Analysis of pump shaft fracture issues

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Condition of the pump shaft breakage at the site: 1. The fracture consists of two parts, old and new. 2. From the outer circumference of the cross-section, they are all old fracture traces. 3. No damage was found to the bearings or mechanical seals. 4. Cavitation can be observed on the impeller blades. 5. The coupling bolts, impeller back caps, and other connection bolts have all become loose. 6. No foreign objects were found at the entrance. Cause analysis: 1. Stress concentration exists in the material; prolonged operation caused cracks to appear in the shaft, leading to its fracture ； 2. The shaft was not properly heat-treated; no modulation treatment was carried out. 3. The material itself has internal defects. 4. Cavitation causes erosion of the impeller, leading to a loss of dynamic balance and resulting in fatigue fracture of the weak parts of the main shaft.