Hermetic Canned Motor Pump Structural Features

Hemetek is an internationally renowned brand of magnetic drive pumps and canned motor pumps. Its canned motor pumps are known for their high integration, absolute leak-free operation, and high reliability, making them particularly suitable for applications in chemical and petrochemical industries where safety requirements are extremely high.

Their core structural features can be summarized as "integrated, fully enclosed, and internally circulating," as detailed below:

I. Core Structure Overview

Unlike traditional pumps (with shaft seals) or magnetic drive pumps (with isolation sleeves), Hemetek canned motor pumps adopt a "pump and motor integrated, fully shielded" design:

No shaft seal/zero leakage: There is no mechanical seal whatsoever, structurally eliminating any leakage points.

Special Motor: A thin-walled shielding sleeve isolates the motor rotor and stator, completely isolating the motor stator windings from the pumped medium.

Bearings Built into the Medium: The bearings of both the pump and motor rely on the pumped medium itself for lubrication and cooling.

II. Key Components and Structural Features

Canned Motor

Shielding Sleeve: Core component. Between the rotor (rotating component) and the stator (stationary windings), a thin-walled metal sleeve (usually a corrosion-resistant alloy) completely seals and isolates them. This allows the rotor to be immersed in the medium, while the stator windings are completely isolated and protected from the medium.

Rotor Chamber: The motor rotor and pump impeller share the same main shaft and are located in a chamber filled with the pumped medium.

Bearing System
Material: Typically made of self-lubricating, corrosion-resistant, and wear-resistant materials such as graphite, SiC (silicon carbide), or hard alloys.

Lubrication and Cooling: Rely entirely on the pumped medium itself. A portion of the medium circulates, flowing through the bearing clearances, serving to lubricate and remove heat. This is crucial for the long-term stable operation of the canned motor pump.

Circulation Loop
Internal Circulation System: This is the "lifeline" of the canned motor pump. A forced circulation path is designed inside the pump:
A small stream of medium is drawn from the high-pressure area of ​​the pump (usually the pump chamber).

The medium flows sequentially through the rear bearing → motor rotor chamber (cooling the motor) → front bearing.

Finally, it returns to the low-pressure inlet of the pump, completing a closed loop.

Functions: Cools the motor, lubricates bearings, and prevents the medium from vaporizing within the motor cavity.

Monitoring System (Advanced Configuration)

Bearing Wear Monitor: A key feature of high-end brands like Hemetek. It monitors the axial displacement of the rotor shaft using electrical or mechanical sensors (such as shaft displacement probes), providing early warning before bearing wear exceeds limits, enabling predictive maintenance and preventing sudden equipment failure.

Temperature and Pressure Sensors: Monitor motor winding temperature, circulation loop pressure, etc.

Overall Structure

Compact and Integrated: The pump and motor are a rigid unit, requiring no coupling or alignment, resulting in an extremely compact structure and space-saving design.

Fully Enclosed Housing: Typically, there is only one static sealing point (such as a housing flange gasket), achieving complete leak-free operation outside this point.

III. Summary of Structural Advantages

Structural Features

Core Advantages

Applicable Scenarios

No shaft seal, fully shielded

Absolutely no leakage, highest safety, meeting the most stringent environmental and safety standards.

Highly toxic, flammable, explosive, highly corrosive, expensive, or radioactive media.

Self-lubricating/cooling medium

No external cooling water or lubrication system required, simplifying auxiliary piping.

Suitable for applications requiring high system cleanliness or where on-site water sources are inconvenient.

Integrated design

Compact structure, no alignment required, low vibration, low noise, and easy installation.

Suitable for applications with limited space or requiring low maintenance.

Graphite/SiC bearings

Corrosion-resistant and wear-resistant, especially with some tolerance under dry running conditions (short-term).

Suitable for applications with poor media lubricity or where short-term dry running may occur.

Bearing wear monitoring

Enables condition monitoring and predictive maintenance, improving operational reliability and preventing unexpected downtime.

Critical processes with continuous production and high maintenance costs.

IV. Usage Precautions
Due to its special structure, canned motor pumps also have specific usage requirements:

Dry running is strictly prohibited: Even short-term dry running will rapidly damage the bearings and shielding due to loss of media lubrication and cooling.

The media must be clean: Solid particles will severely abrade the bearings and circulation channels. Clean media or a pre-filter is typically required.

Avoid cavitation: Cavitation damages the lubricating film and causes vibration, harming bearings and shielding.

Adequate purging is essential before startup: Ensure the motor chamber and circulation loop are filled with liquid.

In summary, the essence of Hemetek canned motor pumps lies in integrating the pump and motor into a self-sustaining, completely sealed unit powered by the media. This sacrifices slight efficiency for unparalleled sealing safety and operational reliability, making it one of the ultimate solutions for handling hazardous and valuable media.