PSI - Issue 59

Kozulin S. et al. / Procedia Structural Integrity 59 (2024) 391–398

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S. Kozulin et al. / StructuralIntegrityProcedia 00 (2019) 000 – 000 the holes was carried out using three electrode wires. After welding the central seam, two symmetrical seams were applied simultaneously from the middle of the joint to its edges (Fig. 5).

welding direction

Fig. 5 . Scheme of MESW CNof a through crack in the bandage of a cement kiln Ø 6.4/7×95m: 1 - bandage; 2 – technological plate; 3 - melting mouthpiece; 4 – forming insert; 5 - seam; 6 – entrance pocket; 7 – exit pocket; 8 – electrode wires; 9 – under band; 10 – shroud shell of the furnace body;  …  - sequence of passes. The transverse inserts were protected from full melting using copper water-cooled inserts, and the gaps between their ends and the band body were sealed with refractory clay. After welding, a local tempering of the multi-pass welded joint was performed using a portable electric furnace at a high tempering temperature of 550...600°C. Then, the kiln shell was rotated by ´ turn, and the external and internal pockets were cut off using a specially extended gas cutter. The working surface of the band was leveled with an abrasive stone, using pre-made templates. The total welding time was 22 hours, during which 1,360 kg of metal was deposited, including the remelting of 550 kg of metal inserts. The total time for repair work was 6 days. To perform these works using manual arc welding, it would have required at least 42 days. All work was carried out at a negative ambient temperature. The quality of the multi pass weld performed is good, confirmed by several years of operation of the welded joint as shown in the work of Kozulin (2004). The productivity of repairing cracks using the developed method increased by 8 times compared to known methods of manual and semi-automatic welding, and the costs for repair work were reduced by a factor of 3.0. All restored tires are successfully in operation to the present day. Based on statistical data on the trouble-free operation periods of tires repaired using the developed technology, it has been established that the long-term strength of welded joints under conditions of asymmetric alternating loading (- 40…+11 MPa) is not less than 10 7 cycles. To assess the effectiveness of repair methods for through cracks in tire bodies without their disassembly from the rotary kiln body, histograms of repair productivity for through cracks in rotary kiln tires and specific time costs for crack welding (Fig. 6) were constructed based on actual data. It is shown that the productivity of crack repair when using the developed welding method increases by 5…8 times compared to, for example, automatic dual -arc welding with flux. A comparison of the specific time cost s for welding 1 dm³ of the groove shows that with an increase in the cross-section of the welded joint, the effectiveness of using MESW CN for the repair of these defects increases. For enterprises operating rotary kilns in continuous production cycles, reducing the time for performing repair works has special significance, as it allows for a significant reduction in losses from the non-production of goods. For example, replacing a failed tire of a cement kiln Ø5×185 m with a new one by cutting the kiln she ll and disassembling the support block leads to losses of clinker reaching 20…85 thousand tons. Repairing a through crack in the tire directly on the kiln body using automatic dual-arc welding with flux reduces the specified losses to 19…33 thousand tons. When repairing a similar crack using the developed method, the production losses amounted to 0.8…1.3 thousand tons of clinker, which is 14 or more times less than when using automatic dual -arc welding with flux, and the total time for performing repair wor ks is 1.5…3 times (Fig. 7).