Improved fairlead bearings offshore rigs
Fairleads must be in a good condition on behalf of the durability of anchor chains and the safety and integrity of rig and crew. With traditional self-lubricating metal bearings, it is a major challenge to retain all mechanical parts in a good state and functioning as required.
Due to their location on the outside of rigs and often below sea level, maintenance of fairleads offshore is virtually impossible.
Traditional fairlead bearing are made of bronze, a material with limited sea water resistance, a cause of corrosion of surrounding steel parts and a material with an unpredictable wear life when used unlubricated. For reliable usage, regular inspections and, when necessary, replacement are adamant. The relatively high bearing friction results in more wear of sheave pockets and anchor chain.
Risks and consequences
Bearing wear causes more friction which leads to increased sheave and pocket wear. Worn out bearings can cause fairlead sheave seizure, which can ultimately result in anchor chain failure.
The bronze bearings of the fairleads of a large number of Transocean, Diamond and other rigs, have been replaced by wear resistant D-glide bearings. These bearings are strong, durable and require no maintenance at all. Friction is very low, which is beneficial for the fairleader itself as well as for the anchor chain.