Furnace maintenance is just as important as automobile and aircraft maintenance. For commercial heat-treatment operations, the furnace is what keeps the cash flow going and pays the salaries of the heat-treatment associates. If the furnace is not maintained and breaks down (for whatever reason), the cash flow stops or the production stops (and irate customers develop).

Remember, for those who operate captive heat-treatment shops and commercial shops, no matter how well the component has been designed and no matter how good the material is, if the heat-treatment operation stops for any reason, no products can leave the manufacturing facility. Heat treatment is the critical operation that will give the components durability and the ability to perform under operating conditions. So, furnace maintenance must be held as a critical operation to the functionality of any heat-treatment shop.

It does not matter if the furnace is a simple air-circulating furnace, a complex vacuum furnace, an atmosphere furnace, an induction heat-treatment system or a simple oven, the unit will require maintenance.

The best person to use as the primary maintenance person is, of course, the furnace operator (the one who is using the unit). That person is generally blessed with four senses:

  • Sight – things can be seen and observed.
  • Smell – gas leakages (city gas, for example) can be smelled. Granted, nitrogen, argon, hydrogen, etc. cannot be smelled, but ammonia certainly can!
  • Hearing – the furnace associate can generally hear if a bearing is going bad or if a pump is beginning to fail.
  • Feel –  feel on the furnace cold face if there are hot spots developing (insulation failure).


It is a good practice that the furnace associate does a “walk about” around the furnace or equipment at the commencement of their shift, or a shift log book should be used with events noted  that require attention. This is to observe, listen and smell. A good tip for furnace maintenance is to follow the original furnace manufacturer's recommended maintenance procedure. The furnace may be used, however, and the previous owner (for whatever reason) may have lost the maintenance manual. The answer to this problem is relatively simple:

  • Place a telephone call to the original furnace manufacturer and ask for a new manual for the particular equipment.
  • Simply make and write your own furnace/oven maintenance manual.


Another common failing that has been observed by the writer on many occasions is internal furnace cleanliness. This is a particular problem with furnace systems that are processing forged components for austenitizing, which are reliant only on the products of combustion for surface protection. The scale that forms on the surface of the forged component will generally fall off and build up either on the furnace hearth, around the burner holes or both. The scale can build up to such an extent that it will begin to clog the areas around the burner holes.

The scale is building up simply because the burner air-to-gas ratio is not set correctly. One only needs to look inside the furnace and observe each of the burner flames to tell if complete or incomplete combustion is occurring.

Do not let the scale build up. Keep the furnace hearth clean and clear. Even if one is using an endothermic or other type of atmosphere, dirt can build up within the process chamber.

Good shop housekeeping and equipment maintenance is what will impress customers and keep equipment operational to pay the bills.