One reason I can think of is the specific vendor doesn't allow the option. Look at a different PSV vendor.

Good Luck,
Latexman

By design, springs are already working at a high level of their yield strength, and have not been recommended for use in Pressure-relief Valves where there is direct contact with H2S containing fluid. You can of course use 316SS springs in a bellows valve. Normally in conventional design PRV's, the spring material is changed to Inconel X750 for NACE applications.

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

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

Dear Obturator,
For SS, the specification tells maximum temperature of 60 degrees Celsius,
does it mean that we can not use 316 SS for the NACE application where the environmental temperature is above 60 degrees celsius?
regards,

gguliye What specification are you referring to? Depending on PRV manufacturer, wire size of spring etc., the typical maximum temperature for a 316SS stainless steel spring is 260 C (500 F). 316SS Springs are not recommended for NACE where fluid is in direct contact with the spring.

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

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

well it is in NACE document for the SS it tells max 60 degrees celsius in the relevant table
regards,

WHICH NACE Document? Reference and Revision No.?

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

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

please check image in below link
https://materials-welding.blogspot.com/2015/09/mw2...

You're referencing ISO-15156-3 (2015).

In future, when referring to a 'specification', advise the forum of the full reference and revision/edition number. We can't magically make answers for you as you expect.

This ISO-15156-3 (2015) specification is not specific to Pressure-relief Valves, nor to 316 SS material springs which was your original question (and answered earlier).

The UNS 31603 appearing in the chart is 316L SS. We're not discussing that grade.

I think you're reading too much into NACE and getting misled by the various restrictions stated. I have no idea why you have referenced that section of the 'specification' you refer to.

Observe the standard policy your PRV manufacturer has established for product conforming to NACE. This is normally catalogued alongside the standard materials of construction listings. Refer also to your own 2019 Post where this was advised to you - thread1203-459603: NACE Bolting

PRV components in 316SS (except springs), where specified/accepted* by the end user, need to have a maximum hardness of 22 HRC - all PRV manufacturers know his and offer their PRV's with certain levels of 'MACE' compliance (eg. Level 1 - nozzle and disc insert only in <standard> 316SS as the PRV is mainly closed and those are the only two components in contact with the fluid).

* - NACE/ISO-15156 states that end user has final responsibility of materials according to their interpretation of NACE.

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

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

Obturator,
thank u very much for ur clarification
highly appreciate ur help and support
thx
regards,

Hi,
To add to the previous replies :
https://instrumentationtools.com/safety-relief-val...

Pierre