Table of Contents

1. Scope

This standard gives instructions for the use of Company control vale calculation sheet form BN-K 006.

2. General

The formulas and valve slide-rule are in accordance with the "Recommended voluntary standard formulas for sizing control valves", issued by the Fluids Control Institute with bulletin
F.C.I. 62-1.

However, temperature corrections have been added to these recommended basic formulas.

The valve sizing formulas have been based on the "U.S. VALVE FLOW COEFFICIENT CV", which is the yardstick of the valve capacity.

A valve flow coefficient CV is the number of U.S. gallons per minute of water at 40 to 120°F which will pass through a given flow restriction with a pressure drop of 1 psi.

The determination of the valve CV by the manufacturer should be based on Fluids Controls Incorporation, bulletin F.C.I. 58-2.

Because the CV coefficient is measured by the valve manufacturer at rather low pressure drops across the valve and at rather low static pressures the CV coefficient will be lower at higher pressure drops, depending upon the type of valve and design of the valve body.
Reference is made to booklet "The valve flow coefficient and its contribution in control valve sizing" and to the section "Limitations of valve sizing formulas", sheets 19 and 20.
European and especially German manufacturers sometime use a "Valve Coefficient KV ".
A valve flow coefficient KV is the number of cubic meters per hour of water at 5 to 30°C which will pass through a given flow restriction at a pressure drop of 1 kg/cm2.

Kv = 0.86 Cv and Cv = 1.17 Kv

A few valve manufacturers in Great Britan specify the Cvalve coefficient based on an "Imperial gallon", instead of the U.S. gallon.

Cv (Imp. gpm) = 0.83 Cv(US gpm)

and Cv (US gpm) = 1.2 Cv(Imp. gpm)

The full procedure is available for registered users.