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The American Society for Testing and Materials (ASTM) recently issued Method D7718-11, providing an approved standard practice for sampling critical grease-lubricated equipment.
The new standard uses the methodology of the Grease Thief, which enables users to get a representative in-service grease sample from motor bearings, gearboxes, motor-operated valves and other critical machinery, then trend the analysis results for condition monitoring.
This analysis of in-service lubricating grease not only can aid in predicting the life and condition of the grease-lubricated component, but it also can be combined with other technologies such as infrared imaging, vibration analysis and ultrasonic vibration analysis to predict when a machine may fail.
The information obtained through these analyses may allow for more overall uptime by aiding in the prediction of grease-lubricated component failures as part of a predictive maintenance schedule. The prediction of a failing grease-lubricated component should also improve the level of safety of all who work around the component.
“The new standard establishes methods for obtaining good samples from many types of components,” says Richard Wurzbach of MRG Labs. “Until now, there has not been reliable guidance for taking grease samples, which has severely limited the use of grease analysis as a diagnostic tool. With the advent of new technology and a standard approach for sampling, the door has been opened for grease analysis to take on the challenge of improving reliability of wind turbines, robotics, power plants, mining operations and manufacturing.”
The use of the Grease Thief in the place of motor bearing drain plugs allows for proper grease purging while also capturing any purged grease for analysis.
Traditionally, vibration analysis would be used to monitor the mechanical condition of a grease-lubricated electric motor. However, with the Grease Thief sampling devices, you can extract a reasonably representative sample of grease to detect mixing, grease degradation and wear particles.
“This standard practice is the basis for companies to create procedures and processes to ensure reliable monitoring of greases and grease-lubricated component condition,” Wurzbach adds. “Five methods are outlined, providing the proper precautions and steps, tools and methods, to consistently obtain and submit grease samples for analysis.”
The Grease Thief Analyzer utilizes a die-extrusion process to measure changes in grease consistency and flow characteristics, and prepares a thin-film substrate for subsequent lab analysis with typical oil analysis instrumentation. Sampling kits provide the opportunity to obtain results from as little as 1 gram of grease.
“In the same way that oil analysis has been enhanced by the use of sampling fittings and prescribed sampling procedures, grease analysis results can now stand on solid ground to encourage and enable reliable and consistent results,” Wurzbach notes. “The limited circulation of grease in machinery dictates that any samples be carefully obtained by an established best practice and with the right tools for the job. With the Grease Thief sampling technology and procedural guidance based on ASTM D7718, users now have the ability to confidently monitor and enhance the reliability of critical grease-lubricated components.”