Pressure Safety Valves Calculator - Fire Case Gas Filled Vessel

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Discussion Overview

The discussion revolves around understanding a pressure safety valve (PSV) sizing calculator specifically for gas-filled vessels in fire scenarios. Participants are exploring the relevant standards and calculations necessary for sizing relief valves in such contexts.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant seeks clarification on how a specific PSV sizing calculator functions and its reliability for practical use.
  • Another participant notes that the calculations for the PSV orifice area are typically based on API 520 and advises verification of the calculator before application.
  • A participant describes their specific application involving an anaerobic digester with operating pressures and seeks additional regulations applicable below half bar, expressing uncertainty about existing standards.
  • Another participant suggests that the Pressure Equipment Directive (PED) applies to European installations and recommends following API RP 521 for heat input calculations and API 520 for relief valve sizing, indicating these standards contain necessary equations.

Areas of Agreement / Disagreement

Participants have not reached a consensus on the applicability of standards for low-pressure scenarios, and there are multiple viewpoints regarding the appropriate regulations and calculations for sizing relief valves.

Contextual Notes

Participants express uncertainty regarding the adequacy of existing standards for pressures below half bar and the need for additional regulations or calculations specific to their applications.

Who May Find This Useful

Individuals involved in the design, installation, or regulation of pressure safety systems, particularly in European contexts or low-pressure applications.

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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.
 
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 I've 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?

ZEN
 
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.
 
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