Calculating A Reasonable Safety Factor when Sizing Control Valves & Regulators
It is important to include a reasonable safety factor when sizing.
I am often asked, “How do I calculate a safety factor when sizing a control valve or regulator?” It is important to include a reasonable safety factor when sizing. At the same time, be sure to avoid an excessive safety factor as it can be expensive (purchasing a larger valve than required) and lead to instability in the process. Ideally, pressure regulating valves (PRV) should operate between 30% and 70% open; control valves between 20% and 80% open, with the minimum and maximum flow rates falling close to or within that range.
Many sizing programs calculate the actual Cv required. When sizing the following valve types, the calculated Cv should be divided by:
PRV (pressure regulator): 0.7
BPRV (back pressure regulator): 0.5
PPRV/PBPRV (piloted PRV/BPRV): 0.9
TCV (temperature regulator): 0.9
DCV (diaphragm operated control valve): 0.9
MOV (motor operated control valve): 0.9
This practice will ensure you have a reasonable safety factor.
Our sizing program, JVCV, is available by going to our website at website. For your convenience, two versions are available, a downloadable version and a web based version. The input screen is easy to use and customizable by application.
JVCV Results Screen
The JVCV sizing program is used for Jordan Valve industrial control valves and regulators. The Steriflow sizing program, SVCV, is used for our line of sanitary control valves and regulators applied primarily in the Pharmaceutical and Bio-Pharmaceutical industries. LVCV, the LowFlow valve sizing program, is used for sizing our fractional flow control valves and regulators.
Multiple outputs are available from each of these programs. You can find our other sizing programs by going to www.steriflowvalve.com and www.lowflowvalve.com.