Bare Stem High Performance Double Flange Butterfly Valve ISO5211

The bare stem high performance double flange butterfly valve is a double eccentric flange-type isolation valve engineered for process and utility pipelines that require reliable shut-off, standardized actuator mounting and stable flange-to-flange installation. Manufactured by Trekre Valve, this high performance double flange butterfly valve combines a machined ISO 5211 bare stem interface with a double-offset disc geometry so the mounting of pneumatic, electric or worm gear operators requires confirmation of interface dimensions, shaft coupling, torque, travel and any required bracket or adapter. Twin raised flanges on both body ends allow direct bolting to pipeline flanges, making it a practical choice for HVAC chilled water, district heating, industrial cooling, light hydrocarbon, petrochemical and general chemical services where maintenance access and actuator interchangeability matter.

Double eccentric design moves the disc rotation axis off the body centreline and off the disc seal plane, so the disc lifts away from the seat at the first degrees of opening rather than scraping across it. That geometry reduces wear on resilient or metal seat materials, lowers breakaway torque and extends service life on frequently cycled isolation points. The bare stem integrates a standardized top flange pad with bolt circle dimensions per ISO 5211, allowing direct mounting of quarter-turn pneumatic actuators, electric actuators with ISO adapters, hand levers or worm gear operators while maintaining a rigid connection between actuator stem and valve stem.

Bare stem high performance double flange butterfly valve construction

Connection type: double flange (raised face flanges both ends)

Structure: double eccentric (double offset) high performance disc

Size range: 2″ to 48″ (DN50 to DN1200)

Pressure rating: PN10, PN16, PN25, Class 150 and Class 300 (size and seat dependent)

Body material: WCB carbon steel, CF8/CF8M stainless steel or ductile iron options

Seat options: PTFE, RPTFE, EPDM, NBR or metal seated for high temperature

Operation: bare stem with ISO 5211 top flange; worm gear, pneumatic or electric actuator

Temperature range: -29°C to 425°C depending on seat and body material selection

Standards: API 609 Category B, EN 593, MSS SP-68, ISO 5211 mounting interface

End connection: ASME B16.5, EN 1092-1 or DIN flange facing per project specification

ISO 5211 bare stem and actuator compatibility

Process plants increasingly standardize on ISO 5211 actuator interfaces so maintenance teams can swap pneumatic, electric or manual gear units across valve populations without redesigning support brackets. The bare stem on this double flange butterfly valve provides a rigid, machined mounting surface elevated above the body so actuator stem alignment stays concentric with the valve stem, reducing side load on packing and improving cycle life. Confirm the complete mounting interface, shaft coupling, required torque and travel, and any bracket or adapter for the selected valve and operator; the ISO 5211 reference alone does not establish interchangeability.

For modulating duty, electric actuators with 4–20 mA control signals mount directly to the bare stem interface when torque and speed requirements match the valve sizing. For on-off isolation, spring-return pneumatic actuators or double-acting pneumatic units provide fast response in compressor stations, tank farms and utility headers. Worm gear operators with self-locking reduction remain the economical choice on buried vaults, elevated platforms or locations without instrument air, while still benefiting from the standardized stem connection if future automation is planned.

Double flange installation advantages

Unlike wafer designs that rely on pipeline gaskets and through-bolts for location, the double flange body carries its own raised flanges at both ends. That arrangement distributes pipeline loads through the valve body flanges, improves alignment during installation and simplifies removal for seat inspection or actuator replacement without disturbing the opposite pipeline joint. On larger diameters and higher pressure classes, flange-connected butterfly valves offer better resistance to bending moments from unsupported pipe spans, thermal expansion and water hammer events common in district energy and industrial cooling loops.

Face-to-face dimensions can be supplied per EN 558 Series 13, API 609 short pattern or project-specific requirements. Gasket selection follows flange rating and media: compressed fibre for general water, spiral wound for steam and hydrocarbon, or PTFE envelope for corrosive chemical services. Proper flange bolt tightening in a star pattern ensures even gasket compression and prevents seat distortion that could affect bubble-tight shut-off performance at test pressure.

Sealing performance and seat material selection

Resilient seats in PTFE, RPTFE, EPDM or NBR provide bubble-tight shut-off on water, air and neutral fluids at moderate temperature, achieving low leakage rates suitable for environmental and utility applications. Metal seated configurations with stainless or Stellite overlay on the disc and seat ring handle higher temperature, abrasive slurry and steam condensate where soft materials would extrude or degrade. The double eccentric motion minimizes seat contact during opening and closing, which is especially valuable on metal seated valves where repeated scraping would accelerate wear on hard-facing surfaces.

Factory testing typically includes shell hydrostatic test at 1.5 times rated pressure and seat closure test at 1.1 times rated pressure per API 598 or EN 12266-1, with leakage criteria matched to resilient or metal seat class. Trekre Valve documents material heat numbers, dimensional checks and functional torque measurements so EPC contractors and end users can trace each valve from purchase order to site commissioning.

Typical applications and industries

HVAC and district energy systems use bare stem high performance double flange butterfly valves on chilled water supply and return headers, cooling tower isolation and boiler bypass lines where ISO 5211 electric actuators integrate with building management systems. Water treatment plants specify flange butterfly valves on raw water intake, filter backwash and clear well isolation because double flange bodies simplify future actuator upgrades from manual gear to electric modulating control.

Petrochemical and chemical facilities deploy carbon steel or stainless bodies with PTFE seats on solvent, acid and caustic lines where corrosion resistance and fire-safe considerations must be evaluated against project specifications. Power plant auxiliary systems employ metal seated double flange butterfly valves on condenser cooling water, lube oil coolers and fuel oil transfer where temperature cycles and higher differential pressure demand robust hard-seating options. Pulp and paper, food processing and pharmaceutical utilities also benefit from the compact face-to-face envelope compared with gate valves, although the disc and shaft remain in the flow path when fully open. Confirm pressure loss from the selected valve’s flow data.

Product parameters summary

Model designation: high performance double flange butterfly valve, bare stem ISO 5211

Nominal diameter: DN50–DN1200 (2″–48″)

Pressure class: PN10 / PN16 / PN25; Class 150 / Class 300

Body: WCB, LCB, CF8, CF8M, CF3M or ductile iron

Disc: WCB, CF8, CF8M with optional stainless or nickel overlay

Stem: SS410, SS316 or SS304 with blow-out proof design

Seat: PTFE, RPTFE, EPDM, NBR, metal-to-metal

Top flange: ISO 5211 F07–F35 (size dependent)

Operator options: bare stem, worm gear, pneumatic actuator, electric actuator

Design standard: API 609, EN 593, MSS SP-68

Testing: API 598 / EN 12266-1 shell and seat closure

Installation and commissioning guidance

Install the valve with disc in the slightly open position to protect seat edges during flange bolt-up. Verify pipeline flange facing, bolt length and gasket type against the valve rating plate before lifting into line. After installation, cycle the valve fully open and closed under line pressure to confirm smooth operation and correct actuator direction if automated. For buried or vault installations, orient the bare stem upward or per actuator manufacturer clearance requirements, and provide a valve pit dimension that allows gear or actuator removal without cutting pipeline.

Lubricate worm gear operators per supplier instructions and inspect stem packing for leakage after thermal cycling. On electric or pneumatic installations, confirm control signal range, limit switch feedback and fail-safe position (open or closed) match the process safety analysis before energizing automation circuits.

Selection and ordering information

When requesting a bare stem high performance double flange butterfly valve, provide medium name and concentration, design temperature and pressure, nominal size, flange standard and facing, body and seat material preference, leakage class, flow direction if applicable, cycle frequency and intended operator type. Trekre Valve engineers size the disc and seat combination, confirm ISO 5211 top flange size for the selected actuator torque, and supply technical drawings, data sheets and material certificates aligned with project inspection and test plans.

Custom face-to-face lengths, extended bonnets for low temperature service, locking devices and position indication switches are available on request. Contact our sales team with pipeline specifications to receive a quotation for this double flange high performance butterfly valve from our Wuxi manufacturing facility.

Quality assurance from factory to site

Each valve undergoes dimensional inspection, non-destructive examination on critical welds where applicable, assembly torque verification and pressure testing before release. Packing lists include serial numbers linked to test certificates so site inspectors can reconcile delivered goods with purchase order line items. Trekre Valve maintains production equipment for machining, surface treatment and final assembly under documented quality procedures, supporting repeat orders with consistent performance on global industrial projects.