Industrial air compressors are common in UK operations. They use about 10% of industrial electricity, making efficiency important for running costs.
When choosing a compressor, you must decide between oil-lubricated and oil-free models.
Oil-lubricated compressors use oil to reduce friction. This controls heat and extends equipment life. They work well for daily use but need regular oil changes. A Leicester Engineering Works runs six units, changing oil every three months at £75 per unit.
Oil-free compressors function without internal lubrication. They produce air without oil contamination. A Swindon medical supplies manufacturer uses these to avoid product contamination during packaging.
Maintenance differs between types. Oil-lubricated models require checking oil levels weekly, changing filters quarterly, and cleaning air intakes monthly. Oil-free units need bearing inspections twice yearly and cooling system checks. Brighton Seafront Amusements switched to oil-free compressors last autumn and now spend two fewer hours on weekly maintenance.
Food producers, pharmaceutical companies, and electronics firms tend to use oil-free systems. Building sites, car garages, and factories often use oil-lubricated compressors.
When selecting, consider both purchase and running costs. Oil-lubricated compressors cost less upfront but require ongoing oil purchases. They also generate waste oil that must be properly disposed of at council recycling centres. Most oil-free units run at higher speeds, creating more noise – typically 5 to 8 decibels higher than comparable oil-lubricated models.
How Oil and Oil-Free Compressors Work
Any decision over oil vs oil-free air compressors should not be taken lightly. No one compressor type applies to all circumstances.
To help guide your decision, we cover the basics of oil-fed and oil-free air compressors below.
Oil Compressors
Oil-lubricated air compressors rely on oil to keep internal parts moving smoothly without undue friction. Piston compressors, for example, have oil lubrication to prevent excessive wear on components.
An ample supply of clean oil prevents a compressor from overheating. The oil acts as a lubricant and seals the internal housing, too. These machines only begin to struggle if inferior or older oil is used.
Oil is essential, whether using a pressure system where pressurised oil pushes through the internal chambers or a splash system with bearings sprinkled with the lubricant. Machines run better with it and last longer.
These compressors have limitations, particularly in industries requiring oil-free compressed air. The two main ones are food manufacturing and pharmaceutical.
Oil-Free Compressors
Oil-free air compressors are devoid of oil inside the compression chamber. However, it is used for the gearbox. The gearbox requires it to operate properly. It is completely isolated from the closed, compressed air loop. This oil is filtered and later cooled to prevent the gearbox from overheating.
Oil-free air compressors eliminate oil from the compression chamber. Instead, advanced coatings and minimal-friction materials ensure smooth operation. Intercoolers are often integrated to maintain lower temperatures.
In oil-free rotary screw compressors, for example, cooling and lubrication are achieved through innovative materials and designs, ensuring oil-free air output.
Instead of oil lubrication to maintain lower internal temperatures, a minimal friction surface inside the compression chamber allows for smooth operations. Intercoolers – internal cooling inside the air system – can be used to reduce temperature levels.
Oil-free compressors vary in the design approach. Therefore, rotary screw compressors operate differently from piston compressors. Yet, both remain oil-free through alternative approaches to cooling and lubrication.
Pros and Cons of Each Type
Oil Compressors
Pros:
- Best for commercial and heavy-duty requirements
- Built for robust durability
- Working life is approximately 15,000 hours (depending on the model) versus roughly 2,000 hours for oil-free models
- Regulates heat levels even during continuous operations
- Moving parts cooled using oil lubrication
- Runs quietly compared to oil-free air compressors
Cons:
- Output air always contains oil particulate matter
- Should air purity need to be changed, an oil compressor might be inappropriate
- Oil compressors are several times costlier than oil-free versions
- Higher maintenance requirements, including regularly changing the oil and oil filters
Oil-Free Compressors
Pros:
- Suited to smaller operations and compact installation scenarios
- Best compressor type for industries requiring oil-free compressed air
- The range of oil-free compressors benefits from reduced upfront investment
- Lighter, mobile compressor option
- Less, infrequent maintenance required
Cons:
- Shorter lifespan at approximately 2,000 hours (depending on the model) compared to oil-lubricated models
- Less practical for continuous use; may overheat or add excessive wear
- Difficult to renew alternative cooling methods when experiencing declining wear-related effectiveness
- Louder than lubricated compressors
Need help determining the right compressor type? Talk with our compressor professionals at J LL Leach.
Suitable Applications for Each Type
Oil Compressors
Busy construction sites and industrial operations commonly need air compressors to power pneumatic equipment. Oil compressors meet the demand when continuous, substantial compressed air volumes are required.
Oil-based compressors produce output air with a certain amount of oil contaminants. While filters reduce this, it is unavoidable. Industries requiring oil-free air quality must instead look at oil-free compressors. These industries include electronics manufacturing, food and beverage production and packaging, and various medical fields.
Also, this type of compressor cannot be altered later to become an oil-free version. Therefore, once committed to an oil compressor, oil-free air production is not possible.
However, industries such as electronics, food and beverage, and medical fields requiring oil-free air must opt for alternatives.
Oil-Free Compressors
Oil-free compressors are found in medical offices, dental surgeries, and various manufacturing facilities. The food and beverage industries also require higher air purity to avoid contaminating their final product.
In addition to the oil-free benefits, these compressors are smaller and often mobile. They fit into smaller spaces where an oil compressor would not. However, they are also considerably louder compared to oil-based models. As such, thought must go into sound mitigation.
Factors to Consider when Choosing an Air Compressor
Choosing between oil-free and oil-lubricated air compressors involves several practical factors:
Air Purity
Pharmaceuticals, food production, and electronics need clean air. Oil-free compressors prevent contamination and meet ISO standards. Kendal Dairy Products installed six units last year to comply with food safety rules. If your application tolerates some oil, oil-lubricated models work well.
Usage Pattern
Oil-lubricated compressors handle regular use better. A Birmingham metal shop runs theirs 14 hours daily with few issues. Oil-free models wear faster when used constantly. Most tradespeople in Yorkshire use them for 2–3 hour tasks, then let them cool down.
Cost Over Time
Oil-free compressors cost less to buy but typically last about 2,000 hours. Oil-lubricated models run up to 30,000 hours but need oil changes every 500 hours, costing £35 each time. Wright’s Garage in Newcastle budgets £210 yearly for compressor maintenance.
Noise Level
Oil-lubricated models produce about 70 decibels. Oil-free compressors run at 80+ decibels. Many workshops in terraced buildings around Manchester house them in storerooms or build basic sound barriers using leftover materials.
Movement Needs
Oil-free compressors weigh less. Thames Valley Plumbing uses 15 kg units stored in their Ford Transit vans overnight. Larger oil-lubricated models, especially rotary screws, need permanent installation and 1-metre clearance for proper cooling.
Maintenance Tips for Both Types of Compressors
Oil Compressors
For optimal performance, oil compressors require regular maintenance.
During maintenance appointments, the intake valves are cleaned, fasteners re-tightened, and connecting hoses checked. The air receiver tank is drained to remove residual moisture build-up. Changing air filters and the oil ensures smoother operations and cleaner air quality. Also, an oil separator review verifies whether any parts require a replacement.
Air leakage checks are also included to confirm compressor performance.
Oil-Free Compressors
Oil-free compressors do not avoid the need for maintenance. However, it is required less frequently to maintain operations.
Regular inspections include looking for indications of excessive wear. Special attention is paid to the various cooling systems, including intercooler systems, to verify their effectiveness. Examining filtration systems ensures the cleanest air output quality.
An air leakage review is also part of a good maintenance program.
Conclusion
Air compressors are divided into two camps. The oil-free models are necessary for industries where no oil contamination is acceptable within compressed air. Healthcare, specific manufacturing, and the petrochemical industries fall into this category. By comparison, oil compressors are more robust, longer-lasting options for industries where a little oil in compressed air is a non-issue.
Atlas Copco’s comprehensive range includes oil and oil-free compressors, ensuring you find the right solution for your needs.
Smaller operations requiring compact compressors should strongly consider oil-free models, although they must accept a shorter lifespan and a noisier unit. Oil-based compressors are larger, quieter, and last much longer but are more expensive.
The differences between oil and oil-free compressors are significant, and selecting the right type is critical to supporting your operations. Get in touch with the experts at Atlas Copco to explore the best solutions for your business.
FAQ
What is the difference between oil-free and oil-lubricated air compressors?
Oil-free compressors work without oil in the compression chamber using coated parts. They suit applications needing clean air. Oil-lubricated compressors use oil to cut friction and heat. They tend to last longer and make less noise, though oil can get into the air.
Do oil-lubricated compressors require more maintenance?
Yes. You need to check the oil levels every few weeks and change it after about 500 hours of use. The filters get clogged with dust and need replacing quarterly.
Oil-free compressors need less upkeep but still require attention. The air filters collect dirt and need cleaning.
Which type of air compressor is best for clean air applications?
Oil-free compressors suit clean air needs like medical, food or electronics work. They keep oil out of the air system.
Baxter’s Auto in Sheffield has used oil-lubricated models for 15 years. Their compressor sits by the tyre-changing equipment in the corner, running about six hours daily. The slight oil mist does not matter for their work, and the mechanics prefer the quieter operation when working late shifts.
