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How to Repair 4 Common Refractory Failures

Many companies rely on kilns, heaters, reactors and the refractory materials contained within. These materials have impressive life spans under typical usage, but they're still subjected to intense conditions and continual mechanical abuse. Even the most conscientious operators will find themselves in need of refractory lining repairs or replacement at some point.

What are the most common refractory failures, and what are the signs to watch for? Are there steps to take during the planning and construction phases that make problems less likely? Here's a crash course.

1. Fallen Roof Fibre Modules

Under typical conditions, it's not uncommon for refractory linings to last for 20 years or longer. However, the cost of an unexpected failure could be substantial — kiln or incinerator operators might face losses of $1 million per day of compromised production.

There are several reasons why a refractory lining might have its fibre lining modules fall or someone might notice gaps between them.

If all the fibre and metal anchoring materials are gone, the problem was likely caused by corrosion or improperly performed stud welds. If the fibre is missing but its anchoring materials are present, this more likely indicates mechanical wear and tear.

Actions to Take

Possible courses of action depend on a survey of the affected area. Improper installation, like excessive gaps between fibre modules, will cause multiple modules to fail rather than just one. People should act quickly in this case. Multiple failures require an inspection and reset of the fibre module layout design.

People should tackle corrosion by studying how the refractory was sealed. If the fibre modules show signs of water staining, it's time to reseal the refractory. Fibre modules are extremely porous and can absorb several times their weight in water.

2. Misshapen or Collapsed Lining Walls

The insulating fire bricks (IFBs) that comprise the walls of refractory linings haven't changed much in design in nearly 100 years. They're still one of the most widely used materials thanks to low thermal conductivity, but the IFBs of interior refractory walls are still subjected to intense wear and tear.

Sometimes the wall will be obviously cracked and deformed. In other cases, it may only be bowed slightly.

Actions to Take

The first step is to inspect the exterior of the refractory. Hotspots in this area could indicate the backup lining may have failed. In these cases, managers should choose a hotspot repair product and pump it into the unit from the outside.

If the wall is bowed but not otherwise obviously damaged, it probably means the refractory designer didn't leave room for proper thermal expansion. It may also be because of incorrect maintenance procedures. If somebody mistakenly filled "healthy" cracks in refractory blocks — the kind that appears during cooldown and disappears again during heating — then the refractory won't be able to expand as it needs to.

People should examine the surface of the bricks near the observed damage. If they show signs of cracking or melting, the fuel is impure or the unit is operating at higher temperatures than it was designed to withstand. In the latter case, a new refractory built from higher-quality materials may be needed. If that's not an option, the fabrication process should be changed to avoid total failure.

3. Cracks in the Floor

Cracks or heaving in the floor is another common cause of refractory failure and downtime. There are two main reasons why the floor might exhibit these signs:

  • The operational temperature of the refractory increased at some point since it was brought online, possibly because the product lineup or processes changed.
  • The refractory’s thermal expansion is compromised. It's common for expansion joints to become clogged with debris, which limits their effectiveness and can cause the floor to crack or heave.

Actions to Take

Several actions can be taken to halt this kind of damage and prevent it from worsening. The first is to add a routine step to the list of tasks to perform during refractory downtime. Someone should vacuum each expansion joint to keep them working as intended.

Solving this problem for good may require revisiting the flooring materials and design. It might be necessary to replace any dissimilar items placed adjacent to one another. It's also possible the refractory lining wasn't designed with sufficient expansion joints. In such cases, it's best to contact the original designer for inspection and further guidance.

4. Cracked Castable

A damaged castable is one of the most common refractory failure types because these components are typically fabricated in one place and then transported to their final destination for installation. The castable may still have some minor cracks from this process that were never addressed. They're typically not a cause for concern if they don't penetrate the material fully.

However, cracks going through the entire thickness of the castable are not normal handling or shrinkage cracks and require attention.

Actions to Take

Damage to the castable should be repaired right away. A professional can isolate and carefully remove the affected area without overly affecting its surroundings. Damage with fewer than three anchor points does not require immediate attention.

More significant damage may require a more complete retrofit. The original choice of materials and the design of the lining may not have been carried out with proper attention to relevant building codes for furnaces, fired heaters and kilns.

Preventing future damage to the castable may require operators to reduce the amount of contact between the surface of the castable and the outside air.

Evaluating and Addressing Common Refractory Failures

The world of manufacturing and material preparation is varied and constantly changing. Although humanity's collection of fabrication techniques over history has increased, some tools — like refractory designs and materials — haven't changed much over time. People whose livelihood depends on properly functioning incinerators, kilns or fired heaters should understand common refractory failures to assess visible damage and choose their next actions appropriately.

Emily Newton is the Editor-in-Chief of Revolutionized Magazine. She has over six years experience writing articles for the tech and industrial sectors. Subscribe to the Revolutionized newsletter for more content from Emily at https://revolutionized.com/subscribe/
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