Service centers are often called on to provide replacement pumps or pump motors or to advise on pump retrofit and re-application projects. A good understanding of the parameters that govern pump performance is essential to help customers with these opportunities. The information here relates to rotodynamic pumps (centrifugal and axial flow impellers) and not to positive displacement pumps.

Here’s a random collection of common misconceptions about three-phase squirrel-cage motors and the facts that deny them.

Determining the source of noise in an electric motor is often more challenging than correcting it. A methodical investigative approach, however, can narrow the possibilities and make it easier to resolve the issue—with one caveat. If the noise is due to something in the motor design (e.g., a manufacturing defect or anomaly), a solution may be impossible or impractical.

Storing an electric motor for more than a few weeks involves several steps to ensure it will operate properly when needed.  Factors like temperature, humidity and ambient vibration in the storage area also influence the choice of storage methods, some of which may be impractical for smaller machines or need to be reversed before the motor goes into storage.

To ensure the reliability of an RV’s electrical devices, especially electric motors, campers must know the service voltage of the hookup their RV is using. Teaching consumers to check that before they plug in the vehicle could save them many headaches.

Vertical turbine pumps (VTP) commonly have rotors with multiple mixed-flow impellers (sometimes 12 or more) that are supported by a vertical pump motor. Such designs offer a lift adjustment for raising or lowering the pump rotor to properly position the impellers within the bowl. Depending on the type of pump, this may be critical for maximizing pump efficiency and could have a significant impact on motor load (current) and reliability.

Vertical turbine pumps depend on the vertical motor's thrust bearings to support the combined weight of the pump rotor and the motor rotor and to counteract the dynamic down-thrust that the pump impellers generate in lifting the liquid.

Those familiar with industrial electric motors have heard “DC is dead” for decades as advances in variable-frequency drive (VFD) technology for AC squirrel cage induction motors (SCIMs) seemed destined to replace their DC counterparts in every conceivable application.

But just as DC’s demise was greatly exaggerated, so too is the prospect of successor technologies replacing the installed base of SCIMs any time soon – whether for new applications or replacement motors.

Regardless of the method used to detect winding temperature, the total, or hot spot, temperature is the real limit; and the lower it is, the better. Don’t let excessive heat kill your motors before their time.

One of the most common repairs on centrifugal pumps is replacing worn or damaged wear rings. To restore efficient, reliable operation and prevent catastrophic pump failure, it is critical to restore proper clearances between the stationary casing wear ring and the rotating impeller wear ring. Although many pump manufacturers provide clearances and dimensions, some do not. There are plenty of aging pumps around from now-defunct manufacturers for which dimension data is simply not available.

In such cases, the rule of thumb that follows provides some guidance for acceptable running clearances, or the minimum running clearance chart in American Petroleum Institute (API) Standard 610 can be used as a guide.