Usually, a new single-girder crane has a trial run period before it is officially used, which is also called a “run-in period” in the industry. Cranes are generally required to have a running-in time of 60 hours after leaving the site. The purpose of running-in period is to ensure the normal operation of the single-girder crane, reduce the incidence of failure, and prolong the service life and work efficiency.
In reality, many users ignore the running-in period when using single-girder cranes and use them directly, which may often lead to frequent failures, seriously shorten the service life of the machine, and naturally affect the progress of the project.
The assembly and processing of the parts of the new machine will be affected. The initial friction is high, and the pressure on the surface is uneven. The friction will be even greater during the operation of the machine, which will often produce a lot of metal debris and accelerate the wear of the surface of the parts. If the load is operated at this time, it may directly lead to damage to the parts.
The friction of new parts is high. One of the main reasons is that the lubricating oil between the cranes cannot achieve a suitable effect. Early abnormal wear may cause scratches and seizures on the surface of precision parts.
The new single-girder crane may have dimensional and geometric errors between the components, and it will be deformed due to the impact of vibration and impact at the initial stage. In addition, wear and tear may cause the components to loosen. In view of the above conditions, users are requested to run it empty before the crane is shipped from the manufacturer for official use.
During the use of lifting machinery, mechanical parts, electrical control and hydraulic system components will inevitably undergo physical wear and cause failures. The cause of the same failure cannot be a one-to-one correspondence. Therefore, it is necessary to carefully analyze the fault, accurately find out the real cause of the fault, and take corresponding methods to eliminate the fault, so as to restore the technical performance of the fault point. The following describes the common fault analysis and troubleshooting methods of bridge gantry cranes, gantry cranes, electric hoists, etc.
Long-term load use is the main reason for the fatigue crack failure of the main girder web or cover plate.
When the inspection finds that the fatigue crack is not larger than 0.1mm, it can be ground with a grinding wheel; for larger cracks, 8mm small holes can be drilled at both ends of the crack, and then 60° grooves can be made along both sides of the crack for repair welding. Important stress components should be repaired and welded with reinforcing plates to ensure their strength.
During production, if the original welding quality is poor and there are welding defects, use good welding rods for repair welding; during repair, due to improper welding process, residual stress or long-term load use, etc., you should use a reasonable process to polish the desoldered part before welding, and it is strictly forbidden to load after use.
The reason is that the welding internal stress is generated by improper welding process, or the web is partially unstable due to the use of load.
If this fault is found, acetylene welding can be used for local heating, and then hammering can be used to eliminate the deformation internal stress. It is strictly forbidden to use the crane with load. After flame straightening, the wave deformation caused by the local instability of the web can be eliminated.
When the crane is manufactured, the welding process is improper, and the deformation caused by the superposition of welding internal stress and working stress should be heated on the convex side of the main girder with acetylene welding and equipped with appropriate top tools and pullers, and the side bending deformation of the crane should be eliminated by flame straightening. For the side bending deformation of the main girder caused by improper transportation and storage, in addition to using the flame correction method to eliminate the side bending of the crane, the correct method should be used to transport and store the crane in the future to avoid the recurrence of the side bending deformation.
Excessive internal stress of the main girder structure of the crane, improper storage and transportation of the crane, use of the crane for loading, or harsh operating environment, excessive heat effect, etc. may cause the main girder to sink and deform. Acetylene welding and baking can be used to correct the deformation and then reinforced with channel steel along the lower cover plate of the main beam, and the sinking deformation can be eliminated. It can also be corrected by stress method.
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