Jun 25, 2003 · cswosu, Designing PSV outlet with Mach 1 is possible however there are associated conditions such as mechanical integrity of the tail pipe, structure integrity of pipe support, capacity bottleneck of the PSV due to mach 1 (secondary choke), noise problem, potential PSV chattering due to high backpressure, etc.

Aug 27, 2019 · Hi Latexman, The fluid velocity is already at Mach 1 at the PSV outlet and will not reduce any further. With the outlet piping being minimal the pressure at the inside of tail pipe outlet would be nearly same as that exit of PSV nozzle which is critical pressure, I used critical pressure for the "P" or static pressure term in the API 520 formula.

Jul 28, 2006 · There are several orifice sizes which can be installed in a 4x6 PSV. For example a 4L6, 4M6, 4N6 or 4P6. Each on larger than the previous, but none having the same area as a 4" Pipe ID. Sch 40 Pipe has an ID of 4" and a area of 12.5 sq in. L orifice area 3.2 sq in., M orifice 4 sq in, N orifice 4.9 sq in & a P orifice 7.2 sq in.

Jun 27, 2007 · The PSV is located close to the compressor in the plant room but it is necessary to pipe the discharge of the PSV to outside the room to reduce noise in the plant room. The PSV will be an L orifice valve with a DN80 inlet and DN100 outlet.

Jun 28, 2005 · 1" pipe has an inside area of 0.7190 in2 1.5" pipe has an inside area of 1.767 in2 2" pipe has an inside area of 2.952 in2 Given that inside area of the 1" pipe is larger than the orifice size of the PSV, why can't I reduce down on the outlet of the PSV from a 2" outlet to the existing 1" pipe?

Jan 20, 2015 · The line sizing is based on the pipe cross section area. As the pipe section area reduced due to the wall thickness increased from sch.40 to sch.160, the next larger pipe size may be required to accommodate the PSV discharge flow.

Mar 15, 2025 · If so, drill a weep hole at the low point of the PSV tail pipe. At some added minimal risk, if you dont have N2 to purge, and there are no other vessels in the exit path of the PSV, choose a 300lb rated PSV and 300lb piping to withstand detonation in case of accidental ignition.

Oct 2, 2002 · The PSV nozzle is choked, but the velocity everywhere in the pipe is small and far below sonic. (b) If you increase the PSV size, the flow through the 2 inch pipe will increase untill it chokes at the pipe outlet also. (c) Increasing the PSV size further, still increases the flow and the pressure before the outlet choke point increases.

Feb 6, 2017 · Then, you cannot use 0.75" Sch. 160 pipe upstream of that 0.75" Sch. 80 PSV inlet pipe and downstream of the pressure vessel. You could use 0.75" Sch. 40 or 1" Sch. 160 though. As vladrath mentioned, the 3% rule also goes into determining the pipe ID you can use. Both criteria must be satisfied to comply. Good luck, Latexman

Dec 22, 2006 · Someone calculated that a surface area of the cone/basket of >>twice that of the discharge pipe opening would be sufficient to ensure no effective obstruction to discharge relief path. We would often find nests and dead birds inside the discharge pipe - but nothing ever big enough to obstruct a real SV lift. Cheers - - - - - - - - - - - - - - -