ASME Section I Pressure Relief Valves and Devices
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Questions and Answers

What is the function of pressure relief valves?

  • To increase pressure in equipment
  • To block pressure from entering equipment
  • To regulate temperature in equipment
  • To automatically open and relieve pressure (correct)

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

  • 9
  • 5
  • 11 (correct)
  • 15

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

  • To confuse people
  • To make the valves look different
  • To create uniformity in naming (correct)
  • To increase construction costs

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

    <p>ASME PTC-25 definitions</p> Signup and view all the answers

    How are pressure relief valves designed to actuate?

    <p>On inlet static pressure</p> Signup and view all the answers

    What do all pressure relief valves have in common?

    <p>They have great similarity in construction and operation</p> Signup and view all the answers

    What is the acronym PRV used for in this chapter?

    <p>Pressure Relief Valve</p> Signup and view all the answers

    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?

    <p>Two or more</p> Signup and view all the answers

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

    <p>Bronze</p> Signup and view all the answers

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

    <p>Steam will begin to escape</p> Signup and view all the answers

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

    <p>Adjusting nut</p> Signup and view all the answers

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

    <p>The valve spindle can be damaged</p> Signup and view all the answers

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

    <p>To increase the effective area of the disc</p> Signup and view all the answers

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

    <p>Valves with bronze parts</p> Signup and view all the answers

    "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?

    Signup and view all the answers

    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?

    <p>To ensure high temperature resistance</p> Signup and view all the answers

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

    <p>Superheater tubes will overheat due to loss of cooling steam</p> Signup and view all the answers

    What causes the safety valve to pop wide open?

    <p>The increased force against the compression spring</p> Signup and view all the answers

    What is the blowdown of a pressure relief valve?

    <p>The difference between actual popping pressure and actual reseating pressure</p> Signup and view all the answers

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

    <p>Creates a higher pressure under the lip</p> Signup and view all the answers

    How is the PRV set pressure adjusted?

    <p>By changing the compression of the spring</p> Signup and view all the answers

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

    <p>Loosen the jam nut on the adjusting nut</p> Signup and view all the answers

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

    <p>To separately support the valve's discharge</p> Signup and view all the answers

    Study Notes

    Pressure Relief Valves

    • The primary function of pressure relief valves is to prevent overpressure in a system.
    • There are five types of pressure relief devices defined in ASME PTC-25.

    Importance of Accurate Terminology

    • Using accurate terms to describe each type of pressure relief valve is crucial to ensure proper understanding and application.

    ASME BPVC I Definitions

    • According to ASME BPVC I, Part PG-73.1.4, the following definitions apply to pressure relief devices:
      • Accumulation: the pressure increase above the maximum allowable working pressure.
      • Set pressure: the pressure at which a pressure relief valve starts to open.
      • Overpressure: the pressure increase above the maximum allowable working pressure.

    Pressure Relief Valve Design and Operation

    • Pressure relief valves are designed to actuate by opening in response to an increase in pressure.
    • All pressure relief valves have in common the ability to open in response to an increase in pressure.
    • PRV is used as an acronym for Pressure Relief Valve in this chapter.

    Boiler Pressure Relief Valves

    • According to ASME BPVC I, a boiler with more than 500 ft2 of bare tube water-heating surface should have two or more pressure relief valves.
    • Cast iron and bronze safety valves are commonly made of bronze or other corrosion-resistant materials.

    Safety Valve Operation

    • When the steam pressure reaches the set point pressure, the safety valve will lift and relieve the pressure.
    • The point at which the safety valve will lift and relieve the pressure can be adjusted using a spring or other adjusting mechanism.
    • If the safety valve is opened without pressure in the boiler, it will not seat properly, causing problems.

    Huddling Chamber

    • A huddling chamber is formed in a safety valve disc to improve the valve's performance and stability.
    • The huddling chamber allows the valve to open rapidly and fully, ensuring effective pressure relief.

    Superheater and Reheater Pressure Relief Valves

    • According to ASME BPVC Section I, Part PG-73, valves with superheaters operating over 230°C must meet specific requirements.
    • The set pressure of a superheater safety valve must take into consideration the steam pressure drop from the steam drum to the superheater outlet.
    • Superheater and reheater pressure relief valves are required to be made of steel or alloy steel according to ASME BPVC Section I, Part PG-68.
    • If a superheater PRV is set to the same pressure as drum PRVs, it can lead to inadequate pressure relief.

    Blowdown and Adjustment

    • The blowdown of a pressure relief valve is the difference between the set pressure and the reseating pressure.
    • If the blowdown adjusting ring completely blocks off the huddling chamber escape ports, the valve will not seat properly.
    • The PRV set pressure can be adjusted using a spring or other adjusting mechanism.
    • Before adjusting the pressure at which the safety valve opens, the boiler should be shut down and depressurized.

    Discharge Pipe

    • The purpose of a discharge pipe for a safety valve is to direct the released steam or fluid to a safe location.

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    Related Documents

    ASME Section I Pressure Relief Valves and Devices PDF

    Description

    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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