Digi Cell Plus - Digital Oil Test Cell Information Guide
20
GB
Interpreting Results
Water
Water contamination may cause different problems in different types of lubricating oil, although corrosion is always
directly associated with water ingress. Whatever the equipment, water can displace the oil at contacting surfaces,
reducing the amount of lubrication and activating surfaces which may themselves act as catalysts for degradation of the
oil.
This is a particular problem with synthetic ester-based oils (e.g. many turbine lubes) which also react with any water
present (hydrolysis). Water in emulsified form can increase lubricant viscosity. On occasions it has caused gross instability
and dropout of the additive package. Problems will occur, whether visible or not, in any system in the presence of more
than about 0.2 % water (some systems are very intolerant to water contamination).
In highly loaded lubricated contacts, particularly where oil films are thin (for example on gear teeth), water contamination
can result in rapid failure through localised or general breakdown of oil film conditions. Alternatively, the mode of failure
could be progressive resulting from local or generalised corrosion of components within the systems and / or through
effects which impact on the functionality of the lubricant itself.
Sources
There are many potential sources of water contamination in any system including:
• leakage from oil coolers and steam heating coils
• charge air coolers
• condensation of atmospheric humidity
• blow-by gases from engine combustion spaces or past compressor ring packs
• leakage at tank vents (especially those exposed to weather)
• coolant jacket leaks through cracks or seals
• contaminated top up oil (especially in systems with a low tolerance to water)
Effects
Water is an important contaminant in all lubrication systems because of its potential to cause system failure via a number
of mechanisms. Water will:
• corrode unprotected metal surfaces
• attack bearing substrates
• cause instability of chemical additives in the lubricants
• encourage the formation of emulsions
• alter the lubricant vapour pressure
Water contamination within lubricating oil (especially crankcase and system oil) and in fuels can lead to
microbiological growth, forming yeast, mould and bacteria that will clog filters and rapidly corrode fuel systems