Worm Gear Ductile Iron FEP Lined Wafer Butterfly Valve D371F Overview
The worm gear ductile iron FEP lined wafer butterfly valve D371F is a manual quarter-turn isolation valve for corrosive pipelines where a ductile iron pressure shell and fluoroplastic wetted surfaces are required in a short face-to-face wafer envelope. Manufactured by Trekre & Fouten Valve at our Wuxi factory, this ductile iron lined butterfly valve combines a QT400 or QT450 body with factory-moulded FEP (F46) lining on the bore, disc faces and seat lands, plus a worm gear reduction drive for controlled 90-degree rotation. The wafer body installs between two companion flanges with through-bolts, saving axial space on acid transfer headers, alkali circulation loops, solvent recovery manifolds and wastewater treatment branches compared with double-flanged lined patterns.
Compared with cast steel WCB lined wafer butterfly valves on the same nominal size, ductile iron construction offers a practical pressure boundary for general chemical and utility services where the project material specification accepts nodular cast iron rather than carbon steel. Compared with stainless steel unlined wafer butterfly valves, the FEP lining isolates the flowing medium from all wetted metal surfaces so strong mineral acids, caustic solutions and mixed solvents can be handled within the temperature and chemical limits of the selected fluoroplastic grade. Compared with manual handle-operated lined wafer valves, the worm gear drive delivers the breakaway torque needed on larger bore sizes without sudden jerking that could damage lining edges at the seat line.
Construction and design features
Connection type: wafer (clamped between two flanges with through-bolts outside the body)
Structure: centerline concentric disc with two-piece ductile iron body and continuous FEP lining on bore, disc faces and seat lands
Model designation: D371F with optional fluoroplastic suffixes such as F46, F4 or PFA as confirmed on the purchase order
Size range: DN50 to DN1200 (NPS 2 to 48) for standard wafer patterns; intermediate and larger sizes per project drawing
Pressure rating: PN10 and PN16; ANSI Class 150 on matching flange pairs (size and lining grade dependent)
Body material: ductile iron QT400-15, QT450-10 or GGG50 with external coating for general industrial environments
Lining: FEP (F46) as the primary grade on this series; PTFE or PFA available when the process specification requires a different fluoroplastic
Disc and seat: steel or stainless skeleton with moulded fluoroplastic overlay integral to the body liner
Operation: worm gear handwheel with self-locking reduction
Temperature range: approximately -20°C to 150°C depending on lining material, thickness and continuous exposure conditions
Standards: GB/T 12238, HG/T lined valve specifications, API 609 Category A where applicable on the order
Ductile iron body with FEP corrosion barrier
Corrosive services attack valve internals from the bore outward while ambient humidity and wash-down chemicals can attack external cast surfaces on poorly specified valves. In this worm gear ductile iron FEP lined wafer butterfly valve D371F, the ductile iron body provides structural strength for flange bolt loads and impact resistance during handling at a lower material cost than all-stainless equivalents, while FEP forms a continuous barrier between the flowing fluid and all wetted metal surfaces including the body channel, disc faces and seat ring.
FEP (fluorinated ethylene propylene) offers broad chemical inertness against hydrochloric acid, sulphuric acid, phosphoric acid, caustic soda and many organic solvents at moderate temperature. Melt-processed FEP lining achieves uniform thickness at wafer gasket lands and flange transitions, reducing the risk of thin spots where gasket compression could expose metal at the seal line. Where the process specification names PTFE or PFA instead of FEP, Trekre & Fouten Valve can supply the corresponding lining grade on the same D371F wafer platform when chemical compatibility, permeation limits and temperature duty are confirmed on the datasheet.
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 hydrochloric acid dilution headers, sulphuric acid transfer lines, phosphoric acid circulation and solvent recovery manifolds where multiple valves sit in sequence. Compared with lug or double-flanged lined patterns, wafer bodies minimize material cost and simplify replacement when flange standards and pressure ratings remain unchanged on the line.
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, spiral wound or other types as specified. Tighten flange bolts in a star pattern to avoid seat distortion. Trekre & Fouten Valve confirms face-to-face dimension, bolt circle and gasket seating width against the flange standard on the data sheet before shipment from our China valve 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 FEP 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 values at rated differential pressure are stated on the project submittal with margin for aged gaskets and scale buildup.
Applicable working conditions and industries
This ductile iron FEP lined wafer butterfly valve suits isolation duty on pipelines carrying strong mineral acids, caustic solutions, chlorine compounds, organic solvents and mixed corrosive wastewater within the temperature and chemical limits of the FEP lining grade. Typical application areas include chemical processing, electroplating, pulp and paper bleaching circuits, metal pickling lines, pharmaceutical ingredient transfer where fluoroplastic wetted surfaces are specified, and municipal or industrial wastewater treatment where acid or alkali dosing lines require lined isolation valves.
The valve is intended for on-off isolation. Throttling duty is possible only where the disc geometry, seat construction and lining grade suit partial stroke service within the range defined on the project datasheet. Do not use this valve class on services that exceed the lining temperature limit, attack FEP chemically, or require metal-seated shutoff where fluoroplastic compression is insufficient for the stated leakage requirement.
Standards, inspection and delivery
Manufacturing follows GB/T 12238 butterfly valve requirements and HG/T lined valve specifications where applicable to the order. Shell and seat tests are performed per the agreed project protocol and manufacturer test procedure before shipment. Material certificates for body castings and lining batch records can be supplied when requested on the purchase order. Closure leakage is verified by seat test per the agreed standard; state the required test medium and acceptance criteria in the specification rather than assuming a universal rating across all sizes.
Each valve carries a nameplate stating model, nominal size, pressure class, body and lining materials, and manufacturing traceability reference. Trekre & Fouten Valve packages wafer lined butterfly valves with flange protectors and stem guards suitable for domestic and export shipment from Wuxi, Jiangsu, China.
Product parameters summary
Valve type: worm gear ductile iron FEP lined wafer butterfly valve D371F
End connection: wafer (clamped between flanges)
Body: ductile iron QT400 / QT450 / GGG50
Lining: FEP (F46); PTFE or PFA optional per order
Disc: steel or stainless skeleton with fluoroplastic overlay
Seat: moulded fluoroplastic integral with body liner
Actuator: worm gear handwheel, self-locking
Size: DN50–DN1200 (2″–48″)
Pressure: PN10 / PN16; Class 150
Temperature: approximately -20°C to +150°C (lining dependent)
Applicable media: hydrochloric acid, sulphuric acid, alkali solutions, solvents, chlorine compounds and corrosive process fluids within lining limits
Manufacturing: Trekre & Fouten Valve, Wuxi, China
Selection notes
Confirm nominal diameter, pressure class, flange standard and gasket type before ordering. State the exact medium composition, concentration, temperature and any cleaning or steam-out procedure because fluoroplastic limits are not interchangeable across grades. Specify whether FEP, PTFE or PFA lining is required and whether the disc skeleton must be stainless rather than carbon steel for trace metal sensitivity. Request face-to-face length, bolt circle and operating torque table for the stated differential pressure when the valve sits on a critical isolation tag.
When the line also requires electric or pneumatic operation, review the Trekre & Fouten lined butterfly valve range for actuated variants on lug or double-flange connections. The manual D371F wafer pattern remains the baseline for chemical headers where handwheel operation and compact length are sufficient.
Installation and maintenance guidance
Install the wafer valve between companion flanges with gaskets suited to the medium and flange class. Tighten through-bolts in a cross pattern so the wafer faces load evenly without bending the body. Keep the disc slightly open during initial bolt-up, then close and re-torque after the line is pressurized if the procedure allows. During commissioning, cycle the valve several times under line pressure and inspect for external leakage at the stem packing gland.
Periodically inspect seat contact and stem packing during scheduled outages. Avoid operating the valve against closed downstream block valves that could trap pressure and increase seat load beyond the lining design margin. Replace packing when external leakage appears during thermal cycling. Do not use metal tools on lined disc faces or bore surfaces during maintenance.
Comparison with adjacent designs
Cast steel WCB lined wafer butterfly valves such as the D371F46 series use a carbon steel shell when the material specification requires WCB rather than ductile iron. Stainless steel unlined wafer butterfly valves suit clean water and air but do not provide fluoroplastic isolation for strong acids. Double-flange lined butterfly valves add bolting flexibility for end-of-line removal but increase face-to-face length and weight compared with wafer patterns. Pneumatic or electric lined wafer valves add remote operation where plant air or power is available but require separate actuator sizing against lined breakaway torque. The worm gear ductile iron FEP lined wafer butterfly valve D371F fits mid-to-large bore corrosive headers where ductile iron economy, FEP chemical barrier, compact wafer length and manual worm gear operation are all specified on the same valve tag.
This worm gear ductile iron FEP lined wafer butterfly valve extends the Trekre & Fouten lined butterfly valve range for plant owners who need manual isolation on wafer connections with a ductile iron shell and FEP wetted surfaces. Contact our sales team with flange details, medium data and lining grade requirement for quotation and delivery schedule from our China valve manufacturing facility.