5 replies to this topic

[barnesed]

A survey of an existing steam relief valve installation shows the 4" valve outlet connected to a 4" discharge line that connected to an 8" vent header to the roof. (There are other lines tied into the 8" vent header.) There is a 4" check valve in the 4" relief discharge line where it connects to the 8" vent header. Aside from the backpressure questions, is a check valve in a relief discharge line allowed? I would have thought that there could be a situation where the check valve fails to open.

[Erwin APRIANDI]

Hi barnesed,

Here is some rules to be considered while designing relief valve outlet line
1.Discharge line diameter must be at least equal to PRV outlet flange size
2.Maximum discharge velocity should not exceed 75% of sonic velocity
3.For flammable releases to atmosphere, minimum velocity should be no less than 100 ft/sec
4.Atmospheric risers should discharge at least 10 ft above platforms within 50 ft horizontally
5.Radiant heat due to ignition of release should be considered
6.No check valves, orifice plates or other restrictions permitted
7.Atmospheric discharge risers should have drain hole
8.CSO valves should have the stem oriented horizontally or vertically
9.Piping design must consider thermal expansion due to hot/cold release
10.Autorefrigeration and need for brittle fracture resistant materials
11.Closed discharge piping should slope continuously downward to header to avoid liquid traps

you can also download the article that I attached in the following thread
http://www.cheresour...-closed-outlet/

[Art Montemayor]

If your company or organization, your insurance company, or your local safety regulations don’t forbid the installation of a check valve in the discharge line of a PSV, then I would.

This subject has been discussed a few times in some of the many HAZOPs I have participated in and we always discarded the idea or proposal as un-needed, useless, and simply another potential hazard which we didn’t need. I would prohibit it.

[fallah]

In general,installation of check valve in PSV discharge line is prohibitted.

But you fail to submit the information about the vessel PSV installed on.Which standard governs the vessel/boiler/.... design? ASME Sec. IV or ASME Sec. I or........?

Please submit a sketch shows the PSV discharge line and relevant header configuration for better assistance.

[Balav]

If your company or organization, your insurance company, or your local safety regulations don't forbid the installation of a check valve in the discharge line of a PSV, then I would.

This subject has been discussed a few times in some of the many HAZOPs I have participated in and we always discarded the idea or proposal as un-needed, useless, and simply another potential hazard which we didn't need. I would prohibit it.

Hi,

Please explain the section 2.11 in Shell DEP 80.45.10.11 version 30. This section says about role of class 1 Check valve is it applicable for providing check valve at the relief outlet??

[fallah]

Hi,

Please explain the section 2.11 in Shell DEP 80.45.10.11 version 30. This section says about role of class 1 Check valve is it applicable for providing check valve at the relief outlet??

Balav,

Please quote the mentioned statement from Shell DEP.

Fallah

Edited by fallah, 16 November 2011 - 04:23 AM.