We’re experts in designing and manufacturing safety critical assets, which is why we were recently contacted by an offshore oil & gas operator who needed to ensure the structural integrity of their offshore asset.

What happened?

After suffering some operational issues, our client had concerns over the structural integrity of an offshore caisson; should the caisson in question fail there were no support structures in place to prevent it from falling onto the seabed and causing significant asset damage. As a precautionary measure the client needed a solution to allow them to mechanically clamp the caisson so that in the event of a critical failure the load would be secured.

What did we do?

The SengS engineering team designed a bespoke clamp that would be pinned in place on the exterior of the caisson. We carried out rigorous engineering analysis to calculate the peak loads that the clamp would be subjected to, to understand if there was a failure point. The clamp was able to withstand the full caisson load. Once the load analysis was completed the engineering team then had to design a bespoke clamp suitable for this application.

Challenges

The biggest challenge to overcome on this project was developing a methodology for installation, the caisson was already installed subsea and was within one of the guide structures making access difficult. We soon deduced that the clamp would need to be installed by a diver and therefore when designing the clamp we realized that despite the clamp needing to be able to withstand high loads, it also needed to be compact enough to be carried and could not require any complex assembly subsea.

In addition to the already complex installation requirements, the divers would need to drill through the caisson to secure the pins on the new clamp. We needed to ensure both holes at either side were concentric and true to one another to ensure the pin would align and pass from one side all the way through the caisson to the hole on the opposite side.

The outcome

We brainstormed multiple concepts to find a suitable solution, the final design comprised of a one piece hinged clamp which contained all bolting and fixing screws within the design so no loose objects could be dropped or lost during installation.

At our facility in Ellon, Aberdeen, we have a host of specialist environmental testing facilities, including a large, submerged test pit. We simulated the subsea environment to conduct trials of different drilling methods, ensuring an accurate representation of the offshore installation, in doing this we were able to make alterations to the clamp to make installation easier. Bespoke mounting plates were designed for the drilling equipment which ensured ease of use for the divers to install but also ensured accuracy and repeatability for the hole positioning.  

On the successful completion of the trials and training, we were approached by the installation contractor to supply the back deck equipment needed for the installation, this included: hydraulic power units, downlines, reelers, subsea drills, rigging and handling equipment. We sourced all the equipment either from stock or on a rental bases from local supply chain and project managed the installation equipment needed by the installation contractor.

We were delighted to deliver this project on time and in budget and were delighted to receive positive feedback from our client on completion of the installation.

This was a great project for SengS, one that drew on the vast experience and expertise in our business.