Vibration at the drive end of a single-stage double-suction centrifugal pump
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Hello, teacher. I have 3 Kaiquan single-stage double-suction centrifugal pumps with dual supports. During maintenance, the impellers, ring gears, and bearings were replaced; the material of the impellers, which was cast iron, was changed to 1CR13, and the same change was made to the ring gears. After replacing the impellers and ring gears, the dynamic balance and alignment were within standard limits. However, the vibration level at the drive end exceeds the acceptable range when the pumps are in operation. The inlet filters have been removed, and for the 3 pumps, 2 of them show a vibration level of 10–12 mm/s, while the third one shows 7–8 mm/s. Under normal operating conditions, the pressure at the outlet is 5 kilograms per square centimeter; when the outlet valve is closed and the pressure rises to 6–7 kilograms per square centimeter, the vibration level decreases by 1–2 mm/s. The inlet pipeline passes through a elbow, with a straight section before the pump of about 2D in length; the vibration level was not this high before the impeller was replaced. Help analyze it
Check the anchor bolts to see if they are level with the foundation and whether there are any issues related to stress. Also, the pump needs to be tested within its operating conditions. During installation, ensure that the connectors are clean and properly installed. For reference.
This post was last edited by 3983596_FPPZ on 2020-6-29 08:25. Please refer to the pump performance curve to determine the actual rated parameters of the pump; it is not sufficient to rely solely on the outlet pressure. Due to the influence of back pressure, the outlet pressure does not accurately reflect the operating parameters of the pump. The flow rate should be used as the reference, and the changes in vibration when adjusting the valve illustrate this point. Also, the balance condition of this new impeller itself should be taken into consideration. Replacing the impeller may result in it not matching the original one, leading to changes in performance parameters
1. Check whether the sizes of the old and new impellers are the same. 2. Check the maintenance records. 3 Check whether the pump and motor are raised off their bases.
Assuming there is no difference in the size of the impellers before and after replacement, 1 check whether the anchor bolts have been tightened properly. 2 For a double-suction pump, when replacing the impeller, two sets of bearings need to be removed; determine whether any damage to these bearings occurred due to excessive force during removal. 3 Check whether the gap between the ring and the impeller is too large because maximum tolerances were used during manufacturing. Leave this task to the manufacturer – I don’t have the necessary data. If the installation or removal was carried out by the customer without the manufacturer’s staff present, it will be difficult to determine who is responsible