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How to prevent accidental breakage of connecting rod bolts
When the connecting rod bolt breaks during operation, it will cause serious ramming accidents. It will not only cause damage to the cylinder head and cylinder liner, but also cause the connecting rod to deform and bend, and even cause major economic losses such as smashing the body and breaking the crankshaft. In order to avoid ramming accidents caused by breakage of connecting rod bolts, attention should be paid to the following points in use and maintenance: 1. The connecting rod bolt is subjected to a large alternating impact load during engine operation and is an important part of the engine. It is made of high-quality alloy steel through quenched and tempered processing and precision machining. It has high strength and impact toughness and is not available. General ordinary snails or inferior parts instead. If the bolt material, heat treatment, and machining accuracy do not meet the technical requirements, the mechanical strength will not be enough and deformation and fracture will occur. 2. Check carefully before assembly. When the bolt is found to have scratches, sliding buckles, cracks, dents, necking or cracks (application of oil or magnetic inspection inspection), or bolts, nuts with loose, or bolts can not be closely matched with the bolt hole, or use Observe by contrast method, the bolt length is 2% longer than the new standard bolt length and should be replaced. 3. Check the clearance between the connecting rod bearing and the connecting rod journal. If the clearance is too large, it will easily lead to the accident of the connecting rod bolt breaking. At this point should replace the new connecting rod bearings or increase the bearing, and to match or scraping. 4. Check the attachment of the connecting rod bolt or nut to the bearing surface of the connecting rod end cover shoulder. If there is any burr or unevenness, it should be repaired. Otherwise, the connecting rod bolt is subject to additional torque and easily broken. 5. When assembling, apply the torque wrench to alternately divide the connecting rod bolts (usually divided into 3 to 4 times) and evenly screw to the specified button moment. If the torque of the tightening button is insufficient, the connecting surface of the connecting rod will produce a gap. When the bolt is subjected to an impact force, it is easily broken or sheared; if the bolt is tightened too tightly, the bolt is deformed and deformed, the strength is reduced, and the bolt is easily broken after being subjected to stress. The torque of the connecting rod bolts of various engine models is not the same. In the absence of technical data, the safety torque range can be estimated based on the bolt diameter. For example, the MU connecting rod bolts have a safe torque of 60-80 Nm; M12 bolts. Its torque is 80-100Nm; M14 bolt, its torque is 100-120Nmo. 6. When the bolt is found to be excessive when the torque of one bolt on the same connecting rod exceeds the specified value, the two connecting rod bolts on the connecting rod shall be loosened and then alternately tightened in multiple stages to make the two bolts elastic. It is not allowed to loosen only the bolt that has been tightened too tightly. Otherwise, the bolt will have additional bending stress and be easily fatigued and fractured. 7. In the process of tightening the connecting rod bolts, it is necessary to turn the crankshaft to check if the rotation is easy. If the crankshaft is hard to rotate after the bolt is tightened, it is necessary to find out the reason. Never loosen the connecting rod bolt to rotate the crankshaft. 8. In order to prevent the looseness of the connecting rod bolt or nut during operation, it should be locked with a new locking pin, wire or locking piece and other anti-loosening devices; if the notch on the nut is aligned with the hole on the bolt, it can only be inwards in principle. Swivel alignment; used cotter pin, wire or lock piece shall not be used. 9. During use, the condition of the connecting rod bolts should be regularly checked. When the loosening is found, the cause should be checked. Check the bolts for any damage. Then use a power wrench to tighten the specified button moments to the specified value. 10. When the connecting rod bolt is loosened or extended during work, before the bolt is completely loosened and broken, a large knocking sound and vibration will be generated due to the looseness of the connecting rod bearing, and at this time, the vehicle should be stopped immediately to avoid further occurrence. ACCIDENT. 11. When a connecting rod bolt has a sliding buckle, cracks or breaks, the two connecting rod bolts on the same connecting rod should be replaced in pairs. 12. When the engine repeatedly burns watts or when the burning of tiles is severe, the connecting rod bolts are subjected to high temperature annealing, the metallurgical structure changes, the mechanical strength is reduced, and the bearing capacity is reduced. They should be replaced with new ones. 13. When the engine has a racing, biting or overturning accident, careful inspection of the connecting rod bolt must not be ignored. When the bolt is found to be deformed or cracked, it should be replaced in time. 14. In order to prevent fatigue fracture damage of connecting rod bolts, after the engine has accumulated 6000-7000 hours of work, even if the external elements of the bolt are significantly damaged, it should be replaced.