Oil-lubricated or oil-free compressor?

When oil-free air matters

• Air that comes into contact with food or packaging
• Laboratories and analytical instruments
• Medical and dental use
• Processes where oil vapour leaves deposits or reacts with the product

When oil-lubricated is the sensible choice

In workshops, on construction sites and in ordinary pneumatics where the air drives cylinders and tools, oil-lubricated machines are a perfectly good choice. Jun-Air also lists its oil-lubricated compressors for dental and medical equipment, laboratory instruments and the food industry, so it is the requirements for the equipment that decide. They are also low-noise: the user manual gives 35–58 dB(A) measured 1 metre away, depending on the model.

The technologies in the Gast range

Gast builds machines on these five principles, among others, and they cover different parts of the pressure and flow scale. The air flows are the extremes stated by Gast, and the highest figures apply at 60 Hz:

• Diaphragm — oil-free, 3.4–110 l/min, up to 4.1 bar, vacuum to 31 mbar. For small, clean tasks
• Rocking piston — oil-free, 3.5–340 l/min, up to 12 bar. The highest pressure of the oil-free types
• Piston — oil-free, 37–311 l/min, up to 8.6 bar, tanks from 7.6 to 113.6 litres
• Rotary vane — lubricated or oil-free, up to 93.5 m³/h, but low pressure: max. 1.0 bar
• Regenerative blower — oil-free, 651–38 228 l/min, but only a few hundred millibar of pressure

Pressure and flow are linked

The list above shows a relationship worth noting: the machines with the highest air flow deliver the lowest pressure. A regenerative blower moves enormous volumes, but at only a few hundred millibar. If you need 8 bar, it has to be piston or rocking piston — however much air you would otherwise like.

Noise reduction as an option

Gast supplies Sound Shield for the 86R, 87R and 106R. The manufacturer states up to 25% lower dB(A) and up to 40% lower sone value. It is an option where the machine is otherwise right but is too close to people.

If in doubt

Describe the process, not the machine: what the air drives, how much and how often, and whether it comes into contact with anything that cannot tolerate oil. We will then suggest the technology first and the model afterwards.