The basic structure and working principle of a multi-stage pump
A multi-stage pump consists primarily of a stator, rotor, bearings, and shaft seal. The rotor consists of the shaft, impellers, balancing disk, and bearing sleeves. The stator comprises the suction, intermediate, discharge, guide vanes, secondary suction section, stuffing box (casing), and bearing housing. Suction guides fluid into the pump, while the intermediate and discharge sections transport and discharge it. Guide vanes direct fluid to the next stage, enhancing its kinetic and potential energy.
Rotor Components
The heart of the multi-stage pump is the rotor, which houses the shaft, impellers, balancing disk, and sleeve. The shaft connects the motor to the impellers and transfers torque through a coupling. Impellers rotate rapidly, generating centrifugal force to propel fluid to the next stage. The balancing disk counteracts axial thrust, reducing vibrations and noise. The sleeve protects the shaft and bearings for longer service life.
Bearings
Bearing units, either rolling or sliding, support the pump shaft. Rolling bearings use grease (usually 2/3 to 3/4 of the bearing space) while sliding bearings use translucent oil, filled up to the oil level indicator. Their primary function is to bear radial and axial loads for stable shaft rotation.
Shaft Seal
A critical part of the pump, the shaft seal prevents leakage of fluid from the pump body and prevents external contaminants from entering. Common seals are mechanical and packing. Mechanical seals are preferred in high-pressure, high-speed, and high-temperature applications due to their superior sealing performance. Packing seals are suitable for low-pressure, low-speed, and normal-temperature conditions.
Working Principle
Multi-stage pumps operate by the rapid rotation of the rotor, producing centrifugal force to propel fluid to subsequent stages, increasing its energy. Continuous centrifugal action ensures efficient and stable fluid delivery. With multiple stages, these pumps offer higher head and flow capacity, ideal for long-distance, high-head pumping applications.
Multi-stage pumps play an irreplaceable role in industrial processes and daily life as essential fluid transfer equipment. Their fundamental structure encompasses the stator, rotor, bearings, and shaft seals. The rotor being the core component, the working principle relies on sequential centrifugal force for efficient and reliable fluid transport. Understanding the details of their structure and operation enhances our ability to appreciate their benefits and applications in real-world scenarios.
