A TY160C crawler bulldozer (with Cummins NT855-C280 diesel engine) suddenly turned off after less than 15 minutes of starting operation. At this time, the diesel generator's working hours displayed on the timer was 1480 hours.
According to the preliminary analysis, it may be that the battery is discharged too much and the battery capacity is not enough to enable the starter to drive the diesel engine. Therefore, the battery for the TY220 type bulldozer is replaced (the battery has a larger capacity than the TY160C), and the result is still the same. The TY160C's battery can successfully start the TY220, which can prove that the battery is not faulty. It is also believed that the starter may be faulty and cannot drive the diesel engine, but the no-load test result of the starter is normal, indicating that the starter has no fault. When using a crowbar (inserted from the starter mounting hole) to move the diesel flywheel ring gear up and down, it was found that the ring gear did not turn, indicating that the resistance of the mechanical part of the diesel engine or the diesel engine was greater than the starting force of the starter, resulting in the diesel engine not Operation. Based on this, it is believed that there may be diesel engines, power transmission boxes, and torque converters at the site of possible failure. The failure of the diesel engine may include: hard objects in the cylinder, so that the piston can not run, burning tile holding shaft; timing gear stuck and so on. Failure of the power transmission case may include: gear stuck; hydraulic pump damage and hinder the drive gear rotation. The torque converter failure may be part damage.
At the time of investigation, it was decided to remove the torque converter first. The reason was that the first time it came into contact with a Cummins diesel engine, the machine had a large difference in structure from that of a domestic machine. In the case of immature maintenance technology, inexperience, and failure to determine if it was faulty Large-disassembly and large-discharge should be avoided; the torque converter is lighter than the diesel engine, and the number of connecting parts is small, so it is easy to disassemble and facilitate maintenance. That is, after the torque converter is removed, the torque converter and the torque converter can be replaced. The previous work force transmission box is visually inspected: if the power transmission case and/or torque converter is faulty and the diesel engine fails, the diesel engine does not have to be removed. If the diesel engine has a fault and needs to be removed for maintenance, it will be removed sooner or later. Converter.
After removing the torque converter and turning the torque converter power input driving gear by hand, the torque converter operates smoothly without any jamming. It can be initially determined that the fault is not in the torque converter, and the middle of the power transmission case that is engaged with the flywheel ring gear is disassembled. Gears, which can be easily turned by hand to drive the various gears of the hydraulic pump, indicate that the fault is not an automatic transmission. At this time, the flywheel of the diesel engine still cannot be stopped. Therefore, the fault location can be judged on the diesel engine.
The engine oil was discharged and filtered. It was found that there were more debris in the oil, but the source of the debris could not be determined. The oil pan was blocked by the bulldozer beam and it was not convenient to do the demolition inspection. The diesel engine was then hung down.
During the inspection of the diesel engine, it was found that there are two half-rings in the oil pan (four rings in total, used to adjust the axial barrier of the crankshaft) and the other two pieces have also been worn, ablated, and adhered to the crankshaft; The bearing of the main bearing is severely ablated and the shaft is held so that the crankshaft can not rotate. Each bearing has a different degree of damage. Pushing the piston connecting rod group to the direction of the cylinder head can push, indicating that there is no hard object in the upper part of the piston and therefore it has not been disassembled. The cylinder head is used for inspection; there is no jam in the gears in the timing gear chamber.
Due to the large damage to the surface of the seventh main journal, the determination of grinding of the entire crankshaft after measuring the other main journals and the connecting rod journals has reduced the size by 0.25 mm. After grinding, each main bearing is reassembled and gradually tightened (one force per crankshaft, one crankshaft per revolution). When the standard torque is applied to the crankshaft, the crankshaft cannot be turned. After the inspection, the seventh main bearing is found. It was scratched, and at the same time there were two white lines on the main axis of the seventh track. The magnetic flaw test proved that it was two cracks. According to the analysis, the cracks are generated due to overheating when the bearings are burned or held on the shaft. When the bearing bracket fastening bolts are tightened to the standard torque, the journals are deformed and the cracks are increased. When the crankshaft is turned, the new bearings are scratched. The new bearings, new crankshafts (all standard) and assembled as required after the test machine, normal operation, indicating that the fault has been ruled out.
According to the analysis, the reason why this machine suffered from a serious accident with the burning of the shuffling shaft was that the oil filter was not replaced as required. It was learned afterwards that this machine only changed the oil and oil filter after the new machine was run in. , and no oil and oil filters have been replaced in the next eight months (more than 1,000 hours). In particular, after winter, no maintenance has been carried out, and the manual requires The oil and oil filter should be changed every 250 months or once every six months, and the replacement cycle can be shortened if necessary.
The analysis also believes that the other cause of the accident was improper operation. After the machine started, although it was idle for 5 minutes, the machine was working under severe cold conditions. The ambient temperature was low and the diesel engine was not warmed up enough on the friction surface. After a good oil film has not been formed, the vehicle is reloaded and loaded so that the diesel engine will burn and hold the shaft. Therefore, it is recommended that the operator of the engine should increase the throttle after starting the diesel engine and turn it at idle speed for 5 minutes so that the diesel engine can run at medium speed without load to increase the temperature of the diesel engine and increase the oil supply of the oil pump (gear oil pump volume and speed Directly proportionally, to make all parts fully lubricated; when the water temperature reaches 50°C, the walking device and the working device are repeatedly operated many times until the water temperature reaches 70°C and then put into operation to reduce the wear of the parts.
According to the preliminary analysis, it may be that the battery is discharged too much and the battery capacity is not enough to enable the starter to drive the diesel engine. Therefore, the battery for the TY220 type bulldozer is replaced (the battery has a larger capacity than the TY160C), and the result is still the same. The TY160C's battery can successfully start the TY220, which can prove that the battery is not faulty. It is also believed that the starter may be faulty and cannot drive the diesel engine, but the no-load test result of the starter is normal, indicating that the starter has no fault. When using a crowbar (inserted from the starter mounting hole) to move the diesel flywheel ring gear up and down, it was found that the ring gear did not turn, indicating that the resistance of the mechanical part of the diesel engine or the diesel engine was greater than the starting force of the starter, resulting in the diesel engine not Operation. Based on this, it is believed that there may be diesel engines, power transmission boxes, and torque converters at the site of possible failure. The failure of the diesel engine may include: hard objects in the cylinder, so that the piston can not run, burning tile holding shaft; timing gear stuck and so on. Failure of the power transmission case may include: gear stuck; hydraulic pump damage and hinder the drive gear rotation. The torque converter failure may be part damage.
At the time of investigation, it was decided to remove the torque converter first. The reason was that the first time it came into contact with a Cummins diesel engine, the machine had a large difference in structure from that of a domestic machine. In the case of immature maintenance technology, inexperience, and failure to determine if it was faulty Large-disassembly and large-discharge should be avoided; the torque converter is lighter than the diesel engine, and the number of connecting parts is small, so it is easy to disassemble and facilitate maintenance. That is, after the torque converter is removed, the torque converter and the torque converter can be replaced. The previous work force transmission box is visually inspected: if the power transmission case and/or torque converter is faulty and the diesel engine fails, the diesel engine does not have to be removed. If the diesel engine has a fault and needs to be removed for maintenance, it will be removed sooner or later. Converter.
After removing the torque converter and turning the torque converter power input driving gear by hand, the torque converter operates smoothly without any jamming. It can be initially determined that the fault is not in the torque converter, and the middle of the power transmission case that is engaged with the flywheel ring gear is disassembled. Gears, which can be easily turned by hand to drive the various gears of the hydraulic pump, indicate that the fault is not an automatic transmission. At this time, the flywheel of the diesel engine still cannot be stopped. Therefore, the fault location can be judged on the diesel engine.
The engine oil was discharged and filtered. It was found that there were more debris in the oil, but the source of the debris could not be determined. The oil pan was blocked by the bulldozer beam and it was not convenient to do the demolition inspection. The diesel engine was then hung down.
During the inspection of the diesel engine, it was found that there are two half-rings in the oil pan (four rings in total, used to adjust the axial barrier of the crankshaft) and the other two pieces have also been worn, ablated, and adhered to the crankshaft; The bearing of the main bearing is severely ablated and the shaft is held so that the crankshaft can not rotate. Each bearing has a different degree of damage. Pushing the piston connecting rod group to the direction of the cylinder head can push, indicating that there is no hard object in the upper part of the piston and therefore it has not been disassembled. The cylinder head is used for inspection; there is no jam in the gears in the timing gear chamber.
Due to the large damage to the surface of the seventh main journal, the determination of grinding of the entire crankshaft after measuring the other main journals and the connecting rod journals has reduced the size by 0.25 mm. After grinding, each main bearing is reassembled and gradually tightened (one force per crankshaft, one crankshaft per revolution). When the standard torque is applied to the crankshaft, the crankshaft cannot be turned. After the inspection, the seventh main bearing is found. It was scratched, and at the same time there were two white lines on the main axis of the seventh track. The magnetic flaw test proved that it was two cracks. According to the analysis, the cracks are generated due to overheating when the bearings are burned or held on the shaft. When the bearing bracket fastening bolts are tightened to the standard torque, the journals are deformed and the cracks are increased. When the crankshaft is turned, the new bearings are scratched. The new bearings, new crankshafts (all standard) and assembled as required after the test machine, normal operation, indicating that the fault has been ruled out.
According to the analysis, the reason why this machine suffered from a serious accident with the burning of the shuffling shaft was that the oil filter was not replaced as required. It was learned afterwards that this machine only changed the oil and oil filter after the new machine was run in. , and no oil and oil filters have been replaced in the next eight months (more than 1,000 hours). In particular, after winter, no maintenance has been carried out, and the manual requires The oil and oil filter should be changed every 250 months or once every six months, and the replacement cycle can be shortened if necessary.
The analysis also believes that the other cause of the accident was improper operation. After the machine started, although it was idle for 5 minutes, the machine was working under severe cold conditions. The ambient temperature was low and the diesel engine was not warmed up enough on the friction surface. After a good oil film has not been formed, the vehicle is reloaded and loaded so that the diesel engine will burn and hold the shaft. Therefore, it is recommended that the operator of the engine should increase the throttle after starting the diesel engine and turn it at idle speed for 5 minutes so that the diesel engine can run at medium speed without load to increase the temperature of the diesel engine and increase the oil supply of the oil pump (gear oil pump volume and speed Directly proportionally, to make all parts fully lubricated; when the water temperature reaches 50°C, the walking device and the working device are repeatedly operated many times until the water temperature reaches 70°C and then put into operation to reduce the wear of the parts.
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