7 replies to this topic

[process16]

valve problem
I have a process problem at a valve installed at the outlet of a heat exchanger, the CV of this valve =42
the valve is dimensioned for a pressure upstream = 15bar
my problem is , we have a  variation of the pressure upstream (change pompme) the pressure in the present case is 7 bar
how to check if the valve can operate without problems
(The fluid is a hot oil)

[Zauberberg]

If you know upstream/downstream pressure, fluid properties, and valve Cv, it is quite easy to estimate the new flow conditions. Check any valve sizing reference available online, such as http://www.documenta...1798x012_11.pdf  or http://www.pro-quip....ction/SS_03.pdf

 

Here is an online calculator: http://www.engineeri...ents-d_277.html

 

ISA-75.01.01-2007 is attached for reference.

Attached Files

•  ISA 750101.pdf   295.16KB   58 downloads

Edited by Zauberberg, 30 May 2015 - 11:59 AM.

[process16]

Zauberberg

thank you, interesting!!!

but what i didnt understund is:

  the CV given in the data sheet , is it a  tsandard value used  to be controlled by  the new calculated CV??

[Zauberberg]

Cv of a given valve is constant number. It is independent of upstream and downstream conditions, and of fluid properties.

[process16]

well what about this relation :

Q=Cv sqrt(dp/G)

here Cv is depends on the flow rate and the pressur

so how its independent oof upstream conditions??

[Zauberberg]

Please read the definition of the valve Cv in the references I posted. We are wasting time here.

[process16]

Please read the definition of the valve Cv in the references I posted. We are wasting time here.

ahhahaha ok , sorry i understood it

thank you again

by the way , i didnt wast the time and sorry if i did that to u

thank you again  again!!

[Zauberberg]

It is a waste of time in every case when people want somebody else to digest all the information and present them the final result (or explanation) in 2-3 sentences, so that they themselves do not need to make any effort beyond that point. What they do not realize, however, is that it is impossible to become a good engineer if they expect to be spoon-fed for every problem or subject they encounter.

 

You came up with additional question only 2 hours and 45 minutes after I posted a plentiful of data in my first post. I seriously doubt you have taken the time to read all links and attachments within this period. You wouldn't ask again about the valve Cv if you have read those links and attachments, because the answer is already there.