Is it correct to expect a plug valve to hold full test pressure in both flow directions?In this case, I'm looking at a resilient seat eccentric plug valve (6") in a new wastewater force main. Contractor claims full test pressure (150 psi) can only be held in one direction, and not against the "back" of the valve. Is this correct? Some double eccentric plug valves will have poor sealing, but in my knowledge only if the sealing is metallic or not proper soft sealing.The construction itself (double eccentric plug) are in general constructed to give a long-standing excellent seat-sealing both ways.In general a proper constructed valve, knife-gate, gate or double eccentric plug, should be good for the nominal operation pressure both ways, and able to be tested for this(in your case 150LB if this is the valve nomination, or for 1,1 times this).Other type of valves, for instance some knife-gate valves, are constructed in such a way that the knife gate bottom (port) sealing is below lowest port opening section, and the pressure from the liquid is necessary to give a proper sealing by pressing the gate towards the port sealing, eg. one sided sealing, and tendency to poor sealing either way at low pressures.This should not be the case for your type of valve.

MORE NEWS