Two Way Hard to Hard All Metal Hard Sealed Butterfly Valve Double Flange

The two way hard to hard all metal hard sealed butterfly valve is a double-flange quarter-turn isolation valve engineered for extreme temperature, pressure and abrasive media where soft seats, graphite layers or PTFE interlayers would erode under high-velocity flow. Manufactured by Trekre Valve in Wuxi, China, this all-metal seated butterfly valve uses a fully metal sealing ring on both the disc and seat contact surfaces — hard against hard — without non-metallic sandwich layers such as polytetrafluoroethylene, graphite or rubber-asbestos board. The design addresses common weaknesses of conventional multi-layer triple-offset hard-sealed butterfly valves, including interlayer wash-out, thermal delamination and loss of seal integrity when the valve operates partially open under flashing or cavitation conditions.

Structure and sealing principle. The valve body follows a double-flange pattern suitable for pipeline installation with raised-face or flat-face companion flanges per ASME B16.5, EN 1092-1 or GB/T 9113. The disc rotates on a sturdy stem supported by upper and lower bearings or bushings selected for the operating temperature band. Sealing is achieved by precise geometry between the metal disc edge and the metal seat ring: both surfaces are hardened or overlay-welded to resist galling and wear. Because the seal is entirely metallic, there is no elastomer or laminate to extrude, no graphite pack to blow out under steam purge and no PTFE layer to cold-flow at elevated temperature. Trekre applies controlled machining and lapping so contact pressure remains uniform across the seal line at rated differential pressure, supporting bi-directional shut-off in many duty classes.

Size range and pressure ratings. Standard production covers nominal diameters from DN50 to DN1200 (NPS 2 to 48) with pressure classes from PN10 and PN16 through PN25, PN40, PN63 and up to PN160 for selected body materials and bore configurations. Face-to-face dimensions can be supplied to EN 558 Series 13/14, API 609 Category B or project-specific lengths when replacement-in-kind must match existing piping layouts. Bore options include full bore for minimal pressure drop and reduced bore where actuator torque or weight limits apply. Trekre confirms flange drilling, bolt circle and gasket seating width against the purchaser piping class before release to fabrication.

Body, disc and seat materials. Carbon steel WCB and WCC serve general industrial and steam-adjacent duties within the material temperature limits of the chosen grade. Stainless steel CF8, CF8M and CF3M cover corrosive condensate, weak acid and oxidising environments where rust scale on soft-seated valves would contaminate the process. Alloy options such as WC6, WC9 or CF8C extend creep resistance for high-temperature branches. The all-metal seat ring is typically Stellite or equivalent hard-facing on a stainless or nickel-base substrate; the disc sealing edge receives matching overlay or nitriding so both sides of the hard-to-hard pair share compatible hardness and thermal expansion. Stem material is usually SS410, SS316 or 17-4PH depending on torque, corrosion and temperature. Packing systems combine flexible graphite or PTFE-based rings with live-loading where fugitive-emission targets apply.

Drive and operation. Manual worm gear operators handle larger diameters and higher differential pressure where hand-lever torque would exceed ergonomic limits. Bare stem with ISO 5211 mounting pad accepts pneumatic or electric actuators for remote shut-off, interlock or ESD logic. Chain wheel or extension stem arrangements are available for buried, elevated or insulated lines when direct access to the operator is restricted. Trekre sizes the actuator after calculating break torque, running torque and safety factor at maximum design differential, including partial-stroke conditions where dynamic flow loads the disc. Limit switches, position transmitters and lockable handwheel devices can be integrated per project specifications.

Applicable working conditions. The two way hard to hard construction suits fully open, fully closed and throttling positions across a wide envelope: continuous service up to approximately 800 °C on selected alloy configurations, cryogenic exposure down to -196 °C for LNG and cold-box branches, and high-pressure steam or process lines within the rated PN class. All-metal contact resists damage from high-speed fluid flushing during start-up, blow-down or emergency venting — conditions that often destroy laminated metal-seal designs. Typical industries include petrochemical cracking and reforming units, power-plant main steam and condensate isolation, metallurgical off-gas and quench water, refining vacuum and coker overhead, and high-temperature chemical synthesis where polymerisation or coke formation excludes soft seats.

Standards and testing. Design and inspection reference API 609, MSS SP-67, EN 593 or GB/T 12238 as agreed in the purchase order, with shell and seat/leakage tests per API 598 or EN 12266. Trekre documents material heat numbers, NDE where specified (PT, MT, RT on critical welds), dimensional reports and hydrostatic or pneumatic seat tests before shipment. Special tests — fire-safe protocol, low-temperature impact, Fugitive Emissions ISO 15848 or customer witness — are scheduled when the data sheet calls for them.

Product parameters

Selection checklist for engineers. Confirm nominal size, pressure class, flange standard and face-to-face dimension against the piping isometric. State minimum and maximum operating temperature, media composition, solids content and allowable leakage class. Indicate whether bi-directional shut-off, partial-stroke throttling or rapid cycling is required. Specify actuator type, fail position, control voltage or air supply, and any interlock with DCS or SIS. Provide insulation, extension stem or underground box details early so bolt lengths and operator orientation are correct at site. Trekre Valve technical staff review these inputs and return a bill-of-materials aligned with the two way hard to hard all metal hard sealed butterfly valve configuration best suited to the duty.

Installation and maintenance notes. Install the double-flange butterfly valve with flange bolts torqued evenly in a star pattern so gasket load is uniform and the body is not twisted. Leave sufficient clearance above the operator for handwheel rotation or actuator maintenance. Before first start-up, cycle the valve from open to closed several times at zero differential pressure to confirm smooth stem rotation and correct stop alignment. During service, inspect packing glands for leakage and adjust live-load followers as needed; metal-seal contact surfaces should not be lubricated with grease that could carbonise at high temperature. Trekre supplies maintenance manuals listing recommended inspection intervals for high-cycle and high-temperature duties.

Comparison with laminated metal-seal designs. Conventional triple-offset butterfly valves often combine stainless base metal with graphite or PTFE laminates to achieve low leakage at moderate temperature. Under erosive flow, thermal cycling or rapid depressurisation, those interlayers can delaminate and allow bypass leakage that is difficult to repair in line. The two way hard to hard all metal hard sealed butterfly valve eliminates that failure mode by keeping the entire sealing interface in metal. Initial contact stress may be higher and machining cost greater, but lifecycle cost improves on duties with frequent thermal shock, steam impingement or solids in the stream. Trekre engineers can advise when all-metal hard-to-hard sealing is preferable to laminated or soft-seated alternatives for a given P&ID node.

Common application mistakes. Ordering a multi-layer laminated metal seal for high-velocity blow-down service when an all-metal hard-to-hard pair is required leads to early seal failure. Specifying soft-seat temperature limits on a line that routinely exceeds 250 °C causes permanent set and leak paths. Undersizing actuator torque for partial-open throttling under high delta-P prevents full closure and damages the gearbox. Mixing flange standards between valve and mating flanges without verifying bolt circle and gasket width creates assembly gaps. Trekre recommends sharing P&ID excerpts, operating cases and previous failure history so the valve specification matches real plant conditions rather than catalogue defaults alone.

For quotation, submit flange rating, material preference, drive type and delivery schedule. Trekre Valve — China valve manufacturer — produces two way hard to hard all metal hard sealed double flange butterfly valves with documented inspection and export packaging suitable for global project logistics.