Flowserve Swing Check Valves 2.5-24 - Manual (Page 6)

Swing Check Valves FCD ADENIM0013-00
5
1.0 VALVE DESCRIPTION
1.1 Recommended Uses
Anchor/Darling Swing Check Valves are designed to prevent the reversal of flow in a piping system. While they
may hold pressure in the reverse direction, they are not intended for use as isolation valves without special
provisions e.g. elastomeric seats. A reliable seal across the disc can be expected if the reverse flow or
differential pressure is large. However, when the differential pressure is low, difficulty may be encountered in
obtaining a tight seal without special features being added to the valve. If the system operation requires sealing
against a low pressure, Anchor/Darling should be consulted.
1.2 Principles of Operation (Fig. 1)
The principle parts of a swing check valve are the body, bonnet, disc and hinge assembly. The body and bonnet
contain the fluid within the system. The disc is mounted on a hinge arm which rotates about a shaft positioned
above the seat in the body neck. Flow in the normal direction creates a force on the disc which causes it and the
hinge to rotate about the shaft. With increasing flow the disc assembly is rotated further from the seat up into the
body neck. In the full open position a stop on the back of the hinge contacts the body. This positions the major
portion of the assembly out of the flow stream and permits unobstructed fluid flow through the valve. Upon the
cessation of forward flow or reversal of flow direction, the force holding the disc assembly open is no longer
present, whereupon the weight of the assembly combined with the reverse flow causes the disc to return to the
seat. Any seal obtained between the disc and the seat results solely from the difference in pressure across the
disc. Hence, the difficulty in maintaining a tight seal at low pressures.
Figure 1