Diaphragm Valves by John Valves
A diaphragm valve is used for both isolation and throttling duties. It is manufactured with an elastomeric diaphragm that is pressed by a plug above the diaphragm into the flow to throttle or isolate the flow of the media. Complete isolation occurs when the diaphragm comes in contact with the seat inside the valve body.
Diaphragm valves are available in “straight-through” or “weir” styles. In a weir-style diaphragm valve, the internal body surface is shaped such that the media flows over a ridge or saddle. This type is better suited for throttling applications due to its quick opening characteristic. As the straight-through valve name suggests, it has a straight through flow path. However, it is not a full port, as the diaphragm protrudes into the flow at the top of the valve. These give better flow characteristics than “weir” style valves making them better suited for slurries, sludges, etc. They are not as accurate when throttling or suitable for higher temperature fluids due to the design of the diaphragm having to be more flexible to seal on the bottom of the valve body.
Both types of diaphragm valves can be used for abrasive media and chemical applications as the valve bodies can be lined with rubber or PTFE and the diaphragm material can be selected to suit the applicable media.
Frequently Asked Questions About Diaphragm Valves
A diaphragm valve serves the purpose of both isolation and throttling duties. It is designed to control the flow of fluids by utilising an elastomeric diaphragm. When the valve is in operation, the diaphragm is pressed by a plug or disc against a seat within the valve body, effectively throttling or isolating the flow of the media.