Analysis of the failure causes of an in-use magnetic pump
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There is a 3KW coupling-type insulated magnetic pump in use, with a flow rate of 3 cubic meters, a head of 30 meters, and an operating temperature of around 200 degrees. Since the medium tends to crystallize, the pipes and the pump itself are insulated using high-temperature steam. There are no pressure gauges or flow measurement devices on the pump’s outlet pipeline; the flow rate is adjusted primarily to meet the production requirements and to prevent the motor from exceeding its current limits. The pump operated normally at first, and after maintenance, it was able to fill with fluid and maintain its insulation properly. There was no sticking when attempting to rotate the pump shaft. However, when the pump was started, the motor exceeded its current limit, and the same issue occurred even when the valve was closed. Trying again yielded the same result: when the outlet valve was opened wider, the current far exceeded the motor’s rated value, but the flow rate was still sufficient to meet the production needs. What could be the reasons for this phenomenon?
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It used to not exceed the current limit during operation, but now it exceeds that limit even with the outlet valve closed, which indicates that there is something abnormal operating inside the pump: (1) Check whether the sliding bearings are worn and whether there is any friction in the rotor components; it would be best to disassemble the pump for an inspection. (2) Or, due to poor heat retention, crystallization occurs in the liquid inside the pump chamber, preventing the pump from operating properly. The operation of insulated magnetic pumps is very important; it is advisable to install pressure gauges at both the inlet and outlet, and a flow meter at the outlet. It is necessary to regularly record the pump’s operating conditions in order to determine whether it is functioning properly
Is it a problem with the medium! ~Check the process to see if there are any changes in the medium Such as viscosity, temperature. . .
Our company also has magnetic pumps, and the main problem is that the substances flowing through them can crystallize, leading to wear on the pump body and the impeller’s ring, which in turn prevents proper pressure generation
This post was last edited by Be cautious sh on 2011-5-15 at 13:35. If it is a substance that crystallizes, it can cause wear to the pump body and the impeller’s ring, or it may enter the drum chamber and cause damage there. Also, if the viscosity is not selected correctly during the selection process, it can have an impact as well.
The installation is not proper; the pump can be rotated without any jamming when it’s at rest, but excessive current is generated during operation. When power is applied, axial movement occurs, and friction between the impeller or coupling leads to excessive current. Checking the installation position will resolve this issue.
The shaft is out of alignment, causing friction between the impeller and the pump. Surprisingly, there were no abnormalities when turning the engine. A bit dizzy:。 Let’s take another look to see if there are any issues with the selection.
The biggest difference of a magnetic pump is that it has a part that relies on magnetic force for transmission (it is a contactless form of transmission). So I think even if the pump rotor is stuck, the turning gear should still be able to rotate it! So there must be a problem with the pump. Since the poster mentioned that it has just been overhauled, it can be assumed that the components inside are in good condition; therefore, crystallization is still the most likely explanation. The reason might be that the insulation is not adequate, resulting in the temperature not reaching the required level. All the previous inquiries were based on the assumption that the motor functions properly when tested individually.
Reply to 1# hcb081995: It’s possible that the back cover of the impeller is loose; there’s no problem when the machine is stopped, but when it’s in operation, the axial force causes the impeller to rub against the housing
The motor worked fine when tested individually, and its magnetism was found to be in order; even if it got stuck, due to the contactless transmission mechanism, the shaft should not have been able to rotate. Upon disassembly, it was discovered that there was friction between the axial direction of the impeller and that of the pump casing, and the axial force generated caused the impeller to rub against the housing