Flanges specified in the Standard Practice should be used only with the lens gaskets specified herein. This Standard Practice is similar in intent to ASME B16.5, but governs a higher pressure class and lens gasket connection. At the time of writing this Standard Practice, no American Standard existed for pipe walls as heavy as required for this pressure class. Such piping is done mostly with seamless steel tubing. However, for purposes of flange and stub standardization, a definite set of outside diameters has been specified.
This Standard Practice establishes requirements for cast and forged steel flanges (welding neck and straight threaded) and threaded stubs designed especially for use in the chemical industry with end connections making use of lens gaskets.