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Refractories are one of the most overlooked components of boiler systems. They’re heat resistant materials that make up the lining of boilers and other equipment—like furnaces. While they’re integral to running and maintaining commercial and industrial boilers, they are also a leading cause of boiler outages and energy losses. Proper boiler refractory installation, startup, and maintenance services are required so you get the most out of your boiler system and prevent issues.
Many clients don’t understand about installation and startup of refractories, and most end up choosing the wrong refractory material or even consulting refractory contractors with little knowledge of the latest application methods. Incomplete evaluation of boiler systems and partial explanations can easily lead to the wrong boiler refractory materials, incorrect installation methods, and higher running costs.
If you want to protect your boiler, read on to learn about the refractory construction and installation materials used today, how to choose the right installation method, advances in the refractory industry, and more.
Refractory materials are used in boilers to contain the heat generated by burning fuel in furnaces. These materials need to have the right insulating properties, withstand extreme pressure, and endure general wear and chemical processes, as well as withstand high temperatures.
Boiler refractory materials are classified in three main groups:
- Acid materials: They consist of clay, quartz, silica, gamister, and sandstone.
- Neutral material: Consist of graphite, chromite, alumina, and plumbago.
- Base or alkaline material: Consist of lime, zirconia, and magnesia.
Special care must always be taken when choosing the proper refractory materials to avoid unwanted reactions that could reduce insulation and effectiveness.
When it comes to installation, the refractory material used comes in two forms: firebricks and monolithic refractory.
This refractory material has long been used over the years. The material is formed into bricks that are fired at very high temperatures in special insulated chambers. The material is usually lined in boilers or furnaces.
These boiler refractory materials are unshaped and have become the most preferred option in the refractories industry over the last two decades. This is mainly due to economic considerations, their rapid installation time, lower cost of raw materials, and less manpower needed for refractory installation. Their main properties include abrasion resistant, chemical inertness, mechanical integrity, and thermal shock resistance at high temperatures. These materials come in many formulations and forms.
Monolithic boiler refractory materials come in many formulations and forms, including castable, plastic, ramming, gunning, and coating refractories.
These materials consist of fine refractory grains and precision graded coarse. They are usually mixed with water and installed by either pumping or pouring. Vibration is required for proper placement of the materials. Advances are being made in the manufacturing of castable formulations making the material easier and quicker to apply.
These are used as linings for various kinds of boilers. They are specially adapted for making economical and quick emergency repairs and can be rammed to any contour or shape. Plastic boiler refractory materials are extremely versatile, as they are highly adapted to different operational conditions.
These are very similar to plastic refractories, but are often stiffer. The material product is usually delivered dry and then mixed with little water before application. Other ramming refractories are delivered in wet form, ready for use immediately after opening the product.
These are granular materials that are sprayed on specific application areas, like furnace walls, using a variety of air placement guns. Gunning refractories are mainly used for patching and maintenance work on boilers and furnaces. They are mostly supplied dry and pre-damped in a batch mixer then fed into a gun continuously. They provide excellent coverage in boiler refractory applications.
Coating refractories are primarily used to protect refractory linings against any forms of chemical attack. They are applied to cover specific working surfaces of a refractory lining and are generally applied in thin layers.
There are other monolithic and specialized refractories used such as insulating castables, refractory mortars, fettling mixes, and tap hole mixes. To get a better understanding of these refractory materials and their applications, you should consult certified refractory experts.
There are several popular installation methods used for boiler refractory today. The most used methods include casting, pump casting, gunite, and shotcrete.
The casting method involves mixing and pouring wet castable refractory into forms. The forms are shaped to hold the refractory material in place until it’s set, after which it is removed.
Since most castable refractory is in fluid form, many application methods use the pumping technique. The refractory material is pumped into the particular location where it’s needed using a trailer or truck-mounted line pump. With this method, it’s easier to pump and apply large volumes of refractory material.
This is a dry monolithic refractory specifically designed for use with dry gun equipment. In most cases, additives are added to make it stickier and improve application time. Air is used to push out the dry gunite through a special machine hose to a specific target. Water, or other additive, is added at the nozzle to moisten the boiler refractory material used, so that it easily sticks to the application surface.
This is low-cement, low moisture refractory that’s fully mixed and tempered with water or additives. To apply shotcrete, most professionals use a dry spray gun.
How to Determine the Right Application Method
When it comes to installing refractory, you have to choose the most appropriate application method. However, you also have to consider some vital elements before application. Consider several factors that will influence your decision, including:
- Site conditions and location.
- Installation equipment and environmental factors.
- Volume of boiler refractory required.
- Storage conditions.
- Bake-out requirements.
- Cost of materials, equipment, and labor.
- Skill of refractories installation team.
As a client looking for the right installation services, discussing these factors with experienced and reputable boiler experts is critical. It ensures that you not only choose the right refractory materials, but that you also work with a reliable team that can recommend the best application method for the unique conditions of your project.
Advancements in Refractory Materials and Application
Over the last 20 years, boiler refractory has greatly benefited from significant improvements in application and material science. Some of the breakthrough technologies that have greatly improved the use of refractory in industrial and commercial boiler systems include abrasion resistant systems, chemical bonding advancements, and dry out time.
The area of abrasion resistance has greatly advanced in the refractory industry. Unlike several years ago, when the standard test method of abrasion resistance required losses less than 4.0 cc, today, it’s less than 3.0 cc. Technological advances in material science have ensured harder and more resilient refractory materials.
Chemical Bonding Properties
Manufacturers are now adhering new refractory material on existing material by chemical bonding. That has reduced the need for full boiler refractory replacement that can significantly affect repair and maintenance schedules, as well as budgets.
If a boiler system is missing the required percentage of refractory material, chemical bonding allows the overlaying of new refractory on top of the existing one to make up the desired lining thickness. So long as the manufacturer’s guidelines are followed for surface preparation and application, chemical bonding is a reliable refractory repair solution.
Dry Out Time
Dry-out time for refractory material has also improved. In some applications, manufacturers have created refractory material that requires little to no dry-out time and effort. Curing or dry-out time has been greatly reduced from 75-80 hours on average to 40-45 hours on average. A 50% reduction in dry-out time has ensured better cost savings for clients and less work and maintenance for installation experts.
Single Component Linings
In the past, different refractory formulas were used to perform certain application needs, like insulation and abrasion prevention, which would create two separate layers. In most cases, the separate layers would cause inefficiencies that would lead to boiler outages. Today, dual component linings have been replaced with single refractory formulas that serve all required functions effectively.
Anchoring systems for boiler refractory material have also come a long way. Hex metals that have long been used as anchors are now coming in different arrangements, such as center-tab hex arrangement, which is common today. These new systems handle greater refractory thickness.
There are also more advanced hex-alternative systems which are popular when performing localized patch repairs. Better and more effective anchoring systems, like hex-cell, half-cells, curl anchors, D-bars, and K-bars, have been introduced to the industry. Rapid arc welding for anchoring systems has also proved more superior and reduced failure rates.
Precautions During and After Refractory Installation
To ensure your installation goes smoothly, functions efficiently, and lasts for years, follow some simple precautionary advice from your friends at Manley’s Boiler, Inc.
- Provide ample space for expansion of boiler refractory. This will prevent undue pressure on the refractory material.
- The amount of refractory material used determines the time required to raise steam. A greater amount should be used to slow down the steam raising process and prevent refractory damage.
- Close down all air dampers or checks as soon as the boiler shuts down to prevent cold air from touching the hot refractory. This is one of the leading causes of surface flaking or refractory spalling, which causes reduction of the refractory wall thickness.
- Ensure that no impurities like sodium salts and vanadium enter the boiler to avoid any reaction with the refractory materials. Such reactions form a molten slag that causes a reduction of wall thickness.
Refractory Startup and Considerations
It’s important to understand that all boiler systems require expert operator attention during startup. Special care is needed when it comes to manipulating boiler fuel systems and feed water to ensure safety and prevent system damage. Boiler refractory startup plays a huge role in determining the achievable refractory life. A gradual warm-up is required to prevent refractory from cracking. To avoid problems and future costly repairs, depend on the experts.
Refractory Services and Maintenance
Proper installation of boiler refractory is critical to preserve industrial and commercial boiler equipment for the longest time possible. If you’re looking for installation, repair, or maintenance services, you have to work with established professionals to properly discuss your refractory needs. Whatever refractory problems you’re facing, the experts at Manley’s Boiler will work with you to determine the proper scope of work required.
At Manley’s Boiler, our technicians and welders are LACC, RSO, and MSHAW certified and trained to offer the highest standards of quality, safety, and technical expertise. Our professional experience, project management experience, and excellent workmanship result in quality services that you can count on. We handle everything from initial planning, operations startup, and performance evaluations to boiler selling and leasing, preventative maintenance, and large refractory equipment installation on your industrial or commercial furnace or boiler.
Our team is happy to offer the best solutions for your boiler refractory needs. To discuss our refractory services further, please contact us and we’ll arrange a consultation.