Plug Valves

Plug valves rotate a cylindrical or tapered plug 90° inside the body bore to open or close the flow passage. The plug itself is the sealing element—its outer surface contacts the body seat surface directly, or through an intermediate seat insert, to achieve shutoff. That direct plug-to-seat interface is the fundamental characteristic that distinguishes plug valves from ball valves (where a separate seat ring contacts the ball) and gate valves (where a flat gate slides between two seat rings). FLOWKS manufactures six plug valve configurations spanning three seating philosophies and three mechanical motion types. Lubricated plug valves inject sealant through external fittings into internal distribution grooves on the tapered plug surface—the lubricant film creates both the primary sealing boundary and the rotational lubrication layer that prevents metal galling. Soft seated plug valves use PTFE, reinforced PTFE, Viton, EPDM, or NBR inserts bonded to the body bore or plug surface—soft seat compression fills surface irregularities for bubble-tight zero leakage, no external lubricant needed. Pressure balanced plug valves route line pressure to both sides of the plug through internal bypass passages—hydraulic forces cancel out, operating torque stays manageable at Class 600-900 and 12"-24" sizes where unbalanced torque would exceed manual or actuator capability. Lift type plug valves raise the plug off the seat before rotating—zero sliding contact during rotation eliminates seat wear, limited to 1/2"-4" sizes where the lift distance is short. Expanding plug valves (Venturi) use expandable sealing elements (slips/wedges) that move outward against reduced-diameter body seat faces—double-block-and-bleed sealing in a single valve body, with some open-state pressure drop through the venturi constriction. Expanding plug valves (Full Bore) apply the same expanding mechanism against full-diameter seat faces—DBB sealing plus piggable unrestricted flow passage, at higher mechanical complexity and cost than the venturi design.

FLOWKS plug valves provide quarter-turn shutoff through direct plug-to-body sealing contact across the widest range of pressure and seating requirements. Oil lubricated plug valves create a hydrostatic seal through injected lubricant film between tapered plug and body bore—specified for crude oil, natural gas, and refinery service where line media degrades elastomer seats. Soft seated plug valves achieve bubble-tight zero leakage through PTFE, reinforced PTFE, Viton, or EPDM seat inserts—no external lubricant, lower torque, ideal for chemical, water, and process isolation up to Class 300. Pressure balanced plug valves cancel hydraulic force on the plug face through internal bypass passages—manageable operating torque at Class 600-900 on 12" through 24" pipeline isolation where unbalanced torque exceeds actuator capability. Lift type plug valves raise the plug off the seat before rotation—zero sliding friction, zero seat wear, limited to 1/2"-4" sizes for instrument and sampling isolation. Expanding plug valves (Venturi) deliver double-block-and-bleed sealing in a single valve body through outward-expanding sealing elements against reduced-diameter seat faces—compact seat geometry, some open-state pressure drop. Expanding plug valves (Full Bore) provide DBB sealing plus piggable unrestricted flow passage through full-diameter expanding slips—zero open-state pressure drop, pigging-compatible, at higher mechanical complexity.