SR drive boosts oil-free compressor efficiency

CompAir's successful range of oil free compressors has just got even better, with the introduction of two additional water injected screw compressors.

CompAir's successful range of oil free compressors has just got even better, with the introduction of two additional water injected screw compressors.

These are switched reluctance variable speed models - ensuring the oil free range now benefits from the same advanced technology as the L-Series screw compressors, which have proved so popular because of their excellent energy efficiency.

Designed for applications where there is a need for high-quality "oil free" air, this range offers a cost-effective oil-free solution.

Using the switched reluctance variable speed drive system, which CompAir manufactures under an exclusive license from SR Drives, offers customers even more options as part of the company's modular approach.

The system uses a digitally controlled switched reluctance DC drive.

The drive system enables the compressor to match output to varying demands and as a result provide considerable energy savings.

Adding an SR compressor to any installation of standard oil free compressors gives the entire system the ability to precisely match output to demand, allowing the compressors to consume exactly the right amount of energy to do the job, and no more.

CompAir has also announced even more improvements to the range with the smaller compressors also benefiting from variable speed controls.

The previous oil free series included 15, 22 and 37kW models, which were all fixed speed but now thanks to an inverter drive system, new variable speed models have entered production and the final oil free variable speed range now extends down to 15kW and up to 75kW.

Graham Roberts Managing Director of the Industrial Division explained: "CompAir firmly believes in putting the customer first which is why we continue to focus on developing and applying the newest technologies to our products.

Instead of just applying technologies to all compressors in a range we assess what is best for the customer in the long term".

"Developing and using the most appropriate technologies available we can meet all customer requirements across the globe, which is much more cost efficient and beneficial to the customer than building a single, larger 'one size fits all' solution".

With the lowest specific energy consumption in its class, the oil-free series offers outstanding energy efficiency and low operating costs.

Roberts continued: "In active air applications, quality of the air is key".

"High technology industries in particular, including precision engineering, pharmaceutical, food and drink, electronics, chemicals and healthcare, all demand higher quality air".

"They are also looking for the lowest ownership and operating costs".

"The single-stage water-injected rotary series is not only one of the most efficient range of oil-free rotary products available, it offers reduced energy and maintenance costs and hence a lower life cycle cost than any other compressor in its size range".

"A major advantage of this design is that not only is the air produced totally oil free, there is no oil used in the compressor at all".

"The bearings are greased and sealed for life, so there is no danger of contamination and no environmental costs associated with oil disposal".

At the heart of the oil free series is a single stage, single screw water injected compression element.

It has a bronze single six-flute main rotor with two carbon-fibre composite 11-tooth gate rotors.

The compression element is designed to deliver 12 pulses of air per revolution, compared with six pulses for a conventional screw.

This, together with the elimination of metal-to-metal parts, offers low vibration and noise levels.

During the compression cycle, atmospheric air enters the compression element and fills the flutes of the main rotor.

The gate rotors engage with the flutes and form two compression chambers, above and below the main rotor.

They then automatically follow the rotation of the main rotor, reducing the volume in the flutes and compressing the air along the compression chambers.

Purified water injected into the compression element seals, cools and lubricates the process.

When the flutes align with the discharge port, the compressed air and water mixture is discharged from the compression element and the water is separated from the compressed air in a vessel.

Fully integrated into the package is a water purification system that uses reverse osmosis membrane filtration to provide high quality injection water.

This removes dissolved salts, metals, minerals and organisms and ensures reliable and trouble-free operation.

This purified water enhances efficiency is by providing superior cooling and near isothermal compression.

With only a 15C temperature rise across the compression element, there is no need for a final after cooler, which reduces pressure losses and hence energy consumption.

The fully integrated package includes the air-cooled water cooler, water purification, full silencing for low noise levels, and a Delcos 3100 control system.

This simplicity of construction significantly reduces maintenance costs, with a service interval of 4000 hours and servicing limited to changing the filter elements.

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