Valves

Question 0

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?

Answer 0

170 psig

Question 1

Which one of the following describes the function of a safety valve?

Answer 1

Provide overpressure protection to limit the internal pressure in vessels

Question 2

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?

Answer 2

141 psig

Question 3

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?

Answer 3

127 psig

Question 4

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?

Answer 4

764 psig

Question 5

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?

Answer 5

5.0

Blowdown% = P(set)-P(reset)
/ P(set) *100%

Question 6

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.

Answer 6

above; safety

Question 7

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?

Answer 7

3.5 percent

Accumulation % = P(fullopen)-P(setpoint)
/ P(setpoint) *100%

Question 8

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.

Answer 8

partially; 6 gpm

Question 9

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?

Answer 9

Relief Valve Status: Safety Valve Status:
Partially Open. Cycling between full open &
Full open

Question 10

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.

Answer 10

fully; 2 gpm

Question 11

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?

Answer 11

The relief valves are installed to prevent unnecessary opening of the safety valves during a steam pressure transient.

Question 12

The primary purpose of a pressure relief valve is to…

Answer 12

maintain system integrity.

Question 13

The difference between the setpoint pressure at which a safety valve opens and the pressure at which it closes is called..

Answer 13

blowdown.

Question 14

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…

Answer 14

accumulation.

Question 15

Which one of the following is a difference between a typical relief valve and a typical safety valve?

Answer 15

A relief valve gradually opens as pressure increases above the setpoint pressure whereas a safety valve pops open at the setpoint pressure.

Question 16

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 __________.

Answer 16

stabilize slightly above the pressure setpoint; fluctuate within a few percent of the pressure setpoint

Question 17

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 __________.

Answer 17

fluctuate within a few percent of the pressure setpoint; stabilize slightly above the pressure setpoint

Question 18

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?

Answer 18

Relief Valve A. Relief Valve B

4 gpm 2 gpm

Question 19

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?

Answer 19

205 psig

Question 20

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.

Answer 20

lower; poorer

Question 21

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.

Answer 21

smaller; larger

Question 22

Which one of the following statements describes the flow rate characteristics of a typical gate valve in an operating water system?

Answer 22

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

Question 23

Which one of the following statements describes the flow rate characteristics of a typical globe valve in an operating water system?

Answer 23

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

Question 24

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.

Answer 24

closed; large

Question 25

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.

Answer 25

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

Question 26

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

Answer 26

Ball

Question 27

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

Answer 27

Gate; Gate

Question 28

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.

Answer 28

Cannot be determined without additional information.

Question 29

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.

Answer 29

Another valve, located downstream of the throttled valve, was partially closed.

Question 30

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.

Answer 30

The throttled valve was closed more.

Question 31

How will a typical motor-operated valve respond to a loss of electrical power to the valve actuator?

Answer 31

Remain as is

Question 32

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.

Answer 32

The valve disk has jammed against its backseat by the difference in the thermal contraction of the stem and the bonnet.

Question 33

When manually positioning a motor-operated valve, why must care be taken to avoid using excessive valve seating/backseating force?

Answer 33

The valve may bind during subsequent operation.

Question 34

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.

Answer 34

The maintenance technician overtightened the packing gland, causing the stem to bind.

Question 35

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.

Answer 35

Increased stroke time from fully open to fully closed.

Question 36

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.

Answer 36

Removes pressure from the packing/stuffing box and is typically used when needed to isolate packing leakage.

Question 37

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.

Answer 37

A. The valve may bind and cause the motor to trip on overload during subsequent remote operation.

Question 38

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.

Answer 38

D. energizing the valve actuator motor.

Question 39

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

Answer 39

C. disengages; engages

Question 40

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.

Answer 40

A. The handwheel will disengage and the valve will automatically open.

Question 41

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.

Answer 41

A. The handwheel will disengage and the valve will automatically close.

Question 42

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

Answer 42

B. The handwheel will turn, but the valve stem will not move.

Question 43

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

Answer 43

B. Gate

Question 44

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

Answer 44

B. can be used to prevent flow in both directions.

Question 45

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

Answer 45

D. Check valve

Question 46

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

Answer 46

C. swing and lift.

Question 47

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.

Answer 47

A. permit flow in only one direction.

Question 48

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.

Answer 48

B. backflow through nonoperating components or flowpaths.

Question 49

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

Answer 49

D. Check valve

Question 50

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.

Answer 50

B. close direction using normal force and verify there is no substantial handwheel movement.

Question 51

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.

Answer 51

C. in the closed direction, then open the valve to its previously open position.

Question 52

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

Answer 52

B. larger; more

Question 53

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.

Answer 53

C. the turbulent flow created by a partially opened gate valve will cause erosion damage to the valve seat.

Question 54

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

Answer 54

B. larger; smaller

Question 55

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.

Answer 55

C. Attempt to turn the valve handwheel in the close direction and verify no movement.

Question 56

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

Answer 56

D. smaller; on/off

Question 57

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.

Answer 57

C. close direction using normal force and verify there is no substantial handwheel movement.

Question 58

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.

Answer 58

C. The turbulent flow created by a throttled gate valve will cause erosion damage to the valve seat.

Question 59

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.

Answer 59

D. The maintenance technician overtightened the packing gland, causing the stem to bind.

Question 60

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.

Answer 60

D. Attempt to turn the valve operator in the open direction and verify that no movement occurs.

Question 61

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.

Answer 61

C. The turbulent flow created by a partially opened gate valve causes excessive seat and disk wear.

Question 62

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.

Answer 62

D. require less force to open against large differential pressures.

Question 63

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.

Answer 63

D. require more force to open against large differential pressures.

Question 64

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

Answer 64

A. ball; ball

Question 65

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.

Answer 65

A. the turbulent flow created by a partially opened gate valve can cause extensive damage to the valve.

Question 66

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

Answer 66

C. butterfly; butterfly

Question 67

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.

Answer 67

D. The valve stem packing gland was overtightened after the packing material was replaced.

Question 68

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

Answer 68

A. ball; butterfly

Question 69

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

Answer 69

D. butterfly; ball

Question 70

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.

Answer 70

B. As system pressure increases to the safety setpoint, the pressure overcomes spring force on the valve operator, causing the valve to open

Question 71

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

Answer 71

A. Safety

Question 72

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.

Answer 72

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.

Question 73

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

Answer 73

A. A; A

Question 74

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

Answer 74

B. A; B

Question 75

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

Answer 75

A. increase; decrease

Question 76

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

Answer 76

B. increase; increase

Question 77

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.

Answer 77

D. decrease, and the pressure on the downstream side will remain the same.

Question 78

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

Answer 78

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

Question 79

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

Answer 79

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

Question 80

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

Answer 80

B. Globe valve

Question 81

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

Answer 81

A. flow control is more linear for globe valves than for gate valves.

Question 82

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.

Answer 82

C. isolate fluid flow in an operating system.

Question 83

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.

Answer 83

D. Attempt to turn the valve operator in the "open" direction and verify that no movement occurs

Question 84

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

Answer 84

D. Increased stroke time from fully open to fully closed

Question 85

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

Answer 85

A. equal to

Question 86

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

Answer 86

A. To prevent a sudden valve repositioning upon the transfer

Question 87

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

Answer 87

D. valve actuator motor in the open direction

Question 88

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.

Answer 88

B. Removes pressure from the packing/stuffing box and is typically used when needed to isolate packing leakage