JFPA
Aqua Drive System- A Technical Guide 2

Japan Fluid Power Association

Front cover: Copyright © Town of Asakura, Fukuoka Prefecture, Japan.
Triple water mills, a national registered monument
Back cover: Fukuroda-no-taki, Ibaragi Prefecture, Japan
Copyright © 2005 by Japan Fluid Power Association

Releasing the 2nd edition of the ADS Technical Guide
Concepts such as sustainability, safety, cleanliness, and hygiene have come to keys essential fordeveloping new technologies in recent years. They have been important in domains of environmental
protection and industrial wastes in particular; the global communities have discussed on CO2 emissions,dioxin pollution, soil contamination, and water pollution from green perspectives while the industries
have concerned about the 3R approach (Reduce, Reuse, Recycle), that are closely linked to industrial
waste treatment. Today, however, those topics are no longer limited to those domains, and efforts forsolving the problems have been widely spread. The field of engineering is not an exception.
Re-evaluation of not only machines and their drives (oil hydraulics, pneumatics and electrics) but also
overall service requirements and environment has already been started in the light of environmental
and social sustainability.
Japan Fluid Power Association, or JFPA, found the movement very important and has launchedprojects, "Technical Study on Environmental Friendly Water Hydraulic Drive Systems" from 1998 to2000, and subsequently "Research and Study for the Practical Use of the Aqua Drive Technology" from2001 to 2003. These projects were made possible with the Machinery Promotion Fund by Japan
Motorcycle Racing Organization. The study outcome is the "Aqua Drive System (ADS) technology," a
new fluid power drive that solely uses "tap water" as the power transmission medium. The ADS
technology has increasingly been gaining attention in the United States and Europe as an alternative toconventional solutions.
The three-year project, "Technical Study on Environmental Friendly Water Hydraulic Drive Systems,”
released an English version of the first ADS technical guide, "Aqua Drive System - A Technical Guide"in the year 2000, and the copies were distributed at HANNOVER MESSE 2001 in April 2001. The
Guide was intended to promote the ADS technology and to offer a common ground for both component
and system suppliers to refer when they jointly develop water hydraulic applications. The project
members made a presentation on their water hydraulic technology at the Joint Water HydraulicCommittee Meeting during the MESSE. To respond to a strong demand for the Japanese version
from the JFPA members and those who are interested in water hydraulics, the Guide was translated in
to Japanese in 2001. Finally, this 2nd edition of the Guide (English version) was released in 2005 as
the summary of the ADS technology studied and gained in the six-year research. We wish this 2ndedition of the ADS Technical Guide be beneficial for people who are interested and contribute toprogress of the ADS technology in the world.
We would like to express our deep appreciation to the Industrial Machinery Division of Manufacturing
Industrial Bureau, Ministry of Economy, Trade and Industries and Japan Motorcycle Racing
Organization for their valuable inputs and sincere support.
March 2005
Japan Fluid Power Association
Kenichi Hirano, Chairman of the Technical Committee,
Atsushi Yamaguchi, Chairman of the Study Committee on ADS for Practical Applications

- Table of Contents Chapter 1

Approaches Toward Application of ADS.......................1

Chapter 2

Guide for Selecting ADS Components..........................3

2.1
2.2
2.3

List of components and suppliers ................................................................................. 3
Types and specifications ............................................................................................... 6
2.2.1 Overview of water hydraulic components......................................................... 6
2.2.2 Specifications of water hydraulic components ............................................... 10
Materials for components and systems ...................................................................... 16

Chapter 3
3.1

3.2
3.3

Water quality................................................................................................................ 18
Water quality evaluation test ....................................................................................... 18
3.2.1 Test apparatus and conditions........................................................................ 18
3.2.2 Test result........................................................................................................ 19
Guidelines for water quality control............................................................................. 21

Chapter 4
4.1

4.2

5.2

Application of Aqua Drive System ..............................36

Applicable fields of ADS.............................................................................................. 36
Published ADS applications ........................................................................................ 37

Chapter 6
6.1
6.2
6.3

Operating Aqua Drive System .....................................23

High-speed operation.................................................................................................. 23
4.1.1 Experimental apparatus and method ............................................................. 23
4.1.2 Experimental results ....................................................................................... 25
4.1.3 Simulation ....................................................................................................... 29
ADS operational guideline........................................................................................... 32
4.2.1 Pressure loss and flow rate ............................................................................ 32
4.2.2 Surge pressure prevention ............................................................................. 33
4.2.3 System configuration and operational considerations.................................... 34

Chapter 5
5.1

Water Quality Control for Aqua Drive System ............18

Future Perspectives of Aqua Drive System ................40

Social demand and ADS ............................................................................................. 40
Market and prospects of ADS ..................................................................................... 40
Boosting the ADS-related industries ........................................................................... 41

JFPA Water Hydraulics Committee Members:Companies and Universities ........................42“Technical Study on Environmental Friendly Water Hydraulic Drive Systems” from 1998 to 2000
“Research and Study for the Practical Use of the Aqua Drive Technology” from 2001 to 2003

Chapter 1 Approaches Toward Application of ADS
Fluid power technology that uses water for power transmission has already been utilized at the end of the
18th century. The technology of the time was focused more on transmitting a huge power. However, it
involved many problems, such as low efficiency due to leakage and material deterioration resulted from wear,
friction, and rust. All these were blamed on low viscosity of water. Not to mention, nothing was done totreat and maintain the working water.
Later, various kinds of water-based fluids, of which rust-prevention, corrosion resistance, and lubricating
properties have been improved by adding additives to water, have begun to be used for press and mining
machines. The major advantage offered by these fluids is flame resistance; therefore, they have been wellapplied to iron manufacture facilities where the danger of fire was the most concern. A water hydraulic drive
system is often recognized just as "water hydraulics" in a boarder sense, and most likely, it uses water-based
fluids.
The “Aqua Drive System (ADS)" in this technical guide, on the contrary, is differently defined from theconventional term above; it solely uses tap water or pure water for its power transmission. ADS is not a
substitution of existing system drives: it is a solution for various systems to maximize their overall
advantages while minimizing risks inherent in use of conventional oil hydraulic, pneumatic, or electric drives.
(1) Oil-free
・ The aqua drive system consists of components
without lubricating oil, working oil, andmechanical oil.
・ The driving characteristics of the aqua drive
system are equivalent to those of theconventional driving technologies, such as byelectricity, oil hydraulics, and pneumatics.
(2)

Fig. 1.1

Life Cycle Assessment (LCA) compliant
The concept to evaluate the viability of thesystem・ Resource and energy saving.
・ Environmental
conservation,cleanliness
required for the environmentally sustainable
manufacturing process, safety in hygiene.
・ Overall cost performance, including the initialcost but also service, maintenance, andmanagement costs, etc.

(3) High technology supported
・ Today's cutting-edge fundamental technologies
in the fields of ceramics, engineering plastics,
and advanced surface treatment technology.
・ Computer-aided technologies in design andanalysis, as well as in control and management.

Three elements supporting
aqua drive technology

Advantages(1) Availability: The readily available tap water isthe system fluid.
(2) Easy to dispose of: The used water can bedamped to the rivers and sewage without
special wastewater process or can be recycled
as required.
(3) Low management cost: Costs for purchaseand management of the fluid are low.
(4) Low environmental impact: Even upon an
accidental leakage during the operation, the fluid
is non-odorous, non-toxic, and harmless.

Fig. 1.2

1

Environmentally sustainableaqua drive system

(5) Superior compatibility with products: The system is very clean, and hygiene control is easy.
(6) Fire resistance: ADS uses water, a fire-resistant fluid. This ensures fire safety and makes the system
excluded from objects to which the Fire Defense Law is to be applied; the system is superior to any otherdriving system in regards to fire insurance and safety management.
(7) Low pressure loss: Water's low viscosity contributes to reduction of pipe pressure loss and easy
system expansion. Because of this, the user can even save power required when compared to that
required for the oil hydraulic system of the same size.
(8) High response: High fluid stiffness provides rapid power transmission.

Potential application fields of ADS
Optical, medical,
pharmaceutical,
precision molding, andpaper machines

Machines forsemiconductors,
electric parts, etc.

Machines for foodprocessing, beveragebottling, packaging

General production
and manufacture lines

Cleanliness
Sanitation
HACCP
Oceanfront, river,and lake
construction
machines

Natural environment
conservation

Factory-basis water hydraulic net
system/emission-free production process(Resource and energy saving)ISO 14001

Machines for hightemp./explosive
areas (steel,rolling, volatile
areas )

Work
environment

OHSAS
18001

ISO 12001

ISO 9001 Safety/prevention on explosion

ADS Technology(Aqua Drive System)

Machines in radio
active areas
in-water/in-ocean

Specialenvironmental area

Safety on in-house/amusement
area

Fire fighting andrescue tools

Welfare/universal houseequipment

Oil-free machinery elements,
such as bearing, gear, ball screw,
speed reducer, etc.

Leisure complex, sports,
and amusement park
equipmentace
vel surf
Hig h-lent
treatmeHigh-precision
processing

Incre
ased
reli

Bi
me
tal
l

ic

jun
cti

on

w

Fig. 1.3

nt

Ad
va
n
ap cedpl co
ica mtio pu
n ter

e
atm

e
fn
no
tio lsca riapli ate
Ap m

W

e
r tr
ate

abilityIncorporationof high-technology

Applicable fields of ADS and their supporting technologies

Problems to be solved(1)

Lubrication property and sealing characteristic: Water's low viscosity deteriorates the lubrication
property, leading to decreased efficiency by leakage from slight gaps of the system components or byincrease of wear and friction on the mating faces of moving parts and deteriorated sealing.

(2)

Cavitation prevention: Water’s high vapor pressure easily initiates cavitation and erosion, whichcause material deterioration.

(3)

Rust prevention: Rust is easy to be generated.

(4)

Water quality maintenance: In the fluid, bacteria, sludge, and slime are developed.
compounds are deposited.

Metal

These problems unique to the "aqua drive system" can be solved through careful selection of component
structures/materials and by use of advanced designing methods with computers. Applying today's high-end
technology is also beneficial for the materials and the surface treatment.

2Chapter 2 Guide for Selecting ADS Components
2.1

List of components and suppliers

Figure 2.1 lists the categories of the ADS components.
Positive
Displacement

Pumps

Centrifugal
Actuators

MotorsCylinders

Aqua
Drive
SystemRotaryAxial
RadialVane
Reciprocal
Axial
RadialVane
TurbineDirectional
Pressure
Flow
Servo & Proportional

ValvesPiping, Hosing, Fitting
Tanks
Filters
Accumulators
Heat exchangers
Water quality control units
Sensors
OthersAccessories

Controllers

Fig. 2.1

Devices and accessories that configure ADS

Table 2.1 lists suppliers of water hydraulic components and accessories for ADS in Japan. As of
September 2003, 64 companies either manufacture or supply water hydraulic products: 59 of those are themember companies of JFPA and 5 are non-member companies.
The water hydraulic components in Table 2.1 are selected based on Fig. 2.1 and the component lists
included in our publication, Fluid Power Industry in Japan. The pump category, centrifugal pump, is omitted
from the tables and no supplier/product information on the item is given this time. A valve category“Cartridge valve” is added to the table. Accessories such as sensors and pressure switches are included in“Measuring instruments.” “Heat exchangers” include coolers. “Fittings” and “Piping Materials” are grouped
as one category in the tables. “Others” include gauge cocks, surge dampers, and mechanical seals. The
category, “Water-base fluid,” although included in listed in Fluid Power Industry in Japan, is omitted in Table
2.1.
The symbols indicate availability of the listed water hydraulic components: for production, ○ or ●, andfor sales only, △ or ▲. The data of the component manufacturers and suppliers in the following pages
are made based on the data in Fluid Power Industry in Japan, questionnaires and study of productcatalogues of the members from 2002 to 2004 by our Water Hydraulics Committee. The symbols indicate
availability of brief specifications of the items in Tables 2.2 to 2.7 in Section 2.2.2. Only the components of
the responders to our questionnaires or surveys are listed in the following tables.

3

Table 2.1 Water hydraulic component manufacturers and suppliers (1/2)

Hoses

Packing

●

▲

▲

▲

▲

●

▲

○

EATON FLUID POWER LTD.

●ASK CORPORTION

EBARA RESEARCH CO., LTD.

△

○

○

○

△

△

○
△

●
○

△

OHSAKA INDUSTRIES CO.,LTD.

●

OSAKA JACK CO., LTD.

○

●

A

●

F

●

F
A

○
○

●

F
F

●

○

NOK CORPORATIONOIL DRIVE KOGYO LTD.

●▲

IHARA SCIENCECORPORATIONSMC CORPORATION

Membership

Fittings &Piping materials●○

ARAKI IRON WORKS LTD.

OthersPower units

Heat exchangers

Filters

Measuring
instruments

Pressure Intensifiers

Accumulators

Servo valves

Proportional valves

Cartridge valves

Directional valves

Flow control valves

Water hydraulic
Jacks

Cylinders

MotorsPositivedisplacement pumps

Company(64 in total)

Pressure control
valvesWater Hydraulic Component and Accessory

Products

●

F

▲

F

F

●
○

▲

F

▲
●

OHTSUKA CO., LTD.
KATSUMA STEEL TUBE CO.,LTD.

●

KAMUI CO., LTD.
KAYABA INDUSTRY CO., LTD.

○

○

●

KAWAJYU SHOJI CO., LTD.

▲

▲

▲

KITAMURA SHOKO CO., LTD.

○KOSHIN SEIKOSHO, LTD.

○

KOKUSAI KOGYO CO., LTD.

▲

△

○

○

△

△

△

▲

▲

▲

▲

▲

▲

△

F
F

●

A

▲

▲

▲

△

○

▲

●

▲

○

▲

▲

▲

▲

A

▲

▲

▲

▲

▲

▲

▲

▲

▲

▲

▲

▲

A

A
F

▲

KOYO CO., LTD.

F●

KOYO SEIKI CO., LTD.
SAKAGAMI SEISAKUSHO
LTD.

F

●
●

SANMAX CORPORATION

A
A

●

○

○

○
●

CKD CORPORATIONJAPAN PNEUMATICS CO.,
LTD.

○

●

●

▲

▲

▲
F

●

○

△
●

JUNKOSHA CO., LTD.

A●SHINTO BRATOR, LTD.

●ANIPPON STEEL CORPORATIN●

A

SUGINO MACHINE LTD○

SUMITOMO PRECISIONPRODUCTS CO., LTD.

●TAIYO, LTD.

○○

Note 2)
Note 3)Note 4)

▲

●

△

▲
F

●

△

△

△

△

△

△

▲

▲

▲

△

▲

△

●

TAKAKO INDUSTRIES INC.

Note 1)○F○

TAIYO INTERNATIONALCORPORATIONDANFOSS K.K.

○

△

▲

F

▲
●

△

△

△

F

○ & ●: components for production. △ & ▲: components for sales. Brief specifications of the products, only with○ or △, are available in Tables 2.2 to 2.7 in Section 2.2.2.
These tables are compiled based on Table of Products in Fluid Power Industry in Japan issued in September 2004
and results of the survey conducted by the Committee.
The “Membership” indicates the statues: ”F” for a full membership and “A” for an associate membership.
Water hydraulic technology developed by Ebara Research Co., Ltd. has been transferred to Takako Industries Inc., afull member of Japan Fluid Power Association.

4

Table 2.1 Water hydraulic component manufacturers and suppliers (2/2)

Hoses

Packing

▲

▲

▲

●

●

△

△

△

▲

●

TOYOOKI KOGYO CO., LTD.

△

△

△

○

○

●

F
△

▲

△

▲

▲

●

○
▲

○

△

▲

▲

F
A

●

NIPPON ACCUMULATOR CO.,
LTD.

○

A

●

●

A

●

F

●

●
○

▲

F

●

A

F

●
●

A

▲

NIHON PALL LTD.

F○

MOOG JAPAN LTD.
PARKER HANNIFIN JAPANLTD.
PACIFIC SOWA
CORPORATION

▲

▲

▲

A

▲

A

▲

A

●

HIYOSHI KOGYO CO., LTD.
HIROSE VALVE INDUSTRY
CO., LTD.

●

F

○

A

●

BUSAK+SHAMBAN K.K.
BRIDGESTONE FLOWTECHCORPORATIONHORIUCHI MACHINERY CO.,LTD.
MASUDA MANUFACTURING
CO., LTD.

●

A

●

F

○

F

●

MATUI CORPORATION▲MARUYAMA EXCELL CO.,
LTD.

△

▲

▲

▲

▲

▲

△

▲

△

▲

▲

▲

○

▲

F
●

○

○

○

○

○

○

○

A
F

○

A

●
○

●

F

●

MITSUO MFG CO., LTD.
MITSUBISHI HEAVY
INDUSTRIES, LTD.
YAMASHIN FILTERMANUFACTURING
CORPORATIONYAMAMOTO SUIATSU
KOGYOSHO CO., LTD.

AF●NIPPON VALQUA
INDUSTRIES, LTD.
NIPPON PILLAR PACKING
CO., LTD.

F▲●NITTA MOORE COMPANYNIPPON OIL PUMP CO., LTD.

●▲●

NAKAMURA KOKI CO., LTD.

NITTO KOHKI CO., LTD.

A▲▲NIKKO INDUSTRY CO., LTD.

A○

NAKANISHI SHOJI CO., LTD.

NABCO LTD.

Membership

Fittings &Piping material○

OthersPower units▲

Heat exchangers

Filters

Pressure intensifiers

Accumulators▲△

TOKIMEC INC.
TOKAI RUBBER INDUSTRIESLTD.
TOHTO HYDRAULICSCORPORATION

Servo valves△

Proportional valves△

Cartridge valves△

Measuring
instruments○

Directional valves

Water hydraulic jacks

Cylinders

Motors△Flow control valves

TOWA KIKI CO., LTD.

Positivedisplacement pumps

Company(64 in total)

Pressure control
valvesWater Hydraulic Equipment and Accessory

Products

●

○

○

○

●

5

○

●

▲

▲

▲

F

2.2

Types and specifications

2.2.1

Overview of water hydraulic components● Pumps
Structure: A water hydraulic pump used for the aqua drive system is selected either from the positive
displacement or the centrifugal, according to specifications and the use of the system. For a time being, amajority of the pumps are the positive displacement in ADS. The centrifugal pump, which has been usedwidely for transferring fluids in many industrial fields, can be used for a low-pressure drive system, due to its
low-pressure level compared to that of the positive displacement pump.
Availability: The reciprocal and the axial-piston types are available. Many manufacturers in Japan supply
the former for the pumps are popular for water jetting, and they provide the pumps in various sizes/capacities.
The latter is usually custom-made pumps, having been supplied by two overseas manufacturers and two
manufacturers in Japan. The overseas manufacturers supply a variety of standard lineups, capability ofwhich are ranging from a few L/min to 400 L/min. The vane type pumps for a low-pressure range (1.75MPa,
40 L/min) are available from manufacturers in Japan.
Displacement: The pump size should be selected such that the required flow rate and rotational speed are
obtained. The flow velocity of the inlet/outlet port is preferred to be within the recommended flow velocity
range of the pipe size.
Rotational speed: The rotational speed should be selected based on the following suction requirements.

•
•
•
•
•

Suction height of the pump
Suction port pressure (upper and lower limits)
Suction pipe size and length as well as suction filter resistance, etc.
Necessity of the boost pump
Installation method (vertical, horizontal, submerged, etc.)● Actuators
Motors
Structure: The positive displacement and centrifugal types are common for water hydraulic motors.
Availability: The axial-piston, vane, and oscillating
types are commercially available. Overseas
manufacturers have been offering axial-piston typemotors. They sell a variety of lineups with capability
ranging from a few kW to 100 kW. They offer
vane-type motors of low-speed and high-torque while
Japanese manufacturers supply low-pressure motors.
Rotational speed: When the water hydraulic motor isused at a low rotational speed, the user should select a
motor of which rotational speed is not lower than thevalue recommended by the manufacturer.
If noappropriate motor is available, combine the motor witha reduction gear.
Actuator, integrating a water
lubricated type reduction gear and a water hydraulicmotor, is also developed and commercially available;
therefore, the user has a variety of choices according to
the use.

6

Water hydraulic vane motor

Cylinders
Structure: Two cylinder types, single action and double action, are offered, based on their motion. The
user can choose the cylinder from a wide variety, such as the plunger, single-/double-rod, and telescopic
types. However, regarding the material and the seal system, clearly define the cylinder speed, frequency ofoperation, and loading requirements.
Availability: Among the water hydraulic components, cylinder is a component most available. Many
manufacturers offer water hydraulics cylinders, pressures of which are used range from the tap water level to
21 MPa. Many standard cylinders are used for a low pressure equal to 3.5 MPa or lower. However, thecustom-made cylinders can handle a pressure of 14 MPa or even higher. Similar to oil hydraulic cylinders,cylinder sizes from φ20 to φ250 are common. Cylinders for water hydraulic jacks, because of the natureof the application, are aimed for much higher pressures (14 to 21 MPa); they are widely available frommanufacturers in Japan.
Cylinder speed: The user can refer to the recommended speed range of the oil hydraulic cylinder for
selecting the water hydraulic cylinder speed. The cylinder should be equipped with a seal system of which
sliding resistance is minimum as possible.
Air vent: The air vent must be installed such that it can automatically vent the air or is accessible for humanto vent the air manually.
Buckling strength: To prevent the cylinder piston rod from being bent or buckled no matter where it isinstalled, the user needs to pay attention to the stroke length, loading direction, and installation method of thecylinder.
Loading method and excessive load: When the cylinder is used where excessive or external load can bebuilt up, the user needs to install the cylinder by a method, which takes the expected maximum load or thepressure peak into account.
Pressure amplification: The system must be equipped with a measure so that the rated pressure does not
go beyond the limit because of the difference of piston areas.

Water hydraulic cylinders● Control valves
Overview: The water hydraulic valve is classified per function to control the pressure, flow rate, and directionof the fluid. Two types, spool and poppet, are offered.
Availability: Overseas manufacturers are the main suppliers for valves that operate in a wide pressure andflow rate ranges, from the tap water level to 21 MPa or higher: pressure control valves, flow control valves,and directional valves. In addition to such valves, cartridge valves, servo valves, and proportional valves
are available; user can select those water hydraulic valves to configure an aqua drive system to serve use’s
purposes.

7

Inner passage: The inner passage of the valve main body and the manifold should have a structure suchthat the fluid does not stay still. The structure prevents the water quality change and accumulation offoreign substances caused by the residing fluid.
Electric connection of the electric operational valve: The valve has to satisfy the IEC standard in regards
to water- and damp-proof aspects.
Water and moisture proofing of the solenoid part: The user should select a safe valve according to
IEC529 such that ingress of water and dust from the outside is prevented and potential fluid leakage from thevalve to the solenoid is prevented.

Water hydraulic servovalves

Water hydraulic relief valve● Pipes and fittings
Availability: Various types of pipes, hoses, and fittings are available.
Pipe size: Select a pipe size such that the flow velocity in the respective pipeline should meet the following
recommended values:
High-pressure line: 3 to 8 m/s
Return line: 2 to 5 m/s
Suction line: 0.5 to 1 m/s
Note) Comparison of the water and oil hydraulics: The pipe friction loss and surge pressure due todifferences between the water and oil properties have been calculated, assuming the friction and oil flow
through the same line at the same flow rate. The friction loss of the water is generally a half of that of theoil hydraulics. The surge pressure of the water is generally 1.3 times greater than that of the oil due towater hammer. If the friction loss value of the water hydraulics is allowed to be equal to that of the oil, thevelocity of the water can be increased up to twice as much as the oil. However, considering the influenceof the surge pressure, it is reasonable for the flow velocity of the water to be 1.5 to 1.6 times of that of theoil. Therefore, if the upper limit of the flow velocity through the oil hydraulic pipe is assumed be 5 to 6 m/s,that through the water hydraulic pipe shall be 8 to 10 m/s.
Pipe for the high-pressure line: Despite of the velocity being within or beyond the recommended range
described above, the user should consider possible generation of the surge pressure, depending on theoperation methods, and avoid any system damage when selecting the high-pressure line.
Hose assembly: Select a hose assembly confirmed for the adaptability with the fluid, such as metal jigs andrubber hoses.
Pipe connection: Pipes must have a shape that allows no outer leakage.
connection method that requires taper screw threads or sealers.

It is not desirable to use any

Fittings for pipes and hoses: The fitting should be made of the elastic seal.
confirmed for the conformity with the fluid.

8

Select the elastic seal

Rated pressure of the fitting: Select the fitting of which rated pressure is beyond the maximum operationalpressure of the system.
Standard of the pipe: It is desirable that the selected pipe should conform to specifications described in JIS
G 3448: 2004 (Light gauge stainless steel tubes for ordinary piping) and JIS G 3459: 2004 (Stainless steel
pipes).

● Reservoirs
Availability: Various types of reservoirs are available to suit your system requirements. Stainless metal andplastic reservoirs have been widely available.
Note that preventive measures for corrosion or
bacteria/germs generation must be taken into consideration when selecting your reservoir.
Capacity: The reservoir should be capable of holding the fluid circulating in the system, as well as being able
to maintain a certain water level of the fluid that guarantees safe use of the fluid. Also, the user should
select a reservoir, taking into consideration the water temperature rise, characteristics of separation of theentrained air, and falling speed of contaminants.
Water level: The reservoir should be designed so that a water level of the fluid is higher than the pumpsuction port. Depending on the pump suction requirements, use of a pressurizing reservoir or boost pumpis preferred.
Interior surface structure: It is influential to the pump suction requirements. The circulating speed of thefluid should allow for sufficient air discharge to the reservoir. Therefore, separate the suction and returnsides of the pump with a buffer plate or other medium.
Shading: To prevent bacteria and germ growth, the structure should be designed so that no direct sunlightenters into the reservoir.
Suction line and its position: The user should use the suction line of the size with which the suction
characteristics recommended by the pump manufacturer can be obtained and install it where suchcharacteristics can be achieved. When a filter for the suction line is to be installed, its cleaning or
replacement should be taken into account.
Preventing residual contaminants: Contamination residue and deposit in the reservoir will cause rusts andhelp bacteria growth. Therefore, the reservoir structure should be designed such that no contaminants ordeposits could stay on the bottom and at corners of the reservoir, and the fluid should be completely drained.
Interior surface finishing: It should be finished such that contaminants, such as sludge, waste lint, scale,and others, can be easily removed when they enter the reservoir.
Air breather: When the reservoir is an open type, install an air breather to purify the air entering the water
reservoir, considering ambient conditions where a pump is installed. Select a filter with an appropriate
filtering grade for taking bacteria and germs in the air into consideration.

● Accessories
Availability: Standard and special-order water hydraulic accessories are offered, depending on
manufacturers and component types. Wide choices of the accessories are available to configure fluid
power systems, capabilities of which are equivalent to those of oil hydraulic systems.

Filters
Filtration: Filtration is required to maintain particle contaminants under an acceptable level, following
operational requirements such as the pressure range employed for the ADS.
Indication of thecontamination level should conform to ISO 4406.
Selection: Generally, the inner clearance in the water hydraulic components is narrower than in the oil
hydraulics. To select the filter, the user has to follow standards recommended by the manufacturer. Notethat the pressure drop occurring when the fluid passes through the filter must stay within the specified range

9

provided by the supplier.
Water supply: When the water is supplied for the initial stage or for maintaining the water level, the user
should fill the reservoir with the fluid via the filter designed exclusively for water supply. It should have theequivalent or superior accuracy, compared to other filters already supplied to the system.
Pump suction line: The user should select a filter, which matches the suction requirements provided by thepump manufacturer, and build the configuration with considerations on maintainability, such as replacementof elements. Note that the user must know some pump manufacturers do not allow filter installation to thesuction line. The user should follow the instructions provided by the manufacturer and adopt the filtration
configuration suitable for the system.

Accumulator
Structure: Accumulators, such as the diaphragm, bladder, and piston types, are available. The bladdertype accumulator is the most popular type among the water hydraulic accumulators. These water hydraulicaccumulators offers user capabilities equivalent to those for oil hydraulic systems in terms of their maximum
operational pressures and gas capacities. The accumulators can be substituted from the counterpart of theoil hydraulics in the aspects of function and performance.
Purpose of the use: The accumulators are useful for increasing operational speed of actuators, damping
circuit pulses, and absorbing impacts.

OthersHeat exchanger: When the fluid temperature exceeds the specified (refer to Section 4. 2. 3 (2), System
operation temperature) during natural cool down, the heat exchanger complying with the fluid should be used.
To prevent freezing, a heater may be used as required.
Air breather: When the reservoir is an open type, considering the ambient environmental conditions where
the pump is installed, the air breather must be installed to purify the air entering the water reservoir. For thefiltering grade, the user should also take into account the bacteria and germ flowing in the air.
Water treatment unit: Integrating the unit for sterilization, such as dechlorination, ozonation, ultraviolet
treatment, into the water hydraulic unit or pipes as required can prevent the bacteria and germ growth.
Various and effective units are commercially available for respective purpose of sterilization. The user canselect the suitable one with appropriate specification, which complies with the required water quality and thesystem operation.
Sensor: For safe operation of the system and protection of the water hydraulic components, equipping theunit with switches such as the pressure switch, the level switch, the temperature switch, etc. is desirable.

2.2.2

Specifications of water hydraulic components

Tables 2.2 to 2.7 list specifications of water hydraulic components available in Japan.
The tables are designed as a buyers’ guide for existing and potential users of water hydraulic systems.
The data aid the users to select suitable water hydraulic components of the specifications and the suppliers
listed: water hydraulic pumps, water hydraulic motors, water hydraulic cylinders/jacks, water hydraulic control
valves, water hydraulic units, accumulators, and intensifiers. The following products are subgrouped: water
hydraulic pumps, water hydraulic motors, and water hydraulic control valves.
Symbols in the tables show the availability of the components: ◎ for standard production, ○ for
special-order production, and △ for sales only. The components are corresponding to those listed in Table
2.1 with symbols (○ or △). Blank cells or cells with a hyphen indicate that precise numerical data were
not provided by the companies.

10

Table 2.2 Water hydraulic pumps

EBARA RESEARCH CO., LTD.

OthersReciprocal

Vane

Radial piston

Company

Axial piston

Type
Displacement volume
3(cm /rev)

Operationalpressure
Max.
(MPa)

16

△
◎

OSAKA JACK CO., LTD.

Min.

Max.

3.3

225

15

28
16

Flow rateMax.
(L/min)Rotational
speed
Max.
-1
(min )

430

2,000

24

1,800

KAYABA INDUSTRY CO., LTD.

○

21

KITAMURA SHOKO CO., LTD.

△

16

3.3

225

430

2,000

50

2.3

438

228

3,600

△

80

△
KOSHIN SEIKOSHO, LTD.

◎

45

SUGINO MACHINE LTD.

◎

250
◎

TAIYO, LTD.
DANFOSS K.K.

1,500

0.7

360

511

10 - 16280

3.6 - 144

1,800

△

80

4

80

7.2 - 144

1,800

40

1,750

1.4 - 1.75△△△

MARUYAMA EXCELL CO., LTD.
MITSUBISHI HEAVY INDUSTRIES,LTD.
YAMAMOTO SUIATSU KOGYOSHOCO., LTD.

4,100

△

TOWA KIKI CO., LTD.
TOHTO HYDRAULICSCORPORATION

15

○
◎

10 - 16

2

80

144

1,800

50

1.1

444

275

3,600

21

23

60

100

1,800

6.6 - 198

1.8

186

11.2

300

Table 2.3 Water hydraulic motors

EBARA RESEARCH CO., LTD.

OthersOscillating

Vane

Radial piston

Company

Axial piston

Type
Displacement
volumeOperationa(cm3/rev)
l pressure
Max.
(MPa)

16

△
○

Min.

Max.

3.1

225

2

Rotational speedMax.
(min-1)

Flow rateMax.
(L/min)
Min.

Max.

430

500

2,000 - 4,000

12

500

1,500

KITAMURA SHOKO CO., LTD.

△

16

4.6

225

430

500

2,000 - 4,000

DANFOSS K.K.

△

14

4

12.5

37.5

300

3,000 - 4,000

36

15

200

37.5

300

3,000 - 4,000

36

15

200

△
TOHTO HYDRAULICSCORPORATIONEBARA RESEARCH CO., LTD.

5

160

14

△
△

4

5

12.5
160

11

Table 2.4 Water hydraulic cylinders/water hydraulic Jacks

Jacks

Company

CylinderType
Operationalpressure
Max.
(MPa)

Cylinder bore
(mm)

Stroke
Max.
(mm)

2,500

ARAKI IRON WORKS LTD.

○14

40 - 200

SMC CORPORATION○

3.5 - 1440 - 250

EBARA RESEARCH CO., LTD.

△2 - 1420 - 300

1554, 64◎OSAKA JACK CO., LTD.
KAYABA INDUSTRY CO., LTD.

○

Tap Water
Pressure

KITAMURA SHOKO CO., LTD.

○
△

14
○

SANMAX CORPORATION◎○JAPAN PNEUMATICS CO., LTD.

◎
○
◎
○

Speed
(m/s)

Port size

1/8 - 3/4
0.01 - 0.3

Rc1/8 - 1/2

700
1,280

G1/2

50 - 100

450

Rc1/2

14

50 - 130

2,000

Rc1/2

Max. 2.5

25 - 150

10,0000.1

Rc1/8 - 1/2

Max.

20

40 - 80

1,000

0.1

Rc1/8 - 1/2

Max. 720, 25, 30

300

0.01 - 0.3

Rc1/8

Max. 35

20, 25, 35

200.01 - 0.05

Rc1/8

3,500

TAIYO, LTD.

○

0.2 - 1420 - 250

TAIYO INTERNATIONALCORPORATION△

1

40 - 160

DANFOSS K.K.

△

14

25 - 63

TOWA KIKI CO., LTD.

◎

0.1 - 0.7, 0.1 - 1

40, 50, 63, 80, 100△Max. 2125 - 160

TOHTO HYDRAULICSCORPORATION△

Max. 1632, 40, 50, 63, 80,
100

NABCO LTD.

○

Max. 2128, 40, 50, etc.

NIPPON VALQUA INDUSTRIES,LTD.

○HORIUCHI MACHINERY CO., LTD.

○MITSUBISHI HEAVY INDUSTRIES,LTD.
YAMAMOTO SUIATSU KOGYOSYO
CO., LTD.

○○

Tap waterpressure
Tap waterpressure - 14MPa

1/8-3/8
0.2
1,500

G1/8, 1/4, 3/8
Rc1/8 - 3/8

2,000

30 - 100300

0.002 - 0.1

Rc1/2

25 - 400

4,000

0.008 - 0.3

1/8 - 2

10

125

2,200

0.2

Rc3/8

Up to 21

240

1,000

4

Rc11/412

Table 2.5 Water hydraulic control valves (1/3)
Type

Rated
pressure(MPa)(14 - 21)◎

IHARA SCIENCE CORPORATION○SMC CORPORATION◎EBARA RESEARCH CO., LTD.

5

1/8, 1/4

1.5―

1/8 - 2

14
○
○

△
△
△
△
△
△
△
△
◎
〇

TAIYO, LTD.

14

80

14

80

31.5

30

3/8

31.5

30

3/8

31.5

30

3/8

31.5

30

3/8

31.5

30

3/8

31.5

30

3/8

31.5

30

3/8

35

275

3/8 - 11/4

(14 - 21)

1,500

Tap waterpressure

20

0.01 - 1.72△

1/2
1/8 - 1△

(Tap waterpressure,
14 - 21)

―

1/4

△

0.8 - 4―

1/4 - 2△0 - 10―

1/4 - 1 /2

0 - 25△DANFOSS K.K.

Tap waterpressure

14△

TAIYO INTERNATIONALCORPORATION

1/4, 3/8, 1/2

14△SUGINO MACHINE LTD.

Port size

14△△

KITAMURA SHOKO CO., LTD.

Flow rate(L/min)Others

Proportional

Servo

Cartridge

Check

Direction

Solenoid-operated

Orifice

Reducing

ReliefCompany

Flow rate

Flow control

Pressure

△
△
△
△
△
△

13

1

3/8 - 1/2

2.5 - 1430/60/120

G3/8, G1/2, G3/4

14

30

G3/8

14

30

G3/8

16 (21)30/60/120/150

G3/8, G1/2, G3/4, G1

30

30/60

G3/8, G1/2

14

30

G3/8

Table 2.5 Water hydraulic control valves (2/3)
Type

TOWA KIKI CO., LTD.

(< 3.5)20 (m /h)

15A - 50A△(< 3.5)60

10A - 25A(> 21)

25

1/4, 3/8△

0.069 - 2―

1/8 - 1/2△

10

TOKIMEC INC.

3/8 - 2

1/4 - 11/2

0.02 - 1

120

3/8 - 1△

1.6 - 10Max. 560

1/8 - 2△

1

10

1/8, 1/4

△

14

―

1/8

△

10

―

1/4 - 3/4

2.5 - 1420 - 120

3/8 - 3/4

△

△

34.5

△

40

11.4 208.2
17.1 378.5
―

△

14

30

3/8

5, 14

25 - 120

3/8, 1/2

△

34.5

―

1/8 - 1△30

30, 603/8, 1/2

△

40

34.5

△

△

1/8 - 1
1/8 - 1
1/8 - 2

1/4 - 3/4

(14 - 21)200

1/8 - 1

14

30

3/8

14

60

1/2

14

30

3/8

Max. 21

Up to 200

Various sizes

32

Up to 25

DN3, 6, 10

32

Up to 15

DN3, 6

○

―

320

○

21

0.3

○

14

5

○

14

40

△
△
○
○
○
△
△
MOOG JAPAN LTD.

1/4
30.02 - 0.55△

NABCO LTD.

Port size△△

TOYOOKI KOGYO CO., LTD.

Flow rate(L/min)0.03 - 0.7△△

TOHTO HYDRAULICSCORPORATION

Rated
pressure(MPa)
Others

Proportional

Servo

Cartridge

Check

Direction

Solenoid-operated

Orifice

Reducing

ReliefCompany

Flow rate

Flow control

Pressure

14

Table 2.5 Water hydraulic control valves (3/3)
Type

HIROSE VALVE INDUSTRY CO.,
LTD.

Rated
pressure(MPa)

Flow rate(L/min)Port size(> 21)

600

1/4 - 11/2

21

350 4000

8 - 80A

Others

Proportional

Servo

Cartridge

Check

Solenoid-operated

Orifice

Reducing

ReliefCompany

Flow control

Pressure Flow rate Direction◎◎

MARUYAMA EXCELL CO., LTD.

△1 - 50275

3/8 - 11/4

MITSUBISHI HEAVY INDUSTRIES,
LTD.

○

21

60

1/2

21

40

3/8

21

60

3/8

21

100

3/8

60

11

3/8

(> 21)

11

3/8(> 21)

11

3/8(> 21)

11

3/8(> 21)

11

3/8(> 21)

11

3/8

○
○
○
YAMAMOTO SUIATSU KOGYOSYO
CO., LTD.

◎
○
○
○
○
○

Table 2.6 Water hydraulic units

EBARA RESEARCH CO., LTD○ △KITAMURA SHOKO CO., LTD.

○ △JAPAN PNEUMATICS CO., LTD.

△TAIYO INTERNATIONAL CORPORATION △Operationalpressure
Max.
(MPa)

Pump
displacement
volume3(cm /rev)Tank
capacity(L)

Motor(kW x poles)

30

200

15 x 4

OthersReciprocal

Vane

Radial piston

Availability

Company

Axial piston

Pump Type

14
14
○

3.5

2

0 - 0.9○

14

4/6.3/10/12.5

27/60

14

25

100

50

1.1 - 444

18

16

DANFOSS K.K.

△ ◎TOWA KIKI CO., LTD.

○

0.1 - 10△

0.1 - 1TOYOOKI KOGYO CO., LTD.

○MARUYAMA EXCELL CO., LTD.

○MITSUBISHI HEAVY INDUSTRIES, LTD.

○ ○

△

15

400

11 x 6
0.4 - 45 x 4Ps
0.4 - 45 x 6Ps
15

Table 2.7 Accumulators/pressure intensifiers
Type

NOK CORPORATIONKITAMURA SHOKO CO., LTD.

Volume(L)

Flow rate(L/min)Port size◎

0.44 - 0.83

0.5 - 20―G1/2・3/4, R3/4

◎

6.85

0.3, 0.5

―

Rc3/8

◎

3.4 - 34.3

1 - 160―

G3/4 - G3△

2.94 - 34.3

1 - 230―

Rc3/4, flange fitting△

5.88 - 20.6

0.1 - 160―

Rc1/4, 3/4, flange fitting(14 - 21)―10

1 - 2.5

20―

1/2 - 1

1 - 20―15

1/2 - 1(14 - 21)20―

(14 - 21)

―

15

◎

5 - 25

0.1 - 160―

Rc3/8・3/4, M42 - 75

◎

0.95

2.4

―

R1/2

◎

15 - 50

0.1 - 160―

Rc3/8・3/4, M42 - 90△

7 - 35

0.1 - 2―

Rc1/2 - 3/4

2.5

UNF9/16

PressureintensifiersRated pressure(MPa)

Accumulator

Company○
SANMAX CORPORATION○○

SUGINO MACHINE LTD.

◎◎NIPPON ACCUMULATOR CO., LTD.

MARUYAMA EXCELL CO., LTD.
YAMAMOTO SUIATSU KOGYOSYO CO.,
LTD.

2.3

○

500

Materials for components and systems

In order to design an aqua drive system and make the system reliable, the designer needs to know aboutmaterials used in the system devices and components including pipes, fittings, and accessories. Materials
used to configure the system are mostly anti-corrosive alloys (stainless steels, aluminum-base alloys,
copper-base alloys, nickel-base alloys), resins, and ceramics. Surface treatments are applied to improvesurface properties of the devices and components against corrosion, wear, and erosion. Depending on typeand location of the material to be used, appropriate surface treatments shall be implemented (e. g. metal
plating, vapor deposition, or thermal spraying). The materials used for the treatments vary: metals, plastics,
and ceramics to name a few. Carbon steels are sometimes used for a base metal due to cost and material
availability concerns.
For seals, the following materials are commonly used for their stability to water.
(1) Elastomer (rubber): NBR, HNBR, FKM (FPM), etc.
(2) Thermal plastic elastomer: Polyurethane, etc.
(3) Resin: PTFE with filling materials, super large molecular weight PE, etc.
In addition to the above materials, metals can be used for seals for fixed components. When selecting
seals for moving components including pumps, motors, or cylinders, seal material properties, for sliding anddurability in particular, are important elements to consider.
Table 2.8 and Table 2.9 list materials used for water hydraulic components in Japan and rubber materials
used for seals, respectively. The data are obtained by questionnaires to water hydraulic component
suppliers shown in Section 2.1 and studying their product catalogue.

16

Table 2.8 Materials used for water hydraulic components and devices

Machinery
Pumps
MotorsCylindersMultipurpose control
valves
Proportional/servo
valves
Accumulator
Pressure intensifiers
Measuring
instruments/apparatus
Filters
Water hydraulic Units
Piping/Fittings
Hoses
Note 1)
Note 2)
Note 3)Note 4)Note 5)

Stainless
steel
○
○
○
○

Iron
Carbonsteel

Non-iron
Cast iron Aluminum

Brass

BronzeResin

Ceramics

○
○

○

○
○
○

○

○

○

○

○
○

Rubber

○
○
○

○

○
○
○
○

○
○

○

Stainless steel includes SUS304 and SCS13. The metal may be treated with hard chrome plating.
Carbon steel shall be plated or coated with epoxy resin to improve its anti-rust property.
Aluminum shall be treated with special alumite.
Bronze includes AIBC.
Resin includes PP resin (accumulator), Nylon, Polyolefin (hoses).

Table 2.9 Rubber materials used for seals/packings in water hydraulic components and devices
Machinery

Cylinders
Solenoid directional valve
Accumulators
Water hydraulicequipment in general
Symbols)

Places for Use

NBR,
HNBR

Packing
Diaphragms, O-Rings
Bladders, seals
Oil seals
O-Rings, gaskets

○
○
○
○
○

NBR: Nitrile Rubber. HNBR: Hydrogenated Nitrile Rubber.
Rubber. FKM: Fluorine Rubber. IIR: Butyl Rubber

17

VMQ

EPDM

FKM

IIR

○
○
○
○

○

VMQ: Silicone Rubber.

EPDM: Ethylene Propylene

Chapter 3 Water Quality Control for Aqua Drive System
3.1

Water quality

The tap water standard (Ordinance No. 69 of Ministry of Health and Welfare, 1992) defines 29
health-related requirements and 17 characteristic elements for tap water. Of them, this chapter focuses onfive elements that may affect ADS operation: - pH, chlorine ions, hardness, evaporation residue, and generalbacteria.

3.2

Water quality evaluation test

A case study was conducted to analyze the following parameters that affect the working water quality in
ADS: (1) Water temperature, (2) continuous system operation and suspension, (3) ambient temperature, and(4) filter mesh size in the air breather.

3.2.1

Test apparatus and conditions

Figure 3.1 is a view of the water quality test unit. Figure 3.2 is the circuit diagram of the test apparatus.
Before starting the test, the apparatus was flushed sufficiently. During the test, the water was circulated
without additional water supply into the system. The water used was tap water supplied around the Tokyo
metropolitan area. The monitoring points and items were as follows.
[Monitoring points][Monitoring items]

Inside of the reservoir, just before the return filter, and the mid way of the connecting
line of the accumulator
pH value, chloride ion, hardness, residue of evaporation, and general bacteria
Closed tank: 100 L
Installed within a room sothat the tank was notdirectly exposed to sunlight
On/off valve

14 MPaM

Triplexplunger pump
21 L/minFig 3.1 Water quality test unit

Fig 3.2

Circuit diagram of the test apparatus

Pressure (MPa)60sTime (s)Fig. 3.3 Load cycles (Experimental value)183.2.2

Test result

Generalbacteria (cell/mL)
一般細菌(個/mL)

The test system was operated at a constant water temperature of 30 to 32 ℃ with a load of 14 MPa for 30
seconds and then with almost no load (1.5 MPa) for 30 seconds, as shown in Fig. 3.3. The test wascontinued for approximately eight hours a day during the test period of 259 days (total operating time: 1,592
hours). Figure 3.4 shows the test results.

60000
タンク
Tank
Filter
フィルタ

50000
40000

Ａｃｃ．

30000
20000
10000
0
0

400

800

1200

1600

9

pH値

pH

8
7
タンク
Tank
フィルタ
Filter

6

Acc.
5
0

400

800

1200

1600

Evaporation
residue (mg/L)
蒸発残留物(mg/L)

Operatingtime (h)
運転時間(h)
500
400

Tank
タンク
Filter
フィルタ

300

Ａｃｃ.

200
100
0
0

Operatingtime (h)
運転時間(h)

800

1200

1600

Operatingtime (h)
運転時間(h)200

250

Clorineion (mg/L)
塩素イオン(mg/L)

300

Hardness(mg/L)
硬度(mg/L)

400

タンク
Tank
Filter
フィルタ

200

Ａｃｃ．

150
100
50
0

160

タンク
Tank
Filter
フィルタ

120

Ａｃｃ．
80
40
0

0

400

800

1200

1600

0

Operatingtime
運転時間(h)400

800

Operatingtime
運転時間(h)Fig. 3.4 Water quality evaluation results

19

1200

1600

As shown in Fig. 3.4, the levels of pH, chlorine ions, hardness, and evaporation residue remained
considerably lower than those defined by the tap water standard. They showed no major variations or
differences among the monitoring points. According to the sets of sampling data, excluding the forth one,the bacteria count increased in the initial phase (120 hours from the test start to the 15th day) and thendecreased due to starvation and death, regardless of the sampling points.
The same test was conducted at a constant water temperature of 40 to 42 ℃ for 110 days (total operatingtime: 670 hours,) and similar results were obtained.

General bacteria (cell/mL)

General bacteria (Count/mL)

The system water was sampled at the 15th day, which confirmed a growth of general bacteria. To checkthe bacteria growth rate in the initial phase, the system was intermittently operated, similarly as shown in Fig.
3.3, at a constant water temperature of 40 ℃ around-the-clock for 20 days. Figure 3.5 shows the bacteria
count in the water sampled daily. For reference, the bacteria count in a stopped water hydraulic system isalso indicated, the water temperature in which was kept at 40 ℃. The figure shows that the bacteria growth
was rapid in the initial phase in both cases. The growth in the running system takes place in an earlier
stage than in the reference case. This phenomenon is supposedly associated with the points where thewater was sampled. It was sampled from the tank bottom; it is assumed that the spread of bacteria in thetank took more time in the stopped system. The bacteria growth in the stopped system had a higher peakthan that in the running system.

35000
30000
25000

Operating
Stopped

20000
15000
10000
5000
0
1

2

3

4

5

6

7

8

9 10 11 12 13 14 15 16 17 18 19 20

Day

Fig. 3.5

Bacteria count in the initial test phase

Influence of the ambient room temperature and the filter mesh size in the air breather for the bacteria
growth was examined and Fig. 3.6 shows the test results. Using a 40-µm-mesh filter, Tests 1 and 2 werecarried out in a cold season (February 26 to March 17 in 2002) and in a hot season (August 12 to September
4 in 2003), respectively. Test 3 was conducted from October 27 to November 18 in 2003, using a 1-µm
mesh filter. In all the tests, the system was operated at a constant water temperature of 40 ℃.
As shown in the figure, the bacteria count started to rise just after the test start and reached at the
maximum level in a day or two. Then, the count declined to below 4,000 cells/mL in ten days and remainedat almost the same level. The bacteria growth in Test 3 had a peak lower than that in Test 2 but a slightly
higher than that in Test 1. Considering that Test 1 was conducted in the winter (room temp.: approx. 15 ℃)
while Test 2 was in the summer (approx. 30 ℃), Figure 3.6 suggests that the room temperature is a more
influential factor on the bacteria growth than the filter mesh size.

20

200000
180000General bacteria (Count/ｍL)

160000Experiment 1 (40µm, Room temp. 15℃)

140000120000Experiment 2 (40µm, Room temp. 30℃)

100000Experiment 3 (1µm, Room temp. 21℃)
80000
60000
40000
20000
0
1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

Day

Fig. 3.6

3.3

Influence of the room temperature and the mesh size of the air breather on bacteria growth

Guidelines for water quality control

ADS uses tap water, which may be affected by algae and bacteria growth or pH variations, depending on
the service conditions. Table 3.1 describes how the water quality change in the system affects the systemcomponents. To prevent potential risks associated with those factors, the water quality control is required
as outlined in Table 3.2.
Table 3.1
FactorBacteria and algae growth
Chlorine ions
Water pH

Influence of water quality change on system components
Potential influence on the components- Solenoid-operated directional valve/relief valve: spool malfunction- Strainer: clogged filter element- Cylinder: deteriorated sealing performance- Pump/motor: clogged drain path in the casing
Causes crack on stainless steel with stress corrosion.
A low water pH opts to corrode metals more severely.

Table 3.2

Control factor and reference value
1)

Control element and description
Reference value
pH
A lower pH value may result in corrosion.
6.5 to 8.5
A higher chlorine level causes corrosion of stainless steel
Chlorine ions
200 mg/L or less(crevice corrosion).
Higher hardness increases a risk of calcium deposition,
300 mg/L or lessHardnesswhich results in corrosion.
The residue mainly contains salt and organic constituents
Evaporationsuch as calcium, magnesium, and silicate, which cause 500 mg/L or lessresidue
metal corrosion in the piping.
GeneralCounts of both bacteria and other microorganisms per 1
100 cells/mL or lessbacteria
ml of water. Used as a measure of water contamination.
1) The values for pH and chlorine ions are based on Nessie standards of Danfoss K. K.; those forhardness, evaporation residue, and general bacteria are on the water quality standard defined by
the Ordinance No. 69 of Ministry of Health and Welfare in Japan.

21

Maintenance method: It is preferable to have a filtering system that removes bacteria and othermicroorganisms from the working water. Figure 3.7 describes removal of contaminants of different sizes in
the water.

Contaminant

Size

Germs

VirusesOrganic

Microorganisms

Dirt

Silica colloid

Inorganic
Rust

Electronic microscope

Observation
methodVisual

Optical microscope

Microfilter

RemovalmethodFilter

Hollow fiber

Fig. 3.7

Removal of contaminants of different sizes

Sources) Shoji Kubota, “Atarashii mizuno kisochishiki” (in Japanese, the title
translated as “Basics of new water”), Ohmsha Ltd. (ISBN:
4-274-11989-0)
Shoji Kubota and Ichiko Nohara, “Jousui, seisui, kassui no
kisochishiki” (in Japanese, the title translated as “Basics of purified,treated and activated waters”), Ohmsha Ltd. (ISBN:
4-274-02303-6)

22

Chapter 4 Operating Aqua Drive System
4.1

High-speed operation

To clarify problems and establish guidelines for putting an aqua drive system into practical applications, anexperiment was conducted to simulate injection and dwelling processes of the conventional oil hydraulicprecision molding machine with ADS. A target speed of a water hydraulic cylinder used in the model was
set to 4 m/s, which is equivalent to a general cylinder speed for oil hydraulic precision molding machines thatrun in a middle pressure range. Use of tap water as the system fluid could make the cylinder exceed thetarget speed while it could reveal various problems unique to ADS. The experiment focused on verifying
rapidity of the water hydraulic cylinder and pressure behavior on the water hydraulic components whenmodel is run in a circuit, consisting of an accumulator as an auxiliary water pressure source and logic valves.

4.1.1

Experimental apparatus and method

Figures 4.1 and 4.2 show a circuit diagram of the experimental apparatus and the apparatus images,
respectively.
The apparatus consists of a water hydraulic unit, a water hydraulic cylinder, and a load simulator unit. In
3the aqua drive unit, a fixed capacity pump of 30 cm /rev is driven by a 15-kW inverter motor to supply water-1
at 43.5 L/min (when running at 1,450 min ). The rated pressure of the circuit was 14 MPa. On the pumpdischarge side, a high-speed operation circuit is connected, which comprises of high-capacity logic valves
and an accumulator. The water hydraulic cylinder was used for performing the injection and dwelling
processes. The solenoid valve circuit was used for retracting the cylinder. The water hydraulic cylinder,
designed as an injection cylinder (cylinder inner diameter: 40mm, rod diameter: 22 mm, and stroke: 250 mm),was connected to that in the same size of the oil hydraulic cylinder, which simulates the load. The load
simulator, consisting of an oil hydraulic cylinder and oil hydraulic unload valve, controls loading andunloading to simulate loads of the precision molding machine.

Valve unit
Cylinder displacement x

Loadsimulator

Water
hydrauliccylinderAqua drive unit
Water hydraulicpump unit
InverterFig 4.1

Circuit diagram of the experimental apparatus

23

(a)

Overview(b) Load simulator(Water hydraulic and oil hydraulic cylinders)(c) Valve unit
(Logic valve and accumulator)
Fig. 4.2(b) Dummy load
(Unloading relief valve)

Appearances of the experimental apparatus

Experimental parameters and measurement items are as follows.
(1)

Experimental parameters (See Fig. 4.1)
・ Discharge pressure of Pump 3: Set it with Relief valve 10 as an accumulated pressure of
Accumulator 13.
・ Loading pressure of loading cylinder 29: Set it with Relief valve 31.
・ Pilot flow rate of Logic valve 15: Set it by replacing a Fixed-orifice 14 of Pilot valve 12.

(2)

Measurement items (See Fig. 4.1)
・ Pressures
Pump discharge pressure: P8A
Pressures of the injection cylinder rod side and the head side: P28C and P28D
Pilot pressure of the logic valve: P14A and P14B
Pressure of the loading relief valve: P30A
・ Cylinder displacement: x

24

Three processes described in Fig. 4.3 are defined as one operation cycle.

Dwelling

Cylinder displacement

Injection

Retract
The cylinder is retracted
by closing the logic valve
and switching thedirection switch valve.

Loading pressure of 3 MPaor higher is held for 0.5 sec.

The unloading valve isswitched to the state ofloading.

Time
Fig. 4.3 Operation pattern

4.1.2

Experimental conditions
Experimental conditions are as follows.
・ Pump flow: 22.5 L/min
・ Supply pressure: 12MPa, 13MPa, 14MPa
・ Accumulator pressure: 70 % of the supply pressure
・ Relief pressure in the load simulator: 15.5 MPa
・ Orifice diameter of the pilot in the logic valve: 1.0 mm, 1.5 mm, 2.0mm

4.5

Cylinderspeedm/sm/s
シリンダ速度(1)

Experimental results

4
3.5
3
2.5
2
11.5

12

12.5

13

13.5

14

14.5

Supplypressure
供給圧力
MPa MPa
絞り直径φ1.5mm
絞り直径φ2.0mm●: Orifice dia. φ 絞り直径φ1.0mm
1.0 mm, ▲: Orificedia. φ 1.5 mm,■: Orifice dia. φ 2.0 mm

Fig. 4.4

Cylinder speed vs. supply pressure changed
with orifice diameter of the pilot in the logic valve

25

(2)

Result A

Figure 4.4 shows the effect of supply pressure and the orifice diameter of the pilot in the logic valve. The
figure shows that the operational speed increases with the orifice diameter. When the orifice diameter is 2.0mm and the supply pressure is 14 MPa in particular, the cylinder moves 4.14 m/s, which exceeds the target
value. The cylinder speed, however, saturates when the orifice diameter is 1.5 mm or larger. The result
indicates that combination of the accumulator and the logic valves is effective to accelerate the cylinder
movement in ADS.

20
18
16
14
12
10
8
6
4
2
0
-2

Cylinder displacement
シリンダ変位
mm mm

250
200
150
100
50
0
0

0.5

1

1.5

2

圧力 MPaMPa
Pressure

Figure 4.5-1 shows changes of the cylinder displacement and pressures at each measured point in thesystem when the supply pressure is at 14 MPa and the orifice diameter is 1.5 mm. Figure 4.5-2 showsdetails of the results, focusing the injection and dwelling processes. The water hydraulic cylinder speed
drastically drops at the cylinder end in Fig. 4.5-2 due to the cushion effect of the oil hydraulic cylinder. This
result suggests that, to simulate loads of the precision molding machine more precisely, loads must be
applied with an unloading valve of high response just before the cylinder end. Note that the pressure riseon the cylinder head and rod sides immediately after the cylinder movement can be suppressed by opening
the rod-side logic valve earlier than the cylinder movement.

x
P30A
P8A
P28D
P28C
P14A
P14B

2.5

時間 s sTime

Cylinder displacement and pressure vs. time
(Supply pressure: 14 MPa. Orifice diameter: 1.5 mm)

250
200
150
100
50
0
0.25

0.3

0.35

0.4

0.45

0.5

20
18
16
14
12
10
8
6
4
2
0
-2
0.55

圧力 MPaMPa
Pressure

Cylinderシリンダ変位
displacementmmmm

Fig. 4.5-1

Time
時間 s sFig. 4.5-2

Cylinder displacement and pressure vs. time
(Supply pressure: 14 MPa. Orifice diameter: 1.5 mm.
Magnified: the time from 0.25 to 0.55 seconds)

26

x
P30A
P8A
P28D
P28C
P14A
P14B

(3)

Pressure rise estimation

The surge pressure upon cylinder stop in ADS is generally higher than that in oil hydraulic systems due tolow compressibility of water. The surge pressure, which is one of serious issues for the ADS applications,depends on the cylinder speed; thus, it should be estimated as a guideline for designing piping. When the
supply pressure is p , the water density is ρ , and the maximum cylinder speed of the injection process is ν ,a theoretical maximum surge pressure p max is given by the following equation:pmax = p + ρ av ,where a is the velocity of pressure wave and is defined as a = K / ρ with K as the bulk module of
the water.

Surge
pressure upon cylinder stop
シリンダ停止時ヘッド側サージ圧力
on the headMPaside MPa

Figure 4.6 shows comparisons of the maximum surge pressures: those theoretically calculated using theequation above and those measured in the experiment by stopping the cylinder running at a high speed.
The data shows that the all theoretically obtained surge pressures are higher than those measured in theexperiment. If the system designer can know the maximum speed of the cylinder in the design phase, themaximum surge pressure in the real system can be estimated. Note that the measured surge pressures
were lower than the estimated because the cylinder decelerated in the cushion mechanism before it stopped.

22
Theoretical(φ1.0)
理論値(φ1.0)

20
Theoretical(φ1.5)
理論値(φ1.5)

18

Theoretical(φ2.0)
理論値(φ2.0)
Experimental(φ1.0)
実験値(φ1.0)

16

Experimental(φ1.5)
実験値(φ1.5)

14

Experimental(φ2.0)
実験値(φ2.0)

12
12

12.5

13
13.5
Supplypressure
供給圧力
MPaMPaFig. 4.6

14

Comparison of the theoretical surge pressurespmax

and the experimental surge pressures(4)

Result B

To explore possibility for rapid cylinder speed, changes in the cylinder speed were measured using two
types of logic valves; geometries of the main valves are different to each other. Figure 4.7 indicates thewater hydraulic logic valve used in the experiment, showing the circuit diagram of the valve unit in Fig. 4.1.
To identify the valves, the valve described in Fig. 4.1 is called Form A while the one described in Fig. 4.7 iscalled Form B.
These valves have a different geometry of the logic main valve; the valve opening-flow rate characteristics
are different. Form B has a higher tolerance to the opening-flow rate changes; it was expected to achieve
high-speed cylinder operation.
Figure 4.8 shows a comparison of the two valves at high-speed operation. The result indicates that thecylinder speed of Form B exceeds the performance of Form A overall. In addition, the surge pressure uponcylinder stop was also increased.

27

Valve unit

Fig. 4.7

Circuit diagram of a water hydraulic logic valve, Form B

Cylinderspeedm/sm/s
シリンダ速度

5.0
4.5
Form A, φ1.0
Form A, φ1.5
Form A, φ2.0
Form B, φ1.0
Form B, φ1.5
Form B, φ2.0

4.0
3.5
3.0
2.5
2.0
12

13

14

Supplypressure
供給圧力
MPa MPa

サージ圧力
MPaMPaSurge
pressure

21
20
19

Form A, φ1.0
Form A, φ1.5
Form A, φ2.0
Form B, φ1.0
Form B, φ1.5
Form B, φ2.0

18
17
16
15
14
13
12
12

13

14

Supplypressure
供給圧力
MPa MPa
Fig. 4.8(5)

Cylinder speed and the surge pressureof the valves Form A and B

Conclusions
1. Combination of high-capacity logic valves and an accumulator achieved the cylinder speed of 4 m/s orhigher. The speed is equivalent to normal cylinder speed in the oil hydraulic precision molding
machines that run in a middle pressure range.
2. The surge pressure upon stop of the operating water hydraulic cylinder (cushion area) can be
estimated.

28

4.1.3(1)

Simulation

Simulation model

A simulation analysis was conducted to investigate a relation among the orifice diameter of the pilot in the
logic valve, 14a, the cylinder speed, and the surge pressure. Figure 4.9 shows a diagram of the circuit to beanalyzed. The simulation was conducted by deriving basic equations of the main components configuring
the circuit.
Considerations for deriving the basic equations of the main components were as follows.

P
28C
P
30A

PH

PH

・
・
・
・
・
・
・

Constant flow rate of the pump
Override characteristics of the relief valve
Polytrophic change of the gas in the accumulator
Compressibility of the fluid in the cylinder chambers and changes of the cylinder chamber
volumes
Equations for cylinder motion including inertia, viscosity, and friction force
Dynamic of piping
Assumption that the cushion force is proportional to the cylinder speed
Override characteristics when the relief valve is open.
The flow rate passing through the relief valve, thinking the relief valve as the orifice when closed.
Equation of the poppet motion and flow rate characteristics, as well as water compressibility
Effect of the orifice of the pilot, 14A

Logic
valve
ロジック弁

Logic
valve
ロジック弁

15
B

15
A

P
28D

PH

・
・
・
・

31

Orifice
絞り

32

14
A

M
28

シリンダ変位
Cylinderx
displacement x

29

33

13

Fig. 4.9

Circuit diagram for the simulation analysis

29

(2)

Results and considerations

Figure 4.10 shows a result of the simulation analysis when the logic valve, Form A, was used at a supply
pressure of 14 MPa and the orifice diameter was 1.5 mm.
The figure on the top shows the piston displacement of the water hydraulic cylinder, x, while the figure on
the bottom shows the pressures of the water hydraulic cylinder, on the head, p28D, and on the rod side, p28C,
as well as the pressure of the oil hydraulic cylinder on the head of the load simulator, p30A. At t = 0, the logic
valves, 15A and 15B, are opened. Right upon their opening, the piston displacement x starts to increase.
When x reaches 230 mm, the cushion mechanism of the oil hydraulic cylinder starts working. It takes
approximately 0.055 second until the cushion starts working. From the traveling distance in the period oftime, which is 230 mm (full stroke – cushion = 250 – 20), the mean speed, 4.18 m/s is derived. The surge
pressure upon cylinder stop, therefore, is 20.3 MPa.

x (m)

0.3
0.2
0.1
0

p (MPa)

20

p28D

10

p28C

p30A

0
0

0.02

0.04

0.06

0.08

t (s)
Fig. 4.10

Simulation result (Form A at a supply pressure of 14 MPa,
with the orifice of 14 A, φ 1.5 mm)

The simulated cylinder speeds with the orifice diameter of the pilot, 14A, is 1.0, 1.5, and 2.0 mm are shownin Figs. 4.11 (Form A) and 4.12 (Form B). The surge pressures simulated upon cylinder stop are shown in
Figs. 4.13 (Form A) and 4.14 (Form B). Symbols, ○,◇, and □ in the figures, are the experimental results
while lines are the simulation results. Intensity of the cushion was the same for the both valve types.
If the supply pressures are the same, the cylinder speeds and the surge pressures increase with the orifice
diameters in the experiment. The tendency was also observed in the simulation. The higher the supply
pressure, in the experiment, the higher the cylinder speed and the surge pressure became when the orifice
diameter was the same. The same tendency was also confirmed in the simulation. In contrast, differences
observed between the results of the experiment and the simulation, shown in Fig. 4.14, are left for a future
work.

30

6

6
Orifice
絞り14A
14A(Form(Form B)B) (mm)
(mm)

○ 2.0
◇ 1.5
□ 1.0

5

Cylinderspeed(m/s)
m/s
シリンダ速度Cylinderspeed(m/s)
m/s
シリンダ速度Orifice
14A(Form(FormA)
A)(mm)(mm)
絞り 14A

4

3

2

5

4

3

2

12

13
14
(MPa) MPa
供給圧力
Supplypressure

12

13

14

(MPa) MPa
供給圧力
Supplypressure

Fig. 4.11 Mean cylinder speed (Form A)

Fig. 4.12 Mean cylinder speed (Form B)

25

25
Orifice
14A(Form (mm)B) (mm)
絞り 14A(FromB)

Orifice
14A(Form(FormA)A)(mm)(mm)
絞り 14A

○ 2.0
◇ 1.5
□ 1.0

20

(MPa)MPa
サージ圧
Surge
pressure(MPa)MPa
サージ圧
Surge
pressure

○ 2.0
◇ 1.5
□ 1.0

15

10

Fig. 4.13

○ 2.0
◇ 1.5
□ 1.0
20

15

10

12

13
14
供給圧力
(MPa) MPa
Supplypressure

12

13

14

供給圧力
(MPa) MPa
Supplypressure

Surge pressure upon cylinder stop
(Form A)

31

Fig. 4.14

Surge pressure upon cylinder stop
(Form B)

4.2

ADS operational guideline

4.2.1

Pressure loss and flow rate

Water is a fluid of low viscosity, and its pressure loss in lines is much less compared to that of oil.
Therefore, the following can be some of the advantages that water can provide as a fluid.
Inner diameter of fluid lines can be smaller.
Energy loss is minimized even when the actuator and pump should be installed distant to each other.

d

p +Δp
V

p

L
Fig. 4.15

Pipe

Water pressure loss and oil pressure loss, measured for water and oil flows in a pipe of the same size at
the same flow rate, are compared. When a fluid of density ρ, kinematic viscosity ν, and flow velocity V isflown in a pipe, inner diameter and length of which are d and L, respectively, the pressure loss Δp can be
expressed by the following equation.
Δр=

λρL 2
V
2d

λ is the pipe friction coefficient and can be expressed as follows, assuming that the Reynolds number Re
is equal to Vd/ν.

λ=64
0.3164(laminar flow) and λ=(turbulent flow), respectively.
4
Re
Re

Assuming that flow in the water hydraulic pipe is turbulent while that in the oil hydraulic pipe is laminar, theratio of the respective pressure loss can be expressed by the equation below. In the equation, a subscript w
means water hydraulics whereas a subscript o means oil hydraulics.

∆ρ w λw ρ w⎛Q⎞==6.46 ⎜ ⎟∆ρ o λo ρ o
⎝d⎠

3/ 4

(Eq. 4.1)

Assuming that the flows in the water and oil hydraulic pipes are both turbulent, the ratio can be expressedby the equation below.

∆ρ w λw ρ w==0.474∆ρ o λo ρ o(Eq. 4.2)

Pressure losses, Δρw in a water hydraulic line and Δρo in an oil hydraulic line, are both calculated using
values listed in Table 4.1 and are plotted in Fig. 4.16.
Table 4.1

Values used for the pressure loss calculation3

ρ (㎏/m )2
ν (m /s)

Water
1,000
-6
1.0 x 10

32

Oil
880
-6
34.0 x 10

In every case, the ratio remains smaller than 1.
From this result, the pressure loss in a water
hydraulic line is smaller than that in an oil hydraulicline.
Due to low kinematic viscosity of water, thepressure loss in a water hydraulic pipeline is small,and thus advantageous as a power transmitting line.
Application of water hydraulics to a drive system
where the pump and the control valve or theactuator are separately installed and a compact
system of which pipelines are of small diameter issuitable.

4.2.2
(1)

Pressure loss ratio(Water hydraulics/oil hydraulics)

The y-axis indicates the ratio Δρw/Δρo whilethe x-axis indicates flow rate Q. The pipe size d istaken as its parameter. The ratio was calculated
1
using a Schedule 80 line, from 1/8 to 2 /2 of thenominal diameter. Calculations obtained by Eq. 4.1
were indicated with solid lines while those obtainedby Eq. 4.2 were indicated with a broken line.

Turbulent
Pipe: Schedule 80

Flow rate

Fig. 4.16

L/min

Comparison of pressure loss in water
hydraulic line and in oil hydraulic line

Surge pressure prevention

Surge pressure

Generation of surge pressure must be paid attention to when flow rate of a fluid power system is high whilesudden run and stop of the system are demanded. In the ADS, the surge pressure becomes higher
compared to that of the oil hydraulic system due to properties of water. Therefore, if the user's ADS is
expected to run for fast action while generation of excessive surge pressure is anticipated, excogitating thewater hydraulic circuit and devices configuring the system n the designing stage is desirable. For example,
realizing a shock-less drive using some controllable devices, such as a proportional valve and a servo valve,can be considered.
(2)

Surge pressure test and simulation analysis in acylinder drive circuit⊿p

Using a cylinder drive circuit described in Fig. 4.18, an
experiment was conducted to examine the surge pressurethat occurs upon a sudden shutting of a valve. The flow
velocity was 9.05 m/s.
The servo valve was closed,
following the pattern described in Fig. 4.19. The surge
pressure ∆p was measured from the transient pressure
wave of the port B.
Figure 4.20 shows the test and simulation results. The
figure indicates the simulation sufficiently reproduced the test
results.
(3)

－⊿p

V
Fig. 4.17

V － ⊿V

Surge pressure generation
due to shutting a valve

Surge pressure prevention method

The experiment and simulation provide the following findings:① Extending the valve manipulation time of the servo valve suppresses the surge pressure;② Adapting two-slope manipulation effectively suppresses the surge pressure, and adjusting the time ofslopes and applied voltages (valve-opening) can minimize the surge pressure generation.

33

Pressure-receiving
area Ac
受圧面積

W4

W1

p4

p1

q4

M

Load:
50 kgkg
負荷：50

u (V)

Displacement
変位 y

9 (V)

q1

Pipe:
1 m 1/8’
管路：1m
1/8’

Pattern
パターン
PatternPipe:
5 m 1/8’
管路：5m
1/8’

C

u

B
A
Appliedvoltage u
印加電圧

p3

1 (V)

p2
A

B

0

t (s)
T/2

t
T

P

(3/4)TT

7 MPa
Fig. 4.18

T

Surge pressure test apparatus

Fig. 4.19

Two-slope manipulation

8

Simulation
計算結果
シミュレーション結果
実験結果
Experimentp2 (MPa)

6
4

∆p

2
0
–0.05

0

0.05

0.1

t (s)
Fig. 4.20

4.2.3
(1)

Comparison of the experimental and simulation results
using the servo valve (Pattern A)

System configuration and operational considerations

Filtration
・ Water supply filter: The water supply filter should be equipped, at the initial stage of operation andupon water supply for maintaining the system water level, to prevent foreign materials from migrating
to the system. When the water is supplied to a system, which is not frequently operated, thesystem shall be sufficiently drained to prevent water from containing rust and the rust fromre-entering to the system.
・ Filtration equipment (filter): To eliminate substances causing contamination, bacteria, and othermicroorganic substances, the filtration equipment shall be equipped with lines such as the watersupply line, the return line, the suction line, and so forth, if necessary. The system is desirably
designed so that it enables to monitor the clogging of such filters.
・ Air breather: Bacteria in the air should be taken into account for filter grade selection. Hollow-paper
filters (1 micron or less) can be used.
・ Monitoring of the filter pressure loss: Proper filtration of the fluid not only extends the lifetime of thewater hydraulic components, but also is important to demonstrate the maximum performance of thesystem. Therefore, the system is desirably designed so that the monitoring of the filter pressure loss
is allowed.

34

(2)

System operation temperature
・ Temperature of the system: To prevent the freezing and to restrain generation of vapor, the watertemperature should be + 5 ℃ to 45 ℃.
・ Temperature of the components: When each component manufacturer specifies operation
temperature, the component should be used within such a specified temperature. When the user
describes the operation temperature for the system, this point should be considered. Note that thetemperature of surfaces of each component should always be touchable by the human being.
・ Temperature control: If operating the system within the proper temperature range is difficult, propercountermeasures should be taken according to situations. The fluid will be frozen at 0 ℃ .
Therefore, when the system is used in cold climates or where the ambient temperature may become
0 ℃ or lower, installing some heating equipment will be required to prevent the fluid from being
frozen at any place in the system. Contrary, when the system is used where the fluid may be
evaporated due to the temperature rise of the reservoir, modifying the reservoir shape and size or
installing heat exchangers will be required. Especially, the countermeasure for places where thefluid does not circulate, such as the cylinder and rotary oscillating torque actuator, is important.

(3)

Considerations for the test operation
・ Flushing: To prevent troubles due to entry of foreign substances into the fluid, oils and dirt attachedon the pipes, fittings, and components shall be sufficiently removed before integrating them into thesystem. In addition, to remove such foreign substances in the water hydraulic unit and the pipes,
flushing shall be done when the system is operated anew. The water temperature should be kept
higher within the operational range during the flushing to improve the effect.

(4)

Considerations upon the system startup
・ Avoidance of the dry operation: To avoid damages due to the dry operation, the pump should bealways operated with the fluid supplied.
・ Ventilation: At the very first operation of the system, the air of the water hydraulic unit, pipes,
actuator, etc., must be completely evacuated to protect the components and obtain the required
performances.

(5)

Other issues
・ Periodical inspection: Vibration generated from the pump may loosen the pipe connecting elements.
To prevent the fluid leakage and the air suction, the periodical inspection should be performed tocheck and re-tighten the joint parts and screws of the pipes.
・ Service: Periodical service should be done to the air breather and filters to keep them clean.
・ Replacement of the fluid: The fluid should be periodically replaced according to frequency of systemuse, operational environment, and water quality control parameters applied to the system
maintenance.
・ Pulsation and noise of the triple plunger pump: As the triple plunger pump is mainly used at thelower rotational speed, troubles may occur to the system due to pulsation. Therefore, thepulsation-prevention measures should be taken on the accumulator and rubber hoses. Otherwise,
the system should be configured with pump unit separated.
・ Long-term system shutdown: When the system is scheduled to shutdown for a long period of time,draining the fluid or adding bactericide in the fluid is recommended. To resume the system
operation after a long system shutdown period, accumulation of bacteria, microorganisms, or solid
particles may clog the filter elements, orifices and chokes or engage the sliding parts. The suction
pressure shall be checked if those components are working as designed upon system restart. Minda pressure loss caused by the filter element; replace the element if required. Check if the water inthe reservoir is reaching the specified level if the system involves risks of water loss by water
evaporation, for example.
・ Storage of the components and unit: The user should follow the instructions provided from the
suppliers when the user stores the components and unit. Many overseas manufacturers fill the
non-freezing solution for the purpose of preventing the component interior surfaces from freezing or
rusting during storage and preservation (e. g., mono propylene glycol). When the system isoperated anew, the non-freezing solution should be sufficiently washed away.

35

Chapter 5 Application of Aqua Drive System
5.1

Applicable fields of ADS

ADS has been increasingly adopted to food processing machines, medical and care tools, and nuclear
power plant facilities. Figure 5.1 shows the result of a survey conducted with questionnaire on applicable
fields of ADS for the water hydraulic component suppliers listed in Section 2.1. The questionnaire listed 9
fields Water Hydraulics Committee and JFPA see them as immediate potentials for ADS and 10 additional
fields and asked the suppliers if they have adapted or will adapt ADS for those fields. Almost 80% of the 50
responses suggested possible ADS applications.
The survey reveals 123 cases of ADS applications, as shown in Fig. 5.1, approximately 50% of which arein the fields of (1) food processing, (2) maritime and offshore, (3) civil engineering, and (4) medical and care
(descending ranking). The rest includes the fields of (5) nuclear, (6) underwater, (7) home appliances, (8)leisure, and (9) medicine.
"Other fields" include applications in the following fields.
(1) General industrial machinery: 7 cases (machines, industrial machines, tire forming machines, injection
molding machine, clamp equipment)(2) Cleaning: 5 (cleaning, fire fighting, high-pressure jet/spray, high-pressure water hydraulic unit)(3) General industrial equipment: 4 (manufacturing line/plant, factory automation, steel making, vehicle
production)(4) Semiconductor: 4 (semiconductor manufacturing equipment, molding machine, electronics)(5) Others: 3 (coolant line for machine tools, pool, research)

17

Food processing
16

Vessels and offshore
15

Civil engineering

14

Medical and care
10

NuclearRiver

9Home appliances

9

Leisure5

Medicine

5
23

Other fields
0Fig. 5.1

5

10

15

20

25

Applications of the ADS technology

The machines and equipment specifically cited are as follows.
(1) Food processing: Food processing machine(2) Medical and care: Lifter, bathing assistance equipment, dental instrument(3) Leisure: Pool bed lifter(4) River: Drive system for fish gates, high-pressure cleaner(5) Civil engineering: Pile driver, water hydraulic trench(6) Vessels and offshore: Local application fire fighting systems for the machine room(7) Nuclear: Cooling water circulator, waste treatment system(8) Others and general industry: Hydroforming machine
In addition, the ADS technology can potentially be applied to the following:
Seawater desalination unit, paper-manufacturing machine, home elevator, shield machine, disk molding
machine, underwater development machinery, movable theatrical stage, amusement equipment, packing
machine, and rescue tool.

36

Water hydraulic systems are generally appreciated in fields that demand safety, environmental friendliness,cleanliness, low-pressure range, low related costs, high power density, and applicability in outdoor/water
front sites. According to the survey, the companies have applied the ADS technology mainly because oflower environmental impact, as described below.
(1)
(2)
(3)
(4)
(5)
(6)

Environment (nature preservation): 8 cases
Safety and cleanliness: 4
Availability of the fluid/pressure source (tap water): 2
No contamination upon leakage of the fluid: 2
No wastewater treatment required: 1
Not sensitive to radioactivity: 1

5.2

Published ADS applications

Table 5.1 lists ADS applications published in the Japanese journals and newspapers before the year 2002.
The organizations include companies, university laboratories, and research committees formed bycompanies. Some of the applications below are still under study.
Table 5.2 presents the some of their images and specifications.
Table 5.1
No.
1
2

3

4

5

Organization

Source (date)

Lift- KAYABA INDUSTRY CO.,LTD.
Automatic poultry breast deboner- MAEKAWA SEISAKUJO
CO., LTD
Forklift- MITSUBISHI HEAVY
INDUSTRIES, LTD.

HYDRULICS AND
PNEUMATICS, Vol. 39, No.
13, (2000.11)
Nikkan Kogyo Shimbun, Ltd.
(2001.2.16), others

Semiconductor forming press- New Energy and Industrial
Technology Development
Organization
Lift- SANMAX CORPORATION

10Door slider- NIPPON VALQUA
INDUSTRY, LTD
Bathing assistance equipment- NIPPON VALQUA
INDUSTRY, LTD
Water hydraulic drive system forsluice gates- Study Committee for Sluice
Engineering and Ecosystem
Motor (tap water use)
- TOKYO INSTITUTE OFTECHNOLOGY
Bathing assisting equipment- LINE INDUSTRY CO., LTD.

11

Power cylinder- FALCOM INC.

6
7

8

9

12

Publications on the ADS applications

Semiconductor forming press- TOWA KIKI, CO., LTD.

JOURNAL OF THE JAPANFLUID POWER SYSTEM
SOCIETY, Vol. 32, No. 2,(2001.3)
Report on Proposal Invitation
Project of New Business
Creation for the year of 2000
(2001.3.27)
JAPAN INDUSTRIAL
JOURNAL, (2001.6.14),
othersFLUID POWER, Vol. 15, No.
3 (2001.7)
FLUID POWER, Vol. 15, No.
3 (2001.7)“Water Hydraulic Drive
System for Sluice Gate”(2001.8)
Nikkei Sangyo
Shimbun/Nihon Keizai
Shimbun, Inc., (2001.10.29)
Nikkei Sangyo
Shimbun/Nihon Keizai
Shimbun, Inc. (2001.11.08)
Nikkan Kogyo Shimbun, Ltd.
(2002.2.08)
Nikkei Sangyo
Shimbun/Nihon Keizai
Shimbun, Inc. (2002.12.03),
others37

Application field and featureWelfare equipment- Driven by tap water pressure
Primary food processing- Can be cleaned with water, free fromelectrical leakage, HACCP-conformed
Industrial transporting vehicle (battery forklift)- Used where oil pollution must not occur.
Semiconductor molding- Ensuring uniform pressure distribution on
chips
Lift unit- Clean & useful for disaster recovery.
Working pressure Max.: 1 MPa or less
Automatic sliding door
- Operated only with tap water pressure, quiet,energy-effective, safe
Bathing assistance lifter- Operated with tap water pressure,height-adjustable
Drive system for sluice gates- Environmentally friendly, powerful, safe
Care equipment- No electricity required, driven by tap waterpressure
Care/welfare equipment- Driven by water supply and dischargepressures
Power cylinder driven by a servo motor- Converted from oil to water hydraulics forenvironmental concerns
Semiconductor packaging equipment- Environmentally friendly

Table 5. 2

ADS application

Applications using tap water pressure
No.

Name and image

Specifications (circuit)

Lift
Item

Specifications
Tap water pressure(Min.: 0.2 MPa)
100 kg or less (body weight)
Max.: 3.0 m/min.: 1.7 m
1.3 m (For a pool, 1.1 to 1.3 m indepth)
32 kg in total (Cylinder body: 18 kg)
Switching with a manual valve(Up/down/stop)

Drive source
Allowable load
LengthLift stroke
WeightUp-and-down
switching
Horizontal seat
movement
Installation
method1

Moves manually.
Two types: plate and socket

Liftersystem
リフタシステム

Tap wateroutlet
水道蛇口

To thedrainage

Source:KAYABA INDUSTRY CO., LTD.
[No. 1 in Table 5.1]

→排水口へ

Pressuresource水圧源(Tap(上水道)water
pipe line)

Tapwater hose
水道用ホース

Door slider
Item
Drive source
Working waterpressure
Allowable door
weightMax. door speed
Cushioning

2

Working force
Working noise
Durability

Limit Valve

Safety function

Rodless Cylinder

Direction Control Valve

Source:NIPPON VALQUA INDUSTRY, LTD[No. 6 in Table 5.1]

External power
supplyWorking
temperatureSpecifications
Tap water pressure(Min.: 0.2 MPa)
Max.: 0.3 MPa
Max.: 20 kg
250 mm/s
10 to 100 mm/s
(closing side, adjustable)
58 N
Max.: 40 dB
Min.: 0.2 million actions
The outer bracket is unlocked
upon entanglement.
Not required
0 to 60 ℃ (no condensation)

Applicable in: Places where no electricity is allowed or
special attention must be paid for safety (spa/bathroom,
hospital, care facility, plant/research facility, and dangerous
object (oil/organic solvent) warehouse)

38Applications to factory machinery
No.

Name and image

Automatic poultry breast deboner

Specifications (circuit)(Feature)
This machine consists of elevating stations on arevolving table and processing units and separates theupper body of poultry into breast, fillet, and bone. It canbe frequently cleaned with water to ensure food safety andhygiene.
Item
Throughput
ADS aspects

3

Components

Source:
MAEKAWA SEISAKUJO CO., LTD[No. 2 in Table 5.1]
Semiconductor forming press unit

(Merits of ADS application)
・ Carefree for water cleaning (free from short circuits andrust, HACCP-conformed)
・ Compact and high power, easily re-locatable・ Facilitating food hygiene management
・ Allowing easy maintenance with a centralized drive
source(Feature)
A press unit used to apply a resin coating to the outersurface of a wafer in a semiconductor manufacturing
process
Item
Pressing force
Pressing speed
Effective stroke

4

Source:
New Energy and Industrial Technology
Development Organization[No. 4 in Table 5.1]

Specifications
900 pieces/hour Max.
Pressure
Elevation unit: 7 MPa
Processing unit: 2 MPa
Pump, motor, cylinder, servo
valve, directional control
valve, etc.

Specifications
980kN Max.
Forming: 0.01 to 20 mm/s
High-speed operation: 75
mm/s
150mm

ADS aspect

Pressure: 13.7 MPa
Flow: 52 L/min

Components

Pump, cylinder, servo valve,
directional control valve,
accumulator, etc.

(Merits of ADS application)
・ Reducing environmental impact
・ Contributing to a more compact system (compact andhigh power)
・ Permitting uniform resin coating with a direct pressure
from the water hydraulic cylinder
・ Allowing accurate position, speed, and pressure control

39

Chapter 6 Future Perspectives of Aqua Drive System
6.1

Social demand and ADS

Engineering, due to its nature and academic system, is fundamentally different from science. Science isto seek the absolute truth in any condition whereas engineering is to pursue optimal solutions with given
conditions. In the 20th century, science and engineering developed the manufacturing industries and madean unprecedented achievement in both quality and quantity of production. However, just before the newmillennium, when the mass production and consumption triggered problems, environmental destruction, or
natural resource depletion, and when they obviously emerged, people have recognized the importance andurgency of taking actions to solve the problems and, gradually, they have started to reflect their behaviors as
consumers. People start walking with a slogan, “the 21st century is the century of the environment,” and we
can no longer neglect tangible and intangible factors from the industrial activities, or manufacturing products.
In other words, the industrial activities have to change the course to be more human-friendly. Making theindustrial activities more human-friendly is a requirement to education of engineers and technicians.
This global paradigm shift will have an effect on the fundamental technologies in mechanical engineering.
Drive systems having the variable-speed characteristics show excellent controllability to various types ofmotors and loads; they are essential for the manufacturing and working machinery in every manufacturing
field. Now, the known drives are: oil hydraulics, pneumatics, and electricity. However, when it comes tocompliance to the industrial conditions of the 21st century, there is no other drives but ADS using tap water
as the fluid. ADS, by taking an advantage of tap water use, can assure our healthy environment: safety,
cleanliness, and hygiene, and coexist with animals and plants as well as human beings.
Anticipating such a global technological trend, universities, academic associations, or industrialorganizations in Japan have been fostering a great interest in ADS and have worked out for long. The
Japan Fluid Power Association has provided a ground for some important studies on water hydraulics andsociety:
Technical Study on Environmental Friendly Water Hydraulic Drive Systems (1998 to 2000)
andResearch and Study for the Practical Use of the Aqua Drive Technology (2001 to 2003).
This is thesummary of the history of the primary research and studies done for the past six years. (1) The Committeeorganized and conducted experiments to investigate the water quality control issues and the water hydraulicdriving characteristics. The experiments resulted in establishing a guideline for the water quality control.
In the experiments, where a circuit modeling the injection and dwelling processes of an oil hydraulic precisionmolding machine, such as an injection molding machine or die cast machine, the high-speed operation using
the logic valves was achieved. The Committee focused on the surge pressure generation in particular, andexamined methods for the prediction and prevention. Their work established a guideline to actualize apractical water hydraulic application including the methods to design and control the system. (2) The
Committee collected information to complete as a buyers’ guide that includes a list of manufacturers andsuppliers covering specifications of their ADS components, responses of questionnaires regarding thematerials, and some examples of the practical applications. The guide is designed to provide water
hydraulics users with search courses to assist them. (3) The Committee published “Aqua Drive System – A
Technical Guide.” This guide will contributes to promote the ADS widely to end users and system suppliers.
This English version (the 2nd edition) will provide anyone interested in water hydraulic systems with thelatest ADS information in Japan.

6.2

Market and prospects of ADS

Some ADS applications were demonstrated in business expos.: a semiconductor sealing system in
SEMICON Japan 2002 and an automated poultry breast deboner in FOOMA JAPAN 2003. They received
attention especially from those who are environmentally aware in related industrial fields. However, they
still have technical problems to overcome to actualize practical water hydraulic applications.
To actualize the practical applications, it is important to select appropriate and potential fields and predictthe market scale on the assumption that the water hydraulic products are adapted. The following 15 fields
are suggested by our investigations as promising applicable fields of machinery and tools:
sluices/water gates for rivers, home elevators, injection molding machines, seawater desalination
plants, atomic power plants, disk molding machines, semiconductor molding machines, food40

processing machines, social welfare tools (lift, bed), shield machines, paper manufacturingmachines, packing machines, movable theatrical stages and sports/amusement tools, rescue
tools (deck guns), underwater development machinery.
To penetrate the ADS technology, solving technical problems and increase of recognition are essential.
The following problems are picked up:
countermeasures to low temperatures, corrosion/erosion, sealing technology, reliability/lifetime,
reduction of the initial cost, maintenance evaluation, water quality control, LCA evaluation.
Using the Delphi method, the Committee predicted when these problems become negligible for promoting
ADS, or the time required to solve them. Experts including the Committee members concluded that it would
be from three years to eight years, for which they can be responded with individual technologies and withsome complicated technologies.
The four driving systems: water hydraulics, oil hydraulics, pneumatics, and electricity, will be evaluatedwhen ADS is more matured with metrics on environmental loads. The total market scale of water hydraulicproducts is estimated to become 60 billion-yen six years later, 2010, and 100 billion-yen in 2012. The
Committee concludes that, appropriately sharing the market of the driving systems with the rest threemethods and creating new applicable fields, the market output in 2012 will exceed 100 billion-yen.

6.3

Boosting the ADS-related industries

The introduced ADS technologies are now start transforming into practical applications. Building up anorganic linkage between academic, industrial, and government organizations is a must to facilitate thetransformation. Some primary linkages are explained below.
Linkage between water hydraulic component and ADS-applied system manufacturers and end users: Aninteractive link should be built between water hydraulic component/ADS-applied system manufacturers andend users. The end users will easily recognize ADS and have interests because the technology ischaracterized by some keywords describing essential elements to our daily life: environmental issues, safety,
or cleanliness. Component manufacturers need to supply not individual components but systems to
ADS-applied system manufacturers, satisfying demands of the end users. A tide from the both sides will
surely build a virtuous circle involving the ADS-applied system manufacturers.
Linkage between component and material manufacturers: To solve the technical problems and promote
the commercial supply of ADS, this link should be important in addition to the component-manufacturers link.
The operational pressure range of ADS is from the water pipe network pressure to 14 MPa. Because ADS
operates in a wide operational pressure range from the tap water level to 14 MPa or higher, selecting
appropriate materials and treatment/processing methods and developing appropriate system configuration
are critical. Each manufacturer will be responsible for and collaborate together in the linkage for theseissues.
Linkage between young engineers and users: Communication with the engineers and the users througheducational opportunities or promotion activities is important and is effective to promote the ADS technology.
To educate young researchers and engineers in particular, letting them develop new and original ADS
components and systems is recommended.
Linkage between governmental bodies: Governmental bodies are expected to facilitate development andpromotion of the ADS technology, which contribute to environmental conservation and assurance of safety of
the nationals: revision of laws and regulations or supporting projects through public fund.
END

41

JFPA Water Hydraulics Committee Members:Companies and Universities“Technical Study on Environmental Friendly Water Hydraulic Drive Systems” from 1998 to 2000
For the year of 1998 (7 companies)
EBARA RESEARCH CO., LTD., KAYABA INDUSTRY CO., LTD., TOYOOKI KOGYO CO., LTD.,YUKEN KOGYO CO., LTD., NABCO LTD., TOKIMEC INC., KITAMURA SHOKO CO., LTD.
For the year of 1999 (10 companies)
EBARA RESEARCH CO., LTD., KAYABA INDUSTRY CO., LTD., TOYOOKI KOGYO CO., LTD.,YUKEN KOGYO CO., LTD., NABCO LTD., TOKIMEC INC., KITAMURA SHOKO CO., LTD.,
NACHI-FUJIKOSHI CORP., YAMAMOTO SUIATU KOGYOSHO CO., LTD., TAKAKO INDUSTRIES,INC.
For the year of 2000 (10 companies)
EBARA RESEARCH CO., LTD., KAYABA INDUSTRY CO., LTD., TOYOOKI KOGYO CO., LTD.,YUKEN KOGYO CO., LTD., NABCO LTD., KITAMURA SHOKO CO., LTD., NACHI-FUJIKOSHI
CORP., YAMAMOTO SUIATU KOGYOSHO CO., LTD., TAKAKO INDUSTRIES, INC., SAKAGAMISEISAKUSHO LTD.

“Research and Study for the Practical Use of the Aqua Drive Technology” from 2001 to 2003
For the year of 2001 (16 companies)
EBARA RESEARCH CO., LTD., KAYABA INDUSTRY CO., LTD., TOYOOKI KOGYO CO., LTD.,YUKEN KOGYO CO., LTD., NABCO LTD., KITAMURA SHOKO CO., LTD., NACHI-FUJIKOSHI
CORP., YAMAMOTO SUIATU KOGYOSHO CO., LTD., TAKAKO INDUSTRIES, INC., TOKIMEC
INC., TAIYO, LTD., HIROSE VALVE INDUSTRY CO., LTD., KAWASAKI HEAVY INDUSTRIES,
LTD., NOK CORPORATION, TACO CO., LTD., NIPPON VALQUA INDUSTRIES, LTD.
For the year of 2002 (16 companies)
EBARA RESEARCH CO., LTD., KAYABA INDUSTRY CO., LTD., TOYOOKI KOGYO CO., LTD.,YUKEN KOGYO CO., LTD., NABCO LTD., KITAMURA SHOKO CO., NACHI-FUJIKOSHI CORP.,SMC CORPORATION, TAKAKO INDUSTRIES, INC., TOKIMEC INC., LTD., TAIYO, LTD., HIROSEVALVE INDUSTRY CO., LTD., KAWASAKI PRECISION MACHINERY LTD., NOK CORPORATION,TACO CO., LTD., NIPPON VALQUA INDUSTRIES, LTD.
For the year of 2003 (16 companies)
EBARA RESEARCH CO., LTD., KAYABA INDUSTRY CO., LTD., TOYOOKI KOGYO CO., LTD.,YUKEN KOGYO CO., LTD., NABCO LTD., KITAMURA SHOKO CO., NACHI-FUJIKOSHI CORP.,SMC CORPORATION, TAKAKO INDUSTRIES, INC., TOKIMEC INC., LTD., TAIYO, LTD., HIROSEVALVE INDUSTRY CO., LTD., KAWASAKI PRECISION MACHINERY LTD., NOK CORPORATION,TACO CO., LTD., NIPPON VALQUA INDUSTRIES, LTD.

Member universities from 1998 to 2003
Faculty of Science and Technology of Sophia University
Faculty of Engineering of Yokohama National University

Executive office: The Japan Fluid Power Association(Note) Contact JFPA regarding context of this book or the products shown.
This project is made possible with grants (50 %) and contributions from the member companies(50 %)

42

This project is made possible by the promotion grant
for machinery-related industries offeredby the Japan Motorcycle Racing Organization.

Issued on March, 2004
Issuer: Susumu Hiromitsu
Organization
Japan Fluid Power Association
Kikai Shinko Kaikan, # 311, 3-5-8 Shiba-koen
Minato-ku, Tokyo 105-0011 JAPAN
Phone: 03-3433-5391
Fax: 03-3434-3354
URL: http://www.japan-fluid-power.or.jp/
E-mail: jfpa@japan-fluid-power.or.jp

Japan Fluid Power Association
Kikai Shinko Bldg., Room 311
3-5-8 Shiba-koen,
Minato-ku, Tokyo 105-0011 Japan
Phone: +81+3-3433-5391
Fax: +81-3-3434-3354