Structure and Working Principle of a Pumped-Space Shield

A centrifugal pump connects the pump to an electric shaft via a coupling, enabling both the pump shaft and motor to rotate simultaneously. In contrast, a canned motor pump is a seal-free design where both the pump and drive motor are enclosed within a pressure vessel filled with the fluid being pumped.

This vessel features only a static seal and utilizes a wire winding to generate a rotating magnetic field that drives the rotor. This configuration eliminates the need for traditional shaft sealing mechanisms found in conventional centrifugal pumps, ensuring complete leak prevention. The internal structure and external appearance of a canned motor pump are illustrated in Figures 2-4-1 and 2-4-2.

Working Principle and Structure of Magnetic Pump

The magnetic drive centrifugal pump (abbreviated as magnetic pump) is a novel pump that utilizes modern magnetism principles to achieve contactless torque transmission through the magnetic force of permanent magnets. Specifically, when a motor drives the outer rotor (i.e., the outer magnet assembly) to rotate, magnetic flux lines pass through the isolation sleeve under the influence of the magnetic field, driving the inner rotor (i.e., the inner magnet assembly) and impeller to rotate synchronously. Since the medium is confined within the stationary isolation sleeve, this design ensures

Since the medium is confined within the stationary isolation sleeve, this design ensures leak-free pumping, completely resolving the shaft seal leakage issue associated with mechanical-driven pumps, making it a fully sealed, leak-proof, and pollution-free industrial pump. Its internal structure and exterior appearance are shown in Figures 2-4-3 and 2-4-4. Figure 2-4-3 illustrates the internal structure of a magnetically driven pump; Figure 2-4-4 shows its external appearance.

2.4.3 Common Features and Differences Between Shielded Pumps and Magnetic Pumps

2.4.3.1 Structural Commonalities Between Shielded Pumps and Magnetic Pumps

1. All of them belong to vane-type transfer pumps.
2. No dynamic seal is required, ensuring zero leakage.

2.4.3.2 Structural Differences Between Shielded Pumps and Magnetic Pumps

1. The working components of the shielded pump—its impeller and motor—are integrated into a single unit. The motor rotor is in direct contact with the working fluid, while it is separated from the stator by a shielding sleeve. The motor features an internal circulation cooling system that provides both cooling for the motor and lubrication for the bearings.
2. The key components of a magnetic pump are a pair of interacting inner and outer magnetic cylinders. A fully sealed isolation housing is positioned between the outer and inner magnetic cylinders, completely separating them and placing the inner cylinder within the working medium. During operation, the motor transmits torque to the outer magnetic cylinder via a coupling; under the magnetic force exerted by the outer cylinder, the inner magnetic cylinder rotates under its influence, with the impeller being connected to it. Consequently, the rotation of the inner magnetic cylinder drives the impeller, thereby performing work on the medium.

2.4.4 Applications of Shielded Pumps and Magnetic Pumps

2.4.4.1 Classification and Applications of Shielded Pumps

(1) Basic Type: The medium flows from the impeller inlet to the pump outlet flange, where a self-lubricating line is formed that directs the outlet medium into the rear bearing. Through the clearance between the bearing and the rotor, the medium is then returned to the front bearing, achieving self-lubrication of the pump bearings.

This type is suitable for clean media environments with low vaporization tendencies, as shown in Figure 2-4-5 (Basic Type). (2) Reverse Circulation Type: In this shielded pump design, the flow direction of the liquid used for bearing lubrication, cooling, and motor cooling is opposite to that of the basic type. Its key advantage is reduced cavitation risk, making it particularly suitable for transporting highly volatile liquids such as liquefied petroleum gas and chloromethane, as illustrated in Figure 2-4-6.

Figure 2-4-6: Reverse-circulation type (3) High-temperature variant, typically designed for transport media with maximum temperatures up to 350°C, flow rates up to 300 m³/h, and head values up to 115 m, suitable for high-temperature liquids such as thermal oils and hot water. As shown in Figure 2-4-7: Figure 2-4-7 High-temperature variant

2.4.4.2 Applications of Magnetic Pumps

Magnetic pumps, featuring a shaftless design, operate with low noise, zero leakage, and no pollution, completely eliminating the environmental contamination issues caused by liquid leakage-induced corrosion associated with traditional mechanical shaft seal pumps. They are widely used in industrial systems such as grain and oil processing, food manufacturing, petrochemicals, and pharmaceuticals for transporting rare and valuable liquids, volatile substances, and media where sealing contamination is unacceptable—particularly for liquids containing no solid particles that are prone to leakage, flammability, or explosiveness. In food industries where stringent sealing requirements apply, magnetic pumps demonstrate exceptional safety and reliability, reducing leakage rates from traditional mechanical seals to zero, effectively preventing material waste and contamination while ensuring safe, efficient, clean, and hygienic production processes, making them highly worthy of widespread adoption and promotion.