Assembly of fasteners for diesel generator set engine

At present, although some mechanics and repairmen have obtained driver's licenses or junior repairman level certificates, their understanding of the construction principles and maintenance knowledge of machinery is still very superficial. During maintenance, it is common to use a wrench to tighten fasteners or to strike fasteners with force by hand. As a result, the installed diesel engine frequently malfunctions during operation, and some even cause serious accidents. The following are the installation precautions for important fasteners on diesel engines, in order to draw the attention of engine operators and repair personnel.
1. Cylinder head nut. When tightening the cylinder head nut, it should be gradually tightened to the specified torque in several times, and the principle of starting in the middle, then on both sides, and crossing diagonally should be followed. When dismantling the cylinder, it should also be gradually loosened in the prescribed order. If the cylinder head nuts are tightened unevenly or unevenly, it can cause the cylinder head plane to warp and deform. If the nut is tightened too tightly, the bolt will stretch and deform, and the body and threads will also be damaged. If the nut is not tightened enough, it can cause air, water, and oil leakage in the cylinder, and the high-temperature gas inside the cylinder can also burn out the cylinder gasket.
2. Flywheel nut. The flywheel and crankshaft of the S195 diesel engine are connected through a conical surface and a flat key. During installation, the flywheel nut must be tightened and locked with a thrust washer at the folded edge. If the flywheel nut is not tightened, the diesel engine will produce a knocking sound during operation, and in severe cases, it can damage the crankshaft cone surface, cut the keyway, twist the crankshaft, and cause serious accidents. Also, it should be noted that the corner of the thrust washer can only be bent once.
3. Connecting rod bolts. Connecting rod bolts made of high-quality steel can withstand significant impact forces during operation and cannot be replaced with ordinary bolts. When tightening, the torque should be uniform. The two connecting rod bolts should be tightened gradually to the specified torque in several turns, and finally locked with galvanized iron wire. If the tightening torque of the connecting rod bolt is too large, it will cause the bolt to stretch, deform or even break, leading to cylinder ramming accidents; If the tightening torque of the connecting rod bolt is too small, the clearance between the bearing shells will increase, resulting in knocking sound and impact load during operation, and even accidents such as burning the bearing and holding the shaft and breaking the connecting rod bolt may occur.
4. Main bearing bolts. The installation accuracy of the main bearing should be ensured and it should not be loose. When tightening the main bearing bolts (for a fully supported four cylinder engine crankshaft), the 5 main bearings should be tightened evenly to the specified torque in 2-3 times, starting from the middle, followed by 2, 4, and then 1, 5. Every time it is tightened, the crankshaft should also be checked for normal rotation. The hazards caused by excessive or insufficient tightening torque of main bearing bolts are basically the same as those caused by excessive or insufficient tightening torque of connecting rod bolts.
5. Balance block bolts. When installing the balance block bolts, they should be tightened gradually to the specified torque in several steps according to the sequence. The balance block should be reinstalled in its original position, otherwise it will lose its balancing function.
6. Rocker arm seat nut. For rocker arm seat nuts, regular inspections should be carried out in conjunction with maintenance during use. If the nut of the rocker arm seat becomes loose, it will increase the valve clearance, delay the opening and closing of the valve, shorten the duration of valve opening, cause insufficient gas supply, unclean exhaust, decreased power, and increased fuel consumption in the diesel engine.
　　
7. Fuel injector locking nut. When installing the fuel injector, its locking nut should be tightened to the specified torque. At the same time, it is best to tighten it several times, not all at once. If the locking nut of the fuel injector is tightened too tightly, it will cause deformation of the locking nut and also easily cause the needle valve to get stuck; If tightened too loosely, it can cause fuel injector leakage, decrease in injection pressure, poor atomization, and increased fuel consumption.
8. Tighten the oil outlet valve seat. When installing the outlet valve seat of the fuel injection pump, the specified torque should also be applied. If the tight seat of the oil outlet valve is tightened too tightly, it will cause deformation of the plunger sleeve, block the plunger in the sleeve, and cause early wear of the plunger coupling, decreased sealing performance, and insufficient power; If the tight seat of the oil outlet valve is too loose, it will cause oil leakage in the fuel injection pump, prevent the establishment of oil pressure, delay the fuel supply time, reduce the fuel supply, and seriously affect the engine performance.
9. Fuel injector pressure plate nut. When installing the fuel injector assembly on the cylinder head of a diesel engine, in addition to paying attention to removing dirt such as carbon deposits in the installation seat of the fuel injector assembly, installing the pressure plate of the fuel injector assembly in reverse, and ensuring that the thickness of the steel gasket is appropriate and cannot be missed, attention should also be paid to the tightening torque of the nut of the pressure plate of the fuel injector assembly. If the tightening torque of the pressure plate nut is too high, it will cause deformation of the fuel injector valve body, resulting in the fuel injector nozzle getting stuck and the diesel engine not working; If the tightening torque is too small, the fuel injector will leak, causing insufficient cylinder pressure, making it difficult to start the diesel engine, and high-temperature gas will also rush out and burn out the fuel injector.
In addition, when installing the high-pressure oil pipe joint on the distribution pump slide rotor and distribution pump housing, the spring should also be tightened according to the specified torque.