Chapter 8 - Couplings Flashcards
Coupling
Connects two shafts, end-to-end in the same line, for two main purposes.
Should not be operated when the angular and parallel misalignment are at a maximum.
Two Purposes of Couplings
The transmit power, causing rotation, at the same RPM/Torque.
Compensate for minor misalignment and random movement between the shafts.
Angular Misalignment
Angle between the centerlines of the two connected shafts.
Axial Displacement
Change in axial position of the shaft and part of the coupling in a direction parallel to the axial centerline.
Axial Forces
The driver or driven equipment can generate axial forces in which case the couple will pass those forces to the next available bearing with thrust capability.
Axial Freedom
This characteristic allows for variation in coupling position on the shaft at time of installation.
Backlash
The amount of free movement between two rotation, mating parts.
Bore
Central hole that become the mounting surface for the coupling on the shaft.
Most common is round, but can be all types of shapes.
Damping
Reduced vibration between driver and driven shafts so that heat is dissipated.
BE or BSE
Distance between shafts.
Factors of Safety
Safety compensations for temperature, material vibrations, fatigue strength, dimensional variations, tolerances, and potential stress risers.
Fail-Safe
A coupling that will continue to operate for a period of time after the torque-transmitting element has failed.
Parallel Misalignment
A measure of offset distance between the centerlines of driving and driven shafts.
Coupling Evaluation Factors:
Design Alignment Capabilities Axial Freedom Backlash Chemical Resistance Damping Capacity Ease of Installation Fail Safe or Fusible Link Field Repairable High Speed Capacity Inherent Balance
Coupling Selection factors:
Horsepower Torque Speed Shaft Sizes Environment Conditions Type of prime mover Space Limitations
