I got this out of a manufacturer's engineering handbook:Critical pressure drop occurs if DP>=Fl^2*(P1-Ff*Pv)Ff=0.96-0.28(Pv/Pc)^.5DP is the pressure drop through the valveFl is the liquid pressure recovery factor for the valve. Fl for Globe valves tend to be at about 0.9 or a little more. Look up the published value for the valve you are using.Pv is vapor pressure (absolute units) of your fluid at the system temperature. Pc is the critical pressure of the fluid. If the pressure drop in your system exceeds critical, you can do what is necessary to change variables to prevent DP from exceeding DPcrit. These include: Using a valve with a higher Fl(2) using 2 or more valves in series to split the pressure drop(3) reducing the DP by trimming the pump impeller (consult your pump manufacturer)(3) Raising the system inlet and outlet pressure at the valve (placing the valve in the bottom of a U adds .4335 psi head per foot)(4) reducing the vapor pressure of the fluid by relocating heat sources or cooling the fluid.

MORE NEWS