Last week, Lee Evans, Brian Farno, and I attended a seminar entitled “Fundamentals of Compressed Air Systems,” sponsored by the Compressed Air Challenge. Lee and Brian have already written great pieces on what we learned, and Joe Panfalone (even though he didn’t even go) has gotten in on the action too – leaving me to search desperately through my notes for something relevant to discuss. Here’s my initial takeaway: If your blog is published on Wednesday, try to attend the seminar you wish to write about on Tuesday, not Thursday.
One thing that my associates left me, though, was the subject of inappropriate uses of compressed air. According to the Compressed Air Challenge folks, 70% of the savings to be realized lie in measures on the “demand” side of your system. A big chunk of this is the aforementioned inappropriate uses, which were defined as applications that could be performed using alternate methods. The assumption is that these alternate methods are less costly from a compressed air usage standpoint – which is not always the only factor to consider:
*The floor needs to be swept at the end of the shift. It takes 10 minutes with a broom, or 5 minutes with a Super Blast Safety Air Gun (for instance, the Model 1214, which uses 91 SCFM @80psig). Let’s assume labor at a cost of $50/hr, and compressed air at a cost of $0.25/1000 SCF (Standard Cubic Feet):
-Broom: $4.17 labor (10 minutes @$25/hr) = $4.17
-Air: $2.19 labor (5 minutes @$25/hr) + $0.11 compressed air = $2.19
Other situations require a little more data, and math, to quantify. For instance, if vacuum is required for lifting, pick and place, mounting, etc., a central vacuum pump may have lower operating costs than those associated with the compressed air needs of E-Vac Vacuum Generators. When you factor in initial capital cost and maintenance expenses, the E-Vac still compares favorably, though, despite the potentially higher operating cost. I say “potentially,” because a system’s vacuum pump is often located some distance from the farthest point of use. That means it’s spending energy not only to provide vacuum to the remote points of use, but also to overcome the line loss in those lengths of piping. E-Vacs don’t have this problem, as they can be easily installed at the point of use, and sized appropriately.
The last (and I thought, most highlighted) inappropriate use they covered was cabinet cooling. It was explained that even though a vortex tube cooler may cost less, the air consumed will cost more than the electricity required by a refrigerant-based unit. Now, we don’t dispute that…the following comparison shows as much:
Then, the instructor went a bit further (pre-empting a question from Brian, Lee, and I) to validate cabinet cooling as an appropriate use, but only when: the environment was not conducive to a refrigerant-based unit (high ambient temperatures, dusty/dirty/aggressive atmosphere, etc.), AND thermostat control was used. They took great pains to not promote any particular brands of equipment in the presentation of the seminar, but the photo they used to illustrate this was unmistakably an EXAIR NEMA 4 Cabinet Cooler with Electronic Temperature Control. That was worth the price of admission for me.
If you have questions about whether you’re using your compressed air appropriately, or even to its maximum efficiency, give us a call. If we can’t find the answer mathematically from the data available, we can gather the data in our Efficiency Lab. Math doesn’t lie, and neither will we.
Russ Bowman
Application Engineer
EXAIR Corporation
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