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Control valve sizing

How to calculate control valve sizing

By tushar on 18 June, 2009 - 6:53 am

dear all,

i am trying to calculate control valve sizing. can anybody guide me for calculating Cv using various formulas.

By Miguel Chen on 18 June, 2009 - 11:36 pm

Dear Sir,

We are control valve manufacturer in Taiwan! I could send you one formula attachment for calculating water CV under the planned circumstances,and you could check the CV value result. By comparing the CV value offered by each brand for chooosing control valve's size of each different brand.

Please contact me since I could not attached the calculation document in this coulumn.

Best Regards,

Miguel Chen/Elite Line

By vahid on 19 June, 2009 - 9:11 am

hey there,

could you send me the formula or anything about the control valve sizing info. to me as well?? thank you very much. my email address is lscnlemon [at] yahoo.com.cn

By tushar on 20 June, 2009 - 4:43 am

Dear Miguel Chen,

Could you please e-mail to me your formula also. It could be useful for me.

Best Regards,

Faizul

faizulism4007 [at] yahoo.com

By Vivek Shah on 13 November, 2010 - 4:30 am

Dear Sir,

We are EPCC Agency for Pneumatic conveying systems for solid handeling based at Baroda, India.

We required approx 200 different valve for our project.

We float the inquiry for valves. we got some quote with valve sizing data. In that How to check the rated CV for particular valves.

Can you help in this regards.

Thanking You.

Regards

Vivek Shah

Project Engineer

For,

Zeppelin Systems India Pvt. Limited

Level 4, ADM Building,

Alembic Campus, Alembic Road,

Vadodara-390003

India.

By mr GZul on 16 November, 2010 - 2:42 am

>We are control valve manufacturer in Taiwan! I could send you one formula attachment for calculating water CV under the planned circumstances,and you could check the CV value result. By comparing the CV value offered by each brand for chooosing control valve's size of each different brand.

>

>Please contact me since I could not attached the calculation document in this column.

Send that to me sir, i am working as Trainee in Instrumentation field

n_rakesh_kumar@yahoo.com

By Dinh on 4 March, 2011 - 10:39 am

Dear Miguel Chen/Elite Line,

I am looking for control valve (Taiwan). pls send me catalogue of you. My email: thietbicongnghiep79@gmail.com

Best regards

By anri on 19 June, 2009 - 2:01 am

Its a huge question. there are large books on that issue. try finding any 'conrol valve handbook' that can be very helpful. besides there are too many parameters to consider

By MRKS Sastry on 19 June, 2009 - 2:50 am

Tushar,

I would ask you to go to www.google.com and type Fisher Control Valve Handbook" and download the book. this book gives you the required information about Control Valves - selection, sizing etc.

I found this book very useful. whatever you discuss in the forum, it is less. Go for that book - it is a free download.

My suggestion: Get the previous datasheets of your plant related to Control valves and try to use the formulae given in the book and check the calculated values. Thereby, you get a lot of practice.

Good Luck!

It depends for which application control valve you want to size as for liquid,gas etc.they have different sizing factor.U can search on net...there is a thumb rule u can follow it for liquid application

Step1.Observer the dia of the pipe for which control valve is required.

e.g 300mm

Step-2: Take the half of the value of pipe size

e.g 150mm

step-3 pick the control valve one size higher than the available in the market

e.g 200mm

By wboyes on 19 June, 2009 - 3:36 pm

We host the Fourth Edition (current one)of the "Little Black Book" also known as the Fisher Control Valve Handbook at

http://www.controlglobal.com/whitepapers/2006/059.html.

It is a reference no engineer should be without.

In addition, there are other white papers on control valves, from Metso, Emerson, Honeywell, and others.

But the real star of the show is the three part series by Bela Liptak on sizing control valves:

Part One: http://www.controlglobal.com/articles/2006/132.html

Part Two: http://www.controlglobal.com/articles/2006/167.html

Part Three: http://www.controlglobal.com/articles/2006/215.html

As part of this series, Bela created what I believe is the only modern impartial guide to control valve selection:

http://www.controlglobal.com/Media/MediaManager/article_132_controlvalves.pdf

I hope this helps!

Walt Boyes

Editor in Chief

Control and Controlglobal.com

www.controlglobal.com

Mailto:wboyes [at] putman.net

Read my blog SoundOFF!! At www.controlglobal.com/soundoff

Hi there,

It is not all that complicated once you have the right formulas to work with. Here are some examples.

LOOK AT THE NOTES AT THE BOTTOM FIRST BEFORE YOU READ ANY FURTHER!!!!

Calculate the cv of a LIQUID ONLY control valve for a given flow, dp and sg

Cv = 11.7 q (SG / dp)1/2where

q = Expected flow rate (m3/h)

Sg = Specific gravity of the liquid (1 for water in this example)

dp = Pressure drop across the valve at expected flow rate (kPa)Example 1.

So if q = 5m3/h

Sg for water = 1

Dp over valve during 5m3/h flow = 10kpaDo manual calculation:

Cv = 11.7 q (SG / dp)1/2

1) 11,7 x 5 = 58,5

2) 1/10 = 0,1

3) ½ = 1/2 = 0.5

4) 0,1 to the power of 0,5 = 0.31622776

5) So 0.31622776 x 58,5 = 18,49So a valve with a cv of 18,5 is needed to do a flow of water(sg=1) at 5m3/h and a dp over the valve of 10kpa

Look at manufacturer valve manual for available valves and

select a valve with a next bigger Cv.----------------------------------------

Example 2.

So if q = 30m3/h

Sg for liquid = 0,97

Dp over valve during 30m3/h flow = 110kpaDo manual calculation:

Cv = 11.7 q (SG / dp)1/2

1) 11,7 x 30 = 351

2) 0,97/110 = 0,008818

3) ½ = 1/2 = 0.5

4) 0,008818 to the power of 0,5 = 0.0939042

5) So 0.0939042 x 351 = 32,96So a valve with a cv of 32,96 is needed to do a flow of

liquid (sg=0,97) at 30m3/h and a dp over the valve of 110kpaLook at manufacturer valve manual for available valves and

select a valve with a next bigger Cv---------------------------------------

Example 3.

So if q will be 64m3/h

Sg for liquid is 0,87

Dp over valve during 64m3/h flow is 210kpaDo manual calculation:

Cv = 11.7 q (SG / dp)1/2

1) 11,7 x 64 = 748,8

2) 0,87/210 = 0,00414285

3) ½ = 1/2 = 0.5

4) 0,00414285 to the power of 0,5 = 0.06436497

5) So 0.06436497 x 748,8 = 48,196

So a valve with a cv of 48,196 is needed to do a flow of liquid (sg=0,87) at 64m3/h and a dp over the valve of 210kpaLook at manufacturer valve manual for available valves and

select a valve with a next bigger Cv------------------------------------------

To do the power off calculation on your windows calculator:

Example:

5 to the power of 4press 5 then x^y then 4 then =

--------------------------------------------

Control Valve selection Flow Coefficient - Cv - for Air and other Gases

For critical pressure drop the outlet pressure - po - from the control valve is less than 53% of the inlet pressure - pi. The flow coefficient can be expressed as:

Cv = q [SG (T + 460)]1/2/ 660 pi

where

q = free gas per hour, standard cubic feet per hour (Cu.ft/h)

SG = Specific gravity of the gas relative to air at 14.7

psia and 60oF

T = flowing air or gas temperature (oF)

pi = inlet gas absolute pressure (psia)Example:

5000 = Gas flow (Cu. ft./h) (f.a.d)

100 = Inlet Gas Absolute Pressure (psia)

1 = Specific gravity of the gas

60 = Gas Temperature (oFDo manual calculation:

Cv = q [SG (T + 460)]1/2/ 660 pi

1) 60 + 460 = 520

2) 520 x 1 = 520

3) ½ = 1/2 = 0.5

4) 520 to the power of 0,5 = 22,8035

5) 22,8035 x 5000 = 114017,5425

6) 660 x 100 = 66000

7) 114017,5425 / 66000 = 1,727So a valve with a cv of 1,73 is needed to do a air flow (sg=1) at 5000Cu.f/h, at a air flow temp of 60F and a inlet gas absolute press of 100PSIA

Look at manufacturer valve manual for available valves and select a valve with a next bigger Cv

-----------------------------------------------

For non critical pressure drop the outlet pressure - po - from the control valve is greater than 53% of the inlet pressure - pi. The flow coefficient can be expressed as:

Cv = q [SG(T + 460)]1/2/ [1360(dp*po)1/2]

where

dp = (pi - po)

po = outlet gas absolute pressure (psia)Example:

6000 = Gas flow (Cu. ft./h) (f.a.d)

140 = Inlet Gas Pressure (psia

110 = Outlet Gas Pressure (psia

1 = Specific gravity of the gas

60 = Gas Temperature (oF)Do manual calculation:

Cv = q [SG(T + 460)]1/2/ [1360(dp*po)1/2]

1) 60 + 460 = 520

2) 520 x 1 = 520

3) ½ = 1/2 = 0.5

4) 520 to the power of 0,5 = 22,8035

5) 22,8035 x 6000 = 136821,051

6) 140 - 110 = 30

7) 30 x 110 = 3300

8) ½ = 1/2 = 0.5

9) 3300 to the power of 0,5 = 57,445

10) 57,445 x 1360 = 78126,05199

11) 136821,051 / 78126,05199 = 1,75So a valve with a cv of 1,75 is needed to do a air flow (sg=1) at 6000Cu.f/h, at a air flow temp of 60F and a DP of 30PSIA absolute press

Look at manufacturer valve manual for available valves and

select a valve with a next bigger Cv--------------------------------------------------

To do the power off calculation on your windows calculator:

Example:

5 to the power of 4 ------- press 5 then x^y then 4 then =

--------------------------------------------------

NOTE!!!

Please note the "1/2" in the formulas is not as it seems, it is suppose to be a small "1/2" on the top right hand corner of the bracket, in other words a "to the power of 1/2" and

not " bracket times 1/2 as it is displayed"

Cannot seem to get it displayed like that on this page - sorry if it is confusing but look at he calculation to see where the "power of" is used and you will understand what I mean.

Good Luck

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By Mary on 26 November, 2010 - 1:32 am

Dear sir

I have been working on the power calculation in control valves but couldn't come to a specific conclusion. could you help me with the

formula used in power calculation and power factor details for (control valves)

id chindud@gmail.com

archana@severnglocon.com

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Mary... if your question was addressed to me, then there is some confusion.

Power and power factor calculations are not related to valve sizing. However, perhaps your question is related to motor sizing?

Regards, Phil Corso

By archana on 11 October, 2011 - 4:36 am

our sizing data sheet produces a factor called power and power factor and maximum power based on the fluid medium the power formulae varies and based on the size the maximum power varies to some constant inbuilt value and the power factor is the ratio of the power calculated to the max power

just wanted to know what this power is all about is it related to