REVIEW OF CONDITION MONITORING TECHNOLOGIES FOR OFFSHORE STEEL WIRE ROPES

摘要

In this research, we review condition-monitoring technologies for offshore steel wire ropes (SWR). Such ropes are used within several offshore applications including cranes for load handling such as subsea construction at depths up to 3000 meters, drilling lines, marine riser tensioner lines and anchor lines. For mooring, there is a clear tendency of using fiber ropes. Especially for heavy-lift cranes and subsea deployment, winches with strong ropes of up to 180 mm in diameter may be required, which has a considerable cost per rope, especially for large water depth. Today's practice have to discard the rope after a predetermined number of uses due to fatigue from bending over sheaves with a large safety factor. Other sources of degradation are abrasion, fretting, corrosion and extreme forces, and are typically accelerated due to undersized or poorly maintained sheaves, groove type, lack of lubrication and excessive load. Non-destructive testing techniques have been developed for SWR during over 100 years. Most notably are the magnetic leakage techniques (electromagnetic methods), which are widely used within several industries such as mining and construction. The content reviewed in this research is primarily the developments the last five years within the topics of electromagnetic method, acoustic emissions, ultrasound, X- and γ-rays, fiber optics, optical and thermal vision and current signature analysis. Each technique is weighed based on pros and cons for the subsea construction application. Assessments include ability to detect localized flaws (i.e. broken wire) both internally and externally, estimated loss of metallic cross sectional area, robustness with respect to the rough offshore environment, ability to evaluate both rope and end fittings, and ability to work during operation.