In these financially difficult times, compressor users can’t afford to let energy efficiency disappear into thin air. Katherine Crichton writes.
WITH Kevin Rudd setting a new target to reduce emissions up to 25% below 2000 levels by 2020, industry needs to ensure it is adequately prepared for the brave new world of carbon permits, carbon trading, and the plethora of reporting schemes that have been created to monitor energy efficiency.
With air compressor systems one of the biggest culprits of energy wastage on the factory floor – said to use up to 30% of a plant’s total energy consumption – it is in everyone’s best interests to ensure systems are working to optimum capacity.
Edwin Burwood, CEO of independent project consultancy group Specialty Air, says some systems can waste 70% of their energy usage.
“Compressors are inherently inefficient systems, with generally only around 8% of air making it down the pipeline.
“About 19.7% of the air from compressors are said to come out of leaks on average, with a recent visit to a brand new manufacturing facility revealing 37% of compressed air in losses,” Burwood said.
However, he and Dale Stedman, Specialty Air’s BDM, stress that leaks are just part of the energy efficiency story, telling Manufacturers’ Monthly it is a common misdemeanour that many companies think once they have plugged their leaks, they have solved their air efficiency problem.
“Generally the critical factor is the compressor control systems. Regularly, our Compressed Air Flow and Energy Demand Survey reveals virtually zero energy savings by repairing leaks in isolation, due to the existing compressor control system”, Stedman explains.
“If the control system isn’t designed or set up correctly, you can fix all the leaks on the plant and end up with $0 savings – it’s very important to understand the control system first.”
He told Manufacturers’ Monthly one of the first things the company’s technicians examine when conducting a flow test is the control system on the compressor.
“This is will determine whether it’s commercially viable to repair the leaks.
“There’s a marked difference between the performance curves of a VSD, load/unload machine or a VOC compressor.
“It’s the curve of the control, which will determine how much air you take off before you actually have an impact on the amount of dollars you are actually saving.”
According to Stedman, at least half of his job is educating – or making people aware – of the opportunities to improve their system efficiency not just by plugging leaks.
“Through our flow test, we can identify what the volume of the leak loss rate is across the plant.
“Best operating practice is about 10% because it may not be technically or commercially worthwhile to repair leaks below this range unless there are OHS issues.”
Stedman advises if companies are operating above that figure, it is important they conduct a detailed ultrasonic leak test to identify each individual leak in the plant. He also says it is important to conduct a ultrasonic leak test which will identify what is best operating practice while still being cost effective.
“It is imperative that each leak is tagged, photographed and rated in volume (CFM) etc giving the necessary information to interrogate systems to ensure they run at best operating practice,” he said.
Sounding out leaks
With advances in leak detection equipment, long gone are the days when a bucket of soapy water or the human ear were considered adequate methods of detecting leaks.
While the injected dye method might work for some applications, a newer technology is proving to be able to find leaks under conditions that can severely hinder the performance of other methods.
Designed to be very sensitive to sound, it is said that a good ultrasonic leak detector can actually let you hear the blink of the human eye.
As the name implies, ultrasonic leak detectors identify the ultrasonic sound of a leak, which is particularly useful when it comes to smaller leaks which emit high-frequency sounds too high for the human ear to detect.
It is also said to be one of the most reliable forms of leak detection, a claim which technical support engineer, Nash Bakhit at Atlas Copco, supports.
“I haven’t seen many other methods that are as accurate as ultrasonic technology,” Bakhit told Manufacturers’ Monthly.
“The technology came into prevalence in the last five or six years and now pretty much everyone in the industry uses ultrasonic leak detection.”
And it is not hard to see why this technology is gaining in popularity, as it allows leaks to be identified quickly despite being around loud industrial equipment.
“Because the ultrasonic detector is focused on a specific band of sound – wind noise, voices, traffic, and most normal operational sounds will not be detected.
“Some leaks can be heard from several feet away, therefore access to the leak is not always necessary, as ultrasonic technology can identify leaks from a distance of over 10m,” Bakhit explained.
As long as the leak is turbulent, there will be enough sound to be detected ultrasonically, and Bakhit told Manufacturers’ Monthly that high pressure is not necessary for the technology to detect the air escaping.
Ultrasonics can detect pinhole leaks with as low as 1L/S, however the more pressure behind the leak, the easier it will be to locate.
“In saying this, it is often the quiet leaks that can do the most damage when it comes to air wastage, so this is where ultrasonic leak detector comes into its own.”
For Colin Gilbert, also with Atlas Copco, one of the key benefits of using ultrasonics is not only the technology’s ability to identify leaks, but the fact it can quantify information in terms of flow rate, cost to the system.
The ability to quantify the amount of air leaking out as well as detecting the location and the severity of the leak allows us to accurately calculate exactly how much air is leaking out through a plant’s air line.”