ASME Section I Pressure Relief Valves and Devices

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23 Questions

What is the function of pressure relief valves?

To automatically open and relieve pressure

How many different types of pressure relief devices are defined in ASME PTC-25?


Why is it important to use accurate terms to describe each type of pressure relief valve?

To create uniformity in naming

According to ASME BPVC I, Part PG-73.1.4, which definitions relating to pressure relief devices apply?

ASME PTC-25 definitions

How are pressure relief valves designed to actuate?

On inlet static pressure

What do all pressure relief valves have in common?

They have great similarity in construction and operation

What is the acronym PRV used for in this chapter?

Pressure Relief Valve

According to ASME BPVC I, how many pressure relief valves should a boiler have if it has more than 500 ft2 of bare tube water-heating surface?

Two or more

What material are cast iron and bronze safety valves commonly made of?


How does a safety valve work when the steam pressure reaches the set point pressure?

Steam will begin to escape

What is used to adjust the point at which the safety valve will lift and relieve the pressure?

Adjusting nut

What happens if the safety valve is opened without pressure in the boiler?

The valve spindle can be damaged

Why is a huddling chamber formed in a safety valve disc?

To increase the effective area of the disc

What does ASME BPVC Section I, Part PG-73 prohibit for valves with superheaters operating over 230°C?

Valves with bronze parts

"The set pressure of a superheater safety valve must take into consideration that the steam pressure will drop as it flows from the steam drum to the superheater outlet." - What is the reason behind this statement?

Why are superheater and reheater pressure relief valves required to be made of steel or alloy steel according to ASME BPVC Section I, Part PG-68?

To ensure high temperature resistance

What happens if a superheater PRV is set to the same pressure as drum PRVs?

Superheater tubes will overheat due to loss of cooling steam

What causes the safety valve to pop wide open?

The increased force against the compression spring

What is the blowdown of a pressure relief valve?

The difference between actual popping pressure and actual reseating pressure

What happens when the blowdown adjusting ring completely blocks off the huddling chamber escape ports?

Creates a higher pressure under the lip

How is the PRV set pressure adjusted?

By changing the compression of the spring

What should be done before adjusting the pressure at which the safety valve opens?

Loosen the jam nut on the adjusting nut

What is the purpose of a discharge pipe for a safety valve?

To separately support the valve's discharge

Explore the code requirements, construction, and operation of ASME Section I Pressure Relief Valves and Devices. Learn about the different types defined in ASME PTC-25 Pressure Relief Devices and the terminology used to categorize them.

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