Grease Testing
by Micheal Blackmon, CLS
Reliability Engineer

Evaluation of grease using conventional test methodologies can be very time consuming and expensive, and can require a significantly large sample of grease. While this can be a deterrent for implementing grease analysis as part of a predictive maintenance program, technological advances have been made in this area which streamline the ability to test small samples of used grease. One such technology is the Grease Thief sampling and analysis system. Grease Thief Sampling Kits provide the ability to collect representative grease samples from wind turbines, motor-operated valves, gearboxes, pillow-block bearings, electric motors, and other grease lubricated components. The kits are designed in a manner that allows for sample collection in accordance with ASTM D7718 Standard Practice for Obtaining In-Service Samples of Lubricating Grease.

The grease testing methodology is outlined in ASTM D7918 Standard Test Method for Measurement of Flow Properties and Evaluation of Wear, Contaminants and Oxidative Properties of Lubricating Grease by Die Extrusion Method and Preparation. Up to eight tests can be performed, including:

  • Die extrusion to determine the consistency of the grease by measuring loads at various speeds as the grease is extracted through an orifice slot, then comparing to a baseline sample
  • FTIR to detect contamination and oxidation by comparing an overlay of the used grease to the new grease baseline
  • Colorimetry testing to observe appearance changes due to overheating, aging, and contamination
  • Atomic emission spectrometry to evaluate for wear metals along with additive elements and possible contaminants
  • Linear sweep voltammetry to measure antioxidant content which can give an indication of the remaining useful life left on the grease as well as assist in determining proper relubrication cycles
  • FdM+ to monitor for wear concentration by determining the amount of ferromagnetic material that is present in the sample
  • Analytical ferrography to characterize the types and sizes of wear debris that are present
  • Rheology to determine the flow characteristics of the sample.

ALS offers this grease testing which provides valuable insight into grease performance and integrity. With as little as a gram of grease, data can be provided which includes information on:

  • Wear
  • Consistency
  • Contamination
  • Oxidation properties

With the ability to collect representative grease samples and generate repeatable test data in a cost effective and timely manner, predictive maintenance programs can now be updated to include in-service grease analysis as part of their routine evaluations.

  • Optimize grease replenishment intervals
  • Determine wear trends for critical pieces of equipment
  • Detect lubricant mixing or other contamination
  • Evaluate failed grease lubricated components

In-service grease analysis will provide insight into making well-planned, cost-saving maintenance decisions which will lead to optimized asset health and reliability.

Basic and Advanced Grease Thief Sampling kits can be ordered through your ALS Tribology customer service representative. If you would like further information on ALS grease testing services please contact one of ALS Tribology’s Reliability Experts today.

You can find additional information on grease lubrication of roller bearings on our eSource article General Grease Overview and Bearing Lubrication