Valve Bonnet:

The cover for the opening within the valve body is the bonnet. In a few designs, the body itself is divided into two sections which bolt together. Such as valve bodies, bonnets vary in design. A few bonnets function easily as valve covers, although others support valve internals and accessories like as the disk, stem, and actuator.

The bonnet is the second principal pressure boundary of a valve. It is cast or forged of the similar material as the body and is linked to the body through a threaded, bolted, or welded joint. Within all cases, the attachment of the bonnet to the body is assumed a pressure boundary. This means in which the weld joint or bolts that links the bonnet to the body are pressure-retaining elements.

Valve bonnets, while a necessity for most valves, present a cause for concern. Bonnets could complicate the manufacture of valves, rise valve size, represent an important cost portion of valve cost and are a source for potential leakage.