Centrifugal pump failure
Thread Content
The fluoroplastic alloy centrifugal pump we use causes the power switch to trip after it starts operating; however, it functions properly when the valve is set at 50% opening. We have also used devices of this model in the past without such problems; what could be the cause? We would appreciate it if everyone could offer their opinions or suggestions. Thank you
Has the air switch tripped? That shouldn’t be the case. If it’s the thermal relay that trips, it means the load is too heavy and the motor current exceeds the rated value. First, try running the machine without a load to see if there’s anything stuck or causing excessive weight
Check the gap of the sealing ring; a large gap can cause excessive current and lead to tripping. It could also be a problem with the motor. I recently encountered such an issue with an inverter-driven motor – it would trip once a certain current level was reached. I always thought it was a problem with the pump, but after swapping the two motors, I discovered the actual cause.
That’s a very professional question; we seem to have encountered it once as well!
It’s probably a problem with the motor; it shuts down when overloaded and experiences excessive current.
Some motors encounter the problem of tripping due to overcurrent; it is necessary to check whether the motor and the outlet pipes meet the required standards!
The valve was opened too much, causing a trip due to the excess current, right?
Follow the principle of starting with the easier tasks; first, measure whether the current exceeds the motor’s rated value. If it does not exceed the rated value, then it is a problem with the electrical components, and these components should be inspected, adjusted, or replaced (such as relays or circuit breakers). If the current does exceed the rated value, then there is a problem with the unit itself. First, test the motor individually to check whether its no-load current falls within the specified range. If it is normal, then examine the alignment of the coupling as well as the installation of the pump itself (issues such as excessive misalignment of the coupling, poor flexibility when rotating the pump shaft, or too small gaps between rotating parts like the impeller and stationary parts like the pump casing or flanges may exist). If there are such problems, realign them and try running the pump again; if it still shuts down, then check whether the process medium meets the requirements of the pump. If the density of the medium is too high, it can cause the current to be excessively high. If the medium is fine, then consider that the pump model is not suitable for the given process, and in that case, either replace the motor with one of a larger capacity or reduce the outer diameter of the pump’s impeller (this requires some calculations) to resolve the issue.
A trip indicates current overload; first, use the flow and pressure data to determine whether the motor selection is appropriate.
Check the seal, turn the pump to see its ease of rotation, and address the pump selection issues mentioned by other users as well. Is it caused by excessive stress?
If the valve is too small to a certain extent, it will cause increased noise and vibration in the centrifugal pump, and the performance of the pump will exhibit instability. Moreover, operating a centrifugal pump with its valves closed for an extended period can cause the temperature of the liquid inside the pump to rise. When the pump operates at a low flow rate or with no flow at all while still being closed, the water circulates rapidly within the pump chamber due to the high-speed rotation of the impeller; this causes the pump body’s temperature to rise sharply, as does the outlet pressure. In mild cases, this leads to leakage and damage to the seals, while in severe cases it can result in the pump exploding. The motor current also increases, and excessive current can cause the motor to burn out.