PSV Sizing

[arcpro]

Can somebody please guide me through PSV sizing?

[sharjeel]

following things to know before you go for PSV sizing
1)Basis for PSV sizing, i.e., external fire, tube rupture case, discharge valve closure, exothermic reaction run away. This is important to know prior you go through PSV sizing. Then there are standards available which guide you in determining maximum over-pressurization above vessel design pressure.
2)Once you know the basis of PSV sizing, you can then establish Flow capacity required to prevent over pressurization.
3)Establish static and dynamic back pressure in the discharge piping of the PSV. Static pressure means pressure that is constantly present in the discharge piping, while dynamic pressure is the result of flow through PSV. static pressure affects PSV popping pressure whereas dynamic pressure affects PSV releasing capacity.
4)Establish re-seating pressure (blow down pressure) of the PSV, the pressure at which PSV will re-seat after releasing pressure. this is usually below popping pressure.
Once you establish above four things, PSV sizing is then mere orifice sizing.
The type selection of PSV (pilot operated, constant back pressure, bellow type PSV etc) & amount of PSV is the next consideration.

[dexter]

Thats a very critical part of design. My friend I would suggest you to go thru API-RP-520 and API-RP-521 for sizing, selection and installation of such pressure relief and protection devices. I can guide you thru if you can share some process data.

[whaider]

For me, establishing the correct basis is the key and should be very well thought through. This is an area where you know better than any one else. You will identify a worst case scenario along with a weakest point in your process. I will spend 85% of time in establishing the basis and 15% on the sizing it self including review of proposals.

Once you are sure that your basis is correct and you have got the relieving pressure & flow, any manufacturer of relief valves shall do the sizing for you while submitting his offer. It is more of a selection than hardcore sizing. This fact does not relive any process engineer from understanding how PSVs are sized and math involved. This understanding shall also help you in reviewing the proposals which is an important part of procurement process. For developing this understanding, in addition to API 520/521/526 I would suggest,

1- http://www.tycoflowcontrol-na.com/ld/CROMC-0296-US.pdf [PRV Engineering Handbook for download]

2- http://www.andersongreenwood.com/literature.asp[For all sorts of literature on the subject]

3- http://sizing.tycovalves.com/Software/P ... rview.aspx [For Software download]

4- ASME PTC-25 [Testing]

[arcpro]

Thanks everybody for your replies.
Is there any FREE software available for PSV sizing?

[whaider]

You can have all you need on the following link

http://www.dresserconsolidated.com/inde ... selection/

[arcpro]

Thanks.

[whaider]

A good presentation on basics of PSVs ...