What Do We Need To Know About Centrifugal Pumps? (3)

Jun 20, 2025

1. What are the reasons for abnormal heating of centrifugal pumps during operation?

Heating is a manifestation of the conversion of mechanical energy into thermal energy. Common causes of abnormal heating in pumps include:
Heat accompanied by noise is usually caused by damage to the bearing ball isolation frame.
The bearing sleeve in the bearing box is loose, and the front and rear covers are loose, causing heat due to friction.
The bearing hole is too large, causing the outer ring of the bearing to loosen.
There are foreign objects inside the pump body.
The large vibration of the rotor causes wear on the sealing ring.
Pump evacuation or excessive pump load.
The rotor is unbalanced.
Too much or too little lubricating oil and unqualified oil quality.

2. What are the reasons for centrifugal pump vibration?

The rotor is unbalanced.
The pump shaft and motor are not aligned, and the coupling rubber ring is aging.
Excessive wear of bearings or sealing rings can cause rotor eccentricity.
Pump evacuation or gas inside the pump.
The suction pressure is too low, causing the liquid to vaporize or approach vaporization.
The axial thrust increases, causing axial misalignment.
Improper lubrication of bearings and packing leads to excessive wear.
Bearing wear or damage.
Localized blockage of impeller or vibration of external accessory pipelines.
Excessive or insufficient lubricating oil (grease).
The foundation stiffness of the pump is insufficient, and the bolts are loose.

3. What are the standards for centrifugal pump vibration and bearing temperature?

The vibration standard for centrifugal pumps is:
The speed is less than 1500vpm and the vibration is less than 0.09mm.
Speed of 1500~3000vpm, vibration less than 0.06mm.
The temperature standard for bearings is: sliding bearings are less than 65 ℃, and rolling bearings are less than 70 ℃.

4. What is the appropriate amount of cooling water to turn on when the pump is running normally?

When the pump is working normally, the optimal size for opening the cooling water is around 40 ℃ for the drainage temperature. At this point, touching the discharged water with your hands may cause some temperature, and the cooling effect is optimal. Especially for the cooling water of the end face seal, it should not be opened too much in winter to prevent the sealing rings of the dynamic and static rings from hardening due to low water temperature, losing elasticity and causing seal failure.

5. What are the phenomena when the centrifugal pump is evacuated?

When the running pump starts to empty, it will suddenly make noise and vibration, accompanied by a decrease in pressure, flow rate, and current. When the evacuation is severe, the pump will experience strong vibration, the pressure will return to zero, and there will be no liquid ejected from the pump.