Analysis And Countermeasures For The Increased Power Consumption Of Centrifugal Pumps in Sewage Treatment Equipment

Jan 05, 2025

What is a centrifugal pump
Centrifugal pumps work by utilizing the rotation of impellers to cause centrifugal motion in water. Before starting the water pump, it is necessary to fill the pump casing and suction pipe with water, and then start the motor to drive the impeller and water to rotate at high speed. The water undergoes centrifugal motion and is thrown towards the outer edge of the impeller, flowing into the pressure water pipeline of the water pump through the flow channel of the snail shaped pump casing.

The basic structure of a centrifugal pump consists of six parts: impeller, pump body, pump shaft, bearings, sealing ring, and packing box.
Cause analysis
1. The pump matching is unreasonable. The pressure and displacement of the modified or replaced pump have increased compared to the original pump, while the power of the electric motor is too small;
2. The outlet valve of the pump is opened too wide, the pump pressure is too low, the pump displacement exceeds the specified value on the nameplate too much, and deviates too much from the working point;
3. The packing is pressed too tightly;
4. The power supply voltage is too low and the current exceeds the rated value;
5. The motor or pump is severely misaligned and vibrates severely;
6. Severe friction between the rotor and stator components inside the pump;
7. The rotor of the electric motor moves and is not in the correct position, causing the journal step to rub against the end face of the bearing or the coupling to rub against the oil seal cover;
8. The buffer and shock-absorbing rubber ring of the coupling is too tight, causing the motor coupling to rub against the bearing cover due to the forward movement of the pump;
9. The pump balance plate did not open, resulting in severe grinding and overheating of the balance return pipe;
10. The radial clearance of the pressure relief sleeve or balance plate is too small, the deflection is too large, and it wears out during operation;
11. When the pump is started, serious internal faults occur, such as the detachment of the mouth ring and liner, or insufficient clearance in the fit;
12. The pump shaft has poor rigidity and is bent and deformed.
Three processing methods
There are roughly three countermeasures for the power loss of centrifugal pumps:
1. According to the on-site situation, take corresponding measures in a timely manner to deal with it
① Contact the power supply unit and adjust the power supply voltage to the specified range;
② Adjust the opening degree of the outlet valve to operate at the normal operating point;
③ Properly control the pump pressure and displacement to reduce the operating current of the motor;
④ Adjust the tightness of the packing gland.
2. If the above measures cannot be eliminated, the pump should be stopped for inspection and treatment
① Emptying again and draining the air inside the pump;
② Check and adjust the pressure of the lubricating oil circuit, repair or replace the bearing shell;
③ Replace the damping rubber ring of the coupling;
④ Repair or replace the balance plate;
⑤ Perform three maintenance operations, repair and replace damaged parts;
⑥ Cooperate with a professional team to handle motor malfunctions.
3. Provide suggestions and recommendations to the superior production management department and design unit to improve the mismatch of pump units
① Replace the electric motor;
② Downgrading or cutting the impeller.