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Estimation method for arrival directions of radio waves to measure the surface current of sea using VHF radar on vessel
AuthorsRei Arai ; Naoki Nakatani ; Kentaro Sachi et al.
Date published2009
AbstractRecently VHF (Very High Frequency) radars have frequently been used for measuring the flow velocity field on the coast as they enable the velocity distribution for exceedingly wide regions to be obtained simultaneously. This paper describes the results of an examination of the inference of a radar installed on board a steel vessel where a VLCC (Very Large Crude-oil Carrier) was used for the experiments. Even if the characteristics of the received waves called antenna pattern here is deformed it is possible to estimate the arrival direction of the radio waves in specific regions. The results imply the possibility of measuring the flow velocity distribution by means of VHF radars on board vessels.
AuthorsRei Arai ; Naoki Nakatani ; Kentaro Sachi et al.
Date published2009
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Estimation of wind at sea with land-sea coefficient (roughness topography and contraction) from wind observed on land
AuthorsRyuji Koh
Date published2002
AbstractWhen predicting waves wind at sea is estimated with synoptic maps or by observing wind on land. For inland sea with a short fetch wind observed on land seems to be more precise than the wind estimated with large-scale synoptic maps. However observed wind is always affected by surrounding topography and buildings. Wind observed on land is converted into wind at sea with a presumed multiplier. Here theoretical 'quantifying' estimation is proposed to replace 'presumed' multiplier with land-sea coefficient as a product of roughness coefficient topographical coefficient and contraction coefficient.
AuthorsRyuji Koh
Date published2002
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Experience from operation inspection and condition monitoring of offshore pipeline systems on the Norwegian continental shelf
AuthorsA K Thomsen ; R L Leonhardsen
PublisherInternational Society of Offshore and Polar Engineers
AbstractThe Norwegian Petroleum Directorate (NPD) has a computerised database called CODAM (COrrosion and DAMage database) in which incidents and damages on structures risers and pipelines are recorded. An overview of different incidents and occurrences related to the offshore pipeline system on the Norwegian continental shelf which occurred between 1975 and 1996 based on information in CODAM is presented. Types of incident include causes of loss of containment corrosion attacks free spans exceeding the design criteria upheaval buckling scratchmarks dents cracks and horizontal deflections.
AuthorsDate publishedA K Thomsen ; R L Leonhardsen
1998
PublisherInternational Society of Offshore and Polar Engineers
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Experimental and numerical study of heave-induced lateral motion (HILM)
AuthorsC Le Cunff ; F Biolley ; G Damy
Date published2005
AbstractExperiments were carried out at IFREMER Brest to obtain data on the displacement of Steel Catenary Risers (SCR) in the Touch-Down Zone (TDZ) induced by top motion. Measurements were conducted both in the section on the ground (2D motion) and in the section above the touch-down point (3D motion) with an optical tracking system. In the model test the bottom 1/10 of the riser was represented at a scale of about 1/10. The present paper is focusing on Heave-Induced Lateral Motion (HILM) in the bottom part of the riser. The model riser is based on a full scale case which is first described. Based on Froude's similitude the geometrical characteristics of the model are derived. The tracking system and the various instrumentation are then detailed. In the last section experimental results on one specific case are presented. Numerical calculations with a coupled fluid/structure solver are performed. A comparison for the amplitude and frequencies of HILM is presented.
AuthorsC Le Cunff ; F Biolley ; G Damy
Date published2005
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Experimental trials on a spark ignition engine fuelled by producer gas from charcoal to provide up to 4kW shaft power
AuthorsG R Breag ; A P Harker ; A C Hollingdale ; D Pearce
Shelf Location230b
AbstractThis report outlines the development work carried out on a motive power system capable of developing up to 4 kW shaft output using producer gas manufactured from charcoal. Details of the systems used, fuel consumption efficiencies, gas quality, engine performance data and wear of the engine are presented. The gasifier/engine unit would be of particular relevance as a power supply source operating on charcoal fines from an on-going charcoal industry.
AuthorsPublisherG R Breag ; A P Harker ; A C Hollingdale ; D Pearce
Tropical Products Institute
Shelf LocationDate published230b
1982
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Fatigue life evaluation of inner-surface flaw in welded tubular joint of offshore platform
AuthorsI Soya ; J Kobayashi ; R Kohno et al.
PublisherAmerican Society of Mechanical Engineers - ASME
AbstractThe weld toe on the outer surface of a tubular joint which is called the hot spot is a critical point for fatigue failure. However the failure seldom occurs from the weld toe of the weld root on the inner position of the joint. It is not clear whether the inner surface of joint becomes critical when a crack-like flaw exists on the inner surface. Some numerical cases were carried out on a jacket-type platform. Three-dimensional finite element analyses were conducted on several types of tubular joints to obtain stress distributions through wall thickness and hot spot stresses on the surface. The fatigue life for the inner surface flaw was found to be longer than that for the hot spot.
AuthorsDate publishedI Soya ; J Kobayashi ; R Kohno et al.
1997
PublisherAmerican Society of Mechanical Engineers - ASME
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Float-off operation of a land-built COT on dual transportation barges: time-vs. frequency-domain analysis
AuthorsChan K Yang ; D H Lee ; M H Kim et al.
Date published2005
AbstractIn this paper the float-off operation of a land-built crude oil tank (COT) loaded out and towed on launching dual-submersible barges is numerically simulated by a time-domain vessel-mooring-riser coupled dynamic analysis program with multiple floating bodies. The study is particularly focused on the maximum load prediction on connectors and the minimum gap prediction between barges and the COT. In case of simpler modeling the time-domain simulation results are compared with frequency-domain results. Then the time-domain model is run for more realistic situation with hawsers and mooring line. In hydrodynamic analysis the interactions among the 3 floating bodies are fully taken into consideration. In the frequency-domain analysis the connectors between barges are modeled by equivalent translational and rotational springs the stiffness of which is estimated using Euler's beam theory. In order to assess the possible occurrence of contact between COT and barges the relative motions between barges and the COT at several points of interest were investigated.
AuthorsChan K Yang ; D H Lee ; M H Kim et al.
Date published2005
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Fracture toughness requirement for fracture performance evaluation of welded joints based on the local approach
AuthorsF Minami ; M Ohata ; M Toyada et al.
PublisherThe American Society of Mechanical Engineers - ASME
AbstractA new procedure for fracture toughness requirement to meet the design solution of structural components is based on the local approach with Weibull stress used as a fracture driving force of notched materials and 3-point bend specimens and the proposal of an equivalent CTOD (crack tip opening displacement) concept. Theoretical principles with supporting experimental evidence are discussed for: the equivalent CTOD concept based on the local approach; the transfer of 3-point bend results to fracture performance evaluation of a wide plate; and the fracture toughness requirement based on the equivalent CTOD concept.
AuthorsDate publishedF Minami ; M Ohata ; M Toyada et al.
1996
PublisherThe American Society of Mechanical Engineers - ASME
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GloBallast Monograph Series No. 9 - 1st International Workshop on Guidelines and Standards for Ballast Water Sampling
AuthorsSteve Raaymakers
Shelf Location226b
AbstractThe objectives 1st International Workshop on Guidelines and Standards for Ballast Water Sampling were: to review ballast water sampling activities undertaken by various entities around the world to date, and to allow discussion and debate comparing methods and results; to initiate greater global coordination and cooperation on this issue, including sharing expertise, experiences and data; to review the various ballast water sampling guidelines and standards that are currently available and adapt them into draft international guidelines, for use by the GloBallast Pilot Countries and consideration by IMO’s Marine Environment Protection Committee (MEPC) in the context of the new Convention; to provide practical training to the delegates from the GloBallast Pilot Countries in standardised ballast water sampling methods, to allow them to purchase the necessary equipment and develop and implement ballast water sampling programmes on return to their home countries.
AuthorsPublisherSteve Raaymakers
International Maritime Organization IMO
Shelf LocationDate published226b
2003
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Guidelines on the use of high-modulus synthetic fibre ropes as mooring lines on large tankers
AuthorsOil Companies International Marine Forum (OCIMF)
Shelf Location236c
AbstractRope manufacturers have introduced a new generation of synthetic fibre ropes claiming they are equivalent or superior to traditional steel wire mooring ropes. A number of tanker operators have adopted them. The publication of these guidelines was deemed necessary by the members of the OCIMF to address what is seen as a gap in recognised industry guidance. They give an overview of high-modulus synthetic fibres, the advantages and disadvantages of high-modulus synthetic fibre ropes compared with steel wire mooring ropes, selection of high-modulus synthetic fibre mooring ropes, installing high-modulus synthetic fibre mooring ropes, inspection, service life and splicing, quality assurance and recommendations.
AuthorsPublisherOil Companies International Marine Forum (OCIMF)
Witherby & Co.
ISBN number1856092305
Shelf LocationDate published236c
2002
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Influence of oxygen on electrode consumption and penetration in GTA welding
AuthorsYoji Ogawa ; Takao Morita
Date published2004
AbstractDynamic behaviour of arc-cathode and arc-anode reactions was observed by ultra-high speed video system in a chamber from vacuum to high pressure where contents of gas are controlled. Effects of oxygen and minor elements on anode and cathode reactions were considered. Influence of oxygen addition on electrode consumption and penetration in GTA Welding was discussed. Oxidation reactions and their produced oxides play an important role on cathode erosion. Oxidation accelerates erosion of tungsten electrode apart from cathode spot region. Plasma arc pattern is slightly changed by addition of oxygen and active flux. The behaviour is almost the same. Addition of oxygen into the shielding gas deepened the penetration. The effect is also the same as active flux coating
AuthorsYoji Ogawa ; Takao Morita
Date published2004
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Landing on the roof: CVN noise
AuthorsKurt D Yankaskas ; Michael F Shaw
Date published2006
AbstractAircraft flight operations noise has received considerable attention in the civilian and commercial worlds. There has been renewed interest in the human effects of excessive intermittent airborne noise occurring on the 03 Level (Gallery Deck) and on the Flight Deck during aircraft launch and recovery operations ('Flight Ops.') aboard US Navy aircraft carriers. High noise levels cause crew fatigue lost work hours high crew turnover safety problems and worst case hearing damage or loss of life. The cost of this problems can be quantified as part of the Total Ownership Cost of the ship by taking into account such factors as the cost of veterans' hearing compensation crew retention bonuses and crew turnover. This interest has lead to at-sea measurements of intermittent noise levels during flight operations on two operational aircraft carriers. This data provides the first detailed systematic quantification of sound pressure levels noise frequency content noise time duration and frequency of events.
AuthorsKurt D Yankaskas ; Michael F Shaw
Date published2006
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MAIB Report of the Chief Inspector of Marine Accidents into the Failure of the Lifeboat Launching Equipment on mv Norsea on 5 February 1992 with the Loss of 2 Lives
AuthorsMarine Accident Investigation Branch (MAIB)
Shelf Location15d
AbstractContents include: Particulars of ship and crew and narrative of the events; Consideration of possible factors including decision to use the band bowsing system, sequence of failure and possible reasons for structural collapse of the lifeboat davits; Further comment and discussion including operation of the band bowsing system brake, approval of lifeboat launching system, search and rescue, management of the project, decisions made by Schat-Davit following the accident; and Conclusions - both findings and recommendations.
AuthorsPublisherMarine Accident Investigation Branch (MAIB)
Department of Transport (DOT)
Shelf LocationDate published15d
1993
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Modular approach to ships and ports security based on quantifiable relative risk index (RRI)
AuthorsBhatia
PublisherIMarEST
AbstractThe Internaional Ships and Ports Security (ISPS) Code comes into effect on 1 July 2004. Acordingly all passenger ships cargo ships over 500gt on international voyages including high speed crafts will have to carry onboard approved Ship Security Plan (SSP) and Ship Security Certificate (SSC). In essence the underlying purpose of the Code is to make ships and ports more secure and resilient to many growing threats from terrorism to theft and pilferage. However from the author's point of view it does little more than raise awareness of these threats. In this paper some of the inherent weaknesses in the present approach are highlighted and a new modular approach to ship and port security based on a quantifiable relative risk index (RRI) developed by the author is introduced.
AuthorsDate publishedBhatia
2004
PublisherIMarEST
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Numerical simulation of broken ice cover forces on structures: a parametric study
AuthorsM Sayed ; R Frederking ; A Barker
Date published2000
AbstractIce forces on structures in drifting broken ice are a concern for offshore petroleum production operations off the East Coast of Canada. Methods for estimating these forces remain uncertain. The complexity of ice-structure interaction also poses several difficulties to numerical modelling. This study deals with a class of problems where the behaviour of the ice cover can be modelled using a continuum cohesionless Mohr-Coulomb criterion. A numerical model of broken ice cover interaction with offshore structures is presented. The model is based on a PIC (particle-in-cell) approach combined with a viscous plastic ice rheology (Mohr-Coulomb plastic yield criterion) to describe ice properties. The Zhang-Hibler(1997) numerical scheme is used to solve the momentum equations. A parametric study is conducted in order to determine the influence of shape of the structure ice thickness ice properties and velocity on the resulting ice forces.
AuthorsM Sayed ; R Frederking ; A Barker
Date published2000
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On the Availability of Subsea Blow-Out Preventers
AuthorsN de Moura-Jorge ; J Wolfram ; P Clark
Date published1998
AbstractThis paper describes some analyses that have been undertaken on two samples of field data on submarine BOP failures. One of these databases has been compiled from PETROBRAS Drilling Reports and the other obtained from the SINTEF BOP Database. The usual textbook approaches have been found to be inadequate for the analysis of this data and new methods have been developed and are described. In the past the failure rates for BOP systems have been assumed to be constant however the analysis presented here provides strong evidence that they are not; and that failure rate of the BOP systems varies during the period of deployment on the wellhead. The implications of this and the variation in risk during the various phases of well development upon appropriate target levels of availability and the inspection intervals required to achieve these are discussed.
AuthorsN de Moura-Jorge ; J Wolfram ; P Clark
Date published1998
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On the splitting of main currents in the Indonesian Seas
AuthorsW H Burnett ; V M Kamenkovich
Date published2002
AbstractA regional baroclinic model of the Indonesian Seas circulation is presented. This is based on the Princeton Ocean Model. Fifteen levels in the vertical are chosen to resolve the vertical structure of the circulation. The horizontal resolution of about 10 km provides a sufficiently accurate description of the bottom topography in the area. Three open boundary ports are introduced to simulate the Mindanao Current inflow into the region; the North Equatorial Counter Current outflow to the Pacific; and the resultant outflow to the Indian Ocean. The results of barotropic experiments show that the splitting of simulated currents between the Lombok Strait and the Flores Sea and between the Makassar Strait and the Malucca Sea differ substantially from the splitting schematics based on observations. The analysis of baroclinic experiments is presented to reveal the influence of baroclinicity on the structure of splitting patterns.
AuthorsW H Burnett ; V M Kamenkovich
Date published2002
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Optimized damping to reduce noise on high speed-lightweight craft
AuthorsRaymond Fischer ; Leo Boroditsky ; Ronald Dempsey et al.
Date published2009
AbstractNoise levels are generally higher on high speed-lightweight craft than other craft due to their construction and high power-to-weight ratio. One effective method to reduce noise is the application of damping materials particularly on aluminum vessels. These damping materials both tile and spray-on can reduce both structureborne and airborne transmitted noise. Noise can be effectively controlled for minimal weight increase when the treatment thickness and coverage area are carefully optimized. This paper presents case histories of damping treatments applied to SEAFIGHTER (X-Craft) and a high-speed ferry patrol boat and crew boat. The techniques used to evaluate the damping material itself and incorporate the material's performance into a predictive tool are discussed. Damping to reduce noise induced by machinery and high-speed flow impact are also discussed.
AuthorsRaymond Fischer ; Leo Boroditsky ; Ronald Dempsey et al.
Date published2009
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Ormen Lange sub-sea condition and leakage monitoring
AuthorsJens Abrahamsen ; Svein Haugen ; Trond Benny Bertmand et al.
Date published2007
AbstractWith the Ormen Lange development Norsk Hydros sub-sea solutions are taking technological developments on the Norwegian continental shelf a significant step ahead. Nothing will be visible on the surface when the enormous gas field comes onstream in 2007. High pressure large water depth and distant location called for a new way of thinking in many ways. The leakage and CMS (condition monitoring system) developed to ensure safe and pollution free operation of the two templates at 850 meters water depth are presented. Back in 2000 Hydro and Naxys Naval Technology started the development of a new type of sub-sea monitoring system based on technology originally developed for naval warefare and surveillance. After successful testing on the sub-sea processing plant Troll Pilot in 2001 the system was further developed and qualified. On the Ormen Lange Templates one centrally positioned module containing an array of acoustic sensors monitors the complete 44 x 33-m template. The system provides location and magnitude of any leak structural vibration or valve malfunction on the template.
AuthorsJens Abrahamsen ; Svein Haugen ; Trond Benny Bertmand et al.
Date published2007
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Papers Presented at the Second International Symposium on Wave and tidal energy September 1981
AuthorsBHRA Fluid Enging
Shelf Location213d
AbstractSecond Int Symp held in Cambridge 23 - 25 Sept 1981 Papers are Environmental implications of wave power proposals for the Outer Hebrides and Moray Firth The spatial distribution of wave power on the western UK coast One dimensional modelling of tidal power schemes Mathematical modelling of tidal power in the Bristol Channel Surges in tidal power basins - can they increase power output Dynamic models of tidal estuaries A fluid transmission system for wave energy converters Wave energy - the influence of maintenance repair requirements Moorings for wave energy devices The influence of Severn tidal power schemes on sediment transport processes Environmental implications of tidal power proposlas with particular reference to the Severn Estuary Power generation from tidal flows for navigation buoys A hydrodynamical model of the Lancaster flexible bag wave energy device Extreme wave forces on submerged cylinders Turbine caissons for the Severn Barrage
AuthorsPublisherBHRA Fluid Enging
BHRA
Shelf LocationDate published213d
1981