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Compressor Dictionary – O

Oil Lubrication

BAUER compressors are equipped with an industrial grade oil pump and filter. Effective lubrication of » pistons, cylinders and the » drive gear guarantees minimum wear and maximum compressor life.

BAUER compressors are designed and manufactured for continuous running.

BAUER compressors are designed to inject a precise amount of oil into the final stage's guiding piston at constant pressure. The oil drips down onto the spinning driving gear. This produces a fine oil mist, which lubricates the bearings and cylinder walls.

Three main reasons for lubricating compressors are:

• minimising friction,
• minimising wear, especially in the cylinders and bearings,
• cooling the unit.

Careful selection of adequate lubricants is of prime importance. Since these are in contact with breathing air, they have to be physiologically and toxicologically safe. Brands have to be certified for the use in BAUER breathing air compressors. The choice of oil also has fundamental influence on the compressor's lifetime.

Lubricants are either synthetic or mineral oils. Synthetic oils are designed for heavy-duty use and continuous running over a wide temperature range (+5 °C to +45 °C). Synthetic oil ought to be changed after 2 000 operating hours or after two years, whichever occurs first. The specific servicing interval is indicated in every model's operating manual.

Mineral oils are designed for light duty compressor use and for a narrower temperature range (+5 °C to +35 °C). Mineral oil ought to be changed after 1 000 operating hours or after 12 months, whichever occurs first.

A simple switchover from mineral oil to synthetic oil is only possible during the first 100 operating hours of a new compressor. Beforehand, the compressor has to be cleaned thoroughly. Older units have to be checked by a qualified service technician prior to the oil change. Synthetic oils tend to dissolve carbon deposits inside the compressor. The dissolved residue will clog filters, valves and coolers. A switchover from synthetic to mineral oils is possible anytime.

Compressors that are designed for continuous running require a different lubrication system than those that are operated intermittently. Light-duty, portable compressors employ splash lubrication. A pin, which is attached to the crankshaft, dips into the oil sump and sprays the bottom of the pistons and the walls of the cylinders. The compressor must be positioned horizontally (the angle of tilt should not exceed 10°) for effective lubrication.

Compressors that are in operation around-the-clock employ an oil pump. The pump takes in oil from the sump and pressure lubricates the final stage. The excess oil drips down, is scattered by the piston rods' motion and, hence, lubricates the other moving parts. The tilt of the unit is restricted to 10° to prevent air from being sucked in by the oil pump. These units are ideal for continuous operation.

The compression chambers on top of the pistons also need lubrication. To that end, the air that escaped into the crankcase (blow-by), which has a pressure of 1,3 bar absolute and is saturated with oil, is injected into the first stage. Besides offering first rate lubrication, the compressor's free air delivery is enhanced by 5 - 10%. The oil residue in the blow-by no longer circulates inside a closed system. Rather, it bonds with the water vapour in compressed air and forms condensate, an emulsion of water and oil. The oil lost in cylinder lubrication has to be supplemented regularly.

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