Shielded (Canned Motor) Pumps: How They Work and Why They’re Essential for Safe Fluid Handling

 Shielded (Canned Motor) Pumps: How They Work and Why They’re Essential for Safe Fluid Handling

In industrial settings—such as chemical processing, pharmaceuticals, surface treatment, and advanced materials manufacturing—handling corrosive, hazardous, or flammable liquids safely is a top priority. In these applications, traditional sealed pumps often struggle to balance reliability and safety, especially when leakage is unacceptable.

This is where shielded pumps—also known as canned motor pumps—offer a structural advantage. Their unique design eliminates dynamic seals, drastically reducing leakage risks and improving operational safety.

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What Is a Shielded (Canned Motor) Pump?

A shielded pump integrates the motor and pump into a single, fully enclosed unit. Rather than having an external motor connected to a shaft with mechanical seals, the motor rotor and pump rotor are aligned inside a sealed housing (or “canned”), which keeps the process fluid completely enclosed. This eliminates the need for traditional shaft seals—commonly the weakest point in a pump system.

In essence, shielded pumps remove potential leakage paths by design.

How Does a Shielded Pump Work?

Here’s the basic principle in action:

Fully enclosed design: The motor stator is isolated outside the fluid chamber, while the rotor and impeller reside inside a pressure-tight can.

Magnetic coupling: The motor’s electromagnetic field passes through the can to drive the rotor directly.

Fluid lubrication and cooling: The pumped liquid functions as both lubricant and coolant for the internal bearings.

This means the entire rotating assembly is submerged in the process fluid and does not rely on mechanical seals to separate the motor from the liquid.

Key Structural Components

A typical shielded pump consists of:

Enclosed motor stator

Canned rotor and impeller assembly

Pressure-tight isolation sleeve (the “can”)

Bearing and support system lubricated by the process fluid

Because the fluid itself lubricates and cools the internal parts, the design simplifies maintenance and improves reliability.

Why Shielded Pumps Are Preferred for Hazardous Fluids

Shielded pumps offer several practical advantages:

✔ No mechanical seals = no dynamic leakage path

✔ Reduced maintenance and downtime

✔ Improved safety for flammable, toxic, or corrosive liquids

✔ Compact design with fewer wear components

These features make shielded pumps ideal for applications where leak prevention and operational safety outweigh marginal efficiency gains.

Common Applications

Shielded pumps are widely used in:

Acid/alkali circulation and transfer

Solvent handling and recovery

Flammable liquid transfers

High-purity chemical processing

Systems with strict environmental and safety standards

If you’re designing or upgrading a system that transports hazardous liquids, a shielded pump is often a strong candidate for achieving long-term, low-risk operation.

When to Use Shielded Pumps (and When Not)

Shielded pumps deliver benefits, but also require thoughtful selection:

🔹 Best for clean, corrosive, hazardous liquids

🔹 Not suitable for fluids with large abrasive solids

🔹 Must avoid prolonged dry running

🔹 Requires proper matching of flow, viscosity, and temperature

Good pump selection isn’t just about picking a type—it’s about matching fluid properties, system design, and operational goals.

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