This standard covers steel, nickel base and other alloy plug valves with flanged or butt-welding ends and ductile iron plug valves with flanged ends in sizes NPS 1/2 through NPS 24 and threaded or socket-welding ends for sizes NPS 1/2 through NPS 2. Valve bodies conforming to ASME B16.34 may have one flange and one butt-welding end, or one threaded and one socket-welding end. This standard covers additional requirements for plug valves that are in full conformance to the requirements of ASME B16.34 for Standard Class 150 through 2500 except that in the case of ductile iron valves, Class 150 and 300, the requirements of ASME B16.42 for pressure-temperature ratings, wall thickness, flange dimensions and ductile iron material shall be substituted. This standard covers both lubricated and non-lubricated valves that have two-way coaxial ports; three-way and four-way plug valves do not fall under the scope of this standard. This standard includes requirements for valves fitted with internal body, plug, or port linings or applied hard facings on the body, body ports, plug, or plug port. The extent of linings and the materials of which they are made are not covered in this standard. This standard covers tandem plug valves which have two independent operating plugs in a single body. Plug valves covered in this standard belong to one of four general design groups that in many cases have different face-to-face and end-to-end dimensions. Some types of plug valves are not made to all patterns. The four groups are described in 1.5.1 through 1.5.4. The short pattern design is found only in Class 150 and 300 where flanged plug valves match the face-to-face dimensions of steel-flanged gate valves in NPS 1 1/2 through NPS 12. The regular pattern design has a plug port area that is greater than the venturi pattern. Valves of the venturi pattern are designed for minimum pressure loss consistent with the reduced port area used in this type of valve. Venturi valves have a configuration of body and plug ports that approximate a venturi throat. The round-port full-bore pattern has a circular port through both the plug and the body that is not smaller than that specified in Appendix A of ASME B16.34 for the applicable valve size and pressure class. The standard nomenclature for valve parts is shown in Figures 1, 2, 3, and 4.