Magnetically Coupled Gear Pumps: An Optimal Solution for Efficient Fluid Transfer

What are Magnetically Coupled Gear Pumps?

Unlike traditional external gear pumps that rely on a motor shaft directly coupled to a driving gear, magnetically coupled gear pumps use magnetic force to transfer torque. This eliminates the need for a shaft passing through a seal, which is a common source of wear and eventual leakage in direct drive pumps. By utilizing magnetic coupling, these pumps create a hermetic seal while still enabling motor-to-gear coupling, significantly extending the pump’s operational lifespan. All Diener precision pumps feature magnetic coupling, offering our clients longlasting pump solutions of superior quality.

How Traditional Magnetic Couplings Work

In traditional magnetic couplings, a magnet is connected to the pump’s internal driving gear. This magnet is typically encased in metal or plastic to prevent fluid contact and to allow coupling with the driving gear. A thin metal barrier separates the pumped fluid from the external atmosphere, ensuring that the fluid remains isolated. On the other side of the barrier, an external magnet attached to the motor couples with the internal magnet. The strength of this coupling depends on the type of magnet, with rare earth metals offering stronger magnetic bonds.

Precision is key in traditional magnetic couplings, as the strength of the magnetic bond diminishes rapidly with distance. Therefore, precise machining is required to ensure that the magnets are positioned as close together as possible, maximizing coupling efficiency and ensuring smooth, quiet operation.

Advantages of Magnetic Coupling

• Eliminates the need for a sliding seal, extending the life of the pump and reducing frictional drag.
• Flexibility in motor choice, allowing any motor type or size to be used.
• Thermal isolation, preventing the motor from transferring heat to the pumped fluid.
• Strong magnetic coupling, especially when both magnets are made from rare earth alloys.

Disadvantages

• The addition of magnetic coupling components increases the overall size of the pump.
• Extra magnets and brackets add to the cost of the pump assembly.

The Evolution: Direct Magnetic Drive

Building on the traditional magnetic couplings, direct magnetic drives have emerged as a more compact and cost-effective solution. In this design, the pump’s internal magnet serves as the rotor for a brushless DC (BLDC) motor, eliminating the need for a separate motor and external magnet. This configuration offers a fully hermetic, magnetically driven pump with a reduced number of components and a lower manufacturing cost.

To achieve the necessary performance in direct magnetic drives, rare earth metal alloys are typically used for the internal magnet, while the fluid barrier remains similar to that in traditional magnetic couplings.

Advantages of Direct Magnetic Drive

• Extended pump life due to the elimination of the sliding seal and reduced friction.
• Compact design, making it ideal for installations in tight spaces.
• Cost-effective manufacturing, thanks to fewer components.
• Long operational lifespan, as there are no motor ball bearings to wear out.

Disadvantages

• There can be power and input limitations, depending on the pump supplier’s portfolio.
• Heat-producing coils are positioned closer to the pump, potentially adding heat to the fluid—though this effect is generally minimal and only relevant in small, closed-loop systems.

Magnetically coupled gear pumps offer significant benefits over traditional designs, particularly in applications where long life, reliability, and a compact footprint are essential. Whether using traditional magnetic coupling or the more advanced direct magnetic drive, these pumps provide a hermetic sealing solution that extends operational life and reduces maintenance needs.