Message Board Thread - "Hot Shafts at Couplings"

Back to Threads | Back to Forums

TitleByPosted On
Hot Shafts at Couplings Eddie Hindmarsh 7/17/2004
Where the shaft of an electric motor is coupled to a pump or something similar, the coupling being of uniform temperature, why should one of the shafts be considerably hotter than the other. If this is normal, which one would be expected to be hotter, or, is it an effect of a misalignment, or some other problem.
Eddie Hindmarsh
 
Re:Hot Shafts at Couplings Carl M 7/20/2004
Many reasons why you may see this.
If the shaft goes to a pump's packing seal there will be elevated temperature due to the friction of the seal. The pump's fluid temperature will effect the pump,and shaft, either hotter or cooler. If I see a suspected anomaly I'll tighten the span to identify the source of the heat to see if it's coming from the coupling interface, the motor bearing,the pump seal or gearbox bearing. The coupling area should not be warmer than either shaft. Otherwise I'd suspect alignment or a worn/broken coupling.

Carl M
 
Re:Hot Shafts at Couplings RonFrend 8/4/2004
In 1995 Miller Brewing Company carried out a series of tests in which they took a motor/pump set and misligned it by 0.030". The same test was carried out using seven different coupling types and the results were surprising.

The rubber tyre type couplings caused the bearings on the coupling end of the motor AND the pump to heat up.

The chain type coupling heated itself up.

Spider insert couplings caused a (smaller than chain type) increase in the coupling temperature.

Spigot type couplings seemed to heat up more on one side than the other.

So all in all there is no simple answer to your question but the dynamics of the straining coupling and shaft have to result in heat build up but extactly where depends on the design.

I have attached a picture of a typical tyre type coupling - don't believe what they tell you about flexible couplings. Rubber under load is incompressible and it is the bearings that suffer.
 


  • Back to Threads
  • Back to Forums

     

  •   Copyright © FLIR Systems, Inc 2012