Concentric Butterfly Valves
Concentric butterfly valves are quarter-turn isolation and throttling valves in which a centred disc rotates on a shaft that passes through the centre of the disc and the centre of the bore, sealing against a full elastomer liner that lines the body bore. A 90 degree turn of the shaft moves the disc from fully open (edge-on to flow) to fully closed (face-on against the liner). The rubber liner provides bubble-tight shut-off and isolates the body metal from the medium, which makes the concentric, resilient-seated pattern the economical workhorse for water, HVAC, low-pressure utility, fire-water and many chemical and food lines.
Resilient-seated butterfly valves fall under API 609 Category A and EN 593 / ISO 5752, with seat and shell testing to API 598 and the leakage and operation criteria of MSS SP-67. They are normally rated to ASME 150 (PN 10/16), with some designs to ASME 300, and sizes commonly run from 2" up to 24"-48" and beyond. Wafer, semi-lug and lugged body patterns are standard, the lugged version supporting dead-end and downstream-flange-removal service.
The liner is the defining material choice: EPDM for water, hot water and many chemicals, NBR for oils and gas, Viton for aggressive media, and food-grade or white liners for sanitary duty. Disc materials range from ductile iron and aluminium-bronze through CF8 / CF8M (A351 SS304/316) and duplex; the body is typically ductile iron, WCB or stainless. The shaft is usually SS410 or SS316, sometimes duplex for chloride service.
Concentric valves are operated by lever (notched plate), worm gear, or pneumatic and electric actuators, with the rubber seat's interference giving a defined seating torque the actuator must cover. ISO 5211 mounting pads are standard for actuation.
Himalay's MSME partners manufacture resilient-seated butterfly valves with testing per API 598 / BS EN 12266-1 / ISO 5208, material traceability, and PED-CE (EU), SABER (Saudi Arabia), and NACE MR0175 (sour service) coordinated as part of the standard order flow.
