Oil vs Oil-Free Air Compressors

Air compressors are found in many commercial and industrial businesses, from vehicle workshops to large manufacturing facilities. As much as ten per cent of all industrial power consumed in the UK is directed toward powering compressed air systems.

Oil-free and oil-lubricated air compressors work hard to create a sufficient volume of compressed air for related operations. Whether it is a piston or a rotary screw, the choice of compressor is an important one. Oil compressors are costlier than oil-free compressors. 

Some industries do not allow for oil contamination in compressed air. These include medical fields, food and beverage manufacturing or packaging, and sensitive air-powered equipment. Therefore, it is useful to understand the fundamental differences, benefits, and drawbacks of air compressor systems.

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.

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.

Oil vs Oil-Free Air Compressors
Oil vs Oil-Free Air Compressors

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.

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

Here are some factors to think about when choosing an air compressor:

The operating environment is easy to overlook. Temperature and humidity variances during different seasons impact performance. They also alter compressor lifespan too.   

Air purity is often the determining factor in compressor selection. For some industries, oil-free output air is a prerequisite. Certain pieces of equipment might not operate when the air is too oily.  

Cost is also relevant. Oil compressors cost twice the price or more to purchase, but their lifecycle is five to seven times longer. They do, however, have ongoing maintenance needs. Oil-free compressors will not break the bank, but the operational life of the latest models falls far short of their oil compressor counterparts. However, they are pleasingly easier to maintain.

In two minds about which compressor type is right for your business? Our team can provide an answer.

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.

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 considerable, and choosing the right compressor is essential to support your operations. Get in touch with our knowledgeable people at J LL Leach to help you make the right choice.