In industrial environments where temperatures often soar above $1000^\circ\text{C}$, effective thermal management is non-negotiable for energy efficiency and operational safety. Among the high-performance materials available, calcium silicate insulation stands out as a white, rigid, and durable solution for continuous high-heat applications.
This guide provides a comprehensive overview of calcium silicate (Calsil) insulation, detailing its unique scientific structure, its critical applications across heavy industry, and the key factors to consider when choosing the right density for your thermal system.
Calcium Silicate Insulation is a lightweight, non-combustible material formed from a reaction between lime ($\text{CaO}$), silica ($\text{SiO}_2$), and reinforcing fibers, produced through a high-pressure hydrothermal curing process. It is the gold standard for backup and intermediate layer insulation in furnaces and pipelines operating up to $1100^\circ\text{C}$.
Unlike older materials, calcium silicate is 100% asbestos-free, offering a safe and reliable alternative for industrial thermal management.
The exceptional performance of Calsil is rooted in its unique crystalline structure, specifically the formation of Xonotlite ($6\text{CaO} \cdot 6\text{SiO}_2 \cdot \text{H}_2\text{O}$).
This structure features microscopic, interlocking needle-like crystals that create high internal porosity. This porous, yet rigid, network provides two major benefits:
Extremely Low Thermal Conductivity: The high volume of trapped air within the microstructure minimizes heat transfer.
High Compressive Strength: The interlocking crystals allow the material to bear significant loads without deforming, making it ideal for backup layers behind heavy refractory bricks.
Caption: The needle-like, porous Xonotlite structure is the reason for Calcium Silicate’s low thermal conductivity and high compressive strength.
Calcium silicate insulation is selected for industrial projects because of its robust technical specifications, which offer superior longevity and energy savings compared to conventional insulating materials.
| Property | Value/Range | Benefit |
| Max Service Temperature | $1000^\circ\text{C}$ to $1100^\circ\text{C}$ | Reliable performance for continuous use in super-high heat environments. |
| Low Thermal Conductivity | $0.06–0.09 \text{ W/m·K}$ at $200^\circ\text{C}$ | Maximizes energy efficiency and reduces fuel consumption. |
| High Compressive Strength | Up to $5.5 \text{ MPa}$ | Ideal for use as load-bearing backup insulation for heavy refractory linings. |
| Dimensional Stability | Very Low Shrinkage | Ensures the insulation maintains its shape over decades of thermal cycling. |
| Fire Safety | Non-Combustible | Used effectively in passive fire protection systems. |
| Material Type | Max Temp (C) | Thermal Conductivity (W/m⋅K) | Compressive Strength (MPa) |
| Calcium Silicate | $\sim 1100$ | $0.07$ (Excellent) | $0.8 – 5.5$ (High) |
| Mineral Wool/Rockwool | $\sim 750$ | $0.08 – 0.10$ | $0.005$ (Very Low) |
| Perlite Blocks | $\sim 870$ | $0.09 – 0.11$ | $0.5 – 1.5$ (Low/Medium) |
The versatility of Calsil boards and shapes makes them indispensable for both thermal process efficiency and safety across numerous sectors.
Calcium silicate serves a critical function as the backup insulation layer in steelmaking equipment. It protects the outer steel shell and provides a thermal gradient that prolongs the life of the primary refractory lining.
Uses: Blast Furnace Stoves, Hot Blast Pipes (Bustle Pipes), Reheating Furnaces, and Lime Kilns.
Key Benefit: Its high compressive strength withstands the pressure exerted by the heavy, dense working lining.
This is a high-value application where specialized High-Density Calcium Silicate is essential.
Non-Wettability: The material resists adhesion and corrosion from molten aluminium, significantly reducing metal loss and cleaning time in holding furnaces, launders, and spouts.
Uses: Holding Furnaces, Troughs (Launders), Transfer Spouts, and Hot-Top Ring Systems.
In power plants, Calsil is crucial for maximizing efficiency and minimizing heat loss in continuous operation.
Uses: Boiler Walls, Steam Turbines, Chimneys, Flue Gas Ducts, and Waste Heat Recovery Boilers.
Key Benefit: Wide temperature range and long-term dimensional stability ensures long-lasting thermal protection under high pressure.
Cement kilns operate under extreme thermal cycling and chemical conditions.
Uses: Preheater Cyclones, Kiln Riser Ducts, and Firing Hoods.
Key Benefit: Lightweight structure minimizes the load on the kiln shell and supporting ductwork, while its stability maintains process temperatures needed for clinker formation.
Consistency is key in glass and ceramics manufacturing.
Uses: Glass Melting Furnaces, Regenerators (Backup), Annealing Lehrs (Lehr rolls), and Tunnel Kilns.
Key Benefit: High dimensional stability prevents cracking and deformation, maintaining the thermal profile critical for product quality.
Calsil provides chemical and electrical insulation in highly complex environments.
Uses: Process Heaters, Reformers, Gas Crackers, and High-Temperature Pipelines.
Key Benefit: Non-combustibility and resistance to corrosion from fuel gases and chemical vapours ensures maximum safety and operational uptime.
Selecting the correct density is paramount for optimal performance. The choice depends mainly on the application’s mechanical and chemical requirements.
Operating Temperature: Typically up to $1000^\circ\text{C}$.
Density: $170–270 \text{ kg/m}^3$.
Reinforcement: Primarily glass fibers.
Best Use: General backup insulation in continuous furnaces, boilers, and large ducts where heat loss reduction is the main priority. Offers the best insulation value per thickness.
Operating Temperature: Up to $1100^\circ\text{C}$.
Density: $250–500 \text{ kg/m}^3$ (or higher).
Reinforcement: Often reinforced with Carbon fibers or specialized glass fibers.
Best Use: Applications requiring high load-bearing capacity (under heavy bricks) or direct contact with non-ferrous molten metals (like aluminium) where non-wettability is critical. Provides superior mechanical strength and thermal shock resistance.
Caption: High-density calcium silicate can be easily CNC machined for customized industrial components like pouring spouts and feeder tips.
Proper handling and installation are necessary to maximize the service life of calcium silicate insulation, often lasting up to 20 years.
Expansion Joints: Despite its low shrinkage, Calsil should be installed with expansion joints to accommodate the thermal expansion of the surrounding steel shell and the primary refractory lining. Consult manufacturer guidelines for spacing.
Sealing: Any gaps or joints should be sealed with high-temperature refractory cement or mastics to prevent “hot spots” caused by heat tunnelling.
Moisture Control: While stable, Calsil should be stored and installed dry. If it gets wet, a controlled dry-out schedule (slow, gradual heating) is necessary to prevent steam spalling upon initial heat-up.
While calcium silicate is non-asbestos, it is crucial to handle the fibrous dust correctly.
PPE: Always wear appropriate personal protective equipment, including N95 respiratory masks and safety glasses, when cutting, drilling, or machining the boards.
Ventilation: Use power tools with local exhaust ventilation or perform cutting in well-ventilated areas to minimize inhalation of fine silica dust.
Q1: How does calcium silicate compare to ceramic fiber?
Calcium silicate is a rigid board/block, offering high compressive strength and dimensional stability, making it suitable for load-bearing backup layers. Ceramic fiber is flexible, lighter, and easier to install, but cannot bear a load and is typically limited to lining hot-face applications or highly irregular shapes.
Q2: Can I use calcium silicate for fire protection?
Yes. Due to its non-combustibility and stability at high temperatures, it is widely used in passive fire protection (PFP) systems, including heat barriers, cable trays, and fire-rated partitioning, offering excellent insulation during a fire event.
Q3: Is calcium silicate insulation recyclable?
Yes, in many cases. Due to its inert mineral composition, spent Calsil can often be crushed and used as filler material in non-critical construction applications, reducing landfill waste.
Q4: Does the material emit odors or fumes?
No. Once installed and cured, pure calcium silicate is odorless, non-toxic, and does not off-gas, making it safe for food processing and clean industrial environments.
Calcium silicate insulation remains the material of choice for engineers who require a solution that perfectly balances high temperature resistance, structural strength, and outstanding energy efficiency.
By reducing heat loss, maintaining stable process temperatures, and extending the life of primary refractory linings, Calsil boards contribute directly to the profitability and safety of operations across the steel, aluminium, power, and cement industries.
Ready to invest in insulation that lasts as long as your equipment? [Zhengzhou Highland Refractory Material Co., Ltd.] offers customized calcium silicate solutions, engineered for perfect fit and maximum thermal performance. Contact us today to discuss your next high-temperature project.
Calcium Silicate Insulation Board is a high-performance, lightweight thermal insulation material designed to provide exceptional fire resistance and superior thermal insulation in high-temperature industrial applications. This non-asbestos product, primarily made from a blend of silica (SiO₂) and calcium (CaO) along with reinforcing fibers, is widely used across multiple industries for its remarkable heat-resistant properties. It is ideal for applications that require continuous exposure to temperatures as high as 1000ºC. This product offers not only excellent insulation but also superior mechanical strength and durability, making it suitable for a wide range of applications, including steel furnaces, chemical processing units, boilers, kilns, and energy systems. Available in various thicknesses and dimensions, calcium silicate insulation boards provide an efficient solution for meeting the challenging demands of high-temperature environments.
Ceramic fiber board is a new type of refractory insulation material.
Ceramic fiber products are advanced high-temperature insulation materials designed for industrial furnaces, kilns, boilers, and thermal processing equipment. With superior heat resistance, low thermal conductivity, and flexible forms, these materials help industries improve furnace efficiency, reduce operating costs, and extend equipment service life. Highland Refractory, a leading manufacturer of refractory materials, offers a complete range of ceramic fiber products engineered for demanding industrial environments. Our products are trusted worldwide in steel, non-ferrous metallurgy, petrochemical, cement, glass, and energy industries, providing reliable thermal insulation solutions with continuous service temperatures ranging from 1260°C to 1600°C.
Ceramic Fiber Tape, woven with high-purity ceramic fiber yarn, is a versatile and efficient thermal insulation material used across various industries. With a high temperature resistance range from 600°C to 1050°C, ceramic fiber tape is primarily designed for use as insulation gaskets, covers, and seals for high-temperature systems. The material’s outstanding combination of low thermal conductivity, great flexibility, and resistance to thermal shock makes it indispensable in applications requiring robust thermal insulation. Manufactured by Highland Refractory, our ceramic fiber tape meets the highest quality standards, providing optimal performance in even the harshest environments. Whether it’s used in industrial furnaces, power plants, or high-temperature sealing applications, our ceramic fiber tapes are designed to meet the demands of modern industries, offering safe, energy-efficient, and long-lasting solutions.
Ceramic fiber board is a new type of refractory insulation material.
