The crossed roller turntable bearing of the crane plays the role of connecting the upper part and the chassis part in the slewing mechanism, and also supports the whole rotating part of the crane. If the steel ball in the slewing bearing is damaged and the raceway is worn, the work of the slewing mechanism will be affected. In serious cases, the slewing mechanism will turn heavily and make noise. At the same time, the pressure of the slewing hydraulic system will exceed the rated value. When the slewing is stopped for lifting and unloading, the vibration of the slewing bearing will be too large down or up at the moment of falling together. The bearing clearance has exceeded the standard seriously. At this time, the slewing ring shall be repaired or replaced. The main reason for the mechanical failure is that the crossed roller bearing is not well maintained and used properly.
When the crane operates in an environment with strong corrosivity and more dust, or after heavy rain, it shall be wiped in time, the proper amount of lubricant meeting the requirements shall be added to the inside of the slideway, and antirust oil shall be applied to the outside. The oil injection nozzle should be dredged frequently to prevent clogging. The tightness of bolts shall be checked frequently to prevent the gap between the upper and lower slideways from being too large due to the loosening of bolts, resulting in the wear of steel balls and raceways.
There are two main reasons for improper use. One is that the levelness of the crane chassis is not good when lifting the slewing operation, or the four legs are not firmly padded when working on the soft ground, which will lead to the up and downslope in the whole slewing travel, resulting in the return speed and the required system pressure is not the same, so it is easy to cause uneven wear of the raceway, and at the same time, it also allows It is easy to cause slag or crack on the surface of the rolling element and accelerate wear. Second, when the basic arm of the crane is used to pull the heavy objects in a diagonal way and the heavy objects in a distant place are not lifted in a diagonal way, the slewing mechanism is often used to pull the heavy objects in the wrong way, which violates the safety operation regulations. At the same time, the cross roller bearing will also damage the slewing mechanism and the basic arm.
When the pressure of slewing hydraulic system is low, the sound and speed of the slewing process of the crane are normal under the condition of no-load and light load; when the crane is loaded with a heavy load, it will be difficult or even unable to turn. The reason for this phenomenon is that the spring of the overload buffer valve (see attached figure) of the rotary hydraulic system becomes soft. The pressure of the rotary hydraulic system is realized by adjusting the screw of the overload buffer valve. The adjusting screw also has the function of sealing the oil circuit. In order to ensure the tightness of the oil circuit, the screw must be tightened, but in this way, the spring pressure cannot be adjusted at will. When the spring pressure is not enough, it can only be solved by adding washers at the end of the spring, which is also adopted by most maintenance manufacturers.
When the operating handle of the slewing mechanism is pulled to make the slewing mechanism start to operate, so that the slewing brake and the slewing mechanism can not act synchronously, the crossed roller bearing namely the slewing brake is opened after turning, so that the slewing resistance is too large or even can not move. At this time, if we continue to increase the throttle and the angle of the slewing handle, the slewing pressure will be too high or even exceed the rated value, causing damage to other weak components or causing pipeline leakage. At this time, it is necessary to repair the brake oil circuit, clean or replace the hydraulic components in the oil circuit to keep the brake oil circuit unblocked.
Please check the Product Guide to select suitable bearings for your machinery.
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