First, the failure phenomenon and analysis (A) failure phenomenon. When the door machine is overloaded with luffing movements, the boom system makes a jarring whistling sound, and the boom box is accompanied by jitter and resonance. After the company and manufacturer of technical staff to confirm the joint inspection, the sound is issued from the boom joint bearings Department. After a preliminary analysis, we think that the sound is caused by poor lubrication of joint bearings caused by dry grinding. (B) Analysis of the reasons. Most of the reasons for bearing damage in addition to poor lubrication, but also includes the lack of capacity overload and other external factors. To this end, we analyzed from these aspects: 1, overload: After calculation, the joint bearing parts bear the maximum load of about 1975kN, and bearing the rated carrying capacity of 10600KN. It can be determined, the bearing damage and overload is unrelated; 2, non-normal impact or management is not in place: The door machine to the bearing damage to the process of a short period of time, there have been no factors that may lead to bearing damage , Such as non-normal impact or long time no lubrication and so on. This can be determined, not accidental factors or management is not in place to cause damage to bearings; 3, lubrication: door lubrication system uses the "Shanghai Wufeng Electrolytic Engineering Co., Ltd." designed dry oil lubrication system. â‘ system structure: The system divides the door machine into boom system (boom and nose bridge), herringbone system and rotating large bearing alternately lubrication (each section has two main pipeline). The joint bearings for the door arm and nose bridge connection hinge, and the other hinge system with the boom hinge (roller) in parallel on the boom system of the two oil mains. â‘¡Working principle: When the centralized lubrication pump pumps the boom system, all the two lines of distributor (oil filling valve) are put into operation all the time according to the order of the two sides of the boom. At the same time, when the pressure in the main pipe rises and exceeds 5 kg of the main pipe in the other pipe, the pressure switch at the head of the two main pipes will act. The control system will automatically open the road and transfer it to the main pipe of another road, Point of the two-line distributor all the action so far. The pressure of the pipeline rises to two when the pressure drop reaches 5 kg again turn back to the first road, the end of a cycle. This working cycle until it reaches the road lubrication system set working hours to stop. From the phenomenon of bearing damage and lubrication system works two aspects of analysis, to determine the main reason is caused by poor lubrication. (C) Analysis of dismantling According to the above analysis, we first of all manual bearing on the bearings. After refueling, vibration and noise disappear. An hour or so after the experiment again appeared abnormal sound. We examined the centralized lubrication system carefully and found no abnormalities. However, vibrations and noise still appear after continued use, with no sign of diminishing. To this end, we decided to dismantle the bearing analysis. The first disassembly: 1, disassembled and found that the outer wall of the joint bearing collar when installed in the lower end of the arc angle of 30 to 40 degrees for several scratches; 2, the bearing shaft under the surface (In the mounting state) there is abrasion marks with a circular arc angle of about 180 degrees, forming a shoulder in the axial direction. The width of the wear zone is the same as the width of the joint bearing collar. The maximum height of the shoulder is about 3 ~ 4mm. According to the above phenomena and the analysis of the bearing and shaft lubrication hole structure, initially thought that there are three reasons for the wear and tear: First, the bearing and shaft body oil has its own defects, resulting in grease difficult to reach the pressure surface.