The crankshaft is an essential component in a diesel generator set. Due to the complex force and working conditions, the sliding speed of each friction surface of the crankshaft is very high, and the heat dissipation conditions are poor. Therefore, not only is the journal of the crankshaft prone to wear, but it may also undergo bending and twisting deformation, and even crack or break. Once a malfunction occurs, it will seriously affect the working efficiency of the diesel generator set. Therefore, inspecting and repairing the crankshaft is a very important maintenance step.
I. Inspection and Treatment Methods for Crankshaft Cracks
The cracks in the crankshaft are very fine and not easily detectable by the naked eye. They can be inspected with a magnetic flaw detector. When conditions do not permit, a simple inspection method is the oil immersion hammer strike method: First, immerse the crankshaft in kerosene for a moment, then take it out, wipe it clean, sprinkle white powder on it, and then strike the crankshaft arm in sections with a hand hammer. Due to the vibration, the kerosene in the crack seeps out, causing the white powder to show oil stains and yellow line marks. Based on this, the location and length of the crack can be determined.
Ii. Inspection and Treatment Methods for Crankshaft Deformation
The part where the bending deformation of the crankshaft is reflected more obviously is the middle main journal. If the crankshaft is used after being bent and deformed, it will accelerate the wear of the crankshaft connecting rod mechanism and even cause cracks and fractures in the crankshaft. Therefore, in engine repair, this must be inspected. When conducting the inspection, the two ends of the crankshaft should be supported on the V-shaped frame on the platform. The contact of the dial indicator should be placed against the middle main journal, avoiding the oil hole. Slowly rotate the crankshaft once and observe the rated value and the minimum value indicated on the dial indicator. Half of the difference between the two values is the straightness of the crankshaft. If there is eccentric wear on the crankshaft, the amount of eccentric wear should be reduced. When the straightness is within the range of 0.05-0.10mm, it can be corrected in combination with journal grinding. The inspection method for the torsion Angle of the crankshaft is as follows: Horizontally support the crankshaft on a platform so that the two journal posts of the connecting rods in the same position are at the top dead center. Then, use a measuring instrument to measure the height difference of the front and rear connecting rod journal posts at their high points. The greater the difference, the greater the torsion Angle.
Three, the main journal and connecting rod journal of the crankshaft are inevitably subject to wear during operation, and the wear is uneven. The main manifestations are that the roundness and cylindricity of the journal exceed the standard values and scratches. The rated part of the wear of the connecting rod journal is generally on the inner surface of each journal, that is, the side close to the centerline of the crankshaft, causing the journal to lose its roundness. The parts that are worn into a conical shape are generally on the side where impurities adhere to the lubricating oil passage and the parts that are subjected to greater force. The wear area of the crankshaft main journal varies depending on the degree of engine strengthening, the number of cylinders, the length of the crankshaft, and the counterweight of the balance weights. Moreover, the wear is more uniform compared to that of the connecting rod journal. Practice shows that the wear of the connecting rod journal is faster than that of the main shaft journal. However, the consequences caused by the wear of the main shaft journal are more serious than those of the connecting rod journal. Inspection and treatment methods. According to the wear law of each journal, the worn parts can be found. The roundness and cylindricity can be measured by an outer diameter micrometer to determine the repair level and grinding dimensions of the crankshaft.
The three faults mentioned above are the common faults of the crankshaft of diesel generator sets. Therefore, inspection and repair are very important and users cannot ignore them.
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Post time: Jun-09-2025