MSS SP-156-2019 involves requirements for ductile iron, metal-seated, non-lubricated, eccentric plug valves with flanged, mechanical joint, grooved or shouldered ends. This Standard Practice includes applicable eccentric plug valves in sizes and pressure-temperature ratings specified herein for general-purpose service. Conditions of water hammer, hydraulic pulsation, and excessive operating noise are the result of system design rather than valve design and require special design and construction considerations. This Standard Practice also includes, directly or by reference, identified stipulations on chemical and mechanical material properties, dimensions and classes (designations) of end connections, valve pressure and temperature ratings, workmanship, testing, coating, marking, and preparation for shipment. For definitions of terms used in this Standard Practice, see MSS SP-96.