The Intriguing Story of the Pressure Seal Valve(3)

A SIGNIFICANT CASE

As the 1940s ended and the 1950s began, some of the Hobbs licensees stopped paying him royalties. This obviously did not sit well with Hobbs who had no desire to take a vacation from engineering design work and what it paid. Hobbs resorted to a lawsuit against Wisconsin Power & Light and Powell. The lawsuit was initially won by Hobbs; however it was eventually overturned by the Court of Appeals for the Seventh Circuit in 1957. The case is now famous and is referenced often in the field of patent law.

Prior to the introduction of pressure-seal technology for valves, several manufacturers provided welded bonnet valve designs in all size ranges to eliminate any gasket seal flow path. This design worked well, but resulted in large valves that were very difficult and expensive to repair and maintain.What transpired from the proceedings was that Hobbs had no right to the technology because it was in the public domain at the time of his involvement. The technology had in fact been perfected by Dr. Percy W. Bridgman from 1905 to 1908. Bridgman developed the seal by necessity as an adjunct to his ultra-high-pressure research. He detailed his joint in his book, The Physics of High Pressure, published in 1931. The pressure-seal joint he developed as applied to pressure vessels and pipe connections was referred to as the “Bridgman Joint” as late as the 1950s and 1960s.

A BOON TO HIGH PRESSURE

The pressure seal valve was truly a problem-solver for the high-pressure steam industry. It was the perfect technological match for the welding expertise that now made excellent, high-integrity butt-weld ends commonplace.

Up until this time, valve design and pressure ratings were derived from the existing flange standards, primarily the American Society of Mechanical Engineers (ASME) B16.5, Pipe Flanges and Flanged Fittings. Since the pressure seal valves had no body/bonnet flanges, a new standard for pressure temperature ratings was needed. This standard was developed by the Manufacturers Standardization Society as SP-66, Design and Ratings of Steel Butt-weld End Valves, in 1964. It would serve as the design standard for pressure seal valves until the development of ASME B16.34, Valves‒Flanged Threaded and Welding End, in 1974.

Today, pressure seal valves are manufactured of low carbon steel, chrome/ moly and austenitic stainless steel in pressure classes up to 4500. Pressure seal design today is fairly standardized by manufacturers all over the world. This current calm attitude of universal pressure seal design acceptance is a far cry from the battles waged in the power houses and court houses of 50 years ago…all over a tapered ring of soft steel.

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