The D671X pneumatic wafer soft seal butterfly valve is a quarter-turn isolation valve for clean water, air, and low-abrasive industrial fluids where a short face-to-face length and fast automated cycling matter. Trekre Valve builds this concentric wafer butterfly valve with ductile iron, carbon steel, or stainless steel bodies, a stainless or ductile iron disc working against an elastomer seat, and a pneumatic actuator sized for the stated differential pressure. Fouten Valve application support can confirm body alloy, seat polymer, bolt pattern, and accessory list against the pipeline flange standard before release from our Wuxi factory.
Table of Contents
Overview and wafer connection
Wafer butterfly valves install between two pipeline flanges. Through-bolts pass outside the valve body and compress gaskets on both sides of the short wafer shell. That layout saves axial space compared with double-flanged bodies and suits retrofit tie-ins on crowded pipe racks, HVAC headers, and packaged skids. The D671X designation identifies a soft-seated, concentric disc geometry with pneumatic operation; suffix letters on the order document indicate pressure class, body material, and seat polymer when a project requires a specific code such as D671X-10Q or D671X-16P.
Confirm flange drilling, facing, gasket type, and bolt length against the approved drawing. Face-to-face length follows wafer tables aligned with GB/T 12238 and API 609 Category A patterns for the nominated size and pressure class. Mixed-standard jobs should not assume interchangeability from nominal diameter alone.
Structure, disc, and soft seal
The valve assembly includes a two-piece or one-piece wafer body, disc, elastomer seat ring, stem, upper and lower bushings, packing gland, and actuator coupling. In the concentric soft-seal layout, the stem axis passes through the disc center. Closing torque presses the disc edge into the resilient seat to build sealing stress. Opening rotation lifts the disc away from the seat line early in the stroke, which limits scrubbing on clean media services.
Seat options commonly include EPDM for water and moderate-temperature air, NBR for oil-tolerant water and compressed air, silicone for food-grade water where the material certificate matches the duty, and FKM where higher temperature or selected chemicals appear in the fluid analysis. Shutoff acceptance follows the test method named on the purchase order; Trekre documents seat results on the factory test sheet rather than quoting a universal leakage class in place of that record.
The disc is typically stainless steel 304 or 316 for corrosion resistance on the wetted face, or ductile iron with a stainless overlay when cost and weight targets favor a composite plate. The stem uses stainless steel with anti-blowout retention in the lower bearing pocket. Self-lubricating bushings reduce friction so pneumatic break torque stays within the selected actuator envelope after packing adjustment.
Pneumatic actuator, air supply, and accessories
Standard supply pairs the wafer body with a rack-and-pinion or scotch-yoke pneumatic actuator chosen from break and run torque at maximum differential pressure, plus an agreed safety factor. Supply air is normally filtered and dried near 0.4 to 0.6 MPa unless the actuator nameplate specifies another band. Double-acting actuators use air on both sides for open and close. Single-acting units use springs to fail closed or fail open as defined in the cause-and-effect chart.
Common accessories include a filter-regulator-lubricator set, solenoid valves for remote commands, limit switches for open and closed feedback, positioners when modulating flow is approved for the disc design, and quick exhaust fittings where cycle time limits appear in the specification. Explosion-proof solenoid coils and stainless steel air tubing are available when area classification drawings require them. Manual override devices can be quoted when maintenance rules demand local operation during air loss.
The actuator mounting interface on applicable sizes follows ISO 5211 dimensions so an electric or gear operator can replace the pneumatic head later if the plant adds automation. Any change in operator type requires a fresh torque review because break torque rises when seats age or when line pressure increases above the original design point.
Body materials and pressure-temperature limits
Body castings are offered in ductile iron QT450-10 or QT400-15 for municipal and building services, carbon steel WCB for industrial water and air, and stainless CF8 or CF8M when chloride fogging or mild chemical exposure affects external surfaces as well as the bore. Pressure ratings commonly include PN10 and PN16, with Class 150 flange pairs on ANSI projects. Nominal sizes from DN50 through DN1200 appear on standard price lists; confirm casting availability and actuator size for extreme diameters at quotation stage.
Temperature limits depend on the seat polymer and packing set. EPDM seats often serve from roughly −30 °C to +120 °C in water duty when the fluid chemistry matches the rubber grade. NBR seats typically serve lower temperature compressed air and oily water within the band stated on the material data sheet. Do not exceed the combined pressure-temperature table for the complete valve assembly; the body rating alone does not define seat life at the upper temperature edge.
Product parameters
| Item | Specification |
|---|---|
| Model | D671X pneumatic wafer soft seal butterfly valve |
| Structure | Wafer, concentric soft seat |
| Size range | DN50 – DN1200 (NPS 2 – 48) |
| Pressure class | PN10, PN16; Class 150 as specified |
| Body material | Ductile iron, WCB, CF8, CF8M |
| Disc / seat | Stainless or ductile iron disc; EPDM, NBR, silicone, or FKM seat |
| Operation | Pneumatic actuator; solenoid and limit switches optional |
| Design reference | GB/T 12238, API 609 Category A, project flange standard |
| Test | Shell and seat per agreed standard; leakage per test report |
Table values show common optional combinations. Final body, seat, actuator, and flange details are confirmed on the Trekre or Fouten technical agreement, nameplate, and test report for the ordered tag number.
Typical applications
Specify the D671X pneumatic wafer soft seal butterfly valve on municipal pump discharge isolation, building chilled and hot water branches, cooling tower makeup lines, food-grade water transfer where elastomer certificates match the hygiene plan, paper mill white water zones, and general plant air headers where soft seats and fast pneumatic cycling are appropriate. The compact wafer body fits equipment packages that must stay within a defined module length.
Compared with manual worm gear wafer valves on the same line size, pneumatic drive shortens cycle time and simplifies linkage to distributed control systems. Compared with metal-seated triple-offset wafer valves, the soft seat targets lower torque and bubble-tight water shutoff rather than high-temperature dry gas duty. Media with sharp solids, high velocity slurry, or sustained throttling beyond the manufacturer partial-open limit should be reviewed before selecting a concentric soft-seal disc.
Installation, commissioning, and service
Install the valve with the disc slightly open to protect the seat edges while flange bolts are tightened in a cross pattern. Use gaskets compatible with the fluid and flange facing. Align pipe ends so wafer lugs are not twisted by bolt pull-in. Connect dry, filtered air, verify solenoid voltage and fail direction, then stroke the valve locally before applying process pressure. Record open and closed limit switch feedback against the control system tags.
Periodic inspection should cover seat faces for cuts, stem packing for weeping, and actuator lubrication per the actuator manual. Replace seat rings during planned outages when closure leakage exceeds the operating procedure allowance. Store spare valves with the disc marginally open to avoid long-term seat compression set in warehouse stock.
Selection questions
What data should I send for a D671X quotation?
Provide medium composition, design pressure and temperature, nominal size, flange standard and facing, required fail action, control voltage, and any explosion-protection class. Trekre Valve engineers return a bill of materials with body and seat materials, actuator model, and flange bolt guidance.
Can the valve be used for throttling service?
Some concentric soft-seal discs tolerate partial opening for balanced flows, but cavitation, noise, and seat wear rise at high pressure drops. Share the flow curve and differential pressure so the team can confirm whether a lined or high-performance offset design fits better.
Is welding allowed on the wafer body?
Do not weld the valve into the pipeline. Wafer bodies rely on flange gaskets and through-bolts; welding heat damages elastomer seats and voids standard warranty terms for soft-seal products.