Sudden overcurrent in the centrifugal pump
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I’ve been driving for four years, and this phenomenon has never occurred. A/B units, one in use and one as backup. ①The motor’s rated current is 40.4, with a power of 22 kW. Single-unit operation 19 (normal). ②The outlet valve is not open; only the return flow is active, with a current of 44. Outlet fully open, current 46. (Abnormal! ) ③ The pump is normal, with the bearings exhibiting good horizontal and vertical vibration levels. The GE value is normal, and centering with respect to the heart is OK. ④Replace the shaft, bearings, and packing seal with those of the same specification motor. There is still overcurrent, as shown in ②. ⑤The outlet check valve was found to be in good condition, and there are no issues with the inlet pipeline. ⑥Motor internal resistance is normal; insulation check shows no issues. ⑤ The operating current of the adjacent unit is 34, with the outlet fully open. So far, only the blades have not been replaced; everything else that could be replaced has been replaced. Where is the problem?
Flowserve centrifugal pumps.
How about the barring gear? What is the medium, and are there any impurities?
The traffic is actually a little bit lower than that of the backup server
The turning of the shaft is quite smooth; the medium is 99% water
Motor overload, elimination method. Unplug the device and test the motor separately; if there are no issues, then consider the pump. When checking a pump for any signs of wear, pay attention to the rings at the front and back of the impeller, as well as the seals between the pump cover and the shaft sleeve, the moving ring and the sealing chamber, the dynamic and static rings of the mechanical seal, the positioning pins between the shaft and the static ring, and the area between the shaft and the labyrinth seal or oil seal. If no signs of wear are found, then consider hydraulic factors – such as whether the gaps between the rings are too large, or whether there is any backflow within the pump body and cover. Pay special attention to the throat section of the pump body. Has the impeller balance clearance increased?
Motor overload is mainly related to two aspects: first, an increase in mechanical resistance, which involves checking for any points of friction; second, a decrease in the efficiency of converting work into kinetic energy, which requires examining the gaps in various parts of the impeller to determine where the energy loss occurs.
Check it; since the problem persists even after replacing the motor, there must be friction inside the pump. Of course, first measure the current at the site to see if it’s a problem with the current transmitter.
However, manual cranking was smooth with no sticking. Semi-open impeller; no signs of friction were observed upon inspection. There are also no signs of friction inside the pump casing, and all the gaps in the impeller that needed adjustment have been adjusted. The main issue is that it’s illogical – there’s no significant change in the current at the switch outlet, with a difference of only 1A.