What occurs when a flexible coupling "locks up"?

When a flexible coupling "locks up," it means that it has lost its ability to accommodate misalignments between coupled shafts. In a functioning flexible coupling, the design allows for some degree of misalignment—whether angular, parallel, or axial—so that the shafts can operate smoothly without excessive wear or damage.

When locking up occurs, misalignment that typically would be tolerated becomes rigidly transferred through the shaft assemblies. This can lead to increased stress on the shaft, bearings, and connected equipment since the flexibility that would normally absorb some of these misalignment forces is no longer available. Consequently, the components face greater risks of wear or failure due to the additional stress.

This characteristic of the flexible coupling is crucial to understand, especially in applications involving rotating machinery where proper alignment is essential for efficient operation.