New hydraulics for linkspan bridges in the ports of Western Scotland

Armada Engineering were appointed by international engineering consultants Royal Haskoning DHV to provide consultancy and bespoke design for a new hydraulic system. This was required for the linkspan bridges used by the ferries in 15 ports in Western Scotland and the Western Isles. These ports are operated by Caledonian Maritime Assets Ltd (CMAL).

The ferries dock against the linkspan bridges which move up and down, allowing vehicles to load and unload, powered by hydraulics.

The system needed renewal and Armada Engineering were asked to come up with a solution that would work across the 15 sites, taking into account their unique geographical factors.

Initially, Armada Engineering visited some of the sites, in order to assess the requirements in full and provided a consultancy recommendation for a package that met the brief.

The principal differences between the existing HPUs and the proposed new ones were:

• Operation of the linkspan bridge (Up/Down) was to be by electrical, momentary pushbutton rather than by manual control. Operation by manual control was subject to abuse by the operators who could jam the mechanical control levers to avoid continuously holding them. A mechanical override was required in the event of control system failure. The diesel unit controls would continue to be manual.
• All the HPUs for all locations were to be the same. The pumps used on the electric units to be the same as those used on the diesel units. Parts were to be interchangeable as far as possible between the two units.
• A new electrical control panel/operating panel was to be located at the front of the electric HPU which would contain all the electrical components required.
• Greater environmental protection to was be provided to reduce the adverse effects of seawater on the components of the HPUs.

This project then proceeded to Armada Engineering designing a prototype which the team subsequently installed for testing in the port of Oban. The new system had to be designed to take account of all the new legislative requirements regarding safe operation and be able to fit into the ‘footprint’ of the existing equipment that it was replacing.

Following successful testing of the prototype, Armada Engineering developed final designs for the new hydraulic system, which could work in effectively in each of the required locations.

Project Engineer Murray Walker says: “This project allowed us to use our consultancy and bespoke design skills to come up with a design that has proven to be highly successful in use in this harsh and remote environment.”