Diaphragm Valves

A diaphragm valve closes by pressing a flexible diaphragm down onto a seat or weir within the body, sealing the flow. The diaphragm isolates the operating mechanism (the stem and bonnet) from the medium, so there is no path for leakage past a stem and no crevice where product can be trapped. This makes diaphragm valves well suited to corrosive, abrasive, viscous and hygienic services where a metal-seated valve would corrode, clog or harbour contamination.

Two body forms are common. The weir type raises a low sill under the diaphragm, giving good regulation and low travel, which suits throttling and clean shut-off. The straight-through (full-bore) type has no weir and drains completely, which suits slurries, viscous media and self-draining hygienic lines. The diaphragm itself is the wear part and is selected from EPDM, NBR, butyl, PTFE-faced and other elastomers to match the medium and temperature.

Applications span water and wastewater treatment (particularly chemical dosing), the chemical and mineral industries, and pharmaceutical, food and beverage processing where cleanability and the absence of dead space are essential. Diaphragm valves handle acids, alkalis, chlorine solutions, slurries and ultra-pure fluids, and are readily lined for aggressive chemical duty.

Bodies are made in cast iron, ductile iron and stainless steel, plain or lined with rubber, PTFE or glass, with flanged, threaded, clamp or weld ends to EN 1092 or ASME B16.5 and hygienic connections where required. Design and testing follow EN 13397 for diaphragm valves in industrial application.

When specifying, provide the bore, pressure and temperature, the medium (including concentration where corrosive), the preferred body form (weir or straight-through), the lining and diaphragm material and the actuation. We can then propose a configuration for the service.