Basic structure and troubleshooting of centrifugal pumps

Basic structure and troubleshooting of centrifugal pumps

Centrifugal pumps work by rotating the impeller to make water centrifugal. Before starting the water pump, the pump casing and the suction pipe must be filled with water, and then the motor is started so that the pump shaft drives the impeller and water to rotate at high speed. The water undergoes centrifugal motion and is thrown to the outer edge of the impeller, flowing into the water pressure pipeline of the water pump through the flow channel of the volute pump casing.

1. Types of centrifugal pumps Single-stage centrifugal pumps, multi-stage centrifugal pumps, vertical pumps, shielded centrifugal pumps, horizontal centrifugal pumps

2. Basic structure of centrifugal pumps The basic structure of a centrifugal pump is composed of eight parts, namely: impeller, pump body, pump cover, water retaining ring, pump shaft, bearing, sealing ring, stuffing box, and axial force balancing device.

1. The impeller is the core part of the centrifugal pump, which has a high speed and a large output force.

2. The pump body is also called the pump casing, which is the main body of the water pump. It plays a supporting and fixing role and is connected to the bracket for mounting the bearing.

3. The function of the pump shaft is to connect the motor with the coupling and transmit the torque of the motor to the impeller, so it is the main component for transmitting mechanical energy.

4. The sealing ring is also called the leakage reduction ring.

5. The stuffing box is mainly composed of stuffing, which prevents the water flow in the pump from flowing out and the outside air from entering the pump. Always keep the vacuum in the water pump! When the pump shaft and the stuffing generate heat due to friction, the water seal pipe must be used to inject water into the water seal ring to cool the stuffing!

6. Axial force balancing device. During the operation of the centrifugal pump, since the liquid enters the impeller at low pressure and flows out at high pressure, the pressure on both sides of the impeller is unequal, generating an axial thrust pointing to the inlet direction, which will cause the rotor to move axially, causing wear and vibration. Therefore, an axial thrust bearing should be set to balance the axial force.

3. Troubleshooting of single-stage centrifugal pumps

1. Single-stage centrifugal pump failure: slow water filling of the pump Reason: Large gap between the front liner and the impeller, the outlet pipe cannot seal the air, and the discharge is full.

Solution: adjust the gap, adjust the water outlet pipe, and install a vacuum device.

2. Single-stage centrifugal pump failure: low water outlet pressure and low flow rate Reason: There is air in the pump, the gap between the impeller and the front liner is large, the clutch is not closed tightly, and the impeller or liner is worn.

Solution: empty the gas in the pump, adjust the gap, adjust the gap of the clutch friction plate, and replace the impeller or liner.

3. Single-stage centrifugal pump failure: the pump wears quickly Reason: poor construction environment (large particles), long conveying distance, and long water inlet pipeline. Solution: replace the sand field, add a booster unit, shorten the length of the water inlet pipe to reduce cavitation.

4. Single-stage centrifugal pump failure: water pump vibration Reason: The pump shaft is not concentric with the diesel engine (or motor), the impeller is unbalanced, and the bearing is damaged.

Solution: adjust the concentricity, balance the impeller, and replace the bearing.

5. Single-stage centrifugal pump failure: The pump does not absorb water. Reasons: Insufficient water injection, air in the pump cannot be discharged, air leakage in the suction pipe, and large gap between the front liner and the impeller.

Solution: Continue to inject water, check whether the pipeline is leaking, and adjust the gap between the impeller and the front liner.

6. Single-stage centrifugal pump failure: The impeller shaft neck wears quickly. Reasons: Low head of the high-pressure water pump, misaligned packing, and the pump shaft and the rear cover are not concentric.

Solution: Replace a high-pressure pump with a higher head than the single-stage centrifugal pump, replace the packing, and adjust the concentricity.