Aluminum Furnace Maintenance Tips

Reducing Operating Costs:   Checking your furnace for natural gas and atmosphere consumption 

Gas Consumption - Compare usage to historical data; BTU per pound will vary between different types of furnaces and process temperatures, and upon the size of the load in a given furnace. It takes much more fuel to process a small load in a big furnace.  Also, BTU per pound goes up if there is a long soak.  An increase in gas consumption can be caused by any of the following:

• Air leaks into the furnace - This is perhaps the biggest cause of extra fuel consumption. Look for leaks at door seals, car bottom seals, etc.
• Negative furnace pressure - Negative furnace pressure causes air to leak into the furnace, which causes the burners to fire harder. Make sure that pressure dampers or electronic pressure control maintains a slightly positive pressure in the work zones at all times.
• Excessive positive furnace pressure - This causes excessive amounts of heated furnace atmosphere to escape around any openings into the furnace. The correct furnace pressure is as little as possible to run the process successfully.
• A combustion system that needs adjusted - Combustion systems are sometimes adjusted too lean. Excessive amounts of excess air have to be heated to the process temperature. Most combustion systems run with as little as 10% excess air.

Atmosphere Consumption - It takes 4 to 5 furnace volumes to purge a furnace, and 1/2 to 1 volume per hour to hold it during heating, and 1-1/2 to 2 volumes per hour during cooling; or, you can check historical usage per cycle.  If you are using more than this, you either have a problem with your flow control system, or air is leaking into the furnace.

Where to look for leaks:

• Door seals
• Shaft seals on fans and any dampers, etc.
• Gaskets on any component plugs or access covers
• Cracked welds in the shell or areas that were never welded
• Cracked radiant tubes
• Packing on radiant tubes - for expansion

The latest design, materials and equipment specifications should be obtained from the company before any reliance is placed on the enclosed since changes may occur due to product improvement.