bluuebunny/crossref_metadata_2025_split huggingface dataset:
Underwater Welding of Mild Steel a Metallurgical Investigation of Critical Factors
Authors: Nagarajan Yedapurisan , Loper Carl R. 
Published: October 2008

ABSTRACT
Underwater welding of mild steel (without" mechanical shielding of the arc) was performed in the laboratory using a tank with continually circulating water. U groove welds (A.W.S.BU6) and square groove butt welds (A.W.S.BPlb) were made (E60l3 electrodes): In the first case, the welds were cleaned by wire brushing and shot blasting between passes, while in the latter case the back side was additionally ground. When thoroughly cleaned, the welds showed an improvement in ductility from the original 15% R.A. to 30% R.A. Bead on plate tests were used to compare E6013, E6020, and E7024 electrodes. Crack free welds were obtained only with E7024, with the crack susceptibility of E6020 intermediate.

INTRODUCTION
Though it has been recognized that the properties of the welds produced under water are inferior to those of surface welds, the actual effects of the water medium are still not clearly understood. With a growing interest in offshore construction, interest in the area of underwater welding has been revived in recent years (l,2,3,4).
In addition to faster cooling rates experienced in underwater welding, the introduction of harmful hydrogen in the weld metal and structural inhomogeneities, e.g., incomplete fusion and slag inclusions, are inevitable. Further due to the production of gases from the electrode covering, and the dissociation of steam into hydrogen and oxygen, a fair amount of porosity is also present in the structure. It is known that when the cooling rate of the weld metal exceeds a certain critical rate in the presence of hydrogen, microfissuring occurs, however, an investigation that considers all pertinent factors is still required.
The research study briefly reported here is the result of preliminary investigations of the critical factors that affect the mechanical properties of the mild steel welds made under water. This study was carried out in three phases:Phase I - Preliminary studies on U groove welds.Phase II - Cleaning procedure modifications and studies on butt welds.Phase III - Bead on plate welds to study the conditions under which micro cracking could be controlled.

EQUIPMENT AND MATERIALS

Tank and Accessories
The welding reported in this study was performed in a p1exig1ass tank 18"×18"×15" in size. The water depth at the work table was 9 inches. Continuous circulation of water was used to avoid turbidity, thereby improving the visibility.
A periscope was constructed and attached to the outside of the tank and provided the welder with a clear view of the arc despite the turbulence of the boiling water. Welding guides were used to aid the welder in laying a straight bead. A schematic arrangement of the tank and accessories is shown in figure 1.
The welding power source was a 300A capacity motor generator with an open circuit voltage of 40V.
Development of an Unmanned Deepwater Pipeline Repair System
Authors: Bline Donald B. , McDonald Wm. M. 
Published: October 2008

ABSTRACT
A pipeline repair system has been designed for performing all tasks required to locate, assess, and repair damage to pipelines in water depths beyond diver capability. Trade-off studies indicate that the system is also applicable for water depths within diver capability. A cooperative industry development program sponsored both the detailed preliminary design for the entire system and detailed fabrication level design of critical components. Critical components have or will undergo model and prototype testing. The system is designed to be able to perform such activities as soil excavation, pipe-coating removal, pipe cutting, end preparation, and transport and positioning of replacement sections. The technology to implement these activities constitutes a significant advance in offshore pipeline repair technology when combined into a single system.

INTRODUCTION
The capability to repair marine pipelines damaged by corrosion, storms, earth movement, third parties, etc. in water depths beyond the practical reach of divers is a near-term requirement for offshore oil and gas producing operations.
To meet this requirement, a cooperative industry program to develop an unmanned pipeline repair system was initiated in late 1973. The result of this program was a detailed preliminary design of equipment and procedures as well as prototype testing of selected critical components.

SYSTEM DESCRIPTION
The basic system consists of two separate vehicles for deployment of tools and pipe-repair components to the seafloor work site. The Work Vehicle (WV}, Fig. 1, is an unmanned, umbilically tethered, tool platform used for observation, excavation, pipe preparation, and light manipulative tasks. The Vertical Transport Vehicle (VTV), Fig. 2, is a buoyant, umbilically tethered, heavy load lowering platform for transporting the large, heavy pipe connection and replacement equipment. In areas where relatively calm seas persist, two large workboats could be used to deploy these vehicles. Other equipment includes a power and control cable to each of the two vehicles, plus the pipeline repair and replacement components.
A key feature of the repair system is that it can adapt to a wide variety of damage situations including damage to a buried pipeline. The design is based on a maximum diameter of 36-in for a concrete coated pipe. Equipment is designed for a depth of 4000 ft, but the system is relatively insensitive to water depth.(Equation available in full paper)

Structure.
Principal elements comprising the vehicle are two mirror image trussed hull structures joined at their top by six composite beams upon which are attached six buoyancy units. The hulls are completely floodable simple trusses having a light-weight sole plate and a sheet fairing on the outboard sides. All structural elements are of special alloy aluminium. The hulls carry the principal items of machinery including electric motors, hydraulic systems, switch gear, etc.
Block Erection Method of Maui "A" Tower
Authors: Kawakatsu Yasuo , Matsubara Hiroyoshi , Watabe Takashi , Shiroichi Akira 
Published: October 2008

ABSTRACT
This paper introduces the block erection method used to assemble the Maul 'A' Tower an offshore platform located 21 miles off the Taranaki coast of New Zealand's North Island. Descriptions are given herein ofthe block erection concept applicable to the various components of an Offshore platform,the materials used in the main sections of the tower, andthe assembly procedures.
The principal characteristics of the tower and the shipyard where it was fabricated and assembled are also outlined, as are the tower flotation procedures and the benefits of the block erection method over the conventional panel erection method.

INTRODUCTION
Shell BP and Todd Oil Services Limited (SBPT) discovered the Maui field some 30 miles off the South Taranaki coast in early 1969 on a prospecting license area of 11, 030 square-miles. The field is being developed by Maui Development Limited, a joint venture company operating on behalf of the New Zealand Government (as Offshore Mining Co. Ltd.), 50%; Shell (Petroleum Mining) Co. Ltd., 18.75%; BP (Oil Exploration) Co. of New Zealand Ltd., 18.75%; and Todd Petroleum Mining Co. Ltd., 12.5%.
On behalf of Maui Development Limited, Shell BP and Todd Oil Services Limited is the operator responsible for design, procurement, construction and operation of the platforms, submarine pipelines, and onshore processing facilities.
Project plans called for a gas and oil drilling and production platform to be installed at the site in a water depth of 108 meters. In April 1974 our company was awarded the contract by SBPT to build the tower support structure for the platform. Seventeen months later, in September 1975, the tower was delivered to the client.
Besides being one of the world's largest structures of its kind, the Maui 'A' tower is also the world's first self-buoyant tower of this type and for this water depth ever erected. Further, delivery involved the world's longest tower tow, some 9,200 km. The principal particulars of the tower are: height, 131.674 m; breadth (leg center to leg center), 21.366 × 48.768 m (top), 47.854 × 48.768 m (bottom); leg diameters, 6.706, 4.877 and 1.829 m; maximum wall thickness, 95.3 mm; total weight, 6,400 metric tons (tower, 5,174 tons; accessory structures and systems, 831 tons; piping systems, electrical equipment and wiring supports, 395 tons).
High-strength steel produced to DIN specifications are used in the principal members of the tower, while a steel produced to satisfy DIN specifications for mechanical strength in the through thickness direction is used in the nodes.
The tower was assembled at our Tsu Shipyard (refer to Fig. 1) by the block erection method the first time this method has been used to assemble an offshore structure. This was the principal factor that permitted the completion of the tower in a record time of 17 months.
The Experimental and Theoretical Study of a Tension Leg Platform in Deep Water
Authors: Yashima Nobuyoshi 
Published: October 2008

ABSTRACT
The offshore industry is going into deep water exceeding 3,000 ft.
The tension leg platform Js available for exploratory drilling, supporting production equipment, and work over operations in such deep water.
The moored stable platform with a buoyancy exceeding the weight has tensioned vertical anchor cables. The tension leg generally consists of wire ropes with elasticity that cannot be ignored in deep water.
The elongation of the anchor cables results in roll, pitch, and heave motions of the structure. These three motions are small and, therefore, have no significant effect on the actual field operations; however, in extremely deep water the vertical motions are not negligible.
In order to evaluate the effect of elasticity of the anchor lines in deep water, we made a 1/50 scale model of a tension leg platform that has four vertical cylinders and four anchor lines. Hydrodynamic forces acting on the cylinders were calculated by considering the radiation and wave exciting forces vertically and the drag and inertia forces horizontally. We recognized through the theoretical study and model experiments that more elasticity in the tension cables would result in less tension variation of the cables in motion response by waves, and investigated the nonlinearity of motion response to regular waves under steady state forces such as wind, current and wave drift.

INTRODUCTION
Floating vessels, such as a drill ship and a semisubmersible drilling rig, experience more heave, pitch, and roll motions as sea conditions become rougher and water depths greater, resulting in costly downtime. However, the tension leg platform, which is held firmly in place by vertical anchor cables, results in less motion response to heave, pitch, and roll even in deep water.
This is because the cable tension prevents vertical motions, and acts to lessen horizontal motions. The tension leg-platform concept is adaptable to several specialized types of offshore oil structures such as a production platform and a workover unit for servicing subsea wells.
Similarly, the amplitude of the tension Variations between the maximum end the minimum cable tension by a regular wave could change, depending upon the magnitude of the steady state forces. Fig. 7 shows the tension variations of Cables 1, 2, 3, and 4 in Case B, in which the external forces ere horizontal force components of a wave with a period and height of 1.5 seconds and 10 cm, respectively, end steady-state forces.
The natural periods of heave, pitch, and surge of the 1/50 size model me shown in Table 1. Cases A, B, C, and D indicate the different property characteristics of the cables as shown in Fig. 5. (There are no legs in Case D).
Nevertheless natural periods of surging in Case: A, B, and C are not very different; that is, these periods. not significantly dependent upon the elasticity of the tension cables.
Performance Tests of Off-The-Shelf Oil Skimmers
Authors: Griffiths Richard A. 
Published: October 2008

ABSTRACT
Five advancing-type commercially available oil skimmers were tested at the EPA's OHMSETT facility. Four were found to be low speed devices, with very low thruput efficiency at speeds greater than 1.25 kt to 1.5 kt.
One device, the Cyclonet, recovered oil best at speeds of 4 kt to 6 kt. Typical oil recovery rates were 10 gpm to 20 gpm. Improvements in the design, use, and testing procedures for these types of skimmers are suggested.

INTRODUCTION
During July 1975 the U. S. Coast Guard Office-of Research and Development sponsored tests of five off-the-shelf oil- recovery devices at the EPA's OHMSETT facility. The tests had four objectives:to develop a standard test procedure for testing oil recovery devices,to familiarize Coast Guard Strike Teams with the devices tested,to assist in the evaluation of these skimmers for purchase as operational equipment, andto evaluate these skimmers for use in fast currents.
The oil skimmers tested are considered representative not only of each manufacturer's products but of different generic types of skimmers. Interpretation of the test results, then, enables one to evaluate each particular device, to consider design advantages or disadvantages (or possible improvements) of each type, and to criticize and improve the test procedures.
A complete evaluation of a device must involve additional considerations besides oil recovery performance. Testing the full scale, prototype devices in a large-tank such as OHMSETT also allows a qualitative evaluation of practical problems encountered when using a skimmer, such as set-up time, ease of operating, demobilization and cleaning problems, and support equipment, manpower, storage, and maintenance requirements.
A comprehensive report with test details will be released soon by the Coast Guard and will be available through NTIS.

TEST PROCEDURE AND RATIONALE
The test plan was basically the same for each device, with oil distribution rate, tow speed, etc. adjusted to suitable values. Each plan began with an investigation of the effects of speed on performance and determination of the "optimum speed" followed by investigation of the effects of encounter rate, waves, and oil type. In each test an attempt was made to achieve "steady state" conditions, defined as the average operating conditions during several hours of continuous skimming. In general this meant establishing a stable slick in front of the device and filling basins, sumps, pumps, and hoses with fluid recovered under such conditions.
Three measures of-performance were of general concern: (oil) recovery rate; recovery efficiency, defined as that percent of the recovered fluid which is oil; and thruput efficiency, defined as that percent of the oil encountered which is recovered.
A lube oil and ½ fuel oil were selected for testing. The oils were reused repeatedly during the four week test period with gravity separation of the water between uses. The following were the average properties over the period:(Available in full paper)
Structure And Possible Petroleum Traps Of Lower Cook Inlet, Alaska
Authors: Fisher Michael A. 
Published: October 2008

ABSTRACT
The regional structure of lower Cook Inlet is a large northeast-trending syncline that extends the width of the inlet. The syncline, which involves Mesozoic and Tertiary rocks, is divided into two oppositely-plunging synclines at the latitude of Augustine Island by the Augustine Seldovia arch. This arch trends east-west, transverse to the axis of the lower Cook Inlet basin, between Augustine Island and the Kenai Peninsula near Seldovia. A number of anticlines have their axes parallel to the basin axis and intersect the arch at oblique angles. Domical structures could be formed where the two structural trends intersect, providing a possible setting for petroleum entrapment. The northeast-trending anticlines also may be structural traps. Seismic data reveal a number of unconformities in the offshore area. In particular, a regional angular unconformity interpreted to separate Mesozoic and Tertiary rocks extends northeastward along the southeast coast of lower Cook Inlet. Truncated strata beneath this unconformity may contain combined structural and stratigraphic traps.

INTRODUCTION
Lower Cook Inlet is the southern half of an intermontane basin in south-central Alaska (Fig. 1). On the southeast side of the inlet are the towns of Homer and Seldovia, along the northwest coast are Cape Douglas; Augustine Island, and the Iniskin Peninsula.
Two seismic surveys that provide public information were conducted in lower Cook Inlet. In July, 1975, the U. S. Geological Survey contracted with Western Geophysical, Inc. to collect 480 km of common-depth-point (COP) seismic data using a 2,700-m, 72-channel streamer, Aquapulse guns, and DDS-888 digital instruments. The grid of seismic lines is about 30 km square. A combined Raydist/RPS navigation system located shot seismic data was processed by Petty-Ray Geophysical, Inc. Copies of the 36-fold final stack sections and shot point maps are available to the public through: National Geophysical and Solar Terrestrial Data Center, Code D-62l, Boulder, CO, 80302.
A second seismic survey was conducted in July 1976 aboard the R/V SEA SOUNDER, a vessel operated by the U. S. Geological Survey. A 30-kiloJOUle sparker system obtained data along track lines that form a grid about 15 km square. Some sparker lines are in the same locations as the CDP lines. Although the sparker data has about one-tenth of the sub bottom penetration of the COP data, axes of structures in Tertiary rocks can be clearly seen. The COP lines are too widely spaced to define the extent of structural axes, but show the regional configuration of deep strata beneath lower Cook Inlet.
Three seismic horizons were correlated throughout the grid of COP lines; all three are too deep to be seen on the sparker data. In order of increasing depth, the horizons are labeled A, B, and C. The A-horizon is believed to be at the base of Tertiary strata; the B horizon might be at the base of Upper Cretaceous strata; the C-horizon may be near the base of Upper Jurassic strata.
Extending Seismic Design Provisions For Buildings To The Design Of Offshore Structures
Authors: Sharpe Roland L. , Newmark Nathan M. 
Published: October 2008

ABSTRACT
The philosophy and background of seismic design provisions for buildings are discussed. The applicability of design assumptions and provisions used for buildings to extremely tall, slender, and flexible offshore structures is reviewed. Offshore structures are much bigger in plan than most buildings and do not have a common foundation. Hence they may respond in torsion as well as translation to seismic motions. Moreover they are surrounded by water that causes different types of actions and response to dynamic inputs. The significance and possible effects on offshore structures of major earthquake motion characteristics are presented. Areas that require detailed study are described.

INTRODUCTION
Earthquakes are of special interest because they can affect most components of a structural system and the equipment supported thereon. Earthquakes occur at irregular time intervals and transmit transient dynamic ground motions which can induce large forces in man-made facilities. The response of structures and their contents to such dynamic motion is a very complex phenomenon.
There has been a tendency in most parts of the United States to view earthquakes as a California problem. However, over 70 million people in 32 states are subject to major and moderate earthquake risks, that is, earthquake motions with effective peak ground accelerations exceeding 0.l0g. If it is assumed that the seismic design regionalization maps recently developed by the Applied Technology Council (ATC) can be extended offshore, about 41 percent of the East Coast, 80 percent of the West Coast excluding Alaska, all of the Gulf of Alaska including the Aleutians, the Bering Sea coast up to about 60 degrees north latitude about one half of Hawaii, and much of Puerto Rico are subject, to effective peak ground accelerations exceeding 0.10g.1
Until recently few offshore structures have been built in active earthquake areas. Most offshore structures have been constructed in the Gulf of Mexico, a re1atively Quiescent seismic area. A few structures have been built off the southern California coast and in Cook Inlet, Alaska. For the Cook Inlet structures, the forces exerted by ice packs were more severe than those from earthquakes. The design of most of the southern California structures followed the Uniform Building Code (UBC) requirements for buildings, with each company using earthquake engineering consultants, as appropriate.
The increasing energy crunch and impending future shortages have sparked an upsurge in interest in developing the potential oil reserves existing in the outer continent shelf (OCS). Activity is largely centered in the Gulf of Mexico, southern California coast, Gulf of Alaska, and the mid-Atlantic coast. Of these areas, those off southern California and the Gulf of Alaska are in seismically active areas. The earthquake problem is not unique to the United States, and offshore developments near New Zealand, Indonesia, and the Philippines are also subject to major earthquake motions.