Certified Pressure Relief valves

[SrChemE]

Are relief valves and rupture disks required to be certified / stamped when in hazardous processes?
What can be done to have them certified?

 

[The Obturator]

It depends what you mean by certified. Generally, in the USA, SRV's follow the ASME VIII Code for unfired vessels, ASME I for fired boilers etc. Each has similar, but different rules. For pressures above 15 PSIG, the SRV's need to have their capacities certified against these code rules by the National Board of Pressure and Vessel Inspectors. The valves are then able to be code stamped so long as the manufacturer has his factory system qualified as well. Contrary to some peoples belief, SRV's are not ASME Approved but accredited by the National Board. Similar exists for bursting discs.

It does not matter whether the process is hazardous or not. It is whether the pressure is over 15 PSIG. Liquids have also been included since 1985.

In Europe (EU Countries) a similar PED - Pressure Equipment Directive is enforced since 1992 for pressures above 0.5 barg. In the main, here one of the Nominated Bodies (Lloyds, DNV etc.), certifies the valve against test data which can also that supplied by the National Board. The valves in these cases are CE marked.

Per ISO, only the term Safety Valve is used regardless of application or design.

 

[SrChemE]

avalveman, thank you for your reply. we have several tanks above 15 psig, so it would apply to all of them.
When you say "capacities certified against these code rules by the National Board of Pressure and Vessel Inspectors" do you meen the relief calculation that we engineers do on each valve to ensure they were sized correctly (based on fire,PCV failure, outlet valve closed, inlet/outlet dP check, etc.)?

 

[The Obturator]

Basically yes. Normally, you would calculate SRV size using API-520 to determine effective area. Once vendor is selected, calculate the actual capacity of fluid using ASME VIII formula with SRV's actual orifice area and actual derated coefficient of discharge listed in the National Board "Red Book" NB-18. Of course the manufacturer can do this for you. Note that the nameplate will have the equivalent air, water or steam rated capacity stamped for compliance with ASME code (different to actual fluid and reflects actual medium originally used for accreditation).

Per ISO, only the term Safety Valve is used regardless of application or design.

 

[SrChemE]

Avalveman, thanks for your feedback.
How do I ensure the valve is actually certified?
Will the relief valve tag identify certified/non certified? Or is there another designation for that?
Thanks!

 

[The Obturator]

Be sure the valve has "UV" Stamped under the ASME form of Shield Symbol on the SRV nameplate. Or simply see if the design/manufacturer is listed in the National Board Book NB-18 here;

http://www.nationalboard.org/SiteDocuments/NB18/NB18.pdf

Per ISO, only the term Safety Valve is used regardless of application or design.