How to repair and inspect the crankshaft of a diesel generator set

The crankshaft is the ultimate component in diesel generator sets. Due to its complex force and working conditions, the sliding speed of each friction surface is high, and the heat dissipation conditions are poor. Therefore, the crankshaft is not only prone to wear on the journal, but also prone to bending, twisting, deformation, and even cracking or breaking. Once a malfunction occurs, it will seriously affect the efficiency of the diesel generator set, so inspecting and repairing the crankshaft is a very important maintenance step. So how to inspect and repair it? Here is a brief introduction.

1) Inspection and treatment methods for crankshaft cracks

The cracks on the crankshaft are fine and difficult to detect with the naked eye. A magnetic flaw detector can be used for inspection. In situations where conditions are not met, the simplest inspection method is the immersion hammer method: first immerse the crankshaft in kerosene for a moment, take it out and wipe it clean, sprinkle white powder, and then use a hammer to segment it on the crankshaft arm_ When knocked up, due to vibration, kerosene seeps out of the crack, causing the white powder to show oil stains and yellow lines. Based on this, the position and length of the crack can be determined.

2) Inspection and processing methods for crankshaft deformation

The most obvious reflection of crankshaft bending deformation is at the middle main journal. If the crankshaft is bent and deformed and continues to be used, it will accelerate the wear of the crankshaft connecting rod mechanism, and even cause cracks and fractures in the crankshaft. Therefore, in engine repairs, this must be inspected. During inspection, both ends of the crankshaft should be supported on the platform's V_ On the rack, use the contact of a dial gauge to press against the middle main journal and avoid the oil hole. Slowly rotate the crankshaft for one revolution and observe the maximum and minimum values indicated on the dial gauge. One 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 subtracted. When the straightness is within the range of 0.05~0.10mm, it can be corrected by combining with journal grinding.

The inspection method for crankshaft torsion angle is to support the crankshaft horizontally on a platform, so that the two journals of the same position connecting rod are at the top dead center, and then use a hundred meters to measure the height difference between the front and rear connecting rod journals at their highest points. The larger the difference, the greater the torsion angle.

3) The main journal and connecting rod journal of the crankshaft inevitably experience wear during operation, and the wear is uneven, mainly manifested by roundness, cylindricity exceeding the standard value, and strain on the journal. The maximum wear of the connecting rod journal is generally on the inner surface of each journal, which is on the side near the centerline of the crankshaft, causing the journal to lose its roundness; The parts that wear into a cone are generally on the side where impurities attach to the lubricating oil passage and on the parts that are subjected to high force. Crankshaft main journal_ The wear parts of the engine vary according to the degree of engine strengthening, number of cylinders, crankshaft length, and balance weight, and the wear relative to the connecting rod journal is more uniform. Practice has shown that the wear of the connecting rod journal is faster than that of the main shaft journal, but the consequences of the main shaft journal wear are more serious than those of the connecting rod journal wear.

Inspection and handling methods. Based on the wear pattern of each journal, identify the worn area and measure its roundness and cylindricity using an outer diameter micrometer to determine the repair level and grinding size of the crankshaft.