The high-performance double-eccentric wafer butterfly valve with bare stem is a quarter-turn isolation valve intended for compact installation between compatible pipeline flanges. Manufactured by Trekre Valve, it uses a machined bare stem and ISO 5211 actuator mounting interface. Actuator attachment requires verification of flange size, shaft coupling geometry, torque capacity, angular travel and any adapter or gearbox needed for the selected drive. The wafer body fits between companion flanges using the specified through-bolting arrangement.
Also known as a high performance clamp butterfly valve with smooth stem, the design combines wafer-type end connections with double-offset camming action. The disc rotation axis is offset from the body centreline and from the seal plane, so the disc lifts away from the seat during the first degrees of opening rather than scraping across the sealing surface. That geometry reduces seat wear, lowers breakaway torque and extends service life on frequently cycled isolation points compared with concentric rubber-lined wafer valves on identical nominal sizes.
High performance wafer butterfly valve construction
Connection type: wafer (clamp / between-flange pattern)
Structure: double eccentric (double offset) high performance disc
Size range: 2″ to 20″ (DN50 to DN500)
Pressure rating: ANSI Class 150, EN PN16 and equivalent (size and seat dependent)
Body material: WCB carbon steel, CF8/CF8M stainless steel 304/316
Seat options: PTFE, RPTFE, EPDM, NBR or metal seated for elevated temperature
Operation: smooth bare stem with ISO 5211 interface; 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-67, ISO 5211 mounting interface
ISO 5211 smooth bare stem and actuator compatibility
The bare-stem configuration provides an exposed valve shaft end for connection to a suitable quarter-turn operating device or gearbox. ISO 5211 standardizes relevant part-turn actuator attachment interfaces, but does not make all actuator models directly interchangeable. The selected drive must match the mounting flange, coupling dimensions, output torque, travel and mounting arrangement. A multi-turn actuator requires an appropriate mechanical conversion or gearbox arrangement before it can operate a quarter-turn butterfly valve.
Because no operating device is supplied as standard, the valve ships ready for field assembly of the selected actuator package. Project engineers can specify handle levers for small bore manual isolation, worm gear boxes for buried or hard-to-reach locations, pneumatic double-acting or spring-return units for fast shut-off, or electric actuators with position feedback for remote SCADA integration. Actuator sizing must account for differential pressure, media characteristics, required fail position and operating cycle frequency at the design stage.
Double eccentric disc sealing performance
Double eccentric geometry positions the disc shaft axis behind the body centreline and offset from the seal ring plane. At closed position the disc edge presses against the seat with controlled contact pressure. During opening the disc immediately clears the seat profile, eliminating the continuous rubbing action typical of concentric designs. Confirm the required closure leakage and cycling duty against the selected seat configuration and applicable test evidence.
Metal-seated and resilient-seated double-eccentric butterfly valves use different seat constructions and have different pressure-temperature and leakage characteristics. Hard-facing options may be specified where the selected service and valve design require improved resistance to wear. Bidirectional shut-off capability must be established for the exact seat configuration, differential pressure and test conditions; installation must follow the documented flow-direction and orientation requirements of the supplied valve.
Wafer installation and pipeline integration
Wafer butterfly valves install between two companion flanges using through-bolts that pass outside the valve body. This arrangement minimizes axial length in tight mechanical rooms, pump skids, filter housings and packaged equipment where every millimetre of face-to-face dimension matters. Lug-type alternatives require longer bolts and separate upstream/downstream flange sets; double-flanged valves add further length and weight. For new construction and retrofit projects targeting space savings, the wafer high performance butterfly valve remains the preferred structural form below approximately DN500.
Correct gasket selection and bolt torque sequence are essential for reliable wafer installation. Full-face or ring-type gaskets must match the flange standard—ANSI B16.5, EN 1092-1 or JIS B2220—and the bolting pattern of the companion flanges. Over-torquing can distort the wafer body and impair seat contact; under-torquing risks external leakage at the flange joint. Trekre Valve recommends following the installation torque values published for the specific flange class and gasket material combination used on site.
Material selection for body and seat
WCB carbon steel bodies suit general industrial water, steam, air and hydrocarbon services within the temperature limits of the selected seat material. CF8 (304) and CF8M (316) stainless steel bodies address corrosive chemical environments, food-grade washdown areas and offshore atmospheres where chloride exposure accelerates rust on carbon steel. Body material choice should align with pipeline specification, welding procedure qualification and any NACE or low-temperature impact requirements stated in the purchase order.
PTFE and RPTFE seats provide excellent chemical resistance and low friction for modulating as well as on-off duties. EPDM and NBR resilient seats handle municipal water, HVAC chilled water and compressed air at moderate temperatures. Metal seats with Stellite or similar hard-facing support high-temperature steam, thermal oil and abrasive slurry applications where soft materials cannot maintain sealing integrity over the project design life.
Typical applications and industry sectors
High performance wafer butterfly valves with smooth bare stems appear across building services, district energy networks, wastewater treatment plants, chemical batch reactors, power plant auxiliary systems and general manufacturing utility headers. The compact wafer form fits inside valve pits with limited headroom, on rooftop HVAC risers and inside OEM equipment skids where the valve supplier must deliver actuator-ready bare stem units for factory assembly.
Water treatment facilities use these valves on filter backwash lines, clarifier outlets and chemical dosing headers where reliable isolation and actuator standardization reduce spare-part inventory. Chemical plants specify stainless steel bodies with PTFE seats on solvent transfer lines, while power stations deploy metal-seated variants on balanced condenser cooling water circuits and auxiliary steam systems.
Inspection, testing and quality assurance
Each valve undergoes shell hydrostatic test and seat leakage test per applicable standard before shipment. Trekre Valve maintains ultrasonic thickness gauging, chemical analysis and dimensional inspection equipment at the Wuxi manufacturing facility. Material certificates, test reports and actuator mounting dimension drawings are available on request to support project documentation packages and third-party inspection requirements.
Pre-shipment verification of ISO 5211 flange bolt circle, stem square or key dimensions and valve tag data against the purchase order prevents costly field rework on automated lines. For critical services, additional NDE such as radiography on welds or PMI on stainless components can be incorporated into the production scope when specified at order entry.
Selection checklist for procurement engineers
Confirm nominal size, flange standard, pressure class and face-to-face dimension against piping isometrics before ordering. State the medium composition, design temperature, design pressure, required leakage class and expected cycle frequency. Specify actuator type, fail position, control signal and enclosure rating when ordering an assembled unit, or confirm bare stem only when the actuator is supplied separately. Indicate any special requirements such as extended packing, locking device, position indicator or corrosion-resistant coating for buried or coastal installations.
Trekre Valve engineering team supports selection reviews, actuator sizing calculations and customized material configurations for project-specific specifications. Contact the factory with complete operating data to receive a technical proposal aligned with API 609, EN 593 or project-specific valve datasheets.
Product parameters summary
Type: High performance wafer butterfly valve, smooth bare stem, double eccentric
End connection: Wafer (between-flange)
Nominal diameter: DN50–DN500 (2″–20″)
Pressure: Class 150 / PN16
Body: WCB, CF8, CF8M
Seat: PTFE, RPTFE, EPDM, NBR, metal
Stem: Smooth bare stem, ISO 5211 top flange
Actuation: Worm gear, pneumatic, electric (field mounted)
Standards: API 609, EN 593, ISO 5211
Frequently Asked Questions
Can I mount a multi-turn actuator directly on this bare-stem butterfly valve?
The page identifies a quarter-turn valve and explains that a multi-turn drive needs an appropriate conversion or gearbox arrangement. Provide the proposed drive details and ask for confirmation of the complete coupling, travel and torque arrangement.
What should I check if I want to reuse my existing quarter-turn actuator?
Compare the mounting flange, shaft coupling, available output torque, angular travel and installed clearance with the selected valve data. Matching an interface designation alone does not establish compatibility.
Will the wafer body clear the bore of my existing pipe and flanges?
Send the actual pipe bore, flange details and required valve size. Request the selected valve drawing and disc-clearance check before installation, together with the specified fastener and assembly requirements.