LB Bentley is a specialist in creating small bore valves for subsea applications. Since it introduced the now standard subsea rotary gate valve into the market in 1998, the gate valve has gained universal acceptance throughout the industry. This component is now used globally with many customers preferring this design over traditional needle, ball and slab type gate valve designs.
As subsea oil and gas exploration becomes even more challenging, the company realized a highly specialized gate valve that met a wide range of extreme working pressures and operating conditions was needed. Meeting these development challenges led to the new Medium-Duty Rotary Gate Valve.
To meet this application’s requirements, Trelleborg Sealing Solutions 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. To facilitate subsea use, Trelleborg’s Turcon Glyd Ring T was selected as a contaminant exclusion seal.
Throughout the development process, the Trelleborg team had to consider safety issues and challenges inherent in vital subsea equipment applications. For LB Bentley the qualification status of its products is continuously developing, but this allows the company to offer an expanding range of fully qualified products, including the Medium-Duty Rotary Gate Valve that Trelleborg has helped develop.
The Medium-Duty Rotary Gate Valve uses minimal moving parts and an efficient quarter-turn mechanism that is operated manually. It exceeds the requirements of the two key industry standards of API6A and API 17D. The two seals used in the gate valve are Turcon Variseal MC and Turcon Glyd Ring T.
Turcon Variseal MC 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 PTFE based material seal profile. The single-piece design improves sealing integrity and leak tightness in high-pressure applications by providing higher contact force across multiple seal hardware interfaces.
Turcon Glyd Ring T is recommended for double-acting sealing for hydraulic components and is particularly suited to heavy duty and large diameter applications. Within the seal, both lateral profile flanks are inclined so that the seal profile tapers toward the seal surface. It can retain the typically robust and compact form of piston seals without losing any of the flexibility required to achieve a pressure-related maximum compression.
The edge angle created by the cross-sectional form of Turcon Glyd Ring T permits an additional degree of freedom of movement and enables slight tilting of the seal; the maximum compression is always shifted toward the area of the seal edge directly exposed to the pressure. On the lower-pressure edge of the seal, the Glyd Ring T exhibits only zones with neutral strains without compressive or shearing loads. This design reduces the danger of gap extrusion.