Causes and Countermeasures of Ablation of Crankshaft

Crankshaft ablation causes and countermeasures: Ablation of the crankshaft, mainly due to the failure to form an effective lubricating film between the crankshaft journal and the bearing, resulting in direct friction between the crankshaft journal and the bearing. When the crankshaft of a diesel engine ablates, it will emit white smoke and emit an unusual sound of metal impact. It may even cause the crankshaft and the bearing to lock together and fail to rotate. Therefore, it is necessary to correctly analyze and judge the cause of the failure.

1. Poor oil quality: 1) Poor oil quality. The selected engine oil quality grade and viscosity grade are lower, or different grades of engine oil are used for blending, which causes the use performance of the engine oil to fail to meet the requirements; a large amount of dust is mixed into the engine oil during use, and the engine oil is oxidized and deteriorated due to the excessively high working temperature of the diesel engine. . The oxidatively degraded engine oil is black and dull, and the concentration is increased. Using two-fingered engine oil, the engine oil has dust and impurities. If it is found that the used oil exhibits the above phenomenon, it must be replaced in time. 2) The engine oil becomes thin. Due to the lubrication of a part of the diesel fuel injection pump using pressure lubrication, once the injection pump and the oil seal fail. The diesel oil will enter the lubricant chamber and will dilute and deteriorate the diesel engine lubricant. In addition, if the water jacket has cracks or trachoma pores, so that the cooling water seeps into the oil will also make the oil thinning. The upper parts of the diesel engine (top cylinder head, valve mechanism, cylinder head cover) can be checked for water vapour or water droplets. If it is found that the increase in the use of engine oil capacity, the concentration decreased, the viscosity decreased, and the smell of raw oil shows that the engine oil is mixed with diesel. Import pump valve

2. Insufficient oil stock and low oil pressure: Insufficient oil stock and low oil pressure will result in insufficient lubrication oil flow of the diesel engine, and thus no lubricant film formation between the diesel engine crankshaft journal and the bearing shell can be guaranteed. Check the amount of oil in the sump and the reading of the oil pressure gauge to further check for any abnormalities such as clogging or leakage in the oil line.

3, crankshaft journal and bearing gap is too large or too small: 1) crankshaft journal and bearing due to the gap is too large, resulting in lower engine oil pressure, can not form a sufficient lubricant film. 2) The gap between the crankshaft journal and the bearing bush is too small, and the oil film thickness between the crankshaft journal and the bearing bush is not enough or there is no lubricating film. When the gap is too large or too small, you can use the micrometer, cylinder table to check the journal, bearing hole, bearing size, calculate the fit clearance, can also use the feeler gauge directly with the gap.

4, the crankshaft or cylinder geometry over the poor: 1) The crankshaft radial runout greater than the difference, so that the journal and the bearing gap is small or no gap, the thickness of the lubricant film is not enough or no lubricant film. 2) The coaxiality of the main bearing bore of the cylinder block is so bad that the gap between the main journal and the bearing bush is too small or no clearance, and the thickness of the lubricant film is not enough or there is no lubricating film. 3) The verticality of the cylinder and the main bearing hole is so poor that the connecting rod journal and the main journal gap are too small or no clearance. The thickness of the lubricant film is not enough or there is no lubricating film. This phenomenon often occurs when the diesel engine is put into use for a short period of time after a new machine or overhaul. To determine the geometrically oversized parts, you can shake the crankshaft of the diesel engine with your hand crank (rotate hard), and then unload the diesel engine main bearing cap and the connecting rod bearing cover one by one and then turn the crankshaft. According to the rotating crankshaft torque size, the difference is determined to determine (but to determine the size of the super-delta, you need to disassemble the diesel engine, with a special inspection tool to determine).