Submittal Sheet

S2-8
STEP ONE
STEP TWO
STEP THREE
STEP FOUR
Determine the designed Cv by using the following equation.
Cv =
Q G
Where
= Flow in gallons per minute (GPM) required to pass through the valve
= Specific gravity of fluid *
= Designed pressure drop across the valve in PSI
= Flow coefficient
Q
G
Cv
NOTES
* Specific gravity is negligible (equal to 1) for water below 200˚F. Use actual specific gravity
of pure fluids other than water. In most cases, the valve selected for a H
2
O mixture will not
be affected by the specific gravity.
EXAMPLE
OPTION 1
LINE SIZE SIZE FOR PRECISE CONTROL
The Specific Gravity of 50% Water
(Compound 1) and 50% Ethylene
Glycol Solution (Compound 2):
Determine whether the valve should be line size or sized to match the designed pressure drop
(typical for modulating applications where precise control is required.)
Determine the actual pressure drop using the below equation.
Go to page S2-9, ST2 Series Quick
Reference Charts. Using the line size,
find a valve of the same size with a Cv
that best matches the one calculated
in Step 1.
Go to pages S2-10 (2-Way or 3-Way),
ST2 Series Piping Geometry Charts.
Find the line size at the top of the chart.
Scan down the page to the Cv that best
matches the one calculated in Step 1.
OPTION 2
Cv
Q G
=
2
Check to be sure that the close-off requirements are met. Refer to Page S2-11 - S2-14.
If the pressure drop is acceptable
†
, go to Step 4.
If not, repeat Steps 2 and 3, selecting an alternate valve.
Specic Gravity (G)
wt% of Compound 2
Specic Gravity (G)
= +
1
G
soln
wt% of Compound 1
1
0.5
1.0
0.5
1.113
1.05
+
=
=
Specic Gravity
† Recommended to be no higher than 35 PSI or match the designed pressure drop,
3, 4, 5, and 6 PSI are commonly accepted for modulating applications.
SoftTouch 2 - Valve Sizing Steps
www.braycommercialdivision.com
13788 West Road, Suite 200A
Houston, Texas 77041
[e-mail]
Phone: [phone]
S2-8