The two winches, one port and one starboard, are used to control towing of the paravanes which control the in-water spread of seismic acquisition equipment. Eight hydrophone streamer cables up to 8km long are towed from deck level using a special fibre rope. Each winch has a 1.7m diameter, 200mm wide cast brake drum, both of which had hardened and scored. The hardness ruled out single point tooling and metal deposition while machining was not an option due to the composition of the base material.

Once on board, the Metalock team set up one of their portable grinding units, supported on a special framework to ensure that the grinding machine and drum centrelines were on a common datum to assure optimum finish. The drum was revolved slowly using winch hydraulic drives. Two two-man Metalock teams worked round the clock for two days removing 4mm of diameter from each drum and cleaning up the surfaces.

While this work was progressing, Veritas fitted thicker new braking materials to the brake bands to compensate for the slightly smaller drum diameters and restore original clearances. When reassembled, the winch brakes were checked and found to be ‘good as new’. The work had been carried out at a fraction of the cost of replacement and within the time frame and budget allocated.

MJ Information No: 19329