What Does Chime Mean?
A chime, as it pertains to bulk storage tanks, is an annular, flat metal plate welded to the base of the tank. It serves as the interface between the tank's sidewalls and the tank's foundation. The annular chime structure helps to stabilize the tank by transferring radial forces (typically due to hydrostatic pressure and temperature) from the sidewalls to the concrete base.
Unfortunately, the tank chime, while essential for tank stability, is an ideal location for the development of significant corrosion.
Corrosionpedia Explains Chime
Loads from the sidewalls compress the plate onto the foundation, thus applying a resultant flexural stress on the plate. This flexing causes the outer edge of the chime to lift off the foundation, which results in a gap between the chime and the concrete foundation. Differential settlement of the tank can also cause gaps to form around the tank periphery.
The ingress of moisture and external contaminants through the gaps and spaces around the annular chime is a major source of corrosion around the tank's base. Several methods, such as sealants and corrosion inhibitors, are typically employed to prevent or mitigate the effects of corrosion while the tank is in service.