Piston Valves

Piston valve
seat tightness in a piston valve is obtained by a cylindrically shaped burnished piston, connected to a spindle, and operated by a hand wheel, which enables it to move through the inner diameter of two sealing rings. The two sealing rings are separated by a ported spacer. The bottom ring rests on a cast machined groove of the body and upper packing ring is being held and remained pressed by a bonnet on top. The bonnet rests on the top ring, when tightened evenly by the nut of the stud presses the spacer, which in turn presses the bottom ring. This is done by keeping the valve in closed position. Thus the mechanism is aligned compressed and ready for operation.
When the piston is in the high position, that is, held by only the upper valve ring, (which also ensures tightness to the atmosphere), the valve is open. When the piston is lowered and is held in place by both the upper and lower valve ring (and thus ensuring seat tightness between the valve inlet and outlet ),the valve is closed . Because of the use of the sealing rings, the piston valve is considered a “soft-seated”, valve. The contact between the piston and rings (sealing effect ) is positively assured by means of the pressure exerted by stud bolts. Spring washers (belleville type), are fitted to compensate expansion due to temperature variations.
application:-
the valve finds it’s best application in tight shut off of steam. They are used in process line s containing many different fluids such as water, steam condensate & thermic fluid line. The valve also has numerous applications in the control of liquid and gases also.