What material is now commonly used to construct furnace walls in modern watertube boilers?

The construction of furnace walls in modern watertube boilers commonly utilizes watertubes themselves. This approach optimizes heat transfer and increases the structural integrity of the boiler. Watertubes are designed to carry water and steam efficiently, allowing for high-pressure operation and effective heat exchange. By integrating watertubes into the furnace walls, manufacturers can achieve better temperature control and enhanced energy efficiency.

Other materials, such as steel casing, might be used in different boiler components, but they do not provide the same level of heat exchange performance as watertubes. Plastic insulation and block insulation may serve important functions in thermal insulation but are not part of the structural design that contributes to the boiler's primary operation and efficiency. Thus, the design choice of using watertubes aligns well with the operational efficiencies and performance requirements of modern watertube boilers.