Until the late 1950s and early 1960s, valve pressure/temperature ratings were based on flange ratings (i.e., ASME B16.5), but the limitations of American Standard B16.5 and its predecessor B16e, along with the popularity of the butt-welding end pressure seal bonnet valve, warranted a new method of rating valves. MSS created SP-66, Pressure Temperature Ratings for Steel Butt-welding End Valves in 1964 to address the limitations. The standard used the mechanical properties of the different body materials to determine the minimum wall thicknesses and ratings of the valves under its scope. The SP-66 document would later be expanded and form the basis of ASME/ANSI B16.34 in 1974. B16.34, Valves—Flanged, Threaded and Welding End, is the most referenced valve design standard in the world.
Flanges and bolt patterns have been standardized since the mid-20th century; however, there were two different flange standards, MSS SP-44 and API 605 for valves over 24 inches in size. Even though the flange designs and bolt patterns are totally different, the difference has never been successfully addressed and continues to plague manufacturers, distributors and end-users.
TESTING AND MORE RECENT STANDARDS
Valve testing standards are a relatively new creation. When the API 600 document was first published (before World War II), testing criteria was simple—valves couldn’t leak during testing. Try selling that concept today! In response to the lack of realistic testing standards, MSS created, SP-61, “Pressure Testing of Valves” in 1961. It has been supplanted substantially by the most widely used testing standard in the U.S. today, API 598, “Valve Inspection and Test,” which was first published in 1968.
During the 1960s through the 1980s, many new valve standards were developed by API, MSS and ASME. These new standards covered a variety of valve types, including check, butterfly, ball and others. Although most of the valve standards emerged from API, MSS and ASME, other standards organizations were also developing valve standards. Across the pond, for example, was the British Standards Institute, which created several standards used in the U.S. for many years. Also, the International Organization for Standardization (ISO), which published its first standard in 1947, has been very active in valve standards creation during the past 25 years. Some of the ISO standards are used regularly in the U.S.
For the water and wastewater industry, the American Water Works Association has created general standards, while the International Society of Automation is the creator and custodian of control valve specifications.
The history of valve standards is a still being written: Old standards are revised and new ones created. In API, for example, standards created during the past 20 years have covered valve repair, valve qualification, fugitive emissions testing and fire testing of valves, to name a few.
When we look at the rich past of the valve industry, we find that valve standardization runs both a parallel and an intertwined path dotted with stories of famous companies as well as great achievements in valve design.
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