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josej
Power-User

Join Date: Mar 2008
Location: Mumbai
Posts: 250
Good Answers: 2

Control Valve, Cavitation

04/15/2015 2:37 AM

Dear All,

1)If Cavitation index

Sigma Value ( Process ) < Sigma Value ( Manufactuers Recomended Value )

Can We conclude that valve will not cavitate

2 ) Due to High DP, we expect Cavitation to Occur at minimum flow, multistage let down trim has been selected with Stellite overlay.

How can we judge that cavitation at minimum flow is ok ?

Regards

Jose
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PWSlack
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 32175
Good Answers: 839
#1

Re: Control Valve , Cavitation

04/15/2015 3:40 AM

The judgement can be made by discussing the situation with the valve manufacturer over the telephone AND it will be by far the quickest way too.

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Rixter
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Join Date: Apr 2010
Location: About 4000 miles from the center of the earth (+/-100 mi)
Posts: 9910
Good Answers: 1141
#2

Re: Control Valve, Cavitation

04/15/2015 12:53 PM

This explains Sigma as it applies to cavitation. I hope that helps...

https://www.fwwebb.com/docs/processcontrols/ControlValveCavitation.pdf
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kwn
Participant

Join Date: Mar 2015
Posts: 3
#3

Re: Control Valve, Cavitation

04/16/2015 11:03 AM

Not really enough info ...

For Starters: (Assuming the medium is liquid)

1. What type of valve?

2. What's your calculated sigma value?

-What's the upstream pressure? How far upstream of the valve was it measured?

- What's the downstream pressure? How far downstream from the valve was it measured?

3. Any detail on the system (flow and pressure ranges)?

A multistage trim will reduce pressure drop at the vena contracta, which will then tolerate a lower cavitation index, but without knowing more details of your situation a conclusion can't really be made yet.

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