Damaged form and cause analysis of crane steel beam

We know that the steel beam is the most important part of the crane. It determines how much load the crane can carry. Then, what failures usually occur in the steel beam of the crane, and what are the forms of damage?

1. Surface corrosion (interpretation: refers to decay, disappearance, erosion, etc.)

The working environment of the crane is harsh. It usually works in gas dust (form: solid particles) containing acid-base corrosion (interpretation: refers to decay, disappearance, erosion, etc.). In addition, the collision during operation and the natural aging and peeling of the anti-rust coating make the surface lose its protection. In addition, maintenance work is not timely, resulting in partial corrosion and oxygenation, varying degrees of surface rust, reducing the strength of steel beams, and making steel knots for a long time. Structural deformation, which is also a common failure of the main girder of a double-beam crane.

2. Crack

Practice has proved that although cracks do not necessarily lead to fractures, it is very important to find and deal with them in time. Single-girder cranes usually refer to single-girder bridge cranes. The main beams of single-beam crane bridges mostly use I-shaped steel or a combined section of steel and steel plates. The hoisting trolley is often assembled by chain hoists, electric hoists, or hoists as parts of the lifting mechanism. The single beam crane has two operation modes: ground and air. There are two types of ground operation: wired handle operation and remote control handle operation; aerial operation refers to operation in the driver's cab. The driver’s cab has two types: open and closed. It can be divided into two types for installation on the left or right according to the actual situation. There are two types of entry directions: side and end to meet the needs of users. Even if it is not repaired in time, long-term work is often the initial stage of cracks, especially the transition period and dangerous cracks. Generally speaking, cracks mainly occur in the welding part and the part where the stress is concentrated.

3. Deformation

It includes partial bending (Bend) deformation, twisting and eccentricity. According to the metal structure inspection requirements, the straightness tolerance of the rod along the longitudinal axis is 1/750. In use, the deformation of the main chord should not be more than 3 permil; -5 permil;; the deformation of the web should not be more than 2-4mm; the hole distance error of the rod connecting bolt (composition: head and screw) should not exceed the assembly (assemble) 1/2 of the gap; and the roundness error of the screw hole does not exceed 1/2 of the assembly gap; when it exceeds the above range, it is deemed deformed.

The reasons for the deformation of the crane steel beam are as follows:

(1) The local bending deformation of steel beam is caused by collision and impact. The single beam crane has two operation modes: ground and air. There are two types of ground operation: wired handle operation and remote control handle operation; aerial operation refers to operation in the driver's cab. The driver’s cab has two types: open and closed. It can be divided into two types for installation on the left or right according to the actual situation. There are two types of entry directions: side and end to meet the needs of users.

(2) Due to the loosening of the connecting bolts (composition: head and screw), the bolt holes are ground into an ellipse, resulting in eccentricity of the arm and additional bending moment.

(3) Accidental collision and deformation of steel beams are caused by wrong actions. If the operating mechanism (organization) fails, the boom will reverse uncontrollably, and collision with the tower will cause serious deformation.

(4) Long-term overload causes the steel beam to yield deformation (permanent deformation).

In addition to steel girder failures, there are other failures of the crane that should be paid special attention to. For details, please refer to the common failures and removal methods of general double girder bridge cranes.

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