How often should screw compressor oil be changed?

The replacement cycle of screw compressor oil is usually the first time after 500 hours of operation of the new machine, and then every 2000 to 8000 hours. The specific cycle needs to be comprehensively determined based on the operating environment, oil type and manufacturer’s recommendations.。The following is a detailed explanation of this issue:

1. Basic replacement cycle

1. First replacement
   New screw compressor in operation500 hoursThe oil will need to be changed for the first time later. This is because during the running-in period of the new machine, metal debris will be produced by friction between parts, which may contaminate the lubricating oil and affect equipment performance.
2. Regular replacement cycle
   • mineral oil type: Usually every2000 to 4000 hoursReplace it once.
   • synthetic oil type: For high-performance synthetic oils from brands such as Mobil and Shell, the recommended replacement cycle can be up to8000 hours or more。
   • extreme conditions: If the compressor is exposed to high temperature, high humidity, high dust or in contact with corrosive gases for a long time, the replacement cycle needs to be shortened (e.g.1000 to 2000 hours）。

2. Key factors affecting the replacement cycle

1. use environment
   • humidity: High air humidity will lead to an increase in condensed water and accelerate the emulsification and deterioration of lubricating oil.
   • dust: When dust in the air enters the compressor, it will pollute the lubricating oil and increase wear.
   • corrosive gases: For example, acidic or alkaline gases in the chemical industry will directly corrode lubricating oil and shorten its life.
2. Oil type
   • mineral oil: Low cost, but poor oxidation resistance and high temperature resistance, requiring frequent replacement.
   • synthetic oil: Such as PAO (poly alpha olefin), ester oils, etc., have excellent oxidation resistance and thermal stability, and can extend the replacement cycle.
3. operating load
   • continuous operation: For compressors that operate continuously 24 hours a day, the aging rate of lubricating oil is accelerated and the replacement cycle needs to be shortened.
   • intermittent operation: For compressors with short daily running times, the lubricant replacement cycle can be appropriately extended.
4. recommended by the manufacturer
   • Different brands of compressors may have different requirements for lubricating oil, so you need to refer to the equipment manual or maintenance guidelines provided by the manufacturer. For example, some brands may recommend every3000 hoursReplace it once, while other brands may recommend every5000 hoursReplace.

3. Maintenance recommendations to extend lubricating oil life

1. Regularly check oil status
   • appearance: Normal lubricating oil should be light yellow or transparent and colorless. If it becomes turbid, black or milky white, it means that it has deteriorated.
   • viscosity: Use a viscometer to measure the kinematic viscosity of the lubricating oil (40℃). If the change rate exceeds ±10%(mineral oil) or ±50%(ester oil), it needs to be replaced.
   • acid value: The acid value is analyzed through the oil testing agency. If it exceeds 20% of the new oil standard, it needs to be replaced immediately.
2. keep the system clean
   • air filter: each1500 to 2000 hoursReplace the air filter element to prevent dust from entering the compressor.
   • oil filter: each2000 hoursReplace the oil filter to avoid impurities contaminating the lubricating oil.
   • oil-gas separator: each3000 hoursReplace the oil and gas separator to ensure efficient separation of oil and compressed air.
3. Control operating temperature
   • Ensure that the compressor discharge temperature does not exceed the rated value (usually80 to 110℃), high temperatures will accelerate the oxidation of lubricating oil.
   • Clean the cooler regularly to prevent poor heat dissipation from causing temperature rise.

4. Adjustment of replacement cycle under special circumstances

1. Running-in period for new machines
   After the first 500 hours of operation of the new machine, the lubricating oil needs to be replaced and the oil system cleaned to remove metal debris generated by running-in.
2. Restart after a long shutdown
   If the compressor shutdown exceeds3 monthsBefore restarting, check the status of the lubricating oil and replace it with new oil if necessary to prevent oil deterioration and damage to the equipment.
3. Contraindications for oil mixing
   It is strictly prohibited to mix different brands or types of lubricating oils, otherwise chemical reactions may be triggered, resulting in degradation of oil performance or equipment failure.