Search our collections

SP (sandwich pipes) composed of two steel layers separated by a polypropylene annular can be used for deepwater oil and gas transportation. They combine high structural strength to resist external pressure with thermal insulation to prevent blockage by paraffin and hydrate. In this work experimental tests and numerical models were used to verify the influence of the inter-layer adhesion on the ultimate strength under external pressure and longitudinal bending of a sandwich pipe prototype. The maximum shear stress obtained from sandwich pipe specimens bonded with a specific adhesive indicated the adhesion levels to be adopted in the numerical simulations. Two contact models were used to simulate the bonding and slipping conditions between layers one adopting a friction model and the other including non-linear springs between metal and polymer nodes. The latter is an adapted solution to simulate both tension and shear loads. As expected for a sandwich structure the structural strength is strongly dependent on the interface stickiness. The analysed geometry is able to withstand a water depth up to 3000 m with a bonding strength corresponding to only 10 per cent of the idealised perfect adhesion condition.

VIV (vortex-induced vibration) of spar hulls is one of the key operational issues in high current environments and an important consideration for mooring and riser integrity. Based on extensive analytical laboratory and field studies ExxonMobil has developed a reliable methodology for predicting the VIV of classic spars which has been validated by field measurements. The development of industry's first validated procedure for spar hull VIV is presented. Key factors for reliable prediction of VIV response of classic spar hulls are given along with comparisons of model test results and field measurements. Procedures that enable the first ever evaluation of VIV in the presence of other co-existing sources of excitation such as wave and wind drift are discussed. Looking beyond classic spars the paper highlights extensions appropriate for VIV prediction on newer generation spars.

Air and water drag on sea ice for rough smooth and transitional smooth-to-rough turbulent flow are presented. The results are valid for unstratified planetary boundary layer flow and are based on similarity theory. The geostrophic drag coefficient and the direction of the surface shear stress are presented for steady flow conditions. Water-ice drag results are also presented for tidal (time-dependent) planetary boundary layer flow. In this case the maximum surface shear stress as well as the directions of the surface shear stresses associated with the rotating tidal components are given. For rough turbulent flow the present similarity theory results for air-ice drag as well as steady water-ice drag agree reasonably well with the Davenport (1978) formulas which are obtained as fits to observations in atmospheric boundary layers.

The pile system of the ship berthing structure at Derince Port was damaged by the August 1999 Izmit earthquake. The forces and related displacements by these types of waves and the wave from stream function theory on the piled systems are analysed and compared. In this study by using the observed tsunami wave characteristics in Izmit bay different types of long wave theories are applied to compute the forces and displacements on the damaged pile system at Derince Port. The reasons for the damage of the piled system are discussed by comparing the computed forces and displacements.

Fall-type accidents are the main topic of this paper because this type of accident accounts for 30% of occupational accidents which occur at shipyards. This type of accident happens during walking around ship construction areas. In order to understand the factors which generate a harmful walking mode the relationship between the fluctuation of the motion of the walking body and the walkway environment was investigated and a fluctuation analysis based on a technique belonging to applied chaos theory was conducted. This analytical methodology is proposed for the analysis of the influence of the walkway environment on occupational safety at shipyards.

The rising cost of energy has led to investigations into how electric power generation on board ships can be provided by a simple system burning cheap heavy fuel. This means amongst other things a power supply from heavy fuel generating sets running on unblended bunker fuels . The cost of power generation from bunker fuel auxiliary diesels is discussed and compared with the traditional ship having 2 types of fuel on board i.e. bunker and diesel fuel. Details are given of the design and investment operating and maintenance costs. Fuel treatment common supply systems for main and auxiliary engines and problems of black-out of electric power supply are discussed. Particular attention should be paid by operators to lub oil treatment for auxiliary engines running on bunker fuel. A report is given on the operating experience to date of MaK engines using low-grade fuels.

A numerical method is presented for the analysis of the dynamic responses of large-scale floating structures to random waves. A boundary element method (BEM) is applied to evaluate the fluid motion and finite element method (FEM) to analyse the response of the structure. The BEM and the FEM are combined to solve the wave-structure interaction problem by satisfying the continuity of pressure and displacement on fluid-structure interface. The unknown time-dependent boundary conditions on the free surface and the interface are evaluated by a time-stepping procedure which gives a time domain solution. Comparisons are made with experimental results.

Offshore LQ (living quarters) are typically designated to be or to contain the TR (temporary refuge) including the installation's CCR (central control room) and as such are required to withstand both direct and indirect effects of explosion. LQs are generally located as far as practicable from areas where significant explosion hazards exist. However there is a possibility of LQs being exposed to some residual effects of blast overpressure from an event originating elsewhere on the installation. Guidance on the calculation method used for distribution of external blast overpressure on the LQs is provided. Also given is advice on the application of non-linear finite element analysis methods. However the emphasis is on the aspects of a manual method which can be used with or without the design software.

This publication is intended to provide the shipping community with guidance and information on the loading and discharging of bulk carriers to remain within the limitations as specified by the classification society to reduce the likelihood of over-stressing the ship's structure. The loads that affect the ship's structure are generally discussed with special reference to the derivation of the loading and unloading plans and the requirements for ship/shore communication. A review of the potential problems that could be encountered during cargo operations is presented. Guidance is given on the measures that should be taken to monitor and control cargo and ballasting operations in order to reduce the possibility of over-stressing the ship's structure.

During the research voyage RV 'Akademik Fedorov' (ULA - ice class) to an area of relative inaccessibility strength testing of the bow region of ice belt hull structure was carried out. The method of calculation of ice load is described. This is based on sensors signals which allow the contact load to be determined so that it can be used in designing new vessels for strength analysis of vessels under operation and for developing a requirement for ice belt structures design. The ice load is calculated as an ice pressure distributed in nonlinear symmetrical manner on a rectangular contact zone. The pressure distribution can be described in special case as the uniform distribution hydrodynamic contact ice - hull interaction model or Canadian ice - hull interaction ('Mexican hat'). The results of calculation are used as well as a statistical model to describe the function of ice load parameters from ice condition characteristics.

Numerical simulation of the bi-cone solid-liquid separation hydrocyclones based on Reynolds Stress Model (RSM) is carried out by Computational Fluid Dynamics (CFD) analysis. Re-circulation flow and short-circuit flow phenomena are indicated by simulating results. Also distribution rule of axial velocity radial velocity and tangential velocity of the flow field inside hydrocyclone are obtained. Some of the simulation results are qualitatively in accordance with the Laser Doppler Anemometer (LDA) measuring data. Also the wall erosion problem of the hydrocyclones is studied. The positions of erosion are analyzed and recognized based on Discrete Phase Model (DPM). Erosion of the revised hydrocyclone is obviously improved and the separation efficiency is enhanced by CFD analysis. At the same time characteristic of pressure is analyzed.

Variations in the rate of land reclamation in Japan from 1950-1980 are reported with comment on geotechnical problems encountered: particular attention is paid to the situation in Osaka Bay mid- west Japan where a new offshore airport is planned: location map outline plan generalised profile geological survey data and the occurrence of unconsolidated deposits are considered. Investigations into the mechanism of secondary compression of the marine clays are reported with details of: the drained creep behaviour of normally consolidated clay; the change in state of soil during delayed consolidation; delayed consolidation at on-shore seabed in the recently reclaimed Osaka South Port; and characteristics of the of soils in the area of the proposed airport (including preconsolidation profiles chlorite content and undrained shear strength).

The manufacturing method (seamless UO UOE) has had a considerable influence on the collapse pressure of steel pipes. For UOE-manufactured pipes a significant reduction in collapse strength has been observed compared to unexpanded pipes. A research program has been carried out to investigate the effect of the manufacturing process on the collapse and local buckling behaviour. The results of collapse tests on three 20-inch UOE-manufactured pipes and one seamless pipe are presented. The D/t ratios were 4527 22 and 29. The paper also contains the results of FEA (finite element calculations) carried out to obtain more information on the parameters governing the collapse resistance of UOE-manufactured pipes. The influence of the Bauschinger effect on the collapse resistance was determined. The results of probabilistic calculations with relevant experimental data related to collapse of pipes have been collected in a database and compared with the available design formulae. Design formulations for collapse with appropriate safety factors calibrated against experimental and numerical models using probabilistic methods have been selected for the practical range of design situations.

A methodology for computing the dynamics of interacting risers is presented. During the time simulations riser impacts (if any) are recorded. The relative velocity and angle between the axes of the risers are recorded at each hit so that the actual stress and accumulated fatigue damage may be computed in a post-processing operation. Detailed material properties such as properties of coating the actual composite material properties etc. are used in that process. The methodology is based on a pre-established database of forces acting on the cylinders. At each time step all riser elements are loaded with a combination of in-line and transverse forces depending on local relative distance to the neighbouring riser. This implies that the methodology is based on quasi-static assumptions. The paper presents a validation of the computed force database by comparison with measured results. Examples of results from simulation with top tensioned risers on a TLP are given.

An increasing demand for light and middle distillates such as gasoline or diesel oil has brought about many changes in the refining processes. This in turn has impacted on the quality of marine fuel oils. Screw pumps used in fuel oil conditioning units are presented to illustrate this subject. The main focus is on the mechanical shaft seal. Leakage from this seal is the most frequent failure of such pumps in fuel oil systems. Possible counter measures such as seals with quench to avoid air exposure or double seals such as back-to-back mechanical seals with a supply of pressurised locking oil are presented. However a technical and commercial evaluation of such solutions shows that a complete elimination of the shaft seal is a more reasonable solution. It is shown how the concept of a hermetically sealed pump was realised and successfully implemented.

Hydrocyclone is a kind of multi-phase separator widely used in petrochemical mining and many other industries especially on offshore applications where the space is limited and valuable. The basic separating principle of hydrocyclones and the cyclic experimental research facilities are introduced. The difficulty of separating fine particle is described. Based on a solid-liquid hydrocyclone used for separating fine particles the effect of cyclic flow condition on a hydrocyclone's performance is studied. Effects of cyclic period ratio cyclic flowrate amplitude ratio Reynolds number gas liquid ratio and the cyclical signal type on the hydrocyclone's fine particle separation performance especially on relative overflow purifying rate were studied in detail. The results show that the separation efficiency of the hydrocyclone operated under cyclic flow condition can be higher than that in steady condition when the cyclic period ratio is about 0.68 and the cyclic flowrate amplitude ratio is about 2 percent. Rectangular wave seems to be the best cyclic signal for enhancing the hydrocyclone's separation efficiency. The cyclical change of flowrate leads to the increasing of hydrocyclone's energy consumption to some extent while the increasing amount is very less which is no more than 3 percent in general.

With development occurring in increasingly challenging environmental conditions the potential benefits of riser monitoring for completion-workover operations with open sea completion risers are becoming more apparent. This is particularly the case when monitoring is combined with an on-board numerical riser model that can provide real-time operational guidance to rig personnel. The use of a RMS (riser management system) with these capabilities presents opportunities for significant cost savings from a maximised operational window and enhanced safety and riser integrity. An RMS is described that has been supplied for a completion-workover riser application in the Barents Sea. The key features of the RMS are described with particular emphasis on the procedure used to determine the riser response from a limited number of riser strain measurements using the FE numerical model of the riser. Experience with deployment of the system and its use in practice is described and some of the key benefits are highlighted.

Minimising the response levels for the top and bottom riser angles during drilling is crucial for a successful operation and also for maintaining riser integrity in a long-term sense. One way of achieving reduction of these angles is by moving the surface floater to a given position. If mooring lines are applied re-positioning of the vessel is a rather slow and laborious process. If a DP (dynamic positioning) system is applied the attractive option arises to implement riser response criteria directly within the control loop. At present no fully automated system has been implemented on an offshore drilling unit. The relationship between surface floater motion and angle responses is first considered. The possibility of reducing the maximum angular response levels by dynamic positioning of the floater is then investigated. Application of structural reliability methods in relation to on-line dynamic control of the floater position is considered. A number of observations are concluded. The procedures also have further relevance for other control problems (formulations) where the underlying load and response processes develop slowly and where the dynamic components are of significance.

The effects of percentage EGR (exhaust gas recirculation) and operating parameters on NOx emission concentration are investigated for marine diesel engines. Work regarding NOX emissions reduction methods is reviewed in brief. IMO permissible levels for diesel engines as a function of speed are presented. A computer program is developed and used to investigate the effect of EGR on NOX emissions using LNG (liquid and gaseous) fuel as well. A test rig is erected to verify the results from the computer program. An empirical formula is derived to predict the percentage variation in NOX with the variation in percentage of EGR. A comparison between the theoretical results and the experimental results using liquid fuel showed good agreement. It is concluded that EGR is a useful method for reducing NOx from diesel engines at a reasonable cost. Additional work is identified for further study.

The nutritional requirements of marine finfish larvae have received considerable attention and studies have show that DHA (docosahexaenoic acid) affects the growth and survival of marine finfish larvae. We investigated the effects of different rotifer diets containing variable amounts of DHA on the growth and survival of larval Atlantic cod (Gadus morhua L.) Four different commercial rotifer enrichment formulations were used. The results showed a positive effect of rotifer DHA proportions on growth and survival of cod larvae and demonstrated that Atlantic cod larvae require a high ration of dietary DHA to EPA.