Some of the couplings used on industrial equipment are capable of transmitting large amounts of torque in a reasonably small space. They also do not require lubrication, and are quite easy to install, in most circumstances. These attributes make them quite desirable in some industrial applications. The elements themselves are quite tolerant of small amounts of misalignment. But the shafts and bearings may not be able to tolerate the same degree of misalignment.
A few years ago, I checked alignment on a 250hp pump, driven by an electric motor, and coupled using one of these elastomeric couplings. The mechanics in this facility had been replacing the mechanical seal every few months, and didn’t know why. I checked their alignment, and found it to be out of tolerance only slightly; which did not explain the reason for so many seal failures.
We removed the coupling element, and found that misalignment was obvious – just by sight. We laser aligned the machines with a Fixturlaser NXA, while the coupling element was removed. Then we re-installed the element. The seal failures were eliminated.
To be honest, this IS NOT the fault of the coupling or the coupling manufacturer. All coupling manufacturing companies typically stress that care should be taken to achieve the best alignment. Remember, flexible couplings are not infinitely flexible. In all cases, make sure the alignment quality is good enough for all machine components – not just the coupling.
If you have questions about alignment quality, please feel free to contact us at www.vibralign.com.