9 replies to this topic

[aika93]

Hello, Dear community members!

 

I am new in this industry and reading your forum help me a lot.

 

I am doing PCV calculation( for the first time) for nitrogen supply and  need to calculate valve Cv, for this I am using Fisher Catalog 12 Section 2 tab. In one of the formulas they use x-Ratio of pressure drop to upstream absolute static pressure (dP/P1), dimensionless. 

 

My question is, what they mean by saying "upstream absolute static pressure"?

 

Regards,

Aidan

Edited by aidan93, 18 October 2016 - 02:42 AM.

[breizh]

Hi ,

Take a look.

Edited by breizh, 18 October 2016 - 10:17 PM.

[aika93]

Hi ,

Take a

Thank you!

[fallah]

 

My question is, what they mean by saying "upstream absolute static pressure"?

 

 

Aidan,

 

It's the pressure, say in psig, which a pressure gauge at control valve upstream shows plus the local atmospheric pressure (at sea level 14.7 psi).

 

Then, for example, if the pressure gauge shows 100 psig and the local atmospheric pressure to be 14.7 psi; the "upstream absolute static pressure" for relevant control valve will be 100+14.7=114.7 psia

[shvet]

 

I am doing PCV calculation( for the first time) for nitrogen supply and  need to calculate valve Cv, for this I am using Fisher Catalog 12 Section 2 tab. In one of the formulas they use x-Ratio of pressure drop to upstream absolute static pressure (dP/P1), dimensionless.

 

I wouldn't recommend to use "unknown" sources. ISA-75.01.01 is widely used for this service. There you can find all terms and equations.

And one more - you can do this faster with freeware "Fisher Specification Manager". For Cv calculations selfactuated (did you mean selfactuated?) PCV is the same as usual pneumoactuated control valve.

[aika93]

 

 

I am doing PCV calculation( for the first time) for nitrogen supply and  need to calculate valve Cv, for this I am using Fisher Catalog 12 Section 2 tab. In one of the formulas they use x-Ratio of pressure drop to upstream absolute static pressure (dP/P1), dimensionless.

 

I wouldn't recommend to use "unknown" sources. ISA-75.01.01 is widely used for this service. There you can find all terms and equations.

And one more - you can do this faster with freeware "Fisher Specification Manager". For Cv calculations selfactuated (did you mean selfactuated?) PCV is the same as usual pneumoactuated control valve.

 

Thank you. This standart is very usefull. 

 

Regards,

Aidan

[aika93]

Dear All.

 

I calculated C using ISA-75.01.01 refering to Example 4: Compressible flow – choked flow, solve for Kv. I got very small Kv. I did calculation in MathCad, if it is possible,could someone take a look and check me?

 

Best Regards,

Aidan

[breizh]

Hi ,

To me the acronym of PCV  is Pressure control valve .

Other may have different opinion.

You did not attach your calculation.

 

You should also consider the search engine in this forum .

 

Note : If you are not comfortable with the calculation , let you  ask the vendor to support you .

 

Hope this is helping you.

 

Breizh

Edited by breizh, 20 October 2016 - 06:20 PM.

[aika93]

Hello All,

 

Thank you for your answers/help very much.

 

See attached calculation. If someone could check and point my mistakes I will be very thankfull!

 

 

 

[aika93]

Attachment

Attached Files

•  PVSV&N2PCVdraft.zip   108.75KB   15 downloads