One of the main methods for estimating air pollutant emissions from ships is the method developed by Carlo Trozzi, which was later accepted and recommended by the European Environment Agency in its air pollutant emission inventory guidebooks. Consequently, it has become the most commonly used methods for making inventories of air emissions in the shipping industry and for predicting future trends. The method and its equations use emission factors to calculate the emission of air pollutants from ships. Emission factors are calculated depending on fuel consumption or main engine power; results are given for different year of manufacture and engine speed. This paper presents the measurement of air pollutant emissions and some other parameters on marine engines operating in different conditions. The measured values are calculated to obtain values which will enable the next step, the comparison with the emission factors in the latest guide of the European Environment Agency on the inventory of pollutant emissions.

This paper is presenting a solution for simplifying shore maintenance service teams scheduling procedure in the maritime industry. Shore maintenance service teams scheduling procedure in the past required either advanced mathematical knowledge in the area of the queueing theory or adequate computerized software for the calculation. That action in the past was usually outsourced; companies did not have personnel capable of solving the queueing theory nor the software needed for the calculation. The solution, presented in the paper, enables in-house scheduling of the shore maintenance service teams using only basic knowledge of the theory, without the use of the specially designed software. The scheduling is performed using a simplified Excel template for Queueing theory, inserting the data from ship's Computerized Planned Maintenance System. The Excel template, after filling the data, determines the optimal number of teams for the fleet and performs the calculation according to the desired or optimal service level. Simplified Excel template for Queueing theory cut the costs for the calculation and scheduling enabling additional savings in the industry.

Calculation of torsional vibrations is essential in the early phase of the design of any ship propulsion system, after selection of shafting diameters in accordance with the Classification Rules. Later on, during ship trials, the calculation shall be validated by measurements on board. The calculation results depend upon inertial moments of actual masses, stiffness of shafting components, damping in the actual shafting components, as well as the excitation forces and moments exerted by the propulsion engine(s) and the propeller. Inertial moments and stiffness can be determined with no ambiguities. However, this is not the case with either the damping, or the engine excitation. Actually, during validation on board the calculation supposed damping is the main influential factor to be verified. The aim of this paper is to present and compare several models to define and compare damping definitions in the the torsional vibrations calculation (Frahm's model, Archer's model, physical damping, magnification factor, etc.) in a systematic way, to enable designers to correctly apply the selected damping model. Further on the engine excitation may be expressed by means of cylinder pressures or tangential forces to the cranks. The essentials of the two models and the procedure to convert one excitation model into another one are also presented. The application of the presented damping and excitation models is presented on an actual ship propulsion system and conclusions drawn.

This paper analyzes the shipowner’s role in the development process of ship’s computerized planned maintenance system database, paying specific attention to his/her impact on database quality grades resemblance equalization. The paper describes the database development process from the realization that the database is needed to the installation on board vessel, and all shipowner’s and developer’s actions in the process. The computerized databases of five shipping companies were tested using questionnaire developed for this purpose. The evaluation results are shown in several tables to facilitate overview and comparison of data. The paper provides the data of office user’s workload with regard to the administration and correction of data besides database quality grades: that data serves to portrait the relation between data quality in the databases and importance given to the process of development and maintenance of the databases. The analysis of the results yields numerical values as indicators of shipowner's input on the resemblance of grades of both scenarios and on the database quality grades resemblance equalization. The conclusion shows how the shipowner affects the ship's computerized planned maintenance system database and what actions should be performed to obtain the final product (database, i.e. data in the database) as good as possible and, thus, maintenance of the ship and the whole system. The expected results of the paper are:- To analyze in detail the database ordering and development process,- To pinpoint controlling areas for the database quality,- To analyze the shipowner’s impact on the database quality grades resemblance equalization.

The possibility of interval extension between two dry docking is alternatively offered to the shipowners by classification societies. Although, for now, such a possibility is limited only to certain types of ships, a significant shift has been accomplished in accordance with today's technical and technological capacities. It is quite clear that not all shipowners will accept this option, as either five-year or even mid-interval might suit them well. The option introduces an economic benefit, but requires additional preparation to withstand the full interval without negative consequences, primarily related to the protection of underwater part of the hull. The relationship of economic benefits and the cost of investment to successfully pass the complete period gives a clear view to the shipowner for the decision of accepting an extended dry docking period between two consecutive dry dockings. This paper is presenting one of the approaches to calculate feasibility of prolonging dry docking interval. Calculation example represents an economic indicator, crucial for shipowner’s decision to accept prolonged dry docking interval. The paper presents an analysis of underwater hull condition for the vessel with a composite coating. It is based on a collection of actual data registered in the period of seven years. Significant data have been derived from the analysis, allowing basic set up for theoretical assessment as well as the real justification of extended dry docking period between two consecutive dry dockings of the vessel. Some of the presented facts, related to underwater composite coating, might be used for similar calculations.

The paper describes an evaluation methodology for ship's Planned Maintenance System database based on the application of a newly created questionnaire and the analysis of the evaluation results received by the questionnaire. The evaluation results of several databases and the analysis of evaluation results are also shown in the paper. The main purpose of the paper is to provide a simple and useful tool for the evaluation of all ships' Planned Maintenance System databases, which will enable users to examine the data in the database and discover the areas where the database and maintenance can and must be improved. The expected outcome of the described methodology for the evaluation of ship's Planned Maintenance System database can be described as: - Evaluating ship's Planned Maintenance System database, - Performing ship's Planned Maintenance System database diagnostics to indicate insufficiencies, - Determining the area and mode for ship's Planned Maintenance System database quality improvement and, consequently, overall improvement of the maintenance and reliability of ships' systems, - Setting up a standard for the development and evaluation of computerized database for ship's planned maintenance, - Determining problems which occur during database development and describing complexity of the development process.

This review paper summarizes the legislative framework and the available technologies for ballast water treatment with regard to the approval process and relevant issues. The International Maritime Organization (IMO) sets the limits of organism concentration in ballast water allowed to be discharged into the sea. The 2004 International Convention for the Control and Management of Ships Ballast Water and Sediments is the first international document that introduced obligatory ballast water management and control. Even though ballast water treatment systems are not 100 % effective, they significantly reduce the risk of spreading of invasive species through ballast water exchange. An increased manufacturer interest in the system’s approval or development of new technologies is not expected in future because the procedure is time-consuming and expensive. The final choice of optimal ballast water treatment system depends on the ship owner or operator taking into account the price, type of the ship, whether it is a newbuilding or an existing ship, ballast system capacity and the seas where ships ply as well as harbours at which they call.

As part of the research on high speed radial diesel engines, an analysis had been conducted on the use of the operating systems of the missile boats and comparison of the results with the manufacturer’s recommendations. A graphic model had been set up (block – diagram) on high speed radial ship diesel engine. On the basis of research and empirical data collected on defects which cause the inability to use the engine, the total exploitation reliability of complex technical system and the statistical characteristics of the life of the system had been defined, starting from the assumption that the life of the technical system tested belongs to the Weibull distribution. Research results had been achieved by means of the simulation method (the simulation model) and then were tested with the use of the contemporary computer applications. By defining the levels of operational capability, the levels of reliability had eventually been set up and they need to be ensured through modified maintenance procedures so that the investigated technical system could meet the required criteria. In the research of new samples, the needed intervals of preventive replacement of critical system parts will be determined so that the demanded reliability would be ensured.

Regulations concerning air pollution from merchant shipping are developed at the global level.Because shipping is inherently international, it is vital that shipping is subjected to uniform

Impacts of exhaust gas emissions on the environment and air pollution from ships have received considerable attention in the past few decades. Due to the characteristics of the combustion process, typical for large marine two-stroke low-speed engines, and the use of residual fossil fuels, the world’s fleet emits into the atmosphere significant amount of pollutants such as nitrogen oxides (NOx), carbon monoxide (CO), carbon dioxide (CO2), hydrocarbons (HC), sulphur oxides (SOx) and carbon particles (PM). Impact assessment of the process of their formation, emitted amounts and the influence of emission are important factors for decision making in regulation development and also for engine designers who aim to improve low-speed two-stroke marine engines, for further tightening of regulations regarding limiting emissions. This paper consists of three parts: the first section describes the injection and combustion process in lowspeed two-stroke marine engines, the second part describes the formation of the exhaust as emissions as a product of the combustion process and the third part, in which the known techniques to reduce harmful emissions that are currently used in low-speed two-stroke marine engines are described.

Summary Hydrodynamic and elastohydrodynamic lubrication models were applied to compare the performance of oil lubricated metallic journal bearings with that of sea water lubricated polymer journal bearings in ship propulsion systems. A numerical model based upon the finite difference method and an isoviscous model, together with a computer program with two modules have been used to evaluate the process parameters. The method and model calculations were tested using the data collected from two different types of actual vessels in service. Regarding the stern tube journal bearings, results indicate that the developed software applications attain high approximation accuracy regardless of the relatively simple numerical model.

Current trends in the development of maritime transport and technology in general, and the ship owners' pressures themselves, have forced the producers of large marine two-stroke low-speed diesel engines (by means of the structural modifications) to use low quality fuels oils. These fuels contain substances which under certain conditions can become very corrosive. Today, generally speaking, for the propulsion of merchant ships the use of low speed two-stroke diesel engines in the power range between 5.000 and 80.000 kW, which use very poor quality fuel oil. Combustion of these fuels in the engine cylinders inevitably leads to the formation of electrochemical and dry corrosion, friction and wearing of cylinder elements and exhaust pipes. This paper will analyze the emergence of corrosion and the protection used today against the effects of corrosion in the cylinders of large marine two-stroke low-speed diesel engines.

This paper examines the problem of evaporation of Liquefied Natural Gas (LNG) occurring at different places in the LNG supply chain. Evaporation losses in the LNG supply chain are one of the key factors for LNG safety, technical and economic assessment. LNG is stored and transported in tanks as a cryogenic liquid, i.e. as a liquid at a temperature below its boiling point at near atmospheric pressure. Due to heat entering the cryogenic tank during storage and transportation, a part of the LNG in the tank continuously evaporates creating a gas called Boil-Off Gas (BOG), which changes the quality of LNG over time. The general methods of handling and utilization of the Boil-Off Gas at different points in the LNG supply chain are presented. Attention is given to the issue of LNG energy content transferred during loading and unloading of LNG tankers, as well as to the Boil-Off Gas generated by evaporation of the cargo during maritime transport. The results presented in the paper have been derived from the scientific research project 250 - 2502209 - 2366, "Management of Ship Power Systems under Fault Conditions and Failure" supported by the Ministry of Science, Education and Sports of the Republic of Croatia.

Environmental protection is finally an important issue and, due to previous sea contaminations and for economic reasons, merchant fleets are paying more attention to materials selection and to ship design. Taking into consideration that the propulsion system lubrication, whether oil or water, and the consequent lubricant leakage into sea is a critical problem, the present study examines the practicability and the benefits of implementing water lubricated polymer stern tube bearings instead of conventional white metal bearings lubricated by oil. The investigation method is related to a numerical model and a software application based on finite difference method and isoviscous model. Results, based upon data collected from two different types of actual vessels in service, have shown that power loss in polymer bearings is at least 6 times less than in conventional white metal ones indicating that polymer journal bearings are more energy efficient and environmental friendly.

The selection of the material regarding specific design of the sterntube journal bearings in vessels is critical taking into account the lubrication system, whether oil or water, and the consequent lubricant leakage. To examine the advantages of polymer p

Modern ships are means of transport which, during their entire operational lifespan, need to convey cargo and/or passengers in a safe and reliable way, without jeopardising their safety, and with least possible adverse impacts on the marine environment. The ship’s safety and functionality directly depend on the reliability of her propulsion system, the shafting being the essential unit of the system. The functionality of the ship’s shafting considerably depends on its correct installation. Installation of the ship propulsion shafting is an integral part of the overall positioning (alignment) procedure. Shafting alignment is performed in several stages, starting with the shaft line design, and includes calculating the elastic line and bearing loads, installation of shafting parts onboard ship in compliance with the calculation results, and verifying the alignment results. Procedures are different for ships in service and newly built ships. This paper deals with specific features of the propulsion shafting alignment that is carried out while a ship in service is being converted for a general reason. Unlike a newly built ship, an existing ship imposes additional constraints that should be dealt with in the calculation stage of the process as well as during shafting installation and alignment verification. A calculation approach for ships in service is always different, having specific features from case to case, depending on what is changed and what remains unchanged during the conversion of the ship. The same goes for the implementation and verification of the achieved results. The purpose of this paper is to underline the difference, its contribution being in suggesting the procedure to be followed in case of conversion of an existing vessel.KEY WORDS: ship in service, shafting, alignment, GAP, SAG