Based on years of experience, our company has found that some staff members, although they have relevant certificates or certain maintenance experience, still have a very superficial understanding of the construction principles and maintenance knowledge of machinery. It often occurs that fasteners are forcefully turned with a wrench or struck hard with a hand hammer during maintenance. As a result, the installed diesel engines frequently broke down during operation, and some even caused serious accidents. The following is a description of the installation precautions for important fasteners on diesel engines, so as to draw the attention of the majority of engine operators and maintenance personnel.
Cylinder head nut. When tightening the cylinder head nuts, they should be gradually tightened in several steps to the specified torque, and the principle of starting from the middle, then the sides, and crossing diagonally should be followed. When removing the cylinder, it should also be loosened step by step in the prescribed sequence. If the cylinder head nuts are tightened unevenly or unevenly, it will cause the cylinder head plane to warp and deform. If the nut is tightened too much, the bolt will stretch and deform, and the body and threads will also be damaged. If the nut is not tightened enough, it will cause air leakage, water leakage and oil leakage in the cylinder, and the high-temperature gas inside the cylinder will also burn out the cylinder gasket.
2. Flywheel nut. For instance, the flywheel and crankshaft of the S195 diesel engine are connected through conical surfaces and flat keys. When installing, the flywheel nut must be tightened and locked with the folded edge of the thrust washer. If the flywheel nut is not tightened properly, when the diesel engine is in operation, it will produce knocking sounds. In severe cases, it may damage the conical surface of the crankshaft, cut the keyway, and twist the crankshaft, causing serious accidents. In addition, it should be noted that the corner of the thrust washer can only be bent once.
3. Connecting rod bolts. The connecting rod bolts processed from high-quality steel are subject to great impact forces during operation and cannot be replaced by ordinary bolts. When tightening, the torque should be uniform. The two connecting rod bolts should be tightened step by step in several turns to reach the specified torque, and then locked with galvanized iron wire. If the tightening torque of the connecting rod bolt is too large, it will cause the bolt to stretch and deform or even break, leading to a cylinder damage accident. If the tightening torque of the connecting rod bolt is too small, the clearance of the bearing bush will increase, resulting in knocking sounds and impact loads during operation. In severe cases, accidents such as bearing bush burning, shaft seizing, and connecting rod bolt breakage may occur.
4. Main bearing bolts. The installation accuracy of the main bearing should be ensured and it should not become loose. When tightening the main bearing bolts (for four-cylinder crankshafts with full support), the five main shaft bearings should be tightened evenly in 2 to 3 steps in the order of first the middle, then the second and fourth, and finally the first and fifth, until the specified torque is reached. After each tightening, it is also necessary to check whether the crankshaft rotates normally. The hazards caused by excessive or insufficient tightening torque of the main bearing bolts are basically the same as those caused by excessive or insufficient tightening torque of the connecting rod bolts.
5. Balance block bolts. When installing the balance block bolts, they should be tightened step by step in sequence and several times to the specified torque. The balance weights should be reinstalled in their original positions; otherwise, they will lose their balancing function.
6. Rocker arm seat nut. For the rocker arm seat nut, regular and periodic inspections should be carried out in combination with maintenance during use. If the rocker arm seat nut becomes loose, it will cause the valve clearance to increase, the valve opening to be delayed, the closing to be advanced, and the valve opening duration to be shortened, resulting in insufficient gas supply to the diesel engine, incomplete exhaust, reduced power, and increased fuel consumption.
7. Fuel injector lock nut. When installing the fuel injector, the lock nut should be tightened to the specified torque. At the same time, it is better to tighten it several times repeatedly rather than all at once. If the lock nut of the fuel injector is tightened too much, it will cause the lock nut to deform and also easily lead to the needle valve getting stuck. If it is tightened too loosely, it will cause oil leakage from the fuel injector, a decrease in fuel injection pressure, poor atomization and increased fuel consumption.
8. Tight seat of the oil outlet valve. When installing the tight seat of the fuel injection pump’s fuel outlet valve, it should also be done in accordance with the specified torque. If the tight seat of the oil outlet valve is tightened too much, it will cause the plunger sleeve to deform, resulting in blockage of the plunger in the sleeve and premature wear of the plunger pair, reduced sealing performance and insufficient power. If the tight seat of the fuel outlet valve is too loose, it will cause oil leakage from the fuel injection pump, fail to establish fuel pressure, delay in fuel supply time, reduce fuel supply volume, and seriously affect the working performance of the engine.
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 carbon deposits and other dirt in the fuel injector assembly installation seat, ensuring that the fuel injector assembly pressure plate is not installed in reverse, and that the thickness of the steel gasket is appropriate and not missed, it is also necessary to pay attention to the tightening torque of the fuel injector assembly pressure plate nut. If the tightening torque of the pressure plate nut is too large, it will cause the fuel injector valve body to deform, resulting in the fuel injector getting stuck and the diesel engine being unable to work. If the tightening torque is too small, the fuel injector will leak air, causing insufficient cylinder pressure, making it difficult to start the diesel engine, and the high-temperature gas will also rush out and burn out the fuel injector.
In addition, when installing the sliding vane rotor of the distribution pump and the high-pressure oil pipe joint on the distribution pump housing, it should also be done in accordance with the specified torque.
For more questions about the generator set, please call the Beidou Power team. More than ten years of professional production and sales of power generation equipment experience, more professional engineer team to serve you, choose Beidou power is to choose rest assured, welcome on-site factory inspection.
Post time: Oct-11-2025