Ads by Google
The disc check valve consists of four main components: the body, a disc, a spring and a spring retainer. The disc moves in a plane at right angles to the flow of the fluid, resisted by the spring that is held in place by the retainer. The body is designed to act as an integral centring collar that facilitates installation. Where a 'zero leakage' seal is required, a soft seat can be included.
A disck check valve
When the force exerted on the disc by the upstream pressure is greater than the force exerted by the spring, the weight of the disc and any downstream pressure, the disc is forced to lift off its seat, allowing flow through the valve. When the differential pressure across the valve is reduced, the spring forces the disc back onto its seat, closing the valve just before reverse flow occurs. This is shown in Figure 12.3.4. The presence of the spring enables the disc check vale to be installed in any direction.
Operation of a disc check valve
The differential pressure required to open the check valve is mainly determined by the type of spring used. In addition to the standard spring, there are several spring options available:
No spring - Used where the differential pressure across the valve is small.Nimonic spring - Used in high temperature applications.Heavy-duty spring - This increases the required opening pressure. When installed in the boiler feedwater line, it can be used to prevent steam boilers from flooding when they are unpressurised.