The bolts connecting the middle section of the four-cylinder block to the crankcase have broken
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Why have the bolts connecting the four-cylinder block of the 4M40-197/8-48.7/5-26 compressor (Shenyuan) to the crankcase broken? The unit has been in operation for over 9,000 hours in a row.
Possible causes include fatigue fracture due to prolonged operation, bolt overloading or excessive torque during installation, material defects, etc. The fractured bolt needs to be inspected to determine the exact cause of the fracture, and all similar connections should also be checked for any identical issues in order to ensure the safe operation of the unit. .
If the bolt breaks, it’s definitely because the bolt was under stress. First, check whether there are any quality issues with the bolt itself, and then investigate the sources of stress on the bolt – such as the perpendicularity between the slide and the crankshaft, the levelness of the slide, as well as whether the bolts connecting the intermediate shaft to the crankcase are loose
The white markings on the bolts are quite distinctive; every bolt has such white markings. What role does it play? What’s the point? Has it lost its meaning? To analyze the reasons, one must first examine the fracture pattern.
Judging from the bolt markings, the bolts are not loose. Check again for piston rod impact, as well as any abnormalities in the vibration of the cylinder block and crankcase.
It’s impossible to tell whether it’s loose or not. Because all the markings are on the nuts, while there are no markings in other stationary areas. It has lost its function.
This post was last edited by CHANGBAISHI on 2025-3-16 08:02. It seems that the issue is caused by excessive torque during installation, as can be seen from the images. If it were other factors, it wouldn’t be a broken bolt. For reference.