Hull Inspection Research Articles

Pose-Graph SLAM Using Forward-Looking Sonar

This letter reports on a real-time simultaneous localization and mapping (SLAM) algorithm for an underwater robot using an imaging forward-looking sonar and its application in the area of autonomous underwater ship hull inspection. The proposed algorithm overcomes specific challenges associated with deliverable underwater acoustic SLAM, including feature sparsity and false-positive data association when utilizing sonar imagery. An advanced machine learning technique is used to provide saliency-aware loop closure proposals. A more reliable data association approach using different available constraints is also developed. Our evaluation is presented on the real-world data collected in a ship hull inspection application, which illustrates the system's performance and robustness.

Life cycle cost and environmental impact analysis of ship hull maintenance strategies for a short route hybrid ferry

This paper provides a general insight into the importance of proper hull maintenance and suggests an optimal maintenance strategy for ship operators from both an economic and environmental point of view. Results of life cycle assessment show that significant cost reductions can be obtained by renewing steels every 10 years within the proposed hull maintenance strategy. The assessment also indicates that annual hull inspections and re-coating can contribute to reducing hull resistance and hence fuel consumption, thereby reducing the overall operating costs and emissions. This paper provides ship owners a direct relationship between effective hull maintenance and the reduction in maintenance cost. It also provides information to inform policy makers of the benefits of following a maintenance optimization strategy. This study shows that life cycle assessment can provide information to shipyards and owners to facilitate reliable long-term maintenance decisions.

Pose Estimation Considering an Uncertainty Model of Stereo Vision for In-Water Ship Hull Inspection

For visual inspection of underwater structures by using an autonomous underwater vehicle (AUV), the relative pose between the AUV and the underwater structure needs to be estimated accurately. In this paper, a vision based pose estimation method for in-water ship hull inspection using 3D point cloud data provided by a stereo vision system is proposed. In particular, a systematic procedure to evaluate the uncertainty of feature point location on the obtained stereo images is formulated and applied. An experimental result is presented to demonstrate the practical feasibility of the proposed approach.

A dynamic model for the hull inspection of ships: The analysis and results

Risk Based Inspection in the maritime sector is an approach that involves the quantitative estimation of the probability of failure and the respective consequences concerning either an equipment item or the hull structure of the vessel. The proper risk based inspection plan has great significance on balancing the safe operation requirements and the inspection costs. This paper deals with the ageing and the breakdown of the fore part of a ship due to different degradation and failure mechanisms (corrosion, fatigue, deformation) and the emerged risks that are related to the property, the personnel and the environment. The developed model evaluates several probable inspection schemes, which diversify based on the inspection effectiveness, the time intervals and the corresponding costs.

A vision-based system for robotic inspection of marine vessels

This paper presents a novel intelligent system for the automatic visual inspection of vessels consisting of three processing levels: (a) data acquisition: images are collected using a magnetic climbing robot equipped with a low-cost monocular camera for hull inspection; (b) feature extraction: all the images are characterized by 12 features consisting of color moments in each channel of the HSV space; (c) classification: a novel tool, based on an ensemble of classifiers, is proposed to classify sub-images as rust or non-rust. This paper provides a helpful roadmap to guide future research on the detection of rusting of metals using image processing.

Analysis of Hull Coating Renewal in Ship Repairing

Hull coating (external blasting and painting) renewal (repair) is a part of routine ship maintenance. It is carried out only when the ship is in a dock (graving dock, floating dock, or slipway). For a regular maintenance schedule, the scope of hull coating repairing works dictates the duration of stay of a ship in the dock. It is very vital therefore to estimate the scope of work for hull coating before docking. As soon as the ship is docked, a joint hull inspection by representatives of the owner, dry-dock, and coatings supplier accurately determines the hull coatings scope of work. Most of the time, the inspection result does not match with the preplanned dock operation schedule. Hence, the overall dock operation schedule gets affected due to delay or early undocking of a ship. Hull coating repair and related information for 149 cargo ships were collected from a single shipyard. It was analyzed and presented in both tabular and graphical forms to show the relationship between the scope of work and the age, size, and type of ships. The physical size of a ship has a great influence on the hull blasting and painting repairing works irrespective of design parameters and types of the ship. Using ship dimensions, actual surface area, and other factors, a method of estimating the hull coating scope is proposed. In this article, the authors have made an attempt to identify the independent variables that influence the scope of work (dependent variable), and suggested the possible interrelationships between the dependent and independent variables, which appeared to be linear. 1. Introduction For a newly built ship, the external hull is coated with two types of painting system, namely, anticorrosive painting system and antifouling painting system. Anticorrosive painting system is to protect the steel from corrosion caused by oxidation, and antifouling painting system is to protect the underwater surface from marine growth. After proper surface preparation, multiple coats of anticorrosive paint are applied to the entire hull (underwater and above water) as per painting schemes followed by multiple coats of antifouling paints to the underwater area.

In-Service Hull Inspections for Avoiding Dry Docking Safely

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper OTC 26750, “In-Service Hull Inspections for Avoiding Dry Docking Safely,” by D. Constantinis and P. Davies, EM&I Group, prepared for the 2016 Offshore Technology Conference Asia, Kuala Lumpur, 22–25 March. The paper has not been peer reviewed. Copyright 2016 Offshore Technology Conference. Reproduced by permission. Current methods for external inspection of floating assets on station use divers or remotely operated vehicles (ROVs), but these methods incur high safety, people-on-board (POB), and cost penalties. The data produced by these methods are restricted by marine growth and limited access to isolation valves. The Hull Inspection Techniques and Strategy (HITS) joint-industry project (JIP) called for new methods to be developed that minimize or eliminate diving. This has been achieved by carrying out many of the inspections from inside the hull. Introduction The exploration and production of deep-water hydrocarbon reserves requires evermore-complex and high-capital-value floating assets. There are a number of key drivers required to optimize profitable operations, including managing the integrity of the topside and hull while reducing cost and POB and complying with client, corporate, and regulatory requirements. Floating production units can be designed for 25 years or more on station, and the new-generation ultradeepwater (UDW) drilling units also need to plan their integrity-management strategies without dry docking for extended periods (Fig. 1). These requirements have driven the development of innovative methods for inspecting, testing, and maintaining pressure systems as well as hull structures, the latter sometimes not getting the integrity attention it deserves. The HITS JIP was formed to address these issues, with membership from regulators, oil majors, class societies, lease operators, service companies, and educational bodies representing all sectors of the industry. The HITS JIP drew opinion from the industry and concluded that there are principally four challenges that should be addressed: Minimizing diving operations for hull in-water inspections Minimizing man entry for inspection of confined spaces Developing a capability to inspect cargo oil tanks with minimal cleaning requirements Developing competency standards for hull inspectors The HITS JIP does not carry out any developments itself but encourages industry to develop or adapt technology to improve hull-inspection techniques and evaluates the results. An industrywide survey concluded that the first priority should be given to minimizing diving operations for hull inspection, and, accordingly, three of the HITS member organizations cooperated in the development of an alternative method. This paper describes the new methodology; details how it has been applied to floating production, storage, and offloading vessels (FPSOs) and UDW drillships; and presents the lessons learned through site implementation.

Technology Focus: Offshore Facilities (February 2017)

Technology Focus Welcome to the Offshore Facilities feature in this month’s JPT. I had the plea-sure of screening 207 papers submitted to SPE in this field during the past year to come up with the three papers selected for this issue that cover elements of offshore facilities design and inspection. The first paper describes a design case study for split-process floating liquefied natural gas, in which the primary production and gas-treatment functions are provided on a host platform while liquefaction occurs on separate vessels that serve also for storage and trans-port. Splitting the services results in advantages that include facilitating standardization of the liquefaction design and eliminating the need for liquefied-natural-gas-offloading systems designed for open-water conditions. The next paper describes a risk-based approach for application of passive fire protection (PFP) on an offshore structure. Principles of this unified risk-based approach for accidental loadings and its application to fire-response analysis and PFP are explained, and the method is compared against the conventional approach. The third paper covers work performed by the Hull Inspection Techniques and Strategy joint-industry project to develop new floating production, storage, and offloading vessel hull-inspection methods that minimize or eliminate diving. This has been achieved by conducting many of the inspections from inside the hull, using advanced methods to inspect critical isolation valves and marine piping, and inspecting the hull appendages with miniature remotely operated vehicles. The alternative method delivers improved inspection data as well as significant reductions in cost and people on board and minimal weather/sea-state downtime. I hope you enjoy reading these papers. Recommended additional reading at OnePetro: www.onepetro.org. IPTC 18373 Adapting the Caspian Factor for the Installation of Petronas’ First Gravity-Based Structure by Khairil Raezwan Rashdi, Petronas, et al. OTC 26481 Development of a Novel Hybrid AUV System for Pipeline Inspection in Gulf of Thailand by Phakhachon Hoonsuwan, PTTEP, et al. OTC 27068 Fuel Efficiency on Floating Production Systems by Jos Bronneberg, SBM Offshore USA

Innovative inspection techniques for ultra deepwater drillships and other floating O&G production assets saving costs, enhancing safety, while assuring operational availability and asset integrity

The Hull Inspection Techniques and Strategy (HITS) Joint Industry Project (JIP), a subgroup of the Floating Production Storage and Offloading (FPSO) Research Forum, called for new methods to be developed that enhance safety, reduce costs and support the assurance of integrated asset management. Hull integrity is critical to enhancing safety and operational effectiveness for production operations, particularly for high-value assets. Good hull integrity requires accurate, relevant hull-inspection data of the internal structure, isolation valves, moonpools, external appendages and positioning systems. Current methods use divers or remotely operated vehicles (ROVs); this often disrupts drilling operations and, in the case of divers, is a high but managed risk. HITS JIP called for methods to minimise diver and man intervention in confined spaces. This has now been achieved on several assets while on station, operational and on-hire by an innovative method of conducting inspections from within the hull and using advanced techniques to inspect critical isolation valves, moonpool high-stress areas, thrusters and hull appendages. Aligning internal and external structural inspections optimises operational availability further and is achieved by means of class-approved ‘long-term inspection plans’ that align the ‘underwater’ scope with other hull inspections and spreads the work over several 5-year cycles. As well as safety enhancements, benefits include over 70% persons on board (POB) reduction on diver under water inspection in lieu of drydocking (UWILD) operations, minimising downtime and operational impact, and high-value inspection data. Further advances in hull inspection have also been proven that eliminate man entry of confined spaces for inspection of ballast and other tanks.

Terahertz Spectroscopy and Brewster Angle Reflection Imaging of Acoustic Tiles

A Brewster angle reflection imaging apparatus is demonstrated which is capable of detecting hidden water-filled voids in a rubber tile sample. This imaging application simulates a real-world hull inspection problem for Royal Canadian Navy Victoria-class submarines. The tile samples represent a challenging imaging application due to their large refractive index and absorption coefficient. With a rubber transmission window at approximately 80 GHz, terahertz (THz) sensing methods have shown promise for probing these structures in the laboratory. Operating at Brewster’s angle allows for the typically strong front surface reflection to be minimized while also conveniently making the method insensitive to air-filled voids. Using a broadband THz time-domain waveform imaging system (THz-TDS), we demonstrate satisfactory imaging and detection of water-filled voids without complicated signal processing. Optical properties of the tile samples at low THz frequencies are also reported.

Long‐term Mapping Techniques for Ship Hull Inspection and Surveillance using an Autonomous Underwater Vehicle

This paper reports on a system for an autonomous underwater vehicle to perform in situ, multiple session hull inspection using long‐term simultaneous localization and mapping (SLAM). Our method assumes very little a priori knowledge, and it does not require the aid of acoustic beacons for navigation, which is a typical mode of navigation in this type of application. Our system combines recent techniques in underwater saliency‐informed visual SLAM and a method for representing the ship hull surface as a collection of many locally planar surface features. This methodology produces accurate maps that can be constructed in real‐time on consumer‐grade computing hardware. A single‐session SLAM result is initially used as a prior map for later sessions, where the robot automatically merges the multiple surveys into a common hull‐relative reference frame. To perform the relocalization step, we use a particle filter that leverages the locally planar representation of the ship hull surface, and a fast visual descriptor matching algorithm. Finally, we apply the recently developed graph sparsification tool, generic linear constraints, as a way to manage the computational complexity of the SLAM system as the robot accumulates information across multiple sessions. We show results for 20 SLAM sessions for two large vessels over the course of days, months, and even up to three years, with a total path length of approximately 10.2 km.

Active visual SLAM for robotic area coverage: Theory and experiment

This paper reports on an integrated navigation algorithm for the visual simultaneous localization and mapping (SLAM) robotic area coverage problem. In the robotic area coverage problem, the goal is to explore and map a given target area within a reasonable amount of time. This goal necessitates the use of minimally redundant overlap trajectories for coverage efficiency; however, visual SLAM’s navigation estimate will inevitably drift over time in the absence of loop closures. Therefore, efficient area coverage and good SLAM navigation performance represent competing objectives. To solve this decision-making problem, we introduce perception-driven navigation, an integrated navigation algorithm that automatically balances between exploration and revisitation using a reward framework. This framework accounts for SLAM localization uncertainty, area coverage performance, and the identification of good candidate regions in the environment for visual perception. Results are shown for both a hybrid simulation and real-world demonstration of a visual SLAM system for autonomous underwater ship hull inspection.

Fourier‐based Registration for Robust Forward‐looking Sonar Mosaicing in Low‐visibility Underwater Environments

Vehicle operations in underwater environments are often compromised by poor visibility conditions. For instance, the perception range of optical devices is heavily constrained in turbid waters, thus complicating navigation and mapping tasks in environments such as harbors, bays, or rivers. A new generation of high‐definition forward‐looking sonars providing acoustic imagery at high frame rates has recently emerged as a promising alternative for working under these challenging conditions. However, the characteristics of the sonar data introduce difficulties in image registration, a key step in mosaicing and motion estimation applications. In this work, we propose the use of a Fourier‐based registration technique capable of handling the low resolution, noise, and artifacts associated with sonar image formation. When compared to a state‐of‐the art region‐based technique, our approach shows superior performance in the alignment of both consecutive and nonconsecutive views as well as higher robustness in featureless environments. The method is used to compute pose constraints between sonar frames that, integrated inside a global alignment framework, enable the rendering of consistent acoustic mosaics with high detail and increased resolution. An extensive experimental section is reported showing results in relevant field applications, such as ship hull inspection and harbor mapping.

HULL INSPECTION PRODUCTIVITY MEASUREMENT FOR A NEW SHIPBUILDING PROJECT (CASE STUDY OF BIC 11.02 A NEW SHIPBUILDING PROJECT)

Hull construction process for a new shipbuilding project usualy consist of a set of stages. Starting from material identification, marking, cutting fabrication, assembly and testing. For many shipyard hull inspection activity and hull production stages are joined to simplify production progress monitoring. A 20% credit given for inspection activity. Inspection activities particulary for hull construction which consist of inspection and repair work. Schedule slip of a new shipbuilding is very potencial. This condition is met when man power allocation and work priority are not set properly. Therefore, a clear parameter which conduct with inspection productivity to production manager should be provided. This parameter could help production manager to determine priority of repair work. In this case, differences parameter between production that is using pane measurement and inspection that is using compartement measurement. These two different parameter could make difficulties, particulary when production manager want to know how much progess has been done. A new method to converting the two different parameter has become a topic of this paper

반잠수식 시추선용 선체 유지보수 관리 시스템 개발

Each owner or operator of offshore products uses a maintenance management system like CMMS(Computerized Maintenance Management System) in order to manage their assets effectively and efficiently for a long time. But most of maintenance management systems have been focused on machinery items, not on 'Hull' until now. On the other hand, classifications like ABS, DNV, GL are having a sale on hull inspection and maintenance system for ships and an interest in hull maintenance system is increasing because of the application of EDD(Extended Dry Docking). This paper discusses the concept, inspection process and the practical application of Hull maintenance for Semi-submersible drilling rig to extend the service life and run a stable operation.

Real-Time Visual SLAM for Autonomous Underwater Hull Inspection Using Visual Saliency

This paper reports a real-time monocular visual simultaneous localization and mapping (SLAM) algorithm and results for its application in the area of autonomous underwater ship hull inspection. The proposed algorithm overcomes some of the specific challenges associated with underwater visual SLAM, namely, limited field of view imagery and feature-poor regions. It does so by exploiting our SLAM navigation prior within the image registration pipeline and by being selective about which imagery is considered informative in terms of our visual SLAM map. A novel online bag-of-words measure for intra and interimage saliency are introduced and are shown to be useful for image key-frame selection, information-gain-based link hypothesis, and novelty detection. Results from three real-world hull inspection experiments evaluate the overall approach, including one survey comprising a 3.4-h/2.7-km-long trajectory.

Development of an Underwater Robotic Inspection System using Mechanical Contact

This paper reports the development of a robotic inspection system using a mechanical contact mechanism that enhances the positioning stability of a small and lightweight underwater robot to take clear images of underwater targets and to work with manipulators for inspections under external disturbances. As described in this paper, first we perform a two‐dimensional numerical analysis based on force and moment acting on an underwater robot with a contact mechanism. Second, we experimentally investigate the friction coefficients of several soft and high friction materials for the contact points of a prototype contact mechanism to enhance the positioning stability of the robot. Based on the results of numerical analysis and the experimental investigation, we design and develop a prototype contact mechanism for an underwater robot. Moreover, we experimentally test the stability of the underwater robot with the contact mechanism in a test tank. Finally, a ship hull inspection is conducted as a field test in a port using the robot with the developed contact mechanism. The experimentally obtained results indicate that the proposed contact mechanism is a useful tool for underwater visual inspections and manipulator tasks of a small and lightweight underwater robot.

Active planning for underwater inspection and the benefit of adaptivity

We discuss the problem of inspecting an underwater structure, such as a submerged ship hull, with an autonomous underwater vehicle (AUV). Unlike a large body of prior work, we focus on planning the views of the AUV to improve the quality of the inspection, rather than maximizing the accuracy of a given data stream. We formulate the inspection planning problem as an extension to Bayesian active learning, and we show connections to recent theoretical guarantees in this area. We rigorously analyze the benefit of adaptive re-planning for such problems, and we prove that the potential benefit of adaptivity can be reduced from an exponential to a constant factor by changing the problem from cost minimization with a constraint on information gain to variance reduction with a constraint on cost. Such analysis allows the use of robust, non-adaptive planning algorithms that perform competitively with adaptive algorithms. Based on our analysis, we propose a method for constructing 3D meshes from sonar-derived point clouds, and we introduce uncertainty modeling through non-parametric Bayesian regression. Finally, we demonstrate the benefit of active inspection planning using sonar data from ship hull inspections with the Bluefin-MIT Hovering AUV.

Advanced perception, navigation and planning for autonomous in-water ship hull inspection

Inspection of ship hulls and marine structures using autonomous underwater vehicles has emerged as a unique and challenging application of robotics. The problem poses rich questions in physical design and operation, perception and navigation, and planning, driven by difficulties arising from the acoustic environment, poor water quality and the highly complex structures to be inspected. In this paper, we develop and apply algorithms for the central navigation and planning problems on ship hulls. These divide into two classes, suitable for the open, forward parts of a typical monohull, and for the complex areas around the shafting, propellers and rudders. On the open hull, we have integrated acoustic and visual mapping processes to achieve closed-loop control relative to features such as weld-lines and biofouling. In the complex area, we implemented new large-scale planning routines so as to achieve full imaging coverage of all the structures, at a high resolution. We demonstrate our approaches in recent operations on naval ships.

Sampling-Based Coverage Path Planning for Inspection of Complex Structures

We present several new contributions in sampling-based coverage path planning, the task of finding feasible paths that give 100% sensor coverage of complex structures in obstaclefilled and visually occluded environments. First, we establish a framework for analyzing the probabilistic completeness of a sampling-based coverage algorithm, and derive results on the completeness and convergence of existing algorithms. Second, we introduce a new algorithm for the iterative improvement of a feasible coverage path; this relies on a samplingbased subroutine that makes asymptotically optimal local improvements to a feasible coverage path based on a strong generalization of the RRT* algorithm. We then apply the algorithm to the real-world task of autonomous in-water ship hull inspection. We use our improvement algorithm in conjunction with redundant roadmap coverage planning algorithm to produce paths that cover complex 3D environments with unprecedented efficiency.