bluuebunny/crossref_metadata_2025_split huggingface dataset:
Model Testing of OTEC Plant Platform and Cold Water
Authors: Barr Roderick A. , Sheldon Lewis R. 
Published: October 2008

INTRODUCTION
In 1975 the Department of Energy (then ERDA) initiated a significant effort to develop ocean thermal energy conversion (OTEC) as a commercial energy source. Significant technical effort has since been devoted to investigation and solution of technical problems associated with OTEC. Certain areas, such as heat transfer, biofouling of heat exchangers and structural loading of the cold water pipe (CWP), have emerged as key OTEC technical problem areas.
The design of OTEC plant CWPs which can operate without failure for 30 to 40 years is a difficult problem, particularly when the severe environmental conditions which can occur at most proposed OTEC sites (Puerto Rico, the U.S. Gulf of Mexico, Hawaii, etc.) are considered. Over the past four years a number of analytical methods have been developed for analyzing CWP dynamic and static loads. These methods have been used as a primary basis for most of the CWP designs and studies carried out to date. The more widely used methods are based on different methods of approach and assumptions, and hence are of different potential accuracy for different CWP designs.
It is essential that analytical methods be carefully validated if they are to be used with confidence to design CWP's. Scale model test data provide the best basis for validation, and validation efforts to date have relied primarily on data from laboratory and at-sea model tests. This paper discusses model testing of OTEC plant platform/CWP configurations in waves, with emphasis on simularity or scaling requirements and two sets of laboratory tests carried out at HYDRONAUTICS Incorporated. The use of the test data for validation is also considered.

SCALING REQUIREMENTS FOR OTEC MODELS
Three types of scaling are applicable to seakeeping or other model tests of OTEC plant platforms and CWP's. These are: dynamic scaling; hydrodynamic scaling, particularly of the CWP; and structural or elastic scaling of the CWP. The first two types are considered in most ocean engineering testing, while the latter type is typically not considered. This section considers scaling or similarity cosiderations for OTEC models with emphasis on CWP elastic or hydroe1astic scaling. A more detailed discussion of scaling is given by Barr and Johnsonl

DYNAMIC SCALING
For any test in ocean waves, which is the environment of greatest interest for OTEC plants, it is essential to observe Froude scaling, in which the Froude number, F, is identical in model and prototype:
(available in full paper)
where V is a characteristics velocity, l is a character istic length and g is gravitation acceleration. This scaling makes acceleration invariant between model and prototype and requires that
(Available in full paper)
where the subscripts m and p denote model and proto type, respectively, and ? is the linear scale ratio of prototype to model size. An important implication of Equation [l] is that:
(Available in full paper)
Advanced Use Of The Radiopositioning System Pulse/8 In The North Sea
Authors: Fritzner Hans E. 
Published: October 2008

ABSTRACT
One of the most commonly used radiopositioning systems in the North Sea, Pulse/B is discussed. The background is the recording and processing of a large volume of data from both survey vessels and anchored, semisubmersible drilling rigs in the Norwegian Sector 58°-62°N. Methods in order to improve the accuracy are presented. This include the Pulse/8 system both in hyperbolic and circular mode as well as utilization of the differential technique. Processing of data such as filtering and computations of three-way fixes and fixed errors is also discussed. For the hyperbolic mode, the results show that filtering and the use of three-way fixes will improve the repeatability well below the claimed 50 meters within most of the actual area, 25-30 meters can normally be found. When thorough establishment of the fixed errors is carried out for a location, the absolute accuracy will be of nearly the same order as the repeatability. More advanced use of the system wil improve the accuracy further, in certain areas possibly even below 20-25 meters. Finally, the circular mode of the Pulse/B system has been found to be, an attractive system in new areas with limited activity.

INTRODUCTION
During the last years, one of the most commonly used radio positioning systems in the North Sea offshore activities has been Pulse/B. This 100 kHz, pulsed and Loran C-like radio positioning system has six transmitting stations located as shown on Fig. 1, and operated by a joint venture between Decca Survey Ltd. and A/S Kongsberg Vapenfabrikk (from now on to be called the "Contractor".) As shown, a repeatability of less than 50 meters is claimed within most of the North Sea.
In this Paper, some methods with the intention of improving the accuracy are discussed. The background for this discussion is the recording and processing of a large volume of Pulse/8 data from both survey vessels and anchored, semisubmersible drilling rigs in the Norwegian Sector 58°-62°N.
The methods include the system applied both in hyperbolic and circular mode as well as utilization of the differential technique. Various methods of data processing are also discussed such as filtering (smoothing) and computations of three-way fixes and fixed errors.
Most of the data presented have been recorded on board anchored rigs. Under normal weather conditions, the movements of the rigs can be regarded as negligible. Therefore, the readings can be treated as recorded under stationary conditions.
In this Paper, the emphasis is laid upon the experiences from Pulse/8 data projects. Therefore, descriptions of the system and navigational and statistical theory are limited to a minimum.

THE OPERATION OF THE SYSTEM
On each of the six transmission stations, free-running, high stability cesium oscillators are giving the time reference for the pulses.
A Guide To Flare System Design, With Particular Reference To Offshore Platforms
Authors: McMurray Robert , Oswald Brian J. , Witheridge Rodney E. 
Published: October 2008

ABSTRACT
If an offshore flare system is designed without being integrated from the start with that of the overall platform, the resulting system will be less effective than need be in terms of safety, cost, energy efficiency and operability.
This paper presents a guide to the most important, factors to be considered in designing offshore flare systems, including safety, process requirements and pollution, noise and radiation from flares. The methods used to calculate flare radiation are reviewed critically. Case studies are cited to illustrate the cost and material benefits which can be achieved if the flare system is considered from the outset as an integral part of the production process equipment.

INTRODUCTION
In land based oil fields flaring has not been an important part of the process since the flare could, until recently, be sited well away from the plant and its environmental impact minimised. Engineers were often tempted to write the words ‘To the Flare’ on an arrow pointing off the edge of a process flow sheet and then forget them. Quite often this represented the bulk of the initial design information for the flare system and the detailed design was not considered until near the end of the project. The flare system then had to meet the diverse and often conflicting requirements of a multiplicity of gas sources, making design optimisation difficult if not impossible.
For offshore fields, particularly in deep water locations, the flare is an important part of the process because economics often prohibit locating it sufficiently far away to have no impact on the platform.
It thus needs to be considered in detail at the initial design stage since to some extent the flare system can have a significant influence on the process design and oil production rate. Early consideration makes available a greater number of options and leads to the most efficient and cost effective system.
A previous paperl described how the development of new high technology flares has made on-platform flaring viable, and by eliminating the need for a separate flare platform has resulted in enormous cost savings for deep water locations such as the North Sea. The flare is much closer to the operator and previously used design calculation methods involving many implicit assumptions are no longer satisfactory. Under-design will lead to potentially unsafe operation whereas over-design carries enormous cost penalties. This paper presents a guide to the most important factors in designing offshore flare systems and looks critically into one of the most important aspects - accurate prediction of flare radiation. Case studies are presented which highlight the fact that offshore flare design is not a simple matter and that fairly detailed analysis is required to produce the most economic system.
Buchan Development Project - Conversion Of A Drilling Rig Into Afloating Production Platform
Authors: Logan Barrie L. , Rothwell Eric G. 
Published: October 2008

ABSTRACT
This paper describes the conversion of a Pentagone drilling rig into a floating production facility as part of the development of the Buchan Field, North Sea. It examines the key areas of work involved, the problems encountered and solutions reached in order to provide facilities for a peak production rate of 72,000 BPSD of stabilised crude meeting all current UK statutory requirements.

INTRODUCTION
The Buchan Field is located in the UK sector of the North Sea approximately 160 km E.N.E. of Aberdeen with a water depth over the field between 112m to 118m. The field development is based on subsea completions tied into a subsea manifold, connected in turn by a flexible riser to a floating production platform. 9il export is by tanker from a single point mooring buoy.
The rig selected for conversion was Pentagone 83 ?Drillmaster? built in France in 1973. The technical reasons for the selection of a Pentagone included the advantages of its stability, its load carrying capacity and apparent spaciousness.
This marginal field with a relatively short field life, called for minimum time and capital investment. These concepts and the need to meet all statutory regulations were the guiding factors at all stages of the project.

REMOVAL OF REDUNDANT EQUIPMENT
The philosophy adopted for the removal of existing redundant equipment and materials provided essential space and weight reduction. As the production platform was not required to have drilling or well workover facilities, the strip out naturally centred on existing drilling equipment.
The dry mud bulk silos situated to the rear of the derrick were cut and removed in sections giving a reasonably clear area at top, intermediate and lower decks for additional accommodation.
The cement pump was left for well-kill duty. The mud pumps and associated equipment located on the forward lower deck were taken out through intermediate and top deck cut-outs. Together with the dismantling of five of the seven mud tanks and removal of top deck drill pipe racks this provided space at all three levels forward of the derrick for process and utility equipment.
The principle of the new layout therefore was for non-hazardous and quiet accommodation areas to be placed to the rear of the derrick and process and utility equipment to be placed forward of the derrick.
In conjunction with the key items listed above, a multitude of minor systems and equipment were removed or replaced for various reasons as detailed in later sections. The approximate total permanent weight removed from the existing drilling rig was 1,400 tonnes.

PROCESS AND UTILITIES

(a) General
The basic process requirement for Buchan platform was for a simple effective system to separate the oil feedstock from the wells into the component crude oil, gas and water phases. Facilities are designed to produce a peak of 72,000 BPSD of stabilised crude from a feed crude of 33 - 36° API and a G.O.R. of 308 scf/bbl.
Development And Application Of A High Speed Automatic Field Welding Method For Pipeline
Authors: Takeshi Yasuhira , Sakurai Hideo , Bada Toyoaki , Nogami Mitsuo 
Published: October 2008

Abstract
A automatic field welding method of high speed and good reliability was developed with one-side downhill gas metal arc welding (GMAW) method. The results are followings:Diagrams for selection of the appropriate welding conditions in which high efficiency without any defects can be gained in narrow groove welding.A novel groove shape was developed for preventing deposition of copper onto the root bead when the bead was welded from outer side with copper backing from inside.The effect of new-type groove was confirmed by means of a direct observation of root bead with a special device from the reverse side.The new-type groove makes an appropriate welding condition range enlarge and quality and efficiency increases. Copper does not deposit onto root bead even at an experimental welding speed of 210 cm/min.

Introduction
Pipeline installation requires the use of a welding method presenting high pipe-laying efficiency and therefore high welding speed. Also, petroleum and natural gas pipelines require high-quality welds. The present report describes the development of a computer-controlled automatic one-side downhill welding method using high-current-density GMAW with regard to the girth welding of pipe.
In this method, the groove root is made tight and non-gapped, and welding is performed in the narrow gap with little deposit metal, in order to shorten the pipe alignment and welding time. An appropriate procedure for this method was established by developing the downhill welding which uses copper backing on the pipe inside and small diameter solid wire on the pipe outside.

Experimental Procedure
The welding test was conducted by tack-welding the end of a steel pipe ring (5), for which the prescribed pipe and bevel preparation had been made in advance, to an end face of a fixed steel pipe (2)on a stationary frame (1), fitting another steel pipe ring to the other end face of the pipe in the same way, aligning the grooves of the rings, expanding the pipe by internal clamp (4) and performing downhill. GMAW of the pipe by welding machine (3) as shown in Fig. 1. The internal clamp was provided with a backing copper ring fixed into its clamp shoe for alignment so that backing was effected simultaneously with clamping. Chemical elements and mechanical properties of the tested wire were as shown in Table 1. Wire diameters of 0.9 mm and 1.2 mm were studied, and wire 0.9 mm in diameter was decided to be used in the testing because of its less amount of sputtering and greater stability of arc. For the shielding gas, both CO2 and Ar were used. The test results revealed that the narrow-gap one-side downhill welding of pipe performed at high speed by GMAW method involved the problems shown in Table 2.

Basic Shape of Groove
Groove shape largely influences the pipe alignment operation and the selection of appropriate welding conditions. To shorten the aligning time, the groove should preferably be non-gapped, in addition to having root face.
The Development And Proposed Use Of A Wave Force Measurement System
Authors: Mann David P. , Andrews Arthur P. 
Published: October 2008

Abstract
A transducer has been designed to measure the forces, primarily due to waves, experienced by structure!;&gt; at sea. It is designed to be fitted to structures already at sea and does not require mechanical modifications to the structures.
This paper briefly describes the development work leading to the trials at sea of a small scale prototype then discusses the problems that are anticipated for the use of this transducer on larger, full-scale, structures and indicates possible solutions to these problems.

1.Introduction
The National Maritime Institute (NMI), a united Kingdom Government (UKG) research establishment of the Department of Industry, provides a service of measurements at sea. In 1975 a range of research programmes were sponsored by the Ship and Marine Technology Requirements Board (SMTRB) of the UKG to investigate and prOVide basic data about forces exPerienced bytypical structures at sea such as oil rigs due to their inter-reaction with the'natural environment. As part of this research NMI were given charge of the section involving the measurement of forces and environmental conditions experienced by a specially constructed research structure,. intermediate in size between laboratory scale models and full size. This structure located just off the south coast of the UK is referred to as the christchurch Bay Tower (CBT),(Fig. 1). It is 27.8 metres tall and stands in 8.4 metres of water. 128 channels of measurement and environmental data are monitored on a regular basis. [1].
During the initial investigative work for this structure it became readily apparent that forcemeasurement on structures at sea commonly relies on the use of strain gauge devices, normally installed during structure manufacture. Although not proposed for use on the CBT, a requirement was seen for a simpler system of wave force measurement that could be easily attached to existing structures already at sea. As a result of this a technique was proposed whereby pressure changes caused by wave forces rather than by sea surface elevation changes, could be measured. The system that was proposed, shown schematically in Fig. 2, is that a number of flexible, fluid-filled cells, enclosed in a rigid outer casing, are equi-spaced around the structural member of interest. Forces applied to the load ring of this casing are transmitted through to the flexible cells causing changes in their internal pressures. These changes in internal pressures then being measured.
The pressure exerted on the immersed casing is dependant upon:atmospheric pressuredepth of immersion below lowest tide leveltide height at any given timedensity of sea waterforce due to tidal velocitywave heightforces due to waves, e.g. drag, inertia and slam
The Influence of Chain Friction on Anchor Pile Design
Authors: Vivatrat Vitoon , Valent Philip J. , Ponterio Albert A. 
Published: October 2008

Abstract
This paper presents a simple and versatile computer procedure for estimating the influence of chain friction on the pile load in an anchor pile-chain system. The chain-soil interaction is modeled in terms of the chain embedment depth, chain characteristics and soil strength profile.
Example predictions are presented to illustrate the relative magnitudes of the vertical and horizontal components of the pile load, and the effects of the embedment depth, chain size and pretension. A limited comparison with some measurements of chain friction at shallow depth is also presented.

Introduction
Anchor piles have been used offshore to provide anchor points for mooring purposes for centenary-moored floating platforms (Figure 1) and are a leading candidate for anchoring the lines of guyed tower platforms. The mooring line has been connected at an intermediate position along the pile length (Figure 2(a)), or at the pile head with the head below or at the mud line (Figure 2(b) and 2(c».
Positioning the pile head and chain connection at the muddling (Figure 2(c)) facilitates full inspection and refurbishment of the chain in long-term moorings. On the other hand, the bending stresses in the pile can be significantly reduced by connecting the anchor chain to the pile at a point below the pile head. The reduction results primarily from the additional end restraint provided by the soil above the chain connection.
In practice, the chain connection point has been located as far down the pile as its mid-point, e.g., see Reference (1). The pile and chain are installed by driving the pile and the reconnected chain together. After some tensioning, the chain will assume a configuration as schematically shown in Figure 1.
A pile-chain connection below the mud line implies that the load applied to the pile will have both a vertical and a horizontal component. The relative values of these two load components vary with the chain configuration, which in turn depends on the tension applied to the end of the anchor chain at the mud line. This paper discusses the influences of the chain soil interaction on the line tension at the pile connection. Example predictions from a proposed computational procedure are presented to illustrate the effects of embedment depth, chain size and pretension.

2. Previous Work
Previous studies of the influence of "chain-soil interaction on chain tension can be divided into two groups: those related to the dragging friction and those related to chain embedment.
Dragging friction on anchor chains was usually studied in the field or in laboratories by dragging a length of loose-ended chain in contact with soil. The results can be presented in terms of an "efficiency" ratio (i.e., dragging resistance divided by weight of chain in air) as summarized in Table 1. The chain in his case generally does not cut into the soil and may not be in full contact with the soil.
Interaction between soil and embedded chain was considered by Reese (4) and Gaunt and Cox (5).