Oil-free lubrication for compressor bearings

SKF has successfully developed a range of hybrid bearings for use in compressors, with the refrigerant acting as the lubricant.

SKF has successfully developed a range of hybrid bearings for use in compressors, with the refrigerant acting as the lubricant.

This development is a huge step forward for both compressor manufacturers and end users who will benefit from better performance and lower costs.

The development also has a beneficial effect on the environment, as the absence of oil in the application removes the problems associated with leaks, maintenance issues and oil disposal.

The use of the refrigerant as the lubricant removes many of the bearing lubrication problems associated with refrigeration and air conditioning applications.

For instance, oil is traditionally mixed with the refrigerant in compressors to lubricate the bearings.

However, when this mixture enters the bearing, the refrigerant can "flash" or evaporate and therefore prevent the oil from lubricating the balls and raceways.

A further problem occurs because the oil is diluted as it is mixed with the refrigerant.

This lowers the lubricant's viscosity and immediately creates a "poor lubrication" condition.

With the hybrid bearings allowing the use of a homogenous refrigerant as the lubricant, evaporation and dilution problems are prevented.

A further advantage of the new technology is that it removes the need for an oil separator that collects oil and "pushes" it back to the bearings to minimize the amount of dilution.

Removing the separator lowers costs for the OEM and reduces the maintenance issues for the compressor owner.

In combining steel raceways with silicon-nitride balls, the hybrid bearings also provide the further benefits over conventional all-steel bearings of a greater degree of stiffness, the accommodation of higher speeds and longer lifespans.

The hybrid research is expected to cascade into further applications such as pumps, hospital and food processing equipment, and other specialized applications where lubrication, maintenance and environmental issues are a concern.

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