A 4.7-ton Special Bearing for the Dredger

Schaeffler produced a special bearing with a weight of 4.7 tons and an outside diameter of 1,900 millimeters. For the largest spherical plain bearing in the company’s history, inner and outer rings were produced with a single-piece design in order to withstand the high shock loads of a cutter suction dredger.

by Elena Magistretti

Schaeffler has produced the largest spherical plain bearing in the company’s history to date. This special bearing weighs in at around 4.7 tons and has an outside diameter of 1,900 millimeters, a bore diameter of 1,500 millimeters, and a height of 600 millimeters. The bearing will be used on a cutter suction dredger that was designed and built by Royal IHC, a Dutch company that specializes in equipment, vessels, and services for the offshore, dredging, and wet mining markets.

An application featuring harsh operating conditions
A cutter suction dredger is a working ship either with or without its own drive that removes solid material from the bottom of the body of water. A vacuum is used to lift stones and transport them to shore, e.g. using floating pipelines. Particular strain is placed here on the connection between the pipeline and the ship, which is implemented via a spherical plain bearing that is mounted on the hull and supports the rotary motions that take place between the hull and the pipeline. On the basis of these requirements, a special bearing was designed specifically for the application.
Thanks to the close collaboration with Royal IHC, it was possible to produce the bearing according to the customer’s requirements in a record time of just three months.
Designing the special bearing was not the only major challenge faced by Schaeffler’s experts here; producing it was also highly demanding. The shock loads that occur in the application meant that the inner and outer rings had to be implemented in a single-piece design.
High operational reliability with a low maintenance outlay
The bearing has to eliminate the edge stresses that occur and support large forces according to its dimensions. Because the forces only act unilaterally on the spherical plain bearing, it was designed asymmetrically, making important savings possible in terms of space and weight.
To ensure a long operating life and low levels of wear, Schaeffler created a special system of lubrication grooves, which are designed in such a way that the grease is evenly distributed even during small swivelling motions of around 20 degrees, thus ensuring optimum lubrication.
Because the operating conditions found in offshore applications also require special protection against corrosion and optimal sliding conditions, the sliding surfaces of the bearing were coated with Durotect P, a proven lubricating varnish, which ensures that no metallic contact occurs between the inner and outer rings, even in the event of insufficient lubrication. Lubrication with grease also means that the bearing is protected against corrosion. This ensures a combination of high operational reliability and low maintenance outlay for the customer.