How to repair the bending of the main shaft of the split pump
The repair method of the bending of the main shaft of the split pump mainly depends on the bending degree, length and material properties of the pump shaft. Generally speaking, the repair methods can be divided into two categories: cold straightening method and hot straightening method. The following is a detailed analysis of these two methods:
1. Cold straightening method
Cold straightening method is usually used in occasions where the pump shaft is short and the bending amount is not large. Specific methods include screw jack straightening, press straightening and torsion bar runout straightening.
Screw jack straightening:
Applicable conditions: when the pump shaft diameter d≤5mm.
Operation steps: Use a straight screw jack for straightening. During the straightening process, it is necessary to visually confirm the first press position of the pump shaft, and after the second press, slightly bend the axis of the pump shaft in the opposite direction of the original bend for about 15 minutes. Keep this state for 20 minutes and then release the pressure. If the axis of the pump shaft is straight by visual inspection, a straightness check is required to confirm.
Protective measures: When fixing, a certain thickness of cotton yarn or copper pad is needed to protect the diameter or stress point of the shaft to avoid damage to the contact surface.
Press straightening:
Applicable conditions: When the pump shaft diameter d>55mm.
Operation steps: Place the pump shaft on the press, the convex surface of the pump shaft should face up, and the two ends should be fixed to avoid slipping out. When fixing, the two ends of the fixed shaft diameter and the pressure point of the press should be separated by a certain thickness of cotton yarn. Then, press the convex tip with the press and push it down until the pump shaft is straightened.
Torsion bar runout straightening:
Applicable conditions: When the pump shaft diameter is large.
Operation steps: When twisting the pump shaft, the concave surface of the pump shaft should face up, and the two ends should be pressed down with a tensioning device, and then the pump shaft should be knocked with a torsion bar weighing 1-2kg to achieve straightening.
2. Thermal straightening method
The thermal straightening method is usually used in occasions where the pump shaft is long and has a large bend. Specific methods include local heating straightening, internal stress relaxation straightening, and mechanical heating straightening.
Local heating straightening:
Operation steps: Place the pump shaft on the two protruding upward support frames, wrap the maximum bend of the pump shaft with wet asbestos cloth, and then heat it with a blowtorch or gas welding. The heating temperature needs to be controlled, usually about 100℃ lower than the critical temperature of the pump shaft.
Internal stress relaxation straightening:
Operation steps: Place the pump shaft on two support frames with the convex side facing up, use the induction coil to heat the bending position of the pump shaft, and apply a certain force. Load downward on the convex surface until the pump shaft is straightened. When the axis of the pump shaft is visually checked to be straight, the load needs to be removed. The straightened pump shaft should be annealed to eliminate internal stress.
Mechanical heating straightening:
Operation steps: For a smaller diameter pump shaft, it can be fixed on two support frames with the convex side facing up, and then an external load is applied to press the bent shaft downward. Heat on the concave surface to achieve pump shaft straightening.
3. Precautions
When straightening the pump shaft, the bending amount of the pump shaft should be determined first, and the appropriate straightening method should be selected according to the material, diameter and bending degree of the pump shaft.
During the straightening process, the heating temperature and heating time need to be controlled to avoid excessive thermal damage to the pump shaft.
After the straightening is completed, the pump shaft should be annealed to eliminate internal stress and improve the stability and service life of the pump shaft.
During the entire repair process, attention should be paid to safe operation and maintenance to ensure the safety of the staff and the normal operation of the equipment.
