ARCHEF
Lab.
y. Scheepsbouwkinde
Technische HogschooI
Dell t
An Outline of Our Research Organization
on Ocean Engineering Techniques
May 1977
MITSUBISHI HEAVY INDUSTRIES, LTD.
on Ocean Engineering Techniques
1. Introduction
The techniques relating to ocean engineering can be
roughly divided into offshore technology and oceanography
at the present stage. The former is the direct technology
used for the design, fabrication and construction of various kinds of structures, equipment and instruments required for the effective use of the potentials of the
ocean as represented by resources, energy and space. The latter is the technology for the scientific research of the phenomena and environment of the ocean itself. It forms the basis of the development of the former, but on the other hand, gets the benefit of the structures, equipment and instruments created by the former.
However, there are many cases in which similar themes
are discussed in the points of contact of both of them from their respective standpoints and it is
difficult to
define their boundary distinctly. This tendency is
par-ticularly remarkable in environment assessment. For in-stance, though the Offshore Technology Conference held in Houston, Texas of the United States of America in
May every year is a good example epresenting the former, the papers presented to this conference include those relating to the problems of the treatment of environ-mental pollutions1 besides those concerning the analysis of wind and waves. Further, at the International Conference
on Port and Ocean Engineering under Arctic Conditions held every three years, 20 per cent of the papers are occupied by those dealing with the problems of
environ-ment assessenviron-ment of ice-covered or drift-ice-covered water areas besides those concerning ice and drift-ice.2
On the other hand, in the papers presented to the autumnal meeting of 1975 of the Japan Oceanographic Society which is considered to represent the latter, there were those handling the problems concerning the discus-sion on wave force acting on submerged structures3'4
besides those concerning the discussion on the observation
and analytical methods of oceanic environmental pollu-tion and the discussion on the possibility of environment monitoring by remote control.
The ocean development techniques of our company
are preponderantly oriented to both the software and hardware mainly relating to the offshore technology, mak-ing full use of the features of our company as a heavy
industrial company.
The utility value of the ocean has remarkably expanded
* Shipbuilding & Steel Structures Headquarters
Masaki Tamehiro * Yukio Sakae
Hitoshi Fujil ** Susumu Teramoto
as compared with that of the age when the ocean was considered as the means of marine transportation or the place containing fishery and industrial resources. Among the potentials of the ocean, the use of its resources is most expected on the global scale and its realization is
making a steady progress. As regards the use of its space,
various kinds of projects are being developed as effective means to secure the location of industries matched with new urban structures, to improve living environment on lands and to store resources. However, these projects
still involve many technical problems requiring solution. In some foreign countries, the full-scale use of energy has already been realized in such fields as wave, tidal current and sea-thermal power generation. In our country
also, basic research on the use of the Pacific current aimed
at getting energy resources5, and practical application
of small-scale wave power generation are being
under-taken. However, these are still in their infancy.
Taking such circumstances into consideration, our
com-pany is conducting technical development and furnishing
research facilities based on long-term schedules. Besides,
we are keeping up efforts to create good hardwares by getting significant data from oceanography and trying to
reconcile oceanography and offshore technology.
2. Review of Environment Requiring Ocean Development
Techniques
2.1 Use of resources
It may be said to be the matter of common knowledge
that a large concern on ocean resources is now concentrated
on offshore oil resources and manganese nodules rather
than the fisheries and inorganic resource which have been utilized since long ago.
Offshore oil field exploration activities are now expand-ing on the global scale from the neighborexpand-ing water areas
around the continental shelves to deep, rough or ice-covered
water areas year after year. To cope with this situation, a rapid technical development s looked forward to and the compatibility of technical development and economy becomes one of the main subjects to study for the circles
concerned. Japan, though surrounded by seas, is entirely pessimistic as to oil resources at present. Because even
though the Ocean Prospector, Hakuryu II and Hakuryu Ill were built in Japan prospecting offshore oil exploration projects around the periphery of the Japan Archipelago
MTB 121 May 1977
and South East Asia, they could not discover a bonanza field such as seen in the North Sea. On the other hand the water areas which were found promising for under
sea oil geologically are located close to the territorial
waters of the adjacent countries or overlap rich fishing
rounds, and it is impossible to conduct exploration
ac-tivities as much as they desire. I n addition, the geophysical exploration of the water areas deeper than the continental
shelves around the Japanese archipelago is just at the first stage and we are in an instable situation to create an atmosphere to promote technical development for the future offshore oil exploration.
However, the general trend of the world is that the Ship Classification Society of each country has started
brisk activities, from the viewpoint of securing safety
against severe environmental conditions of the ocean, to integrate the structural calculation technique and to inter-nationalize safety devices for offshore drilling units which
play a leading role in exploration activities, and it is
the time for the designers and manufacturers of such units to express their views on the basis of the results of their technical development. To cope with such severe conditions, mooring technique for floating structures, the
improvement of their structural shapes and the
reexamina-tion of their materials are becoming the subjects of study. Furthermore, as a basic subject, the establishment of an accurate estimation method of wave load applicable to
various structures and the establishment of a fatigue design method are strongly desired.
As regards the exploitation of offshore oil field, produc-tion in deep water areas has again got into the spotlight with the recent discovery of a commerical-quantity oil
field in the 936 ft (285 m)-deep water area facing the estuary of the River Mississippi in the Gulf of Mexico. Various exploitation units including the jacket type, spar
type and submarine exploitation system have been
schem-ed for operation in water areas with a depth range of 550 ft to 950 ft in the North Sea, off Santa Barbara and the Gulf of Mexico and much effort has been made for these units as the objects of development. On the other hand, production platforms of concrete structure have come to be adopted actively because of low
manufac-turing and maintenance costs and less manpower required.
Thirteen out of 39 platforms installed or under construc-tion in the North Sea are fabricated with concrete.
Exploitation activity in drift ice water areas throughout
the year is also dIscussed enthusiastically in the countries
in the northern sphere as the future trend of technical
development.
The diversification of the structures and materials to cope with the environment as mentioned above is clearly shown in the Design Appraisal/Analysis activities of the Lloyd's Register of Shipping. For Japan, and earthquake
countries, the establishment of an analytical method intro-ducing a dynamic design method which takes the
dis-placement of the ground by seismic motions into
consideration is desired. What is important for large
structures such as the platforms is the method of con-struction, whether they are built with steel or concrete. Particularly, in our country which has no fiord coast such as that in Norway, it is difficult to build concrete
plat-forms in water areas with a depth of i 50 meters.
lt
is well known that many enterprises of the worldhave organized several consortium groups and are
conduct-Ing research in the fields of prospecting, mining, lifting
and transportation of manganese nodules. The completion
of the exploitation system and their activities may give a great effect on the future trend of the Law of the Sea.
2.2 Use of space
The space of the sea can be used as a plane surface or three-dimensionally. The plane of the sea has been used as a means of traffic and transportation since long ago, Recently, attempts to develop cities toward offshore in normal direction to the coastal line and attempts to build facilities requiring a wide area such as oil storage system, various kinds of chemical plants, power plant, airport and special harbor facilities on the sea in order to avoid noise and offensive odor which give bad effects on social environment or to make up for the shortage of industrial sites on land are being made as methods of utilizing the plane of the sea.
However, to realize these attempts successfully,. there are many problems requiring solution in connection vith the composition of the system, such as the types of floating structures, the position keeping, the preservation of the environment and control regulations, and it is
considered that it will still take a long time before their realization. We are certain, however, that the floating city "Aquapolis" constructed in 1975 by our company for
Japanese Government and exhibited at the International Ocean Exposition has made a great contribution to the
progress of ocean engineering techniques.
The extensive space of the sea is also particularly attractive as storage places of materials. Storage barges of crude oil, LPG and ores have already been realized in Japan and other countries and the water areas on which they are installed are gradually expanding from enclosed bays to open water areas. To cope with this situation,
interesting studies are being made on their structures,
types, materials and mooring technique. As storage space,
floating storage tanks have been generally adopted. It is
worthy of note, however, that sit-on-bottom type offshore
structures such as submersible platform are adopted in place Df floating offshore structures6 in consideration of the effect of acceleration on the internal equipment and residents and cyclic load applied to the single point mooring equipment which are incidental to the oscillation at sea. Concerning the relation between scouring at the
bottom and the soil, satisfactory solutions have not yet made for all the conceivable structural shapes, for which we must depend on future research and development.
made in the material used for the construction of struc-turai bodies. The concrete-màde LPG storage tank built
in the graving dock of Concrete Technology Corp. of
USA and towed to and installed in Indonesia is its typical example. This tank was initially planned to be built with
steel. However, concrete was adopted for the convenience
of building berth and others. In order to cover the weak-ness of concrete against tension, the largest weak point of concrete, a special shape with the barge bottom con-stituting part of the cylindrical surface was adopted to
reduce the tensile stress zone besides using the prestressed
concrete. The problem of concrete is under study in
Japan by the Japan Ship's Machinery Development
As-sociation and the Rules have been published by Nippon Kaiji Kyokai. Under such circumstances, ¡t is expected
that the movement for the realization of concrete struc-tures will become stronger at a rapid pace.
As for the plant barge, considerably intensive studies have been made since a long time ago. The offshore nuclear power plant to be constructed off Atlantic City in the United States is an example of plant barge. As a
recent case, a concept of an offshore power plant planned to be constructed near the Oafu Island of Hawaii of
USA was published at the POAC 75.
Generally, the most important matter in the construc-tion of an offshore plant is to arrange the plant, which
is proven on land, as compactly as possible and to secure
its stability in waves so as to reduce the oscillating effect of the waves on important components such as the com-pressor to the smallest possible. For this purpose, it is a general practice to use an enclosed sea surface. However,
it is desired that semi-submersible platforms and offshore
plant barges with anti-oscillation devices to be used in open sea surfaces be realized in the future. In this case, the mooring system is a matter of great concern with
the type of the plant barge. Concerning the heaving of the semi-submersible platforms used for oil drilling, the effect of the mooring wire rope could be disregarded to a certain extent from the viewpoint of calculation
tech-nique. For such large-type plant barges, however, the
effect of the mooring wire rope cannot be disregarded
for all oscillations and the establishment of mooring calcu-lation technique is desired.
The concept of the use of space as mentioned above is gradually giving rise to cries for its harmony with the environment. This is stimulating the demand for dredgers, offshore remote supply bases and fire-fighting boats and is creating new markets for semi-submersible platforms and catamarans. Some circles are taking up this concept
system-Wise and as its result, the development of various
kinds of equipment such as oil skimmer, oil separator,
oil fence, collision protection bank and breakwater is
promoted. However, above mentioned various kinds of present equipment are low in useful limits to external forces such as wind and tidal current, and development of the functions capable of coping with the expansion of
operating conditions is desired.
The three-dimensional use of the ocean space is not so active at the present stage. Preference is given to the
efforts to know the sea itself three-dimensionally rather than to the efforts to use it. Under such circumstances,
underwater survey apparatuses, communication systems, wave observation buoys, deep-sea researches submersible
for promoting the progress of oceanography are taken up
as the objects of development.
In this field, however, apart from the submarine, float-ing microwave stations, and sight-seefloat-ing facilities are al-ready in use in comparatively shallow sea areas of up to
around i 00 meters in Japan. I n deep seas also, research
submersibles are already in operation. In some countries,
research submersibles haie been put to practical use since
long ago as an influential means of obtaining basic data on the three-dimensional use of the sea. In our country,
diversified studies are being conducted under the guidance
of the Japan Marine Science & Technology Center. As for
the submersibles, it is considered, as seen
in the "A
Look at Offshore Structures" of Bureau Veritas9, that
it is high time for preponderant orientation to technical development, adding the general safety to the
conven-tional techniques.
As one type of the three-dimensional use of the space, the effective use of the sea bottom is also under study.
The recent progress of the finite element method has made
it possible to analyze the behavior of the structures at the sea bottom at the time of earthquake comparatively in detail, and the analytical results are bringing about a
rapid progress in the sea bottom utilization technique along with the results of experiment of scouring phe-nomenon in a model basin. Sea bottom oil storage tanks and underwater tunnels can be mentioned as typical ex-amples. The former is not yet realized in our country. The future subject is the development of a structure free from oil leakage. If various kinds of equipment related
to sub-systems such as oil-preventing, skimming and large-capacity oil separating techniques for leaked oil, which
is an object of environment assessment, are completed,
the figure of the sea bottom oil storage tanks in Japan
will be actually realized. As for oil separators, in particular,
small-capacity ones (500 m3/h) are under development of a certain extent'°. However, the development of
large-capacity ones is not yet started.
lt
is learned that the oil storage facilities in the North Sea are designed to be allowed for oil spillage up to 50 ppm. Such a value is never allowable in the Japanese waters. If a large-capacity oil separator could be developed,the concept of bottomless tank, treatment of residual
oil ¡n floating hoses between tankers and single point
mooring buoy, and emergency disposal of leaked oil should
find an immediate solution.
As an example of the use of the sea bottom, we can mention the caisson in the lower part of the main tower of the suspension bridge to be built between Japanese
MTB 121 May 1977
main land and Shikoku island. The Akashi-Naruto route has to be located in a tidal current of 8 kn and high-level technique is necessary to sink caissons from above the sea surface into the scheduled points at the sea bottom.
For this purpose, various technical studies including water tank tests are being conducted under the guidance of the Honshu Shikoku Bridge Authority. The results of the
studies are to be adopted in the bride construction works to be started in the near future. According to the present concept, sinking of the caissons will be carried
out while flow velocity does not exceed about 2 kn
during one tidal current period, and the technique to maintain work barges at constant positions is a key point
for the successful sinking of the caissons.
The development of various kinds of civil engineering
machinery used for improving the sludgy ground and levelling the rubble-mound at the sea bottom is desired. The development of a new system taking into considera-tion the economy, raconsidera-tionality and safety of the technique to remote-control such machinery from above the sea surface and the economic realization of the maintenance
of various kinds of work barges at constant positions in
tidal current zones exceeding 3 kn are the subjects of future study.
2.3 Use of energy
Temperature difference, salinity difference, waves, ebb
and tide and tidal current are investigated with a hope to extract clean energy. Japan has already realized a small-scale wave force power generating system but has no
other facilities. tn the Japanese waters, there are tidal current exceeding 6 kn as in the Straints of Tsugaru and
Akashi. It is difficult, however, to fix a platform on
which a power plant ¡s installed in a tidal current having such a quick flow velocity. On the other hand, the flow velocity of the Pacific current, Kuroshio, is about 2 kn -5 kn, being comparatively close to the steady flow and it may be an object for energy extraction though its head
¡s low.
lt was reporred' that electric energy correspond with
2 nuclear power plants of i million kW class can be
extracted by use of 4 percent of the Florida current
which flows along the eastern side of the Florida Penin-sula. A generating sytem utilizing low head is also under study by some circles'2.
In Japan, however, some difficulties will be conceivable,
because the stability of the vector of that warm current is disturbed seasonally by the cold current and besides, there is the mixed existence of the energy sources with fishing grounds and suitable areas for oil resources
ex-ploitation. Therefore, it is considered that long-term investigation and environmental adjustment under a close
cooperation with the personnel engaged in oceanography are essential for the accomplishment of energy extraction
technique.
Transportation of extracted energy to land is also
considered as a big problem. Suppose a nuclear generating plant is constructed offshore. The transmission of large-voltage current for this case has been proposed since long ago as a problem requiring solution. To cope with this problem, the use of the extracted energy for the
dissolution of sea water into other forms such as hydrogen
is taken up as a future problem.
On the other hand, it is said that there is a possibility of study on the direct use of the energy just at the site where that is extracted for the aluminium smelting plant which may consume a big quantity of electric power.
If the energy of the sea could be tanken out economically,
its effects are supposed to be immeasurably large. As the matter stands now, however, the technique has just got
under way.
In the above, we have made a general description of
the use of the potentials of the sea and problems involved.
From a short-term viewpoint,
it can be said thai the
problems of the use of the resources are most eagerly awaiting the results of technical development. From a long-term viewpoint, however, it is needless to say that
we must make a steady development of the usage of space and energy of the sea for the next age. For these technical developments, however, the cooperations of a great many people and constant studies by trial and error are indispensable. Our company perceived the necessity of the cultivation of ocean engineering technique at the beginning of 1963 and since repeated experimental tank tests on the single buoy mooring for the tanker and on the tension leg platform. Our research activities became full-fledged with the progress of offshore oil field
develop-ment and we have succeeded in developing various kinds
of offshore oil drilling units by our own efforts.
In our visit to the office of American Bureau of Ship-ping in New Orleans previously, we had an opportunity to talk with Mr. Bouchard, chief inspector, about the Ocean Prospector and the Ocean Kokuei built by our company and delivered to Ocean Drilling & Exploration Company. In this interview, he said feelingly "You have received many lessons from these units". Actually, drilling units of the same type were also built by the Avondale Shipyard in the United States, the Aker Group of Norway, and the Transfield Shipyard in Australia. In the construc-tion of these units from design to fabrication, muny
technical problems arose successibly and all the designers
and field engineers exerted themselves for finding out good solutions. These efforts made a great contribution
to the progress of the techniques on offshore drilling units.
The lessons we got from the two drilling units were completely embodied in the Hakuryu II, and the Hakuryu III. On the other hand, the Aker Group built the Aker H-3 after thorough study with Det Norske Ventas. Later, American Bureau of Shipping published a pape»3 on the lamellar tearing of steel plate and its countermeasures.
The anti-lamellar tearing steel plate manufactured by the Nippon Steel Corporation is the fruit of the joint
develop-ment of the Corporation and the design and research departments of our company. The Z-steel produced by the Scandinavia Plate Co. of Sweden is also the result of the joint development of the Aker Group and Det
Norske Ventas.
The progress of the ocean engineering technique could
not be attained without the positive activities of the
research institutes concerned from the start. At the time when "ocean engineering" became widely known on a full scale, the Classification Societies had no suitable regulations and there were no sufficient theoretical
back-ground justifying ocean engineering. Only the theory and analytical results published by our research institutes formed the basis of our activities. With the increasing
activities of each Classification Society later on, our
dissatisfaction was gradually eased. However, only the basic problems have been solved up to the present time, and it is desired that research activities will be continued for the solution of various problems including those pointed out by the author.
3. Outline of Research Institutes of our Company and
their Activities Related to Ocean E ngineering Tech niques
Development of the ocean engineering techniques in our company has been conducted in our Nagasaki, Hiroshima and Takasago Technical Institutes in accordance
with the field of study. The Nagasaki Technical Institute is equipped with a large-size ship experimental tank used for research of seakeeping and maneuvering qualities of ships, the Hiroshima Technical Institute has a test tank
for research of offshore structure performance and' the Takasago Technical Institute is provided with a large-size
pressure test apparatus, and all these unique facilities are used effectively. For instance, so-called "Aquapolis" known as the first man-made floating city put on display
at the International Ocean Exposition 1975 by the Japanese
Government had been developed jointly on the basis of
structural test conducted in the Hiroshima Technical Institute and of its hydrodynamic resistance and
oscilla-tion tests in waves and wind resistance tests in the Nagasaki
Technical Institute.
The survey of the technical needs for coping with the ocean environment as reviewed in foregoing article 2 are made jointly by the Shipbuilding and Steel Structure
Division, the Engineering System Development Depart-ments or the Technical Institutes concerned, and the
preparations of research programs are made. Each technical department concerned thoroughly discusses the programs
until their final forms are reached under control of the
Technical Headquarters.
The following is a brief description of the research
facilities of our above-mentioned Technical Institutes and how they are utilized in our actual ocean engineering
activities.
3.1 Nagasaki Technical Institute
The Nagasaki Technical Institute is our main
tech-nical institute for the studies of ships and prime movers,
and is accordingly equipped with lange-size testing
equip-ment suitable for ocean engineering as well. Its research facilities relating to ocean engineering techniques are as
follows.
3.1 .1 Research facilities
3.1.1.1 Ship experimental tank
As research facilities for ship forms, there are Towing tank and Seakeeping and Maneuvering Basin. These ex-perimental tanks are mainly used for hydrodynamic
re-search of ships. The experience and the results of rere-search
obtained are fully used for the development and research of marine structures. The principal particulars of the tank are shown in Table i.
The towing tank was built in 1907 and this was the first towing tank ever built in Japan. The development
of the ship forms of various kinds of highly efficient
merchant ships and of naval vessels have since been carried out.
The facilities were completely destroyed by atomic bomb at the end of World War Il, but was reconstructed
after the War. At present, 2 towing tanks, which
oc-casionally can be used as a 285 m-long tank, are used for
a wide variety of research from the basic hydrodynamical research to the development of ship form and propeller of various kinds. Particularly, the results of studies on the correlation of characteristics between model and full
scale ships and the accuracy of the evaluation of the
performance of full scale ships are highly estimated in the world and this may be an especial characteristic of the institute of an enterprise. With the increase of
self-propelled offshore structures in recent years, these testing
tanks have come to be used for the tests of such struc-tures, making various contributions in this newer field. The Seakeeping and Maneuvering Basin (Fig. 1) was constructed in 1972 and has since been in constant
opera-tion. One object of this Basin is to evaluate the wave
load acting on the hull with high accuracy; and thus, the
Basin is capable of producing regular and irregular waves.
Efficient experimental studies on the motions and the wave loads of various kinds of marine structure in waves such as offshore oil drilling units can be conducted with ease in this Basin. The results of model tests are offering useful and reliable data for the basic design of marine structures of various kind.
3.1.1.2 Multi-purpose wind tunnel
The multi-purpose wind tunnel was built in 1973 and has since been in service. With an air outlet of measuring section 10m x 3m in size, this wind tunnel is capable
of attaining the maximum wind velocity of 28 m/s. Its feature is that the air outlet is capable of rotating 900 around the axis of the wind tunnel. For long structures
such as suspension bridges, it can use a large-size scale model within the length of the measuring section of 10m, and therefore, it can be used for the tests such as a detailed investigation of stability against wind in the stage
MTB 121 May 1977 Length Breadth Depth Maximum speed Drive motors Speed control Standard length Maximum length Wave length Wave height Drive motor Resistance test Self-propulsion tes Propeller open-wat Wake survey Measurement in Wa Wave pattern meas Size Towing carr jage Ship model Wave maker Kinds of test Towing tank
Table 1 The principal particulars of ship experimental tank
Large tank Small tank
165m 120m
12.5 m 6.1 m 6.5 m 3.65 m 10 m/s 4.5 rn/s
75kWx4
l5kWx4
Digital control by thyristor
static leonard system
er test ves 7m 4.2m 10m 7m
1 10m
0.4 m 22 kWurement for wave analysis
1 - 10m
0.2 m 4 kW
of erection. For large height structures such as chimneys and steel towers, it can be used for high-accuracy wind-proof test by setting the measuring section of 10m in vertical position, enabling thorough investigation of safety
measures to be carried out.
With its universality, this wind tunnel is used for the study on the wind resistance of ships and offshore struc-tures and wind pressure moment as well as for the study of the stability against wind of various kinds of steel
structures such as suspension bridges, chimneys and
large-size cooling towers, offering useful data to the design
departments.
3.1.1.3 Ship strength testing facilities
The establishment of the procedures for estimating
external forces, strength response and structural safety
s
Fig. i Seakeeping and maneuvering basin
Digital control by thy
Maximum speed Drive motors Speed control
Kinds of test
Seakeeping and maneuvering basin
Seakeeping tests Resistance and self-propulsion test in regular and irregular
waves of arbitrary direction Measurement of wave loads Forced oscillation t est u
ristor leonard system
Maneuvering tests Zig zag test
Turning and spiral
test
Large amplitude forced yawing test
has become increasingly important for making reasonable
structural design of ships and offshore structures which have been growing in size and diversified in type year
after year.
The fatigue strength testing facilities comprising a 100-ton universal fatigue testing machine, a 100-100-ton corrosion fatigue testing machine and a 250-ton structure fatigue testing machine are installed in the Ship Strength Experi-ment Laboratory (Fig. 2) and are used for the study
Fig. 2 General view of ship strength testing facilities
Shorter side wave maker
Longer side wave maker
Breadthofflap lOmx3
lOmxl2
IlVave length 0.5-10 rn 0.5-10 m Jave height 0.4 m 0.3 m
Power
l5OkVAxl
l2OkVAx4 X-Carnage V-Carriage Seakeeping basin Maneuvering basin60m 180 rn Length 60 m 30m Breadth Depth 3.5 2m 22kW X 4 2 kW x 2 3 rn/s 2 rn/s
Fig. 3 Coating and sea water testing facilities (Ballast tank corrosion testing device)
Table 2 Basic specifications of the impact water
pressure testing tower
Dimensions of models
Drop weight Impact velocity
Drop height
Max. 2000 x 2000 mm Adjustable between 7 .- lOt
Max. 10 rn/s Max. 5.1 m
aimed at comprehensive safety judgement of structural safety from the view-point of fatigue strength. The brittle fracture testing machine (1,000-ton) is used for the study iñtended for the establishment of the measures to guarantee the safety of welded joints. The buckling collapsing testing
device is efficiently used for the establishment of reason-able design method for structural safety, obtaining many
good results.
The impact water pressure testing tower for studying the phenomenon of impact caused by the wave water
surface has a capacity as shown in Table 2.
lt
is inpractical use for the test of bow-flare impact and slamming
of full
ship, by which the response and the condition of fracture of a bow and bottom structure are beingmade clear.
3.1.1.4 Coating and sea water testing facilities
The Nagasaki Technical Institute has a long history in the study of marine paints and coating and corrosion by sea water. In 1971, the Institute made an intensive expansion of research facilities on coating and corrosion by sea water at a convenient site on external coast of
Nagasaki port (Fukahori-Koyagi Branch of Nagasaki
Tech-nical Institute), where active research is being conducted.
(Fig. 3)
For the study of coating, there are a thermo-hygrostate,
a salt water spray testing device and an airless sprayer.
For the study of corrosion by sea water, we have also a low-cycle stress corrosion testing device (manufactured as a part of a research project of the Shipbuilding Re-search Association of Japan) and electrolytic cells. For the study of the durability and anti-fouling property of
Fig. 4 Resistance test of semi-submersible oil drilling rig
(lower hull) (Towing tank)
the coated film, experimental rafts for sea water are floated on the water of Nagasaki outer part basin.
Here, studies on the improvement of paints and coating,
the corrosion of the inner structural members of ships, the corrosion of the parts of marine auxiliary machinery
contacting sea water are intensely made in order to reduce
the cost for painting in the production process, to improve ship's running performance and structural safety and to prevent sea water pollution. The results of these studies are widely in practical use.
Thus, the testing facilities in the Nagasaki Technical Institute installed in primary view of the studies on ship-building techniques are being effectively utilized for the development of marine structures of various design.
3.1.2 Brief description of the results of studies For most of the investigations, research and tests on the hydrodynamic performance of marine structure, the Towing tank, Seakeeping and Maneuvering Basin and Multi-purpose Wind Tunnel described in 3.1.1 have been used and the results obtained were widely adopted in the design of the marine structures built in our building yards, making direct and indirect data contributions to the National projects or marine science and industry. The results are briefly described below.
3.1.2.1 Study on propulsive performance There are wide variety of design of the offshore oil drilling units; however, the one for semi-submersible type has a unique of remarkable reduction of motion in waves. Therefore, the majbr part of the total number of the rigs ever built for deeper sea operation has been the
semi-submersible type. In recent years, importance has also
been increasingly recognized of the design of
self-propel-ling device for the marine structure, such as nozzle propeller
systems. At the towing tanks, studies have been made
on the lower hull
shape, planning the hull lines and optimum propulsion system, based on the long experienceof the studies on ship forms and propeller system. Full-scale propulsion systems built on those basis have been
tested in the full-scale performance trials and the accuracy
MTB 121 May 1977
accuracy resistance and propulsion tests on an isolated lower hull of a 2-lower hull type semi-submersible oíl drilling rig built by our company, using a large-size model. In accordance with the expansion of exploitation area on the sea, the automatic position holding system has become of interest for drilling rigs or drill ships. For these systems, the closed loop control techniques
develop-ed in connection with our automatic navigation system
of ships04 and the results of experiment on hulls and propellers have been applied, and the development study of the dynamic positioning system of the 2-lower hull
type semi-submersible platform have been
conduct-ed'5'06
as our study under the subsidy of the Japan Society for the Promotion of Machine Industry.This study clarified various points of requirements for the dynamic position control systems to be designed as a full-scale systems and also gave us a lot of data con-cerning the capacity of the thruster required, and its
self-propelling abilities.
3.1.2.2 Study on seakeeping qualities
At various kinds of marine structures including oil drilling rigs, it is essential to furnish them sufficient
structural strength in the waves and allowable motion
characteristics in waves for highly efficient operations.
Many experimental studies have been conducted for sea-keeping qualities at Seasea-keeping and Maneuvering Basin; the estimation of the hydrodynamic force acting on struc-tural members and the assessment of their working ef-ficiency on the basis of the performance test results of
ships in waves.
Concerning the estimation of the oscillation
perform-ance of the semi-submersible rigs in waves, the Technical
Institute established an estimation procedure as one of the earliest in this field and put them to practical use'7. The Institute has also studied the estimation of mooring
forces during operation and their safety in storm, and obtained many results significantly useful for the basic design of full-scale systems. They also completed an
ex-tensive structural design procedure for the basic design of
semi-submersible structure on the basis of the computer
program for the estimation of oscillations in waves, putting
it to practical use by verifying its accuracy by tank test
and full-scale performance trial results.
Fig. 5 Oscillation test of semi-submersible oil drilling rig in waves
The large-size semi-submersible rigs built by our com-pany including Ocean Prospector, the Hakuryu Ii and
Hakuryu Ill and the floating city 'Aquapolis", mentioned in the foregoing section, had all undergone basic model
tests for their oscillations, mooring forces and extreme behaviors in storm, and possible confirmations have been thoroughly carried out.
Fig. 5 shows the oscillation test of a semi-submersible
deep-sea oil drilling rig in waves as being carried out as
the joint project study of the Japan Ships Machinery Development Association. This test is conducted under various conditions by use of wave-maker installed on 2 adjacent sides of the Seakeeping and Maneuvering Basin
and its XY movable towing carriage. Full-scale design had
been made on the basis of the results of this test. The Institute is intensely making a basic study on the correla-tion between full-scale and model characteristics based on the full-scale performance test results and their
cor-responding model test results.
3.1.2.3 Study on wind load
In the Multi-purpose Wind Tunnel, model test of the
"Aquapolis" which played symbolic role in the International
Ocean Exposition '75 was conducted as an earliest test after the completion of the Tunnel. In this model test,
a 1/50 model of the Aquapolis was used and measurements
were made for wind resistance, moment, dynamic lift and wind pressure by an air-exposed structure modeIfor various wind directions and positions on the basis of our
long-experienced techniques on wind tunnel tests.
Fig. 6 shows the Aquapolis model put on a water surface-simulated plate with the air outlet at the sideways position. The results obtained by this wind tunnel test
had been used for the detailed investigations of the stability
of the Aquapolis in storm together with the results of various kinds of tests conducted in Seakeeping and
Ma-Fig. 6 Model of "Aquapolis" set on measuring section
(Seen in the rear is the air outlet of the wind tunnel,
Seismic shaking table
Universal fatigue testing machine
Underwater automatic welding experimental facility
Automatic temperature control cooling tank Electronic measurement control type
universal testing machine
Locking type weld crack testing machine
neuvering Basin. All these results have been ref)ected on our design and construction of the offshore structure of
world's largest sca)e.
The Nagasaki Technica) Institute is applying the resu)ts of their hydrodynamic and structural studies on ships and other structures to the development and research of marine structures and the experimental facilities in the
Institute are being effectively used, making much
contribu-tions to the marine industry. 3.2 Hiroshima Technical Institute
The research and development on ocean engineering technique in our Hiroshima Technical Institute is pushed
forward by the research laboratories on material, strength, welding, material forming, structures, chemistry, oscillation
control, computer application, environment equipment and offshore facilities in a body. The principal particulars of their research facilities are shown in Table 3.
3.2.1 Research facilities
3.2.1.1 Offshore structure experimental tank
The feature of this tank is that
it has a sandy or clayish soil tank at the bottom. Further, n addition to the wave-making facility, it is so designed that water in it can be flown circularly by means of a recirculatingTable 3 Principal particulars of research facilities
Electro-hydraulic servo system
Loading capacity: ±20 t Stroke ±50 mm Repetition velocity: O - 25 Hz
Electra-hydraulic servo system
Loading capacity: 20 tg Stroke ±120mm Repetition velocity: O - 50 Hz Tank: Welder: Temperature range: Internal capacity: 1-4.5 mx W 4.2 m xH 4.1 m
Flat, vertical, horizontal underwater automatic welder, adopting
MIG, CO2 and CHO welding processes, with underwater TV camera
Atmospheric temperature - 160°C
L0,5mx WO.Smx/i0.5m
Synchroservo system, with low-high temperature testing device
Max. load: 20 t
Electro-hydraulic system
Loading capacity: +100 t
20 t
Stroke 170 mmpump. In this tank, the behavior of the sit-on-bottom type or floating offshore structures subjected to wave or tidal current forces can be experimented. Towing test, oscillation test and drag test taking the effect of the sea bottom into consideration, investigation of the scouring
phenomenon of the sand at the structural bottom,
penetra-tion test into clay and test of sucpenetra-tion which is experienced at the time of taking-off the legs of structures from the sea bottom can also be conducted in this tank. It can also be used for testing the holding power of the mooring anchor and sinker which are indispensable for offshore
structures.
This tank was completed in the spring of 1969 and has been used for the testing of offshore oil drilling units, working barges and various kinds of platforms in operating, transit and installation conditions. The results of the tests are reflected on their designs.
3.2.1.2 Testing machine for large structures
This testing machine is capable of testing the strength of structures against compression, bending and shearing load by use of a large-sized model and is used for the
structural tests with overall or local models.
The joints of the members of offshore structures
N am e Specifications
Tank: L 40m x W4.5 m xH 1.0 m Soil tank: L 20m x W 4.5 mxH 1.5 m
Offshore structure experimental tank
(with circulating & wave-making devices) Wave: Sine wave and irregular wave
(Wave length up to 4m) (Wave height up to 0.15 ml
Flow: Flow rate up to 1.5 m3/s
Test model:
L l2mxW4OmxII 35m
Large structure testing machine
Loading capacity: 200 t
Electro-hydraufic servo system
Random fatigue testing machine Loading capacity: ±50 t Stroke ±120 mm Repetition velocity: 0 50 Hz
MTB 121 May 1977
(cylindrical or other shapes> are not only. complicated in shape but also are subjected to large repeated loads, so their fatigue strength is important. Fatigue strength test
using models simulating actual structures is conducted by
use of a random fatigue testing machine. This machine has a large-capacity hydraulic lack and is capable of
pro-ducing, besides sine waves, 10 stages of programed wave
forms taking the repeated fluctuating load caused by
ocean waves into consideration, and therefore, can be used for more practical fatigue strength tests.
3.2.1.3 Seismic shaking table
This is one-directional shaking table about 3m square and is effectively controlled to produce sine waves, 10 stages of programed wave forms and is capable of repro-ducing the wave forms of actual earthquakes. lt can be used for testing the vibration response of offshore
struc-tures.
3.2.1.4 Underwater automatic welding experimental facility
This device is used for making experiment on the
execution of underwater welding of offshore structures. Its tank is provided with an external inspection window, an underwater lighting fixture and an underwater TV
camera. Equipped with automatic underwater welders (flat, vertical and horizontal>, the lighting fixture and TV
camera, the device can be remote-controlled. Experiments
to make clear the problems of automatic underwater welding are performed by use of this facility.
3.2.1.5 Other facilities
Materials for offshore structures are used under severe operating and loading conditions and, in addition, they are exposed to low temperatures, depending on their operating water areas. Therefore, it is necessary that the materials be subjected to various kinds of strength tests, fatigue test and fracture test under various temperature conditions.
The universal testing machine of electronic measure-ment control system is equipped with a low-high tem-perature testing device and is used for fatigue test along with the universal fatigue testing machine.
The automatic temperature-control cooling tank is
used for brittle fracture tests at low temperatures. The constrained type welding crack testing machine with a constant load and constant marker point holding device is used for welding crack tests.
3.2.2 Brief description of results of studies
3.2.2.1 Study on the sea bed soil
The offshore structure experimental tank is a
recirculat-ing one havrecirculat-ing a clayish soil tank and a sandy soil tank. The clayish soil tank is used for the suction breaking
tests of sit-on-bottom type offshore structures and penetra-tion test of self-elevating type offshore structures. The
sandy soil tank is used for the scouring test of the bottom,
the holding power test of the anchor and sinker and the sand compaction test for improving the soft mud ground.
Fig. 7 shows the scouring test.
From these tests, various data were obtained as
men-Fig. 7 Scouring test
tioned below.
Suction breaking test Data obtained:
o Mechanism of suction force acting on
bottom-sitting parts of various shapes.
O Effect of suction breaker for reducing suction
force(18).
O Shape of bottom which has superior effect for
reducing suction force.
o Behavior of structures
at the time of suction
breaking (stability).Penetration test Data obtained:
O Relation between the bearing capacity of legs
and penetration.
O Mechanism of penetration of legs of various shapes Scouring test(1S)_(2)(23),(24)
Data obtained:
u Grasping of scouring phenomena occurring around
the periphery of various shapes of structures at
sea bed surface.
O Determination of parameters contributing to
scouring phenomena and estimation of scouring
depth.
o Study on effective bottom shapes of various kinds
of structures for the prevention of scouring. Holding power test
Data obtained:
o Characteristics of holding power of anchors and
sinkers of various shapes.
O Selection of the optimum shapes of anchors and sinkers for various kinds of sea-bed soils.
(5> Compaction test on sand(21),(22)
o Compaction characteristics of sand by vibration. The data obtained are not only used for the study of
the local strength of the bottom of structures (legs),
supporting condition for structures, their stability and the
scale of mooring facility but also are applicable to planning and design of operation manuals.
3.2.2.2 Study on hydrodynamic force
Since the offshore structure experimental tank is capable
of producing waves and flow simultaneously or inde-pendently, we investigate wave and tidal current force,
Fig. 8 Caisson sinking test (Honshu-Shikoku Bridge Au-thority)
towing resistance acting on various kinds of offshore structures or plant barges, interference or sheltering effect
of multi-row cylinders under steady flow conditions such
as seen around pile piers25, and the behavior of caissons
of bridge piers at a time of installation. Fig. 8 shows
caisson setting test.
The data obtained by these tests are effectively used for the structural design of various kinds of offshore structures, the drafting of towing program and the study of installation procedures for the foundation structure of the bridges connecting the mainland with Shikoku after their verification by field measurement with actual
equip-ment or large-sized models.
3.2.2.3 Study on structural strength
Design conditions for offshore structures have become severe with their advance to very deep sea areas, and
increase in size, and they have various problems in their
structural strength as well as their complicated shapes. The Technical Institute is carrying on strength analysis with a large-sized computer and is conducting strength
and fatigue tests on structures by use of a large structure
testing machine and random fatigue testing machine. Tests conducted by use of the large structure testing machine are the measurement of stress and deformation of each member of such structures under typical loads caused by ocean waves including longitudinal bending,
transverse bending and torsion, the ultimate yield strength
of the overall structure and the stiffness distribution in the overall structure. The results of these tests are com-pared with the results of strength calculation. An example of the test is shown in Fig. 9.
As regards local structures, the intersection parts or joints of members have problems on the vïew point of
strength. Regarding the state of stress transmission and
the degree of stress concentration in the joints of members
as parts of discontinuity, in particular, strength tests are
Fig. 9 Structural test (Aquapolis)
Fig. 10 Structural test of member joint
made with local structural models, and programed fatigue tests(29)_(31) assuming the fluctuating loads caused by ocean waves to actual equipment are also conducted. The results of these tests are reflected on the design of large structures. Fig. 10 shows an example of structural test on the joint of members.
Among local structures, the joints where cylindrical
members intersect are so complicated in shape, that much
attention should be paid to both fatigue strength due to stress concentration and execution. The Institute made studies on the reasonable structures of the joints to ease
welding work or to reduce stress concentration, by
chang-ing the ends of cylindrical members from a conventional circular section to a square section developed as a box type joint28. This box type joint has been adopted in the rigs and the Aquapolis built by our company.
3.2.2.4 Development of computer program for
theoretical analysis and full scale field measurement
In parallel with the experimental studies mentioned above, systematic computer programs for the following items were developed and systematic experiments and
MTB 121 May 1977
full scale field measurement at sea to verify the scope of application and accuracy of' the computer programs have
been conducted32 (33) (Fig. 11).
Motion analysis: Systematic computer program for
the motions of semi-submersible offshore structures.
Structural analysis: Systematic computer program for the dynamic structural analysis of
semi-submersible offshore struc-tures.
Mooring analysis: Systematic computer program for mooring of floating offshore
struc-tures.
Fig. 11 Semi-submersible drilling platform (Hakuryu II)
The structural analysis program has been developed for
high-accuracy structural design, emerging from the rule
calculation based on experience engineering. lt was applied
to the new-type oil drilling rig "Ocean Rangerette" jointly developed and designed by our company and ODECO
of the United States, as well as to the rigs designed by our company.
3.2.2.5 Study on aseismatic strength
To investigate the vibration response, particularly seis-mic response of structures, the Institute started theoretical
approach of structures for land use long ago and has
conducted experiments with seismic shaking table, gaining several achievements34.
In the field
of oceanographic engineering, the Institute is also conducting various studies,making the most of its basic techniques, for example, the study on the effects of ambient ground on submerged
tunnel35 and the study on the seismic response of the plants installed direct on the sea bottom.
3.2.2.6 Underwater automatic welding system As a new underwater welding system which is useful for oceanographic engineering and has about the same dependability as those used on land and moreover, can
be operated automatically by remote control, the Technical
Institute developed a new underwater welding process in
local gas phase zone by utilizing the various effects of water jet(36)_(39). The Institute has been conducting the basic development of an automatic system jointly with
Japan Ship's Machinery Development Association and Mitsubishi Electric Corporation since fiscal 1974°.
In this system, only the welder is sunk in a large
tank and its operation, supervision and controls of various
kinds are all conducted by a remote control panel installed
on land (outside the tank) via a TV monitor. A system developed for flat, vertical and horizontal positions experi-mentally proved that it is capable of welding safely and efficiently without the help of a welding operator, obtain-¡ng almost the same welding results as the conventional
welders on land.
As the first step to practical study, the Institute is
scheduled to start an offshore joining experiment of
model blocks of assumed structures. On the other hand, it intends to set about the technical development of a
comprehensive underwater operation system including the
research of peripheral techniques concerning the installa-tion of objects to be welded, and their underwater cutting
and inspection and to put the techniques into practical use.
3.2.2.7 Lamellar tearing preventing
technique4'44
The
joints of the
cylindrical members of offshorestructures produce a very high constrained stress in the direction of their plate thickness and as a consequence, welding crack called lamellar tearing as shown in Fig. 12
is apt to occur in the joints. The welding crack is
dif-ficult to repair if it once breaks out.
The Technical
Institute made a joint study on this
problem with Nippon Steel Corporation and succeeded in
making clear the causes of amellar tearing and developed
an anti-lamellar tearing steel in which non-metallic inclu-sions are much reduced by desulfurizing and degassing
treatments,
However, a wide range of adoption of anti-lamellar
tearing steel results in a large increase of the manufacturing
costs of offshore, structures. In order to make clear its scope of application and develop a material selection
method, the Institute conducted a series of studies for
classifying the value of the plate thickness-directional constrained stresses produced in various kinds of fillet
welded joints by utilizing the Moire's strain measurement
method.
Studies on a welding design method to reduce plate thickness-directional constrained stress and procedure of its execution were also conducted in this Institute and as its result, the problems of lamellar tearing occurring in
offshore structures was solved from both engineering
technique and economic standpoints.
3.2.2.8 Selection of materials and welding process for oil drilling units operated
in low-temperature water areas
To cope with the increasing demand for energy on the
global scale,
ol
field exploitation tends to extend todeeper and colder water areas. These Water areas are not
only extremely cold but are exposed to severe environ mental conditions such as strong wind, waves and ice drift. Consequently the prevention of brittle fracture is
an important matter for the safety of the structures operat-ing in these areas.
In this background, the Institute conducted various kinds of large-scale brittle fracture tests on 8 kinds of
steel plates and their welding joints ranging from mild steel plates to 80 kg/mm2 high tensile steel plates used for structures operated in cold districts, and also made cylindrical joint model fracture test as shown in Fig. 13.
In parallel with these large-scale tests, various
small-scale industrial tests such as Charpy impact test, COD
test
and DT test were carried out
in this Institute,enabling the toughness required for the prevention of the brittle fracture of structures to be determined in
accord-ance to the lowest working temperature of the sea area where they are operated. As the result, the selection of materials which depended on experience in the past has come to be made more reasonably and with a high
1000 t large-type fracture toughness test machine
Table 4 Principal particulars of material testing facilities for deep sea submergence vehicles
Specifications
Pendulum type
Max. impact capacity: 3000 kg-m
Max. impact velocity: 8 m/s Max. specimen thickness: 100 mm
Single lever type ILever ratio 30 : 1)
Capacity: Tension lOt Bending 10 t
Measuring device: Time integrating indicator for recording fracture time
Electro-hydraulic servo system Max. loading capacity: ±200 t
Max. repetition velocity: 1.0 Hz
Control: Load, stroke, marker point elongation
Electro-hydraulic servo system
Max. loading capacity: Static ± 1000 t
Dynamic ± 500t Max. repetition velocity: 1.5 Hz
Control: Load, stroke, marker point elongation
Fig. 13 Fracture test of cylindrical joint model
dependability.
3.3 Takasago Technical Institute
The Takasago Technical Institute is equipped with
material strength testing machines and pressure resistance
test apparatus mainly for the materials and equipment used in deep submergence vehicles. A large scale earth-quake simulator and a test plant for converting sea water to fresh water, which are proving a great effect on the
development of oceanographic instruments and structures
are also equipped in this institute.
3.3.1 Research facilities
3.3.1.1 Test facilities for materials used for
deep submergence vehicles
For materials used for submergence vehicles to operate
in deep seas of the 6000m level, it is necessary to quanti-tatively grasp the various properties required to secure a high reliability at deep sea environment such as
com-Use
Ductile-brittle fracture tests
Stress corrosion crack test
Low-cycle fatigue test
Fracture toughness test Nam e
DT test machine
SCC test machine
200 t low-cycle fatigue test
MTB 121 May 1977
pressive strength, fracture toughness, stress corrosion crack
sensitivity and low-cycle fatigue strength and to reflect the results of these researches on design, fabrication and
inspection techniques.
As the objects of these tests are thick high-strength materials, specially large-capacity test facilities different from the conventional test facilities are necessary for
these tests. The Technical Institute has been pursuing enthusiastic research activities since fiscal 1970 by use of a large-capacity DT test machine, a SCC (stress
cor-rosion crack) test machine, a low-cycle fatigue test ma-chine and a i 000-ton large-type fracture toughness test
machine.
(1) DT machine
This DT test machine is used for impact bending fracture
tests to thick high-strength steels as designed thickness,
whose absorbed energy transition phenomenon cannot be made clear by the conventional Charpy impact test. Fig. 14 and Table 4 show its external view and principal particulars
respectively. With the maximum capacity of 3,000 kg-m and the maximum impact velocity of 8 m/s for specimens with the maximum thickness of 100 mm, this DT test
Fig. 15 External view of SCC test machine
machine is the largest one of its kind in Japan. SCC test machine
lt is generally said that high-strength steels have high sensitivity to delayed fracture and stress corrosion crack and this problem ¡s an important factor ¡n the study of
materials in the oceanic environment.
With the progress of the quantitative evaluation method applied fracture mechanics, ¡t has become possible to
evaluate materials by obtaining what is called (critical value for stress corrosion crack initiation).
This test machine makes evaluation of the above for thick materials, being capable of SCC tests under tensile and bending loads (Fig. 15).
Low-cycle fatigue test machine
A deep submergence vehicle is subject to cyclic load,so
its low-cycle fatigue characteristic is an important factor
in its design.
factor in its design.
Particularly, thick high-strength steels are low in duc-tility as compared with thin ordinary-strength structural
steels and it ¡s presumed that their low-cycle fatigue
strength is reduced by deep sea service. Since t is essential
Fig. 17 1200 kg/cm2 large-scale pressure test apparatus Fig. 14 External view of DT test machine Fig. 16 External view of 1000-t large-type fracture
to grasp their crack initiation time and crack propagation characteristic and reflect the results on fatigue design, a strain control type large-capacity low-cycle fatigue test machine has been installed.
(4) 1000-ton large-type fracture toughness test machine
In order to verify the safety of structures against brittle fracture, a large-type fracture toughness test ma-chine based on the ASTM E 399 is installed. This test
machine is designed to be capable of applying brittle
fracture test by use of specimens with fatigue crack. It is of the highest class among its kind in Japan both in
capacity and accuracy (Fig. 16).
3.3.1.2 Pressure resistance testing apparatus
The studies and development of new design systems,
materials, structures and construction techniques are
in-dispensable for the development of deep submergence vehicle having high safety and high performance, and to
accomplish these studies it is imperative to equip pressure resistance test apparatus capable of reproducing load conditions close to the actual load conditions under which
the submergence vehicles are operated.
The deep submergence vehicle consists of
pressure-resisting shell made of high-strength material, electric power
unit, motor, hydraulic apparatus, pump, buoyancy mate-rials, and various kinds of equipment and outfits installed on the outside of the pressure-resisting shell, and each of these components are exposed to high water pressure
higher than several hundred atmospheric pressure.
There-fore we must execute a wide range of static pressure
test and pressure fatigue test, for which pressure resistance
test apparatus suited to each object are required.
(1) 1200 kg/cm2 large-scale pressure test apparatus (Fig. 17)
This is the first unit for static compression test in
Japan and is used for collapse test with scale models and
for static compression test of pressure-resisting equipment
aimed at the establishment of a design theory for the
pressure-resisting shells of submergence vehicle.
Table 5 shows its principal particulars. Its maximum working pressure i.e. 1200 kg/cm2 is two times the water
pressure applied t a submergence vehicle of the 6000m
class and corresponds to the water pressure at the deepest
part of the ocean. It was designed and manufactured in our Kobe Shipyard & Engine Works.
Small scale pressure test apparatus
The Technical Institute is also equipped with various kinds of small scale pressure test apparatus used for the
pressure resistance test of buoyancy materials and equip-ment parts and for the pressure resistance and under-high pressure performance test of small-scale equipment (Table 6).
Pressure fatigue test apparatus
This apparatus is used for the fatigue test of specimens
in combination with various kinds of pressure resisting tanks mentioned above. It uses oil pressure as pressure medium. It can also be used for fatigue test with water pressure by use of an oil-water converter.
3.3.1 .3 Other test apparatus
2-directional large sclae earthquake simulator
The Technical Institute developed, in 1973,an epochal
2-directional large scale earthquake simulator which is
capable of simultaneous shaking in two directions. Table 8
shows its principal particulars. The earthquake simulator
is used for the basic and applied studies of aseismatic
techniques of various kinds of structures such as the
equipment for nuclear power plant, boiler furnaces,
under-water tunnel with steel shell and underground tank. Equipment for converting sea water into fresh water A 100 t/d pilot plant of a multiple-stage flash evaporat-ing type plant for convertevaporat-ing sea water into fresh water for the joint research and development with Tokyo Electric Power Co., a pilot plant of in-cycle type desalina-tion equipment combined with a thermal power plant and
a pilot plant of multiple-effect horizontal tube film
evaporating type desalination equipment producing fresh water are installed in this Institute (Table 9, Fig. 18).
3.3.2 Brief description of results of studies
3.3.2.1 Study on deep submergence vehicle The research activities on ocean engineering technique
conducted by the Takasago Technical Institute is
con-centrated on the equipment used in deep sea or at sea bottom as mentioned above. Concerning submergence
vehicles, details are reported in another paper. For the
ultra high strength thick steel plates used for the
pressure-Table 5 Principal particulars of 1200 kg/cm2 large scale pressure test apparatus
Pressure-resisting tank Pressure pump
Max. working pressure 1200 kg/cm2 Max. pressure 1200 kg/cm2 Inside diameter 600 mm Flow rate 5 Q/min Outside diameter 1000 mm
Length of internal straight part 1810 mm Measuring instruments Overall length 2900 mm
Pressure measuring instrument 1 set
Internal capacity 530
Medium for pressure Water or oil Digital strain measuring instrument i set
Sealing Bridgeman type seal
MTB 121 May 1977
Table 6 Principal particulars of small-scale pressure test apparatus
Table 8 Principal specifications of earthquake simulator
Item Dimensions of table Weight of table Output Output wave Frequency Max. amplitude Exciting system Critical performance Loading capacity Name
Field test equipment for
heat transfer tube material
Multi-effect horizontal tube film
evaporation testing device
Specifications
6x6x1 m
21 t
In case of horizontal 2-directional shaking 50 t-g each direction
In case of horizontal 1-directional shaking 100 t-g
Sine wave, seismic wave, random wave
0.1-5.0 Hz ±50mm
Electro-hydraulic servo system
3.7 Hz, 1 g
100 t (max)
resistant hulls of submergence vehicles, the Technical Institute developed a material testing method based on new criteria and entirely different from the conventional steel material testing method by the systematic tests as
mentioned below(45),(46),(47), Further, on the basis of the
testing method, the Institute grasped the actual state of the fatigue and toughness of the steels used and gaIned confidence on the superiority of 10 Ni-8 Co steel which
Table 7 Principal particulars of pressure
fatigue test apparatus
i
Fig. 18 Multi-effect horizontal tube film evaporation
system testing device
particulars of experimental equipment for converting sea water into fresh water
Specifications
Type:
Capacity of producing water:
Heat transfer tube Heat rei ection section: Heat recovery section: H eater:
Working steam pressure: Max. temperature:
Circulating brine flow rate:
Multi-stage flash evaporation type
24 t/d 419 x (1.2 x /2000 x 20 pcs. x 2 stages 419 x (1.2 x /2000 x 10 pcs. x 4 stages x 2 series 41.9 x tl.2 xl2500 x 20 pcs. x 2 series 3 kg/cm2 G 120°C 7 t/h x 2 series Type:
Capacity of producing water:
Heat transfer tube:
Working steam temperature: Max. temperature:
Circulating brine flow rate:
Multi-effect horizontal tube film evaporation type 12 t/d pl9xtl.2x 12330 x66pcs. 450 x (1.6 x 12330 X 24 pcs. 3.5 kg/cm2 G 120°C 5 t/h Remarks National project Internal study
is one of the most expective material for the deep
sub-mergence pressure- resistant hull.
o Study on the basic characteristics of the materials for
pressure-resistant hulls of deep submergence research vehicles and their welding method (under the subsidy of Ministry of Transport for fiscal 1970).
O Study on the fatigue characteristics and fracture tough-ness of the materials for pressure-resistant hulls of the
No. 1 tank No. 2 tank No. 3 tank
Max. Static working pressure pressure Repeated (kg/cm2) pressure 1400 700 1400 300 700
-Type Cylindrical Cylindrical Cylindrical
Internal Diämeter dimensions (mm) Depth 200 600 300 450 160 300 Max. compression force 1200 kg/cm2 Max. repetition velocity 30 cpm Pressure regulating range 35 1200 kg/cm2 Pressure fluctuation width ±5% Pressure Accuracy holding
time lOs-30 min of detector
±1%
