Compressed air: the most expensive energy in a production facility

This is the second blog in a series, contributed by Festo Corporation, that focuses on reducing the operational costs of pneumatic systems and discusses how users can get more throughput while using less energy. According to Festo, “This is the goal of every manufacturer, but in order to optimize usage, machine builders and manufacturers alike need accurate information on the energy they consume.”

Another factor regarding leaks is something referred to as artificial demand. The higher your supply pressure, the more air your leaks will consume, creating a greater demand on your compressor. By reducing the supply pressure, you can greatly reduce the amount of air that is required to be produced by your compressor. For example, a 1/4” orifice at a 110 psi supply pressure will generate a leak rate of 72 cfm. The same 1/4” orifice, with the supply pressure reduced to 60 psi, will generate a leak rate of 43.6 cfm; a reduction of nearly 40%. Taken another step further, the financial gain by keeping the system pressure lower, just seen at this one leak, is as follows:

60 psi supply
43.6 cfm x 525,600 min/yr x .00024 ¢ per cf (1) = $5499.88 per year

110 psi supply
72.0 cfm x 525,600 min/yr x .00024 ¢ per cf (1) = $9082.37 per year

By simply reducing the main pressure the artificial demand created by this leak at 110 psi is reduced and a customer can save $3582 per year for this one orifice alone.

Figure 1: Results of a customer survey by Festo

In addition to leaks, the inappropriate use of air accounts for a large percentage of wasted compressed air. In many factories, hand held blowers, pneumatic vacuum generators and coolers all contribute to this. Figure 1 represents actual recorded data from an air audit performed by Festo. Although the customer was vigilant about keeping air leaks to a minimum, their inappropriate uses of air consumed over half of the compressed air. By replacing these commonly used apparatus with low pressure devices, machine builders can dramatically reduce the requirement for compressed air. Additionally, restricting the flow of air to inactive or inoperative equipment will also greatly contribute to energy savings.

There are many companies offering audits for compressor rooms and leakage elimination for the distribution systems. However, once the piping enters a machine most of these services stop. Compressor technology and pneumatics, even though both deal with compressed air, are two very different fields. Compressors represent the supply side, whereas pneumatics the demand side. These two types of audits are rarely offered together, since the two fields of expertise are rarely found together.

If the agenda is to save energy by optimizing the air usage, what service would make most sense? The answer is simple, both! The supply side can be optimized to fulfill the demand in a more efficient manner, but unless the demand is optimized the compressors will still supply more energy then actually needed. The demand side can be optimized by reducing air usage, but besides an increase in throughput and stable pressure levels not much energy is saved due to continued running of the compressor.

Servicing the demand side ensures the lowest possible demand with maximum throughput followed by a supply side service/adjustment to compensate for less demand and inefficiencies. Now the energy savings are even higher than having done both services independently. The important thing to remember is that supply side services do not compete with demand side services, but rather add value to each other. With optimized demand side, one can expect to save up 35% in energy savings. Combined with a compressor audit, the savings can be over 50%.

Stay tuned for next week’s blog highlighting machine level audits compared to compressor audits.