The brake is installed in a cylinder incorporating within it an independent piston rod. The rod is allowed to move freely within the brake until there's an emergency. When there is sudden downward movement, sensors detect this abnormal circumstance and apply the brake immediately. Damping minimises shock loads appropriate to the structure.

Importantly, the brake can also be used to lock/sprag a linkspan into any position, for example when extended maintenance work on the structure is needed.

The device meets the criteria of recent standards for linkspan and walkway safety, and Posford Haskoning said it expects to see the device used in preference to the doubling-up of cylinders, winches and the like. The company says RoSafe is able to 'match or better' the safety performance of these methods, fully satisfying the requirements of new legislation.

It also does so in a much more cost-effective manner.

Rosafe is normally installed in pairs, or singly on lighter walkways with sufficient torsional stiffness.

Available in incremental capacities between 50 and 500 tonnes, RoSafe has its own hydraulic power pack and controls, and is fully independent of normal lifting equipment.

A lifting system for a typical 300 tonne, single ramp linkspan, with a four cylinder system (two per side) including hydraulic power unit, electrical control system and installation, would cost around £250,000. A similar two cylinder system, incorporating two RoSafe devices (one cylinder plus one RoSafe per side) would cost around £275,000, but would bring additional benefits of 100 per cent full redundancy and live safe loading of the ship, without the requirement for mechanical spragging. RoSafe could also be incorporated into the cylinder bodies of a two cylinder system (one combined cylinder/RoSafe per side), which would bring a 20-30 per cent cost saving against the four cylinder system.

The RoSafe development programme was overseen by technical inspection body TUV and the first production prototypes have already been demonstrated to Lloyds Register, the UK Health & Safety Executive, and BSI consultants in Germany.