Underwater acoustic emission monitoring – Experimental investigations and acoustic signature recognition of synthetic mooring ropes

Abstract

Mooring ropes are essential components of offshore installations, and synthetic ropes are increasingly preferred because of their favourable cost to weight ratios. In-service condition of these materials is traditionally monitored through costly visual inspection, which adds to the operating costs of these structures. Acoustic Emissions (AE) are widely used for condition-monitoring in air, and show great potential underwater. This paper investigates the AE signatures of synthetic mooring ropes subjected to sinusoidal tension-tension loading in a controlled environment, using a large-scale dynamic tensile test rig. With a linear array of 3 broadband (20 Hz-50 kHz) hydrophones, four main signatures are identified: low-to high frequency, low-amplitude signals (50 Hz-10 kHz), lowamplitude broadband signals (10 kHz-20 kHz), high amplitude signals (10 Hz-48 kHz) and mediumamplitude signals (500 Hz-48 kHz). These AE types are related to different stages of rope behaviour, from bedding-in to degradation and failure. The main findings are that the failure location and breaking load can be identified through the detection of AE. The occurrence of high amplitude AE bursts in relation to the applied tensile load allows the detection of an imminent failure, i.e. prior to the failure event. These initial results indicate that AE analyses can enable the integrity of synthetic mooring ropes to be monitored.

Condition Monitoring Technologies for Synthetic Fiber Ropes - a Review

“…Figure 19 shows their main results where it is evident that these trends can serve as condition indicators for determining the remaining useful life of the fiber rope. The recent work by Bashir et al (2017) support Figure 18. Infrared transducer set-up (Laura et al, 1995).…”

Use of sound spectral signals analysis to assess the technical condition of mechanical devices

“…Recently, an AE technique monitoring in plain and steel fiber reinforced concrete specimens was analyzed using unsupervised kernel fuzzy cmeans pattern recognition and the principal component method to categorize various damage stages [28]. Results were reported on AE signatures of synthetic mooring ropes subjected to sinusoidal tension-tension loading in a controlled environment [29], a possible correlation between the dominant failure in glass fibrereinforced plastics and their corrwsponding acoustic emissions was reportedly evaluated [30], the Identification of Active Damage Processes acoustic emission method was reported to be applied to continuous monitoring of active destructive processes in reinforced concrete bridges [31].…”

New On-Line MFL Testing Method and Apparatus for Winding Mine Hoist Wire Rope

“…The NDT methods for wire rope include magnetic flux leakage (MFL) testing methods [7,8], ultrasonic testing (UT) methods [9], X-ray inspection [10], acoustic emission (AE) inspection methods [11,12], and eddy current testing (ECT) methods [13]. Among them, the MFL testing method is considered to be the most effective method for detecting wire rope defects [14,15].…”