The radial runout of the single-stage double-suction centrifugal pump is above the specified limit
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The Kaiquan water pump, a single-stage double-suction centrifugal pump (model: KQsn400―N13/470), has a rotational speed of 1450. After the bearings were replaced, the radial runout was excessive, at around 120, while the axial runout was 85. It was disassembled and reassembled several times, but the problem wasn’t resolved. The motor is fine, and the coupling alignment meets the standards. I hope the experts here can help solve it
Please check: (1) Is the bearing cover properly installed? (2) Is the bearing properly installed? (3) Is the bearing model correct? (4) Is the impeller clogged with scale?
Check the direction of the high and low points of the radial runout at the roots of the two bearings. It can be determined whether the bearing seat is out of alignment or the shaft is bent.
1. Perform dynamic balancing. 2. Ensure that all gaps are within spec. 3. Analyze the simple spectrum to determine which frequency is high, and take appropriate action accordingly.
Is the crankshaft runout beyond the limit? Are you measuring the shaft diameter or the outer diameter of the impeller? Radial runout of 120 – what does that even mean? I’m not familiar with the Kaichuan model; is this a cantilever pump?
Since repeated disassembly and assembly doesn’t solve the problem, you can only proceed step by step and use the process of elimination. The rotor is removed, and the spindle is tested for runout separately; the outer diameter and end face of the impeller are measured, and the bearing area is carefully inspected for any issues. Problems with half coupler installation, and so on.
Check step by step: shaft bending, degree of vibration, impeller, inter-stage sleeves, guide sleeves, as well as balance discs, balance drums, balance pipes, and so on
Your vibration meter reading is clearly wrong – is it 8.5 or 85? What is the concept of 85? First, perform dynamic balancing, check the clearance of the bearing caps, and examine the alignment of the components. For a single-stage double-suction pump, it should have a mid-plane separation – that is, it can be cut horizontally, with the upper and lower covers being separable. In such cases, the upper and lower covers need to be tightened first. Use a steel tape measure to determine the inner diameter of the bearing housing, and then measure the outer diameter of the new bearings. The fit between these components must not be too tight, otherwise turning the pump by hand will be difficult and there will be significant vibration ； If it is a bearing shell, use the lead pressing method. Additionally, what is the inner diameter at the impeller, and what is the diameter at the shaft? Determine how many degrees of clearance there are I once repaired a boiler feed pump: new bearings were installed and everything was aligned properly, but the vibration level was high. It was later found that there were 5-6 clearances between the impeller and the shaft, which did not meet the standards. A new impeller was purchased, one with 3 or fewer clearances, and finally everything worked properly
Whether the bearings are in good condition, if there are any issues with the impeller, measurement of the shaft’s bending degree, whether the pump was started in accordance with the procedures, and whether the balance pipes are blocked