What’s the relationship between excess air and your bottom-line? In this article, Jim Roberts, President, U.S. Ignition, shares how to increase efficiency and reduce waste in your heat-treating operations.
This informative piece was first released in Heat Treat Today’s April 2025 Annual Induction Heating & Melting print edition.
A furnace guy walks into a heat treat shop . . . and notices there is a little bit of a yelp to the burners, or the furnace operator mentions the furnace is slowing down on heat up recovery times from a cold load. Or, if you are responsible for fuel costs and monitoring the gas meters, you might notice that situation is slipping in the wrong direction. Or, the burners seem to be dumping soot on your floor. We discussed that in past columns — remember?
Well, it’s all got to do with air. It may seem odd to talk about air when the objective is to utilize fuel at an optimum efficiency, but that’s how we intend to get combustion under control. Let’s go after the air. You remember that we talked about making sure that combustion air sources (blowers, eductors, etc.) were all operating at optimum performance, so the air remains supplied as engineered when the equipment was new. So, now we have our air being delivered at the peak levels we want, but it looks like one of the air valves has shifted, which we covered in the last column on keeping the air sources clean.
This next little tidbit of information is intended to show us all how much this little-considered entity we call AIR can affect the bottom line. Here’s some info you might find interesting.
Eliminate Excess Air
If controls have moved or another phenomenon has caused the burners to lean out, it could cost you a fortune. Most burners are designed to burn with a small percentage of excess air (less than 15%).
Exceptions would include air heating equipment and low temperature drying operations where the excess air is used to control the temperature of the flame. If you operate a burner that has been designed to run at 10–15% excess air and the burner controls or settings drift into the range of 50% excess air (that is a difference of 2–3% O2 or 7.5% O2 in the products of combustion), the difference in an 1800°F oven operation is a calculated 9% loss of fuel efficiency. If you operate a 1 million BTU/hr burner, firing at 75% of the time six days a week for 50 weeks a year, your gas usage would be approx. 5400 therms a year. If we calculate that your gas costs (delivered) are in the range of $4 per 1,000 cu/ft, keeping one burner in tune would save approximately $1,950 per year.
What!!! If you are running a good-sized batch furnace with four burners, that’s a cool $7,800 dollars per year. A ten burner continuous line is going to save almost $20,000 dollars per year. All that just because you cared enough to check excess air levels regularly.
Of course, wasting fuel because you are heating air instead of product is a terrible thing. But don’t forget you can go the other way, too, and go fuel rich with the settings. Then, you take the chance of actually damaging equipment with the carbon you could be producing in a reducing (excess fuel) situation. Carbon can affect all sorts of equipment life, including shortening burner component life and reducing radiant tube and fixture life. It’s not good. Don’t do it. No excess air and no excess fuel will lead you to a happier and more profitable life.
As always, I recommend that you associate your business with the furnace and combustion technicians in your area who can help you make sure everything stays in tune. We’ll chat in the next edition of Heat Treat Today about how to keep a handle on this in-house, so you can tell your experts what you are seeing and start saving yourself gobs of fuel!
For more information: Contact Jim Roberts at jim@usignition.com
