Problems that occur when using shielded pumps
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When using a canned motor pump, the values of radial or vertical vibration can sometimes vary significantly, such as 1.2 mm/s, 2.9 mm/s, 3.6 mm/s, 2.4 mm/s, 1.9 mm/s. In short, large fluctuations in vibration values are observed during data collection. What could be the reason for this?
Have there been any changes in the operating flow rate and head of the pump?
How does an online bearing monitor display information? There are many reasons for vibration in shielded pumps. It will be necessary to describe in detail the operating conditions of your pump in order to be able to give you an accurate assessment
The amplitude is too high; there is a risk of wear on the sliding bearings, shaft sleeves, rotor, and shielding sleeves. Check whether the temperatures of the front and rear bearings are within the standard range; if you’re not confident, disassemble the pump for inspection.
1 It can only be determined by disassembly. 2. For mechanical reasons, the vibration level usually only increases gradually and irreversibly. If there are fluctuations or drops, investigate the cause of the operation. Since the 3 reasons have not been identified, continued operation will cause mechanical damage, resulting in the need for major repairs.
Check if there are any changes in flow rate, pressure, and current? There are many reasons for vibration. The structure of shielded pumps is relatively simple, but they require high standards in terms of process operation as well as maintenance and assembly!
If the rear bearing pointer is in the green zone, no action is needed; fluctuations may be caused by changes in material flow. If the pointer is in the yellow zone, it is necessary to take action by stopping the pump for inspection. Remove the cover of the rear graphite bearing, measure the wear level of the graphite bearing as well as that of the thrust plate, and also use a dial indicator to determine whether the front end is worn out!
1. Shielded pumps are quite delicate; it is not recommended to switch them regularly as is done with centrifugal pumps. Each such switch results in friction between the moving and stationary parts, which reduces the lifespan of the thrust plate by at least 3 months； 2. The bearing monitor can only detect radial vibration; it is unable to assess the axial condition of the thrust plate, and wear of the thrust plate can be determined by an increase in current ； 3. The issue of radial vibration fluctuations is related to the inlet filter and to low flow rates ； Arrange maintenance for this vibration variation as soon as possible ； 4. At the beginning of operation, the shielded electric pump requires a smaller filter screen to trap rust and other debris in the pipelines, and the time taken to clean the filter screen should be kept within half an hour.
It’s more of a problem with the graphite bearings, I guess.