Initiated following discussions with representatives of the port industry and evaluation of various available technologies, the Rosafe programme is being overseen by technical inspection body TUV and involves experts from both project partners, in Britain, Germany and the Netherlands. Royal Haskoning has expertise in the design and planning of ro-ro terminals through UK arm Posford Haskoning while Bosch Rexroth contributes hydraulics research, development and manufacturing expertise.

Posford Haskoning was closely involved in the preparation of ISO specifications for ro-ro ship to shore connection and was recently commissioned by UK construction industry research association CIRIA to prepare a report on the safety of linkspans and walkways, which identified a need to protect the movable structure from catastrophic failure of the supporting and lifting system. As a result of new risk analysis regulations and a fresh approach to linkspan safety issues, the design and operation of this equipment is being reviewed by the industry, particularly focusing on the need for duplication of the hydraulic or wire rope lifting mechanisms.

Bosch Rexroth and Posford Haskoning concluded that an independent safety device was the optimum solution and drew up a number of key criteria for its design. Among these were failsafe operation and the ability to immediately arrest uncontrolled movement then enable reinstatement of the structure to its original position.

The resulting new Rosafe is essentially a hydraulically operated linear brake running on its own supporting rod, an up to date adaptation of a following system which works alongside the main equipment such as hydraulic cylinders or winches but unlike wire rope devices, it does not need replacement after activation and reverts to normal service immediately. It consists of a spring-applied cone brake assembly which is hydraulically released and floats within a sealed chamber, itself pressurised with hydraulic fluid to absorb the dynamic forces derived from emergency operation. The body is gimbal mounted to the main lifting structure and guide bearings at the top and bottom enable free movement up and down the rod.

The Rosafe incorporates a self-contained hydraulic power pack, complete with Rexroth fixed displacement pump, electric motor, control manifold, logic valves and accumulator for releasing the brake and charging the chamber and has its own independent control system for initiating operation and monitoring position. The cylindrical rod features a ceramic coating to withstand aggressive environmental conditions and Rexroth's latest CIMS measuring system for precise positioning, with articulated mounting to follow the movement of the linkspan or walkway when connected to a floating ship.

Normally installed in pairs or singly on lighter walkways with sufficient torsional stiffness, the Rosafe follows routine movement of the lifting equipment in either direction but its sensors detect abnormal downward movement within milliseconds and initiate operation of the brake.

When movement has ceased, the hyraulic power unit can reinstate the brake body to the pre-fall position whilst maintaining 'brake on' status.

This enables continued use of the linkspan or walkway for a limited period following failure of the lifting equipment to allow disembarkation of vehicles and passengers. Rosafe can be activated at any time for supporting the equipment in the parking/maintenance position during normal operation, which also means the device can be routinely tested and verified.

Available in incremental loading capacities from 50 tonnes upwards, the Rosafe is suitable for use alongside most new and existing lifting type ro-ro connections and also serves as a useful upgrade for ageing spragging and position monitoring systems.

MJ Information No: 17329