Triple Offset Butterfly Valves: An Overview

The triple offset-type butterfly valve is a lightweight, low-torque, compact, and low-cost valve that can replace conventional gate valves, globe valves, or ball valves under most service conditions. It is developed on the basis of conventional resilient seated butterfly valves and has the following features: light weight, low torque, compact design, and low cost.

The GNEE triple offset butterfly valve features a hard seat design with one-quarter turn, bidirectional sealing, and fire-safe performance. This eliminates the material aging and deformation issues of soft-seated butterfly valves. The top entry design also allows for online maintenance.

Design Standards

Scope of Product

Design Features

Offset 1

The center of the valve stem is higher than the sealing surface, which guarantees the continuity of the sealing surface.

Offset 2

The center of the valve stem deviates from the center of the valve body, which reduces the opening friction force between the disc and seat.

Offset 3

The opening and closing torque is transmitted to the sealing pair of the valve disc through the valve stem. The unique resilient sealing design ensures zero leakage under both water pressure and air pressure.

• Reliable bidirectional zero-leakage and tight sealing.
• Replaceable sealing pair.
• No dead-end construction.
• All metal construction with intrinsic fire resistance is suitable for a wider range of temperature and pressure.
• Torque forced seals.
• Integral valve stem design with high stiffness.
• Hardened valve seat,which extends the lifetime of the valve, and reduce the frequency of maintenance.
• The standard ISO5211 upper flanges matched with actuator are used.
• Double valve stem anti blow-out design, effectively ensuring pressure safety.
• The upper valve stem is slotted and embedded into the split ring. The bottom valve stem is designed as a stepped shaft.
• The extended bearing design, combined with unique finish machining and hardening treatment, reduces friction on the valve stem and reduces torque.
• Optional multi-level and all-metal sealing ring constructions can be used with a variety of media.
• Valve stem sealing design with fugitive emission: API622 stem packing with fugitive emission. The valve stem is guided and positioned throughout its travel to avoid packing leakage due to lateral displacement. Surface roughness control of the valve stem and stuffing box. Optional gland flange for dynamic load. The fugitive emissions comply with ISO 15848, API 641 and TA-Luft.

Material Specifications

Dimensions & Weights

Double Flanged

Double Flange (long series)

But-Weld

Wafer

Lug

Notes
1. Face to face dimensions are in accordance with the latest edition of stated standard.
2. Flange/end connections are in accordance with ASME B16.5 or ASME B16.47.
3. Please consult SNY for other available sizes, classes and connections.

Class 150 & Class 300

Class 600 & Class 900 (MM Units)

Class 600 & Class 900 (Inch Units)

Triple Offset vs Double Offset vs Concentric

The rule of thumb: below 200 °C with no fire requirement, a concentric or double-offset valve is the economical choice and a triple offset is over-specified. Above 200 °C, on flammable service, or wherever bubble-tight metal seating is written into the datasheet, the triple offset is the correct call.

Applications

The valve earns its place wherever a resilient seat would fail or where bidirectional isolation must be certified. Five service groups cover most enquiries:

Power plant steam and bypass lines

Main steam, turbine admission and extraction lines run at 450–570 °C, where EPDM/NBR seats are long gone. Alloy-steel bodies with Stellite-faced seats hold shutoff through thermal cycling that destroys soft-seated valves.

LNG and cryogenic service

BOG headers, LNG transfer and send-out lines operate from −196 °C to about +150 °C. Low-temperature bodies (LCB/LCC) and duplex discs provide tight shutoff without the embrittlement risk of standard trim.

Refinery and petrochemical hydrocarbon lines

Crude, vacuum residue, hot oil and vapour-recovery lines expose seats to heat and flammable media. Metal seats are inherently fire-safe, and the valve's short face-to-face saves weight against a same-class ball valve.

Gas transmission and compressor stations

Large-diameter Class 150/300 block and bypass valves, offtake metering and town-border stations use wafer and lug bodies where a ball valve of the same bore would be disproportionately heavy and costly.

Chemical and marine/seawater systems

Concentrated acid, chlorine and caustic services use CF8M or duplex bodies; seawater cooling and ballast use duplex with anti-corrosion coating. Metal seats resist the abrasive particles that would chew a soft seat.

Why Source Triple Offset Butterfly Valves from GNEE

Integrated supply, not just a catalog. GNEE combines trading and manufacturing partnerships to cover the full DN 50–DN 2000, Class 150–600 envelope with wafer, lug and double-flanged ends, and to consolidate third-party inspection and documentation for EPC projects.

Material and seat flexibility. Carbon, stainless, duplex, low-temperature and alloy bodies with metal, laminated or soft seats - quoted to your medium, temperature and leakage class rather than a single stock configuration.

Documentation readiness. EN 10204 3.1 MTC, API 607 fire-test report, and SGS/BV/TÜV witnessing available for submittals.

Export experience. 160+ customers served, Tianjin Beichen (No.4-1114) operations, shipments from major Chinese ports, OEM/ODM and custom engineering supported.

packaging and shipping

 

 

 

Send your line size, ASME Class or PN rating, end connection and seat type - our technical team will confirm the specification and return a quotation with lead time within 24 hours. Standard configurations typically deliver in 2–4 weeks; exotic alloys run 8–12 weeks. Contact GNEE today or call +86 15824687445.

FAQ

What makes a triple offset butterfly valve different from a standard or double offset butterfly valve?

A concentric (standard) butterfly valve centers the shaft in the disc and uses a soft seat, limiting it to about Class 150 and 120 °C. A double-offset valve moves the shaft behind the disc to cut rubbing but still relies on soft or semi-metal seats near 200 °C. A triple offset valve adds a third conical offset so the disc cams away from a conical metal seat with no contact until the final 1–2° of closure - enabling a metal-to-metal seal rated to ISO 5208 Rate D, bidirectional shutoff, and fire-safe performance to roughly +600 °C.

What is the maximum temperature and pressure a triple offset butterfly valve can handle?

Pressure follows API 609: Class 150, 300 and 600 as the standard envelope, with the 10th edition (2026) extending Category B to Class 900. Temperature depends on the body and seat materials: carbon and stainless bodies (WCB, CF8M) typically span −46 °C to +425 °C, while alloy steel bodies with hardfaced (Stellite or Inconel) seats extend service to about +540–600 °C; cryogenic duty to −196 °C requires low-temperature or duplex materials. Claims of Class 2500 or +850 °C are outside the standard envelope and should be treated as custom-engineered exceptions, not catalog ratings.

What leakage class does a metal-seated triple offset butterfly valve achieve?

Metal-to-metal seats are qualified to ISO 5208 Rate D - a defined, very low leakage allowance measured per port diameter, not zero. Soft (PTFE or laminated) seats reach ISO 5208 Rate A, which is bubble-tight with no visible leakage. Note that "API 598 Class VI" is incorrect for isolation valves: API 598 has no Class VI, and the Class V/VI scale belongs to ANSI/FCI 70-2 for control valves. Specify the ISO 5208 rate you require rather than a control-valve class.

Is a triple offset butterfly valve fire-safe?

Yes. A metal-seated triple offset valve has no elastomer in the sealing path, so it retains a metal-to-metal seal after a fire; this is verified by fire testing to API 607 (latest edition 2022) as a type test. Soft-seated concentric and double-offset valves are not fire-safe in standard form. Where the line handles flammable fluids, specify API 607 fire-tested valves or a metal-seated triple offset design.

What is the difference between API 609 Category A and Category B?

Category A covers concentric, manufacturer-rated CWP butterfly valves (typically Class 125/150, NPS 2–60) for water and HVAC. Category B covers offset-disc valves with ASME Class and pressure-temperature ratings (Class 150–600, and Class 900 in the 10th edition, 2026) in lug, wafer, double-flanged and now butt-weld ends - this is the category that includes high-performance and triple-offset valves for refinery, power and hydrocarbon service.

Can a triple offset butterfly valve be used for throttling?

It is primarily an on/off isolation valve. The geometry gives a relatively linear flow characteristic, so it can handle moderate throttling, but continuous throttling at high pressure drop will erode the seat and is not its design intent. For severe or precise flow control, specify a dedicated control valve; use the triple offset valve for tight shutoff and isolation.

Is a triple offset butterfly valve a DBB (double block and bleed) valve?

No. A single triple offset valve provides bidirectional tight shutoff from one seat pair, but it is not a double-block-and-bleed device. Achieving DBB requires two isolation valves in series with a bleed between them. Do not specify a single triple offset valve as DBB; if double isolation is required, show two valves and a bleed connection on the datasheet.

How do I specify a triple offset butterfly valve for a quotation?

Provide quantity and size (DN/NPS), pressure class (ASME Class or PN), end connection (wafer, lug or double-flanged, with flange standard such as ASME B16.5), body and seat materials, liner/seat type (metal or soft), operating temperature and medium, actuation (lever, gear, electric or pneumatic per ISO 5211), required leakage class (ISO 5208 Rate A or D), any fire-safe (API 607) or sour-service (NACE MR0175 / ISO 15156) requirement, and destination port with lead-time expectation.