Monitoring Moisture and Wear Particles in PAG and POE Synthetic Lubricants for R-134a Compressors Using Portable Oil Analyzer

Polyalkalene glycols, or PAG, and polyol esters, or POE, are two synthetic lubricants commonly used in refrigerant compressors. They are both hygroscopic. Moisture which is picked up can lead to chemically weakened load bearing surfaces and to corrosion, thereby accelerating mechanical wear.

PAG and POE lubricant samples having from 0.00% to 1.28% water were tested using a portable oil analyzer. Minimum detectibility was found to begin at 0.04% (400 ppm) moisture. Increasing amounts of moisture above this amount yielded proportional output response. Additional samples were contaminated with known concentrations of metal particles representative of common wear debris. Minimum detectability was found to begin at approximately 15 ppm for 4 to 6 micron size iron particles and <100 ppm for 0 to 60 micron size tin particles.