Modified Concentric Vs. Volute design casings - What's the difference ?

A volute design introduces radial forces attempting to move the impeller in a direction other than the true center of the rotation.  These forces will be minimal when the flow is at the best efficiency point, however will be high at low flow or high flow conditions.  A concentric casing will not introduce any radial forces and will offer hydraulic balance to center the impeller with the solution being pumped.  A Modified concentric design is used for the ULTRA-Chem to offer a low radial load to the impeller during any flow condition.  The magnetic drive type of pump design, not using a metal drive shaft for support, would be subject to shaft / impeller defection leading to increased wear and replacement requirements.

The below chart will indicate the comparison of the two designs in relationship for the force introduced on the impeller / shaft.