Compressed Air Cost

[submarinesailor]

While reading Red's latest post about compressed air causing a fire over at the "What did you learn at the latest project" thread.  I remembered some of my Certified Energy Manager (CEM) training and a project we did at the Pentagon's classified waste incinerator.
The training touched on two things about compressed air:
1.   The efficiency of a WELL maintained air system was only about 11% - that's work in to work out.
2.   Depending on several cost factors, compressed air could be your 2nd, 3rd or 4th most expensive utility.  The biggest cost factors being the cost of natural gas/propane/water/etc....

The project at the waste incinerator allowed us to reduce their daily electric cost from about $156 per day to about $52 per day.  The biggest change occurred when we had them make some mechanical changes that in several steps greatly reduced their air consumption.  The first changed allowed them to turn off one of their 50HP compressors at night causing a drop of about $20/day.  The next step was the big one.  Changing out 2 – 5 MMBTU pneumatically controlled gas feed valves with electrically controlled valves – along with adding a manual backup valve for safety.  This change allowed them to run only 1 compressor during the day and shut down both of them at night.  NOTE: Also got them to start alternating compressors on even and odd days reducing their compressor PMS – additional tax dollar savings.  The shutting down of these compressors at night knocked an additional $70/day from their operating cost.  Several other smaller changes added about $10-15 more in electric cost saving. 95% of the savings was compressed air cost.
 
Remember to turn off your compressors when they are not in use.  Also fix any and all air leaks.  They add up real quick.

[Don P]

On jobsites where my compressor lives while we build and in the shop down below I'm always worried about a blown hose overnight causing the compressor to kick on and run continuous, overheat and cause a fire. I try to remember to shut it off at night.

In one shop we had an aftercooler let go on the big compressor. I just heard a boom and saw sparks so ran around the corner with an extinguisher. The flying red hot metal ran me right back around the corner. Very impressive what escaping air can do.

[Corley5]

Once upon a time somewhere I read that air compressors and battery chargers are the two main causes of garage/shop fires.

[PineNut]

I have an air compressor in my home shop and I have been concerned about the dangers of leaving it on. So I installed a switch for the compressor right beside the light switches. It is very easy to overlook a switch so I installed a large pilot light right by the switch. Not 100% insurance that it will be turned off but it is far better than none. 

[Larry]

I had a big Chinese compressor that broke a rod while running.  Made a large racket and quite possibly could have caused a fire if unattended.

I replaced it with a 10 HP Champion rated for continuous use.  Still made me nervous so I wired a small switch in the coil circuit for the motor starter so I can turn it off. While doing that I also wired in a light which is on when the compressor is on line.  Makes it easy to remember to turn it off.

[submarinesailor]

On jobsites where my compressor lives while we build and in the shop down below I'm always worried about a blown hose overnight causing the compressor to kick on and run continuous, overheat and cause a fire. I try to remember to shut it off at night.

In one shop we had an aftercooler let go on the big compressor. I just heard a boom and saw sparks so ran around the corner with an extinguisher. The flying red hot metal ran me right back around the corner. Very impressive what escaping air can do.

Don P - I truly know what you mean about running the other way.  Was involved in a 4500 psi blow out on a submarine many, many years ago.  Can't tell you how many hundreds of man hours we had in repairs.  Add in the all the hours for the shipyard tiger team's welding and testing.  Man was it a big, messy repair.

[scsmith42]

Very insightful info Bruce, thanks for sharing.

I always shut off my compressor at night or when I'm not around the shop. Fire scares me...

[screwsloose]

One cold morning when i got up i hurd my compressor running in the house. Its not loud in the house but i can hear it. 5 minutes later i went out to stock the furnace. Its still running. It never runs that long. Went out to check and the pressure regulator adjusted itself up which set off the releif valve. Because it was cold outside and the furnace wasnt running the air coming out of the tank caused ice buildup on the releif valve. Now there isnt enough pressure in the tank and the compressor was stuck on. The valve for air supply was in the off position.  I usually turn off the air supply but rarely turn off the power. I got to thinking, i always turn the light on when i am in the shop. So I bought the supplies to wire my air compressor into my shop lights. It consists of a 240v 30 amp relay with a 120v coil to activate it and a box to put it all in. This set up will handle the compressor load and when i turn off the lights at the end of the day the compressor is automaticly off with the lights. Now to find the energy and time to do the install.

[Raider Bill]

I always keep my shop compressor on.  After reading this thread that will change.