Industrial process control often involves the management of fluid flow, either by simple on-off flow control, throttling, or diversion of flow to alternate destinations. Valves of many different designs and construction features provide distinct advantages for particular applications depending upon a variety of media characteristics, operational requirements, physical restrictions, and regulatory requirements.
Plug valves, so named for the generally tapered or parallel-sided structure held in the flow path by the valve body, have wide application throughout the fluid control field. Their advantageous features include simple design, low maintenance, moderate size, minimal flow resistance when fully open, and quarter-turn operation.
Cutaway view of sleeved plug valve with design features labeled Courtesy Fluoroseal
One subset of the plug valve family, the sleeved plug valve, has an additional advantage. It does not require lubrication. The metal plug is wedged within a sleeve, usually, PTFE or a similar material, which provides a seal around the plug and a self-lubricating surface to facilitate rotation of the plug within the body. One manufacturer, FluoroSeal, provides a broad offering of sleeved plug valves. The illustration (left) provides a cutaway view of one of Fluoroseal’s valves of this type with primary design features labeled by the manufacturer as follows:
Bidirectional in-line bubble-tight seal independent of line pressure
Multiple external bubble-tight seals independent of line pressure
Direction mechanical three-point adjustment independent of line pressure
Independent travel stops
Full encapsulation and retention of all leading edges of PFE sleeve and top seal components
The full lip at port openings protects PTFE sleeve
A contoured waterway ensures minimum flow turbulence characteristic
No body cavities to entrap flow media
Positive flow direction indication
Drilled and tapped flange actuation mounting pads independent of cover and top sear assembly.
This versatile valve type is available in a number of variants suited to particular applications. These variants include:
Multiport configurations for flow diversion.
Caged plug version for use with a range of abrasive fluids
Double block and bleed design
Fire-safe versions with additional sealing and venting to prevent leakage if the valve is overheated in a fire
Severe service variant to provide tight emission control and suitability for demanding applications with thermal cycling or a high operating rate
Special cleaning, testing, production methods, or other specialized tasks are needed to assure safety or performance under very specific application conditions found in various industries.
Cutaway view of sleeved plug valve with design features labeled