The higher the internal pressure, the greater the sealing force. Easy dismantling is made possible by dropping the Bonnet assembly into the body cavity and driving out the four-segmental thrust rings by means of a push pin.
Relying on fairly simple design principles, pressure seal Valves have proven their capability to handle increasingly demanding fossil and combined-cycle steam isolation applications, as designers continue to push boiler, HRSG, and piping system pressure/temperature envelopes. Pressure seal Valves are typically available in size ranges from 2 inches to 24 inches and ASME B16.34 pressure classes from #600 to #2500, although some manufacturers can accommodate the need for larger diameters and higher ratings for special applications.
Pressure seal Valves are available in many material qualities such as A105 forged and Gr.WCB cast, alloy F22 forged and Gr.WC9 cast; F11 forged and Gr.WC6 cast, austenitic stainless F316 forged and Gr.CF8M cast; for over 500°C, F316H forged and suitable austenitic cast grades.
The pressure seal design concept can be traced back to the mid-1900s, when, faced with ever increasing pressures and temperatures (primarily in power applications), Valve manufacturers began designing alternatives to the traditional bolted-Bonnet approach to sealing the body/Bonnet joint. Along with providing a higher level of pressure boundary sealing integrity, many of the pressure seal Valve designs weighed significantly less than their bolted Bonnet Valve counterparts.