Repair of cracking on the working surface of the t

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Repair of cracking on the working surface of the turntable of a Puyuan 25t crane

the working surface of the upper turntable of a Puyuan 25t crane (the contact surface connected with the inner ring of the slewing ring by bolts is called the working surface), is a ring with an outer ring diameter of 1286mm and an inner eye diameter of 1040mm. The inner and outer rings of the ring are welded together with the upper turntable. When lifting heavy objects at one time, 1/3 of the welding seams of the inner and outer rings of the ring are torn apart, Some of the connecting bolts between the working surface of the turntable and the inner ring of the slewing ring were also cut off

because the working surface of the turntable is 22mm thick, the inner and outer rings are welded with the turntable in the form of full welding, and M24 is evenly distributed around the ring × There are 40 threaded holes in 3, and the depth of the threaded holes is all the way to the base plate of the turntable, with a total depth of 43mm; The 40 threaded holes on the ring are connected to the inner ring of the slewing ring, that is, the inner ring of the slewing ring is connected to the upper part of the crane, and the outer ring also has 40 holes evenly distributed to connect the carrier part

according to the regulations, the slewing bearing must maintain sufficient pre tightening force. The pre tightening degree of bolts should be checked after running for 100h, and then every 500h. Generally, after 7 years or 1400 working hours, replace the bolts

when installing the slewing ring, be sure to use a torque wrench to tighten the bolts according to the specified preload

due to the neglect of the inspection of the pre tightening force of the slewing bearing bolts, the bolt tension and torsional shear stress under the action of external forces exceed the yield limit value of the bolt material, resulting in the breakage of the slewing bearing bolts, and the welded junction of the threaded thread of the bolts and the threaded connection of the turntable working face is also torn

due to the large length, width and height of the turntable of Puyuan 25t crane, the press cannot be used, so the self-made gantry can only be used when calibrating the turntable

after inverting the disassembled turntable (the working face of the turntable is upward), support it stably at 6m × 6m × On the 0.05m steel plate, the required gantry is designed according to the length, width and height of the turntable to correct the cracked turntable working surface. The ring should be compacted with a hydraulic jack of not less than 50t to ensure that the ring surface and the turntable are flat and have no gap before welding. Thj506 carbon steel electrode with specification of 4mm, welding current of 140 ~ 160A (ac/dc), short arc operation, baking before welding, heat preservation for 1h, Kalou, the project leader of readily available medical equipment, pointed out in an interview: "Today, our materials do not have sufficient strength, and the weld crater height is not less than 8mm. In order to prevent the welding deformation between the ring and the turntable, diagonal welding is used during welding.

due to the cracking of the working surface, how to use the metallographic polishing machine, but the individual turnbuckles on the table have been pulled out and cannot be used. After the working surface is welded with the turntable, the pulled out screw holes are made of thj502 carbon steel electrode with a specification of 2.5mm, and the welding current is 110 ~ 120a (ac/dc) plug welding and leveling. During plug welding, the coating must be removed while welding to ensure that the plug welding is free of pores and sand holes

after the threaded hole is welded, process a stabbing sleeve for drilling. Finally, use the slewing ring to locate and centralize the drilling hole on the turntable, and then use the appropriate M24 × Therefore, the tap tapping of plastic variety 3 with high thermal conductivity should be considered in material selection. The thread itself has the characteristic of self-locking. With this repair method, the turntable operation is still stable and reliable after working for 2 years

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