PSV in Pressure Vessel 3

[bmoorthy]

What are the circumstance under which the PSV should be mounted on the Pressure vessel. In most of the pressure vessel we find a nozzle provided for Safety valve and also we find the PSV are very close to the vessel or are directly mounted on the vessel.

Where as in a Heat Exchanger (Which is designed to ASME Sec VIII div 1) we generally do not find PSV nozzles, what are the rules which specifies the situations and the locations of PSV provisions?

 

[prochem]

Relief valves requirements for pressure vessels are addressed in ASME Section VIII, Div 1, UG-125 thru UG-136.

 

[sbush]

I too am interested in the questions raised by bmoorthy. Unlike prochem, I don't have easy access to a set of code books. Could someone please elaborate on prochem's answer. Specifically, I would like to know:

1. For cold water service, does the PRV or PSV have to be installed at a high point on the vessel?

2. Does the PRV or PSV have to be installed on a dedicated vessel penetration or can it be combined with another device, such as an air release valve, using an adequately sized tee fitting or manifold?

3. In the water treatment market, I see an equal amount of pressure vessels, designed for cold water service, with and without PRVs or PSVs. What dictates when they must be used?

S. Bush

http://www.water-eg.com

 

[prochem]

Friends,

A)UG-125, the wording implies that a pressure relief device does not need to be located directly on the vessel PROVIDED the source of the pressure in the vessel is external to the vessel can be controlled and is below the MAWP of the vessel at operating temperature.

B)For Heat exchanger, PSV can be avoided only if the sorce has its own safety relief vale and if it matches the pressure on the exchanger(MAWP). There should not be any valve between HX and the source

c)For vapor application, Pressure relief devices should be connected to the vessel in the vapor space above any
contained liquid or to piping connected to the vapor
space in the vessel which is to be protected.( Consider your individual scenario)

D)Pressure relief devices for liquid service application
shall be connected below the normal liquid level.(doesnt apply if PSV is designed for fire case scenario)

E)All Pressure vessels shall be protected by a pressure releiving device that shall prevent the pressure from rising 10% or 3 psi above the MAWP(Whichever is greater).For fire case scenario the PSV shold prevent the pressure from rising more than 21% of MAWP.

Hope this help.

 

[deanc]

ASME SecVIII Div 1 Appendix M