The lubricating oil of a screw air compressor is hailed as the “blood of the machine”. It not only provides lubrication and reduces friction but also undertakes cooling and heat dissipation, as well as oil-gas separation. However, inferior lubricating oil (such as non-standard oil, recycled oil, or mixed oils of different models) will directly damage these three core functions, triggering chain failures ranging from “part wear” to “complete machine scrapping”, and also harbor potential safety hazards. The economic losses far exceed the cost saved by using cheap oil.
I. Lubrication Failure: Direct Metal-to-Metal Contact Causes Rapid Wear of Core Components
High-quality lubricating oil can form a uniform oil film on the surfaces of high-speed rotating components such as rotors and bearings, avoiding direct metal contact. However, inferior oil has low oil film strength, is prone to rupture, and has poor load resistance, leading to:
- Rotor wear: When the male and female rotors mesh at high speed, the oil film breaks, resulting in direct metal friction. Scratches, seizing, or even jamming may occur. Repairing requires replacing the rotors, which costs 30%-50% of the total price of the air compressor.
- Bearing burnout: Lack of effective lubrication between bearing balls and inner/outer rings turns rolling friction into sliding friction, causing a sharp increase in heat generation. Bearing noise or seizure may occur in as short as a few hours or as long as a few weeks, which in turn damages the main shaft.
- Seal aging: The impure additive components in inferior oil can corrode and swell seals and oil seals, leading to lubricating oil leakage. This further exacerbates insufficient lubrication, forming a vicious cycle.
Users can intuitively feel: increased machine operating noise, intensified body vibration, and overheated bearing end caps.
II. Cooling Failure: Heat Cannot Be Dissipated, Leading to “Overheating Crisis” for the Machine
A large amount of heat generated during air compression (the temperature rises by 80-120℃ when atmospheric pressure is compressed to 0.8MPa) is entirely carried away by lubricating oil. However, inferior oil has low thermal conductivity and is prone to oxidation and deterioration, resulting in rapid failure of the cooling function:
- Sharp rise in exhaust temperature: Inferior oil cannot timely dissipate heat, causing the air compressor’s exhaust temperature to continuously exceed 100℃. This triggers frequent shutdowns due to overheating protection, affecting production.
- Accelerated oil deterioration: High temperature causes inferior oil to oxidize and carbonize more quickly, forming sludge. Sludge further clogs the cooler fins and oil passages, hindering heat dissipation and falling into a vicious cycle of “overheating → oil deterioration → higher temperature”.
- Damage to rubber components: High temperature accelerates the aging and cracking of rubber parts such as oil pipes and seals, increasing the risk of leakage and shortening the service life of components in the electrical control box.
III. Difficult Oil-Gas Separation: Dual Losses of Surging Energy Consumption and Air Supply Contamination
The oil-gas separation of screw air compressors relies on the “anti-foaming property” and “separation stability” of lubricating oil, which are seriously substandard in inferior oil:
- Rapid clogging of oil separator filter element: Inferior oil is prone to generating a large amount of foam, and the oil mist particles are small, making it difficult to be separated by the oil separator filter element. This quickly clogs the filter element, causing the pressure difference before and after the oil separator to soar (normally ≤0.15MPa, while inferior oil may exceed 0.3MPa in 1-2 months).
- Increased energy consumption: Clogging of the oil separator filter element increases exhaust resistance, requiring the air compressor to do extra work to supply air. The energy consumption is 10%-20% higher than when using high-quality oil.
- Air supply contamination: Incomplete separation by the oil separator filter element leads to excessive oil content in the exhaust (normally ≤3ppm, while inferior oil may reach tens of ppm). This contaminates downstream pneumatic tools and precision equipment (such as electronic components and food processing machinery), resulting in product scrapping or tool damage.
IV. Carbon Deposits and Sludge: Hidden “Spontaneous Combustion Risk” and Blockage of Key Components
Inferior oil has low base oil purity and ineffective additives. Under high temperature and pressure, it is prone to oxidation and carbonization, forming black colloidal sludge and hard carbon deposits:
- Blocked oil passages: Sludge clogs oil filters, oil passages, and unloading valves, leading to poor circulation of lubricating oil and oil shortage in the main unit. Carbon deposits get stuck in the valve cores of intake valves and safety valves, causing valve jamming and faults such as “failure to stop when fully pressurized” and “inability to relieve pressure due to overpressure”.
- Spontaneous combustion hazard: Carbon deposits are flammable. If they accumulate on the surface of high-temperature components (such as exhaust ports and oil coolers), when the temperature reaches the ignition point (about 300℃), spontaneous combustion may occur, and even cause an explosion of the oil-gas mixture in the air receiver, posing a serious safety risk.
V. Hidden Losses: Maintenance Costs + Shutdown Losses Far Exceed Oil Costs
Many users choose inferior oil to “save money”, but in fact, they will pay higher hidden costs:
- Doubled maintenance costs: Inferior oil shortens the replacement cycle of oil filters and oil separator filter elements by more than 50%. In addition, core components such as bearings and rotors need to be replaced frequently. The annual maintenance cost may be 3-5 times the cost of high-quality oil.
- Heavy shutdown losses: Production interruptions caused by faults such as overheating and jamming, especially for factories with continuous production, may result in shutdown losses of tens of thousands of yuan a day.
- Shortened machine service life: Under normal maintenance, the service life of a screw air compressor is about 8-10 years. Long-term use of inferior oil may require overhaul in 3-5 years, or even complete machine scrapping.
Summary: Don’t “Cut Corners” and End Up “Paying a Heavy Price” – 2 Key Points to Avoid Pitfalls in Oil Selection
The hazards of inferior lubricating oil do not “manifest slowly” but “erode quickly” – from the first injection, hidden troubles have been planted in the machine. Avoiding these problems is actually very simple:
- Choose the right oil: Only use brand-specific lubricating oil for air compressors (such as Kaishan’s dedicated screw air compressor oil) or screw machine-specific oil that meets ISO VG46/68 standards. Do not buy non-standard oil or recycled oil.
- Do not mix oils: Do not mix lubricating oils of different brands or types (mineral oil, synthetic oil). When changing oil, completely drain the old oil to avoid oil compatibility issues.
Remember: High-quality lubricating oil is an “investment that saves money”, while inferior oil is a “money-burning trap”. Instead of spending a lot of money repairing the machine afterward, it is better to choose and use the right oil from the beginning.
Post time: Nov-21-2025
