Reduction of Friction Loss for Increased Energy Savings and Reduced Maintenance Workload

Tokyo, Japan, May 22, 2012 - NSK Ltd. (NSK; Headquarters: Tokyo, Japan; President and CEO: Norio Otsuka) today announced that it has developed a low torque rolling bearing designed for high efficiency centrifugal chillers used in large scale air conditioning equipment applications. In realizing the world's first*1 development of a rolling bearing solution for high efficiency turbo refrigeration machines, NSK has solved the problems posed by using sliding bearings by cutting friction loss in half.

NSK will seek to increase sales of this energy-saving product throughout Japan and worldwide, targeting 500 million yen in annual sales in 2016.


*1: According to NSK's findings as of March 2012

Development background
Reducing CO2 emissions and saving energy have become increasingly important in recent years as global warming countermeasures. In an effort to preserve the environment, the demand for centrifugal chillers, which have a high level of energy efficiency, has risen for air conditioner systems in large-scale facilities because such systems consume a great deal of power and fuel. Generally speaking, centrifugal chillers consist of a motor-driven centrifugal compressor that rotates an impeller to cause the refrigerant to blow outwards, and then the compressor compresses to circulate the refrigeration cycle. In terms of refrigeration capacity (cooling capacity), these machines typically range from 100 to 10,000 refrigeration tons*2. That alone is a lot of load to handle, but on top of that, in recent years there has been a push for
even higher efficiency and compactness, which has resulted in the compressors of these centrifugal chillers getting faster and faster. Of course, this is resulting in extremely demanding conditions for the bearings both in terms of speed and load, which in turn demands a high level of bearing technology.

NSK has responded to this demand by leveraging the experience it has built in aircraft applications to create a bearing that is highly reliable in environments 1.5 times faster than sliding bearings, and cuts friction loss in half through the use of such technology as high speed orientated cage shapes and lubrication methods.

Refrigeration Cycle


*2: One refrigeration ton is the cooling capacity required to phase change one ton of water at 0℃ to one ton of ice at 0℃.

Product features
1. Extremely low friction loss: half the friction loss of conventional products
By employing creative measures in the design of the bearing such as shape optimization of the cage and lubrication volume, this rolling bearing is able to cut friction loss to half of that of the widely used sliding bearings.
2. Improved durability through optimization of bearing interior specifications
The problem with typical rolling bearings under high-speed conditions is that the lubrication oil within the bearing gets agitated, resulting in friction loss in the bearing, which in turn leads to a variety of problems such as seizure and shortened life. This product is optimized in terms of the cage shape, material combination (brass and resin) and lubrication methodology to improve oil scavenging and thereby prevent seizure and also achieve sufficient product life.

Product benefits
1. Helps save energy
In reducing bearing friction loss, this product helps improve the performance of the centrifugal chillers, resulting in a roughly 20% improvement in energy savings compared to conventional refrigeration machines.
2. Improved compaction of the refrigerant
Modifying the bearing to high-speed applications also improves the compaction of the refrigerant, which in turn helps the turbo refrigeration machine achieve a high level of efficiency and compactness.
3. Less maintenance frequency
In reducing bearing friction loss and improving the lubrication performance, the bearing temperature is kept from rising, thereby improving reliability of the equipment.

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