refractory in a boiler

The Importance of Refractory in a Boiler

Boilers are impressive devices designed to withstand intense heat and pressure with minimal maintenance. But, over time, they will require more and more fuel to give the same performance. Did you know that the number one reason for this is the erosion of the refractory material?

As the refractory material inside your boiler slowly wears away, heat is allowed to escape instead of staying trapped in your boiler water. Let’s take a look at this wonderful material and why it’s so important to your boiler.

What Is Boiler Refractory?

“Refractory” describes the material that lines a commercial boiler, high-temperature furnace, or other similar units. This material is heat-resistant in order to withstand the high temperatures it is exposed to in these units. It also needs to be able to withstand wear due to the chemicals it is exposed to and yet still function. The materials used to create this refractory lining can also be used to fill in any of the boiler’s openings, line the boiler’s parts, and protect the wall tubes.

Boiler Refractory Materials

There is considerable variablilty in the materials chosen for the refractory in a boiler. Though many look like little more than ordinary ceramic brick, some linings can be composed of complex materials like gunning mixes, plastic, or castable mixtures.

Most boiler refractory materials come from a variety of mostly nonmetallic substances such as Fireclay (mostly hydrated aluminum silicates), silicon carbide, alumina, magnesite, zirconia, chromite, dolomite, or bauxite. These materials contain the high strength, chemical resistance, and, most importantly, heat-insulating properties necessary to serve in a boiler.

Important for Efficiency

The most common reason that boilers drop in efficiency is the decay of this refractory material. Once the refractory material begins to fail, heat from combustion can escape. This loss of efficiency will grow more severe as more and more refractory material is lost, but it can be restored by replacing the refractory material.

Your boiler’s refractory is necessary for helping to keep the heat inside your boiler. Therefore, if it gets damaged, your boiler won’t be as efficient, causing you to spend more money on fuel.

Causes of Refractory Material Failure

Refractory damage can cause severe problems with your boiler. In fact, if the damage is bad enough, you may need to shut down your boiler while it’s being repaired. You may even need to replace it. There are several problems that may cause your refractory to become damaged or fail, but with proper precautions, you may be able to avoid these issues. We list some of these problems below.

  1. Improper Material Selection. If the refractory is made of materials that are not adequately heat-resistant, it could fail in less than a year.
  2. Poor Installation. A refractory should last at least seven years; they often last considerably longer. However, if the refractory is not installed correctly, holes and cracks may form, thus shortening its lifespan.
  3. Incorrect Storage or Mixing. Not only is it important to choose the correct materials for your refractory, but they also need to be correctly stored as well. It’s essential to keep the materials dry, or they may not cure as quickly or last as long. Proper mixing is also vital, as improper mixing could lead to holes or sheering of the refractory lining.

Maintaining Your Refractory Material

Maintaining your refractory is essential for protecting the structure of your boiler and ensuring its energy efficiency. To properly maintain your refractory, it must be regularly inspected. During the inspection, the technician will collect information about the materials that make up your refractory along with a sample to analyze.

Fuel samples will be taken as well to see what chemicals are in the fuel and whether they might react with your refractory to potentially cause holes, cracks, or sheering. The refractory will also be visually inspected to see if it’s in satisfactory condition. If any problems are discovered during this inspection, you’ll be able to deal with them before they become more serious.

You can also take some steps yourself to increase the life of your refractory. Take care to follow the manufacturer’s instructions during boiler heat up and cool down. Also, don’t let dust accumulate on your boiler’s stainless-steel surfaces as it could cause it to overheating and fatigue.

Finally, pay attention to cracks in the refractory material. During the heat-up process, this is normal, but if they are present at other times, they need to be addressed quickly.


Hopefully, now you understand how important your refractory material is to your boiler. If your boiler has lost efficiency and is consuming more fuel or if surrounding parts are suffering heat damage, chances are your refractory material is damaged. By checking for loss of refractory material as a part of your maintenance routine, you can prevent this loss of efficiency and easily restore it by replacing the lost material. This is important not only to save money on boiler operation but also to minimize damage to the boiler itself.

When it comes to boiler compliance and boiler maintenance, it is crucial to work with a heating contractor that understands the entire heating system.  CC Controlled Combustion Co. Inc. specializes in all areas of your hydronic heating system and steam heating system.  Our range of services falls into five categories.  1) Compliance, 2) Maintenance, 3) Service, 4) Replacements & 5) Upgrades. Our 1) Compliance (aka Boiler Compliance or NYC Boiler Code Compliance) includes, but is not limited to NYC DOB Code Compliance (Annual Boiler Inspections LL4, LL87, LL95, LL97, Gas Pipe Inspections LL152), NYC DEP Certificate Renewals for Triennial Inspections, NYC DEP Registration Renewals, NYC DEP Annual Tune-Ups, NYC DEP Annual Backflow Preventer Inspections, NYS DEC Fuel Oil Tank Inspections (Monthly Visual Inspections for Above Ground Petroleum Bulk Storage Tanks and Annual Tank Tightness Testing for Underground Petroleum Bulk Storage Tanks).  NYS DEC Petroleum Bulk Storage (PBS) Application filing.  We also work with customers to cure the various DOB Boiler Violations, DEP Boiler Violations & DEC Violations. Our 2) Maintenance (aka heating system maintenance or preventative boiler maintenance) includes Burner Overhauls, Boiler Cleanings (Fireside Boiler Cleanings & Waterside Boiler Cleanings) on Cast Iron Sectional Boilers, Condensing Boilers, Firebox Boilers, Scotch Marine Boilers (both Firetube Boilers & Watertube Boilers), Boiler Water Chemical Treatment, Low Water Cut Off Control Maintenance, Condensate Neutralizer Kit Replacements, Domestic Hot Water Coil Flushing, Heat Exchanger Flushing & Valve Exercising.  Our 3) Service is available 24/7/365.  We offer trustworthy 24/7/365 Emergency Boiler Service.  We responded to service calls from our Service Contract customers during Super Storm Sandy, COVID19 Pandemic, on all holidays and in any weather.  Our Certified Welders, Electricians & Plumbers allow us to resolve a wide array of service requests during normal business hours. Through our 4) Replacements (aka Boiler Replacements or Boiler Installations), we perform like for like boiler replacement, bid on a spec from a professional engineer or suggest a different size or type of boiler.  We offer gas conversion services with utilities like Con Edison and National Grid, and chimney liner installations.  5) We can upgrade parts of your existing boiler or heating system for better efficiency, reliability, and compliance.  Some of our common upgrades are fuel conversions (#4 oil to #2 oil and or natural gas), linkage-less control (aka parallel positioning), variable frequency drive (VFD) installations on motors, and energy management systems with apartment temperature sensors.  We are an approved vendor for Consolidated Edison Rebates (Con Ed Rebates), National Grid Rebates (Nat Grid Rebates) and New York State Energy Research and Development Authority Real-Time Energy Monitoring (NYSERDA Rebates or NYSERDA RTEM Rebates).

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