Problem of Boil - off in LNG Supply Chain Dobrota, Đorđe; Lalić, Branko; Komar, Ivan
Transactions on Maritime Science,
10/2013, Volume:
2, Issue:
2
Journal Article, Paper
Open access
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 scientifi 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.
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
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 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.
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.
Današnji trend u razvoju pomorstva i tehnologije općenito, a samim time i pritisci brodara, nagnali su proizvođače velikih brodskih dvotaktnih sporohodnih dizelskih motora da konstrukcijskim ...modifikacijama omoguće uporabu goriva sve lošije kvalitete. Takva goriva sadržavaju tvari koje u određenim uvjetima mogu postati vrlo korozivne. Danas se, generalno gledajući, za pogon trgovačkih brodova koristi sporohodnim dvotaktnim dizelskim motorima u rasponu snaga od 5,000 do 80,000 kW i to na goriva vrlo loše kvalitete. Izgaranje takvih goriva u cilindrima motora neminovno uzrokuje stvaranje elektrokemijske i kemijske korozije, te trenje i trošenje elemenata cilindara i ispušnih vodova. U ovom će se radu analizirati problem nastanka korozije i zaštita kojom se danas služi poradi sprečavanja korozijskog djelovanja u cilindrima velikih brodskih dvotaktnih sporohodnih dizelskih motora.
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.
A diesel propulsion plant for large ships is a very complex and high risk system with strong demands for its reliability. Strict requirements are to be imposed on the marine diesel engine speed ...control in all working conditions. This paper deals with the problem of tuning the engine speed controller parameters. A very effective and practical experimental tuning method, based on the experience of engine experts, has been proposed and tested during the final testing of a large marine 2-stroke slow speed diesel engine on a test bed. The digital engine speed controller with an electrical synchronous servo motor has been used as the fuel actuator. Several scenarios of the engine speed controller tuning and testing with the fuel actuator and the engine speed response are given in the paper for illustration purpose. The experimental tuning time of optimal controller parameter values was short, and the final engine tests on the test bed showed very good results for the whole engine working regime. The experimental engine controller tuning method based on expert experience and heuristic knowledge could be very useful during the long-term operation of the engine.
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