5 replies to this topic

[ist10]

Dear all,

 

we are about to define process specifications for a silencer on a vent line. The system pressure is as high as 35 barg and the vent line is open to atmosphere. For a given pipe size with adiabatic compressible flow, we are reaching Mach Number = 1.0 without losing half the pressure of 35 barg as the friction loss on vent line. I am aware that it is not possible to go beyond  Mach=1.0. There will be some allowable pressure drop for the silencer itself but I don't foresee this wll be great. Therefore the excess pressure will be lost at the pipe exit due to sudden expansion but I assume that this is not something allowable. Can somebody shed some light on that? 

 

Many thanks

Kind regards

[fallah]

ist10,

 

Is the vent line a PSV discharge line? Can you upload a simple sketch of the vent system?

[ist10]

Fallah,

 

not a PSV discharge line. The main line is gas supply line to gas turbine and the vent is intended to discharge the volume within two valves in case both closed. 

[fallah]

ist10,

 

Yes, the excess pressure will be lost at the pipe exit due to sudden expansion along with the shock waves and noise; and the silencer is located there (pipe exit) to silence the noise to an acceptable level permitted by local regulations...

[ist10]

Fallah,

 

many thanks for the response. I can imagine the noise limitation will be solved via silencer; however do you think that this shock wave created by the sudden expansion is allowed in terms of say pipe supports and so on? 

[fallah]

ist10,

 

The created shock waves and vibration should be damped by proper pipe supporting system...