Worm Gear Stainless Steel Lined PTFE Wafer Butterfly Valve PFA FEP Overview
The worm gear stainless steel lined PTFE wafer butterfly valve PFA FEP is a manual isolation valve for corrosive process lines where a compact face-to-face dimension and fluoroplastic wetted surfaces are required together. Manufactured by Trekre Valve, this stainless steel lined butterfly valve combines a CF8 or CF8M pressure shell with a moulded PTFE, PFA or FEP barrier on the bore, disc faces and seat lands, plus a worm gear reduction drive for controlled 90-degree rotation. The wafer body clamps between two pipeline flanges, saving axial space compared with double-flanged patterns on crowded header runs, pump skids and chemical dosing manifolds.
Construction and design features
Connection type: wafer (clamped between two flanges; single-clamp variants available on request)
Structure: centerline disc with two-piece stainless steel body and continuous fluoroplastic lining on bore, disc faces and seat lands
Size range: 2″ to 24″ (DN50 to DN600) for standard wafer patterns; larger sizes available on project request
Pressure rating: PN10 and PN16; Class 150 on ANSI flange pairs (size and lining grade dependent)
Body material: stainless steel CF8 (304) or CF8M (316-type) cast body with external passivation or paint system for general industrial environments
Lining options: PTFE, PFA or FEP selected for media compatibility, permeation resistance and temperature duty
Operation: worm gear handwheel with self-locking reduction for controlled opening and closing torque
Temperature range: -29°C to 180°C depending on lining material and continuous exposure conditions
Standards: GB/T 12238, HG/T 3704 lined valve specifications, API 609 Category A where applicable
Stainless steel body with dual corrosion resistance
Corrosive services attack valve internals from the bore outward while ambient humidity, wash-down chemicals or coastal atmospheres can attack external steel surfaces on poorly specified valves. In this worm gear stainless steel lined PTFE wafer butterfly valve, the CF8 or CF8M body resists external oxidation and provides structural strength for flange bolt loads, while PTFE, PFA or FEP forms a continuous barrier between the flowing fluid and all wetted steel surfaces including the body channel, disc faces and seat ring.
PTFE offers broad chemical inertness against strong mineral acids, caustic solutions and mixed solvents at moderate temperature. PFA provides improved permeation resistance and smoother surfaces for sticky polymers, chlorinated compounds or ultra-pure pharmaceutical fluids where trace metal contamination must be avoided. FEP suits applications where melt-processed lining uniformity at flange transitions and wafer body edges is critical. The lining is moulded under factory conditions rather than applied as a field wrap, ensuring uniform thickness where flange gaskets compress against the wafer faces.
Wafer installation and pipeline space savings
Wafer butterfly valves install between two pipeline flanges with through-bolts that pass outside the valve body. The short face-to-face length reduces overall piping envelope on chemical transfer headers, FGD recycle lines and wastewater treatment galleries where multiple valves sit in sequence. Compared with lug or double-flanged patterns, wafer bodies minimize material cost and simplify replacement when flange standards and pressure ratings remain unchanged.
Install the valve with the disc slightly open to protect lined seat edges during flange bolt-up. Use full-length bolts sized for the flange rating and gaskets compatible with the chemical service — PTFE envelope or spiral wound as specified. Tighten flange bolts in a star pattern to avoid seat distortion. Trekre Valve confirms face-to-face dimension, bolt circle and gasket seating width against the flange standard on the data sheet before shipment from our Wuxi manufacturing facility.
Worm gear drive and operating torque
Large bore lined butterfly valves require significant breakaway torque to unseat the fluoroplastic seal line after periods in the closed position, especially when line pressure or media deposits add friction. A worm gear reduction mounted on the stem converts moderate handwheel effort into the torque needed to rotate the disc through 90 degrees without sudden jerking that could damage the lining at the seat edge.
The self-locking worm gear prevents back-driving from line torque on partially open valves in high-velocity services. Handwheel direction, open and closed position stops, and optional mechanical position indicator are factory-set and documented on the nameplate. For buried or hard-to-reach installations, extension stem and floor box options can be quoted separately. Operating torque tables in the project submittal include breakaway and running values at rated differential pressure with margin for aged gaskets and scale buildup.
Fluoroplastic lining selection for PFA and FEP duty
When the process specification names PFA or FEP rather than standard PTFE, the choice usually reflects temperature margin, permeation limits or surface finish requirements rather than a generic corrosion label. PFA-lined wafer butterfly valves handle hot corrosive condensate, mixed acid streams and chlorinated solvents where PTFE permeation rates would exceed project limits over multi-year service. FEP lining suits lower-temperature acid transfer and caustic circulation where melt-processed uniformity at the wafer gasket lands simplifies field assembly.
The disc seal line engages the lined seat without exposing bare metal, maintaining shut-off performance per project leakage criteria documented in the test report. Do not use the valve for throttling service beyond the partial-open limits defined on the data sheet — lined centerline discs are intended primarily for on-off isolation.
Typical applications and industry sectors
Chemical plants deploy worm gear stainless steel lined PTFE wafer butterfly valves on sulphuric acid transfer, hydrochloric acid dilution headers, phosphoric acid circulation and solvent recovery manifolds where corrosive fluids demand fluoroplastic protection in a compact wafer envelope. Chlor-alkali facilities isolate brine, caustic and chlorine compound streams on horizontal runs where stainless external surfaces resist chloride fogging in coastal or indoor humid environments.
Water and wastewater treatment facilities use lined wafer butterfly valves on sodium hypochlorite dosing, ferric chloride feed and polymer injection headers. Pharmaceutical and food-grade installations specify CF8M bodies with PFA lining where external wash-down and internal product contact both require corrosion-resistant materials. For power plant FGD scrubber recycle isolation, pulp bleaching stage shutoff and metal finishing acid rinse lines, confirm compatibility of the complete wetted-material configuration with the actual medium and operating conditions. No comparative corrosion lifetime is established here for an unspecified bare steel valve.
Installation, maintenance and inspection
After installation, cycle the valve fully open and closed under no-flow conditions to verify smooth worm gear operation and correct disc orientation. Introduce process fluid gradually and inspect flange joints and stem packing for leakage. Periodic maintenance includes handwheel lubrication per site procedure, stem packing adjustment if needed, and visual inspection of external surfaces where wash-down chemicals are used.
Store spare lined wafer valves with the disc in the slightly open position to avoid permanent seat compression set during long warehouse periods. Before returning a valve to service after extended storage, inspect gasket faces for lining damage at bolt holes and verify worm gear backlash remains within factory tolerance.
Selection and ordering information
Stainless-steel material options include 304 and 316L. Specify the required component materials and exact grades in the quotation and order documents; confirm the actual casting grade rather than treating a cast designation and a wrought grade as automatically interchangeable. Also provide medium name and concentration, design temperature and pressure, nominal size, flange standard (ANSI, DIN, JIS or GB), lining material preference (PTFE, PFA or FEP), and any extension stem or gear box orientation requirements. Confirm whether the installation requires dead-end service rating on one flange side — wafer valves generally rely on both flanges for retention. Trekre Valve factory tests each lined butterfly valve for seat leakage and handwheel operation prior to shipment.
Product parameters summary
Valve type: worm gear stainless steel lined PTFE wafer butterfly valve PFA FEP
End connection: wafer (clamped between flanges)
Body: stainless steel CF8 (304) or CF8M (316-type)
Lining: PTFE, PFA, FEP
Disc: lined stainless steel with fluoroplastic overlay
Seat: moulded fluoroplastic integral with body liner
Actuator: worm gear handwheel, self-locking
Size: DN50–DN600 (2″–24″)
Pressure: PN10 / PN16; Class 150
Temperature: -29°C to +180°C (lining dependent)
Applicable media: acids, alkalis, solvents, chlorine compounds, wastewater and corrosive process fluids
Manufacturing: Trekre Valve, Wuxi, China
Frequently Asked Questions
Why should I specify the metal shell material if the valve is lined?
The shell and lining are separate parts of the selected assembly. State the project’s body-material requirements and external exposure as well as the process conditions, and request confirmation of the quoted stainless-steel shell and wetted barrier.
Can I select the lining from the highest temperature shown for the series?
Request the allowable conditions of the exact lining, seat, seals and body combination. Provide the actual process temperature, pressure and medium; a series-level figure does not apply automatically to every listed lining option.
Can this stainless-steel wafer valve replace a double-flanged lined valve?
Compare the actual face-to-face space, flange arrangement, fasteners and operating envelope using the selected drawing. Different body connections should not be treated as dimensionally interchangeable without review.