swing wafer check valves
When the swing wafer Check Valve opens, the flap is forced into
the top of the pipeline. Subsequently, the flap must have a smaller diameter
than that of the pipeline, and because of this, the pressure drop across the
valve, which is often high for swing type valves, is further increased.
Swing type Check Valves are used mainly on larger pipeline sizes,
typically above DN125, because on smaller pipelines the pressure drop, caused by
the disc 'floating' on the fluid stream, becomes significant. Furthermore, there
are significant cost savings to be made by using these valves on larger sizes,
due to the small amount of material required for the construction of the valve.
There is however one problem with using larger size valves; due to their
size, the discs are particularly heavy, and therefore possess a large amount of
kinetic energy when they close. This energy is transferred to the seat and
process fluid when the valve slams shut, which could cause damage to the seat of
the valve and generate waterhammer.
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