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
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
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.