Circulating Fluidized Bed (CFB) Boiler Tube Erosion

HVTS Claddings for CFB Boiler Tubes

IGS leverages decades of experience with over 500 Circulating Fluidized Bed (CFB) Boiler High Velocity Thermal Sprayed (HVTS) cladding applications to stay at the forefront of maximizing run time and minimizing outage frequency and cost for CFB Boilers globally.  IGS HVTS cladding has been successfully used over the past decade to provide scalable (we adjust cladding thickness to meet specific wear rates in different locations), proactively manageable and fully refurbishable boiler tube protection from fly ash erosion and fireside corrosion. Our service renders mechanical repair of boiler tubes in Circulating Fluidized Bed Boilers an unnecessary practice.

The problem: an example of CFB Boiler erosion



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Colin Bateman

IGS Subject Matter Expert

Waterwall Corrosion-Erosion of Circulating Fluidized Bed Boilers

CFB Boilers by design offer a number of advantages over conventional boiler designs, including the ability to fire a wide range of fuels and lower combustion temperatures which reduce emissions.  The bottom approximately one-third of these boilers is generally protected by castable refractory, but the top approximately two-thirds have exposed tubes to maximize radiant and convective heat transfer.  These boilers operate by combusting fuel in a fluidized bed of non-combustible particles which causes CFB erosion.

As bed material particles recirculate in the furnace, it causes metal wastage of the furnace water wall / evaporator panels by corrosion-erosion mechanisms, an unavoidable consequence of this design of boiler.  This fireside corrosion is typically found at refractory to water wall / evaporator interface, field weld joints in the furnace (typically 4-8 meters above the refractory interface), and at tubes upstream of the cyclone inlet(s) at the top of the furnace as fly ash travels out of the furnace and into the cyclone.

On-Site HVTS Cladding Mitigating CFB Metal Wastage

IGS High Velocity Thermal Sprayed cladding is ideal for protecting CFB boiler tubes from fireside corrosion and fly ash erosion metal wastage.  For CFB Boilers, IGS applies high alloy materials with both ceramic and metallic components to produce a homogenous (particles typically <50um), hard (typically in excess of 1,200Hv300), and tough layer providing optimal application and performance properties for CFB Boilers. We utilize only the true High Velocity application process, where atomization of the material occurs before or in a supersonic gas stream, the only way in which to achieve such optimal cladding properties needed for reliable and predictable long-term cladding performance.

Advantages of IGS HVTS Cladding

IGS HVTS offer our customers the following advantages over other thermal spray and cladding solutions:

  • We proactively manage IGS HVTS cladding to eliminate boiler tube wastage. With IGS technology, the HVTS cladding becomes a controlled protective sacrificial barrier that eliminates CFB erosion tube wastage and therefore the need for tube restoration in CFB furnaces indefinitely.
  • HVTS cladding is completely scalable, which creates the opportunity for customers to extend their run time between outages with the assurance that they will not suffer a tube leak, and maximize the return on investment of their operating assets.

SMART Gard - The Smarter Way to Guarantee CFB Boiler Reliability

Find out more about SMART Gard solution characteristics, alloy features, technological benefits, erosion resistance, and much more.

Our Experience Cladding Metal Inside CFB Boilers

IGS is the pioneer in the use of Thermal Spray claddings in CFB boilers. We have completed over 500 CFB applications over the past two decades.  Having completed so many applications over so many years uniquely positions IGS as the knowledge leader in materials, application technology, installation, refurbishment and operating methods.  Simply stated, we are the best positioned to know what works and what does not in many varying CFB Boiler types burning a wide range of fuels across the globe.  Where others may be experimenting, IGS has trusted and proven solutions.

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Optimized Solutions for CFB Boiler Tube Wastage Protection

Over the past decade, we have leveraged this experience and knowledge to develop unique materials and methods to provide reliable and predictable protective barriers in the most challenging CFB boilers globally.  We have learned that:

  • For the use of thermal spray coatings to make sense economically, they must be managed proactively so as not to expose underlying substrate material. Investing in thermal sprayed coatings and having to expend time and money on tube restoration is not optimal.  IGS has proven success in accomplishing this.
  • Materials need to have specific properties to successfully protect boiler tubes reliably over multiple outage cycles, and for the life of the boiler. Hardness, toughness and residual stress properties are among some of the critical characteristics that determine whether coatings will wear in a controlled manner, and not cause secondary problems in the furnace such as accelerated wastage of the tubes at the coating interface, or accelerated localized wear should the coating failure in localized areas.

IGS Cladding Prevents Accelerated Localized Wear of CFB Waterwalls

  • Managing long-term boiler tube protection is a larger challenge than just the initial application. Unlike many environments where protective claddings or coatings are used, in CFB boilers, the boiler tube protection system such as IGS HVTS cladding is a sacrificial layer.  This means it must be proactively refurbishable to be effective.  IGS creates value for its clients not only through the provision of skilled personnel and proprietary fit for service HVTS cladding solutions but also through expert inspection and wastage modeling. We specify what materials, at what thickness should be applied where both on initial application and periodic refurbishment. These specifications ensure long-term dependable performance.


Good communication. Job hazard analysis was well documented and the thermal spray method statement was clear and comprehensive. IGS was on time and provided daily job progress reports.

Plant Engineer

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We Provide On-Site Expertise and CFB Boiler Service Worldwide

HVTS cladding offering creates value for CFB boiler owners and operators by ensuring reliability and predictability of the performance of their boiler assets. Customers who view the reliability and dependability of their units as mission-critical to their revenue generation and/or their customers will experience the economic benefit of IGS technology and approach to CFB Boiler reliability.  Through our strategically placed operations in the Americas, Europe, Africa, CIS, Middle-East, and Asia Pacific regions, we focus on creating value for our customers globally by ensuring the reliable and dependable performance of their mission-critical assets.

Read more on our Biomass and Waste-to-Energy BFB and CFB boiler erosion-corrosion solutions.

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