Repair of Short Blade Fracture of Hydraulic Coupling Pump Wheel

In the dismantling inspection, it is often found that cracks of different lengths and lengths occur in the turbine vane of the turbo coupling, while the long vanes do not have cracks. This is because only one end of the short blade is welded to the pump body, and there is no fixed point at the top end and the outer end. As a result, short cracks are easily generated in the short blade during operation.

1, the main reason

(1) Foreign mechanical impurities penetrate the filter into the bearing of the fluid coupling. The filter is blocked by impurities, so that the bearing is not lubricated and damaged, causing vibration of the fluid coupling. In severe cases, bending of the shaft is caused and the shaft is bent. Strong vibration, blade damage caused by moving and static friction.

(2) The thickness of the steel plate does not meet the design requirements; the surface roughness is poor, and the tool marks are left, which leads to the stress concentration caused by the poor contact of the twisted blade; when the blade is welded, the current is too large to make the weld joint undercut or slag, or Weld seam height is not enough; welding joints of the blade often occur when the ultra-temperature quenching phenomenon, so that the material strength decreased, or make the blade local excessive stress, so that the pump blade cracks.

(3) Material failure or misuse of materials. The material of the blade is unqualified. After long-term operation, it is prone to fatigue cracks and expands.

(4) With the cyclical changes of operating load, rotational speed, oil flow, pressure and temperature, the oil flow will produce fatigue cracks under the action of two vibrations with radial blades for a long time. Overloading operation increases the working stress of the blade, causing premature damage to the blade. 2, improvement measures (1) welding cracks and stiffeners. Grind and weld the cracks of the short blades, then weld the stiffeners to the heads of all short blades in the center of the right ring and weld them with the long blades (see the attached drawing). After the first round of welding, the entire circle is welded. The reinforcing ribs are φ6mm metal rods. After the short blades are fixed, their rigidity is increased, the self-excited vibration and the torsional vibration of the short blades are reduced in operation, and the bending stress is reduced, so that no fatigue cracks will occur again.

(2) Improve the processing quality of parts. Before the blade welding, all the blade pitches should be calibrated. After the blade spot welding is fixed, it must be calibrated again to ensure the accuracy of the blade spacing and radial position and reduce the vibration caused by blade imbalance. The welding process is as follows:

(1) Segmented welding is adopted to prevent local overheat deformation of the welding part of the blade and avoid hot cracking.

2 When the local clearance of the weld is too large, the tip will be trimmed to the specified size. It is strictly forbidden to fill the gap in the gap.

3 Bevel size should be reduced metal filling to ensure welding quality, reduce welding stress and deformation. 4Welding waves on the weld metal surface should be uniform and free of cracks to prevent imperfections such as unconvergence, overflow, burn-through, unfilled and pinholes, slag inclusions, and biting meat along the edges or corners. After the welding is completed, stress relief treatment should be performed to prevent deformation. When assembling the pump wheel and turbine, check the verticality of the pump wheel and the turbine on both sides of the wheel end face, and whether the motor and the fan pair are on a center line. When installing the fluid coupling, the center of the fluid coupling must be 0.15 to 0.25 mm lower than the center of the motor shaft or fan shaft to eliminate the effect of temperature rise. After the pump wheel of the fluid coupling is equipped with stiffeners, the performance of its work and adjustment is not changed after the use of the reinforcing ribs, the movement is flexible, the adjustment process is smooth, and the vibration condition is basically eliminated.