Among the core components of cranes, the wire rope drum is not the most eye-catching, but it is like a silent "strongman", responsible for winding, retracting and releasing the wire rope day after day, which is directly related to the safety of heavy lifting. However, this "strongman" also has a fragile side. Under long-term high-load operation, various faults will quietly come to the door, and a little carelessness may lead to a disaster. Today, let's talk about the common "problems" of the drum to help practitioners take precautions in advance.
The drum wall and rope groove are the places where the force is most concentrated. When the crane lifts heavy objects, the tension of the wire rope will cause the drum to bear bending stress, and during the repeated retraction and release process, this stress will continue to act on the metal like a "tug of war". Over time, fine cracks will appear in the thinner parts of the drum wall or at the bottom of the rope groove. At first, they may be only a few millimeters long and difficult to detect with the naked eye, but as the number of hoisting increases, the cracks will spread like tree branches.
There is a real case: a gantry crane at a port had a drum that had been used for more than 8 years without a comprehensive inspection. When hoisting a 40-ton container, the cracks at the bottom of the rope groove suddenly expanded, causing the drum wall to partially collapse and the wire rope to jump out of the groove instantly. Fortunately, the safety device braked in time to avoid an accident. There is a consensus in the industry: when the crack depth exceeds 10% of the drum wall thickness, or the length reaches 1/5 of the rope groove circumference, the drum must be scrapped immediately and must not be "put into service with a problem".
The drum can rotate, and the power is transmitted by the drum shaft and the connecting key. The drum shaft is like a human "spine", which has to bear the dual pressure of torque and bending moment; and the key is like a "joint", which is responsible for fixing the relative position of the drum and the shaft. In long-term operation, the friction between the shaft neck and the bearing, and the extrusion between the key and the keyway will make the matching clearance larger and larger.
The most intuitive manifestation is that the drum will "sway" when starting or braking, accompanied by a "clicking" sound. This situation has occurred in a crawler crane at a construction site. Inspection found that the key has been worn to only half the thickness, and the shaft neck has also been worn out. If it continues to be used, it is very likely that when lifting heavy objects, the key will be suddenly cut off, and the drum will be thrown out after the shaft loses its fixation, and the consequences will be disastrous. According to regulations, if the wear of the shaft exceeds 3% of the original diameter, or the wear of the key exceeds 5% of the original size, a new part must be replaced.
The function of the rope groove is to guide the wire rope to be arranged neatly and reduce mutual friction. However, when the wire rope is repeatedly wound in the rope groove, it is like sandpaper that constantly polishes the groove wall. Over time, the rope groove will become wider and shallower, and even "flare" deformation will occur.
Don't underestimate the wear of the rope groove, it is very harmful: on the one hand, after the rope groove becomes wider, the wire rope will "slip" in the groove, resulting in chaotic winding, and in severe cases, it will jump out of the rope groove and be squeezed and deformed; on the other hand, the rope groove is not deep enough, which will reduce the contact area between the wire rope and the bottom of the groove, increase local stress, and accelerate the wire breakage of the wire rope. The industry standard clearly stipulates that when the wear of the rope groove reaches 15%~20% of the original wall thickness, or the error of the groove bottom diameter exceeds 5mm, the rope groove must be re-turned or the drum must be replaced.
In addition to the above problems, the drum may also be deformed due to unexpected force. For example, sudden overload during hoisting, or heavy objects hitting the drum, may cause the drum to bend and the flanges at both ends to tilt. The deformed drum will produce strong vibrations during operation, which will not only increase its own wear, but also cause uneven force on the wire rope, posing a safety hazard.
Experienced masters know that drum maintenance cannot only look at the surface. It is necessary to regularly check the straightness of the drum with a ruler and measure the verticality of the flange with a dial indicator. Once the deformation is found to be excessive, even if it does not affect temporary use, it must be repaired in time to avoid small problems from becoming major failures.
Although the drum is small, it is the "throat" of the safe operation of the crane. For practitioners, regular inspections (recommended at least once a month), good lubrication (grease is added to the journal and bearing parts every week), and avoiding overloaded hoisting are all key to extending the life of the drum. After all, in lifting operations, the "small temper" of any component may lead to irreversible consequences. Keeping the safety of the drum is to keep the bottom line of the entire hoisting operation.
Contact Person: Mr. kalai
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