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Pressure Boundary Part

Pressure Boundary Part

Pressure Boundary Part

Hello All,
which standard defines what is the pressure boundary part for a safety relief valve?
Does the nozzle of the valve belong to the pressure boundary?

RE: Pressure Boundary Part

'Pressure Boundary' is typically a term that may be used by a PRV manufacturer. That is to say, the definition may vary.

This is not quite defined in codes such as ASME XIII, but reference is made to 'pressure zones' and 'primary and secondary' pressures..

Most manufacturers will define 'pressure boundary' the same as they do for 'wetted parts'. In almost all cases, pressure boundary relates to those parts 'wetted' (ie. in contact with) by the process fluid. This is normally broken down into two such boundaries.

i. Primary Pressure parts (ie. parts in contact with the fluid when the valve is closed)- this is normally the nozzle and disc, in the case of a full nozzle spring operated PRV. This can be considered the primary pressure boundary.

ii. Secondary pressure parts or secondary pressure boundary/zone - Parts in contact with the fluid when the valve is open.

This is better explained by individual PRV manufacturers who have adopted this approach for their NACE material PRV offerings - look at their catalogues for their individual definitions of these 'boundaries'.

*** Per ISO-4126, the generic term
'Safety Valve' is used regardless of application or design ***

*** 'Pressure-relief Valve' is the equivalent ASME/API term ***

RE: Pressure Boundary Part

Thanks Obturator

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