Stromag clutches ensure reliable torque transmission for marine gearbox in large ferry

When a major Chinese manufacturer of marine propulsion systems needed a robust clutch to integrate into a roll-on-roll-off ferry gearbox, it turned to Stromag for a compact, high performance, low maintenance solution.

Stromag supplied Model KMS 18000/25 clutches which were integrated and adapted into the gearboxes.

Large ferries commonly use a dual diesel-powered propeller shaft propulsion, with four diesel engines driving two propeller shafts. In this arrangement, there are twin diesel engines connected to a common gearbox for each shaft.

The gearboxes reduce the medium shaft speed from the engine down to the low-speed drive required for the propeller. The two engines per gearbox are each connected via a clutch, which enables engagement/disengagement to allow either one or both engines to be run as needed, and facilitates reversing of the engine. The application is very demanding on the clutch, which must be compact enough to be integrated into the tight space yet still transmit the required high torques.

A low maintenance and high reliability solution is also important, with ferries typically running to tight schedules and the cost of unplanned downtime being high. The productivity of these vessels is ultimately dependent on the good working condition of the propulsion system – any failure within the propulsion system can impact on speed and manoeuvrability, disrupting the vessel’s schedule and leading to significant commercial losses.

For a major Chinese marine propulsion system manufacturer, developing a suitable gearbox/clutch power transmission combination for a large ferry application was proving a particular challenge. The roll-on-roll-off ferry transports wheeled cargo/vehicles in an enclosed lower deck, while passengers travel on an upper deck, and the size of the vessel demanded a high torque transmission yet in a very compact package, putting especially high stresses on the clutch.

Having investigated and evaluated clutch designs from several manufacturers and found them wanting, the Chinese OEM turned to Stromag, recognising its reputation for quality, responsiveness and cost-effectiveness.

Renowned within the marine industry for extra heavy-duty clutches that are characterised by a high power density in a small mounting space, Stromag is a leading engineering partner for marine gear manufacturers around the world. A brand of Altra Industrial Motion Corp., a leading global supplier of power transmission equipment, Stromag has over eight decades experience in the development of multi-disc couplings.



Large ferries commonly use a dual diesel-powered propeller shaft propulsion, with four diesel engines driving two propeller shafts.

For this application, wet-running multi-disc KMS clutches were specified, being specifically designed for use in marine gearboxes. The oil-cooled, hydraulically-operated units are used where high torques must be transmitted reliably in tight engine room spaces. The clutches have an excellent torque-to-weight ratio and low mass moment of inertia. Units feature a high thermal capacity since switching heat is dissipated by internal oil cooling.

Stromag supplied Model KMS 18000/25 clutches which were integrated and adapted into the gearboxes. Each 635 mm diameter clutch has a torque rating of 240,000 Nm. Along with meeting the performance requirements and providing a high-reliability solution, all KMS models are also low maintenance, as any disc wear is automatically compensated by piston travel. Further, they offer a long disc service life.

Stromag has the capability to deliver KMS clutches and technical expertise worldwide. This ensures any shipbuilder or marine propulsion OEM can specify an optimal marine clutch suitable for multiple vessel classes, designed to promote reliability.

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