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Building a compact air compressor is not just about miniaturizing an existing larger model. It is about creative use of technology to miniaturize without minimizing performance parameters. In 2002, ELGi achieved just that. We designed and manufactured the smallest screw air compressor in the world.


The challenge was put forward by a German company that wanted a screw compressor for a specific application. Traditionally such applications are catered for by diaphragm or piston compressors, as the requirement is for small air volume. In looking at screw compressor technology, it was immediately obvious that the rotors would need to be very small (the size of the rotors being one of the critical factors that determine the flow volume of the compressor). It was also obvious that at these sizes the losses due to leakage would be significant.


The solution demanded a compressor running at high speeds in order to compensate for the losses. However, higher speeds produce higher flow and hence the rotor sizes had to be further reduced to meet the customer’s specifications. This dynamic iteration between speed and size of the rotors resulted in an optimized design. We were able to build rotors measuring 35 mm and 28 mm for the male and female respectively. Additionally, we attained speed capability of up to 20,000 RPM. The smallest rotors before this were in the range of 55-60 mm. ELGi’s innovative design resulted in a 30-40 % reduction in the size of a screw air compressor.


The next challenge was manufacturing. All the manufacturing machines available were designed with a certain minimum size in mind. ELGi had to implement manufacturing process changes to enable the existing machines to produce a compressor of this size. In addition, ELGi searched the globe to identify standard components such as bearings and seals that could be used without compromising the design goals. Both these aspects were critical in meeting the budget objectives of the project.


Within a short time of 3 months, the first prototype was put on the test bed and the results were excellent. The flow, pressure, power and temperature were all within the limits defined by the design. This was followed by rigorous endurance testing and the product withstood all the abuse that was hurled at it.


With this confidence, the first displayable working package was made and exhibited at the Compressed Air and Vacuum Technology Exhibition in Hannover, Germany in April 2003. The reception to this product was a mixture of disbelief and relief. Disbelief from competitors who could not accept that making such a small screw compressor was possible. Customers, who had been hankering for such a product, reacted with a sense of relief that their needs were finally being addressed by ELGi.


This technology opened up opportunities for oil-free compressors of this size as well as applications for futuristic technologies such as fuel cells. One innovative step by ELGi has gone on to change the way the world uses compressed air technology today.

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