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Overhaul Methods for Crankshaft of Diesel Generator Set

Dec. 23, 2019

How to overhaul crankshaft of diesel generator set? Starlight diesel genset supplier answers for you.

Crankshaft is the most important part of diesel generator set. Due to the complex stress and working conditions of crankshaft, the sliding speed of each friction surface is very high, and the heat dissipation condition is poor. Therefore crankshaft journals is easily wear, bent and distorted, even cracks or breaks, etc. Once crankshaft has fault, it will affect the working efficiency of diesel generators. So overhaul is a very important maintenance step. 

Overhaul and treatment method of crankshaft crack

The cracks on the crankshaft are very fine, which can not be easily seen by the naked eye. The magnetic flaw detector can be used for inspection.

When conditions are not available, the simple way is:

First immerse the crankshaft in kerosene for a moment, take it out and wipe it, then sprinkle it with white powder. Then knock on the crankshaft arm in sections with a hammer. Due to the vibration, the kerosene in the crack seeps out, making the white powder show the yellow oil stains. The crack position and length can be determined.

 crankshaft of diesel generator set

Overhaul and treatment of crankshaft deformation

The obvious part of crankshaft bending deformation is the middle main journal. If the crankshaft continues to be used after bending and deformation, it will cause crankshaft connecting rod structure fast wear and tear, even make crankshaft cracked and broken. Therefore in the repair process of diesel engine, inspection must be done.

When inspecting, both ends of the crankshaft shall be supported on the V-shaped frame on the platform, and the contact of the dial indicator shall be put against the middle main journal to avoid the oil hole. Slowly turn round the crankshaft for one revolution, observe the maximum and minimum values indicated on the dial indicator. One half of the difference between the two values is the straightness of the crankshaft. If the crankshaft has partial wear, the amount of partial wear should be subtracted. When the straightness is within the range of 0.05 ~ 0.10mm, we can combine with journal grinding to make corrections.

The test method of crankshaft angle of torsion

Support the crankshaft horizontally on the platform, make the two journals of the same connecting rod at the top dead center. Then use a dial indicator to measure the height difference between the front and rear connecting rod journals at their highest points. The greater the difference, the greater the torsional angle.

The main journal and connecting rod journal of crankshaft will inevitably produce wear and tear in work, and the wear is uneven. Its main performance is the roundness of the journal, cylindricity exceeding the standard value and strain. The most worn part of connecting rod journal is generally on the inner side of each journal, that is, the side close to the crankshaft centerline. However, the parts that are worn into a cone are generally on the side where impurities are attached to the lubricating oil passage and on the parts with large stress. The worn parts of crankshaft main journal are different according to the strengthening degree of engine, the number of cylinders, the length of crankshaft and the balance weight. And wear is more uniform relative to the connecting rod journal. The practice shows that the wear of connecting rod journal is faster than that of main journal. However, consequences of journal wear is more serious than that of connecting rod journal.

Inspection and treatment methods: find out the worn parts according to the wear law of each journal. Roundness and cylindricity can be measured by external micrometer to determine the repair level and grinding dimension of crankshaft.

Hope this article is helpful to you. Starlight Power is a manufacturer of diesel generators and has focused on high quality product for more than 43 years. We have a very professional sales team and after-sales service team. If you are interested, please contact us by email sales@dieselgeneratortech.com, we will work with you. 

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