LATEST DEVELOPMENTS IN STEERING SYSTEMS

Safety design of steering systems has received much closer examination since the loss of the Amoco Cadiz, culminating in proposed new SOLAS requirements that are being considered by IMCO. The reduction of drag is also being considered so as to reduce fuel consumption. Three types of steering gear are considered: Rapson slide, oscillating cylinder, and rotary vane. The basic rule agreed after the accident was that a steering gear should be capable of recovering from a single hydraulic failure within 45 s, although only 50% capability would be available. Based on this requirement it is necessary to provide either two steering gears operating on the same tiller with no interconnection, or a system where the interconnection can be closed within 45 s and before oil loss has reached a point where it is no longer possible to keep the unaffected actuators fully charged with fluid. These proposals are discussed together with two others which are not considered quite so effective.