What to know about centrifugal pumps

The core principle of the centrifugal pump is to use the rotation of the impeller to generate centrifugal force, transfer energy to the liquid, and make it sucked in axially and discharged radially.

 

1. Core Principle

Use the rotation of the impeller to generate centrifugal force, transfer energy to the liquid, so that it is sucked in from the axial direction and discharged radially.

2. Main Structure

- Impeller: core component, pushing the liquid to do work.

- Pump casing (volute): collects liquid and converts kinetic energy into pressure energy.

- Shaft seal device: prevents liquid leakage (such as mechanical seal, packing seal).

- Suction/discharge pipeline: connection system, including valves, filters and other accessories.

3. Classification method

- By the number of impellers: single-stage pump (single impeller), multi-stage pump (multiple impellers in series).

- By suction method: single-suction pump (single-side liquid inlet), double-suction pump (double-side liquid inlet).

- By purpose: clean water pump, sewage pump, chemical pump, oil pump, etc.

4. Performance parameters

- Flow rate (Q): liquid volume transported per unit time (m³/h).

- Head (H): energy provided by the pump to unit weight of liquid (m).

- Power and efficiency: shaft power (motor input power), effective power (liquid energy power), efficiency is the ratio of the two.

- Speed ​​(n): impeller revolutions per minute (r/min), affecting flow and head.

- Net Positive Suction Head (NPSH): key parameter to avoid cavitation caused by liquid vaporization.

V. Working characteristics

- Characteristic curves: flow-head, flow-power, flow-efficiency curves, reflecting the operating law of the pump.

- Working point: the intersection of the pump characteristic curve and the pipeline characteristic curve, which determines the actual operating parameters.

- Adjustment method: adjust the flow through the valve (simple but high energy consumption), or frequency conversion speed regulation (energy saving but high cost).

VI. Installation and maintenance

- Installation points: the suction pipe is short and straight to avoid air leakage; the pump shaft is horizontal and coaxial with the motor.

- Start and stop: fill the pump with air before starting and close the outlet valve; when stopping, close the outlet valve first and then turn off the power.

- Common faults:

- Cavitation: produces noise, vibration, damages the impeller, and the suction pressure must be guaranteed.

- Leakage: The shaft seal is worn or improperly installed, and the seal needs to be replaced.

- Bearing overheating: insufficient lubrication or shaft misalignment, need to add oil or adjust the alignment.

VII. Selection points

- Clarify the characteristics of the medium (viscosity, corrosiveness, solid content, etc.).

- Determine the flow rate and head requirements (leave 10%~20% margin).

- Consider the installation conditions (suction height, ambient temperature) and energy-saving requirements.

- Give priority to efficient and reliable brands and models.

VIII. Application scenarios

Widely used in chemical, petroleum, water supply and drainage, agricultural irrigation, electricity and other fields to transport clean or impure liquids.

If you need in-depth analysis or troubleshooting of specific scenarios, please explain further!