Diaphragm Valve Bonnet Assemblies:

A few diaphragm valves use a quick-opening lever and bonnet operator. This bonnet is interchangeable along with the standard bonnet on conventional weir-type bodies. The 90° turn of the lever moves the diaphragm from full open to full close. Diaphragm valves might also be equipped along with chain wheel operators, bevel gear operators, extended stems, air operators, and hydraulic operators.

Several diaphragm valves are used in vacuum service. Standard bonnet construction could be employed within vacuum service by 4 inches in size. On valves 4 inches and larger, evacuated, a sealed, bonnet should be employed. This is recommended to guard against premature diaphragm failure.

Sealed bonnets are supplied along with a seal bushing on the nonindicating categories and a seal bushing plus O-ring on the indicating categories. Construction of the bonnet assembly of a diaphragm valve is described in Figure. This design is recommended for valves which are handling dangerous gases and liquids. In the event of a diaphragm failure, the hazardous materials will not be released to the atmosphere. It is recommended that a means be given to allow a safe disposal of the corrodents from the bonnet if the materials being handled are very hazardous.