3 replies to this topic

[Tamizh]

Hi all,

 

API 521 15.14.4.1 says that PRV may not required if the piping always contains a pocket of non condensing vapour, such that it can never become liquid-full.

 

what does this mean? I cant get this meaning. 

 

Thanks

 

[aroon]

Gany,

 

It means if your system is having adequate vapor space in the form of pockets of non-condensing vapors (gases), that space itself is sufficient to accommodate increase in liquid volume (minimal compared to gas) due to thermal input. Increase in liquid volume by thermal expansion is very small as compare to available volume in the form of vapor pockets so the increase liquid volume will lead to gas compression instead of increasing whole system pressure.

 

Hope this is sufficient to understand the basic of this phenomena ...

[fallah]

Gany,

 

In addition to aroon's explanations:

 

The API statement clearly states "...it may not required..." means if non condensing vapors isn't adequate in volume or is so less to oversaturate the basic liquid permanently (not always) then a PRV is required to protect piping against overpressure due to thermal expansion...

[Tamizh]

thanks aroon & fallah