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Tools & Technical Reference


Centrifugal Pump Overview

Centrifugal Pump ExplodedThe term "centrifugal pump" encompasses a multitude of pump technologies. Centrifugal means "directed or moving away from a center or axis", therefore a centrifugal pump uses a rotating impeller to move the fluid outward. Fluid enters the pump and is drawn into the eye, or center, of the impeller and then is forced outward through the vanes (blades) via centrifugal force generated by the rotating action of the impeller. The fluid is forced to the outside of the pump casing (or volute) and out the pump's discharge (see figure 1). The flow of a centrifugal pump depends on the system pressure drop: the higher the system's pressure drop, the lower the flow (See application note: A Primer on Pressure Drop).

Lytron's cooling systems use seal-less, magnetically-driven centrifugal pumps, also known as mag-drives. Magnetically driven pumps use two magnets to drive the impeller. One magnet is attached to the motor shaft, generally referred to as the "drive magnet". The other magnet is attached to the impeller (the "driven" or "impeller" magnet). The drive magnet spins causing the impeller magnet, and therefore impeller, to spin at the same rate. This pump design eliminates pump seals which often wear out from the friction caused by the rotation of the motor shaft and are a source of leakage. In Lytron's centrifugal pumps, the drive magnet is integrally molded into the impeller and thermoplastically coated to ensure zero contamination of the pump fluid. Thus, "mag-drive" ensures pump integrity and eliminates any possibility of shaft or seal leakage.

Magnetically-driven centrifugal pumps have many features that make them preferred for chiller/cooling system applications. When operated properly, they do not have any significant wear items therefore the centrifugal pump's life will significantly exceed that of positive displacement pumps and centrifugal pumps with seals. Also this design does not generate particles that could clog the system's filters so the pump's performance will not change over time. All pumps will impart some heat to the fluid but it is important to minimize heat added from the pump to ensure the recirculating chiller has tight temperature stability. Since mag-drive pumps have minimal frictional surfaces to generate heat, they transfer far less heat to the fluid than other pump styles.

This long, maintenance-free service life, combined with the other design benefits have made magnetically driven centrifugal pumps a leading choice for Lytron's cooling systems.

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