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Pressure safety Valves

  1. Oct 6, 2011 #1
  2. jcsd
  3. Oct 6, 2011 #2
    This worksheet determines the required pressure relief valve orifice area for a gas filled pressure vessel that is on fire.

    These calculations are usually based on API 520. I would verify the calculator before you use it for any real relief valve sizing.
  4. Oct 7, 2011 #3
    Thanks for your reply

    Im looking at an anaerobic digester with an operating pressure of between 20 and 30mbar. Usually relief valves will be set to release at around 35mbar.

    Standards ive found are

    ISO 4126 (harmonized with European Union directives) [5]
    EN 764-7 (former CEN standard, harmonized with European Union directives, replaced with EN ISO 4126-1)
    AD Merkblatt (German)
    PED 97/23/EC (Pressure Equipment Directive - European Union)

    Most only cover above half bar do you or does anyone know if there are any other regs to consider?

    If not is there a simple calculation for sizing relief valves?

  5. Oct 7, 2011 #4
    From your standards it looks like this is a European installation.

    Assuming this, the PED will apply. You will need to get your relief valve CE Marked and the CE Declaration of Conformity should list the highest applicable PED category.

    I would suggest following API RP 521 to determine the heat input from fire and API 520 to calculate the relief valve size. You should be able to download or order these standards - they will have all the equations.
    Last edited: Oct 7, 2011
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