Refractory is an insulating material suitable for temperatures as high as 3000 degrees Fahrenheit. This material is often used as a lining in furnaces, kilns, incinerators, boilers, smelters, and even rocket engines. It is made of natural and synthetic compounds, including ceramics, clay polymers and some super alloys. With routine inspection and proper maintenance, refractory can provide years of safe, reliable and efficient operation while minimizing the cost of equipment failure and downtime.
The insulating properties of refractory make the impossible jobs possible. Think of a smelting pot that holds molten steel – the pot is typically made of steel. Without refractory, the pot would be damaged every time the super-heated liquid was poured into it because the temperature of the liquid was higher than the melting point of the pot. However, a pot lined with refractory can be used over and over
again with no damage to the vessel.
For safe operation, burners, boilers, furnaces and other equipment depend on quality refractory. A burner creates an extremely hot flame and refractory protects the equipment while shaping and directing the flame. Boilers and furnaces rely on refractory to avoid unsafe hot spots or potential failure from burning through the equipment. Downtime, injuries and fires may be avoided with routine refractory maintenance.
Refractory can improve the efficiency of your operation. For instance, a boiler lined with refractory takes less time – and therefore fuel – to heat the water or steam each time it cycles on. The heat loss from the boiler is minimized because the refractory holds the heat where it belongs, inside the boiler. It also means burner cycle times can be longer or high-turndown burners can run at a lower flame, further enhancing efficiency and reducing operating cost. As an added bonus, less cycling means components such as the burner and housing will last longer and reduce capital cost. Refractory inspection and repair needs to be routinely performed by a trained technician to avoid downtime, emergency repair cost or total equipment replacement. Some issues a technician will look for are surface cracks, thinning refractory, tile sag, and slag. While the target wall area often shows the first signs of failure, the technician will investigate the entire refractory as part of a quality inspection.
Surface cracks are the first indication of refractory deterioration. If a burner is excessively cycling, possibly due to over-sizing, inadequate turndown or spikes in demand, premature cracking may occur near the burner. If cracks are allowed to spread, they can create hot spots in the casing, which may weaken it and cause a safety hazard and/or equipment failure.
Thinning refractory is also on the technician’s mind because as it thins, the insulating quality is reduced and end of life is approaching. One indicator of thin refractory is crater-like depressions, known as spalls. Spalls occur when an improperly shaped flame impinges the surface of the refractory. Correcting the burner and essential refractory could prevent major damage to the equipment and extend its life.
As refractory material expands and contracts, the refractory tiles can shrink, warp and sag over time. Any gaps between tiles can allow heat to penetrate, causing damage to the casing or surrounding area. Warping and shrinking is a precursor to replacing the entire chamber. Early detection provides the opportunity for budgets and operations to be planned accordingly. Slag is material deposited on the refractory’s surface and may cause a variety of issues. For example, slag may reduce heat absorption, raise exit gas temperatures, increase attemperator spray-flow temperature, interfere with ash removal, or impact equipment operation. Minor slag may be removed from the refractory, improving performance.
The life span of refractory varies from application to application. With routine inspection and maintenance, problems can be found early and a patch of high- temperature mortar can extend its longevity. While it is important to note that this fix may only last a few years and eventually the refractory will have to be replaced, it’s less expensive to repair cracks than it is to deal with damaged equipment, downtime, or injured personnel. American Combustion Service, Inc. is prepared to handle all your refractory needs with highly trained technicians. We will work with you to develop a routine inspection schedule to protect your equipment and employees. A variety of pre-cast refractory shapes are kept on hand and we custom mold shapes as needed to handle routine or emergency calls. 24-hour customer service is one of our highest priorities and we understand coordinating with your team is essential to minimize downtime.