Eliminate Inappropriate Uses of Compressed Air and Save Big $$$
Compressed air generation is one of the most expensive utilities in an industrial facility. When used wisely, compressed air can provide a safe and reliable source of power to key industrial processes. Users should always consider other cost-effective forms of power to accomplish the required tasks and eliminate unproductive demands. Inappropriate uses of compressed air include any application that can be done more effectively or more efficiently by a method other than compressed air. This table below provides some uses of compressed air that may be inappropriate and suggests alternative ways to perform these tasks.
This table shows inappropriate uses of compressed air in an automobile assembly plant. The plant took several action steps identified in the table to eliminate or reduce these inappropriate uses. Peak flow is identified in cubic feet per minute (cfm). The plant audit showed that the energy used to generate the compressed air averages 18 kW/100 cfm. The aggregate electric rate at the plant is $0.05 per kWh.
Annual savings = [kW per cfm] x [cfm savings] x [# of hours] x [$ per kWh] = 18/100 x [(150 x 6,500) + (1,000 x 5,000) + (800 x 3,500) + (750 x 3,500)] x $0.05 = $102,600
Net savings: Calculate electric energy costs for the motor-driven vacuum pump, fans, and actuators, and subtract these costs from the annual savings calculated to determine the net savings. Note that there will be a one-time cost of installation for the added equipment.
- Walk through your plant and identify all compressed air uses and, if possible, the flow and pressure requirements of each use.
- Take steps to eliminate any inappropriate uses. Consult with Air Technologies air systems specialist to see if other equipment (blowers, mechanical or hydraulic devices) will be more cost-effective for those applications.
Cashman Equipment Company is a Caterpillar dealer that operates several locations. They not only sell CAT equipment, but they rent it, service it and sell parts. One of their locations was in need of updating its compressor to provide air for the technicians’ tools and a large paint booth operation.
Cashman Equipment used a 100hp air compressor for plant air that operated at 10% load. It was like having a 400watt light where 100watt would have been adequate. Additionally, when it powered up it spiked their electrical usage causing a very high demand charge each month. “We knew we had to change”, said Jim Cox, Facilities Control Manager.
Cashman looked at several options but it soon became clear that the savings would be with a variable speed drive compressor. The local Atlas Copco dealer, Summit Industrial Equipment, “helped every step of the wayfrom usage analysis to assisting us with the financing,” said Cox.
Cashman Equipment purchased the Atlas Copco GA 50 Variable Speed Drive compressor. It’s specially built to follow the fluctuating demand for air by varying the speed of its drive motor. This reduces energy consumption to a minimum by completely eliminating unloaded power consumption, usually saving up to 22% on thetotal lifecycle cost.
For Cashman they found these savings to live up to their expectations. They installed their GA compressor in the middle of July in 2002. “The first month we saved over $1,000 in our electric bill. And we have consistently had that savings all along,” explained Cox. Another benefit for Cashman is that the compressor is much quieter to operate. As a result the unit was placed inside their main shop building making servicing easier as well as providing a little additional heat for the building in the winter. In the summer months, a roll up door adequately cools the unit. Besides the fact the compressor has saved money on energy, Cox is happy with the constant pressure control. “We find it to be very stable and meets all the demands placed on the unit.” Cox sums it up, “We are ecstatic about the varying air demand pattern. We find that the motor speed regulation is the most efficient compressor control method we’ve seen. We’re enjoying the energy savings and the support we’ve received from our dealer and the whole Atlas Copco organization.”