1. Does Your Process Pull a Consistent Amount of Steam 24/7?
How much steam are you producing versus the capacity of your boilers -- over a year's time? If you don't have a meter on your boilers, then answer these questions: Are you running at full fire all the time? Or are your boilers often idling?
Each time you don't use your boiler and it isjust idling, its efficiency drops. By way of analogy, think of a car's miles per gallon in the city versus on the highway. Highway mileage is based on the assumption that your car is running flat out constantly at the same speed, whereas city MPG is based on stop-and-go driving. Likewise, the energy efficiency of your boiler drops when its usage is stop and go.
2. Does Your Steam Demand Go Through Rapid Fluctuations?
To increase the efficiency of your whole system, keep your boilers running either at the highest load possible or have them shut off and cold. The most efficient boiler is a cold boiler.
According to Mark Utzinger of Miura Boiler, Wheeling, Ill., this is why a multiple installation system allows you to keep the boilers that are running at the highest loads possible. When steam is not needed, you can shut a boiler down and let it go cold. To restart quickly, you should have a small low water content boiler. A boiler with a large water tank that must be kept idling so it can go back online in minutes instead of hours is a huge heat sink. It keeps radiating losses all day long -- even when you are not using it.
3. Are You Monitoring Your Air-to-Gas Mixture?
Monitoring to make sure you have a good air-to-gas mixture is critical. This mixture depends on the type of burner you have, so check your boiler's manual. Make sure the burners are well adjusted -- just as you would check your carburetor in your car and change its filter.
The goal is to have the boiler fire well, so you have low carbon monoxide and pollutants coming out of the boiler. These are measured by an analyzer on the stack. All boiler service technicians have the equipment to do this.
4. Do You Need to Decrease Capacity?
Try to keep your boilers at the highest loads possible. If you have old big boilers sitting there, get rid of one or two of them and keep just one running flat out all the time. Install other boilers that can go off very quickly and come back on very quickly for swing loads. That's the best way to keep your whole system optimally fired.
5. When Your Boiler Is Operating Below 100% Capacity, Does Its Efficiency Drop Below 80%?
The equation is very simple: The amount of steam output of the boiler is divided by the fuel input. This is comparing the potential heat by ignition of the fuel going into the actual amount of heat coming out. Output and input are in BTUs (British Thermal Units) per cubic foot. (See sidebar.)