A vessel’s operator contacted us because the starboard clutch had overheated. Within twenty-four hours, we were on board to check it out. This ship was being returned to service after being layed up for two years.
A review of the propulsion system showed that the clutches were quill mounted in line with the engines. Disassembly of the clutch did not reveal any internal problem that could result in a hangup.
Next we reviewed the original design drawings and there we found a discrepancy with what currently existed. The old design included a pedestal bearing on the forward end of the quill shaft. The installation no longer included this bearing.
This change made a significant difference. With the bearing, the shaft would be fully supported requiring a full (double-flex) coupling. Without the bearing, the appropriate coupling would be a flex-rigid (single-flex) coupling.
When the vessel was returned to service the wrong coupling was installed. Consequently, the assembly whipped and the orbiting clutch plates kept making contact resulting in excessive heat.
They replaced the coupling and the propulsion system is now operating smoothly.