Control Valve Rating
Control Valve Rating
(OP)
I have a system on a district CHW system that operates at a fairly high pressure ~130 psi static supply and ~95 psi static return. my question is in sizing control valves. I have been installing valves with a 125 psi close off rating based on the high operating pressure. Though several people have told me I need only to match the close off to the differential pressure about 40 psi. Which is the best method to size the valve?





RE: Control Valve Rating
However, if you 'could' be in a position (startup?) where you have 130 psi on the upstream side and a much lower pressure on the downstream side you need to size for the potential dP to be able to ensure the valve can operate.
Undersizing an actuator for an on-off valve will mean that with higher dPs across the valve, you might not be able to open the valve. If it's a control valve and depending if it's 'flow to open' or 'flow to close', you might not be able to close or open the valve, depending on the flow path.
RE: Control Valve Rating
In so doing, however, you create a wharehouse fiasco, and will have to carefully document the actuator sizing conditions of all your valves.
I have never been a case where an actuator has been over sized, but countless cases where they have been undersized.
Some of the vendors make it a practice to standardize on the worst case actuator for the valve anyway.