Flowserve Durco TX3 Triple Offset Butterfly Valve

Overview

The Flowserve Durco TX3 is a triple offset butterfly valve that combines zero-leakage, bi-directional shutoff with the low operating torque and reduced wear of a triple offset geometry. The precision seat and seal of the Durco TX3 are machined at an offset angle, creating even seat loading around the entire seat ring and eliminating rubbing between seat and seal during opening and throttling. Together with its laminated metal seal ring, this design provides long-lasting, bubble-tight shutoff even in gas applications. The valve is offered from NPS 3 to 60 in ANSI Class 150, 300, 600, 900 and 1500, for temperatures from -196 °C to 820 °C, in wafer, lug, double-flanged and top-entry cryogenic body styles.

Seven Star LLC supplies the Durco TX3 and its actuation packages to oil and gas, LNG, refining, petrochemical and power customers across the Sultanate of Oman and the GCC, with engineering support in Muscat. We help engineers select body style, material, seal ring and actuator for isolation and control duties, and coordinate complete automated valve packages for projects and shutdowns in Muscat, Sohar, Duqm and Salalah.

Operating Principle of the Durco TX3

The three offsets of the Durco TX3 work together. The first two, placing the shaft behind the sealing plane and away from the pipe centreline, move the disc out of the seat as soon as it starts to open. The third offset, the inclined cone angle of the seat and seal, means that the elliptical sealing surfaces only make contact in the fully closed position. Flowserve explains that this eliminates the wear associated with sealing-surface contact and maintains sealing integrity during high-cycle operation, while the low-friction, low-wear elliptical surfaces keep operating torque low and extend service life.

As general engineering background, a metal-seated triple offset valve closes by torque rather than by interference, so the actuator pushes the seal into the seat to achieve tightness. This allows a quarter-turn butterfly valve to replace heavier gate or ball valves in high-temperature, cryogenic and fire-safe services, often with a shorter face-to-face, lower weight and a smaller actuator.

Engineering Design of the Durco TX3

The standard seal ring of the Durco TX3 is a laminated construction of alternating metal and graphite layers. Each layer seals independently and is unaffected by damage to the others, creating a robust multi-point seal that is fire-safe tested to API 607 and meets API 598 resilient-seat, ISO 5208 Rate A and MSS SP-68 requirements for no visible leakage. The metal plates are duplex 31803 as standard, with 316 stainless steel, Inconel, Monel and Hastelloy options. For extreme temperatures, a solid metal seal ring is available, meeting API 598 metal-seat, ISO 5208 Rate CC and FCI 70-2 Class IV and V. The seat surface is Stellite® for long-lasting sealing performance.

Bodies are available in carbon steel, stainless steel, duplex stainless steel, Inconel® 625, Monel®, Hastelloy® C and Alloy 20. Configurations include wafer, lug and double-flanged short or long pattern to ASME B16.10, plus butt weld, cryogenic and offset top entry options; the double-flanged long body allows an existing ball or gate valve to be replaced by a smaller, lighter valve without piping changes. A robust anti-blowout shaft meets API 609 and ASME B16.34, hardened bearings support the shaft, a bottom flange eases maintenance and multiple PTFE and graphite packing options meet ISO 15848-1. Actuation is by the Limitorque LPS Scotch yoke actuator, rated up to 550 kNm, or by Automax RG-Series or SuperNova rack and pinion actuators, with the Logix 3800 digital positioner for control duties.

Key Features of the Durco TX3

Users specify the Durco TX3 for the following reasons:

• Triple offset design eliminates seat and seal rubbing for long life in high-cycle operation.
• Bi-directional, zero-leakage shutoff tested to API 598, with bubble-tight sealing even in gas service.
• Laminated metal and graphite seal ring with independent multi-point sealing, or solid metal seal ring.
• Sizes NPS 3 to 60 and ANSI Class 150 to 1500.
• Temperature rating from -196 °C to 820 °C, covering cryogenic and high-temperature duties.
• API 607 fire-safe design and API 609 anti-blowout shaft.
• Low operating torque allows compact, cost-effective actuation.
• Certifications including PED, TRCU, CRN, IEC 61508 SIL and ISO 15848-1 fugitive emissions.

Industrial Applications

Flowserve lists oil and gas midstream, LNG processing and transfer and hydrofluoric acid alkylation, power generation including molten salt and thermal oil isolation and control, chemical processing and general industries as the target markets for the Durco TX3. In Oman and the GCC it suits gas pipeline and compressor station isolation, LNG and cryogenic transfer lines, hot oil and heat transfer systems, steam isolation in utilities, and corrosive services in refineries and petrochemical complexes at Sohar, Duqm and Qalhat, including end-of-line service where its tight shutoff is valued.

Seven Star LLC supplies the Durco TX3 as a bare valve or a fully automated package and can align it with other Flowserve products used on site, such as the Argus FK79 floating ball valve for smaller isolation duties and the Rotadisk pneumatic actuator for quarter-turn automation. For throttling duties, the Logix 3800 digital positioner is available through our team as well.

Technical Specifications

Key data from the Flowserve product brochure is listed below:

How to Order

To receive a formal quotation for the Durco TX3, send Seven Star LLC the line size, pressure class, fluid, temperature, required shutoff standard, body style and actuation requirement. Our engineers in Muscat will confirm the configuration, prepare the quotation and support delivery, installation and commissioning anywhere in Oman or the GCC. The Flowserve product brochure can be downloaded from this page.