (see figure below).
Each set of curves shows the steady-state "before and after" conditions for a change in pump and/or
system operating conditions.
Initially, one centrifugal pump was operating in a cooling water system. Then, a second identical
centrifugal pump was started in series with the first.
Which set of operating curves shown below depicts the steady-state “before and after” conditions
described above?
3
78
Initially, two identical centrifugal pumps were operating in parallel in a closed system when one pump
tripped.
Which set of operating curves shown below depicts the steady-state “before and after” conditions
described above?
1
79
Refer to the drawing of four sets of centrifugal pump and system operating curves (see figure below).
Each set of curves shows a combination of two pump/system operating conditions.
Initially, a constant-speed centrifugal pump was operating in an closed system. Another identical
centrifugal pump was then started in parallel with the first.
Which set of operating curves depicts the "before" and "after" conditions described above?
1
80
Refer to the drawing of four sets of centrifugal pump and system operating curves (see figure below).
Each set of curves shows the results of a change in pump and/or system operating conditions.
Initially, a centrifugal pump is operating in a closed water system and discharging through a single
heat exchanger. A second heat exchanger is then placed in service in parallel with the first.
Which set of operating curves depicts the "before" and "after" conditions described above?
4
81
Refer to the drawing of centrifugal pump and system operating curves (see figure below).
Which one of the following determines the general shape of the curve from point C to point D?
The frictional and throttling losses in the piping system as the system flow rate increases.
82
Refer to the drawing of centrifugal pump and system operating curves (see figure below).
A centrifugal pump is initially operating at point B. If the pump speed is reduced by one-half, the
new operating point will be located on curve _____ closer to point _____.
1; D
83
Refer to the drawing of a lube oil temperature control system (see figure below).
Initially, the pump is operating with the temperature control valve one-half open. If the temperature
control valve is positioned more closed, the system head loss will __________; and the pump head
will __________.
increase, increase
84
```
Refer to the drawing of a lube oil temperature control system and the associated pump/system
operating curves (see figure below).
If the pump is initially operating at point B, how will the operating point change if the temperature
controller setpoint is decreased by 10°F?
```
Operating point B will be located on curve 2 closer to point C.
85
Refer to the drawing showing two operating points for the same centrifugal pump (see figure below).
Operating point A was generated from pump performance data taken six months ago. Current pump
performance data was used to generate operating point B. Which one of the following would cause
the observed difference between operating points A and B?
The pump internal components have worn since data was collected for operating point A.
86
Refer to the drawing of four sets of centrifugal pump and system operating curves (see figure below).
Each set of curves shows the results of a change in pump and/or system operating conditions.
Initially, a two-speed centrifugal pump is operating at low speed in a cooling water system and
discharging through a heat exchanger. The pump is then switched to high speed.
Which set of operating curves depicts the "before" and "after" conditions described above?
2
87
Refer to the drawing of four sets of centrifugal pump and system operating curves (see figure below).
Each set of curves shows the results of a change in pump and/or system operating conditions.
Initially, a two-speed centrifugal pump is operating at high speed in a cooling water system and
discharging through a heat exchanger. The pump is then switched to low speed.
Which set of operating curves depicts the "before" and "after" conditions described above?
2
88
Refer to the drawing of a cooling water system and the associated pump/system operating curves (see
figure below). Pumps A and B are identical single-speed centrifugal pumps and initially only pump
A is operating.
Pump B is then started. After the system stabilizes, system flow rate will be...
less than twice the initial flow rate.
89
Refer to the drawing of an operating cooling water system (see figure below).
Which one of the following changes to the cooling water system will result in a higher cooling water
pump flow rate and a reduced pump discharge head?
Place the third system heat load in service.
90
A centrifugal pump is located adjacent to the bottom of an open water storage tank. The pump is
taking suction from a river and discharging to the bottom of the tank. Initially the tank was empty and
the pump was operating at point B on the drawing below.
When tank water level reaches 30 feet, the new pump operating point will be located on curve
__________ closer to point __________. (Assume that no other changes occur in the system.)
2; A
91
A centrifugal pump is used to provide makeup water to a storage tank that is 30 feet high. The pump
is located at the base of the tank. The pump can be aligned to fill the tank via a top connection or a
bottom connection using piping of equal lengths and diameters. The tank is currently half full.
With the pump in operation, the pump will have the highest discharge pressure if the pump is aligned
to fill the tank via the ________ connection; and the tank will become full in the least amount of time
if the pump is aligned to fill the tank via the ________ connection.
top; bottom
92
Refer to the drawing of operating curves for a centrifugal pump in a closed water system (see figure
below).
Which one of the following describes the value of head where the two curves cross?
The amount of pump head that is converted to heat and other losses as the water circulates through
the system.
93
Refer to the drawing of an operating cooling water system (see figure below).
Which one of the following changes to the cooling water system will result in a lower cooling water
pump flow rate and a higher pump discharge head?
Isolate one of the two in-service heat loads.
94
A centrifugal pump is used to provide makeup water to a vented storage tank that is 30 feet high. The
pump is located at the base of the tank. The pump can be aligned to fill the tank via a top connection
or a bottom connection using piping of equal lengths and diameters.
With the tank half full, the operating pump will have the lowest discharge pressure if the pump is
aligned to fill the tank via the ________ connection; and the tank will require the longest amount of
time to become completely full if the pump is aligned to fill the tank via the ________ connection.
bottom; top
95
Refer to the pump and system curves (see figure below) for a centrifugal pump operating in a cooling
water system.
Operating point A existed when data was taken six months ago. Operating point B is the current
operating point. Which one of the following could be responsible for the difference between the
operating points?
The pump was rotating slower when the data was collected for operating point A.
96
A motor-driven radial-flow centrifugal pump is used to provide makeup water to a vented storage tank
that is 30 feet high. The pump is located at the base of the tank. The pump can be aligned to fill the
tank via a top connection or a bottom connection using piping of equal lengths and diameters. The
tank is currently empty.
With tank filling underway, the pump motor will have the lowest power demand if the pump is using
the __________ connection; and the tank will require the least amount of time to become completely
full if the pump is using the __________ connection.
top; bottom
97
Refer to the drawing showing two different operating points for the same centrifugal pump operating
in the same cooling water system (see figure below).
Operating point A was generated from pump data collected two days ago. Operating point B was
generated from pump data collected today. Which one of the following would cause the observed
difference between operating points A and B?
The pump discharge valve was more closed when data was collected for operating point B.
98
Refer to the drawing of pump and system operating curves (see figure below). The drawing shows
the operating point for a single-speed centrifugal pump operating in a closed cooling water system
using 6-inch diameter piping.
If the cooling water system 6-inch diameter piping were replaced with 8-inch diameter piping, the new
operating point would occur at a __________ pump head and a __________ pump flow rate.
lower; higher
99
A motor-driven centrifugal pump is operating in an open system with its discharge valve throttled to
50 percent open. If the discharge valve is fully opened, available net positive suction head (NPSH)
will __________; and required NPSH will __________.
decrease; increase
100
Increasing the flow rate from a centrifugal pump by throttling open the discharge valve will cause
pump head to...
decrease and stabilize at a lower value.
101
A centrifugal pump is operating normally in an open system. If the pump recirculation valve is
opened farther, pump discharge pressure will __________; and pump flow rate will __________.
decrease; increase
102
A centrifugal pump is operating normally in an open system with all valves fully open. If the pump
discharge valve is throttled to 50 percent, pump suction pressure will __________; and pump
discharge pressure will __________.
increase; increase
103
A variable-speed centrifugal pump is operating at rated speed in an open system. If the pump speed is
decreased by 50 percent, available net positive suction head (NPSH) will __________; and required
NPSH will __________.
increase; decrease
104
A motor-driven centrifugal pump is operating in an open system with its discharge valve throttled to
50 percent. How will the pump be affected if the discharge valve is fully opened?
Available net positive suction head decreases, and pump differential pressure decreases.
105
A variable speed motor-driven centrifugal pump is operating at 50 percent speed in an open system.
If the pump speed is increased to 100 percent, available net positive suction head (NPSH) will
__________; and required NPSH will __________.
decrease; increase
106
Which one of the following describes a reason for designing centrifugal pumps with suction nozzles
that are larger than their discharge nozzles?
increases pump available net positive suction head by decreasing head loss at the pump suction
107
A centrifugal firewater pump is operating to pressurize a fire main. The pump takes suction on a
water reservoir. The reservoir water level and the eye of the pump impeller are both at sea level.
Given:
$ The pump has a design shutoff head of 100 feet.
$ The required net positive suction head (NPSH) for the pump is 15 feet.
$ The reservoir water temperature is 60°F.
$ A fire hose connected to the fire main is being used to suppress an elevated fire.
At which one of the following fire hose spray nozzle elevations (referenced to sea level) will the pump
first be unable to provide flow? (Disregard head loss in the fire main and fire hose.)
101 feet
108
A centrifugal firewater pump is operating to pressurize a fire main. The pump takes suction from a
water reservoir. A fire hose connected to the fire main is being used to suppress an elevated fire.
Given:
$ The eye of the pump impeller is located 5 feet above the reservoir water level.
$ The pump has a design shutoff head of 120 feet.
$ The required net positive suction head (NPSH) for the pump is 15 feet.
$ The reservoir water temperature is 60°F.
At which one of the following elevations above the eye of the pump impeller will the fire hose spray
nozzle first be unable to provide flow? (Disregard all sources of head loss.)
116 feet
109
A centrifugal firewater pump is operating to pressurize a fire main. The pump takes suction from a
vented water storage tank. A fire hose connected to the fire main is being used to suppress an
elevated fire.
Given:
$ The eye of the pump impeller is located 30 feet below the tank water level.
$ The pump has a design shutoff head of 120 feet.
$ The required net positive suction head (NPSH) for the pump is 15 feet.
$ The tank water temperature is 60°F.
At which one of the following elevations above the eye of the pump impeller will the fire hose spray
nozzle first be unable to provide flow? (Disregard all sources of head loss.)
151 feet
110
A centrifugal cooling water pump is operating in an open system with its discharge valve fully open.
If the discharge valve is repositioned to 50 percent open, the pump=s available net positive suction
head (NPSH) will __________; and the pump=s required NPSH will __________.
increase; decrease
111
A centrifugal firewater pump is operating to pressurize a fire main. The pump takes suction from a
water reservoir. A fire hose connected to the fire main is being used to suppress an elevated fire.
Given:
$ The eye of the pump impeller is located 15 feet below the reservoir water level.
$ The pump has a design shutoff head of 120 feet.
$ The required net positive suction head (NPSH) for the pump is 15 feet.
$ The reservoir water temperature is 60°F.
At which one of the following elevations above the reservoir water level will the fire hose spray nozzle
first be unable to provide flow? (Disregard all sources of head loss.)
121 feet
112
A motor-driven centrifugal pump is operating in a closed-loop cooling water system and is unable to
achieve its rated volumetric flow rate due to cavitation. Which one of the following will enable the
pump to achieve a higher volumetric flow rate before cavitation occurs?
Operate the system at a higher pressure.
113
Refer to the graph that represents the head-capacity characteristics for a single-speed centrifugal
cooling water pump (see figure below).
Which one of the following lists a pair of parameters that could be represented by curves A and B?
(Note: NPSH is net positive suction head.)
Curve A Curve B
Available NPSH Required NPSH
114
Centrifugal pumps A and B are identical except that pump A uses a single-suction impeller while
pump B uses a double-suction impeller. If both pumps are pumping water at the same inlet
temperature, inlet pressure, and flow rate, single-suction pump A typically will have the __________
impeller axial thrust and the __________ required net positive suction head.
greater; greater
115
A motor-driven centrifugal pump is operating normally in a closed cooling water system. When the
pump discharge flow control valve is opened further, the pump is unable to provide the desired
volumetric flow rate due to cavitation. Which one of the following will enable a higher pump
volumetric flow rate before cavitation occurs?
Remove the existing pump and install a same-capacity pump with a lower minimum net positive
suction head requirement.
116
A nuclear power plant is shut down with core decay heat being removed by the residual heat removal
(RHR) system. The reactor coolant system (RCS) has been drained to a mid-loop water level of 20
inches in both the hot and cold legs. The operating RHR pump is taking suction from a hot leg and
discharging 3,000 gpm to a cold leg.
A loss of RHR flow rate due to vortexing will become more likely if the water level in the hot leg is
__________ by six inches or if the RHR system flow rate is __________ by 500 gpm.
lowered; increased
117
Refer to the drawing of an operating cooling water system (see figure below).
The pump is unable to achieve its rated volumetric flow rate due to cavitation. Which one of the
following will enable the pump to achieve a higher volumetric flow rate before cavitation occurs?
Move the surge tank connection closer to the suction of the pump.
118
Refer to the drawing of an operating cooling water system (see figure below). The pump discharge
valve is partially throttled to produce the following initial pump operating parameters:
Pump discharge pressure = 45 psig
Pump suction pressure = 15 psig
Pump flow rate = 120 gpm
After a few hours of operation, the current pump operating parameters are as follows:
Pump discharge pressure = 48 psig
Pump suction pressure = 18 psig
Pump flow rate: = 120 gpm
Which one of the following could be responsible for the change in pump operating parameters?
The surge tank level increased with no other changes to the system.
119
Refer to the drawing of an operating cooling water system (see figure below).
The pump is unable to achieve its rated volumetric flow rate due to cavitation. Which one of the
following will enable the pump to achieve a higher volumetric flow rate before cavitation occurs?
Increase the service water flow rate to the heat exchanger.
120
Refer to the drawing of an operating cooling water system (see figure below).
How will the centrifugal pump flow rate be affected if the surge tank level decreases from 8 feet to 4
feet? (Assume the pump maintains adequate net positive suction head.)
Pump flow rate will remain the same.
121
A reactor is shutdown with decay heat being removed by the residual heat removal (RHR) system.
The operating RHR pump is taking suction from the bottom of a reactor coolant system (RCS) hot leg
and discharging to a cold leg. The RCS has been drained to a mid-loop water level in the hot legs.
Which one of the following makes vortexing at the RHR suction piping hot leg connection more
likely?
RHR pump flow rate is increased from 1,000 gpm to 1,250 gpm
122
Consider the required net positive suction head (NPSHR) and the available net positive suction head
(NPSHA) for a typical centrifugal pump operating normally in a closed cooling water system. If the
pump flow rate increases, __________ will be affected; and if the pump inlet pressure increases,
__________ will be affected.
both NPSHR and NPSHA; only NPSHA
123
How are the required net positive suction head (NPSHR) and available net positive suction head
(NPSHA) for an in-service centrifugal water pump determined?
NPSHA is calculated using water parameter values at the pump inlet, while NPSHR is determined
from pump curves provided by the pump manufacturer.
124
Refer to the drawing of a cooling water system with an operating centrifugal pump (see figure
below).
If the surge tank water level increases from 8 feet to 9 feet, the pump mass flow rate will…
remain the same, because the pump suction and discharge heads will increase by the same
amount.
125
Which one of the following specifies the proper pump discharge valve position and the basis for that
position when starting a large motor-driven radial-flow centrifugal pump?
Discharge valve throttled to reduce motor starting power requirements.
126
A typical single-stage radial-flow centrifugal pump is being returned to service following maintenance
on its three-phase AC induction motor. Which one of the following will occur when the pump is
started if two of the three motor power leads were inadvertently swapped during restoration?
The pump will rotate in the reverse direction with reduced or no flow rate.
127
If the speed of a positive displacement pump is increased, the available net positive suction head will
__________; and the pump will operate __________ cavitation.
decrease; closer to
128
An increase in positive displacement pump speed will cause the available net positive suction head for
the pump to...
decrease, due to the increase in fluid flow rate
129
The minimum required net positive suction head for a typical positive displacement pump will
increase the most if the pump...
speed increases from 1,200 rpm to 1,600 rpm
130
Which one of the following describes the proper location for a relief valve that will be used to prevent
exceeding the design pressure of a positive displacement pump and associated piping?
On the pump discharge piping upstream of the discharge isolation valve.
131
A positive displacement pump (PDP) is operating in an open system. PDP parameters are as follows:
PDP speed = 1,000 rpm
PDP discharge pressure = 2,000 psig
PDP suction pressure = 50 psig
PDP flow rate = 150 gpm
Which one of the following changes will cause PDP flow rate to exceed 200 gpm?
PDP speed is increased to 1,500 rpm.
132
If the fully open discharge valve of a reciprocating positive displacement pump is closed
approximately 10 percent, pump flow rate will __________; and pump head will __________.
(Assume "ideal" pump response.)
remain constant; increase
133
A variable-speed positive displacement pump is operating at 100 rpm with a flow rate of 60 gpm in an
open system. To decrease pump flow rate to 30 gpm, pump speed must be decreased to
approximately...
50 rpm
134
Which one of the following conditions will result in the greatest increase in volumetric flow rate
through a positive displacement pump?
Doubling the pump speed.
135
Which one of the following describes single-speed pump operating characteristics?
Positive displacement pumps deliver a constant flow rate over a variety of heads.
136
A positive displacement pump (PDP) is operating in an open water system. PDP parameters are as
follows:
PDP speed = 480 rpm
PDP discharge pressure = 1,000 psig
PDP suction pressure = 10 psig
PDP flow rate = 60 gpm
Which one of the following changes will cause PDP flow rate to exceed 100 gpm?
PDP speed is increased to 900 rpm.
137
An ideal (no slip) reciprocating positive displacement pump is operating to provide makeup water to a
reactor coolant system that is being maintained at 1,000 psig. The discharge valve of the pump was
found to be throttled to 80 percent open.
If the valve is subsequently fully opened, pump flow rate will __________; and pump head will
__________.
remain constant; decrease
138
A variable-speed positive displacement pump is operating at 100 rpm with a flow rate of 60 gpm in an
open system. To decrease pump flow rate to 25 gpm, pump speed must be decreased to
approximately...
42 rpm.
139
Which one of the following will result in the greatest increase in volumetric flow rate to a system that
is currently receiving flow from a positive displacement pump operating at 400 rpm with a discharge
pressure of 100 psig?
Start a second identical positive displacement pump in parallel with the first.
140
A section of pipe is being hydrostatically tested to 1,400 psig using a positive displacement pump.
The operating characteristics of the positive displacement pump are shown in the drawing below.
Which one of the following could cause the difference between the expected and the actual pump
performance?
Pump internal leakage is greater than expected.
141
Which one of the following conditions will result in the greatest increase in volumetric flow rate from
a positive displacement pump operating at 300 rpm and a discharge pressure of 100 psig?
Increasing pump speed to 700 rpm
142
An ideal (no slip) reciprocating positive displacement pump is operating in an open system to provide
makeup water to a coolant system that is being maintained at 800 psig. The discharge valve of the
pump is full open.
If the pump discharge valve is subsequently throttled to 80 percent open, pump flow rate will
__________; and pump head will __________.
remain constant; increase
143
A pump is needed to supply fuel oil from a day tank to a diesel engine fuel injection system. The
pump must maintain a nearly constant flow rate with a minimum of discharge pressure fluctuations as
system pressure varies between 200 psig and 1,900 psig.
Which one of the following types of pumps would be most suitable for this application?
Rotary positive displacement
144
An ideal positive displacement pump is pumping to a system operating at 100 psig. Assume pump
speed is constant, zero pump slip, and pump backpressure remains within normal pump operating
limits.
If system pressure increases to 200 psig, the pump head will __________; and pump flow rate will
__________.
increase; remain the same
145
Use the following drawing of system and pump operating curves for a positive displacement pump
with discharge relief valve protection to answer the following question.
A positive displacement pump is initially supplying water at 40 gpm with a pump discharge pressure
of 400 psia. If pump speed is increased until pump flow rate is 80 gpm, what is the new pump
discharge pressure
1,000 psia
146
Use the following drawing of system and pump operating curves for an operating positive
displacement pump with relief valve protection to answer the following question.
A positive displacement pump is initially supplying water at 40 gpm with a pump discharge pressure
of 200 psia. If pump speed is increased until pump flow rate is 80 gpm, what is the new pump
discharge pressure?
800 psia
147
Refer to the drawing of operating curves for a positive displacement pump in a closed water system
(see figure below).
Which one of the following describes the value of the head where the two curves cross?
The amount of pump head that is converted to heat as the water circulates through the system.
148
Refer to the drawing of operating curves for a positive displacement pump in a closed water system
(see figure below).
Which one of the following describes the value of the pump head where the two curves cross?
The amount of pump head needed to maintain the system flow rate.
149
When starting a positive displacement pump, why must the pump discharge valve be fully open?
Ensures integrity of the pump and system piping.
150
What is the purpose of the relief valve located between the pump outlet and the discharge isolation
valve of many positive displacement pumps?
Protect the pump and discharge piping from overpressure if the discharge valve is closed during
pump operation
151
A positive displacement pump should be started with its suction valve __________ and its discharge
valve __________.
fully open; fully open
152
A positive displacement pump should be started with its suction valve __________ and its discharge
valve __________.
open; open
