Double Flange Vacuum Butterfly Valve Triple Offset Metal Hard Seal
The double flange vacuum butterfly valve with triple-offset disc geometry is a quarter-turn isolation valve engineered for vacuum pipelines, process gas headers and vacuum equipment manifolds where reliable shut-off across positive and negative pressure differentials is required. Manufactured by Trekre Valve at our Wuxi production facility, this double-flanged vacuum butterfly valve connects directly to pipeline flanges on both ends, providing stable mechanical support for larger nominal sizes and higher pipe loads compared with wafer-style alternatives. The internal flow path employs a three-eccentric disc arrangement that lifts the sealing surface away from the seat during opening, reducing friction, minimizing wear and supporting repeatable closure in vacuum and low-pressure gas service.
Unlike general-purpose butterfly valves rated only for positive gauge pressure, vacuum service valves must maintain seal integrity when the downstream side is pumped below atmospheric pressure, when the line is vented to atmosphere during maintenance, and when bidirectional pressure differentials occur across the closure member during pump-down and backfill sequences. The double flange vacuum butterfly valve addresses these conditions through a non-rising stem design, upper bonnet packing gland, metal or fluoropolymer seat options and a disc locking device that holds the closure element in position under vibration and thermal cycling common on vacuum skids and coating equipment.
Construction and triple-offset sealing design
Connection type: double-flanged butterfly valve with raised-face or flat-face flange ends per ANSI B16.5 Class 150/300, EN 1092 PN10/PN16/PN25, DIN 2501 or JIS B2220 when cross-standard packages are specified on the purchase order.
Structure: triple-offset (three eccentric) disc and stem geometry; one-piece stem with blowout-proof lower bearing, adjustable upper gland packing and position indicator on the operator. The stem does not move axially during rotation, which simplifies actuator mounting and reduces packing wear in vacuum lines subject to frequent cycling.
Sealing form: metal hard seal with stainless steel or Stellite overlay on the disc edge against a metal seat ring for elevated temperature process gases and abrasive media; PTFE, PFA or elastomer resilient seats for bubble-tight shut-off on clean air, nitrogen and inert gas at moderate temperatures.
Body material: stainless steel CF8 (304), CF8M (316) and CF3M for corrosive or condensable vapour service; carbon steel ASTM A216 WCB with surface treatment for dry air and utility vacuum headers where cost efficiency is prioritized.
Disc and stem: stainless steel disc with optional hardfacing; stem in SS416, SS304 or SS316 with surface finish matched to seat material and operating temperature.
Operation: manual lever handle on smaller sizes; worm gear reducer for mid-to-large bore; pneumatic double-acting or spring-return actuator and electric quarter-turn actuator for automated vacuum process lines.
Double flange interface and vacuum pipeline integration
Double-flanged end connections provide independent bolt circles at inlet and outlet, allowing the valve body to serve as a fixed pipeline element without relying on adjacent flanges for structural support as wafer designs do. This format is preferred on vacuum manifolds where pipe spans, equipment loads and thermal expansion must be managed without distorting the valve body or compromising seat contact. Flange facing, gasket type and bolt length must be confirmed against the project piping specification before installation.
On vacuum systems the valve may experience absolute pressures from rough vacuum through high vacuum depending on the pumping train, chamber volume and upstream isolation strategy. The double flange vacuum butterfly valve is factory tested for seat leakage at project-specified conditions. When integrated into semiconductor process tools, coating chambers, freeze-drying equipment or industrial degassing circuits, confirm target base pressure, allowable leak rate, bake-out temperature limit and outgassing requirements for body and seat materials so the selected trim meets the cumulative leakage budget of the conductance path.
Working principle and disc locking device
The disc rotates approximately 90 degrees about the stem axis to open or close the flow passage. Triple-offset geometry positions the sealing contact on a conical seat path so the disc cams into the seat only in the final degrees of closure, reducing scrape and particle generation compared with concentric disc designs. A disc locking device on the closure plate helps maintain position under pipeline vibration, actuator backdrive and differential pressure across the seat during pump-down transitions.
Non-rising stem construction keeps the packing gland stationary relative to the bonnet while the stem rotates. Packing adjustment and stem seal replacement are different maintenance tasks. Confirm access and any required actuator removal from the instructions for the exact valve and actuator assembly. Before maintenance, isolate the process, establish the specified safe pressure condition and control stored energy in accordance with the approved procedure. Upper bonnet packing typically combines multiple V-ring or braided graphite sets with anti-extrusion rings suited to the temperature envelope and gas compatibility of the service medium.
Nominal size and pressure rating
Nominal diameter range: DN50 through DN1200 (2 inch through 48 inch) depending on pressure class, seat design and actuator torque envelope. Standard production covers DN80 to DN600 for vacuum process skids; larger sizes available on project inquiry with extended lead time for casting and test capacity.
Pressure and vacuum requirements must be evaluated separately for the selected valve. For vacuum duty, specify the minimum absolute operating pressure, maximum differential pressure, allowable seat and external leakage rates, test method and temperature. Positive-pressure ratings, where required, must correspond to the actual pressure-boundary materials, flange connections and documented pressure-temperature rating. Bidirectional shut-off must not be assumed without the applicable test and rating information.
Face-to-face dimensions follow ISO 5752, API 609 or EN 558 Series 13/14 tables for double-flanged butterfly valves according to the nominated flange standard and pressure class. Provide flange standard, pressure class and structural length series on the inquiry form to avoid mismatches during site assembly.
Design standards and factory testing
Design references: API 609 Category B and EN 593 where applicable to the selected valve construction and project specification. Flange requirements must follow the actual mating flange standard and approved valve drawing. Pressure-boundary and seat testing may reference API 598 or ISO 5208 where specified; vacuum suitability additionally requires the minimum absolute pressure, allowable leakage rate, test method and test temperature for the exact assembly. Product certificates and test records should correspond to the supplied valve and agreed inspection scope.
Drive methods and actuation selection
Worm gear manual operation is the conventional drive for double flange vacuum butterfly valves in mid-to-large sizes, providing torque multiplication and a self-locking hold under differential pressure across the disc. The gear unit includes mechanical stops at fully open and fully closed positions and a visible position indicator for operator verification during maintenance lockout procedures.
Pneumatic actuators deliver fast on/off response for interlocked vacuum sequences, load-lock chambers and automated vent/isolation manifolds. Electric actuators support remote open/close commands, limit switch feedback and fieldbus integration for distributed control systems. Actuator sizing must account for break torque at maximum differential pressure, safety factor, ambient temperature at the installation location and any required fail-safe position on loss of air or power.
Applicable working conditions and industries
This double flange vacuum butterfly valve with triple-offset metal hard seal is specified for vacuum drying ovens, solvent recovery headers, semiconductor etch and deposition foreline branches, pharmaceutical freeze-drying circuits, chemical degassing manifolds, metallurgical vacuum furnaces, laboratory vacuum networks and industrial gas isolation on pump sets where double-flanged pipeline connections are the governing installation standard.
Metal hard seated configurations handle process gases at elevated temperature where elastomer seats would degrade, including thermal conditioning lines subject to periodic bake-out within the material limits of body and trim. Resilient seated versions serve clean air, nitrogen, argon and inert gas on utility vacuum headers where bubble-tight closure at moderate temperature is the primary requirement.
Typical industries include vacuum equipment manufacturing, semiconductor fabrication, pharmaceutical production, chemical processing, food vacuum packaging, power plant auxiliary degassing systems and research institutions operating coated-chamber or thin-film deposition tools. The double-flanged body format simplifies integration with existing ANSI or EN vacuum piping without adapter spools on many project layouts.
Installation, maintenance and service notes
Verify flange facing, gasket selection and bolt torque in incremental steps to achieve uniform compression without distorting the valve body. On vacuum lines, perform leak checks using helium mass spectrometry or approved pressure-rise methods after assembly and before introducing process gases. Avoid slamming the disc against the seat at high differential pressure, which accelerates seat wear and can compromise long-term vacuum performance.
Routine maintenance includes inspecting stem packing for wear, confirming smooth rotation through the full stroke, cleaning disc and seat contact surfaces and verifying actuator limit settings. Replaceable seat designs on applicable configurations simplify field refurbishment. Allow clearance above the worm gear or actuator for maintenance access and handwheel rotation in mechanical rooms and skid-mounted packages.
Product parameters
- Valve type: double flange vacuum butterfly valve, triple offset, metal hard seal
- Model reference: D343H-V / project-specific designation
- Size range: DN50–DN1200 (2″–48″)
- Pressure and vacuum rating: specify the documented positive-pressure class, minimum absolute pressure, allowable leakage rate and test conditions for the selected valve configuration
- Body: WCB carbon steel, CF8/CF8M/CF3M stainless steel
- Disc: stainless steel with metal seat or PTFE resilient seat
- Stem: stainless steel, non-rising, blowout-proof, adjustable packing
- Operation: lever handle / worm gear / pneumatic / electric actuator
- Design references: API 609 and EN 593 where applicable to the actual butterfly-valve construction and approved project specification
- Test standard: API 598, ISO 5208, vacuum leak test on request
- Leakage class: metal seat per API 598; resilient seat bubble-tight on air/water
Contact Trekre Valve with complete operating data—medium composition, design temperature, target vacuum range, nominal size, flange standard, actuation method and allowable leak rate—to receive a technical proposal and quotation for double flange vacuum butterfly valves suited to your vacuum pipeline or process equipment project.
Frequently Asked Questions
Can this flanged vacuum valve also handle positive pressure?
Specify the required pressure conditions and directions, including pump-down and venting states. Request the documented rating of the exact valve rather than assuming a vacuum description establishes a positive-pressure rating.
Which leakage data should I request for my vacuum application?
State the required test method, gas, pressure conditions and acceptance criteria. Ask for the selected valve’s applicable test evidence rather than using a general shutoff claim as vacuum leakage data.
What connection information should I send for a replacement?
Provide the actual flange standard, facing, drilling and face-to-face dimensions along with the seal and operating requirements. Confirm the selected drawing before approving the replacement.