I agree with others the concerns about deadheading a pump usually have nothing to do with the coupling.If there is axial force on the pump, it's range of motion will usually be restricted by the pump thrust bearing, but that doesn't rule out fatigue stresses to the coupling as I think suggested above.We do have one set of single stage centrifugal pumps driven by sleeve bearing motor through shim pack coupling where we see large 0.125" axial movement of the motor shaft at a frequency of maybe 1 hz which occurs only when the pump is at low flow (goes away at higher flow).  I figure that the broadband / imapcting forces from small movements of the pump rotor (<0.020" pump bearing clearance) act as base excitation for the spring / mass system consisting of the coupling / motor, and excite the resonant frequenc of that system which willbe quite low due to flexible shim pack coupling and large motor mass.  That Slurry pumps low-flow operation recurs periodically for periods of hours to days, but we have not seen cracking of the shim packs.You might want to tell us what type coupling and describe the bearing configurations on pump and motor. 

2011-08-08

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