With electricity costs continuing to rise, many manufacturers are still failing to realise that compressed air is their most expensive utility. Alan Johnson reports.
Chugging away in a corner of almost every factory sits the ubiquitous air compressor, often totally ignored (until it breaks down). However, according to industry professionals, this is a very expensive strategy.
For when it comes to operating costs, research shows that it takes 7 to 8hp of electricity to produce just 1hp in an air tool, yet this high energy cost is often overlooked by manufacturers.
Nash Bakhit, Product Manager with Atlas Copco, says companies who ignore their air compressors are making a costly mistake. “It’s false economy.”
“My advice for manufacturers is to monitor exactly how much air they actually need, and be aware of their energy consumption used to run their compressed air system.
“The cost of the electricity used to run a compressor can add up to 70% of the total cost of running a compressor,” Bakhit told Manufacturers’ Monthly.
“Manufacturers should be aware, however, that there are numerous energy management systems available, all designed to reduce energy consumption in many different ways, including heat recovery systems, compressor control systems, which can control up 30 compressors, plus air and energy audits.
“It’s also false economy for companies to ignore their compressor’s maintenance schedules, or to run their machines flat out all day and every day with no maintenance. I’ve seen companies who have done this and needed to replace their machines in under 5 years. That strategy is crazy,” he said.
Bakhit suggests a good first step for manufacturers is to invest in an air measurement survey.
“With our specialised equipment, we can measure the air flow, the air pressure, and take some power measurements from the compressor.
“We then compare all these measurements and provide the client with a better solution than the existing system.”
Bakhit says he can recommend a number of different options, ranging from cost-effective compressor management systems right through to the latest energy-saving VSD (Variable Speed Drive) compressors.
“For example, a company might have four or five air compressors running all the time, sometimes running unloaded continuously. This scenario is wasting a lot of energy, and money.
“But with our ES central controllers we are able to manage these air compressors based on demand.
“When demand is low, for example, we can set the limits so only compressor number 1 is running, but when more air is needed it will select compressor number 2.
“Then if we have high demand, the controller might select the highest capacity compressor, say number 3, and stop 1 and 2. It’s a very good system with a number of variants.
“With the central controller, a company’s most economic and efficient machines are prioritised to reduce downtime and match workload requirements,” he said.
Bakhit explained that the system works on any brand of compressor, it doesn’t have to be Atlas Copco machines.
“And if the machine is quite old, and a competitor’s machine, we have a Comms box, what we call the translator, to translate the compressors communications to the controller to understand its language and manage up to five compressors.
“The ES central controller is a very cost effective option, because if the machines old but still serviceable, we can manage the compressors efficiently, plus manage the maintenance of the compressors.
“So rather than just sell the customer new machines, we are able to offer the customer a number of options depending on the applications.”
Bakhit says to help customers further reduce costs; the controllers are able to accurately control the pressure in the system.
“For example, a standard load and un-load compressor would run on a pressure band of 1bar, but an ES controller can minimise that to 0.5 of a bar or less.
“The lower the pressure, the lower the losses, less energy consumption and lower energy cost,” Bakhit explained.
“Manufacturers should know, a properly managed compressed air network will save energy, reduce maintenance, decrease downtime, increase production and improve product quality,” he said.
Bakhit says waste heat recovery systems are another way for manufacturers can cut their energy costs; by reusing the heat generated by the air compressor for a variety of applications.
“The systems are becoming increasingly popular in Australia; they are not just for European companies.
“One local manufacturer, for example, is using the heat generated by the factory’s air compressor to heat the company’s hot water system; for the workers’ showers etc. It’s basically free hot water.”
Bakhit said in another application, the heat generated by the factory’s air compressor is used to heat boilers used in the manufacturing process.
“Wherever a company uses heat in its process, the system comes into the equation,” Bakhit said.
To further reduce operating costs, Bakhit says the companies load/unload air compressors offer two pressure band running positions.
“What this means is that during the day the machine can run on an average of 7 bar, or it could be 8 or 10 bar, whatever the factory needs during the day.
“Then during the night, when there’s not much load, the machines can run on a lower pressure band which could be 4 bar or if no air is needed say between 9am and 6am we can have them on a programmed stop. With a VSD, when no air is needed, the machine will stop completely.”
Bakhit explained that VSD compressors run based on demand, if higher air flows are needed, the machine will ramp up to maximum speed to provide maximum air flow.
“If minimum air flows are needed, the machine will ramp down to idle speed to supply just the air needed, or even stop if no air is needed.”
Bakhit says companies can expect an ROI of less than three years with VSD compressors, in some cases.
“It really depends on the site and the application, and sizing the compressors correctly,” he said.
Bakhit acknowledges that nearly every compressed air system has some air leaks, but to varying degrees.
“Air leaks in a system can cost a company huge amounts of money.
“In some cases, the leaks in the system are so bad that we see machines running just to feed these leaks.
“So if we can find and stop these leaks we can make substantial energy savings,” he said.
Bakhit explained that one of the company’s energy management systems measures not just the air flow and pressure, but also an air leak detection survey.
“We take some ultrasonic measurements of the air, and with some quick calculations we can give the customer an idea of what these leaks are costing the company and how much it would cost the company to fix the leaks.”
He admits some leaks are so small that they are not cost effective to fix, but says most are.
“When a customer sees that the factory’s air leaks are equivalent to a 45kW machine running 365 days a year, he starts to take the air leaks seriously,” Bakhit concluded.