Safety Relief valve sizing

[lockindi]

When sizing a Thermal relief valve to API 520 & 521 (Fire case), what is the value for the 'F' factor, when an insulation material is not classed as having passive fire protection. The vessel is insulated and rated up to 120 Deg C.

Should the factor be 1 for a non insulated vessel or 0.3 based on an insulated vessel.

Thanks
KAL

 

[Fzob]

NFPA 59 section 7 will provide additional guidance on environmental factors. I'm going from memory here, but I'm almost certain that you will need to use 1.0 because in order to use a factor less than 1.0, the insulation must be able to maintain integrity during a fire condition.