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Achieving Furnace Lining Efficiency

Feb. 24, 2012
Five tips for an efficient furnace lining, to cut maintenance costs and keep operations running smoothly and cost-effectively.
An IR camera detects hot spots or other problems with the furnace lining.
Furnace lining repair material can be pumped in from the outside to fill a hot spot and cool a particular area.

An efficient furnace lining is essential for reducing overall maintenance costs and ensuring that facilities run smoothly, without unwarranted revenue loss due to downtime. Follow these tips to keep your furnace running efficiently.

Tip 1. Evaluate the furnace liner with IR thermography inspection — Infrared (IR) thermography scans are essential for evaluating the quality of the furnace lining. Lining quality is critical to protect the steel from excess heat and limit heat loss, and to promote overall furnace efficiency. Typically, the scan involves pointing an IR camera at several points on the furnace casing to analyze the outside temperature and identify hot spots where the unit is leaking heat or experiencing design issues that may not be visible from the outside. This is a particular issue with a painted surface.

Obviously, scanning from the outside is of great benefit because the furnace unit can continue to operate. In many cases, specially trained applications engineers conduct the infrared imaging, analyze the IR scans, and provide recommendations on the most appropriate repair options.

Tip 2. Use on-line maintenance repair — Depending upon the furnace’s temperature, the difficulty of getting to a particular area, or how big the hot spot is, conduct on-line repairs wherever possible. Most maintenance managers prefer the online repair option because it is reliable, fast, and economical. After all, if the unit is producing and generating revenue, repairing it while it is online will avoid revenue loss, including the losses from having to shut down other connected units.

For example, where IR scans indicate that on-line repairs are recommended, Morgan Thermal Ceramics’ pumpable Superwool or Kaowool insulation can be pumped from outside of the furnace, filling cracks and voids caused by deteriorated insulation. Products like these are effective for providing improved thermal insulation efficiencies behind boiler tubes in sidewalls, seals and floors, as well as to repair ovens, furnaces and process equipment. With traditional repairs, the furnace must be shut down and cooled until it is safe for maintenance personnel to enter and repair the lining with fiber blankets, pumpable or monolithic refractories.

Tip 3. Choose the right material for furnace rebuilds — When IR scans indicate that the area of concern is too large for on-line repairs, the unit must be shut down for furnace relining or process heater relining. Material selection is critical to a successful furnace rebuild that will improve efficiency and reliability, and lower maintenance costs. Material properties, including hardness, density, mechanical resistance, or insulating factor, may vary depending upon the furnace’s application. To select the appropriate material for your installation, use a heat-flow analysis software program into which specific temperature and use factors can be applied to obtain information on the appropriate product application.

Keep in mind that many units have old style insulation; since there are so many new, and more efficient insulation types commercially available now, consider upgrading your material choice when reline the furnace. Morgan Thermal Ceramics’ Superwool Plus fiber has up to 20% lower thermal conductivity than competitive insulations, for example, and as a result it is rated 17% more energy efficient than traditional refractory ceramic fiber (RCF) and any other alkaline earth silicate (AES) insulations. MTC’s advanced manufacturing control allows the product to be engineered to maximize the fiber content. Its low bio-persistence also makes it a good replacement for those plants seeking to move away from RCF insulation.

Tip 4. Carefully consider engineering design — After selecting the proper materials, be sure that the engineering design is suitable. Engineering is particularly important to ensure that the furnace relining is as long lasting as possible. Make sure the materials have enough studs to hold them in place, and have sufficient joints for expansion or shrinkage. For instance, if you install a brick lining without the proper expansion joints, the brick could actually grow and begin to push the entire lining off the furnace wall.

Tip 5. proper installation is key to success — Be sure that installation of furnace lining material is done properly and the workers doing the job have the proper skills for the task. There are a wide variety of products available and each one has different installation requirements. For example, with concrete products, if the concrete is not mixed with the right amount of water at the proper temperature, the material will not develop, will be difficult to place, and will not reach expected properties. The bottom line is that if you don’t install it right, it is just as bad as not having a good design and not making a good choice of material.

Steve Chernack is the manager of applications engineering for Morgan Thermal Ceramics’ manager of applications engineering. Learn more at