Do you hear about “oil-free compressors” and “oil-less compressors” and wonder what the difference is? They both appear to be the same. More importantly, how does this apply to your healthcare medical air supply? For a detailed explanation of the following, refer to NFPA99, Edition 2012, Compressors for Medical Air Sections 126.96.36.199.3.4 through 188.8.131.52.3.14.
Compressors that fit both these descriptions are all constructed to deliver compressed air with no oil added or left in from the compression process. But the design of these units is dramatically different.
Oil-free Compressed Air
— Reference NFPA99 Edition 2012 – Exhibit 5.15
This refers to an air compressor unit that has no oil present in the compression area, but there is oil in the unit’s driving area such as crankcase, transfer case, etc.
Examples of oil-free compressors would be:
- Oil-free rotary screws with lubricated driving gears.
- Oil-free reciprocating compressors with a lubricated crankcase and a distance piece in the design, to keep oil from migrating from the crankcase to the compression chamber.
- Liquid ring compressors.
Current standards require a vent to help identify an oil-free pump malfunction. If a malfunction does occur, it may be possible for oil to migrate through to the compression chamber. This would pass oil or oil contaminated air downstream to the patient. Specific filters, filter elements, indicators and alarms are required in oil-free compressors. See NFPA 99, 2012, 184.108.40.206.3.13 (D)(1)(2)(3).
Among other things, an oil-free compressor also requires expensive hydrocarbon monitoring to be used in a medical air application. See NFPA 99, 2012, 220.127.116.11.3.13(D)(4). For these reasons, oil-free compressors are rarely used in medical compressed air equipment.
Today, oil-less compressors are most commonly used in medical air. Oil-less operation, combined with extensive drying and filtering processes, virtually eliminates the possibility of air contamination.
Oil-less Compressed Air
— Reference NFPA99 Edition 2012 – Exhibit 5.14
Refers to an air compressor that has no oil in the air compressor units whatsoever. Not in the compression area and not in the drive area. Many of these compressors use lubricated sealed bearings in some configuration. These are usually a pressed-on fit.
Examples of oil-less compressors would be:
In recent years, oil-less scroll compressors have dominated the medical industry. They have plenty of power, a small footprint, are quieter than most other compressors, are air cooled so no water is being wasted and are proven to be reliable even at 100% duty cycle.
Medical air compressor configurations have also changed. Scroll technology allows “banking” of compressors. Health facilities are going away from single, large, powerful compressors that cost a bundle to operate and maintain. Instead, compact systems comprised of several scroll compressors are being used.
Multiple scrolls add up to the same desired capacity, including the redundancy required in the system. The compressors are programmed to alternate and only those required to meet the varying demand at any point are running. There are so many more advantages to multiple scroll packages. Contact us and we’ll fill you in on the details.