TECH TIPS by Dave Clayton
Your Source for Service Information
Compressor Oil Contamination - Part I
Refrigerant oils, critical to the lubrication of the compressor, must be kept free of contamination and breakdown. Contamination can be due to foreign particles, moisture or oxygen. Breakdown can be due to excessive temperature or chemical reactions.
Poor mechanical maintenance can lead to contamination due to foreign particles or chemical breakdown. Poor handling practices can result in the lubricant being contaminated by foreign particles or moisture. Refrigerant leaks or improper system settings can result in contamination due to moisture or oxygen and lead to chemical breakdown. Chemical breakdown can result in decreased lubrication, sludges, and the formation of acids.
Particulate contamination can cause excessive wear and premature failure by reducing necessary clearances betweeen components and blocking oil channels. Metallic particles can act as abrasives. Moisture can freeze and block oil channels, and it can reduce the lubricating properties of the oil.
- Introduced during handling due to poor handling practices.
- Generated during operation due to poor maintenance practices resulting in excessive wear.
- Sludges created by chemical breakdown.
- Copper plating due to reactions between refrigerant piping and acid contamination.
Moisture in the oil can reduce its lubricating properties as well as form sludges. Suction leaks can introduce air (oxygen) into the refrigeration system. The oxygen and refrigerant react and create acids. The acids attack the copper piping forming metallic sludges and causing plating on the compressor's crankshaft journals and bearings and the piston wristpins.
- Moisture due to poor handling practices or refrigeration leaks.
- Acids formed due to refrigeration leaks.
- Excessive temperature due to reduced clearance, poor oil quality, and improper operating setpoints.
Contamination for any reason results in reduced clearances and restrictions in oil channels which lead to excessive friction and higher temperatures. The resulting breakdown of the oil, and restricted oil delivery, results in even higher temperatures and ever accelerating breakdown. The result is increased wear and unplanned downtime.
In Part II we will discuss how to avoid, identify, and mitigate these problems.
These technical tips are for use by qualified maintenance personnel who are familiar with their specific freeze drying equipment. These tips are intended only as general guidelines. Lyophilization equipment is frequently custom configured and some tips may not be appropriate for all freeze dryers. Always read and follow the directions of your equipment's maintenance manual. If you would like to discuss one of our tech tips, please contact Dave at 215-672-7800 ext-1376.