Fresh air

Oil contamination is an invisible enemy in all bottling installations and aseptic environments. Traditionally, bottlers have taken extra steps toward purity with decontamination after blow molding of the preforms. Even the slightest traces of oil can result in altered or toxic product batches and health hazards for the consumers, recalls and reputation damage, as well as costly production downtime and cleanup.

“Nobody wants oil, in any form, in their finished products,” says general manager of Atlas Copco Crepelle, Stefan Vertriest.

“Air used to blow drinks containers is typically up to 40 bar pressure, and that blown air has to come into direct contact with the inside of the bottle. In terms of end product purity this air should definitely be free of all contaminants, and especially free of oil,” he adds.

Water bottling, juice bottling, carbonated drinks containers, and tea bottling is a rapidly growing market. When consumers reach for refreshment it is vital for the health of the brand they choose that cleanliness and purity is part of the complete product. A brand recall because of potential toxicity would damage the drinks manufacturer, and surely see irreparable damage to the PET bottle provider.

Whereas filters have provided protection in the past Atlas Copco has recently brought to market a new and innovative solution that removes any chance of oil contamination, through its 100% certified oil-free air compressor, in the form of the ZD range.

“The ZD compressor eliminates any risk of oil contamination by virtue of the design itself. At 40 bar delivery there is absolutely no oil detected, which is a major difference with this product from any offering by our competitors and rivals.”

Atlas Copco’s main rivals have deployed oil injected compressors, in which filters are the primary line of defence.

“They brand this as technically oil-free, but obviously this isn’t 100%. It’s almost impossible to guarantee that the air is completely free of oil, in residue, vapour or aerosol form this way,” adds Vertriest.

The ZD range is a two-stage screw compressor, combined with a piston compressor, which means in the part of the machine where the air is compressed, there is no oil present at all.

“Of course, oil is used in to lubricate the moving parts of the equipment, but this is totally isolated from the compression chamber, in both the piston compressor and screw chambers.

Production line

Beyond toxicity, oil-free air means that the problems associated oil traces on valves is removed. When valves and actuators come into even atmospheric coated with oil vapours, build-ups begin and their functionality is reduced.

This not only impacts efficiency, but also maintenance costs and associated downtime costs.

“Oil contamination can spread through you assembly chain and get onto the actuators impacting, for example, the capping equipment, and associated packaging machinery such as the labelling technology,” says Vertriest.

Testing of the Atlas Copco ZD compressor was carried out by the Technische Überwachungs-Verein (German Technical Monitoring Association, or ‘TÜV’), using the most stringent test methods available.

All possible forms of oil contamination as liquids, aerosols and vapors, were measured at three different temperatures (20°C, 40°C and 50°C) and at different pressures (25, 30 and 40 bar) at the measurement point. Even at full capacity, no traces of oil were found in the output air stream.
 

The ZD uses a combination of oil-free rotary screw technology for the first two stages and piston technology for the last two stages.

“By stepping the air pressure up in four stages there is less stress on each section, which reduces wear and tear and prolongs the lifecycle of the compressor. Although this adds to the manufacturing costs at our end, the benefits significantly outweigh this,” says Vertriest. 

By deploying a four stage compression cycle the pressure ratio at each stage is reduced. With the reduced operational stresses this precipitates, Vertriest says the machine can operate reliably for longer.

Additionally, by using additional compression stages energy consumption is lower, as pressure increases are incremental.

Energy costs are skyrocketing all around the world, and even in the Middle East, which has traditionally been a low-cost energy environment, this effect is being felt by PET bottling manufacturers.

“Of course, it depends on the energy cost in your region, but the payback period is well within the lifecycle of the compressor – many times over in fact.”

To combat energy price concerns Vertriest says maximising efficiencies with the new series of compressors was a focal point. “Thermodynamically, the four stage build-up is 7% more efficient compared to a three stage build-up, so energy costs can be kept to an absolute  minimum.”

Because the ZD use a two-stage compressor, the air is brought up to 10 bar first, and then onto a second piston driven compressor where the pressure can be stepped up to 40 bar.

More pressure can be generated by the first stage than is needed for normal operations, so that extra capacity can be diverted elsewhere in the system, such as the packaging process. Additional investment in low pressure compressors is unnecessary.

“Essentially PET solutions are becoming ever more popular. I don’t think this technology will necessarily revolutionise what applications we see for PET, but what it does do is raise the standard of quality and creates a more environmentally sound and cleaner end product,” he concludes.