Developing revolutionary subsea product

It was designed to deliver radically improved vessel safety, reduce environmental risk and decrease costs by greatly boosting a vessel’s operating window.  

STL had previously developed small bore retractable couplers, used as sub-components in its unique XR Connector, however, scaling up to a large two inch bore to allow for choke and kill lines passing through, posed a number of major challenges.

In order for the full potential and functionality of the two-inch coupler to work, it needed a seal to be developed that would work in harmony with the coupler, the world’s first of that size, with a hydraulically retractable element.

Trelleborg set about meeting requirements and developed custom versions of its Turcon Captive Glyd Ring with XploR V9T82 elastomer material and Turcon Stepseal 2A CR with PEEK corner reinforcement rings.

The Turcon Stepseal 2A CR is a new standard corner reinforced rod/piston seal for single-acting use and has many advantages, such as its anti-tilt design and that the dimensions of the seal body and corner reinforcement ring can be modified to facilitate installation.

Andrew Longdon, Technical Manager for Trelleborg Sealing Solutions in the UK, said: “Throughout the process we constantly had to think about the safety issues and challenges that are frequently faced when working with heavy duty engagement of subsea equipment.

“We worked with STL as the team conducted a very lengthy test programme including a full PR-2 temperature and pressure cycling programme along with endurance cycle testing on the products in accordance with the ISO 10423 standard.

“STL also conducted two disconnects with 10,000 psi bore pressure. This was all completed with one set of seals, which I think is some achievement.

“We pride ourselves on innovation and relished this opportunity to work with STL in a bid to find an effective sealing solution and ensure the two inch Hydraulically Retractable Subsea Coupler was working to its full capability.”

Not only does the coupler provide new opportunities for remote emergency release system designs for subsea applications, it also enables people to be removed from stab plate engagement functions on the surface.

By being hydraulically retractable, it allows the heavy duty engagement of equipment both on surface and subsea to be separated from the comparatively delicate engagement of control system interfaces.

STL’s Managing Director Drummond Lawson said: “We knew Trelleborg would be able to solve the challenge of finding a durable and robust seal to work in harmony with our product.

“Not only have they gone above and beyond in meeting expectations of the brief we outlined, but we were also impressed with the service we received throughout the process. We are by no means Trelleborg’s biggest client – but the support we received has been second to none. At every stage of the process a member of the Trelleborg team kept us fully informed from prototype development right through to bringing the product to market.

“This was no easy challenge and without Trelleborg, we would not have been able to produce what we believe to be the first coupler of this size ever to be made with a hydraulically retractable element, which we are certain will create opportunities for our clients beyond just its use in our XR Connector.”

The coupler is fully Lloyds design verified and qualified to 3,000m (10,000ft) water depth, rated to 10,000psi hydraulic bore pressure and up to 5,000psi hydraulic function pressure.