6 replies to this topic

[Senthilsvce]

Hi

 

i need to size the centrifugal pump minimum flow line control valve

 

Liquid pumped out form External floating roof tank through centrifugal pump and minimum reciculation line of the centrifugal pump connected back to the bottom of the floating roof tank in this minimum recirculation line have FV flow valve i need to size this control valve  

 

Note :  i dont have pump vendor information

 

Downstream of the control valve which pressure i have to consider

 

Upstream of the control valve i consider pump  discharge pressure

 

Minimu flow considered as 30% of the pump rated flowrate

 

 

[fallah]

Hi,

 

You have to get vendor information on value of minimum flow otherwise your sizing based on 30% of the rated flow would be just an estimation; means after getting vendor information you have to come back and check the size of control valve. 

 

Dowstream pressure of the control valve would be the pressure corresponding to liquid static head in the tank and upstream pressure to be estimated discharge pressure of the pump at minimum flow point.

 

Indeed, about the flow of the control valve below link especially the 4th post might help you out:

 

 

http://www.cheresour...cv-calculation/

Edited by fallah, 20 September 2013 - 05:57 AM.

[shekhar dhuri]

Totally Agree with Mr. Fallah.

[Senthilsvce]

Thank you

[Padmakar Katre]

Hi

 

i need to size the centrifugal pump minimum flow line control valve

 

Liquid pumped out form External floating roof tank through centrifugal pump and minimum reciculation line of the centrifugal pump connected back to the bottom of the floating roof tank in this minimum recirculation line have FV flow valve i need to size this control valve  

 

Note :  i dont have pump vendor information

 

Downstream of the control valve which pressure i have to consider

 

Upstream of the control valve i consider pump  discharge pressure

 

Minimu flow considered as 30% of the pump rated flowrate

 

 

Hello,

I will suggest to wait till you receive vendor offers. Usually pump minimum circulation line sizes in P&IDs are kept on hold till the pump model is not selected. Minimum flow requirement if any, vendor will communicate and accordingly you can size the line.

[aba_aci]

Hi shekhar,

 

if you want to get size soon, you can rough estimation of the control valve size with one class under line size.

Please CMIIW

[Rodscott]

Senthilsvce,

 

i am doing a project and i was facing the same problem as you are now.

 

I did a preliminary estimation based on Suction Specific Speed and Specific Speed of the pumps. With these two parameters you can cross the values and estimate a minimum flow as a percentage of pump´s BEP (See file below). Once you do not have the pump curve, you can assume your rated flow as being the pump BEP and calculate that value.

I have just received our pump´s curves and my evaluation was very close to vendor data.

 

 Pumps Ns-Nss-calculator-RevA.xls   39.5KB   81 downloads

 

I hope this help you!

 

PS: I found this spreadsheet on internet but i do not have the name of a person who did it. Sorry!

 

Rodscott

Edited by Rodscott, 23 September 2013 - 02:04 PM.