Cast Steel PTFE Lined Double Flange Worm Gear Butterfly Valve

The cast steel PTFE lined double flange worm gear butterfly valve is engineered for pipelines carrying aggressive acids, alkalis, solvents and other corrosive fluids where a bare metal butterfly valve would fail within weeks. Manufactured by Trekre Valve, this double flange butterfly valve combines a WCB or stainless steel pressure boundary with a continuous fluoroplastic lining across the body bore, disc faces and seat zone, isolating process media from the cast structure while retaining the strength and flange connectivity required on chemical, pharmaceutical and wastewater projects.

Double-flanged end connections provide integral flange joints for installation between compatible pipeline flanges. The rotating disc remains within the valve flow passage even when fully open, so this conventional butterfly-valve configuration must not be assumed suitable for the passage of pipeline pigs. The worm gear operator provides mechanical advantage for manual operation on larger diameters, making the valve suitable for isolation duties within the verified pressure, temperature and lining limits of the selected configuration.

PTFE lined double flange butterfly valve construction

Connection type: double flange (FF or RF) per ANSI, DIN, JIS or GB standards

Structure: centerline disc with split or two-piece cast steel body and moulded fluoroplastic liner

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

Pressure rating: PN6, PN10, PN16 and Class 150 (size and lining dependent)

Body material: WCB carbon steel, optional CF8/CF8M for external corrosion resistance

Lining options: PTFE, PFA, FEP or PO selected for media compatibility and permeation limits

Operation: worm gear manual standard; electric actuator or pneumatic actuator on ISO 5211 top flange

Temperature range: -29°C to 150°C depending on lining grade and continuous exposure

Standards: GB/T 12238, API 609 Category A, HG/T 3704 lined valve specifications

Fluoroplastic lining technology and corrosion barrier

Corrosive services attack valve bodies from the inside out. In a cast steel PTFE lined double flange butterfly valve, the fluoropolymer layer forms a continuous barrier between the flowing medium and all wetted steel surfaces including the body channel, disc edges and seat lands. PTFE provides broad chemical inertness against strong mineral acids and caustic solutions at moderate temperatures. PFA and FEP variants offer improved permeation resistance and smoother surfaces for sticky polymers or ultra-pure pharmaceutical fluids where extractables must be minimised.

The lining is moulded or bonded under controlled factory conditions rather than applied as a field wrap, ensuring uniform thickness at flange transitions where differential expansion during thermal cycling could otherwise stress a thin coating. Disc and body linings are profiled so the disc seal line compresses against the lined seat without exposing bare metal, maintaining bubble-tight shut-off on hydrochloric acid dilution, sodium hydroxide circulation, chlorine dioxide bleach and mixed solvent recovery lines typical in chemical plants.

External environmental corrosion is addressed separately through paint systems on the WCB shell or through CF8/CF8M body selection for coastal, offshore or outdoor tank dike installations. The double flange format keeps flange gasket faces outside the lined bore, allowing standard spiral-wound or PTFE envelope gaskets while the valve interior remains fully protected by fluoroplastic.

Double flange connection advantages over wafer designs

Wafer and double-flanged butterfly valves use different body and flange-bolting arrangements. A double-flanged body provides integral flange connections, but its connection style alone does not establish a dead-end pressure rating or permit removal of downstream piping while the upstream side remains pressurized. Any such service requires a documented rating and an approved installation procedure for the exact valve size and configuration. Replacement dimensions must be checked against the actual face-to-face and flange standards of the existing piping.

On larger bore chemical headers, double flange connectivity distributes pipe loads more evenly around the lined body, reducing the risk of liner pinching that can occur if wafer bodies are overtightened on one side. Trekre supplies drilling patterns for ASME B16.5 Class 150, EN 1092 PN10/PN16 and GB/T 9113 so the valve drops into existing flange sets without re-drilling on most retrofit projects.

Worm gear operation for lined butterfly valves

Fluoroplastic linings increase disc-to-seat friction compared with bare metal hard-seated designs, particularly when media deposit thin films on the seal line. A worm gear operator applies high mechanical advantage so operators can open and close the valve without shock loading the liner at the end of stroke. Self-locking worm gearing holds the disc position under flow-induced torque, which matters on throttled lines where partial opening controls fill rate into batch reactors or neutralisation tanks.

The gear housing mounts on a raised ISO 5211 pad above the lined bonnet, keeping lubricated steel components outside the wetted path. Position indicators and optional mechanical stops help commissioning teams verify open and closed limits without relying on guesswork through viscous or coloured process fluids. Where automation is planned later, the same worm gear pad accepts electric multi-turn actuators or pneumatic scotch-yoke units with bracket adapters, avoiding valve body changes when control philosophy evolves from manual to remote operation.

Product parameters summary

Structure: double flanged cast steel body with full PTFE/PFA/FEP lining

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

Pressure class: PN6 / PN10 / PN16 / 150LB

Body: WCB cast carbon steel, optional CF8/CF8M

Lining: PTFE, PFA, FEP or PO (media dependent)

Disc: PTFE-lined stainless steel or fully moulded lined disc

Seat: integral fluoroplastic lining, bubble-tight shut-off

Operation: worm gear manual (standard), electric or pneumatic optional

Design standard: GB/T 12238, API 609, HG/T 3704 (lined valves)

End connection: double flange RF per ASME B16.5, EN 1092, GB/T 9113

Temperature range: -29°C to 150°C (lining limited)

Testing: shell and seat test per API 598 / GB/T 13927

Typical applications in corrosive industries

Sulphuric acid and hydrochloric acid dilution, distribution and tail gas scrubber bypass

Caustic soda, sodium hypochlorite and chlorine alkali plant transfer lines

Pharmaceutical ingredient reactors, CIP return headers and solvent recovery manifolds

Electroplating and surface treatment baths with mixed acid and metal salt solutions

Municipal and industrial wastewater with chemical dosing and sludge acidification

Pulp bleaching, paper stock and white liquor circulation where chloride levels attack bare steel

Advantages of Trekre lined double flange butterfly valves

Full fluoroplastic wetted path protects cast steel body investment on aggressive media without switching to expensive solid alloy valves for every branch line.

Double-flanged construction provides integral flange connections for installation and maintenance planning. Dead-end or single-flange use requires a separate documented rating for the exact valve configuration.

Worm gear drive reduces operator effort and provides self-locking position hold on throttled corrosive services.

ISO 5211 mounting pad enables electric or pneumatic upgrade without replacing the lined valve body.

Factory pressure testing and lining integrity checks support owner inspection on chemical EPC and pharmaceutical validation packages.

Installation and maintenance guidance

Install the cast steel PTFE lined double flange worm gear butterfly valve with the disc slightly open to protect the lining from pinching during flange bolt tightening. Use flange gaskets compatible with the chemical service; PTFE envelope or filled PTFE gaskets are common on lined systems. Tighten bolts in a star pattern to avoid distorting the lined body or creating high spots on the seat line. Verify that pipeline stress after welding is not transferred into the valve flanges, which can crack brittle linings at the flange radius.

During commissioning, cycle the valve slowly through full stroke several times with compatible fluid or clean water to seat the liner evenly. Avoid rapid hammering of the handwheel on closing, which can indent soft fluoroplastic. Inspect stem packing for leakage after the first thermal cycle; lined valves often operate at moderate temperature where packing adjustment is infrequent but should not be ignored on toxic media.

Maintenance intervals depend on media abrasiveness and cycle count. Plan liner inspection during scheduled outages if shut-off performance declines or if visible swelling suggests permeation of lining material. Confirm the replacement parts, required valve removal and disassembly sequence, and maintenance access from the approved drawing and instructions for the supplied valve.

Selection and ordering information

When requesting a quotation, confirm nominal diameter, pressure class, flange standard and drilling table, body material, exact media composition with temperature and concentration, preferred lining material (PTFE, PFA or FEP), operation type and any actuator or position feedback requirements. Our engineering team can recommend the optimal cast steel PTFE lined double flange worm gear butterfly valve configuration for greenfield chemical plants, pharmaceutical suites or replacement of failed unlined valves on acid headers.

As a professional China valve manufacturer, Trekre maintains production, inspection and spare-part support for lined butterfly valves from stock sizes through engineered builds. Contact us for dimensional drawings, torque data, lining chemical compatibility notes and delivery schedules aligned with your turnaround or validation window.

Quality assurance from factory to site

Each cast steel PTFE lined double flange worm gear butterfly valve undergoes material traceability review, dimensional inspection against approved drawings, lining adhesion and spark testing where applicable, and shell and seat pressure testing before release. Factory test reports, lining material certificates and installation manuals accompany shipments to support third-party witness requirements on international projects.

Our Wuxi assembly centre integrates body machining, lining moulding, gearbox pairing and protective packaging for domestic and export delivery. Lead times for common carbon steel lined sizes remain competitive, while large diameters and special lining grades are scheduled with milestone updates for chemical expansion and environmental upgrade programmes.