The project required the replacement of two ship sets of gantry cranes and the supply of a bespoke anti-collision system, all for use in the handling of weapons, explosives and ammunition to and from landing craft within the vessels’ well docks; an area at the stern of the ship which lowers into the water to allow the landing craft to enter.
Budget restrictions called for a cost-effective solution, capable of overcoming the tilt of the well-dock and withstanding potentially turbulent ocean conditions, and which would meet all the necessary safety standards for the handling of munitions.
The two 4.5-tonne cranes are constructed from a number of extensively refurbished gantry cranes from the aircraft carrier HMS Ark Royal in order to keep costs down, whilst still meeting the stringent requirements of the MoD Tri-Services JSP 467 standard for the safe handling of weapons, ammunition and explosives, and are believed to have been the first of their type to do so.
A special protective coating protects against the harsh marine environment and prolongs service life. Parts that can’t be painted, such as the wheels, are stainless steel.
Rack and pinion systems across both the long and cross travel prevent unwanted movement during operation, as the ship displaces with the motion of the sea. Anti-tip brackets and a mechanical storm anchor lock the cranes in position during adverse weather conditions and secondary brakes on all motions ensure optimum safety at all times. Load cells prevent overloading, and the hoist is fitted with over-speed brakes as requested by the MoD.
The gantry beams are built at an angle of 1° to the horizontal to allow for tilt during docking down for landing craft entry, providing constant headroom and allowing for safe operation of the crane. Sliding and pivoting bearings accommodate any misalignment of the existing gantries and allow travel across the change in angle.
Crawl-ways provide safe access to manual recovery winches which enable the retrieval of the crane in the event of a power failure or breakdown. A walkway across the full span of the crane provides safe access for maintenance.