Design and resulting purity are separate matters
Oil may be used, for example, in separate bearings or a gearbox without being injected into the compression chamber. Overall system performance also depends on intake conditions, drying, filtration and pipe condition. The designation Class 0 must be read together with the scope, limits and conditions of the declaration or test.
Select the whole treatment chain
Start with the production process requirement and the location where quality must be achieved. Distinguish particles, water and total oil. An oil-free compressor does not remove intake humidity or guarantee microbiological purity. Component selection is therefore complemented by measurement under relevant operating conditions.
What to check in practice
- Define the required purity and where it will be verified.
- Assess intake conditions and possible contamination in the old distribution system.
- Compare operating costs of complete setups, not just compressor purchase prices.
Example scenario
After replacing an oil-injected compressor with an oil-free one, the original pipework remains. Oil deposited in the network may continue to contaminate the air. Replacing the source alone therefore does not prove that the required limit is met at a remote workstation.
What to watch out for
- Equating an oil-free machine with zero total contamination.
- Omitting drying simply because compression is oil-free.
- Treating certification of one device as certification of the whole operation.
Must the food industry always use an oil-free compressor?
The choice depends on the specific process, risk assessment and purity specification. An industry name alone cannot determine a technology or a universally mandatory class. The requirement must be documented and verified at the point of use.