2022-01-07 News Views 1162
The fracture of connecting rod bolt of diesel engine in operation will lead to serious cylinder tamping accident, which will not only cause the damage of cylinder head and cylinder liner, but also cause the deformation and bending of connecting rod, and even cause great economic losses such as tamping body and breaking crankshaft. In order to avoid the cylinder ramming accident caused by the broken connecting rod bolt, the following points should be paid attention to in the use of maintenance:
1. In use, the tightness of the connecting rod bolts should be checked regularly. When the loosening is found, the reason should be found, and the bolt should be checked for damage, and then screwed to the specified value with a wrench.
2. When a connecting rod bolt has slip, crack or fracture, the two connecting rod bolts on the same connecting rod should be replaced in pairs, and the old and new ones should not be used together.
3. When the engine repeatedly burning tile or a serious burning tile, the connecting rod bolt material by high temperature annealing, mechanical strength and bearing capacity decline, should be replaced.
4. Check the connecting rod bolt or nut and connecting rod end cover shoulder support surface of the fit, if there is burr or uneven, should be polished, otherwise the connecting rod bolt by additional torque, easy to break.
5. when assembling, the connecting rod bolts shall be twisted alternately by torsion wrench (generally divided into 3~4 times) to the specified torque. If the torque is too loose, the connecting rod joint surface in the work has a gap, the bolt is easy to be pulled or cut off by the impact force; Screw too tight, bolt elongation deformation, strength reduction, easy to break after force damage. The specified torque of connecting rod bolt of each type of engine is different. In the absence of technical data, the safe torque range can be estimated according to the bolt diameter.
6. When the engine speed, bite cylinder or overturned accident, must not ignore the connecting rod bolt careful inspection, when found bolt deformation, crack damage, should be replaced in time.
7. In order to prevent fatigue and fracture damage of connecting rod bolts, the bolts should be replaced even if there is no obvious damage on the outside after 6000~7000 hours of engine operation.
8. When the connecting rod bolt is loose or elongated in the work, there will be a large knocking sound and vibration. Before it is completely loose and broken, it should be stopped immediately to avoid a bigger accident.
9. Connecting rod bolt is made of high quality alloy steel after quenching and tempering treatment and precision machining, with high strength and impact toughness, can not be replaced by ordinary bolts or inferior parts. If the bolt material, heat treatment and processing accuracy do not meet the technical requirements, it will lead to insufficient mechanical strength and deformation and fracture accidents.
10. In order to prevent the connecting rod bolts or nuts loose in the work, should use a new split pin, iron wire or lock plate and other anti-loose device locking; If the notch on the nut is not aligned with the hole on the bolt, it can only be rotated inward to be aligned in principle; Used cotter pins, wires or lock plates should not be reused.
11. and check carefully before assembling, when found a scratch on the bolt, slide fastener, cracks, dents, necking or cracking (application oil immersion method inspection or magnaflux inspection), cooperate flabby bolt, nut, bolt can't work closely with the bolt hole, or use of measuring tool to check the bolt length is longer than the new standard bolt length of 2%, all should be replaced.
12. Check the connecting rod bearing and connecting rod journal matching clearance, if the clearance is too large, easy to lead to the connecting rod bolt fracture accident. At this time should replace the new connecting rod bearing or increase the bearing, matching or scraping.
13. When making bolts, if it is found that the torque of a bolt on the same connecting rod exceeds the specified value too much, the two connecting rod bolts on the connecting rod should be loosened and tightened alternately again, and the two bolts should be the same tightness. It is not allowed to loosen only the bolt that is too tight, otherwise the bolt will produce additional force, easy to fatigue fracture.
14. In the process of tightening the connecting rod bolt, try to rotate the crankshaft to check whether it rotates freely. If the bolt is tightened, it is found that the crankshaft is difficult to rotate, and the reason should be found.