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TECHNICAL
What type of check valve should I use ?
By Patrick Gordon of Calafrica ( technical @ calafrica . co . za )
There are two types of check valves , or as most people call it non-return valves . The first one is a swing type check valve .
This valve is recognisable by its free-swinging gate ( flap ) on the inside that seals when the weight of the water forces it closed . The sealing face of this device is normally perpendicular to the direction of the flow .
This forces the user to only use it on an ascending line so that the sealing face closes with the aid of gravity . Both the sealing faces are metallic and thus a positive seal is difficult to achieve . This design feature also causes the flow of liquid to be shut off suddenly and is susceptible to causing water hammer when any reverse flow happens .
The other type of valve is a Spring Type Check valve . In this valve the sealing faces are forced together by a coil spring . When there is no flow and the force of the water on the seal is at balance the force of the spring will close the valve . A positive water flow is needed to open the seals from each other . This design is such that a very soft closing action is achieved and thus water hammer is seldom experienced . The one sealing surface is normally constructed from a neoprene type of material that enables easier sealing .
If we take this information into account , it is obvious that only a Spring-Loaded Check Valve should be used for normal potable water installations . One of the drawbacks of the Spring-Loaded version is that it can ’ t handle very high temperatures . Swing type check valves can handle the heat but lack the capabilities that is required from a high heat type of installation like a solar heating system . There are however many different products that are specially designed to handle these requirements . For more information on alternative products contact your specialist valve manufacturers . PA
“ There are two types of check valves , or as most people call it non-return valves .”
PLUMBDRAIN AFRICA 2022
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www . plumbingafrica . co . za @ plumbingonline @ plumbingonline @ PlumbingAfricaOnline February 2022 Volume 27 I Number 12