With the rapidly escalating cost of electricity there is an increasing focus within industry on the energy consumption of air compressor systems.
It has been estimated that these systems account for some 12 percent of industry electricity use, so ensuring that they are efficient in their operation should be a high priority.
Air compressor system audits can provide an important means of establishing the efficiency of systems and identifying precisely where energy losses are occurring.
However, no Australian Standard currently exists for the conduct of audits and this can place system users in a potentially difficult situation when it comes to selecting an audit provider.
According to national key account manager for Air Audits at CompAir Australia, Gilbert McLean, it is important to take a total systems approach to air audits, with a particular focus on the demand side.
“Typically, some 10 percent of energy savings can be made on the supply side while 20 percent or more of savings can be achieved downstream of compressors on the demand side. As well as reduced costs, this means a reduced carbon footprint for the user company,” McLean told Manufacturers’ Monthly.
“Other benefits of conducting an air audit include improved plant and process productivity, safety benefits, improved product quality and lower rejection rates, greater equipment reliability, and less plant downtime.
“A total systems approach includes measuring the power consumed by compressed air equipment, distribution of the compressed air to the point of use, leaks, and the compressed air consumed at major points of use.
“However, there is often too much focus on the supply side of the system. It is quite possible to put the best performing compressor into a system and not get the best end result.”
McLean points out that in many plants compressed air leaks may represent the single largest system loss and that this can mean, on average, a loss of 30-50 percent of compressed air production to leaks.
“Australia does not currently have a guideline Standard to carry out compressed air assessments, but this is set to change in the near future with the establishment of an Australian Standard based on the American Standard ASME-EA 4 (2010) and the forthcoming ISO 11011, due to be released in 2012/13,” he said.
“Air audits conducted by CompAir currently meet or exceed the requirements of ASME-EA 4 (2010).”
Different methods and standards
Oil free division business development manager at Atlas Copco, Graham Dacombe, observes that various compressed air suppliers have different methods, standards and equipment for carrying out audits.
“This situation is self generated by individual suppliers and needs to improve. An important initiative is the proposed introduction of an Australian Standard to provide guidelines for auditing compressed air systems,” he said.
“It is important that a plant is properly profiled and that the right technology is provided for individual applications because different air compressor system technologies have different advantages. It’s about the right machine for the right application.
“In a multiple machine installation it is important that the correct control technology is installed as there are differing ways to set machines up. Equally important is that the reticulation system is properly laid out and continually checked for leaks.”
Atlas Copco’s AirScan service is designed to provide a complete system survey to identify areas where potential savings can be made.
Graham explains that the survey measures, audits, and reviews every element of a compressed air system in detail, which can include flow, power, pressure drop, air quality and leak checks.
“The validation audit is the security for the customer to ensure the effectiveness of any installed solutions, and assessment of the projected savings.
“A key objective is to determine an acceptable operating balance that is both within the capabilities of the compressors and is also adequate to satisfy production requirements at minimised running costs.
“An accurate account of a plants’ compressed air demand over a 7-day cycle is provided to identify energy costs and where savings are possible. A critical part of this process is leak detection, as leaks typically account for 20 percent of the system demand.” he said.