Fault of increased current and reduced flow in a horizontal single-stage centrifugal pump
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The n-butane reflux pump, model ZE40-3400, has been in use for half a year. Over the past two weeks, it was observed that when pump A was operating, the flow rate was less than 12 m³/h, and the current consumption was 60 A, which is 50% higher than the normal operating current level. The current consumption when the outlet was closed at no load was 19 A, which is normal. Pump B is operating normally, with a flow rate of 15 and a current of 40A. Inspections of the rotor, tests of the motor without load, and inspections of the pump all revealed no issues. Inspections of the bearings, mechanical seals, alignment, lip gap, shaft runout gap, and gear turning showed no abnormalities. I still guessed it might be a problem with the overcurrent component, but the medium isn’t very corrosive either; it’s really puzzling.
Overload and overcurrent in centrifugal pumps are generally caused by: 1. A change in the medium, from a liquid with low density to one with high density. 2. The outlet valve is opened too wide, or the back pressure at the outlet is lost; as a result, on the performance curve, the head is very low, which leads to an excessive flow rate and overcurrent. 3. Abnormal friction in the mechanical components, such as damage to the bearings of the impeller seal or friction with stationary parts. 4. The wear gap of the mouth ring is too large, resulting in mixing of media and high pressure mixing with low pressure. Currently, plans are to purchase the rotor components first and then carry out replacement tests
Based on the description, it seems best to include a flow diagram; could it be that there is a leak in the check valve within the flow process? Also, after checking, the unit “12m³/h” should be written as m3/h; I’m not sure what the extra “&sup” characters mean. Could you please explain this? Thank you :)
By replacing the impeller and turning down the outer diameter of its three blades from 360 to 345, all problems were resolved.
The impeller was made smaller to solve the problem – what is the principle behind this?
What exactly is the reason? With the same process and the same equipment, why is pump B fine while this one requires its impeller to be turned?
Keep the pump body stationary, replace the impellers of pumps A and B, and then try again.
Thanks for sharing, coming in to learn a bit*