pump shaft damage causes

The role of the pump shaft is to transfer power to the impeller and support the impeller in a certain position with the help of bearings. Do you know the main forms of pump shaft damage? How did it come about?

There are two main reasons for the damage of pump shaft

1、 Shaft bending

Shaft bending often occurs in deep well pumps and multi-stage pumps, which have large shaft length diameter ratio.

The causes of pump shaft bending are: rotor dynamic unbalance is too large, rotor vibration, pump foundation levelness out of tolerance. For horizontal multi-stage pumps, the sagging of midspan caused by untimely turning, deformation caused by temperature difference between upper and lower parts of rotors, and vibration caused by excessive dynamic unbalance and centering deviation of rotors.

The main methods to solve the bending of shaft are cold calibration, hot calibration and mixed calibration.

2、 Wear and tear

Eccentric wear is often accompanied by shaft bending. In addition, wear caused by loose inner ring or bearing damage often occurs in bearing shaft diameter.

Inspection steps of pump shaft:

(1) Surface inspection: clean the pump shaft with kerosene, polish it with sandpaper, and check whether there is groove mark on the surface.

(2) Check the bending of the shaft: for the bent shaft, clamping on the lathe is the most convenient measurement, and the accuracy is relatively high. Rolling bearing bracket or V-shaped iron support can also be used for measurement, but the levelness and axial positioning of the shaft must be ensured to prevent the displacement.

① Determine the measurement position of the shaft. Take the installation half coupling, bearing, impeller and other parts as the measuring points.

② Divide the measuring parts of pump shaft into four equal parts or more even parts.

③ Install a dial indicator on the measuring section, and the measuring head of the indicator should be perpendicular to the axis.

④ Rotate the shaft slowly for one circle in the same direction, measure and record the data of each point in turn.

⑤ Comprehensive analysis is made according to the deviation value of each measurement section. Using half of the difference between the two directions of 180 ° symmetry, the corresponding shaft bending diagram is drawn. For example, the straightness deviation in the direction of 0 ° and 180 ° of measuring point I is = 0.12.

⑥ Analyze the maximum bending position and orientation.

Repair method after damaged pump shaft:

1. Journal hook and repair after wear

Vacuum pump maintenance manufacturers recommend using sliding bearing shaft journal. Due to poor lubrication or iron chips and sand particles brought in by lubricating oil, the pump shaft journal is scratched or grinded, and the journal at rubber guide bearing is worn. Generally, copper plating and stainless steel plating are used for repair, and then the standard diameter is processed by using the vehicle or grinding method.

2. Repair of pump shaft bending

For the pump shaft with smaller diameter, copper sheet can be padded at the bending position and straightened by hammering; for the pump shaft with larger diameter and less serious bending, screw straightener can be used for straightening.

3. Repair of shaft thread

When the thread damage at the end of the pump shaft is light, the damaged thread can be repaired with a mixed file and then continue to be used. If the damage is serious, first turn the pump shaft end small, then press on a bushing, screw out the thread on the bushing; or weld the pump shaft end thread with electric and gas welding, and then turn the thread.