Detecting Moisture Problems in Petroleum Products

Petroleum products constantly face problems due to the presence of moisture, which can cause expensive system components to wear out prematurely by negatively affecting the efficiency of lubricants. Therefore, moisture content analysis is essential to detect moisture problems in advance, allowing for proper maintenance of oil systems.

Moisture Problems

There are several ways by which moisture can enter an oil system. The easiest way is during the process of addition or replacement of oil and/or filters. Moisture can enter in large quantities even in a closed oil system through condensation in oil and filter storage.

Depending on temperature and humidity, moisture will be absorbed by oil from humid air. The accumulation of water in oil as a result of oxidation or combustion reaction is another possibility. Even systems that are carefully maintained are susceptible to moisture contamination.

All oils have a saturation point at which they can hold a prescribed amount of dissolved moisture. This saturation point differs with the presence of additives in the oil, as the water identifies the polar molecules to collect around. The moisture presence in oil is visible only after meeting the saturation point, as a layer in the oil or as an emulsion.

Effects of Moisture Presence on Oil Systems

The presence of water affects oil systems in a number of ways. Premature bearing wear is a typical problem, due to a reduction in oil viscosity caused by the presence of large amounts of moisture.

It is also believed that moisture causes degradation by stripping hydrogen from the metal subsequent to its absorption into tiny fissures in the bearings. Bearing life can be significantly affected even if a trace amount of moisture is present in it (Figure 1).

Effect of Water in Oil on Bearing Life.

Figure 1. Effect of Water in Oil on Bearing Life.

Moisture in trace quantities can also affect the purpose of certain additives in oil systems, especially oxidation inhibitors, because of the attraction of water molecules towards polar molecules in a system. This action can decrease the efficiency of any polar additives. Hydrolysis reactions with additives generate some byproducts, which can be lead to the accumulation of sludge, varnish, and acids. This condition can clog filters prematurely.


To address the moisture problems in oil systems, Arizona Instrument has developed the Computrac® Vapor Pro® Fx Moisture Specific Analyzer, which can determine moisture in most petroleum products rapidly and easily.

The device is approved for use with ASTM D7546-09 to determine moisture in lubricating oils, with a range from 100% moisture down to 10ppm.


Arizona Instrument

This information has been sourced, reviewed and adapted from materials provided by AMETEK Brookfield Arizona

For more information on this source, please visit AMETEK Brookfield Arizona


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