Rotaflow Makes CALM Buoy SPM Swivel

Rotaflow was recently contracted by Rhizome Energy Ltd to produce a retrofit Single Point Mooring (SPM) swivel for an existing Catenary Anchor Leg Mooring (CALM) buoy.

The pipeline retrieves crude oil via the CALM buoy to FSO (Floating Storage and Offloading) mooring system. The project required the existing unit, housed within the buoy, to be replaced with a modified and newly designed smaller siwivel in order to accommodate it’s new purpose. Rotaflow’s scope was to design, fabricate, manufacture, assemble and test the unit ready for despatch.

With a tight schedule and well defined project requirements the design was finalised with the minimum number of iterations. All meetings were virtual or by phone. The Factory Acceptance Test was the first time Rotaflow, Rhizome and ABS met face to face (socially distanced – of course).

Rotaflow’s setup means fast turnaround is possible – 8 weeks from PO to despatch!

The swivel, built and surveyed to ABS SPM rules was manufactured and tested within 8 weeks from receipt of the purchase order to despatch of the swivel. This fast turnaround is possible thanks to the experience of the Rotaflow design team and the close proximity between the design and engineering departments of the company.

The Swivel Joint is 6" (DN 150) nominal bore with ASME 150lb flanges. Rated to 285 PSI (19.6 Bar) in duplex stainless steel. This material was chosen to cope with the atmospheric conditions the swivel will be exposed to whilst out at sea. The duplex stainless steel is particularly strong and resistant to corrosion.

The unit is set to be deployed in the Indian ocean, so we can expect high temperatures, long-term sun and salt exposure, rough seas and constant use through round the clock operations. Having worked in oil and gas for decades, the Rotaflow engineers understand exactly how a swivel working in this environment needs to be designed and built to cope with these conditions. The twin taper roller bearing arrangement brings huge bending, radial and axial load capacity. The design will allow the swivel to maintain operations and structural integrity during expected stormy seas.

With twin PTFE main seals, the fluid compatibility is virtually unlimited, the second seal allowing for a monitored leak path in between. Should the main seal fail, the leak port can be closed, and the secondary seal will allow continued operation whilst maintenance is scheduled.

Easy maintenance considered in the design

The seals will give many years of constant operation, but should seal replacement be required, the seal housing can be removed, and seals replaced without disturbing the bearing. This makes the process of maintenance much more straightforward and allows the system to be back up and running in the minimum amount of time – important features to allow continuous production.

This is an example of the forward-thinking innovation employed by Rotaflow. In a world where there’s a march towards greener working practices. A significant part of the business is now in refurbishment and recycling of systems, rather than outright replacement. It means we can extend the lifespan of equipment and save the customer money in the process.