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The Analysis of Crankshaft Cracks and Fractures of Diesel Generator Sets

Jul. 12, 2021

Today we will introduce the reasons, inspection and repair of the crankshaft cracks and breaks of diesel generators:

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1. Causes of crankshaft cracks and breaks of diesel generator sets

The reason is except that the crankshaft bend, the twisting is substantially the same, as well as the following aspects:

1) When the optical grinding journal, the diesel generator set is not allowed to maintain a certain fillet (crank) connection (generally requiring a journal of 1 to 3 mm) to cause stress concentration Crankshaft break.

2) The gap of the bearing is too large or alloy falls off, causing an increase in impact load.

3) Fatigue injury after the crankshaft works.

4) Diesel generator set crankshafts often operate in critical speed.

5) The cylinder body deformation, the crank bearings are not positive, and each crank bearing seat hole is not in an axis.

6) The lubrication oil is not smooth, the crankshaft is in a semi-drying state, causing a crank crack.

7) The crankshaft of diesel generator group is poor, or defects in manufacturing.

8) The balance of the crankshaft is destroyed, and the crankshaft is greatly impulted to crack the crankshaft fatigue.


2. The crankshaft crack crack cracks and breaks of diesel generator

Crankshaft cracks of diesel generator groups have occurred in the binding of the connecting rod shaft to the end or crankshaft arm and the crank journal. The check method as follow:

1) Magnetic detection method. Check with a magnetic flap, first use the magnetic detection of the diesel generator group to magnetize the magnetic flap, and then use the iron powder to be inspected. At the same time, the crankshaft is gently hit by a small hammer. At this time, pay attention to observation, if there is crack, there is a clear crack line in the middle of the iron powder.

2) Hammer method. First remove the oil attached to the surface of the diesel generator set, then remove the entire crankshaft with kerosene or diesel, and then remove the crankshaft clean, finally support the two ends of the crankshaft on the wooden frame, gently Tap each crankshaft arm. If a "," (coherent sharp metal sound), the crankshaft has no cracks; such as a "wave, wave" (inconsistency, short dumb metal sound), indicating that the crankshaft has cracks. It is then easy to produce a crack in this vicinity, and carefully observe with a vaginal or with a magnifying glass. If the oil stains are discovered or a black line, it is the crack.

3) Powder method. After washing the diesel generator crankshaft with kerosene or diesel, it applies a layer of talcum powder on the surface of the crankshaft, and then slightly magnetically magnetically axled with a small hammer. If there is crack in the crankshaft, the oil will bleed from the interior of the crack, the tonal powder of the crankshaft becomes tan. And then you will find the the crack.

4) Lime milk method. Wash the diesel generator crankshaft in hot oil (oil) for about 2h, allowing oil into the crack, after removing the dried, spray the "lime emulsion" into the crankshaft to dry (lime emulsion is a cleaner chalk and Alcohol's mixture of alcohol is 1: 10 to 1: 12), or heat the spray of the crankshaft to 70 to 80 ° C with gas welding flame. At this time, the chalk absorbs the oil stored in the crack, which is dark, showing the shape of the crack.


3. Diesel generator set crankshaft crack cracks, broken repairs

If the crankshaft of the diesel generator group has cracks or breaks, you could repair with the "welding" method. The briefly described process as below.

1) Prepare before welding. First put the diesel generator crankshaft in the alkali water and clean, remove oil, and then use the chisel to church the "U" slot along the crack surface. The groove is deep in the crack. The bottom of the groove is circular, and the width of the groove needs to be determined according to the depth length and shape of the crack. Correction is then performed so that the bending penders of the crankshaft do not exceed the specified range. Finally, mounting the crankshaft on the autocratic welder or is mounted on the cylinder and matches the crankshaft and the cylinder or cylinder bodies. The bearing cover is then tightened, and the crankshaft is avoided in the welding process. If the weld is broken, it is necessary to find a central selection according to the scar of the crankshaft, and the welding is first solder on both sides of the slit, and then soldered after the crack is not soldered.

2) Welding. Before repair welding, gas welding flame first heated to 350 ~ 450 ℃ the welding site, and then seam welding performed diameter mild steel welding of 3 ~ 4mm. Welding, to the welding method by using (vertical movement of electrode cracking), and after the completion of each layer of solder, welding slag removal immediately, then welded layer.

3) Finishing after welding. After welding, the welding repair should first repair flat chisel, and drill through the oil passage, welding cracks test, there is no diesel generator crankshaft bending. Grinding is then performed at the weld by the grinding machine, so that the surface is smooth and flat, and heat treatment can be performed on the working surface of the diesel generator set crankshaft to increase the abrasion resistance of the working surface.


More information pls email to sales@dieselgeneratortech.com, your feedback will be get prompt reply.

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