4 replies to this topic

[rohollah]

hi

I am going to redesing a control valve for acetic acide service which is located in below condition.

can anyone tell me the correct calculeted "Cv"?

flow rate:270m3/h

inlet pressure:28 bara

outlet pressure:5.94bara

inlet temperature:185c

specific gravity:0.9035

vapour pressure:28bara


best regards
rohollah

[DB Shah]

Dear rohollah
Yours is a flashing service, refer this page for step by step sizing guide

http://blackmonk.co....-control-valve/

[kkala]

Probably vapor pressure needs further check, being about 5.4 bar a for pure acetic acid at 185 oC, http://en.wikipedia...28data_page%29 .
"Manual" calculation is tried in attached "CV.xls", following Masoneillan. Method seems similar to the proposed by DB Shah (with small differences). Comments on the attachment would be welcomed, as well a result by an instrument software for comparison.
Assuming critical pressure = 57.8 bar a (that of acetic acid), calculated Cv at conditions is
Cv=129 gpm/sqrt(psi) for vapor pressure = 28 bar a (this does not seem to be for acetic acid).
Cv=68 gpm/sqrt(psi) for vapor pressure = 4.5 bar a.
Last result is practically same as the one by brondy in post No 2.

Attached Files

•  CV.xls   23.5KB   56 downloads

[ankur2061]

rohollah,

An excel spreadsheet for control valve sizing based on Masoneilan method can be downloaded from the following link:

http://www.google.co...FrCjAPw&cad=rja

Regards,
Ankur.

[breizh]

Hi ,

Here an other good one with good support:

http://tierling.home.../LiqCvShell.htm

Breizh