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Curtailing compressor energy use

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AS petrol prices and electricity costs soar, savings-conscious manufacturers are focusing on their air compressors, which are often the largest energy consumers in the factory.

Atlas Copco’s general manager, Ignace Cappuyns, said compressors with on-board frequency converters remain the most energy efficient options for most manufacturers.

“The combination of a frequency converter with the classic mechanical compressor is actually still the number one possibility to reduce energy consumption,” he told Manufacturers Monthly.

Cappuyns said using such compressors could result in daily energy savings of up to 35%, adding up to significant dollar savings each year.

Cheap but not cheerful

Cappuyns said cheaply priced air compressors from emerging markets such as India were beginning to enter the Australia market and these might prove tempting to some manufacturers. He warned these imports typically offered only very basic features and it was not clear whether they would meet Australian standards.

There was also a danger that the imported compressors could fail more quickly than locally made compressors and their suppliers would not offer the same level of support as could be expected from suppliers of locally made products.

“When they fail of course it costs a certain amount of money to repair, but it’s rather the interruption of production which can lead to a huge cost compared to the relatively small difference in the cost of the compressor,” he said.

Compressors are critical to operations in many factories and Cappuyns stressed the importance of considering the costs and benefits of a compressor before making a choice.

“It’s all very nice to pay a very cheap price but the risk has to be assessed: What does it mean if everything fails and you just cannot operate the factory any more?” he said.

Cappuyns said manufacturers should look at the lifetime costs of the compressor rather than simply the purchase price.

“We know that about 70% of the cost over the lifetime of the compressor is energy and only 30% is purchasing, installation, maintenance…to make a small difference and invest more on the purchasing side will save a huge amount of this 70-75% of energy that they’re paying continuously,” he said.

Domnick hunter business development manager John Davis agrees manufacturers can make enormous savings by paying closer attention to their air compressors.

“Air compressors are often among the single largest energy consumers; unfortunately they are also often one of the largest energy wasters, with up to 40% of energy being consumed unnecessarily due to poor design and quality of the compressed air system,” he told Manufacturers Monthly.

Davis suggests manufacturers conduct, or seek assistance from suppliers in conducting, an audit of their compressed air systems.

He explained such audits would typically suggest methods of maximising the efficiency of a compressed air plant by measuring system pressure, temperature, dewpoint, airflow, particle count, oil and water content and gas composition.

“Air leaks are identified using ultrasonic detection, and finally a report is produced identifying cost of the customer’s existing compressed air system, its deficiencies and recommendations to improve overall efficiency,” he said.

Air quality

Davis suggests manufacturers shouldalso have the quality of their compressed air tested.

“The quality of air required throughout a typical compressed air plant can vary,” he said.

While Davis noted it was important to ensure compressed air was clean enough for the operation, he added there was no point in over-cleaning air as different applications required different levels of air purity.

“For example, air to be used for pneumatic conveying of food stuffs or ingredients requires the highest level of purification, whereas air used to operate pneumatics for production machinery may require only general purpose protection.”

Davis said over-cleaning compressed air and using outdated or inefficient filters could create unnecessary costs for operations through additional filtration equipment and excess energy consumption.

“Ordinary filters have always consumed too much energy, as they are by design, a restriction to air flow. During their working life, this restriction increases dramatically, and typically over one year, they can consume more energy than they are worth.

“Technically, service life is dependent on differential pressure. Most manufacturers recommend a replacement filter element at between 50 and 70kPag differential. This will cost the user a massive 5% extra in compressor energy. This is like driving the compressor with its brakes on.”

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