The thickness of high temperature expansion joint castables mainly depends on several factors, including the operating temperature, the material of the expansion joint, the expected service life, and the specific application conditions. Here are some specific examples and guidelines:
In some applications, the inner sleeve of the high temperature expansion joint may use Q235 steel with a thickness of 8mm, on which 50mm of high strength refractory concrete is poured to provide protection.
For cyclone returner in CFB boiler (circulating fluidized bed boiler), the design thickness of refractory castable can reach 360mm, where the first layer is 115mm thick high-strength wear-resistant castable, and the second layer is 254mm thick lightweight thermal insulation castable.
The reasonable thickness of castable needs to consider the service environment and service cycle, which is usually set by the design institute according to specific working conditions. For example, if the expansion joint is in an extremely high temperature environment, the thickness of the castable will be increased accordingly to provide better insulation and protection.
Different types of refractory castables have different expansion joint reserved widths, such as:
Clay refractory castable: 4~6mm
High aluminum cement refractory castable: 6~8mm
Phosphate type refractory castable: 6~8mm
Water glass refractory castable: 4~6mm
These thicknesses and reserved gaps are general guidelines when there are no specific design requirements. In practical applications, reference should be made to the equipment manufacturer's recommendations and engineering design standards to determine the castable thickness that is best suited to specific operating conditions. If the expansion joint is operating at very high temperatures, e.g. over 900°C, then special materials such as stainless steel 310S, stainless steel 309S, titanium alloys or nickel-based alloys may be used, and the castable thickness will be adjusted according to the thermal expansion characteristics and temperature resistance of these materials.