PSV Tailpipe Noise Attenuation

[KernOily]

Hi Guys. I also posted this in the Plant Design forum, so please forgive me for cross-posting. I have a PSV that will relieve 160,000 lbm/hr. Service is saturated steam of 70% quality. The PSV is located inside the plant limits. I can't move it outside the plant for a whole host of reasons.

The system design is robust and is fully designed against the need for the PSV. But, as they say, sh*t happens, and that's why the Code requires PSVs in real life. So I have to deal with the possibility of a high noise level during a relief event.

One solution is a silencer. Another soution is to pipe the PSV tailpipe/discharge pipe out of the plant to outside the plot limit and no silencer needed. My calcs show that I need to be 250' away from the plant, as the crow flies, to get the noise level down to the owner-mandated SPL (114 dBA at 3'). This of course assumes no attenuation caused by the long tailpipe. A diffuser will be installed at the end of the tailpipe to break up the velocity of the exit stream.

The question is, how much SPL attenuation will I get due to the 250' run of pipe? I have a hunch that I can get down to the required 114 dBA using less than 250' of pipe.

I searched the forum here but no luck yet. I haven't found anything in any vendor's literature yet either.

Thanks guys!!!! Pete

 

[4Pipes]

IMHO, a silencer at the end of the pipe is a very reasonable option.

http://www.tycoflowcontrol-na.com/ld/CROMC-0298-US.pdf

Putting 250' of pipe on the end of your steam safety valve will open a bag of worms - stress, support, drainage, bending loads on the psv which should be as per the manufaufacturer - the valve body bending load limits not normally totally unreasonable but not large enought to be ignored as most stress engineers tend to do. Process will increase the outlet pipe diameter to something that will quadruple the first problems and then add a margin to it. etc. hiss! boo!