Grease Analysis
Grease Analysis is a predictive maintenance technique that evaluates the chemical, physical, and mechanical condition of in-service lubricating grease to determine base oil degradation, thickener integrity, additive depletion, contaminant presence (water, dirt, other greases), and wear debris concentration, enabling condition-based maintenance decisions rather than reactive fixes.
In shop floor maintenance, grease analysis is applied to monitor grease-lubricated bearings by extracting a representative 1–2 gram sample from the 'live zone' using ASTM D7718-11 standard procedures. The test slate includes basic screening (Ferrous Density, FTIR, color, water) and advanced tests (Total Water, Remaining Useful Life via RULER, Elemental Metals, Microbial, Extrusion) compared against a fresh grease baseline. Trending uses statistical standard deviation (Alert = 2σ, Alarm = 3σ above average) to identify deviations. Results are integrated into CMMS (e.g., ServiceGrid) to automate regreasing intervals, trigger maintenance work orders, and correlate with vibration/ultrasonic data for holistic asset reliability.
What is the minimum sample size for modern grease analysis?
As little as 1 gram for atomic emission spectroscopy (Rotrode AES) to measure wear metals, thickeners, and additives; 2 grams for ASTM D7718-11 standard practice.
How does FTIR distinguish grease types and detect oxidation?
FTIR identifies gelling agent (thickener) type/concentration, detects oxidation by-products, and flags cross-contamination by comparing spectral peaks against fresh grease baselines.
What does the RULER test measure in grease?
Linear Sweep Voltammetry (RULER) quantifies remaining amino/phenol oxidation inhibitors to determine Remaining Useful Life (RUL), critical for predicting additive depletion before mechanical failure.