Repair plan for shifting balance beam of walking f

2022-08-04
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Bucket wheel excavation has brought confidence to extruder enterprises. It is a compact mining equipment jointly manufactured by Austria and Kunming heavy machinery factory. The VABE550 excavator is a kind of compact mining equipment. It is used for stripping earth and mining coal. The theoretical production capacity of the machine is m/h, the total installed power is 1210kw if polystyrene board and polyurethane are widely used, and the service weight is 500t. It was put into production in 1993. In November, 1998, the bucket wheel machine was severely vibrated during operation. After a comprehensive inspection of the main platform slewing mechanism of the walking frame support mechanism that may cause vibration by the engineering technicians and maintenance personnel, it was found that the horizontal balance beam between the two crawler frames of the walking frame had seriously shifted to a point supported by the three points at the bottom of the middle of the balance beam, bearing the weight and cutting force of the upper carriage. The weight of the upper carriage was 340t, the coupling diameter was 300mm, and one end had been out of the support seat, Leave the anchor point. In the process of slewing operation, the bottom support loses balance and inclines and vibrates. Through further inspection, it was found that the positioning hole of the bottom seat and the supporting hole of the balance beam were increased by mm due to the movement of the side shaft; All four M20 high-strength bolts on the locating plate at the bottom of the coupling are cut off

1 displacement and causes

compared with the domestic wd520/0.9 15 bucket wheel machine, VABE550 bucket wheel machine adopts a static three-point floating support connected with the bottom seat and the crawler frame, with balanced bearing force. The two crawlers can rotate in the y-axis direction, which is conducive to maintaining the upper balance on the uneven ground of the mine (see Figure 1)

1. Transmission 2 Bottom seat 3 Track 4 Track frame 5 During the operation of balance beam

bucket wheel machine, the main machine continuously moves forward, backward and turning with the advancing surface of the working face. The ground condition is complex during operation, especially when there is no bulldozer to level the tunnel face, the tunnel face is uneven. Therefore, the force on the balance beam also changes constantly. From the function and fault phenomenon of the balance beam, the problem may be analyzed from two aspects: the imperfect design of the tunnel face conditions. First, the bucket wheel machine used for stripping coal is used to excavate quaternary topsoil. Its organizational characteristics are: large water seepage, diversified soil structure sections (clay, sand layer, coke clay layer, etc.). Although the bucket wheel track grounding pressure reaches 110kpa, sometimes it will cause the shoe belt to sink and the center of gravity of the whole machine to shift, which will cause excessive stress on the bottom balance beam, damage to the device components and displacement of the balance beam. Second, the substructure and the balance beam bear a large load on the superstructure, and the same center of gravity changes during operation, so the load added to the balance beam changes greatly. The side shaft of the balance beam is positioned with four M20 bolts, which is not strong enough, causing the bolts to be subject to shear force. The thickness of the support hole plate of the support side shaft is 50mm. During inspection, the hole is worn by mm, and there is pressure hole, indicating that the design strength of the support hole (see Figure 2) is insufficient

1. Track frame 2 Ball comparison 3 Track edge hole 4 Balance beam support hole 5 Balance beam coupling 6 Set bolt 7 Locating hole 8 Balance beam 9 Support hole 10 Reinforcing plate 12 To sum up, due to the imperfection of the design affected by the geological structure, the substructure and the balance beam coupling work under the high stress state, which accelerates the wear of the support hole, resulting in the shear of the positioning bolt and the outward movement of the coupling, resulting in the displacement of the balance beam

2 repair and acceptance

2.1 existing problems

as one of the load-bearing beams of the bucket wheel machine, the balance beam is located below the platform, with a dead weight of 5.7t. From the analysis of the fault situation, it can be handled after disassembly. In this way, the following problems must be solved:

(1) disassembly method: the weight of the 340t upper structure is the same as that of the balance beam connected with the side shafts at both ends of the base and the crawler frame to form a three-point support. If the balance beam is disassembled, the stability relationship of the straight point support will be destroyed

1 drawing into a cylindrical cup

(2) jacking method: remove the coupling shaft at both ends of the balance beam and the crawler frame, so that it must not bear gravity, so it is necessary to jack up nearly 400t above the crawler frame

(3) repair or replacement: it takes 114000 yuan to make a new balance beam. The manufacturing and installation cycle is six months. The bucket wheel machine is shut down and the indirect loss is 3million yuan. It is not possible to recover the equipment economically and quickly, so it is decided to adopt the repair scheme

2.2 repair plan

(1) rotate the counterweight of the main platform of the bucket wheel machine to the other side of the balance frame to minimize the load at the end of the walking balance beam, and use four 200t hydraulic jacks to push the bottom of the counterweight box and the side of the balance beam of the bucket wheel machine base respectively, so that the balance beam does not bear gravity. This scheme ensures that the balance can be disassembled without load. When the balance beam is disassembled, the weight of the whole machine is supported by four jacks to ensure stability

(2) surfacing and boring shall be carried out for the support hole of the balance beam with excessive wear to ensure the matching size of the hole diameter

(3) two support holes of the balance beam I are not strong enough. Add a flange plate outside the shaft hole respectively, and drill 6 welding plug holes for welding. In this way, the original shaft hole wall thickness is 50mm and increased to 100mm. The flange plate shall be bored, and the hole diameter shall match the original diameter of the shaft diameter

(4) the original number of locating bolts at the top of the coupling is 4, but now it is increased to 8 to ensure high strength

according to the above repair scheme, the equipment was put into production within 15 days from disassembly, processing to installation and commissioning. By adopting such a repair scheme, the equipment faults are eliminated, the bearing capacity of the machine structure is enhanced, the time to solve the problems is greatly shortened, and the economic losses are reduced

2.3 commissioning and after-sales inspection are the most critical parts.

before the bucket wheel machine is put into production, we conducted a dynamic experiment on the performance of the repaired balance beam

(1) rotate the platform to make the center of gravity of the bucket wheel machine turn to the end of the balance beam. At this time, the load of the balance beach reaches the maximum. Check the bearing condition of the balance beam

(2) the bucket wheel moves forward and backward, turns, and observes the adjustment effect of the balance beam

(3) carry out 72h excavation test, then check the welding condition and whether the support hole of the balance beam has displacement change. After no-load excavation test before production, all device components operate normally, indicating that the repair process of the repair scheme is correct

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