Five Tips for Achieving Furnace-Lining Efficiency
Follow the five tips below to keep your furnace lining running efficiently.
Tip 1 – Evaluate the furnace lining by using infrared (IR) thermography inspection.
Infrared (IR) thermography scans are an essential step for evaluating the quality of the furnace lining. Lining quality is critical to protecting the steel from heat and also to limiting heat loss and promoting overall furnace efficiency. Typically, the scan involves pointing an IR camera at several spots 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 particularly true with a painted surface.
Obviously, scanning from the outside is of great benefit because the unit can continue to operate. Figure 1 shows an IR camera detecting hot spots or other problems with the lining. 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 on the 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 on-line repair option because it is reliable, fast and economical. After all, furnaces and boilers are generating revenue, so it is of great value if repairs can be made while the unit is online. This avoids revenue loss from the unit in question as well as the consequential losses from shutting down additional connected units.
For example, where IR scans indicate that on-line repairs are recommended, Morgan Thermal Ceramics’ pumpable Superwool® or Kaowool® can be pumped from the outside of the furnace or boiler, filling cracks and voids caused by deteriorated insulation. These products are ideal for providing improved thermal-insulation efficiencies behind boiler tubes in sidewalls, seals and floors as well as repairs of 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, pumpables or monolithics. Figure 2 shows how the repair materials can be pumped in from the outside to fill the hot spot and cool a particular area.
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 a furnace reline. Material selection is key 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 on the furnace’s application. Selection of the proper material is frequently done by using a heat-flow analysis software program in which temperature and use factors are input to obtain information on the best materials to be used.
Keep in mind that many units have old-style insulation. Since there are so many new, more-efficient insulation types now on the market, consider upgrading when you have to reline the furnace. For example, Morgan Thermal Ceramics’ Superwool Plus™ fiber has up to 20% lower thermal conductivity than competitive insulations. As a result, Superwool Plus fiber is 17% more energy efficient than traditional Refractory Ceramic Fiber (RCF) and any other Alkaline Earth Silicate (AES) insulations. A breakthrough in the company’s advanced manufacturing control has allowed the product to be engineered to maximize the fiber content. Its low bio-persistence also makes it a good replacement for those looking to move away from RCF insulation. Figures 3 and 4 show a variety of materials used in furnace rebuilds.
Tip 4 – Carefully consider engineering design.
After selecting the proper materials, be sure that the engineering design is suitable. Engineering is extremely important to ensuring 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 end up pushing 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 those 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 as bad as not having a good design and not making a good material choice. IH
For more information: Contact Steve Chernack, manager applications engineering, Morgan Thermal Ceramics, P.O. Box 923, Augusta, GA 30903; tel: 706-796-4301; e-mail: firstname.lastname@example.org; web: www.morganthermalceramics.com