DGX Compressor Lubricants
Compressor Lubrication for SCUBA
The SCUBA diving industry relies on multi-stage reciprocating high-pressure compressors to produce our breathing gases. Because of what we do and where we do it, those compressors are often located in harsh conditions of tropical temperatures or inadequate ventilation that demand a lot from their lubricant. While many operators continue to use inexpensive Group II or III mineral oil based petroleum lubricants, best practice today is to use a synthetic lubricant to help minimize equipment down time and maximize equipment service life. Synthetic lubricants used in SCUBA breathing gas applications with high-pressure compressors are typically either polyalphaolefin or ester based:
- Polyalphaolefins (PAO) are made from a highly refined hydrocarbon mineral oil base that has been so extensively processed as to be considered a Group IV synthetic lubricant. Compared to mineral oils, the PAOs offer improved thermal and oxidative stability. PAOs are very widely used in a great many lubrication applications because their better performance makes them cost effective when compared to mineral oils. The most common complaint about PAO based lubricants in high-pressure compressors is they still have a tendency to form carbon deposits and varnishes that can decrease gas throughput and increase operating temperatures.
- Esters are a higher cost Group V lubricant base that is synthesized from acids and alcohols. Compared to mineral oils and PAOs, the ester based lubricants offer excellent performance in higher temperature applications with superior oxidative stability that resists formation of varnishes and carbon deposits. Ester molecules have polarity that results in a stronger film that better adheres to metal surfaces, which translates into higher lubricity with less wear and lower energy consumption in lubricant applications. Ester based lubricants are the preferred choice for high-pressure compressors used by SCUBA divers.
Environmentally, both polyalphaolefin-based and synthesized ester-based lubricants used in breathing air applications are readily biodegradable with no bio-accumulation and low-toxicity characteristics. However, these characteristics should be considered to only be true prior to use of the lubricant. Used lubricants are considered toxic due to the effects of exposure to high temperatures along with the accumulation of metals due to mechanical wear and operators must practice responsible disposal methods for used lubricants.
Whatever your choice for lubricant, avoid mixing lubricants with different group classifications or changing lubricant using a different group classification without following special replacement procedures especially in older compressors. It is important to point out that some suppliers of breathing air compressors may require their own private label brand of lubricant be used in order to maintain the equipment warranty.