Several Causes of Severe Deterioration of Air Compressor Lubricating Oil

Precautions for the Use of Screw Air Compressor Oil

Air compressor oils of different grades and classifications are prohibited from being mixed. All old oil must be completely drained during oil replacement. 

It is strictly forbidden to merely top up oil or reuse filtered waste oil. Even if the color of compressor oil appears unchanged visually, the consumption of additives may have exceeded the limit.

If there is little sludge inside the system, fill the unit with half of the new oil, run the machine for 15 to 60 minutes, drain all oil completely, then fill with fresh oil for normal operation.

If excessive sludge and carbon deposits accumulate, disassemble the oil tank and manually remove sludge and carbon deposits, followed by cleaning with dedicated detergent. 

After cleaning, the tank must be blown dry with dry air. Fill with sludge & carbon cleaning fluid and operate the unit for 100 to 200 hours, then drain all cleaning fluid before filling with new oil for regular operation. 

Failure to follow this procedure may degrade the performance of oil additives and even trigger safety accidents.

When changing oil, replace the oil bypass filter, oil filter, fine oil-air separator element, coarse filter elements simultaneously. Inspect whether the suction strainer,

air filter, check valve, temperature control alarm and other components are intact.

The oil replacement interval is not fixed. Equipment conditions, ambient environment, oil temperature and mechanical impurities can accelerate oil aging. To prevent carbon deposition and coking, 

observe the lubricant color, viscosity and oiliness every 300 hours during operation. Nevertheless, oil quality cannot be judged solely by color.

If the oil temperature is excessively high, root causes must be identified. Do not bypass protective devices just to maintain production.
Common causes of excessive oil temperature:
The water cooling pipes of the oil cooler are heavily fouled or blocked; excessive dirt on the radiator (air-cooled type), leading to low cooling efficiency.
The thermostatic valve of the oil cooler fails to act, or the oil temperature sensor malfunctions. If controlled by PLC, faults on the circuit board cannot be ruled out.
Poor fitting clearance of moving components.
High ambient temperature leads to elevated lubricant temperature.
Excessive internal leakage inside the screw rotor caused by malfunction or misoperation of the intake throttle valve (partial intake closure).
Poor oil return flow; clogged oil filter (pay attention to the quality of oil filters) leading to insufficient oil supply.
Insufficient compressor rotating speed caused by loose V-belts, which also reduces air delivery capacity.
Discharge pressure fails to reach the set value; possible reasons include improper model selection (undersized unit), clogged air intake filter/oil-air separator, or stuck intake throttle valve.
Poor quality or contamination of lubricating oil, resulting in aging and failure of lubricant.

When oil temperature is abnormally high, first check the oil level, then inspect the oil cooler, verify whether the spring inside the thermostatic valve is broken, 

and finally check if the oil filter is clogged (an oil filter with excessively fine filtration accuracy is also unacceptable).

Record the time of lubricant and component replacement on site, check records regularly and assign responsible personnel. If significant evaporative loss of lubricant is found, first inspect whether the oil-air separator has perforations.
Screw compressor oil is a special fluid and must be managed by designated personnel to avoid accidental oil mixing on site. Tighten drum caps after oil use; do not leave open tools nearby.
Simple Viscosity Test Method for Lubricant

Take a clean glass plate, wash and dry it, fix it at an inclined angle of approximately 45°. Use a clean dropper to drip a small amount of new oil onto the glass plate, and record the flow time over a fixed distance. 

 Test the waste oil with the same method. Oil replacement is mandatory when the flow time difference reaches 15%.