Abstract
Purpose Mooring chains used to stabilise offshore floating platforms are often subjected to harsh environmental conditions on a daily basis, i.e. high tidal waves, storms, etc. Therefore, the integrity assessment of chain links is vital, and regular inspection is mandatory for offshore structures. The development of chain climbing robots is still in its infancy due to the complicated climbing structure presented by mooring chains. The purpose of this paper is to establish an automated climbing technique for mooring chain inspection. Design/methodology/approach This paper presents a Cartesian legged tracked-wheel crawler robot developed for mooring chain inspection. The proposed robot addresses the misalignment condition of the mooring chains which is commonly evident in in situ conditions. Findings The mooring chain link misalignment is investigated mathematically and used as a design parameter for the proposed robot. The robot is validated with laboratory-based climbing experiments. Practical implications Chain breaking can lead to vessel drift and serious damage such as riser rupture, production shutdown and hydrocarbon release. Currently, structural health monitoring of chain links is conducted using either remotely operated vehicles which come at a high cost or by manual means which increase the danger to human operators. The robot can be used as a platform to convey equipment, i.e. tools for non-destructive testing/evaluation applications. Originality/value This study has upgraded a previously designed magnetic adhesion tracked-wheel mooring chain climbing robot to address the misalignment issues of operational mooring chains. As a result of this study, the idea of an orthogonally placed Cartesian legged-magnetic adhesion tracked wheel robotic platform which can eliminate concerns related to the misaligned mooring chain climbing has been established.
Highlights
An exponential increase of floating oil and gas production systems has been recorded around the world due to the high consumption and demand for fossil fuel energy
Floating Production Units (FPU) were recorded of which 62% were reported as Floating Production Storage and Offloading (FPSO) units (Gordon, et al, 2014)
Automated mechanisms /visual aided Non-Destructive Testing (NDT) measurements assisted by Remotely Operated Vehicles (ROVs) for subsea mooring chain inspection were reported in the literature (Welapetage, 2017), (Yoshie & Toshinari, 2013) and (Hall, et al, 1999)
Summary
An exponential increase of floating oil and gas production systems has been recorded around the world due to the high consumption and demand for fossil fuel energy. Integrity assessment of offshore floating platforms needs to be addressed by providing in-situ physical access to the mooring systems as the removal and transportation of chain links for inspection/repair is not practical. Trained Non-Destructive Testing (NDT) divers and ROV inspections are the most common industrial mooring inspection methods These methods raise health and safety concerns and diver inspection is very hazardous when inspecting a chain in the splash zone area ( Angulo, et al, 2017). Automated mechanisms /visual aided NDT measurements assisted by Remotely Operated Vehicles (ROVs) for subsea mooring chain inspection were reported in the literature (Welapetage, 2017), (Yoshie & Toshinari , 2013) and (Hall, et al, 1999). The final section of the paper describes the prototype and validation of the climbing technique
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