Diaphram valves, more properly known as diaphragm valves, are inline devices that utilize a membrane to transect a pipe completely or partially in order to regulate the flow of liquid, gaseous or semi-solid process streams. While a number of different valves are widely available to perform this task, the use of an elastomeric diaphragm in these particular valves significantly reduces both cost and the risk of leaks.
Process valves such as these are capable of starting, stopping and modifying flow rates and pressures as well as ensuring the proper flow directionality. These tasks can be performed through the use of automated systems as with electrical, hydraulic and pneumatic diaphragm valves. Alternatively, manually operated membrane valves are also widely available. In simplified terms, when the diaphragm is engaged by any of the aforementioned actuating devices, the diaphragm or membrane is stretched to the opposite side of the valve.
This effectively forms a barrier. The chemical composition of a process flow as well as the material construction of each diaphragm valve component should be carefully considered as incompatible materials can lead to mechanical failure or malfunction as well as product contamination. Compatible valve materials include polypropylene, ethylene, copper, brass, stainless steel, PVC, CPVC and other durable and chemically resistant materials.
The function and design of a diaphragm valve is relatively simple. The body of the valve is a cylindrical or spherical device that is attached to the necessary piping. This compartment houses the actuating device and stem or rod. Placed directly in front of the rod is the diaphragm. On the opposite side of the pipe is a raised bump.
When the compressed air, hydraulic fluids or manual turning engage the stem it presses down on the diaphragm which is stretched to the desired depth. To shut off flow completely, the diaphragm must cover the entire diameter. When the valve is open the stem retracts and the diaphragm returns to its relaxed position allowing fluids, gases and particulates to pass freely below.
In addition to the material construct of a diaphragm valve, it is important to consider media type, temperature and pressure ratings, frequency of operation, diameter and other dimensions, required end connections and process stream velocity. Diaphragm valve manufacturers and retailers can provide helpful insight and should be consulted before purchasing or installing such a device if any uncertainty persists. Proper installation of a suitable valve provides a reliable and leak proof flow control device to any plumbing or material transport operation.