Load bearing

A custom-designed set of maintenance-free spherical plain bearings are providing additional support to the main offshore platform located in the North Sea.

The bearings were created by Shaeffler UK to support a newly constructed process module extension column which is fixed to the platform.

They provide a flexible support between the mono column and main rig, says Shaeffler, allowing for movement of the column caused by waves and tidal current relative to the main rig.

With a bore diameter of one meter, the bearings are designed to transfer these loads from the column to the main rig.

“After several meetings with the customer and its main contractor for the extension column, it was clear to us that the customer would require a unique design of bearing that offered both a very high level of reliability and zero maintenance,” says Chris Head, application engineer at Schaeffler UK.

“We therefore proposed Schaeffler’s range of ELGES spherical plain bearings, but customised with extra sealing features and low friction sliding layers. These would ensure maximum reliability and zero maintenance.”

Schaeffler’s standard ELGES spherical plain bearing is fitted with only one seal on each side of the bearing, so a special sealing arrangement was discussed with the customer.

The custom bearings are therefore fitted with additional seals and designed with an extra sliding layer in the bore.

This ensures low friction when the extension column moves relative to the main rig due to the sea’s waves.

“We offered additional sealing features in the form of a grease layer, which would allow us to lubricate the outermost lip seal, added a special seal, which acts as a barrier for the grease, with another seal to prevent the grease from contaminating the bearing sliding layer,” says Head.

The bearings were manufactured according to strict customer specifications, with all bearing materials, components, manufacturing and quality processes all fully traceable.

The bearings were installed on the offshore platform extension column in May 2013.

In order to ensure that the installation of the bearings could proceed without difficulty under the challenging and constricted conditions present on an offshore platform, an installation trial was carried out.

This was performed by two experienced fitters from Schaeffler and allowed important details and the special tools required for offshore installation to be included in the work planning.

The service personnel were very experienced, says Schaeffler, having been brought into the project planning and implementation process at an early stage.

“The customer was so impressed by the professional skills displayed during the installation trial that he requested a Schaeffler fitter be present when the preliminary work was carried out on the platform, in order to support the other companies involved and to monitor their work operations,” the company says.

“This is a first for the oil and gas sector,” says Alan Stewart, regional sales manager north at Schaeffler UK.

“This project is the first one in which a process module extension column of this type is supported by bearings. The customer deemed the bearings to be a high priority on this project, as their function is absolutely critical in supporting the extension column.

“We were informed by the customer that we won this business due to our technical knowledge and expertise, and because we understood exactly what the customer required. As the bearing supplier, we successfully met all of our deadlines, helped enormously by excellent cooperation between the three main parties involved – the end customer, the construction contractor and Schaeffler.”