Crane Vessel Research Articles

Dynamic Analysis of Crane Vessel and Floating Wind Turbine during Temporary Berthing for Offshore On-Site Maintenance Operations

With the increased scale and deployment of floating wind turbines in deep sea environments, jack-up installation vessels are unable to conduct maintenance operations due to limitations in water depth. This has led to the recognition of the advantages of floating cranes in offshore maintenance activities. However, the dynamic coupling between the crane and the floating wind turbine under wave and wind action can result in complex responses, which also relate to complex mooring configurations. The ability to maintain stability during maintenance operations has become a primary concern. In order to address this issue, a method of connecting a floating crane with a floating wind turbine is proposed, simulating the berthing of a floating offshore wind turbine (FOWT) to a crane. Thus, a systematic comparison was conducted with frequency- and time-domain simulation using ANSYS-AQWA software. The simulation results demonstrated the feasibility and dynamic efficiency of this novel berthing approach. Connecting the crane vessel to a floating wind turbine significantly reduced the crane tip movement. Simulations showed that the crane tip movement in the X-, Y-, and Z-directions was reduced by over 30%, which implies that it may be feasible to conduct offshore on-site maintenance operations for the FOWT by using floating crane vessels if the two bodies were properly constrained.

Iron Powder as a fuel on Service Vessels

This paper investigates the feasibility of iron powder energy generation systems on board a semi-submersible crane vessel. This is done using a design model that integrates design information and a simulated mission profile to determine a hybrid iron powder setup split. This setup is then placed within a set of vessel designs to calculate a base level feasibility looking at the draft, stability, and emissions decrease. For those concepts that were technically feasible, the new hybrid iron powder setup contributed to a reduction of CO2 up to 25-50% and a reduction of NOx emissions between 15-50%, depending on the mission profile.

A comparative analysis of side and stern installation of a monopile lifting operation using a heavy lift crane vessel

This paper compares two 2XL monopile installation methods: at the leeward side of the heavy lift crane vessel and in the recess at the stern of the vessel. The multi-body system of the vessel, monopile, crane, and mission equipment induces interaction and resonance behaviour. Operational limits are assessed at the crane tip and pile gripper during upending and lowering of the monopile. Stern installation provides a larger operability window during upending compared to side installation. During the lowering stage, the operability depends on the monopile submergence: side and stern installation provide a comparable operability. Considering both stages, stern installation shows promising results.

The Effect of Spare Part Procurement and Inventory on the Smooth Operation of Floatingcrane Vessels at PT MUTIARA JAWA

PT Mutiara Jawa is engaged in transshipment which handles loading and unloading of coal. So that the timeliness of unloading must be considered because the company must have special attention to these activities to prioritize its efforts in providing quality loading and unloading services. Based on the data, the problems that exist discuss the procurement and supply of ship spare parts for ship operations. The purpose of this study is to find out how much influence and relationship the procurement of spare parts has on the smooth operational activities of floating crane vessels. In this study found the results of data from the influence and relationship of spare part procurement to the smooth operation of floating crane vessels.

Implementation of interactive control of a crane ship model in MATLAB/Simulink environment

The increased demand for performing crane ship modeling has led to the necessity for fast and accurate numerical experiments. This paper presents an approach for creating a numerical model of a crane vessel with a suspended load that allows for real-time control of crane parts. The model is developed in the MATLAB/Simulink environment, which makes it possible to extend it further to the user's needs. The authors describe the approach to the calculation of wave-induced ship motions, presents the Simulink block model and describes the features encountered during the simulation process. The possibility of real-time control of the position of crane parts is also shown, keeping the calculation speed of the ship hydrodynamics.

A Code-to-Code Comparison for Dynamic Modeling and Response Analysis of Offshore Wind Turbine Blade Mating Process

Abstract Offshore wind turbine blade installation using jack-up crane vessel is a challenging task. Wave- and wind-induced loads on the installation system can cause large relative motion between the blade root and the hub during the mating process. Currently, several numerical tools are used to analyze such critical global motion responses; however, the industry suffers from lack of experiments and full-scale measurements to validate the accuracy of these results. Consequently, a code-to-code comparison exercise becomes critical as it allows comparing different numerical tools for reliable prediction and verification of results. In the present article, a numerical model of the offshore wind turbine blade mating process using a jack-up crane vessel is developed in orcaflex, and a code-to-code comparison is performed against sima; both these tools are immensely used in the industry for modeling marine operations. Different comparisons are made between both the tools such as: (1) modal analyses of the jack-up vessel and the blade lifting gear, (2) time-domain analysis of the fully coupled installation vessel-crane-blade system, and (3) a comprehensive sensitivity study based on different seed numbers and simulation periods. The results of the study show a good agreement between both the tools with a deviation of less than 3% in terms of modal analysis and less than 5% variation in time-domain results. Further, the article provides modeling guidelines for the industry practitioners that heavily rely on both the tools for modeling marine operations.

Dynamic Analysis of Full-Circle Swinging Hoisting Operation of a Large Revolving Offshore Crane Vessel under Different Wave Directions

Waves have an important influence on the motion performances of offshore crane vessels. The floating crane vessel in waves gives rise to the motion of the lifted object which is connected to the hoisting wire. Based on the geometric parameters of a revolving offshore crane vessel, combined with the specific process of the floating crane vessel at work, a model of the offshore crane vessel under full-circle swing hoisting has been established by OrcaFlex. With the change in wave direction, the dynamic response of the system is made and the impact force between the support vessel and the hanging object and the tension of the crane wire under different wave directions is obtained. At the same time, the minimum impact forces between the support vessel and the hanging object and the tension of the crane wire and their wave directions are obtained. According to the calculated result, the optimal design of the full-circle swing hoisting operation of large revolving offshore crane vessel has been determined.

Dynamic Analysis and Extreme Response Evaluation of Lifting Operation of the Offshore Wind Turbine Jacket Foundation Using a Floating Crane Vessel

The jacket is the most widely-used fixed foundation for offshore wind turbines due to its superior strength and low installation cost in relatively deep waters. Floating crane vessels are commonly used to install jacket foundations. However, the dynamic coupling between the jacket and the floating vessel might generate complex dynamic responses under wave action. The complexity of the multi-body system requires comprehensive time-domain simulations and statistical analysis to obtain reliable results, especially for the evaluation of the operational safety of offshore lift installations of a jacket foundation. In this context, this study performs numerical simulations and statistical analyses to predict the extreme responses and the preliminary allowable sea states for guiding the lowering operation of a jacket using a floating crane vessel. First, ANSYS-AQWA is used to obtain the hydrodynamic coefficients of the vessel in the frequency domain. A nonstationary time-domain simulation of jacket lowering with winches is performed to identify several preliminary critical vertical positions of the jacket from the time series in an irregular wave. The extreme responses of a target probability are evaluated by the extreme distribution model after a large number of steady-state time-domain simulations of the critical vertical positions in irregular waves. The most critical vertical position is determined from three preliminary critical vertical positions by comparing the extreme responses. Eigenvalue analysis and spectrum analysis of the most critical vertical position of the jacket are carried out to find the natural periods of the system and the dynamic coupling characteristics between different components. The influence of wave direction, significant wave height, and spectrum peak period on the dynamic responses are also analyzed in the most critical vertical position. Furthermore, the optimal wave direction is determined as the head sea. Preliminary allowable sea states are derived by comparing the calculated dynamic amplification coefficient with the defined operational criteria.

Nonlinear fault-accommodation thrust allocation for over-activated vessels using artificial neural network and multivariate analysis

This study seeks to develop a better understanding of the thrust allocation process of over-actuated marine vessels. A two-stage analysis framework is proposed for thrust allocation when thrusters experience faults. In Stage-I, sequential quadratic programming with a multi-start mechanism (SQP-MultiStart) is used to find the optimal solution to the nonlinear fault-accommodation thrust allocation problem. According to the solution feasibility, another two different optimization models are considered in Stage-II. A newly developed meta-heuristic optimization approach, neural network algorithm (NNA), and SQP-MultiStart method are employed to find optimal solutions. Histories of decision variables and thrust allocation status are obtained. Self-organization mapping (SOM) and principal component analysis (PCA) are utilized to mine the hidden information in the thrust allocation. A deepwater pipe-laying crane vessel with 7 azimuth thrusters is selected to illustrate the analysis procedure. The features of thrust allocation are investigated and the effectiveness of the proposed framework is verified. Simulation results extend the understanding of the thrust allocation process and assist in choosing the thrust allocation model in different cases. The framework is suitable for fault-free and faulty cases. Neural network technique and multivariate analysis help to mine the knowledge about the thrust allocation performances.

Dynamic Analysis of Splash-zone Crossing Operation for a Subsea Template

Subsea templates are steel structures used to support subsea well components. Normally, offshore crane vessels are employed to install them to the target location on the seabed. Crossing the splash-zone during the lowering of a subsea template is considered the most critical phase during the installation due to slamming loads and needs to be studied to provide the operational weather criterion during the planning phase. In this study, dynamic response analysis has been carried out to evaluate the allowable sea states for the plash-zone crossing phase of the subsea templates. The numerical model of the lifting system, including the crane vessel and the subsea template, is firstly built in the state-of-the-art numerical program SIMA-SIMO. Then, dynamic analysis with time-domain simulations is carried out for the lifting system under various sea states. The disturbed wave field due to the shielding effects from the installation vessel is considered when calculating the hydrodynamic forces on the template. Statistical modelling of the dynamic responses from different wave realizations is used to estimate the extreme responses of various sea states. The application of the generalized extreme value distribution and Gumbel distribution in fitting the extreme responses is discussed. Moreover, the influence of the shielding effects from the vessel, as well as the influence of the changing size of the suction anchor on the hydrodynamic responses and the allowable sea states are studied.

Assessment of allowable sea states for offshore wind turbine blade installation using time-domain numerical models and considering weather forecast uncertainty

Installation of offshore wind turbines, particularly blades, is challenging and should be executed within the allowable limit of sea states to ensure the safety and the efficiency of installation. During the execution phase where weather forecast will be used in the decision-making process, uncertainty in weather forecast is an important issue required to be dealt with. The purpose of this paper is to assess allowable sea states for offshore blade installation, with emphasis on both considering weather forecast uncertainty and using time-domain numerical models for installation response analysis. The general procedure is presented, which includes generation of the response-based alpha-factor αR (that is a reduction indicator reflecting weather forecast uncertainty) in the planning phase based on time-domain modelling and analysis of blade installation, and assessment of corresponding allowable sea states in the execution phase. Single blade installation by a semi-submersible crane vessel at the North Sea center is studied in this paper, and two typical limiting response parameters, namely the blade root radial motion and velocity, are considered. The αR factors correspond to these two limiting parameters are first generated respectively, based on the forecast uncertainty quantification of sea states, the quantitative assessment of system dynamic responses and the estimation of their characteristic values through probabilistic analysis. The characteristic values of the responses that correspond to a certain exceedance probability (10−2 or 10−4) could be generated with and without the consideration of the weather forecast uncertainty. Finally, the allowable sea states with and without the weather forecast uncertainty are obtained when the characteristic value reaches the allowable response limit. These could be further used to identify overall workable weather windows for the offshore blade installation and support operation decision-making. Results indicate that there is a significant difference between the allowable sea states with and without considering weather forecast uncertainty. As the forecast lead time increases, the allowable sea states gradually decrease. Hence, it is necessary to apply αR to involve and quantify the effect of weather forecast uncertainties on operations. Moreover, since time-domain simulations are used for dynamic response analysis of the installation system, the effect of statistical uncertainty related to the use of a limited number of simulations to derive the characteristic response values is also investigated and is found small.

On Training Data Selection in Condition Monitoring Applications—Case Azimuth Thrusters

Machine learning techniques are commonly used in the vibration-based condition monitoring of rotating machines. However, few research studies have focused on model training from a practical viewpoint, namely, how to select representative training samples and operating areas for monitoring applications. We focus on these aspects by studying training sets with varying sizes and distributions, including their effects on the models to be identified. The analysis is based on acceleration and shaft speed data available from an azimuth thruster of a catamaran crane vessel. The considered machine learning algorithm was previously introduced in another study suggesting it could detect defects on the thruster driveline components. In this work, practical guidance is provided to facilitate its implementation, and furthermore, an adaptive method for training subset selection is proposed. Results show that the proposed method enabled the identification of usable training subsets in general, while the success of the previous approach was case-dependent. In addition, the use of Kolmogorov–Smirnov or Anderson–Darling tests for normal distribution, as a part of the method, enabled selections that covered the operating area broadly, while other tests were unfavorable in this regard. Overall, the study demonstrates that reconfigurable and automated model implementations could be achievable with minor effort.

Hydrodynamic characteristics of the crane vessel-three-bucket jacket foundation coupling hoisting system during the process of lowering

In the present study, a novel three-bucket jacket foundation with air-cushion launching technology is proposed. Through the theoretical analysis and commercial hydrodynamic software Moses, a crane vessel-three-bucket jacket foundation coupling hoisting system is established, and time-domain calculations are performed accordingly. Moreover, based on statistical information of the actual sea conditions in a certain sea area throughout the year, the corresponding permissible sea conditions for the construction of the sea are calculated to provide technical guidance for practical engineering. Furthermore, the hydrodynamic characteristics of the crane vessel, the motion response of the coupling hoisting system and variations of the cable tension under different configurations and wave directions are obtained. It is found that the vibration frequencies of the crane vessel and the foundation are the same, and the phase is maintained at 180°. It is considered that when the foundation is located at the stern of the vessel and encounters transverse waves, resonance occurs between the crane vessel and the foundation, which should be avoided in actual construction.

THE CLASSIFICATION OF PIPE-LAY VESSELS AND HEAVY-LIFT CRANE VESSELS

Pipe-lay vessels, heavy-lift crane vessels and dual purpose heavy-lift and pipe-lay vessels are distinct in many ways from other types of ships or offshore units. The unique functions that these vessels carry out can impact directly on the overall safety of the vessel, the personnel on-board and the potential to pollute the environment. This paper outlines some of the hull and machinery safety assurance considerations for classification and design pertinent to pipe-lay and heavy-lift operations. The considerations that are discussed in this paper include the implications of classing the vessel as a ship or an offshore unit; the interaction between classification and marine warranty; general arrangement; station-keeping; structural assessment and the interaction between safety critical systems. Specific hazards for pipe-lay vessels and their use of chemicals on-board are also discussed.

Experimental Study and Numerical Analysis of Crane Operability in Floating Crane Catamaran

Crane vessel is a floating structure equipped with accommodation facilities and one or more cranes to do work in the field. Crane vessel continue to be developed so that they can lift large structures and operate safely in certain environmental conditions. The work that is usually done by crane vessel is to lift heavy or light loads from land to ship, from ship to land, from ship to sea, from sea to ship, and from ship to ship. The process of moving loads carried out by a crane vessel usually called the lifting process. In carrying out its work, a crane vessel is limited by certain criteria for safety reasons. One of them is the criterion that limits the heave motion at the end of the crane boom and roll and pitch motion of the crane vessel. In this final project, an experimental study and numerical analysis of crane operability were carried out on catamaran hulled crane vessel. Experiments were carried out at the Balai Teknologi Hidrodinamika BPPT and numerical analysis using the MOSES software. According to the criteria used, namely Operational Limitations of Offshore Crane Vessels, cranes on floating crane catamaran have the highest operability when the vessel heading is 0 o to the direction of the incoming waves, which is up to H s 1.45 m.

Decommissioning Plans for Fixed Offshore Platforms: A Brief Revision

Brazil began to explore its seas in the 60’s of the XX Century looking for petroleum. This journey began in the Northeast and the first oil field produced offshore was the Guaricema Field, in the State of Sergipe. During the 70’s, Petrobrás found oil in the Campos Basin, between the States of Espírito Santo and Rio de Janeiro, that became the most important oil province in Brazil until the discovery of the Pre-Salt province, in the Santos Basin. As these fields are producing for a long time, many of them are already completely depleted or their production is in way of to be not commercial anymore, and their facilities need to be decommissioned. This review of decommissioning practices of fixed offshore platforms carried out worldwide has focus on the removal of topside with special vessels designed for this purpose or with conventional methods (crane vessels + barge). It will show the benefits of using specialised heavy lift vessels to remove the topsides and move it to shore for dismantling / recycling / reuse / disposal. The cases for study were the successful decommissioning projects in the North Sea: Brent B/D, Valhall QP, Viking, Curlew, Eider A, Golden Eye and Leman, Iwaki-Oki, Halfweg Q1, Yme and Ninian North.

Methodology for developing a response-based correction factor (alpha-factor) for allowable sea state assessment of marine operations considering weather forecast uncertainty

The concept of the alpha-factor, a correction factor on the significant wave height limit, was developed by DNV to consider the effect of weather forecast uncertainty in planning and executing marine operations. In this paper, a new defined response-based correction factor, called the response-based alpha-factor αR, is proposed to account for the forecast uncertainty of both significant wave height Hs and peak wave period Tp, and quantify their effect on dynamic response of offshore structures. A general methodology for developing αR for the use in assessing allowable sea states for marine operations is presented, with emphasis on considering the effect of the weather forecast uncertainty. It consists of uncertainty quantification of the sea state forecast, statistical analysis of dynamic responses of the coupled system for marine operations and allowable sea state assessment using response-based criteria. Based on the methodology, αR for an operation can be derived, in terms of the ratio between the characteristic values of the operational limiting response parameter in the condition with or without the weather forecast uncertainty. Then, the allowable sea states can be assessed in terms of the forecast lead time, to include the effect of the weather forecast uncertainty on the operation decision-making. The workable weather windows can finally be identified and selected through a comparison between the allowable sea states and weather forecasts in the execution phase. Followed by the detailed description of the proposed methodology, a case study dealing with single blade installation for offshore wind turbine using a semi-submersible crane vessel is conducted. The crane tip motion is regarded as the operational limiting response parameter to illustrate the methodology based on frequency-domain response analysis approach. The uncertainty in sea state forecasts generated by two machine learning-based forecasting methods is considered in this paper. Results show that in addition to the forecast uncertainty of Hs, that of Tp also requires to be addressed for marine operations with floating structures (such as the semi-submersible crane vessel). The proposed method provides an efficient way to incorporate the weather forecast uncertainty into the allowable sea states assessment for marine operations. The obtained allowable sea states can provide a good reference for the decision-making of the operation in the execution phase.

Changes in Underwater Noise and Vessel Traffic in the Approaches to Halifax Harbor, Nova Scotia, Canada

Over the past two years, researchers at Fisheries and Oceans Canada have been running an acoustic monitoring project at multiple study sites throughout Nova Scotia, Canada to investigate baleen whale presence and levels of underwater noise. At the onset of the COVID-19 pandemic, a passive acoustic monitor (PAM) was in place in the study site located in the approaches to Halifax Harbor, a major Canadian port. This provided a unique opportunity to determine if changes in vessel noise levels occurred after pandemic restrictions were put in place. To investigate this, we analyzed and compared acoustic data collected from March 28 to April 28 and August 6 to October 22 in both 2019 and 2020. We also investigated possible changes in vessel traffic from February 1 through April 28 and July 1 through July 28 in 2019 and 2020 using terrestrial-based automatic identification system (AIS) data provided by the Canadian Coast Guard and cargo information provided by the Port of Halifax. The acoustic data were analyzed in 1/3 octave frequency bands. For the 89.1–112 Hz frequency band, we found an 8.4 dB increase in the daily minimum sound pressure level (SPL) in April 2020 compared to April 2019 due the presence of a large crane vessel stationed near the mooring site. For the period of August to October, we found an approximately 1.7 dB reduction in the same metric from 2019 to 2020. The most noticeable change in vessel composition was the dramatic decrease in the number and occurrence of pleasure craft in July 2020 compared to the same period in 2019. While this analysis looked at only a single PAM and a limited amount of data, we observed changes in sound levels in the frequency band known to be associated with shipping as well as changes in vessel traffic; we conclude that these observed changes may be related to pandemic restrictions.

Model-free anti-swing control of complex-shaped payload with offshore floating cranes and a large number of lift wires

Being one of the most commonly used offshore operations, offshore lifting operations become increasingly challenging due to the gradually growing size and weight of payloads. The research on automatic control in lifting operations, e.g., anti-swing control and heave compensation, only considers simple-shaped payloads, such as lumped-mass rigid points. However, the sizes and orientations of many structures cannot be neglected. To lift heavy and large-scale payloads, larger and higher cranes are required. Alternatively, it is possible to share the total loads by enhancing the number of lift wires that may limit the tension on each lift wire. However, the complicated configuration introduces significant complexity into the design of the automatic anti-swing algorithm, especially to the control allocation module. This paper performs a preliminary study on the anti-swing control of a complex-shaped suspended payload lift using a floating crane vessel and a large number of lift wires. Inspired by the knowledge of inverse dynamics and range-based localization, a general model-free anti-swing control scheme is proposed. The controller has a simple form without considering state–space equations, but it can reduce the pendular payload motion regardless of the detailed system configuration. An offshore wind turbine tower–nacelle–rotor preassembly installation using floating crane vessel is adopted as a case study to verify the performance of the proposed control strategy.

Assessment of operational limits: Effects of uncertainties in sea state description

For operations dominated by waves, operational limits are normally expressed in terms of allowable sea state parameters, such as the significant wave height (Hs) and spectral peak period (Tp). The allowable sea states need to be assessed in the planning phase of the operations. Different sources of uncertainties (including weather forecasts, wave spectral model and numerical models) should be accounted for in the allowable sea states to provide safety margins. This study focuses on assessment of the operational limits (in terms of Hs and Tp) considering the uncertainties associated with the sea state descriptions used in the numerical analysis. The aim is to demonstrate the effects of simultaneous description of wind sea and swell sea accounting for their different directional spreading and directions of propagation. A case study using lifting operation is chosen to address these uncertainties in the allowable sea states. To illustrate the results, two types of floating crane vessels, mono-hull and semi-submersible are employed in the case study. Operability analysis by using these vessels are performed and compared using NORA10 hindcast data for a site in the Barents Sea.