Valves BOT

A main steam system uses a combination of safety valves 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 safety valves are installed to prevent chattering of the relief valves during normal power

  operation.

• The safety valves are installed to prevent unnecessary opening of the relief valves during a steam

  pressure transient.

• The relief valves are installed to prevent chattering of the safety valves during normal power

  operation.

• The relief valves are installed to prevent unnecessary opening of the safety valves during a steam

  pressure transient.

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

• Provide overpressure protection to limit the internal pressure in vessels.

• Control pressure in a system to maintain optimum operational conditions.

• Sound a warning by lifting at a predetermined value slightly higher than operating pressure.

• Modulate open as necessary to maintain system pressure and/or temperature within normal limits.

The primary purpose of a pressure relief valve is to...

• reduce system energy.

• reduce system pressure.

• maintain system integrity.

• maintain system mass.

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

• blowdown

• accumulation

• setpoint tolerance

• setpoint deviation

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...

• setpoint deviation

• setpoint tolerance

• accumulation

• blowdown

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

• The actuator closing spring on a relief valve is in a compressed state whereas the actuator closing

  spring on a safety valve acts in tension.

• A relief valve gradually opens as pressure increases above the setpoint pressure whereas a safety

  valve pops open at the setpoint pressure.

• Relief valves are capable of being gagged whereas safety valves are not.

• The blowdown of a relief valve is greater than the blowdown of a safety valve.

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.

• higher; better

• lower; better

• higher; poorer

• lower; poorer

Consider a 3-inch gate valve and a 3-inch globe valve in separate but identical operating water

systems. If both valves are fully open, the gate valve will produce the __________ head loss and the

__________ flow rate.

• smaller; larger

• larger; smaller

• smaller; smaller

• larger; larger

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

• Open fully

• Close fully

• Remain as is

• Move to 50 percent open

Which one of the following describes the function and use of the backseat on a manual valve?

• Removes pressure from the packing/stuffing box and is typically used to isolate the stuffing box

  for valve repacking.

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

  packing leakage.

• Acts as a backup in case the primary seat leaks and is typically used during system isolation for

  personnel protection.

• Acts as a backup in case the primary seat leaks and is typically used when needed to prevent the

  primary seat from leaking excessively.