The selection of platen material in non-metallic expansion joints is usually based on its use environment and the performance requirements of the expansion joints. The platen functions in the non-metallic expansion joint to secure and support the skin (i.e., the non-metallic fabric layer), while also cooperating with the connecting flange to secure the expansion joint to the piping system by bolting.
The material of the pressure plate generally needs to have good mechanical strength, corrosion resistance and temperature resistance to adapt to various working conditions that the expansion joint may encounter. Common platen materials include:
Carbon steel: It is the most common platen material, suitable for non-corrosive environment and lower temperature working conditions. Carbon steel platens are typically finished, such as hot dip galvanizing or spraying, to enhance corrosion resistance.
Stainless steel: For corrosive medium or high temperature environment, stainless steel platen is a better choice. Commonly used stainless steel grades include the 304 and 316 series, and these materials offer excellent corrosion resistance and high temperature stability.
Alloy steel: In some special environments, such as high temperature, high pressure or the presence of specific corrosive media, it may be necessary to use special alloy steels, such as chromium molybdenum steel (CrMo), to meet more demanding use requirements.
Aluminum alloy: Aluminum alloy platens may be selected in situations where weight reduction is required, such as aviation or special industrial applications. Although it is not as strong as steel, it has an advantage in lightweight.
The specific material selection of the platen should take into account the working conditions of the expansion joint, including temperature, pressure, media characteristics, and possible corrosive environment. In addition, the size and thickness of the platen also need to be designed according to the size of the expansion joint and the required mechanical strength to ensure that the expansion energy saving works stably under the intended conditions. In some cases, in order to increase the sealing and abrasion resistance of the platen, its surface may be hardened or covered with an abrasion resistant coating.