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| Check Valves are designed to automatically prevent the reversal of flow in a pipeline system. They control the direction of flow, rather than throttling or isolating flow as other valve designs do. Reverse flow may create problems or it could cause damage to equipment. Check valves are sometimes known as reflux valves. | |||||||||||||||||||||||||||||
| There are several basic designs of check valves, these are:
Swing Check Valves This type of check valve uses a hinged mounted disc that swings open and closed with flow. They can be used in the horizontal and vertical (flow upwards) position. The swing check is the most commonly used design of check valves as they do not restrict flow. Typical swing check valves in the John Valves range are our figure numbers 4B, 404 and 4205, and more details may be found in our Online Valve Catalogue. |
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| Lift or Piston Check Valves
This type of check valve uses a piston rather than a hinge mounted disc to prevent the reversal of flow. This provides a cushioning effect during the operation of the valve. They must only be used in a horizontal position. Lift check valves, like globe valves are flow restricting, therefore they are generally used as companions to globe valves. Typical lift check valves in the John Valves range are our figure numbers 121 and 521, and more details may be found in our Online Valve Catalogue. |
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| Dual Flap Check Valves
These check valves are of wafer design and fit between flanges. The valve discs are in two halves and are held in the closed position by a stainless steel spring. The reaction of the stainless steel spring quickly and quietly shuts the valve off before the flow in the line can reverse and water hammer is virtually eliminated. The valve can be installed in horizontal or vertical lines. The dual flap check valve available from John Valves is our figure number 430, and more details may be found in our Online Valve Catalogue. |
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| Air Check Valves
These are check valves specifically designed for compressed air services. The disc is manufactured from flat stainless steel and is held against the seat by a spring. The spring holds the disc against the seat whilst the compressor is idling or in-operative. It is recommended that the valve be located at least 3 metres from the compressor. The air check valve available from John Valves is our figure number 551, and more details may be found in our Online Valve Catalogue. |
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