Deep-Sea Water Suction Technology
by Takumi Yamaguchi *, Tetsuo Inoue *, Masao Hirakawa *, Satoru Abe *,Ken’ichi Ishii *2, Toru Kagoura *2 and Masanobu Fujiwara *3

In the area of deep-sea water suction technology, Furukawa Electric has built
an excellent track record of laying eleven deep-sea water suction pipes in sevenlocations since its first domestic laying in Muroto City, Kochi Prefecture in 1988. During thistime, we have introduced various improvements in the laying method as well as in the design ofmaterial structures including suction pipes, thereby making it possible to manufacture and install
the suction pipes up to 280 mm in diameter, 680 m in laying depth, and 7200 m in pipe length.

ABSTRACT1.

INTRODUCTION

While it seems that deep-sea water has got through theboom becoming widespread in our daily lives, Furukawa
Electric is maintaining a top share in the business of deepsea water suction pipes.
It has been fifteen years since we laid the Japan's
first deep-sea water suction pipe. During this time, wehave introduced various improvements in the installation
method and the design of suction pipes to carry out
further developments. Explanation of deep-sea waterand technological achievements will be presented in thispaper.

2.

ABOUT DEEP-SEA WATER

Although not a very precise definition scientifically, deepsea water generally refers to sea water that lie in thesea about 200 meters or more in depth where sunlightno more reaches. The characteristics of deep-sea watercomprise three elements of “stabilized low temperatures”,“rich nourishment”, and “cleanliness”. Moreover, studies
have recently advanced to draw attention to “maturity” and“richness in minerals”.
Thus efforts are being made in various fields to utilize
deep-sea water as a new natural resource, taking
advantage of such characteristics.
2.1 Application Fields of Deep-Sea Water
Deep-sea water is mainly utilized in such diversified
fields as fisheries, food and beverages, environmental*

Electric Power Engineering Dept., Power Cables Div.
Energy Transmission Research Dept., Ecology & Energy
Lab.
*3 Power Cable Production Dept., Power Cables Div.

conservation, health-beauty-and-medical, energy andresource, and agriculture. Each field is making efforts
to study, develop, and practically apply deep-sea water
leveraging its characteristics.
With respect to its rich nourishment, for instance, thewater is expected to have much effect on aquafarmingof fish and shellfish in the fisheries field as well as on
improving meat quality in the livestock field.
In terms of its stabilized low temperatures, efforts
are being directed to cultivate -- in a warm-temperature
region-- fish, shellfish, seaweeds, vegetables, andhighland vegetables that belong to cold regions by nature.
Also, possibilities of applying the water to cooling water for
power stations and to ocean thermal energy conversion
generation are being investigated entering into the stageof practical studies.
What is more, beer, shampoo, and isotonic drink arealready in the marketplace, taking advantage of thematurity and richness in minerals of the water.
Fisheries field* Cultivation and productionof juvenile fish, shellfish,and seaweeds* Ice making (for freshness
preservation)* Laundering of fish andshellfish

Food and beverages field* Production of varieties offood and beverages

Environmental conservation* Countermeasure against
rocky-shore denudation,
Purification of seawater* Immobilization of CO2

Deep-sea water utilizedin various fields

Energy and resource field

Health-beauty-and-medical
field* Thalassotherapy* Curing of atopic dermatitis* Production of natural healthfoods* Production of cosmetics

Agricultural field* Facilities air-conditioning and * Cultivation of agriculturalindustrial cooling waterproducts with controlled* Ocean thermal energy
production and shipment
conversion generation* Production of fertilizers* Production of freshwater
for hydroponics*2

Figure 1

Application fields of deep-sea water.

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Deep-Sea Water Suction Technology

Figure 1 shows the applications of deep-sea water invarious fields that are either planned or implemented.

3.

DEEP-SEA WATER SUCTION SYSTEM

3.1 Outline of Deep-Sea Water Suction Facility
A deep-sea water suction system may be broadly divided
into suction pipe, water intake, and a shore-based facility
that pumps up deep-sea water to distribute it to individual
facility of customers. Figure 2 shows a schematic image ofthe system.
The suction pipe conveys deep-sea water from theobjective sea depth to the shore-based facility. The pipe isrequired to be in one continuous length preferably, and tohave such performance as to fit well to the ups and downsof the seabed as well as to withstand the tension expected
to occur when the pipe is suspended from the sea surface
down to the seabed during laying work.
The water intake has a structure such that it keeps theend of suction pipe at a constant height above the seabedso as not to suck in sand or sludge lying on the seabed.
The shore-based facility comprises a siphon tank, i.e.,a primary tank for deep-sea water which is installed lower
than the sea-level to maintain siphon effects; a strainer
for filtering out foreign objects; a pump for conveying
the pumped up deep-sea water to destinations; and asand filtration tank to filter out minute sand and the like inaccordance with the intended use.

steel wires directly wound via bedding layers without
using reinforcing steel tapes. Figure 3 shows the general
structure of a water suction pipe and a photo of pipe
sample.
3.2.2 Large-Diameter Deep-Sea Water Suction Pipe
As the use of deep-sea water spreads, the demand
increased rendering the conventional pipes with ordinary
diameter insufficient for enough volume of suction water.
Laying multiple pipes to increase the suction water
volume is subject to restrictions such as site requirements
and the like along with poor economical effectiveness.
Thus it was concluded that increasing the diameter of thepipe was most effective. However, increasing the pipe
diameter posed two problems as follows:
1) Problem of laying work: The pipe itself increases inweight making it difficult to hold the pipe by laying
tension.
2) Problem of manufacturing: The admissible pipe
diameter at the steel wire armoring machine may forma major bottleneck.
In an effort to solve these two problems, reduction of thewall thickness of polyethylene pipe was studied together
with weight control of armoring steel wires. Because, as
mentioned before, the water suction pipe permits lower
design pressures than ordinary water pipes, the wall
thickness of the polyethylene bare pipe was reduced
leaving the outer diameter unchanged to increase
Zinc-galvanized steel wire

3.2 Deep-Sea Water Suction Pipe3.2.1 General Structure of Deep-Sea Water Suction
Pipe
The steel-wire armored polyethylene pipe (submarine
water pipe by the brand name of “AQUALEX”), which
Furukawa Electric has been supplying since 1969,is basically suitable for meeting the performancerequirements mentioned above.
The design pressure for deep-sea water suction pipes
can be set lower than ordinary water pipes because theone end immersed in the sea is always kept open andbecause the principle of siphon is used for water suction.
Consequently, whereas conventional water pipes have astructure in which armoring steel wires are wound after
reinforcing the polyethylene bare pipe by winding steel
tapes, the deep-sea water suction pipes have armoring

Polypropylene yarn
Polyethylene pipe

Corrosion protection paint +polypropylene yarn + chalk

Sand filtration tank Pump pit
To customers´facility

GroundPipingStrainer

Seawall

Sea-level

SeabedPump

Water intake
Suction pipe

Siphon tank

Figure 2

Schematic image of deep-sea water suction system.

Figure 3

General structure and photo of water suction pipe.

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Deep-Sea Water Suction Technology

Polyethylene-coatedzinc-galvanized steel wire Zinc-galvanized steel wire
Polypropylene yarn
Polyethylene pipe

Figure 4

Corrosion protection paint +polypropylene yarn + chalkGeneral structure and photo of large-diameterwater suction pipe.

the inner diameter, thereby achieving an increase in
the water suction volume. Whereas reducing the wall
thickness might possibly degrade the sidewall pressure
resistance of the pipe, every equipment for pipe laying
was accordingly reviewed, as described later, in terms ofsidewall pressures during laying work.
The weight of the water suction pipe is mostly due to themass of the armoring steel wires, so that some of the steel
wires were replaced by polyethylene-coated steel wires toreduce the weight.
Figure 4 shows the general structure of a large-diameterwater suction pipe and a photo of pipe sample.
3.2.3 Lightweight Deep-Sea Water Suction Pipe
While the depth for deep-sea water is generally definedas 200 m or deeper, it sometimes reaches almost 700 m
depending on the site. Increased sea depth eventuallyleads to an increase in the tension during pipe laying.
We have therefore proceeded, regardless of the weight
reduction described in Section 3.2.2, to reduce the pipeweight further using polyethylene terephthalate (PET)
rods with smaller specific weight in place of polyethylenecoated steel wires.
Figure 5 shows the general structure of a lightweightwater suction pipe and a photo of pipe sample.
3.2.4 Deep-Sea Water Suction Pipe Using PE-100
A polyethylene material called PE-100 with better creep
performance has begun to be used as a water pipe. In

PET rod
Polypropylene yarn
Polyethylene pipe

Zinc-galvanized steel wireCorrosion protection paint +polypropylene yarn + chalk

Figure 5

General structure and photo of lightweightwater suction pipe.

Figure 6

Photo of water suction pipe using PE-100.

response to the fact that PE-100 has been acknowledged
in JIS and the standards of Japan Water Works
Association, we have applied PE-100 to the suction water
pipe for the sake of material unification.
Figure 6 shows a photo of the pipe sample.
3.3 Deep-Sea Water Intake
Deep-sea water intake where the water is taken fromshould basically be maintenance-free because, due toits considerable depth, repair work after installation to
replace the filters and the like provided against entry ofsand and sludge would cost enormous cost and time.
The water intake plays the role of a platform thatis provided to maintain the end of suction pipe at a
certain height above the seabed so as to prevent
sucking in of sand or sludge lying on the seabed. Two

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Deep-Sea Water Suction Technology

Figure 7-1 Hexangular pyramidal water intake.

types of structures, i.e., hexangular pyramidal type andtriangular pyramidal type, are applied depending on thegeographical situations of the seabed.
The hexangular pyramidal water intake shown in Figure7-1 is suitable for installation on a seabed area whose
slope is rather steep. Because the end of the suction
pipe is located at the center of the bottom face, it has astructural characteristic that the height of the pipe end
above the seabed remains unchanged on whichever face
the water intake may be landed.
The triangular pyramidal water intake shown in Figure
7-2 is suitable for installation on a muddy seabed area
where the pipe end is required to rise high above theseabed. Because the pipe end is located at the top of
the triangular pyramid, its height above the seabed ispermitted to be higher than the hexangular pyramidal
water intake. However, its position during installation
should be controlled with the greatest care.

Figure 7-2 Triangular pyramidal water intake.

Landing (See Figure 8)↓
Laying (See Figure 9)↓
Installation of water intake (See Figure 10)
Water suction pipe
Tube buoy

Winch for landing

Figure 8

Schematic image of landing work of deep-sea
water suction pipe.

Traveling direction

4.

CHANGES IN TECHNIQUES FOR
INSTALLATION OF WATER SUCTION
PIPE

Outline of Laying Work of Deep-Sea Water
Suction Pipe
In case of land transportation, the pipe has to be delivered
in short lengths capable of being carried on a truck since
it cannot be accommodated on reels due to its large
allowable bending radius. Because, moreover, shortlengths would result in too many intermediate splices atthe site dissipating too much working time, they are notsuited for ocean installation work whereby short working
period is essential not to be affected by adverse ocean
conditions. Therefore, the suction pipe is coiled up in one
continuous length in a barge with adequate load capacity
to be transported to the site. The pipe-carrying barge
travels directly to the site, where the barge is converted toa pipe-laying barge to be used during the laying work.
The procedures of laying a deep-sea water suction pipe
are shown in the flow chart here.

Pipe laying barge

Pipe laying barge

Water suction pipe

4.1

Figure 9

Schematic image of laying work of deep-sea
water suction pipe.

Pipe laying barge

Water intake
Water suction pipe
Guide wire for installation

Figure 10 Schematic image of installation work of water intake.

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First, landing work is carried out whereby the barge
loaded with a water suction pipe approaches the seashore
as near as possible, and, while attaching tube buoys,
gradually pays out the pipe afloat on the sea to land itashore. When the landing work is completed, the barge
moves forward steadily to lay the pipe on the seabed. The
landing work and the laying work are very similar to thoseof conventional water pipes and submarine cables.
But one big difference of installation work between
water suction pipe and conventional water pipe is that
one end of the former is installed in the sea. The water
intake is mounted on the end of water suction pipe, whichis connected with a guide wire for installation and isinstalled on the seabed using a winch. Whereas the endof ordinary water pipe or submarine cable stays during
installation in a position that is visible to eyes, the end ofdeep-sea water suction pipe is in the sea precluding visualconfirmation. Meanwhile, underwater camera cannot
be used in fear of entangling of the power-supply andcontrol cable with the guide wire for installation. Moreover,simultaneous installation of two linear lines of different
bending stiffness, i.e., water suction pipe and guide wiremakes it difficult to project the catenary configuration. In
addition, physical orientation of the water intake comes inconstituting a major problem.
Given the conditions mentioned above, we adopted an
installation method whereby information from underwatertransponder, the tension, pay-out length, and incident
angle of the guide wire are synthesized together to makea judgment about the seabed landing of the water intake;and a underwater camera is used after the completion ofpipe laying to visually confirm the landing situation of thewater intake. Then sonic signals are sent to actuate thedecoupling device mounted on the water intake to retrieve
the guide wire together with the decoupling device.
4.2

Development of Installation Equipment for Water
Suction Pipe4.2.1 Hauling machine
During pipe laying, the pipe has to be paid off graduallywhile being held on board not to let it run into the sea
in one go. A hauling machine is used as this holding

Figure 11 Hauling machine.

machine.
Performance requirements for a hauling machine aredetermined by the sea depth and the own weight of thepipe, so that a hauling machine that is suitable to site
conditions in terms of tension holding capacity, holder’sshape, and holder's length has to be selected to carry out
installation.
4.2.2 Large-Size Turntable
A turntable is indispensable for transporting a watersuction pipe in one continuous length.
If the pipe is small in diameter and short in length, it
may be directly coiled on a barge, but in such a case, alarge allowable bending radius is required since twisting is
introduced into the pipe by coiling.
Recently, as water suction pipes grow in diameter andlength, use of turntables has become the mainstream
technology of pipe loading since it enables small bending
radius introducing no twist. Furukawa Electric has long
been developing the turntable, and the product has beenused in the installation works of not only the company but
also other companies.
4.2.3 Barge with Onboard DPS
In conventional laying work of deep-sea water suction
pipes, anchoring method has been used to move thebarge forward whereby an anchor is set up ahead of thebarge, and the driving wire tied to the anchor is wound up
by a winch on the barge. This laying method raises two
problems to be solved such that the anchor has to be set
up in the seabed as deep as 1000 m, and that the route
keeping and proposed position keeping are easily affectedby the oceanographic conditions.
To solve these problems, we have developed abarge with DPS (Dynamic Positioning System) onboard
which is provided with capabilities of route keeping andproposed position keeping. The DPS is a navigation
system to automatically control the position of a ship,
which comprises a position measuring system based onsatellites and an associated thruster which is used tomove the ship keeping the position.
Conventionally, this navigation system has been
employed in cargo ships, but this time the system has

Figure 12 Turntable.

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Figure 13 Barge with onboard DPS.

Figure 15 Thruster.












Figure 14 Control stand of barge with onboard DPS.

been applied to a broad-beamed barge to enable loading
and laying of deep-sea water suction pipes. The barge
with onboard DPS is applicable to not only deep-sea
water suction pipes but also submarine water pipes andsubmarine cables. Although operation of this type of barge
has just begun, the DPS technology is developing day
by day, as the track record builds up, introducing various
improvements.

5.

TRACK RECORD OF INSTALLATION

Deep-sea water suction pipes have been installed atseven locations domestically, ranging from Hokkaido to
Okinawa, while each location has its own features asshown in Figure 16.

6.

IN CONCLUTION

Given the fact that we are receiving a lot of inquiries
from not only Japan but also overseas, deep-sea water
application is a business area that is expected to be
increasingly active.
In terms of its technological aspect, deep-sea watersuction is tending toward large quantity water suction

 Offshore Kumaishi, Hokkaido: Production of juvenile abalone Offshore Nyuzen-Machi, Toyama Pref.: Shipment adjustment ofmarine products, Washing water for disposal of goods
 Offshore Namerikawa-City, Toyama Pref.: Onshore breeding ofmasu salmon, Thalassotherapy
 Offshore Yaizu-city, Shizuoka Pref.: Water suction from two sea
layers of different depths
 Offshore Takaoka, Kochi Pref.: Deep-sea water supply terminal
installed for exclusive use by businesses Offshore Muroto Cape, Kochi Pref.: Japan's first facility for deepsea water suction
 Offshore Kumejima Island, Okinawa Pref.: Supply of mother prawn
for prawn breeding

Figure 16 Track record of installation of deep-sea
water suction pipe.

in such applications as fertilization of sea areas, ocean
thermal energy conversion generation, cooling water for
power stations, etc. From the standpoint of understanding
deep-sea water suction as an element of deep-sea
laying technology, the technology developed here is very
valuable since it can be extended horizontally to deep-sea
laying of submarine power cables and the like.
We will be most gratified if we could play a role,
through our engagement in deep-sea water suction, insuch aspects as the development of deep-sea water
applications, regional development, and the developmentof ocean engineering.
Lastly, we would like to express our gratitude to thosepeople who kindly cooperated with us in the development.

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