Condition Monitoring Technologies for Steel Wire Ropes – A Review

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 3-4000 meters, drilling lines, marine riser tensioner lines and anchor lines. For mooring, there is a clear tendency for 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 depths. Today’s practice is to discard the rope after a predetermined number of uses due to fatigue from bending over sheaves with a large safety factor, especially for systems regulated by active heave compensation (AHC). 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 for SWR have been developed over a period of 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 (AE), ultrasound, X- and γ-rays, fiber optics, optical and thermal vision and current signature analysis. Each technique is thoroughly presented and discussed for the application of subsea construction. 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

An indicator of message quality for a single optical sensor using a template based tracking algorithm

The volume of messages generated by spaced based interceptors (SBI'S) resulting from a booster launch can lead to an unacceptably large total time for the messages to propagate through the system. In order to help relieve this problem, one might identify the SBI's with the highest quality estimates of the launch information. Message traffic can by sharply reduced if these SBI's can be identified, and message transmission restricted to their messages. Launch parameters and position are estimated using a template based tracking algorithm. A single measure of quality based on the estimated covariance matrix of the measured position is proposed and tested using simulation. Results describe possible modifications to the template based tracking algorithm that would reduce error and allow the quality of a message to be determined.http://archive.org/details/anindicatorofmes1094538539Lieutenant, United States Naval ReserveApproved for public release; distribution is unlimited