There are six 24-inch split case circulating water pumps in this project, installed in the open air. The pump nameplate parameters are:

Q=3000m3/h, H=70m, N=960r/m (actual speed reaches 990r/m)

Equipped with motor power 800kW

The flanges at both ends of the rubber expansion joint are connected to the pipes respectively, and the flanges at both ends themselves are not rigidly connected with long bolts.

After thesplit case pumpis installed, debugging begins one by one. The following situations occur during debugging:

1.  Both the pump base and the cement-fixed buttress of the discharge pipe are displaced. The direction of displacement is as shown in the schematic diagram of the device: the pump moves to the right, and the fixed buttress moves to the left. The cement seats of several pump buttresses cracked due to displacement.

2.  The pressure gauge reading reaches 0.8MPa before the valve is opened, and is about 0.65MPa after the valve is partially opened. The opening of the electric butterfly valve is about 15%. The temperature rise and vibration amplitude of the bearing parts are normal.

3.  After stopping the pump, check the alignment of the couplings. It is found that the two couplings of the machine and pump are misaligned greatly. According to the inspection by the installer, the most serious misalignment is pump #1 (misalignment 1.6mm) and pump #5 (misalignment). 3mm), 6# pump (staggered by 2mm), other pumps also have tens of wires of misalignment.

4.  After adjusting the alignment, when restarting the vehicle, the user and the installation company used a dial indicator to measure the displacement of the pump foot. The maximum was 0.37mm. There was rebound after the pump was stopped, but the pump foot position could not be restored.

The broken shaft accident occurred on pump #5. Before the shaft of the 5# pump broke, it ran intermittently 3-4 times, and the total running time was about 60 hours. After the last drive, the axle broke during operation until the next night. The broken shaft is located at the recess of the driving end bearing positioning shoulder, and the cross section is slightly inclined to the center of the shaft.

Analysis of the cause of the accident: The shaft breaking accident occurred on the 5# pump. There may be problems with the quality of the shaft itself or external factors.

1. The shaft of the 5# pump is broken. It cannot be ruled out that there are quality problems with the 5# pump shaft. These problems may be defects in the shaft material itself, or may be caused by the stress concentration caused by the irregular arc processing of the 5# pump shaft undercut groove. This is the reason why the 5# pump shaft is broken. Axis causes personality issues.

2.  The broken shaft of the 5# pump is related to the displacement of the pump caused by external force. Under the action of external force, the left and right misalignment of the 5# pump coupling is the largest. This external force is generated due to the tension generated by the water pressure on the discharge pipe (this tension F when P2=0.7MPa:

F=0.7×10.2×(πd2)÷4=0.7×10.2×(π×802)÷4=35.9T, when the valve is closed, P2=0.8MPa, at this time F=0.8×10.2×(π×802 )÷4=41T), such a large pulling force cannot be withstood by the stiffness of the rubber pipe wall, and it must extend to the left and right. In this way, the force is transmitted to the right to the pump, causing it to displacement, and to the left to the cement pier, causing it to If the buttress is stronger and does not collapse, the displacement of the pump to the right will be greater. Facts have shown that if the cement pier of the 5# pump is not cracked, the displacement of the 5# pump will be greater. Therefore, after the stop, the left and right misalignment of the coupling of the 5# pump will be the largest (public account: Pump Butler).

3.  Because the stiffness of the rubber pipe wall cannot withstand the huge water thrust and is axially elongated, the pump outlet is subjected to a huge external thrust (the inlet and outlet flanges of the pump cannot withstand the external force of the pipeline), causing the pump body to shift and the coupling to dislocate. , the two shafts of the machine and split case pump run non-concentrically, which is an external factor that causes the shaft of the 5# pump to break.

Solution: Rigidly connect the tire segments with long screws, and allow the discharge pipe to stretch freely. Displacement and shaft breakage problems will no longer occur.