Oil Vs Oil Free Air Compressors
There are many factors to consider when choosing an air compressor. The choice between oil-free and oil-lubricated is one of the most important.
Your decision will impact things like cost, maintenance needs, and the uses to which you put your compressed air. While air purity is usually the chief consideration – oil-free compressors are the only way to prevent oil contamination – those other factors may well affect your decision.
The role of oil in air compressors
All air compressors work by reducing the volume of a mass of air, with different types of compressors using different techniques. Piston, or reciprocating, compressors work in a similar way to an engine, compressing air in pistons. Centrifugal compressors use the velocity of air, spinning it to create pressure. Rotary screw compressors, the type most often available as oil-free compressors, use interlinking screws to continuously push air into a smaller volume.
Each has different moving parts, and, like any machinery, oil is typically used as a lubricant. When used in a compressor, oil performs familiar functions:
- It lubricates. Oil lubrication helps keep moving parts moving freely, reducing friction and improving efficiency.
- It cools. Oil distributes and removes heat from the compressor.
- It seals. Oil fills the small gaps between moving parts, minimising the air loss that would lower pressure.
However, oil-free compressors remove all oil from the compression process, allowing them to generate Class 0, oil-free, compressed air.
The benefits of oil-lubricated air compressors
Able to use oil with every moving part, an oil-lubricated air compressor can take advantage of the functions oil fulfils.
- They can be more efficient, benefiting from reduced friction and better cooling.
- They have longer lifespans and are protected by the oil, reducing wear and tear.
- They can be better suited to heavy-duty tasks and prolonged operation, with reduced heat build-up.
The benefits of oil-free air compressors
Although oil-lubricated compressors have advantages, oil-free compressors have features that can make them more attractive.
- They are lower maintenance, usually having fewer moving parts, so less needs to be maintained.
- They tend to be smaller compressors. The simpler design can reduce overall size, making them attractive if space constraints are an issue.
- They are the only way to guarantee oil-free air. If your processes demand clean air, for example in food production or for breathing, going oil-free is the only way to achieve that.
Oil Vs Oil Free Air Compressors
Oil-free v oil-lubricated
Air purity
Compressed air quality is the most notable difference between the two. An oil-free compression chamber results in oil-free air. An oil-lubricated compressor, even with an oil filter, will have some air contamination.
Cost and expenses
Oil-free compressors, as a result of their specialised design, tend to be more expensive initially. However, they can offer some savings on maintenance costs.
Operational lifespan
Oil-lubricated compressors, because of the reduced friction and wear and tear, tend to have a longer life span. However, improvements in oil-free compressor design have greatly reduced and, in some cases, eliminated the gap.
Workplace impact
Oil-free compressors tend to be smaller, which can make them suitable for more space-constrained operations. However, this needs to be balanced against the increased noise and heat they generate without oil to disperse heat and absorb sound.
Compressed air applications
Aside from purity considerations, situations where the compressor is in continuous operation, or has to produce significant volumes of compressed air tend to be better suited to oil-lubricated compressors.
Choosing the right compressor
For most users, the choice is straightforward, but the key factors will be air purity, maintenance issues, risk and cost.
Air purity
Oil-free compressors are usually chosen because of the need for very high air quality. Applications like food production and processing, or pharmaceutical or medical uses cannot tolerate any risk of oil contamination.
For all other uses, an oil-lubricated compressor, with suitable filters can often achieve suitable purity levels.
Maintenance
Our engineers will always aim to minimise disruption during maintenance and servicing visits, but some disturbance will be inevitable.
If keeping the disruption and downtime from servicing to an absolute minimum is critical then an oil-free compressor helps you do that.
Budget issues
We know that every business has different budgeting needs and preferences.
Oil-free compressors come with a higher initial cost, but ongoing costs are lower. In some circumstances, an oil free compressor may be your best option.
Getting the right type of compressor
Search Air is more than happy to help you find the compressor that’s right for your unique needs. Just contact us, and we can help you balance your needs for compressed air, the location of your compressor, and even estimate your ongoing costs so you can be confident you’ve made the right decision.
FAQ
Which compressor is most cost-effective in the long run?
This will depend on your use case. Although oil-lubricated compressors tend to be more cost-effective over their lifespan, factors like use patterns, maintenance, and energy-efficiency affect this. We can help you estimate running costs as part of our design process.
Are oil-free compressors suitable for continuous heavy-duty tasks?
Most oil-free compressors are less well-suited for continuous operation and heavy-duty tasks. However, more advanced oil-free models can also manage these, using techniques such as water cooling to manage heat, or oil-free centrifugal compressors, which can generate large volumes of compressed air.
How often does oil need changing in lubricated compressors?
This varies from compressor to compressor, and you should always check your manufacturer’s documentation. As a general rule, it should be changed at least once a year, but your usage will affect that. Our servicing plans include filter and oil changes at appropriate intervals based on use, keeping your compressor running optimally.