bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of Automatic Underwater Welding With Local Cavity Formation Method
Authors: Tamura Mitsuru , Nishio Yasuhiro , Wada Hirokazu 
Published: October 2008

ABSTRACT
This paper describes the development of automatic underwater welding system based on an unique localized dry environment by a fluid curtain.
With only the welding machine submerged, the system is operated by remote control in the ocean in connection with materials supply and supervision of works, thus considerably reducing its reliance on diving and underwater operations.
In this process, a stabilized gaseous zone can be created only around the welding spot just underneath the welding torch by inclined water jet stream from the outer circumference of the double nozzle. Then various gas shielded arc welding methods such as TIG, MIG and C02 arc welding are performed in the dry environment. (Fig. 1, 6, 11, 12)
As the initial plan, a submersible automatic welding machine has been produced, and the trial test of this system has been successfully performed on objects submerged in a large cistern while supervising and controlling-their welding conditions by TV monitoring from outside the cistern. (Fig. 15, 16, 17) Welding results have proved excellent, being not much different from those undertaken in an ordinary environment on land. (Fig. 13, 14, 18)

INTRODUCTION
From the viewpoint of natural resources development and utilization of space, recognition and concern have been rapidly elevated with regards to the importance of ocean development and thus the conception of super giant ocean projects such as various offshore plants, sub-sea production systems, etc. are being mapped out actively.
For the construction of these gigantic structures, full-scale underwater fabrication techniques are indispensable.
Among these the underwater welding technique is expected to play the most vital role. Thus early development is earnestly desired by various fields concerned.
Up to the present, the two currently available underwater welding are the dry and wet methods.
For the sake of obtaining reliable weld, it is unquestionably desirable to be welded in a dried environment. Dry method; however, requires a special chamber that entirely covers the work, which brings limited use in the shape of object as well as extremely high cost. Wet method on the other hand, has depended much upon submarine work by divers. And because of many points which are still at issue with respect to reliability, efficiency and workability, underwater welding has not yet been put in full-scale practical use.
Recent developed local cavity methods are noted because of their better handiness than that in the dry technique and also the much better reliability than in the wet processes.
The authors have developed a unique local cavity formation process by a fluid curtain and its application to welding, cutting and painting underwater.
This method utilizes the effects of shutting off the water invasion by the momentum of fluid jet and smooth exhausting of cavity gases by flow entrainment.
This paper describes the principle of cavity formation, cavity formation conditions and its application to welding.
Steels for Different Sections of Offshore Structures
Authors: de Boer Harald , de Meyer Lutz , de Schonfeldt Henry , de Thiele Manfred 
Published: October 2008

ABSTRACT
Steels of different mechanical properties and weldability should be used in different sections of offshore structures with regard to their configuration and stress conditions.
Normal strength steels have a good weldability and a high efficiency in welded joints, when fatigue stresses occur.
High strength steels with 355 N/mm2 minimum yield point are weldable fine grain steels with a wide range of applications. However, plates of more than 30 mm thickness must be preheated before welding to avoid cracking. For complicated structures which are loaded by fatigue stresses, like nodes, the weldability and toughness, in particular in the z-direction of plates, have been improved. A high resistance against lamellar tearing was obtained by inclusion control. The development of a high strength steel which is crack free weldable without preheating was achieved by consistently lowering the carbon content, balanced by an increase in manganese. The properties of these two steel types may be combined in one steel which needs no preheating and is resistant against lamellar tearing.
High strength steels with yield points between 400 and 690 N/mm2 can be used in sections where static stresses dominate.
The principles of steel selection with regard to different stresses during manufacture and service are demonstrated schematically for a semi-submersible drilling unit and have already been successfully applied.

INTRODUCTION
Drilling rigs and production platforms for the offshore technology have to meet different requirements depending on their field of operation. This applies also to the steels used for these structures. The Gulf of Mexico will demand other steels than arctic waters and it would be of poor use to build a complete offshore structure out of one type of steel, because there will be different kinds of stresses. The stress analysis shows that those sections which are exposed to wave forces, are mainly affected by fatigue stresses, whereas parts of the platform itself are mainly statically loaded (Figure 1). The quotient out of the minimum and the maximum stresses represents the ratio of the fatigue stresses. As important as this stress ratio is for the design of offshore structures, as important is the weldability of steels for their construction (1). In addition to the weldability the reliability of a structure is a main factor when selecting materials. Under these conditions there may be applied successfully three categories of steels in one structure:minimum yield point below 300 N/mm2minimum yield point about 355 N/mm2minimum yield point between 400 700 N/mm2
Most of the plates needed for offshore structures are 15 - 75 mm thick.
Special metallurgical procedures for the production of particular grades within these categories will be described with regard to their application. Some of these steels have been proved in service whereas others have been recently developed.
Response Of Concrete Gravity Platforms To Earthquake Excitations
Authors: Watt Brian J. , Boaz Irvin B. , Dowrick David J. 
Published: October 2008

ABSTRACT
The earthquake response of typical concrete gravity structures in a 100 to 200m water depth range was evaluated using response spectrum and Fast Fourier Transform solution techniques. A series of parametric studies showed:The analysis method has a marked effect on magnitude and distribution of computed foundation and structural forces.Correct modeling of the foundation compliance, especially radiation damping, is essential.At the lower end of the soil stiffness range, foundation instability governs and at the upper, structural strength.

INTRODUCTION
One of the specialty sessions at the 1975 OTC was dedicated to the subject of earthquake engineering offshore. It was evident from the state of the art presentations at that time, that few if any investigations had addressed the question of the response of concrete gravity type platforms to earthquake influences. This is hardly surprising since the first production platforms of this kind were installed in the North Sea in the summer of 1975 and to the authors' knowledge, none has yet been ordered for an offshore region characterized by high earthquake risk.
One of the chief advantages of the concrete gravity platform is its potential for carrying payload to location and the very limited amount of offshore work required. The advantage of this in a short installation weather window, like that of the North Sea, is only now becoming fully appreciated. The Gulf of Alaska has similar weather characteristics to the North Sea but also is associated with a high earthquake risk. This paper presents a part of an overall investigation into the feasibility of constructing and installing concrete gravity platforms in the Gulf of Alaska. This was conducted from September 1974 through April 1975. At the time the study commenced, there were sound geological reasons for anticipating the presence of suitable founding conditions at or close to the mudline but only limited numerical data existed.

OBJECTIVES
It would be logical to assume that the intensive nuclear power development programme in the 1960's would have generated ample means for evaluating earthquake problems experienced by massive concrete structures. While this is undoubtedly true with respect to an understanding of the basic phenomena and the provision of some of the methodology, certain factors must be remembered. In the first instance, the size in terms of both mass and geometry of a typical gravity production platform is significantly greater than that of a nuclear reactor installation. Secondly, the superstructure of the former is relatively flexible. Thirdly, the interaction with the surrounding water represents a further level of complication in the case of a submerged structure. Finally, in a typical nuclear reactor design situation the emphasis is on the detailed evaluation of a particular site whereas the type of investigation undertaken in this Gulf of Alaska study was geared more to the identification of which type of site would be satisfactory from all view points.
System Model Development of Two Fast Current Oil Removal Systems
Authors: Ard Roswell , Ayers Ray , Beach Robert 
Published: October 2008

ABSTRACT
Presently, the effective removal of oil spills is limited to current speeds of about one knot. There are several high risk areas of the country where currents are in excess of one knot. To be able to effectively recover spilled oil in these areas, the Coast Guard has initiated a program to develop suitable systems. This program and the results to date are discussed herein along with its projected future direction.

INTRODUCTION
The most common technique available today to control oil spills is the floating boom that supports a vertical skirt extending down into the water to form a barrier to the passage of the oil. At currents in excess of about one knot, the oil slick will not be contained by the boom and will flow beneath the barrier as the oil droplets are entrained by the escaping water. This phenomena applies to any oil recovery device that establishes a relative velocity in excess of about one knot between the oil and the water. The effectiveness of these devices is even further limited by the action of winds and waves.
A large number of oil spills occur in rivers, estuaries, and bays with velocities in excess of one knot. Today, the only way of cleaning up spills in these situations is to wait until it is caught by back water areas and then apply conventional clean up techniques. Another aspect of this problem is the slick that has spread out over a vast area. To recover this type of spill effectively requires the capability of rapidly picking it up with a speed of at least three to four knots in order to effectively maneuver.
The opinions or assertions contained herein are the private ones of the writer and are not to be construed as official or reflecting the views of the Commandant or the Coast Guard at large.
The National Oil and Hazardous Substances Pollution Contingency Plan gave the Coast Guard the responsibility of removing oil discharges on the waters of the United States. Since the fast current problem existed in many of these waters, the Coast Guard initiated a program to develop a suitable oil spill recovery system.

INITIAL RESEARCH
The initial part of this program consisted of two parallel efforts. One of these efforts was to investigate the feasibility of various processes to recover oil in a fast current situation. The other was to determine suitable support systems and the environmental factors that would be encountered in trying to pick up oil in a high current situation.

Process Feasibility Study
A study by Texas A &M investigated the behavior of a floating oil slick subject to various external mechanical influences and to the action of current and waves. Oil diversion schemes, rapid removal techniques, and energy absorption barriers were evaluated. Energy dissipation and rapid removal by lifting appeared to have the most promise for fast current oil recovery.
Cathodic Protection of Offshore Support and Security Craft
Authors: Morgan John 
Published: October 2008

INTRODUCTION
A hundred years ago Thomas Edison investigated in his laboratory the corrosion of iron ships' hulls in seawater. He carried out these experiments in model form and predicted a catastrophic corrosion problem. He was not content to leave it there and with his usual genius designed and indeed operated an impressed current cathodic protection system on board a United States ship.
It was not a great success both because of the materials he had available but also because in scaling down the experiment he had in reality investigated the turbulent conditions that are found at the stern of a vessel associated with a steel propeller and with steel brackets and nozzles.
Perhaps this paper repeats much of Edison's work, it certainly proposes the same solution and application to cure the same conditions that were reproduced a hundred years ago in that famous laboratory.

PROPELLER AND TURBULENT WATER CATHODIC PROTECTION
The current that is required to achieve cathodic protection depends on the rate of arrival of oxygen at the cathode surface and an empirical relationship exists between speed and the cathodic protection current density. At a highly turbulent surface however the corrosion is enhanced by differential oxygen cells caused by variations in the partial pressure of the oxygen in the water. This type of attack, often called impingement corrosion, is evident on many vessels, principally in the stern area, on the propeller blades, on the leading edge of the rudder and on the A and P brackets.
A propeller blade will suffer a more extreme form of attack which is usually called cavitation damage and this is the corrosion of the metal at the point of cavity collapse. Cavitation is usually considered to be a mechanical attack and it has been claimed that it can be reproduced with ultrasonics. However if we consider the collapse of one of these cavities we can formulate an electrochemical mechanism for the corrosion.
The cavity that will be formed in the liquid will be at extremely low pressure and because of this will be completely ionised. The liquid surface of the cavity as it collapses will travel towards the metal of the propeller blade and will pick up an electric charge from the ionised gas. It will probably do this unequally and there will be a resultant charge left on the surface of the metal. This charge will disperse into the liquid and metal and in doing so will cause corrosion.
If we-consider a cavity of 1 cc capacity at 100th of an atmosphere pressure and forming two singly charged ions in the space then we can estimate a current that might flow if the whole of the charge were completely separated at each collapse.
Applications for Olver Lockout Submersibles
Authors: Holland Robert H. 
Published: October 2008

ABSTRACT
This paper will describe recent industrial applications of diver lockout submersibles operating in the North Sea. Types of tasks which can be accomplished more efficiently and economically with diver lockout submersibles will be identified. Innovative solutions to problems presented by lockout submersibles will be discussed, as well as specific oil field applications of diver lockout capabilities and comparisons of diver lock out capabilities with other types of underwater work.

INTRODUCTION
The technique of divers exiting and reentering the confines of submarines while submerged is not new. In fact, it has been used in varying forms by the armed forces since World War II. From these generally clandestine type operations has evolved the diver lockout from submersibles as exists within the offshore oil industry.

HISTORY
This process of evolution has not been one of joint development, but more one of converging the paths of two individual services set up to supply the ever increasing demands of an industry under pressure to satisfy energy needs of modern civilization. These demands have caused the search for oil and gas to expand from land to the sea bed of the continental shelf, which in turn produced the requirement for the underwater worker. Initially, while in shallow water, the scope of operation of these underwater workers/divers was satisfactory, but as exploration, construction, and the supporting maintenance moved further a field and into deeper water, so the diving technique had to change. Now the diver needed a bell or chamber from which to dive and larger support systems, such as deck decompression chambers, on the surface to maintain him. The handling of the bell from the surface and the ability to position that bell in the close vicinity of the job required a platform of considerable size that could be positioned accurately and held in that position irrespective of the natural elements.
This was achieved by either heavy mooring or dynamic mooring systems, which on the one hand is a time consuming process with ever present danger of anchors dragging and causing damage to subsea equipment, or on the other hand a very sophisticated and expensive system which is generally installed in the larger type of vessel.
While the demands on the diver were increasing depth-wise and his range of operation from the surface base reduced, so the submersible was developing to cope with the demands for survey and inspection work over on an every increasing area. The "shirt sleeve" environment of the submersible provided the ability for survey and inspection of as much as 8 or 9 km of pipeline per day, where in many cases, a diver would be hard pressed to cover as much as 1.5 km per day. Also with the use of manipulators certain simple engineering tasks could be performed by the occupants of those submersibles.
LNG: From Ship to Shore
Authors: Peraino J. , Chase B.L. , Plodowski T. , Pupko H. 
Published: October 2008

ABSTRACT
An LNG (liquefied, natural gas) unloading terminal - the largest in the U.E and second only to one in Japan - has been designed by Raymond Technical Facilities Inc. (RayTech), for Columbia LNG Corp. and is nearing completion at Cove Point, Md., on the Chesapeake Bay. Tankers will be unloading Algerian ING at offshore berths from where it will be piped to shore, still as a liquid at -260 °F through a mile-long sunken-tube tunnel. This is the first such application of tunnel construction for carrying LNG. The original terminal design had provided for a conventional pile-supported trestle with pipeway and roadway from the offshore berths to the onshore storage and regasification plant. However, in view of the situation of the terminal in a relatively unspoiled, recreational area, and, particularly of the wetlands area with its value to the over-all local ecology, objections were raised by environmentalists resulting in the substitution of the tunnel for the more visible trestle.
This concept entailed major changes throughout the project. However, once the change was judged worthwhile and economically tolerable by the owners, the work has proceeded as expected with the added attraction of the preservation of many acres of land as a wildlife refuge and recreational area.

INTRODUCTION
With depletion of oil and gas fields within the U.S. coming simultaneously with vastly increased energy demand, the importation of natural gas from foreign countries has become increasingly necessary. By liquefying the gas (by reducing its temperature to -260 °F and, thus, its volume to 1/600 of the original) and by the development of special ships for its importation into the U.S. from the oil and gas fields or Africa, the Middle East, Indonesia, Alaska, etc., a much needed new source of energy has been made available.
Columbia LNG Corp., a subsidiary of the Columbia Gas System Inc., in 1970 started planning for LNG importation through a terminal second in size only to one already operating in Japan. The marine terminal and pipeline for the $30$ million complex at Cove Point, Md., will permit the unloading of the equivalent of a billion cu ft/D (28 million cu m) of natural gas imported from Arzew, Algeria.
Raymond Technical Facilities Inc. (RayTech) a wholly owned subsidiary of Raymond International Inc., was first authorized by the owners in July 1970 to perform site investigations and to prepare preliminary designs and budget estimates of construction cost for the marine terminal to berth, unload, and service the new generation of 125,000 cu m ING tankers coming into use. RayTech was later committed to perform the final design including the preparation of working drawings, specifications, and bidding documents for all structures from the berth line to the contract limit interface, at the onshore tunnel shaft.
Implications Of Plate Tectonics For Offshore Gulf Of Alaska Petroleum Exploration
Authors: Rogers John F. 
Published: October 2008

ABSTRACT
The Gulf of Alaska is coincident with a converging plate boundary, along which the Pacific plate under thrusts the North American plate. Evidence of this interaction shows up in the deformational pattern of offshoreTertiary strata, as well as the sedimentary record.
A broad belt of compressional structures attributable to plate movement can be traced along the continental shelf and slope of the western Gulf of Alaska, parallel to the Aleutian trench. This field cuts diagonally across the continental shelf of the central Gulf of Alaska, splaying into the Fair weather fault system in an area north and west of Yakutat. Structures within this compressional field show evidence of sequential development - from northwest to southeast.
Tertiary sediments record a history of southeastern migration of the "Aleutian" trench, and a tectonic incorporation of early Tertiary oceanic", trench and slope sediments in a late forming continental shelf, all in response to episodic, but persistent plate convergence.
The implications of plate tectonics for exploration is significant. Knowledge about timing of structural growth, and distribution of reservoir and source rocks is vital to an exploration program. Plate tectonics is not an oil finding tool but a unifying concept to which one may relate the required interpretations about structure and stratigraphy.

INTRODUCTION
The concept of global plate tectonics is becoming more and more important to petroleum geologists exploring the Gulf of Alaska. There, two segments of the earth's crust, the Pacific plate and the North American plate, interact in an area where one major O.C.S. lease sale has recently been held, and others are scheduled for the future.
The most promising areas for petroleum potential in the Gulf of Alaska are in the northern Gulf where O.C.S. Sale 39 was held in April 1976, and in the western Gulf where O.C.S. Sale 46 is tentatively scheduled for November 1977 (Fig. 1). In both areas, petroleum potential lies in Tertiary sediments. Folding and faulting took place in Tertiary time. Both stratigraphy and structure have been affected by the plate-tectonics environment of the region and the time.
The regional geology of this area has recently been described by various U.S.G.S. workers.1, 2 Fig. 2 is a vastly simplified geologic map. Mesozoic rocks border the Gulf of Alaska onshore. They are highly deformed and metamorphosed to some extent, and probably have no petroleum potential in the region. Early Tertiary sandstones, shales and volcanics of deep marine (in the west) and shallow marine and non-marine (in the east) environments form the next outcropping belt seaward. They too, are highly deformed. Petroleum potential in these rocks depends on their being found in a location where the degree of deformation is less, and where there is reasonable expectation of reservoir sand development. Late Tertiary rocks outcrop in the next, more seaward out Crop belt.