Magnetic drive pumpss are sealless centrifugal pumps that use a coaxial magnetic coupling to transmit torque to an impeller. They are energy efficient and can circulate a variety of fluids including acids, caustics, and oils. Magnetic drive pumps (like most sealless pumps) have a higher capital cost than comparable centrifugal pumps, but offer reduced operating costs due to the lack of seal replacement, cleanup, waste, and downtime. They are particularly useful for transporting hazardous or expensive chemicals because there is no mechanical seal, eliminating the possibility of leakage or failure due to an obstruction.

Pump Operation and Classification 

All pumps are designed to operate on either a dynamic or positive displacement principle. Dynamic pumps utilize fluid momentum and velocity to generate pump pressure while  use expanding and contracting cavities to move fluids. Dynamic pumps produce a variable flow suited for generating high flow rates with low viscosity fluids, while positive displacement pumps produce a constant flow suited for producing high pressures (and low flow rates) with high viscosity fluids.

Magnetic drive pumps use magnets to generate movement. These magnets are mounted on a carrier or drive assembly and are driven by a standard electric motor. For dynamic pumps, this drive assembly typically moves an impeller; for positive displacement pumps, it moves a mechanism which expands and contracts a cavity. The drive assembly consists of two separate rings of permanent magnets. The outer set moves the inner set via a rotating magnetic field, which in turn drives the pumping mechanism

Most magnetic drive pumps are centrifugal pumps (a subset of dynamic pumps), although there are also positive displacement magnetic drive pumps (like the gear pump pictured above). Centrifugal pumps utilize one or more impellers to generate fluid velocity. To learn more about how centrifugal pumps function, visit the page on GlobalSpec.

Types 

There are two basic types of magnetic drive pumps: rotating shaft and stationary shaft.

• Rotating shaft magnetic drive pumps are designed for heavy-duty applications. They are usually made of metal, which provides the best strength, temperature, and pressure ratings. The rotating shaft increases the complexity of the pump, meaning more parts are required. More parts means more maintenance and higher costs.

• Stationary shaft magnetic drive pumps have fixed shafts and the driven magnets move an entire are designed for light to medium-duty applications. They are usually made of non-metallic components (such as ceramics and plastics) which generally provide good corrosion resistance but have a limited temperature range up to 200-250

  2012-06-29

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