15 months prewarning for crown block sheave bearing damage offshore

Bearing damage on the fast-line side of a crown block sheave at an offshore drilling rig was monitored for 15 months before replacement. Using condition monitoring solutions for marine and offshore applications based on patented high-definition technology, long prewarning time was achieved and planned action was enabled.

Application and monitoring setup

On offshore drilling rigs and vessels, drilling equipment is housed in the derrick with the crown block cluster positioned on top. Several sheaves rotate at approximately 5 to 180 rpm, and a wire from the drawwork moves between the sheaves at the crown block and the travelling block, controlling the top drive’s vertical motion.

One DuoTech accelerometer was installed on each side of the crown block and connected to an Intellinova Parallel EN Ex online system. RPM was derived from the drawwork RPM and calculated based on sheave diameter and wire speed between the drawwork and sheaves.

Results and benefits

After the monitoring system was installed, the first indication of bearing damage appeared in the FFT, showing a clear match with BPFO. All configured technologies displayed the same pattern, and the Colored Spectrum Overview showed progressive damage development.

Using the Decision Support System, a gradually increasing health score trend for BPFO with HD ENV4 was observed over time. The bearing was replaced after an extended monitoring period, and the bearing damage was visually verified after replacement.