Valves Flashcards
A vertical safety valve has a compressed spring assembly that is applying 1,200 lbf to the top of the valve disk in opposition to system pressure. System pressure is being exerted on the underside of the valve disk that is 3 inches in diameter.
Which one of the following is the approximate system pressure at which the safety valve will open?
170 psig
Which one of the following describes the function of a safety valve?
Provide overpressure protection to limit the internal pressure in vessels
A vertical safety valve with a 3-inch diameter disk has a spring applying 1,000 lbf to the top of the valve disk in opposition to system pressure. Which one of the following is the approximate system pressure at which the safety valve will begin to open?
141 psig
A vertical safety valve has a compressed spring assembly that is applying 2,500 lbf to the top of the valve disk in opposition to system pressure. System pressure is being exerted on the underside of the valve disk that is 5 inches in diameter.
What is the approximate system pressure at which the safety valve will open?
127 psig
A vertical safety valve with a 2-inch diameter disk has a compressed spring applying 2,400 lbf to the top of the valve disk in opposition to system pressure. Which one of the following is the approximate system pressure at which the safety valve will open?
764 psig
Given the following pressure specifications for operation of a main steam safety valve (MSSV):
Setpoint pressure (MSSV starts to open) = 1,200 psia Maximum pressure (MSSV will be fully open) = 1,230 psia Reseat pressure (MSSV will be fully closed) = 1,140 psia
Which one of the following is the percent blowdown for the MSSV?
5.0
Blowdown% = P(set)-P(reset)
/ P(set) *100%
A completely full water storage tank is being hydrostatically tested to 100 psig using a positive displacement pump (PDP) with a smooth and constant discharge flow rate of 10 gpm. The tank is
protected by a safety valve and a relief valve; both valves discharge to the atmosphere. Each valve has an opening setpoint of 105 psig and a maximum rated discharge flow rate of 6 gpm. The PDP is
inadvertently left running when tank pressure reaches 100 psig.
With the PDP still running, tank pressure will stabilize __________ 105 psig; and the greater mass flow rate will be coming from the __________ valve.
above; safety
Given the following pressure specifications for a safety relief valve (SRV):
Setpoint pressure (SRV will start to open) = 1,200 psia Maximum pressure (SRV will be fully open) = 1,242 psia Reseat pressure (SRV will be fully closed) = 1,152 psia
Which one of the following is the percent accumulation for the SRV?
3.5 percent
Accumulation % = P(fullopen)-P(setpoint)
/ P(setpoint) *100%
A completely full water storage tank is being hydrostatically tested to 200 psig using a positive displacement pump (PDP) with a smooth and constant discharge flow rate of 8 gpm. The tank is
protected by a relief valve and a safety valve; both valves discharge to the atmosphere. Each valve has an opening setpoint of 205 psig and a maximum rated discharge flow rate of 6 gpm. The PDP is
inadvertently left running when tank pressure reaches 200 psig.
When conditions stabilize with the PDP still running, the relief valve will be __________ open; and the safety valve will be discharging a flow rate of approximately __________ to the atmosphere.
partially; 6 gpm
Tank A is protected by a relief valve and Tank B is protected by a safety valve. Each valve has an opening setpoint of 205 psig
and a maximum rated discharge flow rate of 8 gpm. The tanks are being hydrostatically tested to 200 psig. Each tank is being supplied with a smooth and constant flow rate of 2 gpm from separate positive displacement pumps (PDPs). Both PDPs are
inadvertently left running when tank pressures reach 200 psig. With the PDPs running continuously, what will be the resulting status of the relief and safety valves?
Relief Valve Status: Safety Valve Status:
Partially Open. Cycling between full open &
Full open
A completely full water storage tank is being hydrostatically tested to 200 psig using a positive displacement pump (PDP) with a smooth and constant discharge flow rate of 8 gpm. The tank is
protected by a relief valve and a safety valve that discharge to the atmosphere. The valves have the following characteristics:
- The relief valve opening setpoint is 200 psig with an accumulation
of 5 percent. - The safety valve opening setpoint is 240 psig with a blowdown of
5 percent. - Both valves have a maximum discharge flow rate of 6 gpm.
The PDP is inadvertently left running when tank pressure reaches 200 psig.
When conditions stabilize with the PDP still running, the relief valve will be __________ open; and the safety valve will be discharging a flow rate of approximately __________ to the atmosphere.
fully; 2 gpm
A main steam system uses a combination of safety and relief valves for overpressure protection. Which one of the following describes a major design consideration for installing both types of valves in the same system?
The relief valves are installed to prevent unnecessary opening of the safety valves during a steam pressure transient.
The primary purpose of a pressure relief valve is to…
maintain system integrity.
The difference between the setpoint pressure at which a safety valve opens and the pressure at which it closes is called..
blowdown.
The difference between the setpoint pressure at which a relief valve begins to open and the pressure at which it is fully open is called…
accumulation.
Which one of the following is a difference between a typical relief valve and a typical safety valve?
A relief valve gradually opens as pressure increases above the setpoint pressure whereas a safety valve pops open at the setpoint pressure.
Water storage tanks A and B are identical except that tank A receives overpressure protection from a relief valve, whereas tank B uses a safety valve. The relief valve and safety valve have the same
pressure setpoints and design flow rates.
Water is continuously added to each tank at the same rate (50 percent of the design flow rate of the relief and safety valves). After the tanks are completely full, tank A pressure will __________; and
tank B pressure will __________.
stabilize slightly above the pressure setpoint; fluctuate within a few percent of the pressure setpoint
Vessels A and B are identical except that vessel A receives overpressure protection from an installed safety valve. Vessel B has an installed relief valve. The safety and relief valves have the same
pressure setpoint and design flow rate.
Water is continuously added to each vessel at the same rate (50 percent of the design flow rate of the safety and relief valves). After vessel pressure reaches the setpoint for each valve, vessel A pressure will __________; and vessel B pressure will __________.
fluctuate within a few percent of the pressure setpoint; stabilize slightly above the pressure setpoint
A completely full water storage tank is being hydrostatically tested to 200 psig using a positive displacement pump (PDP) with a smooth and constant discharge flow rate of 6 gpm. The tank is
protected by two relief valves that discharge to the atmosphere. The relief valves have the following characteristics:
- Relief valve A opening setpoint is 200 psig with an accumulation
of 1.5 percent. - Relief valve B opening setpoint is 200 psig with an accumulation
of 3.0 percent. - Each valve has linear flow rate characteristics and a maximum
discharge flow rate of 6 gpm.
The PDP is inadvertently left running when tank pressure reaches 200 psig.
With the PDP running continuously, what will be the discharge flow rates of the relief valves when tank pressure stabilizes?
Relief Valve A. Relief Valve B
4 gpm 2 gpm
A completely full water tank is being hydrostatically tested to 180 psig using a positive displacement pump (PDP) with a smooth and constant discharge flow rate of 6 gpm. The tank is protected by two relief valves that discharge to the atmosphere. The relief valves have the following characteristics:
- Relief valve A opening setpoint is 180 psig with an accumulation
of 5 percent. - Relief valve B opening setpoint is 200 psig with an accumulation
of 5 percent. - Each relief valve has linear flow rate characteristics and a
maximum flow rate of 4 gpm.
The PDP is inadvertently left running when tank pressure reaches 180 psig.
With the PDP still running, at what pressure will the tank stabilize?
205 psig
In a comparison between a globe valve and a gate valve in the same water system application, the gate valve has a __________ pressure drop when fully open and is the __________ choice for throttling.
lower; poorer
Consider a 3-inch gate valve and a 3-inch globe valve in the same water system application. If both valves are fully open, the gate valve produces the __________ head loss and the __________ flow
rate.
smaller; larger
Which one of the following statements describes the flow rate characteristics of a typical gate valve in an operating water system?
The first 25 percent of valve disk travel in the open direction will produce a greater change in flow rate than the last 25 percent of valve disk travel
Which one of the following statements describes the flow rate characteristics of a typical globe valve in an operating water system?
The first 25 percent of valve disk travel in the open direction will produce a greater increase in flow rate than the last 25 percent of valve disk travel
A control valve is most likely to experience cavitation when the valve is almost fully __________ because of a relatively __________ pressure drop across the valve seat.
closed; large
Which one of the following statements describes the throttling characteristics of a typical globe valve
A. The first third of valve disk travel in the open direction will result
in approximately one-third of full flow rate.
B. The first third of valve disk travel in the open direction will
produce a smaller increase in flow rate than the last third of valve
disk travel.
C. The first third of valve disk travel in the open direction will
produce a greater increase in flow rate than the last third of valve
disk travel.
D. The first two-thirds of valve disk travel in the open direction will
produce approximately the same increase in flow rate as the last
third of valve disk travel.
The first third of valve disk travel in the open direction will produce a greater increase in flow rate than the last third of valve disk travel
Which one of the following types of similarly sized valves in an operating water system produces the least frictional head loss when fully open?
A. Ball
B. Globe
C. Butterfly
D. Swing check
Ball
Consider a 6-inch globe valve and a 6-inch gate valve in the same water system application. Typically, the valve that requires the most linear disk travel from fully closed to fully open is the __________ valve; and the valve that produces the smallest pressure drop when fully open is the __________ valve
Gate; Gate
Subcooled water was flowing through a throttled valve with the following initial parameters:
Inlet pressure = 60 psia Outlet pressure = 50 psia Flow rate = 800 gpm
The valve was opened fully and the following parameters currently exist:
Inlet pressure = 60 psia Outlet pressure = 55 psia
What is the approximate flow rate through the fully open valve?
A. 400 gpm
B. 566 gpm
C. 635 gpm
D. Cannot be determined without additional information.
Cannot be determined without additional information.
Subcooled water is flowing through a throttled valve in an open system. The initial steady-state conditions for the throttled valve were as follows:
Inlet pressure = 60 psia Outlet pressure = 44 psia Flow rate = 800 gpm
After four hours, the current steady-state conditions for the throttled valve are as follows:
Inlet pressure = 63 psia Outlet pressure = 54 psia Flow rate = 600 gpm
Which one of the following could be responsible for the difference between the initial and current conditions for the throttled valve?
A. The throttled valve was opened farther.
B. The throttled valve was closed farther.
C. Another valve, located upstream of the throttled valve, was
partially closed.
D. Another valve, located downstream of the throttled valve, was
partially closed.
Another valve, located downstream of the throttled valve, was partially closed.
Subcooled water is flowing through a throttled valve in an open system. The initial steady-state conditions for the throttled valve are as follows:
- Inlet pressure = 60 psia
- Outlet pressure = 44 psia
- Flow rate = 800 gpm
After four hours, the current steady-state conditions for the throttled valve are as follows:
- Inlet pressure = 62 psia
- Outlet pressure = 40 psia
- Flow rate = 600 gpm
Which one of the following could be responsible for the difference between the initial and current conditions for the throttled valve?
A. The throttled valve was opened more.
B. The throttled valve was closed more.
C. Another valve, located upstream of the throttled valve, was
partially closed.
D. Another valve, located downstream of the throttled valve, was
partially closed.
The throttled valve was closed more.
How will a typical motor-operated valve respond to a loss of electrical power to the valve actuator?
Remain as is
An operator attempts to close a fully-open upright manual gate valve to isolate a pump in a cooling water system that has been cooled down for maintenance. However, the operator is unable to rotate the handwheel in the close direction.
Which one of the following could cause this condition?
A. A hydraulic lock has developed under the valve disk.
B. A hydraulic lock has developed in the valve bonnet between the
valve disk and the packing gland.
C. The two halves of the valve disk have expanded and are jammed
against the valve seats.
D. The valve disk has jammed against its backseat by the difference
in the thermal contraction of the stem and the bonnet.
The valve disk has jammed against its backseat by the difference in the thermal contraction of the stem and the bonnet.
When manually positioning a motor-operated valve, why must care be taken to avoid using excessive valve seating/backseating force?
The valve may bind during subsequent operation.
After an adjustment of the packing gland on a valve that had a minor packing leak, an operator attempts to operate the valve, but finds the valve is stuck. What is the most probable cause?
A. The disk separated from the valve stem as a result of
overtightening the packing gland.
B. The operator placed the valve in the wrong position for adjusting
the packing gland.
C. The valve was overtorqued in the closed direction during the
packing gland adjustment.
D. The maintenance technician overtightened the packing gland,
causing the stem to bind.
The maintenance technician overtightened the packing gland, causing the stem to bind.
An adjustment has just been completed on the packing gland of an automatic valve to stop a minor stem leak. Which one of the following can occur if the technician overtightened the packing gland?
A. Decreased cooling flow to the valve internals.
B. Separation of the valve disk from the valve stem.
C. Misalignment of the valve position limit switches.
D. Increased stroke time from fully open to fully closed.
Increased stroke time from fully open to fully closed.
Which one of the following describes the function and use of the backseat on a manual valve?
A. Removes pressure from the packing/stuffing box and is typically
used to isolate the stuffing box for valve repacking.
B. Removes pressure from the packing/stuffing box and is typically
used when needed to isolate packing leakage.
C. Acts as a backup in case the primary seat leaks and is typically
used during system isolation for personnel protection.
D. Acts as a backup in case the primary seat leaks and is typically
used when needed to prevent the primary seat from leaking
excessively.
Removes pressure from the packing/stuffing box and is typically used when needed to isolate packing leakage.
When manually closing a motor-operated valve, why must the operator avoid using excessive valve seating force?
A. The valve may bind and cause the motor to trip on overload
during subsequent remote operation.
B. The valve actuator clutch may be damaged and disable
subsequent remote operation.
C. The valve stem limit switches may be damaged and cause
inaccurate remote valve position indication.
D. The valve actuator position indicator may be damaged and
cause inaccurate local valve position indication.
A. The valve may bind and cause the motor to trip on overload during subsequent remote operation.
After manually positioning a motor-operated valve, the valve actuator motor is reengaged by…
A. taking the manual declutch lever to the disengage position.
B. taking the manual declutch lever to the engage position.
C. racking in the valve actuator motor breaker.
D. energizing the valve actuator motor.
D. energizing the valve actuator motor.
When the manual declutch lever of a motor-operated valve is moved out of the normal position, it __________ the motor and __________ the handwheel.
A. engages; engages
B. engages; disengages
C. disengages; engages
D. disengages; disengages
C. disengages; engages
A typical motor-operated valve with a declutch lever is installed in an emergency core cooling system (ECCS) application. The ECCS actuation signal is designed to energize the valve motor and open the valve. The valve is currently open, but being manually/locally closed by a technician as required by a surveillance test procedure. The declutch lever has been operated and released, and the valve is being closed by operation of the valve handwheel.
If an ECCS actuation signal is received, how will the valve be affected?
A. The handwheel will disengage and the valve will automatically
open.
B. The handwheel will disengage and the valve will remain in the
current position.
C. The handwheel will remain engaged and the valve will
automatically open.
D. The handwheel will remain engaged and the technician can
continue to close the valve.
A. The handwheel will disengage and the valve will automatically open.
A surveillance test procedure is being performed on a typical motor-operated valve (MOV) with a declutch lever that is used in an emergency core cooling system (ECCS) application. The declutch
lever has been operated and released, and the valve is being manually/locally opened by a technician. The MOV breaker is closed as required by the surveillance test procedure. During operation of the valve handwheel, an ECCS actuation signal is received that normally energizes the valve motor and closes the valve.
How will the valve be affected by the actuation signal?
A. The handwheel will disengage and the valve will automatically
close.
B. The handwheel will disengage and the valve will remain in the
current position.
C. The handwheel will remain engaged and the valve will
automatically close.
D. The handwheel will remain engaged and the technician can
continue to open the valve.
A. The handwheel will disengage and the valve will automatically close.
A typical motor-operated valve (MOV) has just been opened from the main control room, and the breaker for the MOV has been opened. A plant operator has been directed to close the MOV locally for a surveillance test.
If the operator attempts to turn the MOV handwheel in the clockwise direction without first operating the declutch lever, which one of the following will occur?
A. The handwheel will not turn, and the valve stem will not move.
B. The handwheel will turn, but the valve stem will not move.
C. The handwheel will turn, and the valve stem will move toward the
closed position because the clutch is automatically engaged
when the handwheel is turned.
D. The handwheel will turn, and the valve stem will move toward the
closed position because the clutch is automatically engaged
when the breaker is opened
B. The handwheel will turn, but the valve stem will not move.
Which one of the following types of similarly sized valves requires the most manual valve stem rotation to move the valve from fully open to fully closed? (Assume that each valve has a non-rising
stem.)
A. Ball
B. Gate
C. Plug
D. Butterfly
B. Gate
A stop check valve is a type of check valve that…
A. cannot be shut remotely.
B. can be used to prevent flow in both directions.
C. contains both a gate valve disk and a check valve disk.
D. can be opened manually to allow flow in both directions
B. can be used to prevent flow in both directions.
Which one of the following valves is used to control the direction of fluid flow and prevent backflow in a system?
A. Safety valve
B. Relief valve
C. Divert valve
D. Check valve
D. Check valve
Two common types of check valves used in nuclear power plants are…
A. globe and gate.
B. ball and plug.
C. swing and lift.
D. needle and angle
C. swing and lift.
A typical check valve is designed to…
A. permit flow in only one direction.
B. prevent system overpressure.
C. isolate system components.
D. perform automatic pump venting.
A. permit flow in only one direction.
Check valves are normally used to prevent…
A. overpressurization of non-operating system piping and
components.
B. backflow through nonoperating components or flowpaths.
C. pump runout by providing a constant backpressure.
D. pump cavitation by keeping nonoperating systems filled.
B. backflow through nonoperating components or flowpaths.
Which one of the following is the type of valve used to control the direction of fluid flow through a system and prevent backflow?
A. Butterfly valve
B. Gate valve
C. Globe valve
D. Check valve
D. Check valve
To verify that a manual valve in an operating system is closed, the operator should observe valve position indication and operate the valve handwheel in the…
A. open direction until flow sounds are heard, then close the valve
using normal force.
B. close direction using normal force and verify there is no
substantial handwheel movement.
C. close direction until it stops, then close it an additional one-half
turn using additional force if necessary.
D. open direction until the valve stem moves in the open direction,
then close the valve using normal force.
B. close direction using normal force and verify there is no substantial handwheel movement.
To verify the position of a fully open manual valve in an operating system, the operator should operate the valve handwheel…
A. in the open direction until the valve is backseated one-half turn.
B. to fully close the valve, then open the valve to the fully open
position.
C. in the closed direction, then open the valve to its previously open
position.
D. to open the valve until it touches the backseat, then close the
valve to the desired position.
C. in the closed direction, then open the valve to its previously open position.
Consider a typical gate valve and a typical globe valve in the same water system application. The globe valve generally has a __________ pressure drop when fully open; and is __________
commonly used for throttling system flow.
A. smaller; less
B. larger; more
C. smaller; more
D. larger; less
B. larger; more
Gate valves should not be used to throttle fluid flow because…
A. the tortuous flow path through a gate valve body makes flow
control difficult.
B. gate valves must be fully opened and backseated to prevent
stem leakage.
C. the turbulent flow created by a partially opened gate valve will
cause erosion damage to the valve seat.
D. the large size of the gate valve disk requires an oversized
actuator to accurately position the disk.
C. the turbulent flow created by a partially opened gate valve will cause erosion damage to the valve seat.
Consider a 3-inch gate valve and a 3-inch globe valve in the same water system application. If both valves are fully open, the globe valve produces the __________ head loss and the __________ flow
rate.
A. larger; larger
B. larger; smaller
C. smaller; larger
D. smaller; smaller
B. larger; smaller
Which one of the following is a generally accepted method for locally verifying that a manual valve is fully closed in a depressurized static piping system?
A. Check a downstream flow gauge to be indicating zero flow.
B. Visually observe the valve rising-stem threading to be fully
exposed.
C. Attempt to turn the valve handwheel in the close direction and
verify no movement.
D. Compare an upstream and downstream pressure gauge to
ensure zero differential pressure.
C. Attempt to turn the valve handwheel in the close direction and verify no movement.
In a comparison between a typical gate valve and a typical globe valve in the same water system application with both valves fully open, the gate valve has a __________ pressure drop and is
normally used in __________ flow applications.
A. larger; throttling
B. larger; on/off
C. smaller; throttling
D. smaller; on/off
D. smaller; on/off
To verify a manual valve in an operating system is closed, the operator should observe valve position indication and operate the valve handwheel in the…
A. open direction at least one full rotation, then close the valve
using normal force.
B. open direction until system flow is observed, then close the valve
using normal force.
C. close direction using normal force and verify there is no
substantial handwheel movement.
D. close direction using normal force, then operate the valve
handwheel an additional one-quarter turn in the close direction.
C. close direction using normal force and verify there is no substantial handwheel movement.
Which one of the following is a disadvantage associated with using a gate valve, versus a globe valve, to throttle flow in a cooling water system?
A. The tortuous flow path through a throttled gate valve body
makes flow control difficult.
B. A gate valve will experience stem leakage unless it is fully
opened and backseated.
C. The turbulent flow created by a throttled gate valve will cause
erosion damage to the valve seat.
D. A fully open gate valve will produce a greater system head loss
than a fully open globe valve.
C. The turbulent flow created by a throttled gate valve will cause erosion damage to the valve seat.
After an adjustment of the packing gland on a valve that had a minor packing leak, the operator attempts to operate the valve, but finds that the valve is stuck. What is the most probable cause?
A. The disk separated from the valve stem as a result of
overtightening the packing gland.
B. The operator placed the valve in the wrong position for adjusting
the packing gland.
C. The valve was overtorqued in the close direction during the
packing gland adjustment.
D. The maintenance technician overtightened the packing gland,
causing the stem to bind.
D. The maintenance technician overtightened the packing gland, causing the stem to bind.
Which one of the following is not a generally accepted method for locally verifying that a valve is open?
A. Observe local flow rate instrumentation.
B. Check the local valve position indicator indicates OPEN.
C. Turn the valve operator in the close direction and verify that
some movement occurs.
D. Attempt to turn the valve operator in the open direction and
verify that no movement occurs.
D. Attempt to turn the valve operator in the open direction and verify that no movement occurs.
Why are gate valves generally not used to throttle water flow?
A. Rapid changes in flow direction inside the valve cause a large
unrecoverable system head loss.
B. Gate valves experience stem leakage unless they are fully open
or fully closed.
C. The turbulent flow created by a partially opened gate valve
causes excessive seat and disk wear.
D. Flow rate through a gate valve is not proportional to the
differential pressure across the valve.
C. The turbulent flow created by a partially opened gate valve causes excessive seat and disk wear.
In a comparison between globe valves and gate valves in the same water system application, globe valves…
A. are less effective at throttling flow.
B. are less effective as pressure regulating valves.
C. produce a smaller pressure decrease when fully open.
D. require less force to open against large differential pressures.
D. require less force to open against large differential pressures.
In a comparison between gate valves and globe valves in the same water system application, gate valves…
A. are more effective at throttling flow.
B. are more effective as pressure regulating valves.
C. produce a larger pressure decrease when fully open.
D. require more force to open against large differential pressures.
D. require more force to open against large differential pressures.
In a comparison between butterfly valves and ball valves, __________ valves are generally more leak- tight in high pressure applications; and __________ valves generally exhibit the smaller pressure decrease when fully open.
A. ball; ball
B. ball; butterfly
C. butterfly; ball
D. butterfly; butterfly
A. ball; ball
A gate valve is generally a poor choice for throttling fluid flow because…
A. the turbulent flow created by a partially opened gate valve can
cause extensive damage to the valve.
B. the tortuous path through a gate valve body can make flow
control difficult.
C. excessive stem leakage will result unless the gate valve is fully
open or fully closed.
D. the head loss from a throttled gate valve will result in an
unacceptable reduction in system flow rate.
A. the turbulent flow created by a partially opened gate valve can cause extensive damage to the valve.
In a comparison between ball valves and butterfly valves in the same water system application, the valve that typically would allow more leakage when fully closed with a high differential pressure is the __________ valve; and the valve that typically would cause the greater pressure loss when fully open is the __________ valve.
A. ball; butterfly
B. ball; ball
C. butterfly; butterfly
D. butterfly; ball
C. butterfly; butterfly
A typical motor-operated valve has been returned to service following a complete maintenance overhaul of the valve and actuator. The valve was remotely opened and closed to verify operability. The measured valve stroke time in each direction was 15 seconds, which is 25 percent longer than normal.
Which one of the following could have caused the increased stroke time?
A. The valve position limit switches were removed and were not reinstalled.
B. The valve torque limit switches were misadjusted to open at half their normal setpoints.
C. The valve was packed with improved packing material having a lower friction coefficient.
D. The valve stem packing gland was overtightened after the packing material was replaced.
D. The valve stem packing gland was overtightened after the packing material was replaced.
In a comparison between ball valves and butterfly valves in the same water system application, the valve that would typically be more leak-tight when fully closed with a high differential pressure is the __________ valve; and the valve that typically results in the greater pressure decrease when fully open is the __________ valve.
A. ball; butterfly
B. ball; ball
C. butterfly; butterfly
D. butterfly; ball
A. ball; butterfly
In a comparison between ball valves and butterfly valves in the same cooling water system application, the valve that would typically experience the greater seat leakage when fully closed with a large differential pressure is the __________ valve; and the valve that would typically cause the smaller head loss when fully open is the __________ valve.
A. ball; butterfly
B. ball; ball
C. butterfly; butterfly
D. butterfly; ball
D. butterfly; ball
Which one of the following describes the operation of a safety valve installed on a high pressure steam system?
A. A safety valve is initially lifted off its seat by system pressure,
then is forced fully open by an air-operated piston.
B. As system pressure increases to the safety setpoint, the pressure
overcomes spring force on the valve operator, causing the valve
to open.
C. A safety valve will remain open until system pressure has been
reduced to the pilot valve actuation setpoint.
D. When the open safety valve has returned system pressure to the
lifting set point, a combination of air and steam pressure above
the valve disk closes the valve.
B. As system pressure increases to the safety setpoint, the pressure
overcomes spring force on the valve operator, causing the valve to open
Which one of the following valves provides overpressure protection to limit the internal pressure in vessels and thus protect personnel and equipment?
A. Safety
B. Control
C. Sentinel
D. Pressure regulating
A. Safety
Which one of the following statements describes the operation of reactor pressure vessel safety valves?
A. An open safety valve will close when reactor pressure decreases
enough for gravity and spring tension to overcome the effect of
reactor pressure on the main valve disk.
B. An open safety valve will close when the pilot valve senses a
reduced reactor pressure and isolates reactor pressure to the
main valve disk.
C. When reactor pressure reaches the lift set point, the safety valve
begins to open and will modulate to a position that is directly
proportional to reactor pressure.
D. When reactor pressure reaches the lift set point, a pilot valve
closes to create a DP across the main valve disk, which
overcomes gravity and spring tension to open the valve.
A. An open safety valve will close when reactor pressure decreases
enough for gravity and spring tension to overcome the effect of reactor pressure on the main valve disk.
Vessel “A” is completely filled with subcooled water at 80°F and Vessel “B” is in a saturated, two phase condition. Both vessels are currently pressurized to 50 psig and isolated.
If both relief valves fully open simultaneously, the faster pressure reduction will initially occur in vessel ________ and the faster mass loss will initially occur in vessel ________.
A. A; A
B. A; B
C. B; A
D. B; B
A. A; A
Vessel “A” is completely filled with subcooled water at 80°F and Vessel “B” is in a saturated, two phase condition. Both vessels are currently pressurized to 50 psig and isolated.
If both relief valves fully open simultaneously, the faster pressure reduction will occur in vessel ______; and if both relief valves close at 40 psig, the greater mass loss will have occurred in vessel _____.
A. A; A
B. A; B
C. B; A
D. B; B
B. A; B
If a pressure control valve at the outlet of a heat exchanger opens farther, system flow rate will _____ and system head loss will _____.
A. increase; decrease
B. increase; increase
C. decrease; decrease
D. decrease; increase
A. increase; decrease
If a cooling water outlet valve is partially closed from the full open position, heat exchanger cooling water pressure upstream of the valve will ________ and the temperature of the lube oil exiting
the heat exchanger will ________.
A. increase; decrease
B. increase; increase
C. decrease; decrease
D. decrease; increase
B. increase; increase
When a discharge valve is opened to atmosphere, the pressure on the upstream side of the valve will…
A. remain the same, and the pressure on the downstream side will
increase.
B. increase, and the pressure on the downstream side will remain
the same.
C. remain the same, and the pressure on the downstream side will
decrease.
D. decrease, and the pressure on the downstream side will remain
the same.
D. decrease, and the pressure on the downstream side will remain
the same.
One of the system curves shows system head loss with the flow control valve 25% open. The other system curve shows system head loss with the flow control valve 100% open. The pump is operating and the valve is initially 25% open, resulting in a pump flow rate of 800 gpm.
If the flow control valve is subsequently fully opened, pump flow rate through the valve will be approximately…
A. 400 gpm.
B. 1,200 gpm.
C. 1,600 gpm.
D. 3,200 gpm
B. 1,200 gpm
At first this may seem to be a question requiring a calculation. It is not. The key to answering this question is remembering that the most common valve used for flow control is a globe valve and that
the NRC bank assumes all globe valves are fast acting If a valve is fast acting a large percentage of the rated flow is achieved with the initial opening of the valve and certainly within the first 25%. Opening it further will INCREASE flow but certainly not by a factor of 2 or 4
Which one of the following valves is most likely to be used with a throttling positioner?
A. Stop valve
B. Globe valve
C. Gate valve
D. Butterfly valve
B. Globe valve
A throttle positioner is a valve actuator that allows the valve to be placed in a midposition to allow throttling of a valve. Globe valves have good throttling characteristics
Some valve positioning (drive) devices are capable of stopping the valve between a fully open and a fully closed (throttled) position. Which one of the following valves has the best throttling
characteristics?
A. Stop valve
B. Globe valve
C. Gate valve
D. Butterfly valve
B. Globe valve
Globe valves are preferred over gate valves for throttling because…
A. flow control is more linear for globe valves than for gate valves.
B. head loss from a fully open globe valve is smaller than the head
loss from a fully open gate valve.
C. valve position indication for a midpositioned valve is more
reliable for globe valves than for gate valves.
D. valve motor operators are more adaptable to globe valves than
to gate valves
A. flow control is more linear for globe valves than for gate valves.
Gate valves are most often used to…
A. protect system integrity by relieving excess pressure.
B. redirect fluid flow in an operating system.
C. isolate fluid flow in an operating system.
D. control fluid flow rate in an operating system.
C. isolate fluid flow in an operating system.
Which one of the following is not a generally accepted method for locally verifying that a valve is open?
A. Observe local flow rate instrumentation.
B. Check the local valve position indicator indicates “open.”
C. Turn the valve operator in the “close” direction and verify that
some movement occurs.
D. Attempt to turn the valve operator in the “open” direction and
verify that no movement occurs.
D. Attempt to turn the valve operator in the “open” direction and
verify that no movement occurs
An adjustment has just been completed on the packing gland of an automatic valve to stop a minor stem leak. Which one of the following can occur if the technician over tightened the packing gland?
A. Decreased cooling flow to the valve internals
B. Separation of the valve disk from the valve stem
C. Misalignment of the valve position limit switches
D. Increased stroke time from fully open to fully closed
D. Increased stroke time from fully open to fully closed
When transferring a valve controller from the manual mode to the automatic mode, the automatic valve controller output signal should be ____________ the manual valve controller output signal at
the time of transfer.
A. equal to
B. greater than
C. less than
D. increasing with
A. equal to
When shifting from automatic to manual control of a typical valve controller, why should the controller manual and automatic output signals be matched?
A. To prevent a sudden valve repositioning upon the transfer
B. To satisfy the controller transfer interlocks
C. To move the valve to the new position prior to the transfer
D. To prevent the controller from locking up due to a large deviation
A. To prevent a sudden valve repositioning upon the transfer
After manually positioning a motor-operated valve, the valve actuator is reengaged by actuation of the…
A. manual declutch lever to the disengage position.
B. manual declutch lever to the engage position.
C. racked in limit switch when the actuator motor breaker is racked
in.
D. valve actuator motor in the open direction
D. valve actuator motor in the open direction
Which one of the following describes the function and use of the backseat on a manual valve?
A. Removes pressure from the packing/stuffing box and is typically
used to isolate the stuffing box for valve repacking.
B. Removes pressure from the packing/stuffing box and is typically
used when needed to isolate packing leakage.
C. Acts as a backup in case the primary seat leaks and is typically
used during system isolation for personnel protection.
D. Acts as a backup in case the primary seat leaks and is typically
used when needed to prevent the primary seat from leaking
excessively.
B. Removes pressure from the packing/stuffing box and is typically
used when needed to isolate packing leakage
