Causes and Precautions for Cracks in the Rotary Kiln Shell
Causes and Precautions for Cracks in the Rotary Kiln Shell
Due to various factors, the rotary kiln equipment often experiences shell cracks in actual production. This situation results in significant losses for companies. Therefore, this article aims to analyze the main reasons for the occurrence of cracks in the rotary kiln shell and propose specific measures to prevent cracks, providing reference for rotary kiln users.
Common places where cracks occur are the wheel belt, the weld seams on both sides of the large gear ring, and the weld seams on other parts of the shell. When there are many cracks on the shell, the repairability of the shell is poor, and the shell must be replaced before use. There are two common types of cracks: longitudinal and circumferential cracks. Longitudinal cracks typically occur at the shim plate and weld seams between the wheel belt and the shell, while circumferential cracks occur at the weld seams on both sides of the transition zone between the wheel belt.
Causes of longitudinal cracks:
When designing the shell, thinner steel was selected as the material for the shell, resulting in insufficient steel thickness to ensure transverse stiffness without ensuring the required transverse stiffness and longitudinal flexibility of the rotary kiln. Therefore, under the action of the alternating stress and pulse stress generated by the self-weight and support reaction force of the wheels, the material is prone to deformation, and cracks may form in the welded heat affected zone. In addition, the thickness and width of shim or baffle plates are too wide or thick, causing excessive stiffness at that point and smaller stiffness at other places. During operation, the baffle will hinder the movement of the shell, resulting in radial free bending deformation. Therefore, thicker and wider baffle or shim plates will result in greater resistance. Once exceeding the ultimate strength limit of the steel plate, cracks will also occur.
In terms of installation, many users often only focus on the cold accuracy of the rotary kiln, ignoring the hot accuracy of the kiln during operation. As a result, when the rotary kiln is running, each gear center is not on a straight line, causing uneven stress on both sides of the wheel belt. The shell may crack due to uneven stress. In addition, for installation convenience, objects such as lifting rings are welded randomly on the shell. After use, they are not removed as required. This not only damages the strength of the shell but also causes stress concentration, resulting in shell cracks.