Supply Vessel Research Articles

Anatomic feature of the adjacent perforator fasciocutaneous flap of plantar and its clinical application

Objective To study the anatomic basis and its clinical effects of the adjacent perforator fasciocutaneous flap in planta. Methods From October, 2010 to December, 2017, the work was on two fronts:① The blood supply of the flap was studied by the dissection of 5 adult lower limbs which were perfused with red emulsion. Under the magnifying glass, the source of blood supply to the pedicle perforator fasciocutaneous flap near the foot was observed, and the caliber of perforating vessels was measured by vernier caliper. ② Methods based on the anatomic study, the adjacent perforator fasciocutaneous flap was designed to repair plantar defect. Eleven cases with defects in planta were treated with the flap including 5 malignant melanoma, 5 refractory wound and 1 pigmented nevus. The size of defects ranged from 1.5 cm×2.0 cm to 4.0 cm ×5.0 cm with the size of the flaps ranging from 7.0 cm×3.0 cm to 13.0 cm×7.0 cm. Results Anatomical studies showed that the supply vessels of the fasciocutaneous flap near the perforator of the plantar space were plantar medial arteries. The external diameter was greater than or equal to the 0.5 mm perforating number of about 7, the average outer diameter was (0.85±0.19) mm. The medial plantar artery emits multiple branches along the running direction and forms anastomotic branches in the arch of the foot to ensure the blood supply of the flap. Eleven cases of perforator fasciocutaneous flaps survived, including 1 case of distal necrosis of small area and healed after change dressings. The follow-up results during 6-24 months showed that all patients were walking normally, with full texture and no localized dull pain. Conclusion On the basis of the extent of diseases, projected the adjacent perforator fasciocutaneous flap, the wear resistance and abrasive resistance are improved resulted from flaps with similar skin texture of defects. The donor site can be closed directly without skin graft. It is an simple and reliable method to repair medium and small- sized plantar defects. Key words: Plantar; Perforator flap, fasciocutaneous flap; Applied anatomy; Repair

Various Aspects of Bollard Pull Tests and Analysis of Test Results

The static force exerted on a hawser at zero ship speed by a vessel, otherwise known as the bollard pull, is one of the key performance indicators of Tugs, Anchor Handling Tugs (AHTs) and Anchor Handling Tug Supply Vessels (AHTSVs). The value of bollard pull is considered critical as it defines the functionality and performance of the vessel. When a company decides on chartering a vessel, a definite prerequisite considered is the value of the bollard pull. The value may be obtained via three ways: calculations, model-testing, and full-scale trials. The latter is often used officially to certify the vessel's bollard pull rating, with the presence of the vessel's owners, surveyors, and any other third parties. The tests and trials follow a set of guidelines provided by classification societies but do not have a standardized set of rules. Therefore, disagreements often arise over the results of such tests and trials. Tests are often carried without any load cells measuring the shaft power to ascertain the brake horsepower (BHP). Simply, engine rpm/ rating is used to fix the 100% maximum continuous rating (MCR) which often in the range of 105–108% MCR. Some of the parties involved in certifying the correct bollard pull tests (BPTs) do not even understand what is all about the bollard pull. Everybody is looking for a higher figure for the bollard pull on the certificate when the reality is different. The author examines and discusses the broad spectrum of factors that affects the "true" value of the bollard pull and explains why such a standardized set of mandatory BPT and the trial code is deemed necessary. The author also presents some of the interesting BPTs data to show the differences in various ways of conducting BPTs. 1. Introduction The bollard pull (BP) is the zero speed pulling/pushing capability of a vessel, i.e., Tugs, Anchor Handling Tug (AHTs), Anchor Handling Tug/ Towing Supply Vessel (AHTSVs), trawlers, etc. It is considered as one of the key practical performance indicators of the above-mentioned vessels, measuring the usefulness of the vessel in a stranding scenario or in holding large vessels such as tankers or towing a rig.

CT features of hepatic epithelioid angiomyolipoma: differentiation from hepatocellular carcinoma in patients with noncirrhotic livers.

Hepatic epithelioid angiomyolipoma (HEA) shares some similarities with other hepatic tumors, such as hepatocellular carcinoma (HCC). Thus, establishing a definite diagnosis of HEA based on medical imaging is often difficult. In this study, we evaluated multiphasic computed tomography (CT) imaging to differentiate HEA from HCC in patients with noncirrhotic livers. We retrospectively analyzed the clinical and imaging data of both contrast and non-contrast enhanced CT scans from 25 patients with HEA and 50 patients with HCC in noncirrhotic livers. CT features, including lesion position, size, shape, interior content, border, enhancement degree, and enhancement pattern, were independently evaluated by two radiologists. Intratumoral blood vessels, peripheral supply vessels, the early display of the hepatic vein, peripheral abnormal perfusion, peripheral washout sign, pseudocapsule, and portal tumor thrombus were also evaluated. Next, we quantitatively analyzed difference within results of clinical and CT characteristics between the HEA and HCC groups. The number of female HEA patients is more than male (76% vs. 24%), with a mean age of 49.44±10.33 years (from 30 to 68 years). The majority (64%) of HEA patients were asymptomatic, without hepatitis (88%). On non-contrast enhanced CT, HEA mainly manifested as a round (92%), hypodense mass (100%) with little fat (12%) and rare complications, such as hemorrhage (4%) and calcification (4%). HEA all manifested as an intensely enhanced mass on contrast-enhanced CT. The differences between HEA and HCC were significant in the imaging characteristics of the early display of the hepatic vein (32% vs. 0%, P=0.000), intratumoral blood vessels during the nonarterial phase (36% vs. 8%, P=0.003), washout enhancement (52% vs. 86%, P=0.001), and prolonged enhancement (40% vs. 4%, P=0.000). Although HEA is an uncommon hepatic tumor, clinical and CT manifestation may be indicative. Clinical and CT characteristics including asymptomatic, non-hepatic, fat-deficient, early display of the hepatic vein, intratumoral blood vessels during the nonarterial phase and prolonged enhancement are selected to improve the recognition of HEA, supporting for a differential diagnosis from HCC.

Optimal design of a hybrid electric propulsive system for an anchor handling tug supply vessel

Hybrid electric propulsive systems (HEPSs) attract increasing research interest due to their environmental and economic merits. However, the design optimization of HEPSs with the single objective of fuel saving may result in increased greenhouse gas (GHG) emission and high cost. The present study proposes a multi-objective optimization method to obtain an optimal trade-off with respect to fuel consumption, GHG emission, and lifecycle cost. Due to high convergence in solving constrained multi-objective optimization problems, the non-dominated sorting genetic algorithm II (NSGA-II) is developed to explore an optimal design space. Performance tests are conducted on a real-time hardware-in-the-loop (HIL) platform. The hybrid diesel/battery/shore power system on an anchor handling tug supply vessel is considered as a study case. The results of the proposed NSGA-II are compared with those from a single-objective optimization pursuing minimum fuel consumption. The proposed method outputs designs that can significantly reduce GHG emission and lifecycle cost by sacrificing low fuel consumption when compared with that of single objective optimization. Furthermore, the HEPS designed by the proposed method exhibits advantages over the conventional propulsive system in terms of all the three aspects.

An Experimental Study of Ship Motions During Replenishment at Sea Operations Between a Supply Vessel and a Landing Helicopter Dock

Hydrodynamic interactions during Replenishment at Sea (RAS) operations can lead to large ship motions and make it difficult for vessels to maintain station during the operation. A research program has been established which aims to validate numerical seakeeping tools to enable the development of enhanced operator guidance for RAS. This paper presents analysis of the first phase of scale model experiments and focuses on the influence that both the lateral and longitudinal separations between two vessels have on the interactions during RAS. The experiments are conducted in regular head seas on a Landing Helicopter Dock (LHD) and a Supply Vessel (SV) in intermediate water depth. The SV is shorter than the LHD by approximately 17%, but due to its larger block coefficient, it displaces almost 16% more than the LHD. Generally, the motions of the SV were larger than the LHD. It was found that hydrodynamic interactions can lead to large SV roll motions in head seas. Directions for future work are provided.

Methodology to qualify marine electrical propulsion system architectures for platform supply vessels

Conventional diesel-electric propulsion systems in platform supply vessels (PSVs) use low-voltage AC (LVAC) supply-based architecture with multiple diesel-generators feeding busbars at 690 V, 60 Hz. The busbars distribute power to thruster motor drives via multi-pulse transformers and diode bridge rectifiers. Advancements in electrical power conversion and distribution technologies offer possibilities of AC or DC distribution at low/medium voltage (LV/MV) for reduced fuel consumption (FC), emissions, and equipment footprint. This study presents methodology to qualify propulsion system architecture for PSV application. Potential architectures, besides conventional one, are active front end (AFE) converter-based LVAC (690 V), MVAC (3.3 kV), LVDC (1000 V), and MVDC (5000 V). Performances of these architectures are assessed quantitatively based on FC, emissions, weight, volume, efficiency, and reliability. FC is estimated based on brake-specific FC data of diesel engine. NO x , SO 2 , and CO 2 emissions are assessed based on their emission factors. The weight, volume, and efficiency are estimated based on parameters of individual components. Reliability is assessed based on component failure data using DIgSILENT Power Factory. The architectures are ranked based on performance parameters using a Pugh matrix. The most suitable architecture for the target PSV is LVDC, followed by MVDC, LVAC with AFE, MVAC, and conventional LVAC.

Robust nonlinear control design for dynamic positioning of marine vessels with thruster system dynamics

Considering the dynamics characteristics of thruster systems for dynamically positioned marine vessels with model parameter uncertainties and unknown time-varying ocean disturbances, the dynamic positioning (DP) control problem becomes a mismatched nonlinear control problem. To solve this problem, a DP robust nonlinear control law is developed using the command filtered vectorial backstepping combined with a disturbance observer (DO) and an auxiliary dynamic system (ADS). The DO provides the estimates of mismatched compound disturbances induced by model parameter uncertainties and unknown ocean disturbances. The ADS addresses the effects of thrust saturation constraints. The command filtered vectorial backstepping obviates differentiations of intermediate control function vectors due to introducing command filters and compensates for filtering errors of intermediate control function vectors caused by command filters by means of designed dynamic systems. The developed DP control law is computationally simple and the DP control performance is improved. Under the developed DP control law, the positioning errors of vessels are made as small as desired and all signals in the DP closed-loop control system are uniformly ultimately bounded. The high-fidelity simulation results on a supply vessel validate the developed DP control law.

Development of the methodology of the choice of the route of work of platform supply vessels in the shelf of the seas

The object of research is specialized vessels servicing production platforms (SPV) in the shelves of the seas. One of the most problematic places is the need to improve the efficiency of specialized service vessels for transporting personnel, building materials and supplies to oil platforms in the sea shelves during the operation of platforms for oil production. In the course of the study, in order to improve the SPV operation of the production platforms, the method of variants and the routing of the operation of vehicles were used to develop the methodology. This allowed to improve the work of the SPV in the maintenance of production platforms, due to the reduction in the cost of voyage. The best way to organize the SPV operation in the maintenance of mining platforms in the Black Sea shelf is received. Namely, possible routes of SPV operation were compiled during the pendulum and group-delivery mode of operation, and the best way of SPV operation for the best route was determined according to the chosen criterion. The economic effect of the SPV operation on the selected route and method, which amounted to about 44 000 dollars for the voyage. This result is due to the fact that the developed methodology for the selection of the best version of the SPV has a number of features, in particular, it consists of successive stages: select route schemes for the organization of the work of environmental protection; compiled options for routes of SPV operation for each scheme; selection criterion is assigned; calculated performance of the vessels; the optimal route and scheme are selected according to the adopted optimization criterion. The developed methodology provides the determination of the optimal route and a variant of the operation scheme of the SPV, which provides the lowest value of the cost of transportation of 1 ton-km of cargo. Compared with similar known methods that are used in road transport, similar methods have not been used in the offshore oil business.

Optimal fleet composition and mix periodic location-routing problem with time windows in an offshore oil and gas industry: A case study of National Iranian Oil Company

This paper presents a new Mixed-Integer Non-Linear Programming (MINLP) model for a Supply Vessel Planning (SVP) problem. The traditional SVP, which is a maritime transportation problem, is developed to a Maritime Fleet Sizing Mix Periodic Location-Routing Problem with Time Windows (MFSMPLRPTW) by considering suppliers, location of onshore-base(s) and some real life aspects. The objective of this model is to decide the composition of fleets, optimal voyages, schedules and also the optimal location(s) for onshore-base(s) in such a way that the total cost is minimized and the needs of operation regions are fulfilled. The MFSMPLPRTW model is solved by an exact two-phase solution approach for both small and medium cases. Also, two meta-heuristic algorithms are used to solve the large-sized instances. In order to justify and show how the model and solution can lead to significant economic improvements for real life instances, a case study by the IOOC is considered, which is the only offshore oil and gas producer in Iran that has lots of installations and operation regions in the Persian Gulf and the Sea of Oman.

Energy efficiency at sea: Knowledge, communication, and situational awareness at offshore oil supply and wind turbine vessels

The increasing focus on energy efficient operation of vessels can be seen in both legislation and research. This paper focuses attention on the human factor influencing energy efficiency and explores the conditions for improving energy efficiency in working vessels taking situational awareness (SA) theory into consideration.The study builds on two cases: an offshore supply vessel for the oil & gas industry and an installation vessel for wind turbines. The study used qualitative methods based on 49 interviews with seafarers and onshore employees from the vessels and shipping companies.The study has identified that the energy efficiency of a ship is mainly influenced by legislation and the praxis formed on board. The results showed that the theory on SA is very a useful tool in explaining the factors affecting the energy efficiency of a vessel and the praxis.The study has shown that obtaining a more energy efficient operation is complex and depends not only on the officer on board the ship. The improvement of energy efficiency is possible, but there is a need to understand the complexity of the issue and to involve both the crew and the entire system around the ship, and to obtain a shared perspective of energy efficient operation. Furthermore, in order to improve energy efficiency in shipping companies, there is a need to support the seafarers in gaining more skills for operating the ship more energy efficiently; to do this the right way there is a need to create an understanding of the system by the authorities, ship owners and charterers.

From data to insight for a polar supply and research vessel

ABSTRACTFull-scale measurements on polar research vessels present an opportunity to advance the state-of-the-art in ship design through high-quality long-term measurements of environmental conditions and ship responses. The approaches, data analytics and synoptic results are presented for a comprehensive measurement campaign on a modern polar supply and research vessel, the SA Agulhas II. It is recognised that the real-time analysis and utilisation of such measurements could benefit the insightful operation and management of this vessel. To this end, the conceptual design of a monitoring and decision-aiding system is presented. Results indicate that significant potential beckons in the integrated acquisition, analysis and utilisation of full-scale ship-board measurements provided that this diverse data can be aggregated, analysed, visualised and interpreted in real time.

Dynamic positioning of ships with unknown parameters and disturbances

Robust adaptive control is proposed for the dynamic positioning (DP) of ships with unknown model parameters and unknown time-varying disturbances. Through representing the parameter uncertain ship motion mathematical model and the unknown time-varying disturbances as parametric forms, respectively, constructing an observer for handling disturbances, and using the adaptive vectorial backstepping, the DP robust adaptive control law is designed. The proposed DP control law achieves the global asymptotic regulation of positioning errors, while guaranteeing the global uniform ultimate boundedness of all signals in the DP closed-loop control system. Simulation results involving a supply vessel validate the proposed DP control law.

Robust supply vessel routing and scheduling

We solve the problem of tactical supply vessel planning arising in the upstream offshore petroleum logistics. Supply vessels deliver all the necessary materials and equipment to offshore installations from an onshore supply base according to a delivery schedule. The planning of supply vessels should be done so that their number is minimized and at the same time provide a reliable flow of supplies from the base. The execution of a weekly sailing plan is affected by weather conditions, especially in winter time. Harsh weather conditions increase the number of vessels required to perform the operations as well as the service times at the installations, and thus disrupt the schedule, leading to additional costs and reduced service level. We present a methodology for robust supply vessel planning enabling a trade-off analysis to be made between the schedules’ service level and vessels’ cost. The methodology involves the generation of multiple vessel schedules with different level of robustness using an adaptive large neighbourhood search metaheuristic and a subsequent discrete event simulation procedure for the assessment of the service level. To control the level of robustness we developed a concept of slacks and incorporated it into the metaheuristic algorithm.

Indirect load case estimation for propeller-ice moments from shaft line torque measurements

In order to estimate the forces exerted on ship propellers during ice navigation, the rotational dynamics of the propulsion system need to be accurately modelled. The blade measurements of ice loads on the propellers of ships during ice navigation is challenged by the harsh operating environment. Shaft line measurements are therefore performed inboard, and the required propeller loads are subsequently estimated through the use of a dynamic model and the solution of an inverse problem. The inverse problem is mathematically ill-posed and requires the determination of the ice-induced load on the propeller blade from shaft line measurements. The present study investigated full-scale torsional responses on the shaft line of a polar supply and research vessel during navigation through sea ice on a 68-day voyage between Cape Town and Antarctica. The vessel spent almost 11 days in ice with observed concentrations above 90% and a maximum thickness of 3 m. The aim was to evaluate the extreme ice-induced moments on the shaft line and thereby determine how sparsely published operational loadings compare to the design loads of an ice-going vessel. Ice-induced moments on the propeller were obtained from operational measurements through three previously published approaches to solving the ill-conditioned inverse problem. The regularization methods used included truncated Singular Value Decomposition, truncated Generalized Singular Value Decomposition and Tikhonov regularization. The maximum ice-induced external moment was found to be 941.5 kNm, which was just within the maximum allowed ice-induced torque on the propeller. The duration of ice impacts on the propeller ranged from 25 to 228 ms. A secondary peak was evident in torsional responses obtained from propeller-ice impacts which is thought to be a shear stress wave that propagates and reflects back in the shaft line. From the inversely determined ice-induced loads, the number of impacts, the duration, the shape and the damping of water on the propeller was identifiable. The results obtained were physically reasonable, indicating that the current methods are suitable for obtaining ice-induced loading on the propeller from shaft line measurements.

Dynamic lateral mass impact on steel stringer-stiffened cylinders

This paper focuses on the impact responses of large-diameter, thin-walled steel stringer-stiffened cylinders subjected to low-velocity mass impact. The impact scenarios employed in this study represent load actions as a result of supply vessel collisions with the main legs of floating offshore platforms and wind turbine structures. Two steel stringer-stiffened cylinders were fabricated and drop tests were performed at mid-span, using a rigid knife-edged indenter. The details of the experimental setup, test procedure and test results are reported in this paper. The experimental data appear to be useful for future benchmark studies. Numerical predictions of the impact response of the test models were simulated by means of the explicit solver of the finite element software package ABAQUS. The numerical predictions show a good agreement with the test results. The effect of the strain-rate hardening definition on the results is highlighted. Furthermore, parametric studies were conducted on stringer-stiffened cylinder models in order to clarify the progressive impact responses.

The periodic supply vessel planning problem with flexible departure times and coupled vessels

In upstream offshore petroleum logistics, periodic supply vessel planning plays an important role since it ensures the replenishment of offshore installations on a regular basis with all the necessary equipment and materials from an onshore base. The problem involves the determination of the fleet composition and of the vessel schedules over a given time horizon. We present an extended version of this problem involving flexible departures from the base and the possibility of coupling vessels by swapping their schedules. We propose a voyage-based model that can be solved exactly for small- and medium-size instances. For the solution of larger instances, we have developed an adaptive large neighborhood heuristic, which yields optimal or near-optimal solutions relatively fast on small- and medium- size instances. Its performance on larger instances is significantly better than that of alternative algorithms previously developed for the same problem.

Dynamic Positioning Capability Analysis for Marine Vessels Based on A DPCap Polar Plot Program

Dynamic positioning capability (DPCap) analysis is essential in the selection of thrusters, in their configuration, and during preliminary investigation of the positioning ability of a newly designed vessel dynamic positioning system. DPCap analysis can help determine the maximum environmental forces, in which the DP system can counteract in given headings. The accuracy of the DPCap analysis is determined by the precise estimation of the environmental forces as well as the effectiveness of the thrust allocation logic. This paper is dedicated to developing an effective and efficient software program for the DPCap analysis for marine vessels. Estimation of the environmental forces can be obtained by model tests, hydrodynamic computation and empirical formulas. A quadratic programming method is adopted to allocate the total thrust on every thruster of the vessel. A detailed description of the thrust allocation logic of the software program is given. The effectiveness of the new program DPCap Polar Plot (DPCPP) was validated by a DPCap analysis for a supply vessel. The present study indicates that the developed program can be used in the DPCap analysis for marine vessels. Moreover, DPCap analysis considering the thruster failure mode might give guidance to the designers of vessels whose thrusters need to be safer.

A decision tool for scheduling fleets of fuel supply vessels

Fleets of fuel supply vessels are used to provide ships anchored in ports different oil products. Demand is satisfied based on a pull system, where oil shipments are triggered by orders placed by customers and delivered on a specific agreed day. The aim of this paper is to develop a time-effective decision tool in order to aid the fleet schedulers to decide in a very short time (usually less than 10 min in the ships’ fuel supply business) if they will accept new orders, based on the fleet’s capacity and availability, and generate a feasible near-optimal operation schedule. The tool was tested in a small Hellenic oil company and the empirical evaluation is presented.

The detection of wave slamming from vibration measurements on a polar supply and research vessel

The SA Agulhas II is a polar supply and research vessel, which operates in the stormy Southern ocean and icy Antarctic waters. She is predisposed to problematic stern slamming. Twelve accelerometer channels from a full-scale vibration measurement system were used to capture measurements of wave incidence on the main deck close to the water line. An automated slamming detection and classification algorithm is proposed to extract slamming incidents from expansive full-scale data. This method is based on image processing of scalograms which are produced by continuous transforms, using the Morlet wavelet. Slams are classified based on the time of incidence. It is shown that high crest factor stern slamming occurs as often as twice per minute.

Математическое и имитационное моделирование электропривода с преобразователем частоты нефтегазового оборудования

Developing offshore hydrocarbon fields is nowadays a primary objective of power engineering. To develop hydrocarbon fields, one uses floating drilling rigs and drilling vessels, icebreakers, supply vessels, transport vessels (tankers and gas carriers), and submarine pumping complexes. When designing high-voltage electric drives with frequency converters, multiple interrelated studies are carried out using mathematical and simulation models, whereby calculation accuracy and the properties of the final product depend on the quality of such simulation. Refined mathematical models are a must if modeling and calculations are to be sufficiently accurate. Mathematical and simulation modeling of electric drives, as well as computational analysis thereof are becoming ever more relevant as engineers have to design more and more power facilities for oil-and-gas fields. We herein demonstrate an algorithm for simulation modeling of stand-alone three-level electric drive inverters, which includes analysis of such drive’s structural diagram, assumption-making, generating an equivalent electric drive diagram, describing the drive mathematically, synthesizing a modulation algorithm, and compiling simulation models. Our studies have shown the effect that resistance parameters and the inductance of motor chokes have on the output voltage quality of a stand-alone inverter. We have also studied how switching frequency of a stand-alone inverter affects distortions in the output voltage and current. We additionally give recommendations on how to select motor chokes.