Turcon® Variseal® MC Seal

Two Heads are Better than One

In oil and gas exploration, avoidance of downtime is critical, which is why equipment manufacturers are continually looking to enhance the solutions they offer to operators. Rather than working alone, these manufacturers use the specialized expertise of suppliers to stretch the performance boundaries of their equipment. And that is exactly what LB Bentley did when it developed its latest rotary gate valve.


for subsea applications that introduced the now standard subsea rotary gate valve into the market in 1998. As subsea oil and gas exploration becomes increasingly challenging, the company realized a highly specialized gate valve that met a wide range of extreme working pressures and operating conditions was needed and development has resulted in its new Medium Duty Rotary Gate Valve.

Custom solution

On this valve, LB Bentley worked in close partnership and with support from Trelleborg Sealing Solutions. To meet demanding requirements, Trelleborg developed a custom version of Turcon® Variseal® MC with high pressure extrusion resistance and back-pressure protection in NORSOK M-710 compliant PTFE and PEEK materials to provide the main stem sealing function. In order to cater for subsea use, Trelleborg’s Turcon® Glyd Ring® T was selected as a contaminant exclusion seal.

The solution demonstrates pioneering stem sealing technology that reduces the risk of contamination and failure while maintaining a high level of reliability.

“Throughout the development process, we constantly had to think about safety issues and challenges that are frequently faced when working with vital subsea equipment,” says Antoine Charrier, a Key Account Manager at Trelleborg Sealing Solutions “We pride ourselves on innovation and relished this opportunity to work with LB Bentley, developing innovative stem sealing technology that reduces the risk of contamination and failure.”

A key partner

LB Bentley works hard to meet its customers’ needs, striving toward continuous improvement. “That means the qualification status of our products is constantly developing. This enables us to offer an expanding range of fully qualified products and we’re immensely proud of the Medium Duty Rotary Gate Valve that Trelleborg has been a key partner in helping us to develop,” says, Noelle Sears, Design Engineer at LB Bentley.


The seal was developed to replace multiple chevron seals or V-Stack type products in subsea valve stems that require a high-integrity sealing capability. It includes a series of single-acting spring-energized seals housed within a U-shaped Turcon® polytetrafluoroethylene (PTFE) based material seal profile. The unique single-piece design significantly improves sealing integrity and leak tightness in high-pressure applications by providing higher contact force across multiple seal hardware interfaces.

Turcon® Variseal® MC advantages and benefits:

  • Good static and semi-dynamic sealing effect
  • Reduced friction under high loads
  • Almost universal chemical compatibility
  • Permanent elasticity unaffected by contact with chemicals
  • Available with anti-extrusion Back-up Rings for service in extreme conditions where single or double extrusion gaps are present
  • Withstands aggressive and abrasive process media
  • Unlimited shelf life
  • Compact form and single piece installation, ideal for replacing multipiece packing and sealing systems
  • No external preload required
  • Resistant to compression set and the need for re-tightening
  • Special sizes and geometries available


Turcon® Glyd Ring® T advantages and benefits:

  • High sealing efficiency with low wear and long service life
  • High operational reliability with low friction and stickslip-free operation
  • Simple groove design suitable for easy installation even in narrow grooves
  • Design flexibility – adaptable for almost all groove sizes
  • Custom designs available
  • Bi-directional seal
  • Very good static leak-tightness
  • Increased clearance possible of approximately 50 percent, depending on the operating conditions


LB Bentley is based in Stroud, England, and introduced the now standard subsea rotary gate valve into the market in 1998. Since then, the gate valve has gained universal acceptance throughout the industry and has become the product of choice globally, with many customers preferring and trusting this design over traditional needle, ball and slab type gate valve designs.

With an unparalleled experience in the design and manufacture of rotary gate valves, together with a simplicity of operation, LB Bentley’s gate valves have  been proven to be hugely reliable in service. A wide range of sizes, pressures, materials and interfaces are available from 3/8 inch through to 1 inch nominal bore, up to 15,000psi (1,034 bar) in both FF and HH trims.

Designs are qualified to API 6A 20th Edition and API 17D 2nd Edition for the temperature range -29 °C to +150 °C, to a water depth of 10,000 feet. The innovative Medium Duty Rotary Gate Valve, developed with the support of Trelleborg Sealing Solutions, incorporates minimal moving parts and an efficient quarter-turn mechanism that is ope rated manually. It exceeds the requirements of the two key industry standards of API6A and API 17D