Quantifying varnish removal in lubricated systems

In lubricated systems, varnish and deposits can form on metal surfaces as lubricant oils degrade, often leading to inefficient operations and equipment failure. There are many chemical cleaning products to break down varnish, but the effectiveness of these compounds in a particular system is difficult to quantify. To aid in selecting appropriate varnish-removing solutions for a particular application, Chevron Lubricants (San Ramon, Calif.; www.chevronlubricants.com) has partnered with the University of California at Merced (www.ucmerced.edu) to develop one of the industry’s first testing systems designed to study and compare the varnish removal efficiency of chemical cleaners.

The new test module includes an oil circulation unit, an imaging system and an image-analysis algorithm, which enables quantitative evaluation of varnish removal efficacy for chemical flushing fluids. An oil sample is heated and pumped through a specially designed test cell holding a metal plate containing a quantity of varnish film. The imaging system monitors varnish removal as the image-analysis algorithm generates corresponding data points, which are corroborated against weight measurements of the plate.

“We can study the varnish removal efficiency of chemical cleaners with different chemistries and treat rates at controlled operating conditions. Removal efficiency can be quantified as the total varnish removed over a given time or the rate of varnish removal. This approach also provides qualitative information about the varnish removal mechanisms for each cleaner using in situ videos of removal and post-test analysis of the varnish particles trapped on a downstream filter,” says Zhen Zhou, senior formulator for Chevron.

Currently, the test system uses standard testing coupons, but the team is developing a module that is capable of measuring varnish removal on irregularly shaped metal parts in the field, such as valves and bearing pads, explains Zhou. The team believes that the testing unit could also be applied in other applications involving thin films and chemical circulation in the coatings and paint industry.