Selection of Pressure Relief Valve

A proper solution would be to give this information to the friendly local valves distributor, open a dialogue, and let that organisation select and offer appropriate valves. After all, the process connection, materials of construction and price still need to be determined as part of the offers, as does the shipping method, delivery time and transport costs. CR4 can't do those.

Do you have access to the API Recommended Practice 520 (part 1) which API-526 references for relief valve orifice calculations? This is the standard you need to follow. If I were tasked with sizing a relief valve, I would definitely trust the standard's recommendations over any calculations given to me by random participants on an internet forum.

If you do follow PWSlack's good advice and seek the help of an engineer at a relief valve distributor, you will need to specify much more data about your application than you have done in your post. The temperature of the water, for example, is really important for relief valve sizing due to the liquid's tendency to flash into vapor when pressure rapidly falls. I suppose you could infer the water's temperature from the specific gravity and viscosity figures you've presented here, but it is very unusual to not present this important parameter up-front. The engineer will also need to know whether or not your application requires capacity certification. Also, you will need to know the proper units of flow measurement for "Q": kPaG is a unit of pressure and not a unit of flow.

Dear Sir,

Thanks for your detailed reply, Unit of Q is L/min..I calculated as per API 520 Part I ( sizing for liquid Releif : Requirng capcity certificatation.. Eq. 3.9)..From this equation I got the right orifice letter... E.. But how we will fix the flange rating.. Is it any relation with the set pressure.?

Thanks and Regards

Vani

Flange rating should be in line with the Vessel/Pipe Nozzle Flange rating.

Regards

Jose

Still no call to the friendly local valves distributor, eh?