The Submarine Pipeline

And Single Buoy Mooring Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1969/1/157/1737643/2169-3358-1969-1-157.pdf by guest on 29 September 2021

S.W. Small Manager of Marine Engineering Pipeline & Production Service Division Bechtel Corporation, San Francisco, Calif.

Abstract harbors or building new facilities to accommodate these The subject of the paper is introduced by means of a ships. Even so, there will still be numerous locations where description of the submarine pipeline-single buoy mooring of this magnitude is either physically or economic- system. This description covers the components of the ally not feasible. Nearly all protected harbors on the east system, its purpose and its operation. coast of the United States fall into this latter category.

Discussion then centers on pollution prevention in the In those areas where the provision of a protected berth design and operation of such a system. In discussing design, is not feasible an open-water berth must be used. each component of the total system is discussed. These are the submarine pipeline, the bottom manifold, the under- There are a number of types of facilities presently used buoy hose, the buoy and the floating hose strings. to load or off-load tankers in open water. These include sea islands, spread moorings, single point mooring structures Discussion of operation of the system points out that and single buoy moorings. Of these, the single buoy methods of operation vary from one terminal to the next mooring (Figure 1) has been most frequently installed to depending upon local conditions and the operator's prefer- service today's very large tankers. ence. However, a generalized description is given of mooring the tanker, connecting the floating hoses, loading The popularity of the single buoy mooring stems from or off-loading cargo, disconnecting the floating hoses and the fact that it can be installed at almost any offshore leaving the mooring. location where deep water is relatively close to shore. Water depth can be selected to suit any required tanker draft. In conclusion the paper summarizes those areas of Nearly the only limitation is that the buoy must be design and operation that must receive critical attention to installed a safe distance from shoal water that could maximize the pollution prevention aspects of the system constitute a danger to the tanker while mooring or and to insure that these systems continue to improve and unmooring. continue to have a low risk of pollution associated with their use. The submarine pipeline and single buoy mooring sys- tem, shown schematically in Figure 2, consist of a The rapid growth in tanker size that has taken place in submarine pipeline from the on-shore tank farm, a bottom the last decade is common knowledge. This growth in manifold at the end of the submarine pipeline, underbuoy tanker size has brought with it the problem of how to hose connecting the bottom manifold with the buoy, the service these very large ships at loading and receiving buoy itself, and one or more strings of floating hose terminals throughout the world. The deep draft of these between the buoy and the tanker. When moored to the vessels precludes the use of most protected harbors. buoy, the tanker can rotate or weathervane to minimize the combined of wind, and . A few harbors in Europe have the depth required to handle 200,000 to 300,000 dwt tankers. Numerous other The submarine pipeline and single buoy mooring system harbors in Europe and other parts of the world have was first put into use in 1959. Since that time there has projects planned or underway for deepening existing been a continuous increase in the number of single buoy 157 Hydraulics. The principle criteria for hydraulic design are the rate of flow for loading or offloading the tanker and the available head for . The piping system is then designed for an acceptable pressure drop. The hydraulic design must deal with the entire system from the tank farm to the tanker. The design optimizes the sizes of the submarine pipeline, the underbuoy hose, the buoy manifold piping, and the floating hose. are generally low. For an offloading situation the pressure is usually around 100 psi but can be as high as 175 psi. In a tanker loading situation the pressure at the shore end of the submarine pipeline can be relatively high even though the pressure at the tanker manifold is generally as low as 10 to 20 psi. With

the high loading and offloading rates characteristics of very Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1969/1/157/1737643/2169-3358-1969-1-157.pdf by guest on 29 September 2021 large tankers, high surge pressures are possible. This problem must be eliminated by avoiding the use of quick-closing power-operated valves. Figure 1. Tanker at the single buoy mooring. Strength. The submarine pipeline must have strength as mooring installations around the world. (Figure 3.) Recent a conduit for fluids, as a beam and as compression or tabulations show a total of 46 installations located in 23 tension member. It is an engineering structure subjected to different countries (Figure 4). Most of the installations put a complex variety of loadings both during its construction into service since 1965 have been designed for 100,000 dwt and subsequently during its operating life. Stresses due to tankers or larger. Early next year a buoy designed to service internal or external pressure, in one or more planes 350,000 dwt tankers will be commissioned. and axial tension or compression occur at various times and in various combinations. The force systems causing these During the decade that the single buoy moorings have stresses are both static and dynamic and they are applied been in use there have been only a few relatively small oil both internally and externally. The internal are spills associated with their operation. Because of the caused by the fluid conveyed, and the external force system increasing popularity of the submarine pipeline and single includes forces caused by currents, , hydrostatic buoy mooring system and its use for ever large tankers, it is pressure, soil pressure, frictional forces, and restraints at extremely important that designs be adequate and opera- anchors. Structural analysis is difficult and in some cases tion be carefully controlled. precise theory is lacking. Even so, it is possible to make a rational design analysis. By using the best of available technology and by taking a conservative approach where System Design theory is weak, a safe, economical, design can be realized. The submarine pipeline and single buoy mooring is a system. Each component, or subsystem, comprising the Durability. To be durable, the submarine pipeline must total system must be adequately design for the particular stay where it is constructed. It must not be subject to service that it must provide. "The chain is no stronger than movement by natural forces and it must be protected its weakest link," and the prevention of oil spills depends against abrasion and in the marine environment. upon every subsystem properly performing its function. The pipeline stability problem differs depending upon whether the pipe is laid on the bottom, anchored to the Submarine Pipeline bottom or buried in the bottom. Exposed pipelines are The submarine pipeline design must consider hydraulics, subjected to hydrostatic and hydrodynamic forces. Buried strength and durability. pipelines are subjected to both soil pressures and hydro- static pressures. An exposed, anchored pipeline is subject to a combination of all of the preceding force systems.

An exposed pipeline must be designed with sufficient submerged that it is immovable under the action of BUOY drag, lift, and inertial forces due to currents and waves. Current forces are relatively steady and their effect on an TANK FARM exposed submarine pipeline are reasonably well understood. Figure 5 illustrates the force system on a submarine pipeline in an current. The lift and drag produced by SUBMARINE PIPELINE- the current and the must be offset by the weight and soil reactions in the system if the pipeline is to be BOTTOM MANIFOLD- UNDER-BUOY stable on the bottom. In cases where the weight and soil HOSE reactions are insufficient, some method of anchoring can be used. The resulting force system on one type of anchored submarine pipeline is shown in Figure 6.

The action of the waves on submarine pipelines does not Figure 2. Schematic of the submarine pipeline - single buoy appear to have been sufficiently researched. Methods for mooring system. determining wave forces on a pipeline resting on the 158 Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1969/1/157/1737643/2169-3358-1969-1-157.pdf by guest on 29 September 2021

Figure 3. Geographical distribution of the submarine pipeline - single buoy mooring system. bottom have been developed but their validity has not been pipeline to be stable. The length of bottom spans must be tested. Figure 8 is a schematic representation of the water controlled so that harmonic vibrations are not set up by the particle trajectories in ocean waves. The particle velocities hydrodynamic forces associated with waves or vortex result in lift and drag forces while the accelerations create shedding. inertial forces. A representation of the possible sequential combinations of these forces due to a passing wave is shown Submarine pipelines are generally protected against the in Figure 9. Buried submarine pipelines must have a effects of corrosion and abrasion by a coating and jacketing submerged weight that will assure that they neither sink nor system. A corrosion protective coating is first applied to the float in the event of liquifaction of the marine bottom due bare pipe. This coating is often either a conventional to either differential pressures or seismic shock waves. The pipeline coat and wrap system or somastic. Other systems forces acting on a buried submarine pipeline are shown in such as epoxy coatings, extruded plastic coatings, and Figure 7. The forces must be in equilibrium for the sprayed thermo plastic coatings are also used. A reinforced

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Figure 4. Growth in number of the submarine pipeline - single Figure 5. Force system on an exposed submarine pipeline in a buoy mooring systems. current. 159 submarine pipeline. The bottom manifold can, however, BUOYANCY & LIFT DIRECTION also serve several other important functions. Valves should OF CURRENT be provided at each underbuoy hose connection to permit SADDLE t - isolation of that hose for maintenance, replacement, or damage control. A sphere or scraper can be placed in the end of the submarine pipeline, beyond the underbuoy hose connections. This, along with a flooding valve at the end of the pipeline, will permit sea water to be used to displace oil SOIL for maintenance or repair. Provision should be made for REACTIONS anchoring the bottom manifold. Movement of this manifold ON ANCHOR could be detrimental to both the submarine pipeline and the underbuoy hoses. Figure 10 is a photograph of a bottom manifold used with a 42 inch diameter submarine

pipeline. Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1969/1/157/1737643/2169-3358-1969-1-157.pdf by guest on 29 September 2021

Underbuoy Hose

Figure 6. Force system on an exposed anchored submarine pipeline The underbuoy hose strings are made up of 25 to 35 foot lengths of smooth bore, heavy duty, reinforced cargo in a current. hose flanged together. Hoses up to 24-inch diameter are concrete jacket is applied over the corrosion coating. This currently in use and 30-inch diameter hose is said to be serves several purposes. It protects the corrosion coating available. from damage during construction, it protects the submarine pipeline from abrasion and it supplies the required sub- The two methods commonly used for installing the merged weight for stability of the submarine pipeline. In underbuoy hose are based on the lazy "S" and the addition to coating and jacketing, submarine pipelines bow-legged configurations. These are illustrated in Figure should be protected from corrosion by a cathodic pro- 11. The lazy "S" configuration uses a steel buoyancy tank tection system. can be either an or tanks flanged into the hose string to obtain the desired impressed current system, or a galvanic system using curve. The bow-legged configuration is usually obtained by sacrificial annodes placed at intervals along the pipeline. the use of external foam plastic flotation collars.

Under some circumstances, the submarine pipeline must In either configuration the length of hose must be always be buried. For example, the pipeline must always be selected so as to avoid chafe either on the bottom, the buried when it passes through the surf or breaker zone. anchor chains or the buoy, and at the same time accommo- Experience has taught us that hydrodynamic forces in the date anticipated movements of the buoy. The length is can be extremely high. Further, there is a usually established either by graphics or by the use of a continuous and somewhat unpredictable movement of the three-dimensional model, taking into account the tidal marine bottom in this zone. Another situation which range and the vertical and horizontal excursion of the buoy requires burial is one where the pipe, if exposed, would be resulting from wave action and mooring forces. subject to possible damage by dragging anchors, fish trawls, or other "outside" agencies. Under such conditions it may The Buoy be necessary to specify a cover of up to 15 feet over the The buoy is made up of three basic sub-systems. These buried pipeline. are the turntable, the hull, and the piping (see Figure 12).

Bottom Manifold Turntable. The turntable is a rotating platform on top The primary function of the bottom manifold is to of the buoy which serves a number of functions. It carries provide for the connection of the underbuoy hoses to the the mooring connections and transmits mooring line forces

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Figure 8. Schematic representation of water particle trajectories in Figure 7. Force system on a buried submarine pipeline. ocean waves. 160 to the buoy hull through its bearings or bogey wheels. It of a number of parameters and cannot be established supports the deck piping and valving. It carries a counter- analytically. Instead they are determined from analysis of weight to balance the piping and the mooring fittings. It the results of tests made with scale models. incorporates a small boat fender and access ladder, and provides a safe working platform for maintenance and Mooring Lines. Mooring lines consist of two nylon repair operations. It must be designed with adequate hawsers permanently connected to the buoy and made strength and must rotate freely under all conditions of buoyant with foam plastic flotation beads. Having the loading. mooring lines buoyant avoids the possibility of entangle-

Body or Hull The hull is the basic flotation unit required to support the ground tackle, the underbuoy hose, the buoy piping and the turntable. The hull must be designed to have sufficient reserve buoyancy that it will not

be pulled underwater by the maximum anticipated mooring Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1969/1/157/1737643/2169-3358-1969-1-157.pdf by guest on 29 September 2021 line forces. Further, the hull must be compartmented so that it will remain floating in the event of damage and flooding of any one compartment. The hull must be strong enough to withstand the buffeting of the sea and occasional impacts from flotsam and jetsam or small craft. It must also have sufficient strength to transmit the mooring line forces from the turntable to the ground tackle. The hull is normally designed with a skirt type fender to prevent the floating hose strings from being caught and squeezed between the ship and the buoy hull.

Piping. The piping on the buoy serves to connect the underbuoy hose through a product swivel to the floating hose. Figure 10. Bottom manifold, 42-inch diameter submarine pipeline.

The product swivel is the heart of the entire single buoy mooring system. It must be able to rotate through a full 360 degrees, be leak-free, and move easily. At some installations it is necessary that the swivel handle more than ■^r one product. Multi-product swivels capable of distributing up to five different products have been built. \ / \ Valves should be provided in the piping system between \ the swivel and each of the floating hose strings. This is to permit isolating one or more hoses for maintenance, repair, or damage control. UNDER-BUOY HOSES "3SRS& Mooring Lines and Ground Tackle LAZY "S" OR BOW LEGGED Both permanently attached mooring hawsers and ground tackle are part of the SBM system. Thus, mooring forces are transmitted through a known system to the ocean bottom. The maximum mooring forces are a function Figure 11. Two configurations for hose under a buoy.

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UNDER-BUOY MOORING HOSES CHAIN

Figure 9. Schematic of possible sequential lift, drag and inertial forces exerted by a wave passing over a submarine pipeline. Figure 12. Buoy body and piping. 161 ment with the ground tackle during the periods between a jacket of unicellular foam rubber having an external tankers when the buoy is not in use. Short lengths of chain protective skin. These two systems of providing flotation are used at the ends of the hawsers where there is a danger are illustrated in Figure 15. of chafe on the buoy or on the fair leads of the ship. The high elasticity of the nylon hawsers has at least two The number and diameter of the floating hoses depends advantages. It reduces the effective force of dynamic upon the number of products, the desired throughput and loadings and "snatch" caused by differential movement of the sizes of hose currently manufactured. Throughput for the buoy and the ship. The high elasticity also leads to a any hose is limited by velocity. The manufacturers recom- better equalization of loads in the two mooring lines. mend that the maximum velocity not exceed 40 feet per second. The maximum diameters available are the same as Ground Tackle. The chain and anchorage of the ground those for the underbuoy hose. Diameters of up to 24 inches tackle array must transmit the mooring forces from the are currently in use and 30-inch diameter is said to be buoy to the ocean bottom. The ground tackle array forms a available. For ease of operation the number of floating

spread mooring for the buoy. Arrays having both four and hoses should be kept to a minimum. Whenever possible, it is Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1969/1/157/1737643/2169-3358-1969-1-157.pdf by guest on 29 September 2021 eight legs are in common use. Other arrays are, of course, always better to use one large diameter hose in lieu of two possible. Each leg of the array consists of a chain pendent or more of a smaller diameter. from the buoy to an anchorage at the ocean bottom. A portion of the chain is constantly moving onto and off of Because of the limited capacity of tanker lifting gear the bottom as a result of wave action on the buoy. This and because of the stiffness of large diameter heavy duty "dip section" is often made of heavier chain to compensate cargo hose, 16 inch diameter hose is the largest which for the extra wear that it receives. The chain pendent should should be lifted over the ship's rail for connection to the be designed so that the pull on the anchorage is always manifold. Thus, when a larger diameter floating hose is used parallel to the bottom even under the heaviest anticipated it is necessary to provide 16 inch or smaller diameter tail load condition. A small and equal pretension in each leg of hoses. These tail hoses must be long enough to go from the mooring reduces the excursion of the buoy when it is water level to the ship's manifold under all conditions of not in use to moor a tanker. draft without excessive strain or bending which might cause kinking or other damage to the hose. The length of floating The type of anchorage used depends upon the soils hose is a function of ship size and mooring line length. It encountered at the site. To date, both anchors and stake can be determined by adding up the various elements which piles have been used as illustrated in Figure 13. Anchors, make up the total length between the buoy and the ship's when used, should be jetted into the bottom or otherwise manifold. Each tail hose should be provided with a buried to avoid any possible dragging which would upset butterfly valve and a blind flange at the end. The valve will the balance of the system. Stake pile designs vary. The size reduce the possibility of any spill occurring when connect- and length of the pile depends upon the soils. The chain ing or disconnecting the hose. attachment to the pile must be designed for the repetitive dynamic loading which it must withstand. System Operation

Floating Hose Strings From the preceding discussion of design, it should be The floating hose strings which form the link between apparent that existing technology, although lacking in some the buoy and the tanker (Figure 14) are made up to 25 to areas, is adequate for the design of a safe submarine 35 foot lengths flanged together. This hose is also basically pipeline and single buoy mooring system. However, this is a smooth bore, heavy duty, reinforced cargo hose. The only one side of the coin. The other side is operation of the length of hose that connects to the buoy is sometimes made system. Careful, competent operation is essential to the of a special variable stiffness construction because of the prevention of oil spills. severe flexing at this point. Flotation is provided either externally in the form of float collars or beads constructed Good operating practices will vary somewhat from one of medium density unicellular plastic foam, or integrally, as terminal to the next, depending upon local conditions and

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Figure 13. Ground tackle for buoy mooring. Figure 14. Floating hose string. 162 Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1969/1/157/1737643/2169-3358-1969-1-157.pdf by guest on 29 September 2021

Figure 15. Alternative hose flotation systems. Figure 16. Diagram showing the idealized tanker approach. the operator's preference. What follows is intended as a Connecting the Floating Hoses generalized description of the offshore operation of a Hose handling is normally carried out by the ship's crew submarine pipeline and single buoy mooring system. with some assistance from the mooring launch crew. Connection of the hoses is thus the responsibility of the Mooring the Tanker ship's cargo officer and is carried out with advice and Mooring of the tanker is a ship-handling problem. It is guidance from the mooring master. best performed under the guidance of a pilot or mooring master who is familiar with the area and the particular Preparations. An important part of the preparation is installation. At present, mooring of a tanker to a single establishing a communications link between the ship and buoy mooring requires the assistance of a mooring launch. the shore. Usually the mooring master is in radio communi- This limits the mooring activity to sea conditions with wave cation with the on-shore operating personnel. This permits heights of from 6 to 8 feet, or less. discussion of cargo handüng rates, signals to be used, and emergency procedures. Other preparations include the Preparing to Moor. Preparation for a mooring involves on-board measures taken to prevent spills such as the the carrying out of a large number of tasks. These involve placing of drip pans under the manifolds, plugging of the setting out the mooring gear, preparing the ship's mani- scuppers, and lashing closed all sea valves connected to the folds, and planning an approach to the buoy which is cargo piping. consistent with the existing wind and sea conditions. If there is any chance that the tanker approach will endanger Flanging Up. The floating hose is lifted with the ship's the floating hoses, the mooring launch will be advised to gear, stopped off, and the end lowered to the ship's move the floating hose to one side. manifold. The flange connection to the manifold is made using a suitable gasket to ensure against leakage. For each installation there is a "danger contour" which represents the shoreward boundary of the safe maneuvering Loading of Offloading Cargo area around the buoy. The depth of this contour is a Pumping is not permitted to commence until the ship's function of the tanker draft and the clearance required cargo officer has assured himself that the valves of the cargo under the keel. The buoy is located so that the distance piping system are properly set. As a further precaution, between it and the danger contour is adequate to provide pumping is started at a reduced rate so that connections, for maneuvering the tanker into the berth. Figure 16 shows valving and water around the vessel can be checked. the danger contour and an idealized tanker approach. During cargo transfer, frequent inspections are made of The tanker will make its approach at a minimum speed the mooring tackle, the mooring buoy, the floating hoses, consistent with ability to steer. It should complete its turn and cargo transfer operations aboard ship. In light weather far enough from the buoy to permit adjustment in course there may be a tendency for the tanker to override the and stopping before the buoy is reached. Ideally the ship buoy. This should not be permitted to happen since it should come dead in the water at from 100 to 300 feet could result in damage to the floating hose. Running the from the buoy. The approach should be planned so that, if ship's propeller a few revolutions astern is a method the maneuver does not proceed as expected, the ship can sometimes used to keep the tanker in it proper position. If pass the buoy on the side opposite to the hoses and make a weather deteriorates and seas become rough it may be second approach. necessary to disconnect the floating hoses from the ship's manifold to avoid damage to them. However, it is seldom Running the Lines. When the tanker is close enough to that weather and sea conditions will force a tanker to leave the buoy, and virtually stopped in the water, the mooring the mooring. launch affixes messenger lines from the ship to each of the mooring hawser pendents. The mooring hawsers are then When taking on cargo, the "topping off" operation is hauled aboard and made fast to complete the mooring. critical from the standpoint of spill prevention. It requires experienced supervision and is usually carried out at a Areas requiring critical attention are: reduced loading rate. 1. Design of the submarine pipeline for adequate Disconnecting the Floating Hoses strength and durability under the most severe Disconnection normally follows completion of cargo anticipated environmental conditions. transfer but it may also be necessary to temporarily 2. Design of the buoy and mooring to withstand the disconnect because of adverse weather and sea conditions, forces imposed by the moored tanker. These forces or to rapidly disconnect because of an emergency resulting should represent the most severe weather and sea from unforeseen events. conditions for which the tanker might be expected to remain at the mooring. If emergency quick-disconnects are provided, they 3. Continuous and careful maintenance of the entire should be placed between the hose end valve and the ship's system with particular attention to the buoy swivel, manifold. Then, if an emergency dictates that the tanker and the floating hose strings.

depart without delay, the hose end valve can be closed to 4. Competent supervision of all operations having to Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1969/1/157/1737643/2169-3358-1969-1-157.pdf by guest on 29 September 2021 prevent serious spill. do with cargo transfer. This includes connection and disconnection of the floating hoses, operation of all Disconnection does not begin until all of the ship and cargo system valving, control of pumping rates, and shore valves have been closed and the ends of the hoses other shipboard precautions. have been cleared of oil. Clearing can sometimes be accomplished by venting. A more positive method is to pull It would not be realistic to say that accidents will not a slight suction on the system using a small onshore happen. Emergency procedures must be worked out, and evacuation pump. equipment must be ready to handle accidental spills in the event that they do occur. However, experience with As soon as hoses are disconnected, the ends are blanked existing installations has demonstrated that the probability off with a blind flange. The hoses are then lowered into the of a spill can be kept very low through proper design and water with the ship's gear and towed away from the ship by operation of the submarine pipeline and single buoy the mooring launch. mooring system.

Leaving the Mooring References After the hoses have been towed out of the way, the mooring hawsers are cast off and the ship is free to depart. 1. Dr. Randolph Blumberg, "Hurricane Winds, Waves and Currents Test Marine Pipe Line Design," Pipe Line Industry, June-Nov. The departure maneuver will depend upon the site, weather (1964). conditions, and sea conditions. The maneuver must be planned so that the ship passes the buoy at a safe distance 2. Joe L. Kreig, "Good Engineering Practice Best Protection For on the side away from the floating hoses. Offshore Lines," Pipe Line Industry, 18 (3) 43-49 (1963). 3. Submarine Pipeline Design Manual, Bechtel Corporation, San Conclusion Francisco. The significant elements of design and operation of a submarine pipeline and single buoy mooring system have 4. R. E. Haring & R. A. Beazley, "Design of Single-Point Mooring Systems for the Open Ocean," Offshore Technology Con- been presented with the intent of giving the reader a better ference, OTC 1022, (1969). understanding of the problems, advantages, and disadvan- tages of the system. It must be borne in mind, however, 5. Minutes of the S.P.M. Forum, (1965-66). that both design and operation depend upon the site selected for the installation. 6. J. M. Langeveld, et al, XXIInd International Navigation Con- gress, Section II, Subject 3, 117-144, Permanent International Association of Navigation Congress, Brussels, Belgium (1969). Some points which should be emphasized are: 7. E. H. Harlow & S. W. Small, "Problems Arising From The Use of 1. Very large tankers are an economic and physical fact Very Large Ships in Connection With Structures For Loading and the need for adequate facilities to service these And Discharging Offshore," XXIInd International Navigation Congress, Section II, Subject 3, 179-190, Permanent Inter- very large vessels must be recognized and satisfied. national Assocation of Navigation Congress, Brussels, Belgium 2. Sheltered deep water ports capable of handling these (1969). very large tankers are few in number. 3. Provision of sheltered facilities is not feasible for 8. Harry G. Knechtel, "Crude Transfer Hose System for Offshore Terminals," Proceedings of OECON, 397-426, Offshore Explora- either economic or physical reasons in many parts of tion Conference, Palos Verdes Estates, California (1968). the world. This is particularly true in many of the areas where oil is currently produced, and at a 9. U. S. Coast Guard, A Manual For The Safe Handling Of number of crude oil processing centers in the United Inflammable and Combustible Liquids, CG-174, United States States, Europe and elsewhere. Government Printing Office, Washington D. C. (1964). 4. A submarine pipeline and single buoy mooring 10. American Petroleum Institute, Manual For the Prevention of system is a safe and economical to the Water Pollution During Marine Oil Terminal Transfer Opera- problem of servicing very large tankers. It is the tions, API Division of Transportation, (1964). solution that has been most used to date. 11. U. S. Department of Interior & U.S.Department of Transporta- 5. Careful and competent design and operation are tion, A Report on Pollution of the Nation's Waters by Oil and essential to the continued success of the submarine Other Hazardous Substances, U. S. Government Printing Office, pipeline and single buoy mooring system. Washington D.C. (1968).

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