I was hoping i could get some help on placing a twin plated wafer check valve on the end of a pump rated at 300m3/h. The pipe diameter is 200 mm, 8". I've tried to obtain as many data sheets with CV numbers etc,I want to calculate the pressure head losses. The valve is ideally placed 5 to 10 diameters away from the discharge end of the pump but it will be a lot less than that.You are then at 83,5 l/s and at a speed of about 2,65 m/s, and yes, the valve will give you some presure loss, depending on actual form, but helped by the velocity that will keep the valve fully opened.Please give a bit more information about your application, fluid and pressure conditions and pipeline layout? Exact make of valve - factory should be able to give you the loss directly!Apart from this: if pressure loss, thigt closure and lifetime is an issue, and the fluid is clean (particle free) the obvious better choice would be a non-slam nozzle check-valve. Pump energy savings could be considerable. ALso, placing a check valve "on the end of a pump" is asking for trouble. Pulsations and large-scale turbulence coming out of the pump will beat up the valve. Take it downstream as far as piping will allow, with 10 diameters an absolute minimum. Gerhardl is right about the nozzle-check: the guidepost in the center will help promote durability. The center-hinged valves you described have a loose gap between the hinge pins and the plates. This gives them a very low initial cracking pressure but also accelerates wear if the flow is bouncy.

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