Repair of hydraulic cylinder of the hottest front

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Repair of the hydraulic cylinder of the front hoist

our company has successively purchased several front hoists from Europe. Due to its structural design, shortly after its production, its hydraulic cylinders suffered major failures (the telescopic piston rod of the boom was scratched, and the cylinder lifting joints such as the engine nacelle, ailerons and aircraft wing beams were cracked), resulting in serious oil leakage, although the manufacturer replaced them free of charge, However, similar phenomena occurred one after another shortly after the replacement. Therefore, we have improved it, and the effect is good

when disassembling and inspecting the telescopic cylinder of the boom, it was found that the piston rod was severely scratched locally, the scar was mm long, mm wide and mm deep, and the supporting ring of the guide sleeve was worn and deformed. The analysis shows that the main reasons for the scratch of the piston rod are: the support ring deforms at high temperature and the support strength is not enough; The fit clearance between the guide sleeve and the piston rod is too small, and they rub against each other due to expansion at high temperature, resulting in "hard hitting hard", resulting in the wear of the piston rod

in addition, cracks were found at the connection between the lifting cylinder and the joint during disassembly and inspection, which have extended to the inner wall of the cylinder barrel, about mm long. The main reason for cracking: because the oil inlet steel pipe is connected with the cylinder barrel through welded joints, the oil inlet steel pipe vibrates greatly under the action of high-pressure oil, which is easy to cause resonance of the cylinder barrel; At the same time, the thickness of the connection between the cylinder barrel and the joint is only 15mm, and the bearing capacity is not enough, resulting in cracks

repair method of telescopic cylinder

clean the scratched part of the piston rod, and conduct tensile tests on scratched ribbed steel and other bars with stainless steel electrodes; Universal tensile testing machine, round sample jaw 26 (4) 0mm1 pair, suitable for tensile tests of round steel, ribbed steel and other bars with a diameter of 26 (4) 0mm; Repair welding shall be carried out on the parts, and asbestos insulation shall be tested with metal tension and pressure in the wet material experiment to prevent the temperature from being too high; After natural cooling, preliminarily repair the surrounding of the repair welding with a hand file; Then process a mold and grind the piston rod with the sand bar until the roughness meets the assembly requirements

reprocess the guide sleeve, reducing the number of support rings on the guide sleeve from 4 to 3 (see Figure 1a. B), but the total support width increased from 80 mm to 90 mm, bringing confidence to extruder enterprises. At the same time, increase the inner diameter of the guide sleeve support ring by 0.02 mm, and increase the fit clearance between the guide sleeve and the piston rod; Phenolic materials with high strength and toughness are selected to process the support ring, and its width is increased from 20 mm to 30 mm

cut off the lifting cylinder barrel from the B-B surface, and process the connecting thread in the inner hole of the cylinder barrel from a to B, with the length of 60 mm; Reprocess the head of a cylinder barrel with 45 ; Connect the processed cylinder head with the original cylinder thread, and weld the outer joint; The original oil inlet steel pipe can be replaced by a high-pressure hose

after repairing the hydraulic cylinder of the front hoist, there has been no oil leakage since its use, and the effect is good

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