ASTM International Committee D02 on Petroleum Products and Lubricants has approved a new ASTM method which covers the determination of moisture content in new and in-service lubricants and additives by relative humidity sensor. The standard, ASTM D 7546, offers users an alternative to moisture testing by Karl Fischer titration, or the less quantitative “crackle test”. Determination of moisture content in lubricants is important as the presence of water, even at low levels, can:

·        Reduce the efficacy and useable lifetime of lubricant additives, especially at elevated temperatures

·        Contribute to premature corrosion and wear of bearings

·        Support undesirable bacterial growth

·        Reduce the load carrying ability of the lubricant

·        React with the lubricant and some additives to form undesirable by-products (varnish, sludge, organic and inorganic acids).


On a side note, the Computrac Vapor Pro Fx is currently the only instrument that conforms to the unique specifications of ASTM D 7546. The moisture specific sensor in the Vapor Pro works without the need for solvents or specialty chemicals. It is not affected by organic volatiles, or compounds that can bias the moisture determination results from Karl Fischer titration such as mercaptans and hydrogen sulfide. The Computrac Fx can detect moisture at levels as low as 10 ppm in most lubricants.