The development of climbing robots for mooring chain applications is still in its infancy due to the operational complexity and the geometrical features of the chain. Mooring chains are subjected to high tidal waves, harsh environmental conditions and storms on a daily basis. Therefore, the integrity assessment of chain links is vital and regular inspection is mandatory for offshore structures. The Magnetic adhesion tracked-wheel crawler robot presented in this study is suitable for mooring chain climbing in air and the technique can be adapted for underwater use. The robotic platform can climb mooring chains at a maximum speed of 42 cm/minute with an external load of 50 N. A numerical study was conducted to investigate the adhesion module and analysis of the robot structural design. Numerical results were validated using a prototyped robot in laboratory conditions. The proposed robot can be used as a platform to convey equipment for non-destructive testing applications.
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.
Only a few attempts have been made to investigate the possibilities of developing chain climbing robot due to the complexity of the structure and physical nature of chain links. Mooring chains are subjected to large tidal waves, harsh environmental conditions and storms on a daily basis. Therefore, periodic inspection of the integrity of chain links is important. Work reported in this paper investigates the possibilities of mooring chain climbing by using tracked wheel locomotion. The permanent magnet adhesion, tracked wheel crawler robot developed for this purpose can climb on mooring chains both in air and underwater with a variable speed according to the inspection requirements (maximum speed of 42cm/minute). It is able to handle an external downward force of 50N during the climbing motion. Numerical modelling based analysis of a magnet adhesion module and the strength of the robot structure is validated with prototyping and testing of the concept.
Inspection of mooring chains is an important but dangerous and costly procedure covering inspection above and below the waterline. The paper presents initial results from the RIMCAW project which aimed at designing and building an inspection robot able to climb mooring chains and deploy NDT technologies for scanning individual links thereby detecting critical defects. The paper focuses on the design and realisation of the inchworm type novel crawler developed and tested in the TWI Middlesbrough, UK water tank.
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