Aluminum Furnace Maintenance Tips

Avoiding Expensive Breakdowns by Adjusting the Water Supply to Fan Shafts and Door Seals

Fan shafts are sometimes water cooled to prevent heat conduction to the bearings. Air cooled shafts operate their bearings at higher temperatures, which can lead to shortened bearing life. Operating at increased bearing temperatures could require special lubrication. Many doors and door seals are water cooled to prevent heat distortion, and to promote long seal life. Any distortion around the door jamb, or seal damage, can allow oxygen and cold air to enter the furnace, which will contaminate the atmosphere and ruin temperature uniformity. 

Most problems with water cooling are caused by debris in the water and water hardness. Water that is hard deposits lime or stone at any point where the water is overheated - even a little. This lime deposit becomes a layer of insulation that prevents the water from properly cooling the metal surface.

The best way to minimize water problems is to set the flow adjusting valves full open.  A partially closed valve can easily stop all of the flow if a small piece of debris comes through the line. Stopped flow will cause failure of a fan bearing and the repair can cause 2 or 3 days of downtime and cost more than $5,000. It just isn't worth trying to save a little water. Running the water line full open reduces the buildup of hardness deposits because the deposits increase greatly when the water gets warmer due to restricted flow. Another benefit is that full flow gives high velocity, which assists in keeping the pipes clean of sediment and algae, etc.

In cases where the plant cooling water system is overloaded and wide open flow cannot be provided, the best system is a pressure regulator in the supply line to the furnace. Valves are still set wide open but pressure can be reduced to reduce the total flow. If debris starts to plug the restriction in the regulator, the regulator will open up to maintain the desired pressure and flow and the debris will be flushed out of the regulator

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.