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Choosing the right air compressor

The latest compressors can save manufacturers thousands of dollars every year, but as Alan Johnson reports the amounts saved depends heavily on the application. 

Unlike traditional air compressors, the motor and drive train on Atlas Copco’s GA VSD+ share one drive shaft and are vertically aligned to allow a smaller footprint.
Traditionally air compressors just sat in the corner of a factory or workshop chugging away day after day with little thought given to its operating efficiency apart from maybe the occasional service.

But today, any manufacturer who adopts this strategy could be wasting thousands of dollars in energy costs every year.

The latest air compressors on the market are vastly more efficient and can offer manufacturers considerable on-going energy savings, but only when the correct air compressor for the application is chosen.

David Brown, Product Manager – Industrial Air Division – with Atlas Copco Australia says the key to selecting the right air compressor is to conduct an air audit to find out exactly what a company’s air demands really are.
“Atlas Copco can conduct an air audit, completely free of charge, and confirm and guarantee what savings the company will make once the new air compressor is installed. There are never any unwanted surprises,” he said.
“When we carry out an air audit, we are looking at the variations in demand. 
“We can then put the audit data into our unique, software package and turn the fluctuations into dollars, which ultimately gives the customer the energy savings possible. 
“Very few other companies can offer this service and simulate the savings,” Brown said.
Energy savings
While VSD (Variable Speed Drive) compressors are very popular machines with manufacturers, Brown admits they are not always going to give companies big savings in every application.
“If a manufacturer has a constant, steady demand, a VSD compressor is not going to save them a lot of money. A VSD compressor will only save a company money when there is a fluctuating demand.”
Brown says he comes across this quite a lot, where people think a VSD will automatically save them money. “That is not always the case.”
“If we can’t get a payback period of a VSD compressor of less than two to three years, we don’t always promote that as being the right machine.” 

However in most cases, he says companies with fluctuating demand can achieve a payback within 18 months to two years, though sometimes it can be less than 12 months.
“The key is to conduct an air audit in the first place. After the customer has bought and installed the compressor, we will conduct another audit a month or so later and show the customer the savings are there, which we guarantee will be there.”
Brown says most sales are upgrades where their existing compressor is getting old and inefficient, and costly to operate.
“For example, we conduct an air audit and simply replace a 37kW compressor with a 37kW VSD compressor, normally saving the company 30% on its energy costs.”
He pointed out that energy costs are by far the largest proportion of the overall cost of an air compressor, with the purchase price only 10% of the lifetime cost of the machine.
“The general consensus is that energy costs make up the bulk of the overall cost, around 75%, with ongoing maintenance making up the other 15%,” he explained.

VSD compressors
Brown pointed out that Atlas Copco, as the largest manufacturer of air compressors in the world, is able to supply the right air compressor for every application.
However he warns that this is not always the case, with VSD compressors from some other manufacturers using a standard drive motor and fitting an “off the shelf” invertor drive package. 
“The problem with this arrangement is that when the standard motor is running at low speed, there maybe cooling problems because the cooling air flow is lower than its design flow. The correct arrangement is to use a motor designed for VSD control.”

Brown explained that the very latest design of VSD compressors from Atlas Copco, the radical new GA VSD+, utilises oil cooled, interior permanent magnet (IPM) motors, where the motor shaft and element shaft are one, eliminating all drive losses. Meaning there are no gears, belts or shafts to maintain.
“These are brilliant machines. The power savings alone are significant enough to justify investing in a new machine.”

He said the GA VSD+ compressor offers a major leap forward in FAD (Free Air Delivery) with improvements of up to 12%, and a breakthrough in energy-efficiency requiring on average 50% less energy than a comparable idling compressor. 
“Plus it’s much quieter than other air compressors on the market; down to an unbelievable 62db(A).”
Brown explained that with the GA VSD+ compressor, Atlas Copco started with a clean sheet of paper back in 2007, and evaluated every part of an air compressor including the motor, cooling, drive train, electronic components, and air intake system.


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