Refractories are a vital component in boilers and furnaces, as they serve as a protective lining against the destructive processes of heat, abrasion, and corrosion inside your boiler’s combustion chamber.
Installing the right boiler refractory materials in industrial and commercial boilers plays a critical role in the efficient and safe operation of your system. Read on to learn more about how refractory lining works and how to replace it.
Refractory and Boiler Failure
Considering that refractory failure is one of the leading causes of boiler problems and fuel inefficiencies, it’s important to make sure that refractories used in boilers are in good condition. Due to the harsh environment that refractory materials operate in, it’s common for the refractory lining to wear down over time. In most cases, the refractory material will crack, erode, or get damaged if not monitored regularly.
What Causes Refractory Lining Wear?
Routine inspections, repairs, and scheduled maintenance and replacement of boiler refractory materials are critical. These steps reduce erosion on boiler tubes, ash coolers, burners, and other boiler system components. If refractory problems are identified, professional repairs and replacement will be needed.
Before getting into the details of the replacement procedure, it’s important to understand what causes refractory lining wear in commercial and industrial boilers. Here’s a small list of common causes:
Abrasive products and materials in boiler systems like fuel, ash, and other particles often wear away boiler refractory lining over time, just like sandblasting.
Refractory linings undergo constant heating and cooling processes that cause expansion and contraction. This thermal cycling eventually causes wearing down and weakening of the boiler refractory materials used. If there is a rapid change in temperature, known as thermal shock, your refractory lining may experience immediate damage.
The refractory lining can chemically react with boiler materials and byproducts of the process, potentially causing softening or glassing of the refractory material.
The washing action of moving liquids, like slag or molten metal, can erode refractory linings and further exposes the refractory materials installed to destruction by abrasive and corrosive elements.
Any moving equipment or parts in your boiler within a process can cause wear on the refractory lining, causing structural integrity issues on the refractory lining.
Finding the Cause of Boiler Refractory Failure
Discovering why a specific refractory material fails is a complex process. Failure is not usually a result of one factor alone, but a combination of several factors, including:
- Refractory material that doesn’t match the fuel being burned.
- Refractory material that was improperly installed, stored, cured, mixed, or dried.
- Refractory material that doesn’t match the existing boiler environment.
- Refractory material that doesn’t match the environment created by fuel combustion.
Once a clear evaluation of these factors has been completed, it’s time to gather more information before replacing your boiler refractory materials.
The Discovery Process
Consulting the boiler plant and installation personnel to collect and document basic information is the first step towards discovering the source of the refractory problem. These experts have first-hand details about the refractory process before and after problems were identified. The following details should be documented:
- Data sheets and material samples of the existing boiler refractory or brick lining.
- Material samples of slag and ash that can be supplied by the plant maintenance personnel.
- Chemical analysis of the boiler fuel being burned.
- Location of storage and duration of the boiler refractory materials before installation.
- Manufacturer name and date of refractory material manufacture.
- Condition of the refractory material during installation.
- Amount of refractory material that was installed.
- The installation procedure and application processes that were used.
- Procedures that were used during the drying or curing process.
Examination and Testing of Existing Material
Expert examination of collected material samples and existing refractory material helps identify the causes of refractory failure. When analyzing and looking at your existing refractory lining or photos, there are several possibilities to consider.
- Is there any evidence of thermal shock where large sections of the top refractory surface are sheared away?
- Did the refractory material fail due to exposure to excessive temperatures, showing glazing and excessive shrinkage?
- Could mechanical abuse be the cause of the problem resulting in jagged or broken holes or edges?
- Is the failure due to boiler or furnace equipment operation?
- Was the failure caused by improper refractory material installation?
It’s important that existing samples of refractory material undergo cold crush tests to verify their strength. The refractory manufacturer’s data sheet can be used to compare the results. If the results show low refractory strength, the right installation procedures may not have been followed.
For slag and ash clinker samples, chemical analysis tests are vital. These tests help determine the minimum temperature that the refractory material may have been exposed to.
Documenting the environment to which boiler refractory materials were exposed is an important part of the discover process. Calculating the base-to-acid ratio offers more details on the type of material that should have been installed in the first place. Refractory materials are manufactured to operate in different environments ranging from basic to neutral to acidic. Each condition has different types of materials that should be considered.
Reviewing Results and Boiler History
Once all tests are complete, it’s time to combine the results. Recent boiler service conditions should be reviewed and analyzed with the help of plant and installation experts. This process helps determine if the boiler service conditions could have affected the installed boiler refractory materials.
Some of the technical factors that could lead to refractory failure and replacement include:
- Moisture content in the fuel with a reducing atmosphere.
- Certain components in fuel, ash, or slag could react with cement-bonded refractory.
- Some startup fuels used in boilers contain components like vanadium, which cause chemical attacks and complete surface failure.
Review of Refractory Installation Procedure
If boiler refractory materials were not installed properly, the possibility of failure is high. Manufacturer recommended installation procedures have to be followed to ensure that refractory material is installed correctly for maximum strength.
The right storage, mixing, curing, and drying procedures must be followed when installing or applying refractory lining. Properly selected and installed refractory lasts longer, helps minimize boiler shutdowns, and leads to better fuel efficiency.
By understanding all aspects related to the design and installation of the boiler refractory materials, you can more easily understand the cause of failure and help prevent future problems.
Refractory Material Replacement
Due to the technical installation procedures involved, refractory replacement and maintenance should only be done by certified professionals with experience in the field.
When replacing boiler refractory materials, it’s important to think of the performance expected in a particular situation. The performance of refractory material you choose for replacement will depend on its qualities and quantities in different phases. The overall quality of the installation or replacement refractory materials is dependent on their physical, chemical, thermal, and mineralogical properties.
Industrial or commercial boilers use shaped or unshaped refractory materials. If any of them show signs of damage or degradation, repair and replacement should be considered.
Improving the Operational Life of Refractory Lining
The process for replacing your boiler refractory material begins with purchasing the appropriate amount and quality refractory material. Consulting experienced repair and maintenance experts will ensure that you choose the best refractory for your boiler system.
Technological advancements in the manufacturing processes of refractory materials have greatly improved over the last two decades. These have led to better performance of refractory material, easier application processes, and more efficient use. Remember that your choice of boiler replacement refractories depends on the operation and mechanical conditions of the boiler or furnace unit.
Dry-In Schedule After Refractory Lining Replacement
After installation, repair or replacement of boiler refractory materials, it’s important to follow the manufacturer’s recommended curing and dry-in schedule and procedures. Many clients or end users shorten the required time for proper boiler refractory dry-in due to the time and costs involved, but this comes with risks.
Risks of Improperly Cured Materials
Heating up your repaired refractories too quickly poses the greatest risk of failure. Following the recommended schedules will help avoid common issues like spalling from high-pressure steam as it builds up within the replaced refractory lining.
While in the past, dry-in schedules were generally about 72 hours, end users today only have to wait about 24 hours before they can activate the boiler. Although the curing time has been significantly reduced, it’s still important that your new refractory lining is allowed enough time to get to the right operational capacity.
Installation with an Expert Team
If your want to replace your refractory materials, contact our expert team at Manley’s Boiler, Inc. We have highly experienced supervisors who are qualified for the inspection and installation of boiler refractory materials that are specifically tailored for commercial and industrial boiler applications and processes. Our specialists can complete repairs and replacements as needed.
Get in touch with Manley’s Boiler Inc. to schedule an appointment today.