Oil-film bearing oil — steel mill

Oil-film bearing oil on a steel mill had taken in a heavy water load before the unit was started. In a bearing circuit water is not a contamination problem in the ordinary sense: it destroys the film the bearing runs on, and a bearing that loses its film is a bearing that is being rebuilt. The oil could not simply be dumped either -- the charge was large, and the mill needed the stand back in service.

A single nano ultra-clean screening unit was trialled on the circuit in September 2020, treating the oil in the reservoir rather than in a tanker. The unit separates free and emulsified water under vacuum and takes the particulate out at the membrane, so the water leaves as water and the oil stays where it is needed. Running it on the circuit meant the mill could keep producing while the water came out.

Two hundred litres of water came out on the day the unit was started. A second ingress followed, and over a tonne was drawn off across six days. The oil stayed in the bearing circuit throughout, which is the part that matters: the water left, the oil did not, and no charge was written off.