Relation between gas velocity and sound level through tail pipe 1

[kingsss]

I'm looking for a formula/correlation which describes the relation between the diameter of a tail pipe (or velocity of gas leaving the tail pipe) and the production of sound.

Considering a Pressure Relief Valve system, I need this relation in order to caclulate the minimum internal diameter of the tail pipe to keep the sound level under the allowed level.

I've already consulted the API521 4th edition March 1997. In this practice several ways lead to a sound level. But none of them are related to a diameter or gas velocity.

Anyone who can help me out?

regards, Kingsss

 

[jalvarez]

kingsss
This is an interesting issue.
In my opinion, if you have a noisy safety valve, you will not reduce significantly the noise just using an expansion, and this could be the reason you don’t find an adequate correlation. The noise is generated by the contraction and expansion of the PSV, and is propagated along the tail pipe. If you reduce the velocity of the exhaust gas, you don’t significantly reduce the noise level.
You may have a case where you have a high velocity of the gas exiting a tail pipe, a “free jet discharge noise”, without an upstream valve very close to the exit. If this is the case, you may reduce the noise with a higher exit diameter. It seems to me that this is not the case, as you mentioned the PSV. So, I think you need a silencer.
There are companies specialized in these silencers. Personally, I’ve good results with ATCO Noise Management. There are many others.
Have a safe day
J.Alvarez

 

[hacksaw]

there are no single formula to answer your question. you generally have to use a silencer and properly designed piping to meet your noise criteria without imparing safety.

 

[kingsss]

All right, thanks all!!