control valve

Use FirstVue Software --Fisher

ISA 75 Series or IEC 534 Series they have given all the equation

Regards

Jose

i know but this software is not free software

Cv = Q√G÷∫h

Where Q = flow of fluid in gallons per minute required,

G = specific gravity of liquid,

h = pressure drop across the valve

Please recheck the differential pressure of 625 psid through the valve. Something looks funny there, but we haven't seen a P&ID.

Cv = (Q√G) ÷ (√h)

Q = flow of liquid gpm

G = sp.gravity

h = pd

substitute :

Cv = ( (221Lb/Hr.) ÷ ( (60 x 2.2 ) ÷ (3.76) ) √0.94 ) ÷ √700-625

(i-e) 221 lb/hr converted to gpm divided by pd

Cv = 5.038º4

May I know Whats The Line Size

upstream line size is 1" S/160

Down stream size : 1" S/160

but in above calculation 700-625 =pd considered but 625 is pd and inlet pressure is 700psig

our engineering has calculated

Required Cv - 0.019

valve rated cv-0.0750

and select the valve as - globe valve

PLZ TELL ME THESE CALCULATIONS ARE CORRECT OR NOT

I HAVE DOUBT

R U sure Abt line Size

Hi Guest,

I am intrigued as to this application. If your make-up rate is as low as you say i,e 20gph then the flow rate is so low as to render a 'normal' control valve set-up quite meaningless. The Delta P and flow put you into the range of needle valve technology rather than any line sized product.

Therefore the control of the feed water pump is probably the most appropriate solution rather than trying to manage such a minute flow.

Have you considered a positive displacement device delivering directly to the boiler via a non-return valve? The control would be greatly simplified.

Regards,

Massey.

IF U CONSIDER pd 625, THEN THE Cv = 0.1078

Cv is 0.0178, sorry for the error

Post #5 looks correct.

H = pd = (700=625) = 75 [rather than 625]. This makes sense, as for instance in a 625 psi boiler with 700 psi feed water pressure.