Lower-cost compressed air

Air compressors can be costly to run, but knowing your system requirements is the first step to reducing unnecessary expenditure. Sarah Falson reports.

GOVERNMENT and industry have been working together to adopt more efficient processing methods for some time, however with the carbon tax now claiming a percentage of profits, and power bills increasing by the month, manufacturers need to think seriously about techniques to protect their hip pockets.

[Image, right: Air audits can be negotiated as part of a customer’s service contract.]

Air compressors are identified as one area where savings can be made, however simply turning off a piece of manufacturing equipment when production runs around the clock is often not an option.

“Historically air compressors have been large, cumbersome and inefficient pieces of equipment, which was fine when electricity cost 1 cent a kW/h,” Southern Cross Compressors Australia national sales & marketing manager, Mark Ferguson, told Manufacturers’ Monthly.

“[However] electricity costs are now around 15-25 cents per kW/h and expected to increase about 15% year-on-year.”

Victoria’s Southern Cross Compressors is one of a growing number of equipment suppliers specialising in lowering the cost of compressed air.

Another is global supplier Atlas Copco Compressors Australia and, according to product manager, Compressor Technique Service, David Irwin, it is now possible to save up to 30% of the energy currently used by air compressors – but manufacturers will have to make an investment up-front.

“It is a two-edged sword. Customers need to spend money to save money in the long term, and this is not always easy to justify when the wolves are not too far away from the door,” he said.

Reducing unnecessary costs

Lowering the cost of running an air compressor is all about reducing unnecessary load on the equipment. According to Irwin, “The lower the pressure the less it costs to produce the compressed air, so reducing pressure losses throughout the system actually helps reduce your cost. For every 1 bar pressure loss you use 7% more energy.”

National sales manager Mark Dudman of global air systems supplier Kaeser Compressors Australia says using the wrong sort of compressor for your application, pressure loss caused by a ‘leak’ in the system – including in the pipes, connectors and valves – and the design of the compressor itself can all cause pressure loss.   

“Using multiple compressors into too small a size header, too many filters, undersized pipe reticulation, and incorrect reticulation materials – for example using a rubber hose instead of compressed air pipework – can all mean pressure losses >1 bar,” he said.

“The costs are not only in power consumption but also in servicing the compressors and ancillaries. If the compressor is running excessive hours just to support system leaks then that adds cost for no purpose.”

The ideal pressure at which a compressor should run for maximum cost savings differs depending on the application, which can range in pressure from 4 bar to as high as 40 bar.

Atlas Copco’s Irwin says that although pressure loss can never be eliminated entirely, manufacturers would do well to invest in a compressor that has been designed with efficiency in mind.

“Pressure loss starts at the compressor and the efficiency of the design so that the compressed air can get from the element to the outlet with as minimal pressure loss as possible,” said Irwin.

“Integrating dryers and line filters also significantly helps in this regard, but the dryer and filters must be truly integrated into the design of the compressor, and not just bolted on to the compressor outlet.

“The quality of the line filter elements also makes a significant difference; buying a cheaper and poorer quality element will save money up front but will cost you more in the long run.”

Some compressors offer built-in controllers, which help to reduce power consumption by continually monitoring an air system’s requirements.

“Easy-to-use control systems are capable of upholding compressor operation and air delivery cutting in or out according to the air demand, without compromising efficiency,” said Kaeser’s Dudman.

Help at hand

Many manufacturers face problems allocating time and resources to maintain their compressed air systems, only paying attention to the equipment when there is an issue.

One way to reduce break-downs, downtime and energy bills is to pay for a professional to conduct an ‘air audit’ on the compressor system to identify problem areas and advise where cost savings can be made.

Audit prices range from hundreds to thousands of dollars depending on the requirements of the site, and manufacturers can either appoint a third party to perform the service or purchase equipment from a supplier that factors the cost of audits in to a customer’s service contract.

According to Atlas Copco’s Irwin, manufacturers should make sure that the company performing their air audit provides a detailed report on the expected cost savings related to fixing any problems in the system.

“Measuring the air consumption is only a start; the real trick is to be able to accurately simulate energy efficiency gains against alternate energy saving equipment,” he said.

Servicing downtime is also something to think about, however as long as the equipment is right for the application, production loss can be minimal, Irwin says.

“A well set up air system will have strategically placed isolation valves so that the affected area can be shut down and rectified without causing disruption. Some customers carry out rectification work in a down time period like a weekend,” he said.

Southern Cross Compressors’ Ferguson adds that pending air audits regulation, it is sometimes difficult for manufacturers to know who to go to.

“There are currently no official standards in Australia for conducting air audits so manufacturers should be careful to select a reputable company to conduct air audits,” he said.