A novel underwater measurement method for mooring system using self-contained technique

Abstract

This article introduces a prototype measurement method for investigating deep-water mooring systems. Measurement information and specifications are determined according to mooring system analysis. Mooring line information is difficult to measure underwater, particularly for aging platforms. To solve this problem, a novel mooring line tension measurement strategy based on lumped mass method is proposed. A type of self-contained sensor is designed and manufactured to realize dynamic response measurement of mooring systems underwater. The sensor is described in detail, including its design requirement, hardware design, and installation mode. A comprehensive field test system was constructed on a semi-submersible platform in South China Sea. Prototype data, including the data measured during typhoons, are introduced and discussed to improve the accuracy, feasibility, and stability of the proposed measurement method.

Development and Sensing Properties Study of Underwater Assembled Water Depth-Inclination Sensors for a Multi-Component Mooring System, Using a Self-Contained Technique

“…Figure 20a,b shows the distributions of the power spectral density (PSD) of thewater depth and inclination measured by the self-contained sensor. Two spectral peaks could be respectively found in the PSD figures at 0.12 Hz, which is close to the wave frequency, and at 0.16 Hz, which is near the natural frequency of the mooring line [16]. The PSD profiles of the present sensor show that the underwater field test system could accurately acquire the frequency domain characteristics of the mooring lines.…”

“…At present, there are three main types of monitoring methodologies used in multi-point mooring systems: (1) Load cells [12], which are installed at the chain stopper on the deck to measure the mooring line tension; (2) Fiber Bragg Gauges (FBG) [16], or strain gauges, which are pasted on the mooring line for short-term measurement; and (3) In-site underwater mooring systems [14], which have specially designed measurement instruments. …”

An Overview of Structural Design, Analysis and Common Monitoring Technologies for Floating Platform and Flexible Cable and Riser

“…Topside tension measurements, in-water sensor measurements and robot-assisted measurements are often used internationally. Self-capacitating sensors and hydroacoustic transmission have been used for a long time on the Challenge FPS platform in the South China Sea (Du et al, 2016). With the progress of underwater data transmission and wireless charging technology, underwater self-capacitating sensors have gradually developed towards long monitoring cycles and ultra-deep water (Prasanth, 2021;Xiao and Huang, 2020;Cao et al, 2016).…”

A fuzzy genetic model for estimating forces in link chains from the measurement of the natural frequencies

“…The measurement of the loads in mooring lines is currently made by techniques like the installation of load cells at the connection of the mooring line with the ship or floating platform, for example, or other types of sensors at the chains (PAPADIMITRIOU, 2016), (DU et al, 2015), (ROBERT et al, 1973), (PRIOUR, 1995) or even through the approximation of the shape of the mooring line to a catenary ( JAMIESON, 2013).…”