Plug Valves
Plug valves use a tapered or cylindrical plug as the closing member; rotating the plug 90° about its own axis fully opens or closes the valve. Operation is fast and the design compact, and because the cavity and bore have no dead pockets, media do not settle, making them particularly suitable for rapid isolation of solids-laden, slurry and high-pressure gas service. By sealing and design there are lubricated taper plug valves (sealant is injected to form the seal and reduce friction, suited to solids-laden media), cylindrical plug valves (uniform loading on the plug, low operating torque) and pressure-balanced plug valves (a balance passage offsets radial thrust at high pressure, greatly reducing torque in large high-pressure sizes). Plugs are surface-hardened, sealant is selected to suit medium and temperature, and the sealant can be replenished in service. Pressure ratings cover ASME Class 150–900 (PN 20–PN 150). Body materials include WCB and CF8/CF8M. Design and manufacture follow API 599 and ASME B16.34. Typical services are gas, natural gas, crude oil and slurry lines.
Pressure-Balanced Plug Valve
The pressure-balanced plug valve has pressure-balancing passages in the plug so that the radial thrust of the high-pressure medium on the plug cancels out, significantly reducing operating torque. It is intended for isolation of high-pressure, large-diameter gas media. The plug is grease-sealed and surface-hardened, giving easy operation and reliable sealing in high-pressure natural gas, hydrogen and long-distance pipelines. It is one of the economical alternatives to ball and gate valves on high-pressure gas lines. Design basis: API 599.
Lubricated Cylindrical Plug Valve
The lubricated cylindrical plug valve replaces the taper plug with a cylindrical plug running in a sleeve. The load is distributed evenly around the circumference, the sealing surface is less prone to sticking, and operating torque is lower than with a taper plug. A grease injection system forms the seal, and a 90° turn opens or closes the valve. The flow area is large and flow resistance low, suiting isolation of town gas, natural gas, water and general industrial media, particularly medium- and low-pressure lines of larger diameter.
Lubricated Taper Plug Valve
The lubricated taper plug valve uses a conical plug as the closing member. Sealing grease injected between the plug and the body taper both seals the valve and reduces friction and wear as the plug turns, so the valve still operates easily in media containing solids. When the plug port aligns with the bore the valve is fully open, and a 90° turn completes opening or closing; the plug cavity and bore have no dead pockets where medium can settle. It suits rapid isolation of media with solid particles, slurries and high-pressure gas. Design basis: API 599; the sealing grease is selected to suit the medium and temperature.