Condition monitoring for the safe operation of offshore cranes

Abstract

Offshore cranes work in harsher conditions than their onshore counterparts, with exposure to a highly corrosive environment and dynamic loading when conducting lifts from floating vessels. These degradation mechanisms can significantly reduce equipment life expectancy and increase maintenance/replacement costs without adequate mitigation programs in place. A systematic process must be followed to identify the potential for loss of integrity of components that could lead to failure, and strategies should be defined/implemented to ensure safe operation.

Study outcomes feed into the maintenance and sparing philosophy, and cascade to site personnel as maintenance and operating procedures. The implementation of a robust condition-monitoring program prior to degradation occurring is a key factor in the success of this program, examples of which include the following.

• Slew bearing condition monitoring: in addition to regular visual inspection and recording of measurable readings, a well-structured grease sampling and analysis protocol provides early detection of moisture ingress, deterioration of lubrication and bearing failure.

• Structural integrity: reporting on integrity by exception does not provide confidence that an area may have been left out, or consistency in ongoing reporting.

• End of useful life definition: some components aren’t available for inspection; others can be inspected however they are susceptible to failures that are not practically detectable. These potential hidden failures can be prevented if a process is followed where the critical component’s operating life is defined, with appropriate supporting justification, and it is renewed accordingly regardless of visual appearance.

An effective condition-monitoring program allows the operator to ascertain if the strategies in place are effective, pick up early detection of potential failure, and arrest the degradation while still inside a safe operating envelope.