Crane girder sinking cause analysis

Crane girder camber called girders sinking gradually decreases , that downward from the original camber produce permanent deformation. Below the level of the main beam provides permanent deformation called lower torsion . Girders sinking because of the following categories:

1, the structure of internal stress effects:  hoist gantry crane  metal structures exist in all parts of pulling in different directions , pressure and other stress . Fly these forces produced mainly in the manufacturing process of structural forces of deformation caused by assembling building . Further, since the welding process locally uneven heating , will result in contraction of the weld and surrounding metal , leading to the main girder residual internal stress , and thus the load under the action of the beam will have a great stress winner and cause permanent deformation. Structure residual stress , during use of the crane tends to homogenize even disappear constantly , causing the main beam of sinking.

2 , the use of irrational : the crane is within the specified conditions of use designed , for overload and other irrational use is not be considered. But a lot of use of units not pay enough attention to this long-term change in the type of work overload and use , as well as for dragging heavy objects , pulling anchor bolts and so on. According to the survey , many units of the crane is because of this irrational use damaged .

3 , unreasonable Repair : Since no master steel crane  metal structure structural deformation caused by heating of the law, and therefore did not take measures to prevent deformation , the bridge on the cutting or welding , resulting in severe deformation of the main beam , in addition, take stage heating will cause the main beam inward lateral bending of the end beam heating , not only the end of the beam back to the deformation , and will affect the main beam deformation. Therefore, we should grasp the deformation of the metal structure to avoid heating the structure must when welding or cutting , as the case may be , to take measures to prevent deformation .

4 , High Impact: According to droop , thermal processing plant using a crane used crane than the cold floor of the main beam sinking phenomenon is more common, more severe degree of subsidence , such high temperatures are mostly caused by radiant heat . This is because the high temperature environment , to some extent, to reduce the yield strength of the metal material , on the other hand the high-temperature environment , thermal stress is generated , which increases the likelihood of sinking of the main beam . It is notable that , smelting radiant heat will cause the cover under the main beam temperature greatly exceeds the upper cover , the cover is to make thermal elongation greater than under the cover of thermal elongation , under the effect of the load leads to the main beam camber natural decrease. So, in a radiant heat environment using cranes, metal structure lower insulation measures should be increased to reduce the temperature of the metal structure.

5 , unreasonable lifting cranes , storage, transportation and installation of : crane bridge is raised structure, greater flexibility, unreasonable storage, transport , lifting and installation may cause deformation of the bridge structure . The use of the bridge gantry crane  units should pay attention to proper use , abide by the rules and the necessary institutional , which prolong life and prevent the crane girders sinking is extremely important.