Disc Check Valves

 

Disc check valves, also called as non-return valves allow the flow to pass through them in only one direction and stop the flow in reverse direction. Because of this unique directional property, disc check valves are essentially used for some critical applications in the steam systems.

There are four major types of disc check valves as follows-

a) Lift Check Valve- Lift check valves work simply on the principle of gravity. When the fluid comes in the forward direction, the disc gets lifted from the seat against the gravitational force by the force of incoming fluid. The valve thus allows fluid to pass in this direction. When the fluid comes in opposite direction, it supports the force of gravity and the disc remains on the seat, keeping the valve closed. Tight shutoff can be difficult to achieve in case back pressures are low. The valve will leak the fluid in such situations.

 

b) Swing Check Valve- Swing check valve have a disc or the closing element that swings around a point to which it is hinged. When the fluid comes in the forward direction, the disc swings in an open position allowing the fluid to pass. When the fluid flow comes in the opposite direction, the disc swings and rests on the seat to lose it.

c) Spring loaded Check Valves- In this kind of check valves, tight shut-off it provided using a spring. The spring holds back the disc on the seat. Even in the forward flow condition, the fluid should exert some pressure, called cracking pressure in order to open the disc against the spring pressure. These valves are compact in design as compared to the conventional swing and lift type of disc check valves. They can be easily mounted in between flanges in any direction

d) Diaphragm Type Check Valve- This kind of check valves uses diaphragms arranged in such a way that that open to allow the flow only in forward direction. When flow comes from the reverse direction, the diaphragms remain closed.