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Flange End Stainless Steel Double Offset Soft Sealed High Performance Butterfly Valve

The Flange End Stainless Steel Double Offset Soft Sealed High Performance Butterfly Valve is an advanced quarter-turn valve designed for critical industrial flow control applications. It combines the mechanical advantage of a double-offset disc design, the leak-tight performance of a soft seal, and the durability of stainless steel construction. This configuration is particularly valued in industries where both corrosion resistance and tight shut-off are essential, such as chemical processing, desalination, power generation, oil & gas, and HVAC systems. By integrating a flange end connection, this valve provides secure bolted joints with mating pipeline flanges, ensuring reliable sealing and alignment during operation. Its high-performance design makes it capable of handling higher pressures, temperatures, and more demanding service conditions compared to standard concentric butterfly valves.

    Design Principles

    1. The double offset (also known as “high performance”) configuration incorporates two distinct shaft offsets:
    First Offset – The shaft is offset from the disc centerline, reducing friction between the disc and seat during operation.
    Second Offset – The shaft is further offset from the centerline of the valve body, ensuring the disc moves away from the seat quickly when opening, minimizing wear.
    This geometry offers:
    Reduced sealing surface contact during operation.
    Lower operating torque requirements.
    Extended seat and disc life.
    2. Soft Seal Mechanism
    The soft seal element (typically PTFE, reinforced PTFE, EPDM, NBR, or other elastomers) ensures bubble-tight shut-off in accordance with API 598 or ISO 5208 leakage standards. Soft sealing materials also provide:
    Excellent sealing performance at low pressures.
    Resistance to certain chemicals depending on material selection.
    Quieter operation compared to metal seats.
    3. Stainless Steel Construction
    The body, disc, and shaft are manufactured from stainless steel grades such as CF8M (316 stainless steel), CF3M (low-carbon 316), or duplex stainless steel depending on service requirements. Benefits include:
    High corrosion resistance in aggressive media.
    Resistance to pitting and crevice corrosion.
    Durability in marine, chemical, and food processing environments.
    4. Flange End Connection
    The flange end design conforms to standards such as ASME B16.5, EN 1092-1, or JIS B2220, ensuring:
    Easy bolting to pipeline flanges.
    Strong mechanical connection for higher pressures.
    Better alignment and reduced leakage risk compared to wafer or lug type connections.

    Technical Specifications

    (Typical configuration – can vary by manufacturer)

    Parameter

    Typical Range / Standard

    Design Standard

    API 609, MSS SP-68, ISO 5752

    Size Range

    DN 50 – DN 1200 (2" – 48")

    Pressure Class

    ASME Class 150 / 300

    Body Material

    CF8M, CF3M, Duplex SS

    Disc Material

    CF8M, Duplex SS

    Seat Material

    PTFE, RPTFE, EPDM, NBR

    Shaft Material

    17-4PH, XM-19, Duplex SS

    End Connection

    Flanged – ASME B16.5 or EN 1092-1

    Leakage Class

    API 598 / ISO 5208 Rate A (bubble-tight)

    Operation

    Manual gearbox, pneumatic actuator, electric actuator

    Temperature Range

    –29°C to +200°C (depending on seat)

    Face-to-Face

    API 609 / ISO 5752 Series

    Working Principle

    The valve operates on a quarter-turn principle:
    Closed Position – The disc presses against the soft seat, creating a tight seal.
    Opening – Rotating the shaft 90° moves the disc away from the seat, thanks to the double offset, minimizing rubbing.
    Fully Open – The disc is parallel to the flow, offering minimal resistance.
    The double offset ensures that the disc does not scrape against the seat except during the final degrees of closure, reducing wear and torque requirements.

    Key Features & Advantages

    1. High Sealing Performance
    Bubble-tight shut-off capability.
    Ideal for critical shut-off applications in liquid, gas, or steam service.
    2. Lower Operating Torque
    Reduced seat friction extends actuator life and lowers energy consumption.
    3. Corrosion Resistance
    Stainless steel body and disc resist corrosion in saline, acidic, or alkaline environments.
    4. Durability
    Extended service life due to reduced wear on sealing surfaces.
    5. Versatile End Connection
    Flange ends provide strong sealing integrity and ease of installation.
    6. Compliance with International Standards
    Meets API, ISO, EN, and ASME requirements for design, testing, and performance.

    Applications

    1. Oil & Gas Industry
    Used in onshore/offshore pipelines, process lines, and storage terminals for hydrocarbons and refined products.
    2. Chemical & Petrochemical
    Handles corrosive chemicals, solvents, and acids with appropriate soft seat selection.
    3. Water & Wastewater
    Ideal for potable water, seawater desalination plants, and wastewater treatment systems.
    4. HVAC & Power Generation
    Used in cooling water loops, condenser systems, and auxiliary services in power plants.
    5. Marine & Offshore
    Excellent for ballast water, fire protection systems, and seawater cooling systems.

    Installation Guidelines

    1. Pre-Installation Checks
    Verify valve size, pressure class, and materials against specifications.
    Ensure pipeline flanges match the valve’s drilling standard.
    Clean pipeline to remove debris.
    2. Installation Procedure
    Position the valve between pipeline flanges, ensuring correct flow direction if applicable.
    Insert bolts and tighten in a cross pattern to ensure even gasket compression.
    Confirm disc movement before fully tightening.
    3. Alignment
    Proper alignment prevents disc interference with pipe walls and ensures long sealing life.

    Maintenance Practices

    1. Routine Inspection
    Check for leaks around flange joints and seat.
    Inspect actuator and gearbox for smooth operation.
    2. Seat Replacement
    Soft seats can be replaced in-line on many designs without removing the valve from the pipeline.
    3. Stem & Seal Lubrication
    Lubricate periodically if recommended by manufacturer.

    Standards & Testing

    1. Design Standards
    API 609 – Butterfly valves for general and high-performance service.
    MSS SP-68 – High-pressure, high-temperature butterfly valves..
    2.Testing Standards
    API 598 – Valve inspection and testing.
    ISO 5208 – Pressure testing of valves..
    3.Face-to-Face Dimensions
    ISO 5752 or API 609 ensures interchangeability between manufacturers.

    Advantages over Concentric Butterfly Valves

    Better sealing under high pressure due to double offset geometry.
    Lower seat wear because of minimal rubbing during operation.
    Higher temperature capability with reinforced soft seals.
    Greater pressure ratings – often up to ASME Class 300.

    Limitations

    Not suitable for abrasive slurries that may erode the soft seat.
    Higher initial cost compared to standard concentric valves.
    Requires careful material selection for specific chemicals to avoid seal degradation.

    Conclusion

    The Flange End Stainless Steel Double Offset Soft Sealed High Performance Butterfly Valve represents a significant step up from conventional butterfly valves in terms of performance, durability, and sealing capability. Its combination of double offset geometry, soft sealing technology, and corrosion-resistant stainless steel construction makes it highly versatile and reliable in demanding industrial environments. From chemical plants to offshore platforms, this valve delivers long service life, reduced maintenance, and excellent flow control, making it a preferred choice for engineers seeking high performance in critical applications.

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