Solitaire is a DP positioned pipelay vessel capable of laying pipe up to 3000 meters. Currently, Solitaire is more than 40 years old. Although it has been upgraded multiple times, it has been identified that certain improvement can be achieved by retrofitting just the aft of the vessel. The purpose of the research is to evaluate the feasibility of improving Solitaire by retrofitting it with a new aftship, by exploring the different design possibilities, including the different stinger support configurations. To this end, an analysis of alternatives has been done and the preferred options have been implemented into a concept design. The use of Systems Engineering (SE) has been motivated by the need to establish a clear structure to guide the design due to the complexity of the problem. This methodology allows to keep a good overview of the requirements and constraints involved in the design. An operational analysis was carried out to identify the operational deficiencies of the design. This lead to four main areas of improvement. i.e, Longitudinal strength, Stinger and Stinger handling system (SHS), Resistance and Deck space. By addressing these operational deficiencies, the operational time of the vessel can be improved. Either by reducing the theoretical peak cycle time, decreasing the downtime or a combination of both. Based on the operational analysis a set of requirements has been compiled and a functional definition of the design has been made. With all the insight obtained through the operational analysis, the design requirements and the functional definition; an analysis of alternatives has been carried out. For each of the operational deficiencies, multiple alternatives are analysed. Local optima are found for each of the deficiencies although, if each of these local optima is implemented in the design, the global performance of the vessel is compromised. Therefore, a holistic design is proposed to integrate all the solutions into one preferred concept design. Overall, the findings of the research suggest that the retrofit of the aft is technically and economically feasible. Nevertheless, a design validation needs to be carried out to better quantify the total improvement of the new design.

From shallow to deep water, from the well to the ship, from the offshore field to shore or between countries, many kilometres of offshore pipelines for transportation of hydrocarbons (oil and gas) have been installed over the last decades. Allseas’ Tog Mor is a shallow water pipelay barge capable of laying pipes up to a water depth of 25 meters. Currently, Tog Mor is more than forty years old and is due for replacement. Therefore, Allseas has considered to replace Tog Mor with a new shallow water pipelay barge. However, it is unclear whether the current barge is optimised for pipelaying since it is designed for crane supported purposes. The aim of this research is to give insight into vessel properties which determine the pipelaying performances and to define a set of design requirements for the new shallow water pipelay barge, Tog Mor 2.0. To define the requirements of Tog Mor 2.0, the principles of Systems Engineering are followed. Based on the operational analysis, the performances of Tog Mor can be improved by a reduction of the theoretical peak cycle time, optimisations of the pipelaying process and a reduction of downtime. The output of the operational analysis in combination with the principles of pipelaying results in potential bottlenecks. Those performances and potential bottlenecks were the input of the functional definition of Systems Engineering. The aim of this functional definition is to allocate functions to systems and to prioritise the design focus point in terms of functions. Those functions were translated into hardware components and integrated in the total design. Due to the inversely proportional relationship of the number of production days and corresponding production costs, an increased number of stations and lay speed do not have an advantage in terms of costs. In order to reduce the theoretical peak cycle time, the specifications of the functional equipment are improved and the need of buoyancy modules is reduced. Less need of buoyancy modules is achieved by the increased capacity of the tensioner (two tensioners of 100 ton each) and an inner stinger. The pipelaying process is optimised by free deck space, a higher level of redundancy of the functional equipment and new technologies of equipment. The level of redundancy in combination with the improved workability results in a reduction of downtime. Those improvements results in a final concept design which proposes a barge with an off-centre firing-line of five stations (three welding stations, one testing & grit blasting station, one coating station). As a result of an improvement of each individual function and the interactions among those functions, an improvement of 30% in terms of theoretical minimum peak cycle is achieved by an optimisation of the pipelaying process and potential bottlenecks. A reduction of the peak cycle time, an optimised pipelaying process and a reduction of downtime percentages results in an improved overall performance of Tog Mor 2.0 compared to the current Tog Mor.

To reduce global warming and air pollution, the maritime industry is searching for solutions to reduce fuel consumption. This thesis focuses on the reduction of generator running hours and fuel consumption of Dynamically Positioned (DP) vessels. In this ship type, redundancy of the power generation system is regularly achieved by running on one generator more than strictly necessary in every engine room. Thereby, these vessels make superfluous running hours and unnecessary fuel consumption. Previous research in this field focused on installing a hybrid system in every separate engine room to replace this redundant running generator and achieve the power generation redundancy by a battery which is temporarily used in case of a generator failure. Since DP vessels normally operate on two separate engine rooms for safety, this results in two separate hybrid systems, i.e. a double-battery hybrid system. To reduce investment costs of a hybrid DP vessel, this thesis concentrates on finding a power management strategy that allows a single hybrid system to be installed on board, which is only connected to one of the engine room grids in case of a generator failure. A single-battery hybrid system cannot be connected to both engine room grids continuously -in contrary to the double-battery hybrid system- because this would cancel the independence of the separate engine rooms. Therefore, in the single-battery hybrid system, no back up power is present in case of an increase in power demand in one of the engine rooms. In present DP vessels, this back up power is supplied by the redundant generator. When using a double-battery hybrid system, this back up power is supplied by the continuously connected hybrid system. Therefore, for a single-battery hybrid system, the starting control decision algorithm of the power management system (PMS) should decide on starting an additional generator prior to a rise of the power demand. Two methods for this starting decision algorithm were tested. Firstly, a mathematical-statistical method using a mathematical model for DP load forecasting and a statistical model for pipe laying load forecasting was tested. This model was found not to work properly. Secondly, a multiple linear regression model that predicts the height of power peaks based on environmental parameters like wind and waves was tested which was found to work appropriately. To assess the feasibility of using either a double-battery hybrid system in combination with a simple starting decision algorithm, or a single-battery hybrid system in combination with a smart starting decision algorithm, these two hybrid system options were compared to the current situation that uses a redundant generator in every engine room. These three system options were compared in terms of investment costs, fuel consumption, generator running hours, planned maintenance costs, and reliability. For this comparison, the DP pipelaying vessel Pioneering Spirit was used as a case vessel. To find the investment costs, a hybrid system was designed for this purpose. To find the fuel consumption, generator running hours, and planned maintenance costs, full year time domain simulations of the hybrid systems in operation were performed using measured power demand data from the case vessel during pipelaying. For this analysis, a mathematical model of the power generation system was used. The reliability assessment of the different systems was performed using fault tree analysis. The single- and double-battery hybrid systems both show a significant fuel consumption reduction of 8.4 and 9.0% respectively. When also taking into account the investment costs, generator maintenance cost reduction, and battery depreciation, the payback time of these hybrid systems is 0.9 and 1.7 years respectively. The difference in payback time is mainly caused by the difference in investment costs between the single- and the double-battery hybrid system. For a single-battery hybrid system for DP vessels, a multiple linear regression model based starting decision algorithm works appropriately. However, although the multiple linear regression model based starting decision algorithm was tested positively in simulations using the available power data, in case of an unforeseen power peak that was not related to one of the input parameters of the regression model, the power generation system lacks back up power. Therefore, the reliability of the single-battery hybrid system is insufficient when using it for DP applications. Especially when taking into account the minor absolute difference in payback time, for the replacement of the redundant generators in DP vessels, the robust and simple double-battery hybrid system is preferred over the small and smart single-battery hybrid system.

Allseas Group S.A. is a leading offshore contractor in the field of pipeline installation, heavy lifting and subsea construction. One of Allseas’ vessels is Pioneering Spirit. The main activities of Pioneering Spirit can be subdivided into pipeline installation, topside installation/removal and jacket installation/removal. The equipment of the first two activities has been successfully put into operation. The equipment to install and remove jackets (Jacket Lift System (JLS)) is currently under development. The mechanism to upend/tilt-over the Jacket Lift System is the subject of this graduation project. The design challenge of Pioneering Spirit’s Jacket Lift System is to install or remove a jacket with a height of at least 70 meters and a mass of up to 20 000 mt (in air) in a single lift/operation. In this thesis project, an additional design solution has been investigated and developed. The objective was to investigate the feasibility and favourability of various principles and concepts to upend/tilt-over a jacket using Pioneering Spirit. Key topics in the development of the design solution were the controllability of the operation, the compatibility of the system in the current appearance of Pioneering Spirit’s, the complexity of the operation and the investments costs to construct, operate and maintain the system. The design solution found in this graduation project consists of a tilting system that rotates over the stern of Pioneering Spirit. The system is driven by a pushing system installed on the reinforced transverse frames on the aftdeck of Pioneering Spirit. The system must be movable to relocate the centre of gravity before upending or after tilting-over of the system. The system is controlled by two winch systems, one attached to the tip of the tilting lift beams (Derrick Hoist system, consisting of 10 winches) and the other to the upper pivot point of the pushing system (Upend/Tilt-over Mechanism, consisting of 8 winches). The system can be controlled in both rotational directions using the two winch systems. The tilting lift beams and pushing system are connected by means of a roller/slider connection. The maximum forces, stability and controllability of the system were checked with a coarse dynamic mathematical model. The natural frequency of the system with and without jacket appeared to be in the same frequency range as the excitation response spectra. This was solved by stiffening the system by increasing the effective diameter of the winch systems and by applying pre-tension. Subsequently, the system appeared to be possibly instable during the first/last 18 degrees of the tilting operation. This was solved by applying an auxiliary construction during the first/last 30 degrees of the tilting process. The maximum response amplitude of the system was calculated by means of a calculation of the maximum excitation in the frequency domain (regular waves) and for time series (irregular waves) for the positions in which the Jacket Lift System can be positioned and all incoming wave directions. The maximum response amplitude of the system occurs in beam waves when the system is positioned vertically. Although the maximum response amplitude of the system is small, mainly because of the stiffness, the maximum forces in the system are exorbitantly large. To give an indication, the maximum tension in the Derrick Hoist System is 4125 mt. At a certain moment in the tilting procedure, the entire mass of the Jacket Lift System (15 000 mt) and Jacket (20 000 mt) is applied to the pivot points at the stern of Pioneering Spirit. In general, the static forces deliver the greatest contribution to the total force. The maximum loads are considered feasible, although strengthening measures must be taken.