Grease Thief® – a practical description of the method

Grease Thief® – a source of knowledge about lubricant condition

Contrary to appearances, this will not be a crime story about grease theft, as the title of this article might suggest. This will be a short tour of the truly forensic research capabilities of lubricant testing, using Grease Thief® technology – lubricant analysis in the modern era.

Lubricant analyses (analogous to blood tests in humans) have been providing information on lubricant condition for more than a century, and for decades have been widely and effectively reporting on equipment condition. They are an indispensable and undeniable tool to support maintenance, optimization of lubricant selection, optimization of lubrication operations, etc. The general awareness of oil testing is quite broad, lubricant testing still seems to be underestimated, which is a common mistake, as the opportunities and benefits of this field continue to grow.

the foundation of the Grease Thief® method

Grease Thief® technology was developed and patented by Richard Wurzbach, a world-class expert in the fields of lubrication and tribology and owner of MRG Laboratories. Grease Thief® is not just testing, but the entire philosophy of the diagnostic process starting with sampling and ending with the proper interpretation of the results.

The premise of the method: meticulous collection and preparation of a grease sample in a way that ensures reproducible, representative results. The key to achieving the above is the eponymous Grease Thief® – a special sampler and, at the same time, an element used in the course of a laboratory test. The end result of the whole process is only as good as the weakest link in the whole system. Therefore, the beginning, i.e. sampling, is always crucial.

Grease Thief® technology is meticulously implemented in the standardization of sampling described in ASTM D7718 (Standard Practice for Obtaining In-Service Samples of Lubricating Grease), which describes the methodology for in-service lubricant sampling from, among other things:

• gears
• framed bearings
• electric motors
• open bearing motors
• open gears
• valve control elements
• Components lubricated with grease after a failure occurs

Testing with the GTA – Grease Thief Analyser® is the only method in the world that allows a number of remarkable determinations to be made from a grease sample weighing as little as 1g. All determinations are standardized to ASTM D7918 (Standard Test Method for Measuring Flow Properties and Evaluating Wear, Contamination and Oxidation Properties of Lubricating Grease by Matrix Extrusion and Preparation).

sampling process

The GTA apparatus makes it possible to perform a unique lubricant consistency profile test. It is the only test in the world that determines the consistency of a lubricant under dynamic conditions. It involves measuring the force used to extrude a sample through a die, from a Grease Thief® sampler over three dynamic cycles.

The result of the test may indicate excessive stiffening or softening of the lubricant, which is important diagnostic information for assessing its condition. It should be added that for a complete interpretation of the results, the laboratory should have reference (fresh) samples of the analyzed lubricants.

As a result of the test described above, we obtain a sample in the form of a thin film on a plastic substrate (so-called grease ribbon). Thanks to an advanced registration system and developed calculation algorithms, GTA makes it possible to classify the degree of lubricant contamination by determining the concentration of particles (in mg/g in sizes >10 µm, >25 µm, >80µm) and the percentage characterization of particles with sizes >25µm in terms of formation processes (e.g., abrasive wear, adhesive wear, fibers).

In addition, the color of the grease is measured, the change in which with respect to the reference grease allows assessment of the degree of its degradation, as well as the concentration of ferromagnetic particles defined in ppm as the FerroQ parameter.

After consistency profile and grease purity tests, the resulting “ribbon” of grease on the segmented substrate always provides equally prepared, identical portions of grease that can be subjected to further tests, such as ICP or RDE (OES) elemental testing, FTIR spectrum testing, Karl Fischer water content testing or RULER antioxidant testing. The juxtaposition of the above-mentioned analyses gives a complete statement of the Degree of lubricant aging (oxidation), contamination, mixing with other lubricant and wear concentration.

In summary, proper lubricant intake and proper lubricant testing are the solution to increase fleet reliability, contribute to stopping unexpected damage/failures, identify impending problems and the ability to intervene to correct potential problems before serious damage occurs. Grease Thief® technology provides the ability to perform reproducible and representative laboratory tests over a wide range, using as little as 1g of grease.

Properly supervised process of analysis enables optimization of lubrication activities and optimization of lubricant consumption and globally results in reduction of production costs and improvement of equipment availability.

potential areas of application

The potential application areas for GTA lubricant testing are virtually unlimited and are intended for, among other things:

• Pharmaceutical industry (production and research)
• Diagnostics of drives and joints of industrial robots (all production lines, such as automotive, household appliances, logistics, electronics)
• Wind power industry (diagnosis of main bearings, blades, generator, pitch and yaw drives), testing of electric motors, valve drives (in nuclear power, mining, and petrochemical industries)
• offshore industry
• arms industry
• food processing industry
• lubricant manufacturing industry – as part of quality control

Tests can be performed on the only such advanced Grease Thief Analyser® in Europe, at Ecol Sp z o.o. of Rybnik. Above and beyond research, Ecol offers training, consulting and support for any eventuality related to the subject of testing and diagnosis of all types of lubricants (lubricating oils, hydraulic oils, electro-insulating oils, etc.) and services within the broadly defined lubricant management.

While we are used to being afraid of thieves, which is quite right in principle, in the case of Grease Thief® we can rest easy while it works. Machine diagnostics has gained a modern tool that can protect more than one piece of equipment and even entire production lines from failure and unplanned downtime.