Above: Water damage to gear box thrust face. Black scab due to salt water ingress.
Comment
In practical terms when deciding on work priorities, onboard elimination of salt-water contamination should always be towards the top of the list.
Above: Kittiwake's water in oil DIGI kit .
Info Centre >> Fuel and Lube Oil Technical Manual >> 7. Lube Oil - Test Results >> 7.4 Enclosed Gears >> 7.4.2 Water
Water Contamination of Gear Oils and Lubricants
The two most important contaminants for gear oils are water (fresh or salt) and engine lubricants that can upset demulsification properties of the oil. The combination of both will of course present the risk of stable emulsions of oil and water being formed. This can cause a variety of problems, the more important of which may be:
When interpreting analysis data on water content in gear oil systems, the key points to bear in mind will be that water will adversely affect oil film conditions. Effects on oil film conditions are likely to be more significant as loading at gear contact surfaces increases.
Where the contamination is sea water, additional problems are potentially created. Sea water is likely to be very much more aggressive than freshwater with respect to corrosion at all bright metal surfaces (gear/bearings). Corrosive activity associated with sea water contamination is likely to be pervasive and continue to take place when machinery is shut down. It is possible that corrosion rates could increase when oil drains down from exposed internal bare metal surfaces.