I am finding leakage in ball valve,when it is in closed condition.The Teflon seat is loaded by spring force from either end of ball(Inlet & outlet flow).However experts opinion is at cold flow(-20 degF to +275degF)),Teflon doesnt give good sealing.My question 1.what are the characteristics of seat(PTFE) & Ball (steel 440C) which drivers for leakage2.How to determine leakage in between Ball & seat.The problem to my opinion is not the Teflon material. It is usually as a result of the seal pass over the hole in the ball. If the hole edges are not carefully designed and machined/grinded/polished it can scratch the Teflon seal with every pass of the seal over the hole. Dirt, dust and small particles embeded on the ball can scratch the seal too. It is a good practice to use a fine filter on the valve inlet and outlet and use clean fluid.Depends on the size of the leakage is it a liquid or gas? if it gas and it is not too excessive you can immerse the valve inside a vessel filled with aliquid such as water of alchol (EPA) (if you can not use water) and countes the bubbles or accumulate them into a glass vessel. Or use leak detector. What you described sounds like a trunnion ball valve. These come with body bleeds. With the valve shut, you can pipe the body bleed to a lab flow meter. Also you can put a pressure gauge on the body to see which seal is leaking. It is pretty unusual for both seats to leak, but it happens.

MORE NEWS