Spring 2017
No.32

【The 90th Anniversary Special Edition】● Greetings・
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President & CEO Toshikazu Takisawa● Greetings upon the Publication of the 90th Anniversary Special Issue・・・3
Senior Excutive Officer Director of Corporate Research and Development Group

Mutsuo Aoki

● Upon the Publication of the 90th Anniversary Special Issue・
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Editorial board of the 90th anniversary special issue of Valqua Technology News● Transition of Valqua s technologies and customer value

Looking back at the history of Valqua Technology News and Valqua Review・・12
Senior Fellow Takahito Nishida● Contribution

Congratulations on the 90th Anniversary Special Issue of Valqua s Establishment・・・15
Professor Emeritus at the University of Hiroshima Toshiyuki Sawa

● Contribution

Evolving Gasketing and Sealing Technologies・
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Professor at Mechanical Engineering, National Institute of Technology,
Numazu College Takashi Kobayashi● Contribution

Congratulations on the 90th Anniversary Year of the Founding・・19
NIPPON VALQUA INDUSTRIES, LTD.
Manager) Takao Iwane

former Managing Director (Technical● Contribution

Congratulations on the Publication of the 90th Anniversary Special Issue ofValqua Technology News・
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NIPPON VALQUA INDUSTRIES, LTD. former Managing Director (Technical･ Business development) Yoshiaki Mori

● Contribution

Memories of My Tenure as CTO・
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・24
NIPPON VALQUA INDUSTRIES, LTD. former CTO Hiroyuki Kuroda● Technical Papers

Types and Application of Filler-added PTFE Materials・
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Corporate Research and Development Group
Development DivisionHigh Performance Plastics Development Division Youichiro Wada

● Technical Papers

Accuracy and Mold Direction of PTFE Products・
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Corporate Research and Development Group Development Division High Performance
Plastics Development Division Technical Service Section No.3 Shigeko Kawai
Corporate Research and Development Group Development Division High Performance
Plastics Development Division Technical Service Section No.3 Nobuyuki Ota● Technical Papers

Introduction and Utilization of Seal Quick Searcher （SQS）‒ Gasket Version ‒・・33
Sales Group Technical Solution Division Toshihiko Enishi● Technical Papers

Causes of and Countermeasures for Allophone Trouble in a Piston Seal
System for Cylinders・
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Corporate Research and Development Group Development Division kenichi Takahashi● Technical Papers

Sticking Troubles of O-Rings and Countermeasures・
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Corporate Research and Development Group Development Division Masanori Okazaki● Technical Papers

Evaluation of the Bolted Flange Connection with PTFE-blended
Gasket under High-temperature and Long-term condition・
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Corporate Research and Development Group Development Division Kouji Satou● VALQUA s Technical History・
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・54
● Recent Technology News Back Issues・
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・58

Greetings
Toshikazu Takisawa
President & CEONIPPON VALQUA INDUSTRIES, LTD.

First of all, we would like to sincerely thank our valued readers for yourcontinuing interest in our Valqua Technology News. Thanks to yoursupport, we are able to celebrate our 90th anniversary this year. We
promise to expand our seal engineering legacy, to strive harder to create innovative technology withnovel value, and to contribute to achieving a sustainable society. To mark our 90th anniversary, thisissue covers projects that demonstrate our technological commitments in an easy-to-understandmanner. We hope you enjoy the Valqua Technology News.
Last year, the world witnessed political upheavals including Brexit, the U.S. presidential election andSpring 2017highly volatile resource prices for petroleum and natural gas in particular. Due to these events,
exchange rates and stock prices on many markets fluctuated greatly, so it was difficult to predict thebusiness environment. Amid the global situation, the Japanese market enjoyed a moderate recovery
over the year-end thanks to some strong industries, mainly semiconductor equipment manufacturers.

No.32

However, unfair practices including falsification of fuel economy tests in the car industry and a roadcollapse near Hakata Station reminded us of the huge social responsibilities of companies and theimportance of risk management. The year 2016 also witnessed accelerating technological progress,
such as autonomous driving technology and the introduction of AI in various industries.
Under such business environment, the VALQUA Group is working on its seventh medium-term
management plan, New Valqua Stage Seven (NV・S7), by optimally restructuring its business frameworkwith a broader perspective. Through the plan, we aim to strengthen how we manage global risks. Oneof our challenges is to promote technological development, particularly our seal engineering technology.
In the global markets, we are also reinforcing the creation of novel value in products and services,which are the two major components of H & S*. Through such activities, we aim to transform the
VALQUA Group into an H & S company.

1One of our value-creating commitments is training sessions. Since we believe that our seal engineering
can provide our customers with“safety and security”through our products, we offer training session
services based on the H & S concept in the worldwide markets, which are receiving positive feedback
from numerous customers. In this issue,“Valqua Technology News”features a wide range oftroubleshooting cases as examples of our customer-oriented solutions.

Again, we thank our valued customers for your continued support, which has allowed us to celebrate
this 90th anniversary. We would greatly appreciate your further guidance and encouragement and wewish you a long and successful future.
* The term“H & S”means working to maximize customer value through“H (hard = products)”and“S (seal-engineering service).”

Spring 2017
No.32

2

Greetings upon the Publication of
the 90th Anniversary Special Issue

First of all, we would like to sincerely thank our valued readers for their continuing interest in our
Valqua Technology News as a means to understand how we are dealing various technologicalchallenges.
We are pleased to celebrate the 90th anniversary of Nippon Valqua Industries this year. We takepride in our contribution to industry development through our fundamental technologies; namely, sealengineering and fluorocarbon polymer processing technologies. Today, various industries are pursuing
technical innovation: higher integration and performance in the semiconductor industry, utilization ofhydrogen energy to achieve a low-carbon society in the energy industry, and introduction of

Spring 2017

autonomous driving technology and AI in the information and communications industry. Since ourNo.32

We are thankful for the many people who have helped us realizing our technological achievement,

seal and material-processing technologies are closely related to these industries, we have been
making great effort to keep pace with technological development and to provide product with value
desired by our customers.

and some of them contributed articles to this spring issue illustrating our technological transition
from past to present, and our current technologies resulting from the continuous development
activities up to today. We have always provided customers with seal products and fluorocarbon
polymer products of high value, as well as solution services, through which we have made manytechnological achievements. As for the technology feature article this issue, like previous one, we
introduce these technological achievements mainly from the standpoint of solving customers’
problems.
One of our achievements of special importance is that, as the pioneer in seal engineering, we initiatedto address the problems of asbestos and totally replaced it with non-asbestos based products ahead ofother companies. We have also led the industry in technologies for reliability evaluation and productlifetime prediction to enhance the safety of non-asbestos products. Through such activities, we havealso accumulated deeper technological knowledge and capabilities, and based on these assets together
with our seal engineering services expertise, we, offer our customers new value as the H&S
3company.
This issue introduces the Seal Quick Searcher®
（ SQS）service, and the“Evaluation of HighTemperature and Long-Term Properties of Fastening Bodies with PTFE Gaskets,”a reliability
evaluation method for enhanced safety in using seal products. This issue also features case reports
how we solved customer`s problems utilizing the solution services related to fluorocarbon polymer
processing and seal technologies. We hope you find these reports interesting and useful.
We will continue to monitor current trends and develop unique technologies to offer products andservices that meet the needs of our customers. Again, we thank you for your support and hope tocontinue serving you in the future.
Senior Excutive Officer

Director of Corporate Research and Development Group

Mutsuo Aoki

Spring 2017
No.32

4

Upon the Publication of the 90th Anniversary
Special Issue
Introduction
This special issue of Valqua Technology News

revitalize industries under this policy and thespirit of value and quality, from which ourcompany derives its name.

celebrates the 60th anniversary since the firstpublication of its predecessor, Valqua Review.

Under a contract with the Ministry of

We sincerely thank all our valued customers

International Trade and Industry, we

and readers who have supported us throughundertook several research projects tothe years, and would like to tell you about ourdevelop Japanese technologies, including high-history upon the publication of this 90th

temperature and high-pressure steam

anniversary special issue.

packings, packings for industrial use（asbestos
joint sheets）, aircraft packings primarily

Spring 2017
No.32

１．Historical background leading to
the publication of Valqua Review
Nippon Valqua Industries was the firstmade from silicone rubber and Teflon®, andmethods for manufacturing and processing
tetrafluoroethylene resin. Our research
produced some excellent results.

Japanese specialized manufacturer of seal
products. At that time, industries wereDuring the same period, we established agrowing since World War I and needed toresearch association on fluororesin.

manufacture industrial products within Japan.

Fluororesin was gaining popularity andIn line with this trend, Nippon Valqua

eventually became widely used in various

Industries was established for the domestic

industries.

production of seal products.
In contrast, seal products were not well
Japan’s petrochemical industry was also

known. According to reports at that time,

starting to grow at that time. However, major“Although packings are important forseal products were being imported frommaintaining the airtightness of fixed andEurope and the U.S. due to the lack ofmoving parts of machinery and preventing

technologies and related technical information

leakage of processing fluid in a wide range ofin Japan. Determined to produce seal

production plants, their value is overlooked

products in Japan, we studied and learned

due to their inconspicuous nature.”from imported products. As a manufacturer,
we aimed to communicate with customers toWith this background, we decided to produce

meet their needs and build their trust in seala technical journal as a 30th anniversary

products. Over the years, we have helped toproject, to raise awareness of packings that5was then c al l ed “ ob tu r ator s ” th r o ugh
theoretical and academic content. We also
wanted to disseminate information about
packings and encourage universities andindustrial high schools to offer courses on
packings.
In December 1957, the first issue of Valqua
Review technical journal was published.

2. Valqua Review2-1）Inauguration of Valqua Review
frequency-resistant insulating materials. Thus,

Takizawa, explained the purpose of Valqua

the journal articles cover a wide range of

Review as follows:“We want to communicate

industrial goods including machinery,with each valued customer, to learn fromchemicals, and electrical products.”

their honest feedback on our products, toUnder such policy, for 44 years since its

improve based on their feedback, and thus toinauguration, Valqua Review has consistently

repay customers for their support. We also

been issued monthly; approved for third-classask academic and industry experts to

mail as a technical journal; distributed tocontribute articles to our journal. We want tocustomers, universities, academic institutions,introduce new ideas and information to ourand libraries to raise awareness of seal

readers, in addition to information on our

technologies; and actively welcomedcurrent and upcoming products.”

contributions from external parties since it is

The background leading to the inauguration

not an in-house journal.

of the journal and its role were described by

At the time of its inauguration, the journal

Mr. Takizawa as follows:“Nippon Valqua

received supporting contributions from

Industries has more than a 30-year history as

academic and industry experts including Dr.

a packing manufacturer. Our product line has

Matake Kurokawa, then director of thealways centered on packings but has also

Agency of Industrial Science and Technology;

expanded to include other industrial goods.

Dr. Masao Yamagata, then academic dean ofThanks to our customers’support, we are

the Faculty of Engineering at the University

celebrating our 30th anniversary. During theof Tokyo; Dr. Uichi Hashimoto, then chairman

postwar period, we provided various chemicalof the Japan Society of Mechanical Engineers;

products including fluororesin packings ahead

and Dr. Shunichi Uchida of the Tokyoof other companies. The excellent electrical

Institute of Technology. This wide range ofproperties of the resin allowed us to expand

contributors represented the highour business to heat-resistant and high-expectations for the journal.
6

Spring 2017

The president at that time, Toshihisa

No.32

Spring 2017
No.32

Dr. Kurokawa expressed his expectations asvarious forms and used for high-temperature

follows:“This journal provides an appropriate

and high-pressure fluids. Thus, the demandframework at a time when few periodicals

for products changed from the time when

cover topics related to packings andthose had been called“obturators.”That is,insulating materials, which are important for

the recognition of leaks changed from simply

industry. However, it is not easy toa loss of energy to problems which hindered

understand their characteristics and use themthe manufacturing environment. Along withappropriately because they are made fromthe raised awareness of packings forvarious materials including metals, inorganics,

preventing leaks, seal manufacturers

and organics. Packings and insulating

gradually started to resolve the problems.

materials have become very diverse with the

In the 1960s, basic research was actively

development of synthetic resin materials. I am

conducted worldwide, and in the 1970s, manypleased to see the inauguration of this journal,

polymer molecules were synthesized. In theand I hope it will help overcome such issues.”

field of fluororesins and synthetic rubber, new

The same year that the journal wasmaterials were developed one after another.

inaugurated, 1957, the Petrochemical Industry

Accordingly, Valqua Review featured articles

Association （predecessor of the Japanon ways of developing systems to meet thePetrochemical Industry Association）started

emerging needs with new materials.

its activities. In the previous year, 1956, theIn the 1970s, the Japanese economy suffered

Hydraulic Machinery Industry Association

turbulent times with the Nixon Shock, Oil（predecessor of the Japan Fluid Power

Shock, and High-Growth Period. This led

Association）
was inaugurated. Since there wasJapan to change its economic path from thelittle knowledge of seal technology at that

pursuit of high growth to the pursuit of stable

time, the need for systematic information on

growth. The era witnessed remarkableseal products started to emerge. Valquadevelopments in export industries including

Review emerged to meet those expectations.

the auto, ship and vessel, and steel industries.
Also, developments in the emerging atomic,2-2）Transition of articles in Valqua Review（December 1957 to June 2000）

space, and information industries were
expected.

From its inauguration in 1957 to the 1960s,

As industries pursued product development,

the journal featured articles to raisesystemization, and informatization, we shifted

awareness of seal products. The articles

from the management of leaks to theranged from basic research on fluororesin andfollowing missions: systematization of seal

the introduction of overseas technologies to

products as seal engineering or technologies

contributions written from the viewpoint offor machine elements and expansion ofseal users, such as“Accurate Utilization andsolution services by introducing diverse seal-

Selection of Seals,”practice-based articles andrelated products. Thanks to many

eventually articles based on in-house data.

contributions from external parties, articles inAt the time, seals were manufactured in

Valqua Review were categorized by elemental

7

articles were published in two independentdata. Valqua aimed to help create not only in-books.

house technologies but also a cross-sectional

In the 1980s, industries started to focus on the

consortium. The resulting achievements were

following: streamlining, improvements inpublished as books by Kindai Henshu-sha:

controllability and operability, improvements

O-Ring, the O-Ring Society, 1969; Gasket, thein safety, environmental protection and

Gasket Society, 1974; and Air-Pressure Seal,

disaster prevention, and compliance with

the Air-Pressure Seal Society, 1977. These

Japanese and international standards such as

greatly contributed to standardization of the

JIS and ISO. In addition, work began on

industry.

advanced technologies that would support the

The journal began to feature articles oncoming economic system, leading tovarious fields including electrical insulating

developments in biotechnology, space,materials using fluororesins, vacuum seals

semiconductor/electronics, and new-energy

including bellows, and building materials

industries.

using glass fiber. Valqua Review became aValqua Review started to run lecture articles

reputed technical journal and was highly

on seals. The journal increasingly featured

evaluated as a technical resource.

articles on fluororesins and fluororubbers toreflect trends in new energies including those

When our company was founded, there werein their use in the atomic-power industry andno sales engineers. However, as we grew, wetheir use at low temperatures in the LNG

started to hire and train sales engineers inindustry as well as semiconductor-associatedthe 1970s.

trends in their use for chemical-liquid

There have been many interviews withprocessing.

external experts in the journal since it was

On the other hand, environmental regulations

started. These articles covered topics ranging

were being tightened and requirements forfrom prospects for technology to prospects

new registration of chemical substances were

for the future, including New Year Random

becoming stricter. Therefore, the pace of new-

Talk - What future lies ahead in the 1980s

material development slowed and the（January 1980）and New Year Random Talk -materials used for product development

Perspectives on China in the 1980s（January

started to be controlled. Valqua Review1981）.

increasingly featured research on non-The specialty series of Valqua Review wasasbestos trends, polymer alloys, composite-

serialized starting with Bochu-Kanwa（talks

making, and sophistication of compounding

during the breaks in one’s work）in April 1977

techniques.

and ended as Kanchu-Kanwa (a talk in freeIn the 1990s, industries became moretime) in May 2000. The writer Tatsuya Imotoglobalized. The semiconductor and electronics

talked about his experiences as an engineer

industries, which became major players,and garnered many readers, and readers

expanded through the digital revolution andlooked forward to the series. A total of 188

fluctuations of these industries started to8

Spring 2017

technology and edited as a series of technicalNo.32

greatly affect the economy. Environmentally,
regulations on chlorofluorocarbons wereintroduced to curb global warming, theproblems of dioxin that is associated with
waste incineration as well as endocrine
disrupter received much attention, and thefirst asbestos regulation was legislated inEurope ahead of other countries.
Valqua Review reported many studies on
elastomers in the early 1990s, featuring
hydraulic-pressure seals and tribology.
Among the feature articles, Shinzo Koujiya, aprofessor of Kyoto University at that time,

Spring 2017
No.32

contributed a five-year series Introduction to

280 academics, wrote articles for the journal.

the Science of Rubber, which was published by

We sincerely thank all contributors for their

Nippon Valqua Industries in 1995. Regarding

invaluable support.

seals, the journal reported research on
vacuum seals including spring-energized
metal C-ring seals. For semiconductors, thejournal systematically reported research on

3. Valqua Technology News
（From Autumn of 2001 to present）

tank linings.

Valqua Technology News was inaugurated inAlong with diversifying needs andthe autumn of 2001 as a quarterly journal,

globalization, the journal started to report on

focusing on articles. The goal of the renewal

efforts to enter new fields, and included

was to promote our unique skills to the publictechnical reports associated with individual

more clearly. Upon its inauguration,needs in the late 1990s. As the articles

Toshikazu Takizawa, the president of Nippon

became more diverse and specialized, theValqua Industries, commented,“We willcontents of the journal became less consistent.

strive to introduce our excellent technologies,

Therefore, in the first year of the newparticularly our core area of seals, in an easy-

medium-term plan New Valqua Stage 1, along

to understand manner, and to offer customers

with a renewal of the management

diverse solutions.”

philosophy The Valqua Way, the concept of

To date, a total of 32 volumes including thisValqua Review was reassessed, leading to theissue have been published, including f 182

rebirth of the journal as Valqua Technology

articles and 79 technical papers. Since theNews.

journal focuses on reporting Valqua’s

Some 488 volumes of Valqua Review

technologies, the number of external

containing 1,707 reports were published. Of

contributions has decreased. Nevertheless,the 1,707 reports, 1,061 were technical papers.

there have been articles from 15 contributors

A total of 824 external contributors, including

including 9 academics.

9

However, rapid social developments haveregarding measures to address global

created social challenges including

environmental problems and global

environmental problems, resource problems,

procurement/international specialization. In

and urbanization. These problems are started

industry, miniaturization of semiconductors,

to interact with each other on a global scale.

enlargement of liquid crystal displays,

To resolve the challenges, open innovation

increase in information technology capacity,

through collaboration among academia andintroduction of clean energies, and life-science

industry is certainly appropriate.

and nanotechnology started to flourish.

In this environment, the journal is

Valqua Technology News aims to clarify thei nc re a si ngl y f e a t uri ng a rt i c l e s o n t h ecompany’s direction through its articles. Its

existential meaning of Nippon Valqua

reporting covered performance-assessment

Industries as a seal-engineering manufacturer.

research on non-asbestos gaskets of various

Finite element analysis（FEA）technology

types; development of highly functional

comprehensively analyzes the varying life ofelastomer series suitable for theseals on the basis of experimental data.

miniaturization of semiconductor devices; andProgress in FEA technology allows customers

the development of vacuum technologies forto intuitively understand issues throughthe nano-development environment. We havevisualization. The technology has also been

worked to increase the value of our products

used to write many articles. The technologies

for society through modularization andhave been integrated to offer solution services‘componentization.’The journal has also

on the basis of users’comprehension of thereported our work on vacuum components,

system. We are endeavoring to expand our

hydraulic systems as a next-generation powerbusiness to technical training whichsource, membrane filters, millimeter-wave

integrates hard and soft aspects to meet the

products, waste-fluid recycling systems, anddemands of the times, and to enter the field ofreticle automated transportation systems.

trouble prevention diagnosis. The journal

The period since 2010 is difficult to describe.

covers all these areas.

Other
Other
Total Numberof Articles
Product
Introductions

Technical
PapersTotal Numberof Articles

Technical
Papers

Product
Introductions

10

Spring 2017

The 2000s was a significant transition period

No.32

4. Conclusion

spirit of contributing to industry. We hope
you will understand how that spirit has been

In this 90th anniversary year since Nippon

inherited. We will strive hard to keep

Valqua Industries’inauguration, we looked

providing the technical information sought byback at our history spanning from Valqua

our valued readers. We look forward to

Review to Valqua Technology News. The

continuing to serve you with future editions.

publication has always maintained its original
Editorial board of the 90th anniversary special issue of Valqua Technology News

Spring 2017
No.32

11

Transition of Valqua’s technologies
and customer value
Looking back at the history of Valqua
Technology News and Valqua Review
Since its founding in 1927, Valqua has focused on the research, development, and manufacture of sealing
products and sealing materials based on technologies developed in-house.
In the 19th century, Japan imported most of high-class sealing products. After that, mineral oil started to
be used as hydraulic oil to replace vegetable oil. Given that synthetic rubber was considered more suitable
than natural rubber for use in mineral oil, we developed compounding technologies for synthetic rubber,
to allow us to domestically produce sealing products. In this way, we have consistently worked behind thescenes to support domestic industries since before World War II.
Just after World War II, we discovered the existence of fluororesin and decided to utilize its excellent
chemical resistance for consumer use. With the goal of domestically molding fluororesin, we imported theresearch and developed our own technologies, marking the first success in fluororesin research in Japan.
In the 1950s, the chemical industry started introducing fluororesin widely. We are proud to havesupported the growth of the Japanese semiconductor industry as well.
Valqua’s products are basic parts of machinery and their range of application expanded rapidly in the
postwar period, and yet our products could rarely be seen in action. However, we wanted more people toknow about our technologies and products, which we believed would contribute to industrial development
in Japan. Therefore, in 1957, we issued Valqua Review, a monthly technical journal, as a 30th anniversary
project.
Valqua Review aimed to widely disseminate information on our technologies and contribute to social
development. Thus, we published articles written by various contributors ranging from customers toacademic experts. The journal introduced sealing technologies and various new materials including
fluororesin and elastomer. The journal contents attracted considerable attention from readers, especiallyplant engineers working mainly in the petrochemical industry, which led the post-war industrial recovery,
and the publication was highly evaluated.
Thereafter, diverse materials have been created along with developments in various industries, and we
too have developed a range of products for different industrial applications. In the 1970s, expandedgraphite was introduced as sealing material, and was mainly used for gland packing. Later, it was widelyused as a filler for spiral wound gaskets along with fluororesin filler. Following the growth of thepetrochemical industry, the semiconductor industry rapidly developed. Fluororubber O-rings, which are
12

Spring 2017

powder material in 1951 and started research and testing on processing methods. We proceeded withNo.32

resistant to high temperatures in the baking process, were introduced in the semiconductor
manufacturing process. Material prices were rising. In parallel, rubber compounding technologies were
gradually standardized, and, regarding seals including gaskets, the basic composition was established. In asense, the technologies reached maturity.
Therefore, for sustained growth it was necessary to expand into growing markets and to develop novel
technical concepts.
Regarding semiconductor manufacturing processes, a type of fluororubber that emits less gas and isresistant to varying ambient plasma was required in line with improved equipment performance. To meetthis need, a novel elastomer seal“ARMOR CRYSTAL®”was developed; it was introduced to thesemiconductor market in 1998.
At that time, material technologies were significantly changing to meet environmental regulations,particularly those for asbestos.
Consequently, Valqua revamped Valqua Review and produced the new quarterly technical journal Valqua
Technology News in the spring of 2002. The renewal aimed to transform the journal into a better sourceof information and to offer more customers technical information in new fields and markets including

Spring 2017

developments in the semiconductor market and various devices, and information on technologies related
to the changing social environment.
（）
New products have new functions that accommodate new technology trends. In response to thesetechnological changes, not only conventional material technologies but also technologies for evaluating the
new functions were needed. That is, reliability assurance technologies were required for the new fields

No.32

and markets.
Conventional products had been supplied based on performance history premised on conventional
technologies. However, due to changes such as regulations on asbestos, which forced manufacturers toradically replace main materials and produce alternative products, the alternative products could not be
supplied based on performance history, because these new products had no performance history. So, it
was necessary to gain social and technical recognition of these products. New technologies were required
to replace performance history, namely reliability evaluation technologies for clarifying the essentialfunctions expected of products, evaluating these functions, and assuring their long-term reliability.
In 2006, Valqua launched the general-purpose, non-asbestos sheet“GF300”. The development of“GF300”
was accomplished thanks to Valqua’s legacy technologies: fluororesin processing technologies that Valqua
had accumulated over the years and reliability evaluation technologies, in which Valqua had pursued
developments in advanced technology fields including the atomic power and aerospace industries.
Recent years have seen a rapid transition not only in product development and functional evaluation, butalso toward a safer society. Under such circumstances, the supply of highly reliable products is notenough; more detailed technical information regarding the selection and use of products should be offered13

to customers. To do so, we should not rely on only conventional technologies and skills transfer, but should
establish more systematic training systems for further dissemination and utilization of our fundamental
technologies. Regarding long-term reliability evaluation, we need to expand the application of analysis
methods to new areas in the future.
Therefore, Valqua decided to become an“H & S company”to drive future growth:“H & S”stands for“H（hard = products）”and“S（soft = seal engineering service）.”
Maximization of customer value is essential for transforming into an H & S company. In doing so, weshould not prioritize only“hard”technologies. We should also expand our services to even the smallest
aspects in the product life cycle including elements closely associated with the product. In doing so, we
believe we can transform into a more rounded seal engineering company.
One example is the Seal Training Center（STC）. In 2014, STC was at our Nara Office（Nara）and MRT
Center（Machida, Tokyo）.
Malfunctions of bolted flange joints due to improper selection of gaskets and improper tightening of bolts
remain unresolved. As generations change, problems associated with the transfer of techniques and skills
from skilled engineers or workers to younger generations are emerging. Each plant is taking actions tochallenges to be solved.
To solve these problems, we should strive harder to disseminate sealing technologies. In addition,
regarding personnel training, we should offer systematic education and lectures including practice training

Spring 2017

tackle these problems, but providing education and training within each company also poses various

to personnel ranging from operators to operation managers and supervisors. This will enable us toNo.32

maintain and improve acceptable technologies and technological levels.
Personnel training based on these ideas has already become the norm in Europe and the U.S. The bolt
tightening method for bolted flange joints was standardized as EN1591-4 in Europe and ASME PCC-1 in
the U.S. Also, a technical certification system for bolt-tightening based on these standards is being started.
Our Seal Training Center（STC）observes these standards, and offers hands-on training for seal
operations. It also incorporates novel technical findings both in Japan and overseas.
Such approaches attract the attention of many users and are also highly evaluated by plant owners andpeople in the engineering field.
Our future corporate mission is not only to develop new products and supply them to the market but also
to offer various solution services for sealing and practical applications.
We will continue to provide the latest technical information to meet the needs of all customers throughValqua Technology News.
Senior Fellow Takahito Nishida

14

Contribution: Congratulations on the 90th Anniversary
Special Issue of Valqua’s Establishment
Let me express my sincere congratulations on the 90th anniversary special
issue. I have enjoyed reading this journal since 1993 when the journal’sname was different from the current Valqua Technology News（VTN）. At
that time, I met an engineer of Valqua for the first time, when he came to
my workplace at University of Yamanashi to learn about the trends of gasket and sealing
technologies in Europe and the U.S. I am also honored that VTN has published my articles several
times.
At that time, non-asbestos gaskets were being developed in the U.S., Canada, the U.K., and France,
but fugitive emissions occurred when the working fluid was a gas. Therefore, researchers wererequested to urgently do the following: introduce new gasket factors, collect data, and, using thegasket factors and collected data, establish methods for designing bolted flange connections which
met the standard leakage rate.
From 1989, I made presentations on my paper at the Pressure Vessels & Piping（PVP）Conferenceof the American Society of Mechanical Engineers（ASME）every year. I also participated in the

Spring 2017

Bolted Flange Connection Committee（BFC）of the Pressure Vessel Research Council. So, by
chance, I grasped the global trends and direction of research. The chairperson of BFC at that time
was Dr. K. H. Hsu, and I had kept a summary of his resume（on a slide）, so I gave a copy to theengineer. After exchanging information with the engineer several times, I asked Mr. Jim Payne, aNo.32

central figure in BFC’s research of bolted flange connection design, about the employee’s questions
while at the PVP Conference in 1994. He gave me his answers which I simply conveyed to theengineer.
Before asbestos regulations were introduced in 2008, asbestos gaskets had been the most widelyused gaskets in Japan. Although I don’t precisely remember the R&D situation for non-asbestos
gaskets at that time, Japan was probably isolated and in a very different environment from that inEurope and the U.S. However, amid such environment, the staff at Valqua studied newtechnologies in the U.S. based on the information summary which I had handed to the engineer andthey prepared for the development of non-asbestos gaskets in Japan.
Around 1997, I was appointed chairman of the Flange-Gasket Committee of the High Pressure
Institute of Japan, so I had more opportunities to learn about research on the sealing performanceof gaskets and bolted flange connections. In 1996, 1998, and 2000, engineers of Valqua participatedin the PVP Conference and gave presentations on their work. Mr. Payne of the U.S. had highexpectations for their presentations on gasket technologies. I also conducted several joint
researches with Valqua during my tenure at University of Yamanashi and Hiroshima University.
15

Valqua also received the attention of researchers from a major US petroleum company when
Valqua more recently presented papers at the PVP Conference related to our joint research on theanalysis of the mechanical behavior and sealing performance evaluation of bolted flange
connections with PTFE gaskets, as well as the stress analysis and sealing performance evaluationof bolted flange connections with larger nominal diameter.
The major research trends in Europe and the U.S. at present appear to be as follows: to develop
techniques for detecting fugitive emission amounts at levels ranging from 10−7 to 10−9 Pa m３/s and,due to environmental problems, to establish methods for the design and construction of bolted
flange connections. In addition, research and technological development of not only gaskets but
also overall bolted flange connections for establishing the following methods are required: amethod to design bolted flange connections and to develop gaskets for high-temperatureenvironments when a combined external load is applied; an efficient and reliable multiple-bolttightening method; and a method for preventive design and assembly for bolted flange connections
with larger nominal diameter. That is, the design and assembly of bolted flange connections

I believe that Valqua will continue to lead the world in the development and expansion of sealing
technologies.
Professor Emeritus at the University of Hiroshima

Toshiyuki Sawa

16

Spring 2017

including a more reliable bolt tightening method than the standard leakage rate is required.

No.32

Contribution:Evolving Gasketing and Sealing
Technologies
Let me express my congratulations on the 90th anniversary year since theestablishment of Nippon Valqua Industries, Ltd. I greatly respect everyone
who has supported industry through the development and manufacturing ofseal products for as long as 90 years. Valqua’s long history shows theimportance of seal products, and gaskets in particular, for industry.

I started research on gaskets about 20 years ago when I was transferred to the National Institute ofTechnology, Numazu College. At that time, research and standardization of the fugitive emissions ofgaskets was led by the Pressure Vessels Research Council in North America. This is when I started
a joint study on the leakage characteristics of gaskets together with Mr. Nishida, currently a senior
fellow, Mr. Asahina, currently an executive officer, and others. In the course of the study, we

Spring 2017
No.32

discovered that the leakage amount of a gasket is closely associated with its compression amount. It
was already known that the amount of leakage differs at the time of compression and unloading ofgaskets even when the same contact pressure is applied to the gasket. However, we found that thecorrelation between a gasket’s leakage amount and compression amount can be uniquelydetermined. Our finding was a significant achievement for evaluating the leakage characteristics ofa gasket.
We presented the results of this study at domestic and international academic conferences. Also,
Valqua Technology News featured our results in 2005. Our method for determining the leakage
amount of a gasket by using its compression amount was incorporated in JIS B 2490“Test method
for sealing behavior of gaskets for pipe flanges”in 2008. I am proud to have contributed to society
through the inclusion of our collaborative results in JIS.

Today, asbestos is no longer used in gaskets; gaskets are mainly made from heat-resistantfluororesin. These gaskets have excellent sealing performance and the leakage amount is much lessthan that of joint-sheet gaskets. Fluororesin gaskets can dramatically reduce gas emissions fromflanged joints of piping systems in plants including chemical plants into the environment. This lowemission property contributes to environmental protection. Methods for designing flanged joints
17were developed around 1940, and are still based on gasket factors. Although problems associatedwith the gasket factor（m, y）have been pointed out, the gasket factor is still used most frequently.
However, the design method is now transforming into a more reasonable design method for flanges
which appropriately takes the gasket’s leakage characteristics into account.

I am sure Valqua will continue to develop highly functional gaskets and prosper also as a supplier ofcomprehensive sealing technologies for flanged joints toward the coming 100th anniversary.

Professor at Mechanical Engineering, National Institute of Technology, Numazu College

Takashi Kobayashi

Spring 2017
No.32

18

Contribution: Congratulations on the 90th
Anniversary Year of the Founding
Valqua Review was inaugurated in 1957 to promote and introduce ourtechnologies under our core principle of value and quality, from which ourcompany derives its name. We take pride in our technologies and have worked
hard to develop various seal products ahead of other companies.
In this 90th anniversary issue, I would like to share with our valued readers
a summary of the products we have developed.
I joined Valqua in 1958 as Japan was emerging from the post-World War II era and as the economy
and society were starting to prosper. At that time, the energy source was switching from coal to oil.
Accordingly, petrochemical complexes were built all around Japan and the production of petroleum
derivatives started, creating a need for new seal products.
• Fluororesin Products
Fluororesin was developed in the U.S. and has unconventional heat and chemical resistance. We
noted the benefits and aimed to incorporate fluororesin products into our product lines. To achieve
this goal, we sent our employees to the U.S. in 1956, where they learned processing techniques, thenwe started to process fluororesin in our Atsugi plant for the first time in Japan. Thereafter, weSpring 2017

started to develop and market chemically resistant fluororesin lining pipes and lining vessels. Also,
we made use of the electrical characteristics of fluororesin, especially its high-frequency properties,
to produce electric parts, and started manufacturing and marketing these parts.
However, since fluororesin is a resin, it was difficult to use it on its own as a seal product. So, we
combined fluororesin with rubber, felt, and metal; designed the shapes of fluororesin products; andNo.32

then produced and marketed seal products (including envelop gaskets). We received DuPont's
prestigious Plunkett Award for our remarkable development of fluororesin products, and received
the award again later.
• Lineup of Rubber Products
Regarding rubber, which is a seal material, new types of rubber material were developed andmarketed one after another. Accordingly, training sessions on these newly developed rubbers andrubber additives were held, taught by various academics. We were lucky to attend such sessions tolearn about techniques for rubber. To fully investigate whether each of these various rubber materials
was suitable for use as a seal material, we combined each rubber material, vulcanized the combined
products, soaked them in various chemical solutions, analyzed the changes in swelling rate andphysical properties, and tabulated the results to determine whether the material could be used or not.
• Alternative Product to Asbestos
The major seal material since before WW II had been asbestos. Thanks to its heat resistance,
chemical resistance, and low cost, asbestos had been used not only for various seal materials but also
as a construction material. However, it was found that asbestos damages the respiratory organs, so
its use started to be banned. The ban was then extended to the seal industry, so we needed to19

develop non-asbestos products. The staff in our development department struggled to find appropriate
substitutes for asbestos for joint sheet, Valquatight Gasket（spiral wound gasket）, gland packing, andothers. But thanks to their efforts, substitute materials were found including carbon fiber, foamedcarbon, and aramid fiber. After repeated development and testing, our lineup of alternative products
was finally completed.
• Products Associated with the Nuclear Power Industry
Around 1970, nuclear power stations started to be built throughout Japan under the energy policy ofthat time. Accordingly, seal materials for the nuclear power industry were developed one after
another. Metal bellows, flectors, rubber boots, foamed-carbon products, inflation seals, and otherproducts were developed. Other industries then started to use these products; flectors were often
used as flexible joints for ducts of desulfurization equipment and NOx removal equipment.
• Automobile Industry
We have manufactured industrial braking systems since our establishment. As automobile technologies
changed, we led the way and developed unique products including a clutch facing for automobiles,
sealing-rubber products for electrical components（seals for harnesses）, and oil sheet gaskets.

As a pioneering company, we have also developed and manufactured industrial mechanical seals
domestically, and have focused on developing the main seal materials including mechanical seal

Spring 2017

• Mechanical Seals

materials for car coolers. We have also produced seal materials with excellent sealing properties
which can be used instead of gland packings.

No.32• Valve Production
We have long produced piston valves which used packings as seal materials. After the production offluororesin started, we developed ball valves which used fluororesin as a seal material for the chemicalindustry and other industries, and started production. Many chemical firms have since used our ballvalves. Also, for highly corrosive chemical solutions, we developed various lining valves made fromfluororesins, and also developed our unique, long-life, cylinder-type valves which can open and close
rapidly. These valves have been used in many iron-making machines and gas generators.
• Development of Corrosion-resistant Seal materials
Seal materials always come in contact with metals. When metal-corrosion problems at the contact
surface occurred in Japan, the need for corrosion-resistant seal materials emerged. So, we worked
with universities and other institutions to develop corrosion-resistant gaskets and packings. During
these projects, we identified corrosive elements in seal materials and optimized the mix of ingredientsand sealing properties ahead of other companies. Our pioneering achievements greatly influenced theconcept of seal materials thereafter.

20

• Development of Seals for Construction Machinery
During the construction boom, construction machinery was produced one after another. Most
machines were hydraulic-driven, and seals were used for most of the hydraulic machinery.
Conventionally, such seals used to be fabric-filled packings, in which rubber had been reinforced withcanvas and other fabrics. However, after the development of high-pressure-resistant urethane rubber,urethane U-packings became the main type. Urethane rubber has extraordinary mechanical strengthand abrasion resistance and is ideal for high-pressure hydraulic packings. So, we conducted functional
tests of urethane packings and decided to produce and market the product as an alternative to fabricfilled packings. At that time, we established Japan Elastollan Co., Ltd., a urethane manufacturer, toproduce urethane. Urethane rubber has rubber elasticity and can be used for injection and extrusion
molding. So, it started to be used for various purposes, including sport shoes and machine parts.
Around 1955, even a new plant had no experience in developing seals, so functional and verification
tests were required in order to develop seal materials. We could not build a plant only for these tests,
so we made a testing machine to conduct basic tests. However, eventually we needed to conduct
verification tests at actual plants. Fortunately, customers in those days let us conduct the final tests
at their plants and collect data. Thanks to their cooperation, we could establish our seal products. We
are deeply grateful for their steady support and will continue to appreciate them.

Spring 2017

This article described the transition of our seal product lineup and development activities sincearound 1955. I hope it was interesting.
NIPPON VALQUA INDUSTRIES, LTD.

former Managing Director （Technical Manager）

Takao Iwane

No.32

21

Contribution: Congratulations on the
Publication of the 90th Anniversary Special
Issue of Valqua Technology News
Let me express my congratulations on the publication of the 90th
anniversary special issue of Valqua Technology News to all the staff of thetechnology-development department of Nippon Valqua Industries, Ltd. I used
to work in that department, and so I am happy to see this anniversary.
In the research and development department, I used to study fluororesin. At that time, fluororesin
was introduced as a material for Valqua's seal products. I also conducted basic research, although I
probably spent longer in applied research and development.
In this article, I would like to share some of my experiences while working on application
development.
Thanks to its distinguished characteristics, fluororesin is used in many industrial fields including forsemiconductor manufacturing equipments, chemical plants, and automobile-related and electronic
components. Also, domestically manufactured fluororesin electric cable（Valflon electric cable）was
In development studies for geothermal power generation, cables for underground surveys are
required. These cables are used in volcanic areas, and so naturally, excellent heat resistance isrequired to tolerate the high temperatures found underground during exploration. At that time, theSpring 2017used to explore locations for geothermal power generation, a new energy.

best cable for this purpose was tetrafluoroethylene resin electric cable.
However, despite its excellent functions, tetrafluoroethylene resin was difficult to process, so weworked hard to devise a way to manufacture cables of several thousand meters. After great
difficulties, we adopted tape-wrapped cable.
We attached various sensors to the end of the cable. Then, along with electricians and the cable, we
explored trackless mountains in a volcanic zone. After safely arriving at the planned location forgeneration, we measured the temperature of hot hydrothermal water present several meters below
the ground along with the staff at the geological survey station. This was all a long time ago（about
40 years?）.
I also experienced on-site development activities. Once, we worked on developing components
including a chemical-resistant heater and solving problems at a production line of a major
semiconductor manufacturer which went on to lay the foundation of the current IT society. On
another occasion, we were posted to a steel-manufacturing site, where we were surrounded bystrong acids and alkalis contained in tanks lined with chemical-resistant fluororesin, piping
inspectors lined with chemical-resistant fluororesin, and other equipment. We proceeded with
22

No.32

development in this tough environment. These hard experiences now provide good memories.
Thanks to the support from many technology-development staff, we could carry out various
application development projects. As a result, we received the Plunkett Award four times. DuPont,
an American manufacturer which was the first to start producing fluororesin, gives the award to agroup which has done excellent work in application development. Our achievement was theculmination of continuous efforts by our excellent R&D staff and related parties, so I was delighted
to win the awards.
As we celebrate the prosperous 90th anniversary year, I look forward to further achievements fromthe technology-development department which will help Valqua to expand toward the coming 100th
anniversary.
NIPPON VALQUA INDUSTRIES, LTD. former Managing Director (Technical ･ Business development)

Yoshiaki Mori

Spring 2017
No.32

23

Contribution: Memories of My Tenure as CTO
Since joining Valqua as an executive officer in charge of development of
products and merchandise in November 2003, I have been working here foras long as 15 years including the last couple of years as a technical adviser.
During my 15-year career at Valqua, I worked as CTO for 4.5 years from
April 2010. Dr. Igarashi, my predecessor, has a broad knowledge and insightin chemistry ranging from basic to applied chemistry. I am grateful for all his
advice during my CTO days. Since I was focused on practical techniques, his advice was invaluable.
As his style as CTO was easygoing, I felt huge pressure when I was appointed as CTO. That was
the first time I truly realized and admired his elegant business style as CTO.
One of my most impressive memories is my first business trip to the Nara Office on my firstworking day at Valqua. The president at that time asked Mr. Joya, a managing director, to show mearound the office. I also had a chance to give a‘policy’speech in front of all the staff of the office. I
remember that I emphasized how R&D should contribute to company earnings. These days, theidea that company R&D should contribute to company earnings has become common, but at thatapproach was like that of public-sector research institutions. This situation was not limited toValqua; many companies had the same idea. So, when I emphasized profit-oriented R&D in my firstpolicy speech, the researchers were reluctant to accept it. My idea was too audacious at that time.
Meanwhile, the business trip was just one day, and I remember it well. Because the Nara Office islocated in the countryside, I had to change trains at Kyoto to the Kintetsu Line to get to the Nara
Office（it’s quicker to visit Shanghai！）. Thereafter, during my tenure as CTO, I visited Nara manytimes, but unfortunately I have never visited the area near the office other than Kashiharajinguu. I
hope to have the chance to travel there again.
In R&D, the creation and utilization of human networks are important along with personnel
training. Especially, in China, close cooperation with academics is indispensable in research anddevelopment. At that time, I had conducted joint studies with universities in Japan and Westerncountries, but not with Chinese academics. In Japan, there was much discussion as to the roles ofresearchers at public institutions including universities in terms of contributing to society. So, wecame to stipulate very specific results for the joint studies in advance. In contrast, there was nosuch discussion in China. When we explained the expected results to Chinese academics and tried
to set goals for an R&D program, they balked. This made me realize that we need to seriously
consider social and cultural backgrounds.
24

Spring 2017

time, it was considered that R&D should be pursued with a medium- to long-term vision. This

No.32

Recently, widely-applicable technological seeds are increasingly likely to come from totally different
fields than in the past. So, it is important for us to open the door for research and to deepen
communication with other companies and other R&D institutions. This gives researchers a global
perspective which allows research institutions to continue evolving into organizations which cancreate great value. Such a pursuit of continuous evolution is our never-ending challenge.
NIPPON VALQUA INDUSTRIES, LTD. former CTO

Spring 2017
No.32

25

Hiroyuki Kuroda

Technical Papers

Types and Application ofFiller-added PTFE Materials
The features of each filler-added PTFE are described

1. Introduction

below.
◦ Inorganic fillers

benefits including heat resistance, chemical resistance,◦ Glass fiber

insulation, non-stick, and low friction. Its scope of

Glass fiber has little effect on chemical and electricalapplication is broad: it is used in various fields including

properties. Glass fiber-added PTFE has approximately

semiconductor devices, chemical plants, automobiles,

twice the compression creep resistance and approximately

office equipment, and home appliances.

1000 times better abrasion resistance than pure PTFE.

However, PTFE suffers from inadequate abrasion

These features make glass fiber-added PTFE ideal forresistance and creep resistance, which are serious

improving abrasion resistance. The color is white,

disadvantages leading to severe self-damage in thewhich makes it easy to use. However, it might break acase where PTFE is used in sliding parts like shaft

counterpart shaft when used for shaft bearings.

bearings and large deformation in the case where one◦ Graphite

is used in load-bearing parts. The addition of a different

Graphite improves creep resistance and reduces initialmaterial, namely, filler, can alleviate these problems.

wear and starting resistance of PTFE. Graphite-added

This report described the types, features, and applications

PTFE has excellent thermal conductivity and chemicalof typical fillers.

resistance. It is less abrasive to the counterpart material,
so it is economically efficient, although its abrasion
resistance is not excellent.

2. Features◦ Carbon fiber２-1）Modifiable Features

Carbon fiber-added PTFE has excellent compressive

The addition of filler can modify features including
abrasion

resistance,

creep

resistance,

thermalconductivity, and coefficient of linear expansion. Modified

Table1
Filler type
Glass ﬁber

PTFE has approximately 1000 times stronger abrasion
resistance, twice the creep resistance, and up to twice
the thermal conductivity of pure PTFE. The optimal
filler should be selected depending on the desired
modification.

Glass ﬁber +graphite
Glass ﬁber +MoS2GraphiteBronze２-2）Types of Filler

Bronze + carbon ﬁber
Carbon graphite

Typical fillers include inorganic fillers such as glass

Carbon ﬁber

fiber, graphite, molybdenum disulfide, and bronze.

Organic ﬁller

Organic fillers are also used.

Types and features of fillers ３）
Identifying symbol Characteristics
Excellent abrasion resistanceExcellent electrical characteristics
Attached by alkali
Poor abrasion resistance in water
Excellent creep resistance
Improves sliding properties
Excellent creep resistance and compression strength
Improves sliding properties
Excellent electrical insulation
Excellent sliding properties
Does not attach to soft opposite materials
Excellent creep resistance and compression strength
Excellent heat conductivity
Excellent sliding properties in oil
Excellent creep resistance and load
bearing properties at high temperatures
Excellent sliding property in water
Excellent creep resistance
Does not attach to soft opposite materials
Stable sliding properties
Excellent creep resistance and compression strength26

Spring 2017

Among plastic-based materials, PTFE offers diverse

No.32

Types and Application of Filler-added PTFE Materials

Table2Item
Filler content

Unit

ASTM
measuring method Pure PTFE

Amount %List of filler-added PTFE properties ３）
Filler identifying symbol

Glass ﬁber Glass ﬁber

Glass ﬁber

Compression strength Bending strength Compression creep

Speciﬁc gravity
TensionStretchGlass ﬁber
Graphite

Glass ﬁber

GraphiteBronzeCarbon/Carbon/Carbon ﬁber
graphite 25% graphite 33%

Permanent
deformation(after 24 hours)

0.2%
oﬀset

Modulus of elasticity

0.2%
oﬀset
Modulus ofelasticity
Hardness
Durometer
Impact strength (izod)
Heat conductivity
Linear expansion coeﬃcient

Water absorption rate
Limit PV value

Coeﬃcient of abrasion(in air, after 50 hours)(in water, after 50 hours)

Measuring with
Matsubara-type
test instrument

Coeﬃcient of dynamic friction(after 50 hours)
Coeﬃcient of static friction

Spring 2017
No.32

strength, creep characteristics, and abrasion resistance.

◦ Organic fillers

These features are significantly improved in the high-◦ Polymide-based resin

temperature region above 200°
C. It also has excellent

Polymide based resin-added PTFE is beneficial in thesliding characteristics and good chemical resistance incase where soft metal moving parts that are likely towater. It offers excellent sliding characteristics in

be damaged by carbon-added or graphite-added PTFE

fluids of low lubricity including acid and alkaline fluids.

are used as a counterpart material.

◦ Molybdenum disulfide◦ Polyphenylene sulfide-based resin

Molybdenum disulfide-added PTFE has improved

Polyphenylene sulfide-added PTFE has creep resistancecreep resistance and lubrication. It does not degradeand dimensional stability.

electrical insulation, so it can be used for electrical◦ Aromatic polyester-based resin

usages. However, molybdenum disulfide is rarely

Aromatic polyester based resin-added PTFE has improved

added to PTFE as a single filler; it is added along withmechanical characteristics including compression andglass fiber and bronze.

bending, as well as stable sliding.

◦ Bronze
Bronze-added PTFE has significantly improved abrasion

Like these examples, there are many types of filler. An

resistance, compressive strength, creep resistance,

appropriate filler should be selected depending on thehardness, and dimensional stability. It tends to retain

usage conditions including load, sliding speed, lifespan,

oil on sliding surfaces, and has excellent abrasion

frictional

resistance under oil lubrication, so it can be used for oil

expansion,

lubrication usages. However, it is important to note

properties.

that bronze-added PTFE is not suitable for electrical

Although pure PTFE is white, some fillers turn PTFE

and chemical applications.

black or dark brown. These conditions should be27

conditions,counterpart

corrosion

resistance,material,
andlinearelectricalTechnical Papers

considered depending on the position of use and the

The type of filler determines the improvement inapplication.

characteristics of PTFE. We hope the above explanationof various fillers will help our readers when selecting a

3. Conclusion
PTFE has excellent chemical characteristics, sliding
properties and non-stick, making it suitable for shaft
bearings and sliding parts. In the case where filler isadded to PTFE, the PTFE gains improved frictional andmaterial.

4. Reference１）Takaharu Ikeda. VALQUA Review; Vol.35, No.1
(1991)

creep characteristics, making it suitable for mechanical２）Takaomi Satokawa. Fluororesin Handbook

purposes.

３）VALQUA Handbook

Youichiro Wada

Spring 2017

Corporate Research and Development Group
Development DivisionHigh Performance Plastics Development Division

No.32

28

Accuracy and Mold Direction of
PTFE Products
1. Introduction

Table1

G eneral tolerance for polytetrafluoroethylene（machine cut）
Unit: mm

In general, the accuracy of PTFE product is not easy to

Grade 1

Grade 2higher than that of metals, and its one of volume transition

1

up to

16

±0.1

±0.3

More than 16

up to

40

±0.2

±0.6

temperature is around room temperature causes volume

More than 40

up to

63

±0.3

±0.8

More than 63

up to

100

±0.4

±1.0

More than 100

up to

160

±0.5

±1.2

More than 160

up to

250

±0.6

±1.4

because not only PTFE is flexible and elastic material,

More than 250

up to

400

±0.7

±1.7

but also residual stress remains after molding sometimes

More than 400

up to

630

±1.0

±2.0

More than 630

up to 1000

±1.5

±2.5

control because its coefficient of linear expansion ischanges approximately 1 to 2%. Moreover, thin-walled
PTFE products are known to be difficult to machining

Spring 2017
No.32

Tolerance

Categories of nominal
dimension

deform due to frictional heat generated during themachining process or due to aging after machining. Suchbe taken into account:deformation could influence dimensional accuracy.

1. PTFE has low thermal conductivity.

Regarding processing accuracy, PTFE products are

2. PTFE has a high coefficient of linear expansion.

sometimes required the same permissible dimensional

3. PTFE’s volume changes markedly（by approximately

tolerance as for a metal material. In such cases, the

1 to 2%）at around 23°C.

characteristics of PTFE described above could cause

4. PTFE is elastic.

troubles between users and manufacturers. With this

5. PTFE sometimes has residual stress.

background, this report explains the processing
accuracy of PTFE.

From the above, PTFE’s dimensional minimum
tolerance is approximately ±0.05 mm or half the value

2. General Permissible
Dimensional Tolerance

stipulated in JIS K 6884（grade 1）, although PTFE’smachining accuracy depends on the size and shape.
However, because of PTFE’s elasticity, an accurate

Table 1 shows“General Tolerance for Polytetrafluoroethylene

value could be varied if the end of a measuring device（Machine Cut）”stipulated in JIS K 6884-1971.

is pushed strongly against a PTFE specimen. For

This standard stipulates dimensions ranging from 1

example, a difference of at least 0.1 mm in measured

mm to 1000 mm for when the material of a PTFE

values sometimes occurs depending on how amolded product is machined through compression or

micrometer is pushed against a PTFE specimen. Users

extrusion molding. The term“general”used in thisand manufacturers should consider this point.

standard means that the standard can be applied whena blueprint shows no figures or symbols.
When measuring the processing accuracy of PTFE,
the following essential characteristics of PTFE should
29

Technical Papers

3. Effects of Annealing Treatment
Usually, free sintering (baking) process is applied toTable2Categories of roughness

New JIS symbol
Symbol Arithmetical mean roughness

Former JIS symbol
Applicability standard
for machining
Symbol Maximum roughness

12.5 to 25 a

50 to 100 S

3.2 to 6.3 a

12.5 to 25 S

Acceptable

PTFE after compression molding. During sintering,

Acceptable

PTFE’s internal stress could be decreased compare

0.4 to 1.6 a

1.6 to 6.3 S

with molded products with coining process (a process（Conditionally acceptable,in the case of sheet）

0.012 to 0.2 a

0.05 to 0.8 S

Unacceptablein which a material is sintered in a mold and then（Unit:μm）

cooled under pressure) whose outer layer is quenched.
However, annealing* treatment is applied to the

The comparison of the two symbol types（new andmaterial in case high dimensional accuracy is required

former JIS symbols）shown in Table 2 is not strictlyor the product shape is complex.

precise; it is shown for convenience. Even today, many

Eliminating the internal stress generated during

companies continue to use the former JIS symbols.

molding process is an effective way to improve

The former symbols were introduced approximately

dimensional accuracy and to prevent from its change

60 years ago, and so are well known. It will take timeover time.

for the new symbols to become known among
peripheral manufacturers. In addition, in the case offunctional parts, existing techniques tend to be

are slowly cooled at a given temperature to remove

followed. Therefore, it is important to understand theinternal stress generated by heat or mechanicalrelationship between the new and former symbols.

Spring 2017

*Annealing: A procedure in which molded products

stress.
Roughness profile

4. Surface Roughness
AsstipulatedinGeneral ToleranceforPolytetrafluoroethylene（Machine Cut）
, material characteristics should be taken

No.32

into account when setting a surface-roughness value.
Since resin is affected by heat during machining on thesurface and has elasticity, the surface-roughness value

Figure1

Type of surface roughness: calculated
average roughness（Ra）

could not equal to the machined metal surface.
Generally, a difference in the finish of surface roughness
Peak line

is caused by the machining conditions including
rotational and feeding speed and cutting tools（blades）.
Table 2: Standard values of surface roughness of PTFE
Figure 1: Calculated average roughness（Ra）

Valley line

Figure 2: Maximum peak（Rmax）

Note:In calculating Ry, only the average roughness profile area inreference length should be used, because too high or low peaks
might be caused by abnormal reason such as scratch.

Figure 3: A machining method for round bars andFigure2Type of surface roughness: maximum peak（Rmax）

sleevesFigure 4: A machining method for sheet (plate material)

30

Accuracy and Mold Direction of PTFE Products

molding is called the molding direction（MD）,while thedirection perpendicular to MD is called the crosssectional direction（CD）.
Some PTFE materials are filled PTFE whose material
is mixed with filler. Since fibrous filler orients duringmolding, and has markedly different physical properties
from those of PTFE, filled PTFE should be designed
and used with caution.
Figure3

The following are characteristics that are changed in

Machining of outside diameter

filled PTFE.
Compression-creep characteristics:
	The MD value becomes greater than the CD
value.
Tensile strength and elongation:
	MD tensile strength becomes greater thanCD tensile strength. CD elongation becomes
greater than MD elongation.

Figure4

Spring 2017
No.32

Coefficient of linear expansion:

Machining of a surface

	The MD value becomes greater than the CD
value.

5. Direction of Molded Products

When material shapes are sleeves and rods, theMolded PTFE products have various directions

molding direction can be visually confirmed, and so thedepending on their molding methods, and the direction

processing can be started based on the direction.

influences the physical properties. One of the common

However, when the material shapes are plates andmolding methods for PTFE is the compression molding

complex processing is required, it is necessary tomethod, as shown in Figure 5.

visualize the direction including marking the direction
during the initial processing stage.

Material

6. Conclusion

PowderPTFE is chemically inactive, has excellent chemical
resistance, can be used at a wide range of temperature,and has the lowest friction coefficient among solidMoldmaterials, and so has been used for various purposes.

Press
Raw material input

Figure5Compression molding

Baking

The compression molding method

Also, PTFE is much easier to machine than metals. It
is also relatively softer than other resins and has goodaffinity when combined with other materials for use.

In the compression molding method, the material is

Recently, many PTFE products have also been used inplaced in a mold and force is applied from both above

the precision-instrument industry, and so stricter

and below the mold to press the material together.

dimensional accuracy is required. We will developThis generates directionality. The direction towardmachining techniques in line with the accelerating

the compressed side in the material at the time ofprogress of machine tools and industrial tools. To do

31

Technical Papers

this, we will ask users and manufacturers for theirrequests for dimensional accuracy and tolerances
according to their intended uses.

7. References
1. Valqua Handbook, Technology Ver., September 2010
2. F luororesin DuPont™ Teflon Handbook, Du PontMitsui Fluorochemicals Company, Ltd.
3. JIS K 6884-1971

Shigeko Kawai

Nobuyuki Ota

Corporate Research andDevelopment Group
Development DivisionHigh Performance
Plastics Development
Division
Technical
Service Section No.3

Corporate Research andDevelopment Group
Development DivisionHigh Performance
Plastics Development
Division
Technical
Service Section No.3

Spring 2017
No.32

Correction and apology
VALQUA would like to announce and apologize for a partial
correction to“Explanation on PTFE Linear Expansion
Coefficient,”3. Example calculation for dimensional correction
in VALQUA Technology New Summer No. 31.
Incorrect: Dimensional change
Incorrect:Dimensional change＝1000×（100－0）×20×10−5＝20
Correct:Dimensional change＝1000×（0－25）
×20×10−5＝−5
Therefore, the length at 0°C is 995 mm (shrunk).

32

Introduction and Utilization of Seal Quick
Searcher®
（SQS）– Gasket Version –conditions, and engineers from all industries can use this

1. Introduction

service. Basic instructions on how to use SQS are given

In 2014, we launched Seal Quick Searcher （SQS）on

below; please refer to them when using our website andour website, which is used to search for available seal

system.

®

products. Through SQS, customers can select industrial
seal products and find troubleshooting methods. The
website search system is designed for engineers who
do not have expertise in gaskets, to allow them toeasily find necessary technical information. The

3. How to Use Seal Quick Searcher®
（SQS）①Search by Fluid Group & Type,	   Temperature, and Pressure

Spring 2017

website also provides technical information in the

One of SQS’s key functions is the ability to search

desired format.

recommended seal products which meet specified

Since SQS was launched, we have received very

conditions. By using this function, anyone can selectpositive feedback from customers. The search system

gaskets based on fluid group & type, temperature, andis now available in not only Japanese but also English

pressure. The following pages describe how to searchand Chinese.

recommended products.

2. What is Seal Quick Searcher®
（SQS）?

No.32

3-1）How to Access Seal Quick Searcher®
（SQS）
Click the“Seal Quick Searcher®”button on our website.

Seal Quick Searcher （SQS）is a search service that®

enables users to find our recommended seal products
in various ways. When searching for industrial seal
products, users can set certain search conditions
including not only fluid group & type, temperature,and pressure but also keywords and industries. We
have also put our accumulated know-how online in aFrequently Asked Question（FAQ）format. Through
SQS, users can calculate bolt tightening force, select anappropriate pressure rating, and search for items
equivalent to non-Valqua products, catalogs, and① Click the

button.

Valqua Handbook in real time.
In addition, users can select gaskets based on actual
usage conditions. If they use SQS and search for solutions

3-2）How to Access“Gasket Search”

to troubles that have happened at their workplace, theClick the“Gasket Search”button on the“Seal Quick

website can offer troubleshooting suggestions. Of course,

Searcher®
（SQS）”page.

the system fully covers inquiries about products and33

Technical Papers⑤ Input temperature and pressure.
Note:To automatically input temperature and pressure,click the desired temperature point on the graph.
⑥ Finally, click the

button.

3-5）How to Retrieve and Confirm theSelection Results② Click the

button.

After clicking the“Retrieval”button, product search
results are displayed below the graph.

3-3）How to Access“Search by Fluid,
Temperature, and Pressure”
Click the“Search by Fluid, Temperature, and Pressure”
button on the“Gasket Search”page.

Spring 2017

③ Click the

button.

3-4）How to Set Search Conditions⑦ The results can be downloaded in PDF format.

Select a fluid group and type, and input temperature⑧ The search conditions are displayed.

and pressure on the“Recommended Gasket Search”⑨ Recommended gaskets are extracted on the basis of thesearch conditions. Then the recommended products
and its upper and lower groups are displayed.
Refer to the following explanation regarding upper andlower groups.
After clicking the product number displayed in the“Selection Results”section, the page switches to a
new page displaying detailed information on theselected product.

page.
Through this intuitive setting of conditions, users canrepeatedly search for products with simple mouse
operations.

Explanation

The term“upper group”represents a group of gaskets
covering a wider range of temperature and pressure
than the recommended gaskets extracted on the basisofdesignatedconditions.

When

the

designatedconditions are near the usable limit of the recommended
products and sufficient margin is desired to ensure
proper functioning, the upper-group information is a
useful reference.
④ Select a fluid group.
Note:Inverted red display represents the selected fluidgroup.

The term“lower group”represents a group of gaskets
covering a narrower range of temperature andpressure than the recommended gaskets extracted on
34

No.32

Introduction and Utilization of Seal Quick Searcher®
（SQS）– Gasket Version –the basis of designated conditions. Therefore, generally,
lower-group products should not be used when the
product is used under the designated conditions.
However, a lower-group product may be used under② The search can be conducted by entering a key word
（partial key words are acceptable）.
③ Also, a search can be conducted by selecting a productnumber from a list of other manufacturers.

limited conditions, such as for a short period including

Note:
“Gasket Search results”displays“Recommended”

trial operation or when a change in conditions isand“Suggested”products. Each type of product isrecommended on the following basis.

planned. The lower-group information may then be a

Recommended product:A product with similar materials

useful reference.

and usable range

4. How to use Seal Quick Searcher®
（SQS）②Find an Item Equivalent to a nonValqua Item with Product Number

Suggested product:A product which has a partly different

Users can use information for a non-Valqua product to

5.  How to Use Seal Quick Searcher®
（SQS）   ③Calculation of Gasket Tightening Forcefind the equivalent Valqua gasket.

color tone and usable range, but canprobably be used.

Spring 20174-1）How to Access“Equivalent Item Search”

Seal

Click the“Equivalent Item Search（Including Productinformation and useful tools for using our products.

No.）”button on the“Gasket Search”page.

This section introduces one such tool and explains how

Quick

Searcher® （SQS） provides

various

to use it to calculate the tightening force.
5-1）How to Access“Support Tools”
Click the“Support Tools”button on the“Seal Quick
Searcher®
（SQS）”page.

No.32① Click the

button .

4-2）How to Set Search Conditions
Set search conditions on the “Search for items
equivalent to Valqua’s gasket from other company’sproducts”page.
Either the“Search by entering a key word”or“Searchfrom a product number from a list of other manufacturers”
is available.

① Click the

35

button.

Technical Papers5-2）How to Access the “Tightening Force
Calculator”
Click the“Tightening Force Calculator”button on the“Support Tools”page.
⑤Input the operating pressure, bolt nominal diameter, andbolt quantity, which are to be calculated.
⑥ Finally, click the

button.

5-5）How to Display Calculation Results② Click the

button.

The results of the tightening-force calculation aredisplayed as follows.
Also, the results can be downloaded as a PDF.

5-3）How to Set Calculation Conditions ①
Select a product and input the dimensions on theupper part of the“Tightening Force Calculator”page.

Spring 2017
No.32

③Select the product number of the product which is to be
calculated.
④ Refer to the illustration and input the internal andoutside diameters of the contact zone.
Especially, in the case of spiral wound gaskets,
attention should be paid to the position of the gasket’soutside diameter when measuring the diameter.

5-4）How to Set Calculation Conditions②
Input the operating pressure, bolt nominal diameter,
and bolt quantity, which are to be calculated, on thelower part of the“Tightening Force Calculator”page.
Then, click the“Calculation”button.

⑦ The value calculated through the following processes:
Wm1 and Wm2 stipulated in JIS B8265 are used in thiscalculation, are compared, and the higher value isdisplayed.
⑧ The value calculated based on our recommended gasket
stress is displayed（in the case of a liquid seal）.
⑨The value calculated based on our recommended gasket stress is
displayed（in the case of a gas atmospheric seal）.

36

Introduction and Utilization of Seal Quick Searcher®
（SQS）– Gasket Version –⑩The value calculated based on the allowable gasket stressof the gasket is displayed.
⑪ The value calculated through the following processes: The
value is calculated according to JIS. Then the obtained
value is compared with our recommended stress and thehigher value is displayed as the final calculation result.

6. Conclusion
This report introduced some of the functions of our
Seal Quick Searcher®（SQS）. We hope you will use
SQS for your business. We will continue to improve
the functions to meet our valued customers’needs.

Toshihiko Enishi
Sales Group
Technical Solution Division

Spring 2017
No.32

37

Technical Papers

Causes of and Countermeasures for
Allophone Trouble in a Piston Seal
System for Cylinders
1. Introduction
In recent years, to accommodate requests regarding

2. Example of Packing Structurefor Hydraulic Cylinders

hydraulic machinery, hydraulic systems have been

Generally, several packing and parts are used in high-streamlined by increasing the operating pressure andpressure cylinders including cylinders for hydraulictemperature and reducing the size and weight ofshovels. Figure1 illustrated the structure of a high-hydraulic systems. Accordingly, the performancepressure cylinder.

requirements of hydraulic cylinders including packingsRodfor hydraulic cylinders have changed, and so the

parts
Pisto

performance of various packings has been improved.

n pa

rts

Spring 2017

We have developed a seal system for high-pressure
cylinders as a maintenance kit for cylinders for hydraulicshovels in the construction machinery industry. Whenevaluating actual equipment during the development
stage, we found that allophone（stick-slip phenomenon）
occurs in cylinders under certain conditions. During

Figure1

Structure of a hydraulic cylinder

allophone of the cylinder, a stick-slip phenomenon

２-1）Structure of Seal System in the Rod Segment

occurs at the contact zone of a reciprocating packing,The packing used in the rod segment plays an

causing abnormal noise and oscillation while the cylinder

important role in preventing external leakage, and isis moving. Such allophone is a problem of hydraulican important function of cylinders. Figure 2 illustrated

cylinders.

the structure of the seal system in the rod segment.

This report describes an allophone trouble and its

Table1 showed the component parts.

solution. In this particular case, we considered that theallophone trouble was caused by the defective formationof an oil film at the contact zone between the packing andits opposing face, so we designed the packing to improve
its ability to absorb the oil film.

⑵ U-shaped packing
Backup ring for
u-shaped packing⑴ Buffer ring⑶ Dust seal

Figure2

Structure of seal system in the rod segment

38

No.32

Causes of and Countermeasures for Allophone Trouble in a Piston Seal System for Cylinders

Table1 List of component parts of the seal system in the rod segment

Table2 List of component parts of the seal system in the piston segment（１）Buffer ring（４）Piston seal
The main component that maintains the oilpressure inside the cylinder for operation. Its
components are as follows:①：Sliding ring to enhance the tribologicalproperties②：Rubber back ring to ensure tight sealing③：Backup ring to support the pressure
resistance

Absorbs the initial high pressure to reduce
the strain on the u-shaped packing. The
pressure resistance is enhanced by the use of
the backup ring in reinforced plastic.
（２）U-shaped packing
The main sealing component to prevent fluid
leakage. The pressure resistance is enhancedby the use of the backup ring in reinforced
plastic.

（５）Wear ring
Functions as a bearing when the piston is inmotion. Typically made of cloth-reinforced
phenolic plastics.

（３）Dust seal
（６）Sliding ring

Spring 2017

This packing prevents the infiltration of external
contaminants such as sand and gravel. It also
helps to ensure the prevention of minor leakage
from the u-shaped packing.

Prevents the contaminants in the oil frominfiltrating the piston seal. Typically made of
Polytetrafluoroethylene (PTFE).

２-2）Structure of Seal System in the Piston Segment

resistance）acts on the contact surface. The stick-slip

The packing used in the piston segment retains

phenomenon is when both stick and slip conditions

hydraulic pressure and provides appropriate thrustoccur instantaneously and cyclically on the contact

and load-retention ability to move the cylinder.2）Figure

surface.２,３）

3 illustrated the structure of the seal system in theThis phenomenon occurs in hydraulic cylinders mainly

piston segment. Table 2 showed the component parts.

at low speed, and sometimes causes troubles such as
noise and oscillation. This noise is called allophone.２,４）⑷ Piston seal
⑹ Sliding ring⑸ Wear ring

4. Evaluation of Allophone

No.32

We have developed a seal system for high-pressure
cylinders. We mounted actual equipment in a cylinderof a hydraulic shovel to conduct an operation test ofthecylinder.

Asaresult,allophone （stick-slip

phenomenon） occurred in the cylinder when theshovel was operated at low speed and when the oil
Figure3

Structure of seal system in the piston segment

temperature was high. However, we did not confirm
allophone at the lab evaluation during development.

3. Allophone（Stick-slip Phenomenon）

This meant that the operating conditions of the actual
equipment had not been recreated, and revealed the
difficulty of evaluating allophone.

Static and kinetic frictional forces act on the contact
surface between the packing and the opposing face;

4-1）Lab Evaluation

the two forces are closely interrelated. Sticking is the

We conducted lab evaluation（stick-slip test）of a sealcondition in which static frictional force （starting

systemresistance）acts on the contact surface, and slipping isdevelopment stage under the conditions shown inthe condition in which kinetic frictional force（sliding

Table 3. The test results showed no allophone or stick-

39

for

high-pressure

cylinders

duringtheTechnical Papers

slip phenomena.
It is difficult to conduct a quantitative assessment of
the stick-slip phenomenon; we need to precisely

5. Relationship between Stick
Slip and Oil Film on Packing

replicate the usage conditions and environment inPoor lubrication and frictional resistance at the contact

order to fully understand the characteristics of thesurface affect the stick-slip phenomenon on packing.

packing, and then to plan and conduct a test. However,That is, periodical and recurring cycles of sticking andin the lab evaluation, the operating conditions including

slipping at a contact surface cause the phenomenon. In

the cylinder’s transverse load and high oil temperature

the sticking condition of the cycle, the packing deforms

had not been replicated.

itself to remain in the original position, and tries to４）

Table3Oiltemperature

return to its original shape when it is forcefully slipped

Conditions for stick-slip test

Parameterby an external force, etc. The stick-slip phenomenon of

Testing conditions
Ambient temperature (temperature without
artificial control: approximately 40°C)

the packing is affected by various factors including

Velocity

0.01 m/sec

temperature, speed, pressure, surface roughness,

Weight25 kg

viscosity of hydraulic oil, and oiliness. Although theseLubricantVerification
methodHydraulic lubricant (kinetic viscosity at 40°C:
46.0 mm2/sec)
Verification is based on the wave form depictedin the accelerometer measuring the up/down
movements of the cylinder.

factors have not been quantitatively investigated,
qualitatively, the low viscosity of hydraulic oil oftencauses rupture of the lubricating film when equipment
is operated at low speed under high pressure andAccelerometer
WeightTo alleviate the stick-slip phenomenon of a packing,the overall frictional resistance is sometimes lowered.

Laser displacement sensor

One way to do this is to improve the retention of oil
film between the opposing face and sliding surface.２）

Spring 2017

when insufficient lubricant is applied.５）

Atmosphere
Up/down motion5-1）Formation of Oil Film on Packing
Regarding retention of an appropriate oil film on thesliding surface of a common reciprocating packing, thepressure gradient of the pressure pattern on the sideof the fluid inlet and the same pressure gradient on the

Cylinderside of atmosphere are closely interrelated.６）Absorption
Figure 4

or scraping of the oil film may occur depending on the

Equipment for stick-slip test

angle of the pressure gradient; this absorption and

加速度(G)
Acceleration
rate (G)0.04

scraping affects the thickness of the oil film and sealing
properties.

0.02

In the process of developing a high-pressure rod seal
（U-packing）, we focused on the shape of the packing

0on the heel side and the pressure gradient of pressure-0.02

patterns in the heel segment. We verified that a seal
with excellent absorbability could be developed by

-0.04
0

50
Sliding摺動距離(mm)distance (mm)Figure5

Results of stick-slip test100

setting both the shape and the pressure gradient to
optimal values.１）

40

No.32

Causes of and Countermeasures for Allophone Trouble in a Piston Seal System for Cylinders5-2）Application of Forming Method of Oil Filmto a Piston Seal System（FEA）. As a result, greater peak contact pressure
and a sharper pressure gradient were confirmed in the

In the cylinder in which allophone occurred, the rod

C-chamfer at both ends.

seal system of the cylinder used a U-packing developed

It was found that the developed U-packing had functions

by Valqua, and an appropriate oil film was retainedof both scraping and absorbing the oil film. As abetween the opposing face and sliding surface. Taking

countermeasure against problems associated with thethese conditions into consideration, we assumed that

C-chamfer, the U-packing was applied to the system toallophone occurred in the piston seal system.

make use of the two functions. Table4 shows the results

Lipof the analysis and investigation of the countermeasure.

Heel

Innerdiameterside
Chamfer surface[Fluid side]
Surfacepressure
distribution

The absorbability of the U-packing was used in shaping
both ends of the wear ring into an R-shape to form anappropriate oil film on the sliding surface. No allophonePeak

was confirmed in an allophone evaluation of actual[Atmosphericside]

Based on this result, we consider that an appropriate

equipment in which this wear ring was provided.
oil film was formed.

[Fluid side]
Lip

Innerdiameterside

Surfacepressure
distribution

Heel

Spring 2017

Table4[Atmospheric
side]

No.32

 esults of analysis of wear ring and investigationRon countermeasure

Parameter

Chamfering (edge)
Chamfer surface

and when transverse load was applied to the piston
seal system. When transverse load was applied to a

Round

Chamfersurface
Localized surfacepressure peaks appear in
the chamfer surface ofthe edges.

The results of allophone evaluation of actual equipment
viscosity of the oil was low due to high oil temperature

Alternative productevaluation results

Edge
form

Figure6 T echnique to absorb oil film used in thedeveloped productsuggested that allophone occurred both when the

Analysis outcomes

Surfacepressure
distributionof sliding
surface

Reduces the pressure
gradient by applying
rounded chamfering on
the edges.
Moderatepressure gradient

Fluid pressure
peak[Fluid side][Fluid side]

shaft bearing, wear ring of the shaft bearing wasstrongly pushed to the opposing face, and then thecontact pressure reached its maximum value. As a

[Piston seal side]

result, the pressure gradient of pressure patterns ispresumed to have become sharper, too. Therefore, we
consider that allophone was caused by higher frictional
resistance due to scraping of the oil film by the wearring.
To verify this hypothesis, the pressure pattern of thewear ring was confirmed by finite element analysis
41

Material
properties[Piston seal side]

Glass-fiber reinforced nylon. Based on the cost factor,
It is stronger and more cost the raw material will noteffective than conventional be replaced.
materials such as PTFE andcloth-reinforced
phenolic
plastics. It is inferior to PTFE
in its frictional characteristics.
Thus, some products havethe sliding surface treatedwith knurling.２）

Technical Papers

6. Allophone Evaluation of
Cylinders of Actual Equipment

cylinders.
To retain an appropriate oil film, the functions ofscraping and absorbing the oil film are essential. By
understanding these functions, this technique can be

hydraulictheapplied to other products to reduce allophone andcountermeasure described above. Figure7 showed thefrictional resistance. However, we still do not have afrequency of the allophone sound. No allophone wave

quantitative

shape was confirmed in the evaluation after taking theappropriate thickness of oil film for each product, andcountermeasure.

other factors, and many challenges remain. Therefore,

shovelbeforeandaftertaking

The waveform of the squeak is identified in the diagram below.

understanding

of

usage

conditions,further product development is needed for verification.

8. References

Frequency

１）Yamashita, J., Valqua Technology News No. 30, 2016,
Time
The waveform of the squeak is not identified in the diagram below.

pp. 3–8２）Ando, T., Hydraulics & Pneumatics, May 2003, pp.
28–33３）Nakano, K., Journal of the Society of Rubber Science

Frequency

and Technology, Vol. 80, 4th issue, 2007, pp. 134–139
4）Takamure, T., Tsuji, K., Muramatsu, A., and Yoshida,
Time

Figure7

Allophone evaluation of cylinders

7. Conclusion

T., Hydraulics & Pneumatics, May 2003, pp. 34–37
5）Akai, H., Hydraulics & Pneumatics, May 2003, pp.
13–20

Spring 2017

After countermeasure application Before countermeasure application

An allophone evaluation was conducted with an actual6）Kaneda, S., Journal of the Society of Rubber Scienceand Technology, Vol. 72, 4th issue, 1999, pp. 194–201

This study verified that retention of an appropriate oilfilm alleviated allophone in packings for hydraulickenichi Takahashi
Corporate Research andDevelopment Group
Development Division

42

No.32

Sticking Troubles of O-Rings andCountermeasures
1. Introduction
The rubber O-ring is a seal used for both static seal
products （gaskets） and dynamic seal products２-1）Sticking of O-rings（packings）. It is made with soft elastomer, and so fits well

When a rubber O-ring contacts with its opposing face,to opposing faces and allows sealing with little tightening

such as a metal surface, under pressure, it sometimes

force. The O-ring also has the following other benefits:

sticks to the face. When the sticking strength of this

• It can be used in various conditions, from highphenomenon is small, the phenomenon is sometimes

pressure to low pressure.

Spring 2017
No.32

2. Sticking Phenomenon and
its Causes

called adhesion. Depending on the usage condition, it• It requires little space for mounting.

may stick sufficiently strongly to cause material• The structure of the mounting section is simple,

destruction of the rubber upon removal. In the case of

making mounting easy.

static seal products, the sealing properties themselves• It is standardized, readily available, and low cost.

rarely cause problems even if sticking occurs.

Thanks to these benefits, the rubber O-ring is the mostHowever, sticking may result in a）a very large force

widely used general seal product in various equipment

required to open flanges at changing O-rings, and b）

and devices in a wide range of industries including thein the case of a large-bore O-ring, the flanges cannot

automobile, hydro-pneumatic, machine-tool, food,be opened due to the large contact area with thesemiconductor, and aerospace industries.

opposing face, which creates substantial sticking force.

Rubber is an inherently elastic material and so recovers

Also, maintenance problems may occur, such as

to its original shape. In addition to elasticity, rubber has

cleaning difficulties if the sticking rubber ruptures:

non-slip, sticky properties. With these useful

the ruptured rubber sticks to the grooves andcharacteristics, rubber is used to produce tires, hoses,

opposing faces when flanges are opened.

belts, and so on. On the other hand, these characteristics

On the other hand, in the case of dynamic seal

could cause malfunction cases when handling products,

products, sticking may cause O-rings to detach from asuch as difficulties in mounting and dismounting. In thegroove and directly affects their sealing properties. In

case of the rubber O-ring, these problems cause

addition, sticking may cause equipment toproducts to stick to each other and to stick to theirmalfunction, including operational delays, abnormal

opposing faces.

noise, and abnormal oscillation. Thus, sticking may

This report describes the causes of O-ring sticking anddirectly result in equipment malfunctions.

countermeasures, and introduces the products that
Valqua has developed to reduce sticking troubles.

２-2）Mechanism of Sticking
Sticking is considered to occur by the following
process: when rubber contacts its opposing face,molecules of a rubber segment spread and stick to the43Technical Papers

opposing face, forming an interface through secondary

are categorized in Figure 1.

bonds（including hydrogen bonds and Van der Waals
Anti-sticking
methods

force）. Thereafter, the initial sticking （physicalsticking）occurs. There are no clear categories ofsticking, and there are various theories about sticking.
However, it is sometimes called adhesion when the
degree of sticking is small. Also, the initial sticking
may be affected by the anchor effect, vacuum effect,and so forth. It is considered that primary bonds

Compounds

Surface
improvement- Oil bleeding- Additives- Coating- Surface finish

Figure1

Polymer
design- Molecular weight andcomposition- Polymer alloy

Categorization of sticking-prevention methods（including chemical bonds）subsequently start to form３-1）S ticking-prevention Using Material Combination

at the interface and the sticking strength graduallyThis method reduces sticking by mixing a

increases, leading to strong sticking （chemical

combination of the following selected internal

1,2）

sticking + physical sticking）.

additives to rubber: solid lubricant including PTFE,
lubricating components, releasing components, or２-3）Factors Affecting Sticking

other chemicals. Generally, these formulated chemicals

The sticking strength varies depending on the type ofaffect the physical properties of rubber, compression

rubber and the material of the opposing face.

set, and others, so the characteristics of each additive

However, other major factors affecting sticking

should be balanced.

and humidity conditions, and the surface roughness of３-2）Sticking-prevention Using Surface Modification

the rubber and its opposing face. Other factors

This method reduces sticking by making the surface

３）of the rubber resistant to sticking. There are two

Based on these reports, major factors are categorized

approaches for doing this: coating to form a sticking-affecting sticking strength have been reported.
as follows:４）• Sticking strength decreases with increase of
hardness of rubber.
• Sticking tends to occur with increasing temperature,
although this is not always true.

Spring 2017

strength include the hardness of rubber, temperature

resistant thin film on the surface of rubber, andsurface treatment using chemical immersion orplasma/radio irradiation. The types of coating include
the following: a coating that physically adheres to thesurface and a coating that forms a thin film through• The effects of humidity vary depending on thereaction with the surface of the rubber to enhancecombination of rubber and its counterpart material.

adhesion to the base rubber. The thin film should• Sticking strength decreases with increasingexhibit chemical affinity with the base rubber. A

roughness of the surface of both rubber and metal.

typical surface treatment is surface hardening: rubber

Contact area affects this phenomenon.

is immersed in chemical solution containing avulcanizing agent and then heat is applied for

3. Sticking-prevention Methods

hardening. However, the area modified by thisSimple methods of preventing sticking include

surface, and frictional wear of the modified layer

greasing and lubrication. However, these processes

results in the loss of this preventive effect. Thiscan contaminate products and mounting sections. To

approach should be used with care when applied toshorten the operation time as well to as prevent

dynamic seal products.

approach is limited to the area close to the top

contamination, O-rings which inherently prevent
sticking are required.

３-3）Sticking-prevention Using Polymer Design

Major methods of preventing the sticking of O-rings

This method reduces sticking by improving the
44

No.32

Sticking Troubles of O-Rings and Countermeasuresmaterial polymer of the O-ring itself. Generally,• Prevention of twisting and damage in O-rings

polymers with high molecular weight are considered
chains and end groups（including -COOH, -OH, and>CO）.
Also, this method can be performed by giving a
polymer a structure which inhibits molecular-chain- Untreated- New Rubberflon

Bonding strength (gf)to stick less, as well as polymers with fewer side

motion（e.g. a structure with a high glass transition
which has a structure to reduce sticking while
retaining the elasticity of rubber. Further moleculardesign investigations are expected by new polymer
design and polymer alloys with new structures.
Valqua has developed various methods to prevent andreduce sticking in its products. Some of our key
products are outlined below.

4. New Rubberflon
Spring 2017

New Rubberflon （Rubberflon is our registeredtrademark）is an example of our products that aredesigned to prevent sticking.
New Rubberflon is produced using the surfacemodification method, not just a coating. Because of

No.32

reactive treatment, the treated surface layer adhere
with matrix rubber, thus not easy to remove.
Moreover, the method does not affect the physicalproperties of the base rubber, so most rubber

Test method: tack testing device
The strength required to detach the probe from the test pieces, after
being in contact under certain conditions, is measured.
Test piece: acrylic rubber sheet of 2 mm thickness; weight: 100 gf;
probe: stainless probe, Φ 5 mm; velocity of probe removal: 600
mm/minFigure2 Sticking strength of a rubber treated with New Rubberflon

Coefficient of kinetic friction

point）. However, it is difficult to develop a polymer- Untreated-New
Rubberflon

Test method: ball indenter test, testing velocity: 60 mm/min
Test piece: rubber sheet of 2 mm thickness, weight: 200 gf, ballindenter: SUS Φ 6
SBR: styrene-butadiene rubber; NBR: nitrile rubber;
FKM: fluorocarbon rubber; IIR: isobutylene-isoprene rubber;
EPDM: ethylene propylene rubber; CR: polychloroprene rubber;
ACM: acrylic rubber; U: polyurethane rubber

Figure3

Coefficient of dynamic friction of a rubber treatedwith New Rubberflon

materials such as nitrile rubber and fluororubber
except for silicone rubber can be processed with thismethod. New Rubberflon offers both low sticking andfriction. Thus, the product not only prevents sticking

5. D2370, a Non-adhesive  Fluororubber

between products or to the opposing face, but also

Fluororubber has excellent heat and chemical resistance,

reduces insertion friction when mounting O-ringsand so is used in a broad range of industries. Generally,

Figure2 showed

fluorine is considered to be an adhesion-resistant,values obtained by experiment to measure New

slippery material. However, contrary to expectations,

Rubberflon’s sticking strength. Figure3 showed values

fluororubber often sticks to the opposing face, and so isobtained by experiment to measure friction coefficient.

not an adhesion-resistant material.

The treatment of O-rings with New Rubberflon isD2370 was developed using our unique compounding

expected to provide the following benefits:

technique. The product reduces sticking while• Prevention of sticking between O-rings

maintaining the characteristics of conventional• Prevention of sticking to the opposing face

fluororubbers including heat resistance and physical• Improvement in fit of O-rings（greaseless）

properties.

including cylindrical-surface seals.

45

５,６）

Technical Papers

Table1 showed the physical properties of D2370, andimportant factor which affects maintenance seriously.

Figure4 showed its sticking strength measured by

However, there also are cases where sealing

experiment.

properties are sometimes retained and extended

Table1 L ist of physical properties of D2370（a non-adhesive fluororubber）
D2370
Non-adhesive
fluorocarbon rubber

D0270
Standard Valqua
fluorocarbon rubber

Hardness (Shore A)

70

71

Tensile strength (MPa)

14.0

13.9

Stretch (%)

190

230

Compressed
permanent deformation＊）rate（％）

14

16

200°C/70 hours, 25% compression, Φ 29 mm disc
The values in the table are observed values, not standard values.

＊）

because of the sticking characteristics of O-rings insite of beyond limitation for sealing by permanent
deformation of O-ring. In such cases, prevention
sticking might not an only way to solve problems but
also prevention methods while considering various
operating conditions were required.
Also, various factors including the usage environmentand conditions affect sticking, so it is difficult to solve
sticking problems only with seal materials. Therefore,
it is important to precisely identify the conditions in

Bonding strength (N)which O-rings are used.
We welcome feedback and honest opinions from users,
to help us make full use of the characteristics ofrubber materials, develop high-value-added products,
and introduce new products.

Test method: The test piece was placed in contact with thecounterpart under certain conditions and cooled in an ambientenvironment for 4 hours, then the strength required to detach thecounterpart from the test pieces is measured.
Test piece: rubber sheet of 2 mm thickness; contact pressure: 5.88
MPa; heating conditions: at 120℃ for 20 hours
Counterpart: ring-shaped SUS 304 of Φ 25 x Φ 19; detachingvelocity: 50 mm/min

Figure4 Sticking strength of D2370 measured by experiment

D2370 can be used as an alternative to common
fluororubber in various valves which use a common
fluororubber O-ring including for door seals and gate

１）Mori, K. et al., Journal of the Society of Rubber Scienceand Technology, Vol. 60, 7th issue, 1987
２）Handbook for the Rubber Industry, 4th ed., Societyof Rubber Science and Technology, Japan, 1994
３）Mori, K. et al., Journal of the Society of Rubber
Science and Technology, Vol. 60, 4th issue, 1987
4）Sagan I., Valqua Review, Vol. 38, 8th issue, 1994
5）Sagan I., Okazaki, M., Valqua Review, Vol. 41, 1stissue, 1997
6）Sagan I., Tribology, March 1998

valve seals. We consider that D2370 can reduce
operational malfunctions at opening and closing points
by decreasing sticking strength of seal materials. In
addition, the product is expected to prevent sticking
to the opposing face including flanges.

6. Conclusion
This report explained sticking factors and methods forpreventing the sticking of O-rings, and introduced our
sticking-prevention products.
In the case of static seal products, sticking is one of

Spring 2017

7. References

Masanori Okazaki
Corporate Research andDevelopment Group
Development Division
46

No.32

Evaluation of the Bolted Flange Connection
with PTFE-blended Gasket under Hightemperature and Long-term condition
characteristics（JIS B 2490）,and creep characteristics

1. Introduction

for these gaskets have not been available. In addition,

The bolted flange connections with gasket have been

there has been insufficient verification as to whether

used under high temperature and long-term conditions

thisin oil plant, chemical plant, power plant and so on. In

superior sealing performance compared with theJapan, various asbestos gaskets used to be widely

conventional connection with asbestos gasket.

used because of excellent heat resistance, sealing

Previous studies have investigated the connection

performance, strength, ease of use, and low cost tillwith PTFE-blended gasket for its sealing performance

2008. The many studies for asbestos gaskets

haveat room temperature, flange hub stress, change in axial

been conducted, clarifying the characteristics of thebolt force（load factor）, and the contact gasket stressconnection with asbestos gasket such as sealing

distribution. The results showed that the sealing

performance. In Japan, the use of asbestos products

performance of the PTFE-blended gasket is quite

was restricted in 2008, requiring non-asbestos products

superior to that of connections with the compressed

to be used.

asbestos fiber sheet gasket.８）However, its performance

１-５）

Spring 2017
No.32

６）

As a result, non-asbestos gaskets haveconnection

with

PTFE-blended

gaskethasbeen developed and improved.

at high temperatures is not well known.８） Therefore,

The asbestos gaskets are categorized into two major

research on the mechanical properties of the connection

types: the spiral wound gasket containing asbestos

including creep characteristics and sealing performance

filler and the compressed asbestos fiber sheet gasket.

under high temperatures and long-term condition are

For the substitution of asbestos, asbestos for spiralrequired.

wound gaskets was replaced with flexible graphite,

The objective of the present paper is to examine theand it caused no major problems. On the other hand,mechanical characteristics of bolted pipe flange

the compressed aramid fiber sheet gasket, the flexible

connections

graphite sheet gasket and the PTFE-blended gasket

elevated temperature using FEM calculations andwith

PTFE-blended

gasketsunderhave been developed . The compressed sheet gaskets

experiments. Firstly, the fundamental characteristics

containing aramid fibers shows low resistant to heatof the PTFE-blended gasket such as stress–strain

because they contained a lot of rubber, and the flexible

curves, thermal expansion coefficient, and fundamental

graphite sheet gaskets are so fragile and easy toleakage characteristics are measured. In addition, thescratch. Therefore, in Japan, the PTFE-blended gasket

creep

was improved further and is now widely used. The

measured. In FEM calculations, the change in axial

former PTFE-blended gaskets showed poor creep

bolt force, the flange hub stress and the contact gasket

characteristics, whereas the newly developed PTFE-

stress distribution of bolted pipe flange connection

blended gasket offers improved creep characteristics.

with PTFE-blended gasket at some temperature are

However, the mechanical characteristics including the

calculated. And then, the leak rates ware estimatedstress–strain curve of gasket, fundamental leakage

from the contact gasket stress distribution and7）

47characteristics

at

high

temperaturesareTechnical Papers

relationship between the leak rate and contact gasket
stress. For verification of the FEM method, theexperiments to measure the change in axial bolt force,the flange hub stress and the leak rate at eachtemperature are carried out.
In this study, the test gasket is No.GF300 in Nippon
Valqua Industries, ltd.. The No.GF300 includes norubber and no material degradation occurs in hightemperature and long-term conditions.
Figure1

2. Experiment set up
Figure 1 shows the experimental setup for connection.

experimental set up for connection

3.Gasket property measurement

The change in axial bolt force, the flange hub stressand the leak rate are measured using this set up. The

Prior to FEM calculations, the gasket properties such as

nominal size of pipe flange is ASME/ANSI class300

stress-strain curve, fundamental leak rate, thermal

2inch and the flange material is Stainless Steel 304 .

expansion coefficient and creep are measured.

9）

cartridge heaters. The flange temperature is measured３-1）Stress–Strain curveand controlled using the thermocouple and the flange

Figure2 shows the schematic of experimental setup for

hub stress is measured using the strain gage. The

measuring the sealing performance of the gasket（JISaxial bolt force was measured using the strain gages

B 2490）.It can be heated by electric cartridge heaters.

attached to shank of bolt. The tightening is performed

Figure3 shows the stress-strain curve at room

according to JIS B 2251:2008“Bolt tightening procedure

temperature, 50℃, 100℃, 200℃ and 300℃ measured.

for pressure boundary flanged joint assembly”.

The strain increases as test temperature increases andLeak rate was measured using the pressure drop

it can be seen the temperature dependency. It is

method and calculated by equation（1）because that the gasket material was softened in hightemperature.
⑴

where, L is leak rate（Pa･m3/s）,M is molar mass（kg）,
V is volume within equipment（mm3）,t is measurement
time （s）, R is gas constant （J/kg･K）, T1 is initial
temperature（℃）, T2 is measurement temperature（℃）,
P1 is initial internal pressure（MPa）and P2 is measurement
internal pressure（MPa）.The nominal size of gasket isASME/ANSI class 300 2 inch with thickness of 1.5mm.
The internal pressure is 2MPa, the flange temperatures

Figure2 S chematic of experimental setup for measuring
the sealing behavior of the gaskets（JIS B 2490）

are chosen as room temperature, 100℃ and 200℃. The
initial axial bolt force is 16.4kN correspond to meancontact gasket stress 35MPa.

48

Spring 2017

The connection is heated 3℃/min using electric

No.32

Evaluation of the Bolted Flange Connection with PTFE-blended Gasket under High-temperature and Long-term condition

Figure3

Stress–strain curves of gasket３-2）Sealing performance

Figure5 M easured relationship between the fundamental leakrate and the contact gasket stress in unloading step
at RT and 200℃

The relationship between the fundamental leak rate
and the contact gasket stress at room temperature３-3）Thermal expansion coefficientand only re-load step at 200℃. The experimental setup

Figure6 shows thermal expansion coefficient measured

was shown in Figure2 and the test gas is helium gas

by thermal mechanical analysis（TMA）.It can be said

2MPa.

that the thermal expansion coefficient increases with

Figure4 shows fundamental leak rate at room

higher temperature.

temperature obtained from the experiment. When the

Spring 2017contact gasket stress is 20MPa or greater, it can bemeasured because that the value was less than lower
limit of 5 x 10−5 Pa･m3/s.

No.32
Figure6

Thermal expansion coefficient of gasket３-4）Creep
Figure4 R elationship of gaskets between leak rate andcontact gasket stress at room temperature in aplaten test

The creep characteristics of gasket are measured by
the setup shown in Figure7, for evaluation of gasketed
connection in long-term condition. The dimensions of

Figure5 shows the leak rate in unloading process attest gasket are φ22mm and φ58mm, test gasket

200℃, the initial contact gasket stresses are chosen as

stresses are chosen as 12.5MPa, 25.0MPa, 35MPa, and

19.8MPa, 25.5MPa and 35.0MPa. From comparison

the temperature is 200℃. Figure8 shows the measured

between results of Figure4 and Figure5, it can be seen

creep strain behaviors of the gasket. The abscissa isthat the sealing performance at high temperature iselapsed time, and the ordinate is creep strain. Thisbetter than at room temperature. The result indicatesfigure indicates that the creep strain increased overthat sealing performance increases as the temperature

time. So creep strain increases as gasket stressincreases. This is suggested that because the softened

increases and it show the stress dependency. This

gasket material is able to fill the micro gaps of flange

behavior was formulated to equation 2 and inputted to

faces at high temperature.

FEM calculations.

49Technical Papers

bolt at initial tightening. In Step 2, heat and internalpressure are applied to the inside of the connection.
Flanges and bolts/nuts are modeled with elasticityheat transfer elements. The gasket is modeled withelasticity-plasticity-heattransfer-viscosity

elements.

Table 1 shows the characteristics of each material.

Figure7Equipment for testing the creep of gaskets

Figure8

FE model for pipe flange connection with gasket

Measured creep strains of gaskets

（2）
where

No.32

is creep strain rate（/s）;σ is stress（MPa）;t

is measurement time（s）;and a, n, and j are constants
obtained by experiment（a = 1.61×10−5（/MPa）, n =1.25, j = −0.915）.

Initial state of tightened bolt

Figure10

4. FEM calculations

Table1The FEM calculations are conducted using ABAQUS.
Figure9 shows the FE model for bolted flange
connection with gasket. Taking into account thesymmetry of the connection, 1/32 part（1/2 in axial
direction,

1/16

in

circumferential

direction） ofconnection is analyzed. Bolts and nuts are united, andscrews are omitted. Also, nut shape is simplified from

Spring 2017

Figure9Internal pressure and heatapplication

Boundary conditions

The characteristics of each material

Modulus of longitudinalelasticity [GPa]FlangeBolt

Gasket

200

200

Fig.3
0.45

Poisson’s ratio

0.3

0.3

Linear expansion
coefficient [/K]
Heat transfer
coefficient [W/m･K]

1.12
E-05
4.4
E-02

1.09
E-05
1.1
E-02

Specific heat [J/kg･K]

500

500

1000

Density (roomtemperature) [kg/m3]

7800

7800

2.3

Fig.6
2.5
E-05

hexagonal to circular.
Figure10 shows the boundary conditions. The uniform
bolt stress is applied to the cross sectional area in the50

Evaluation of the Bolted Flange Connection with PTFE-blended Gasket under High-temperature and Long-term condition

5. Experiments and Results of  
FEM Analysis５-1）Changes in Axial Bolt Force
Figure11 and 12 show the changes in axial bolt force
obtained by FEM calculations and experiments at
100°
C and 200°
C respectively. The solid lines show the
FEM results, the dotted lines show experimental
results. And the change in flange temperature isshown in same figure. The initial axial bolt force isFigure12

Changes in axial bolt force at 200℃

chosen as 16.4kN. The flange is heated, kept for 24

Spring 2017

hours, cooled to room temperature. The heated and５-2）Hub Stress of Flanges

cooled cycles are 4 times.

Figure13 shows the flange hub stress at initial

From figure 11 and 12, it can be seen that the changetightening and under high temperature. The figure

in axial bolt force are influenced from temperature ofalso shows value calculated according to the Boiler &the connection. In initial heating, the axial bolt force

Pressure Vessel Code, Section VIII, Division 1.14） The

decreases substantially, because the gasket strain

measured results are fairly good agreement with theincreases due to the temperature dependency of

FEM results, the method of FEM calculations arestress-strain curve of gasket material, that is, theverified.

gasket thickness decreases. Axial bolt force increased
and decreased in accordance with increasing anddecreasing temperature due to the difference inthermal expansion coefficient between each component.
In heating at 200℃, the change in the axial bolt force is

No.32

larger than that at 100℃ and also the reduction in theaxial bolt force is larger in cooling. In cooling, the axial
bolt force is reduced to 2kN, by which the averagegasket stress is 4.3MPa. However, no leakage isobserved.

Figure13

Flange hub stress５-3）Contact Gasket Stress Distribution andLeak Rates
Figure14 shows the obtained contour figure of contact
gasket stress distribution for the gasket in initial bolt
tightening, and the cases where the connection isheated to 100 and 200℃, respectively. The aroundoutside of gasket did not contact the flange face. So thecontact gasket stress is zero.
In these figures, it can be said that the change in
Figure11 C hanges in axial bolt force at 100℃

contact gasket stress distribution in the circumferential
direction is negligible. As the result, the contact gasket
stress increases at the outer edge of the gasket because
the flange rotation occurs. The results at the elevated51

Technical Papers

temperature, show that the outside of gasket is

35MPa, the contact gasket stress keep over leakage

deformed by compression due to the heating and astress, it can be considered that the sealing is kept.

contact force by a bolt.
Figure15 shows the leak rate from the gasket interfaces
is estimated using the contact gasket stress distribution
obtain from the FEM and the fundamental leak rate
shown in Figure4 and 5 12）13）. The abscissa is contact
gasket stress, the ordinate is the amount of gas leakage
per unit contact diameter. A fairly good agreement
between the estimated results and the experimental
results is observed. This confirms the validity of themethod for estimating the amount of leakage from the
FEM calculations and the fundamental leak rate.

Figure15 C omparison of leak rates of connections between
the experimental results and estimated results.

５-4）Estimation of the sealing performance inlong-term condition
The bolted connection with gasket is used in hightemperature and long-term condition, so it is important toand long-term condition. Figure16 shows the change incontact gasket stress in ten years estimated from resultsof FEM calculations. The leak stress（when allowableleakage is 1.7×10−4 Pa･m3/s）is also shown in same figure,the leakage occurs when the contact gasket stressdecreases less than that value. The connection size is
ASME/ANSI class 300 2inch, the fluid temperature is

Figure16Change in contact gasket stress of connection inten years estimated by FEM calculations

6. Conclusion

No.32

200℃ as above evaluations. The shutdown is every two

In this present paper, it is shown that bolted pipe

years, so it is considered in FEM calculations. When theflange connection with PTFE gasket（No.GF300）keep

initial contact gasket stress is chosen as 25MPa, thegood sealing performance in high temperature andcontact gasket stress fall down less than leak stress, andlong-term condition by using experiments and FEM

then it is estimated that the leakage occur. On the othercalculations. The results obtained are as follows.

hand, when the initial contact gasket stress is chosen as（1）The fundamental characteristics of PTFE-blended
gasket were measured experimentally such as therelationship between gasket stress and displacement andits temperature dependency, the relationship between
the leak rate and contact gasket stress, thermal expansion
coefficient and creep property.
（2）The change in axial bolt force of bolted connection
with PTFE-blended gasket is effected substantially byheat cycle and the connection with No.GF300 gasket
shows the good sealing performance in 200℃ heat

Figure14 C ontact gasket stress distributions obtained by
FEM calculations

Spring 2017

evaluate the sealing performance in high temperature

cycle condition. In addition, the flange hub stress was
lower than the value calculated using ASME code.
52Evaluation of the Bolted Flange Connection with PTFE-blended Gasket under High-temperature and Long-term condition（3）The leak rate from the connection with PTFE-

5）Kobayashi, T., Nishida, T., Yamanaka, Y.:“Consideration

blended gasket was estimated from the contact gasket

on the Representations of Sealing Behavior of Gaskets:

stress distribution obtained by FEM calculations andEffects of the Internal Pressure and the Gasket

the relationship between leak rate and contact gasket

Width,”ASME PVP Vol. 457（2003）,pp. 133–138

stress obtained by experiments, and compared with

6）Industrial Safety and Health Law No. 318（2008）

the experimental value to verify the robustness of our7）Nippon Valqua Industries, Ltd. Non-Asbestos Gasket,
Catalogue No. ZY03（2011）

prediction method.
（4）It is proposed the method to estimate the long-8）Sato, K., Muramatsu, A., Kobayashi, T., Sawa, T.:

term behavior of bolted flange connection with PTFE-“FEM Stress Analysis and Sealing Performance of

blended gasket（No.GF300）under high temperature.

Bolted Flanged Connections using PTFE Blended

And it is shown that the connection with No.GF300

Gaskets under Internal Pressure,”PVP 2015-45268,

gasket keeps safety for 10 years when the initial

Proceedings of ASME PVP 2015 Conference（2015）

contact gasket stress is 35MPa, and also that re-9）ANSI/ASME B 16.5, “Pipe Flanges and Flanged

tightening resulted in additional safe.

Fittings”（1996）
10）Japanese Industrial Standards: JIS B 2251 “Bolt

7. References

joint assembly”（2008）

Spring 2017

１）Takaki, T., Satou, K., Yamanaka, Y., Fukuoka T.:“Effects11）Japanese Industrial Standards: JIS B 2490“Testof Flange Rotation on the Sealing Performance of Pipe

Method for Sealing Behavior of Gaskets for Pipe

Flange Connections,”ASME PVP Vol. 478（2004）pp.

Flanges”（2008）
12）Omiya, Y., Sawa, T., Takagi, Y.:“Stress Analysis and

121–128
２）Takaki, T., Fukuoka, T., Yamanaka, Y.:“Finite Element

Design of Bolted Flange Connections under Internal

Simulation of Bolt-Up Process of Pipe Flange

Pressure,”PVP 2014-28606, Proceedings of ASME

Connections,”Valqua Technology News, No. 2（2002）
,

No.32

tightening procedure for pressure boundary flanged

PVP 2014 Conference（2014）13）Omiya, Y., Sawa, T.:“Stress Analysis and Sealing

pp. 5–13３）Sawa, T., Ogata, N., Nishida, T.:“Stress Analyses

Performance Evaluation of Bolted Pipe Flange

and a Sealing Performance Evaluation of Pipe

Connections with Smaller and Larger Nominal

Flange Connections with Spiral Wound Gaskets

Diameter under Repeated Temperature Changes,”

under Internal Pressure,”Proceedings of the JapanPVP 2014-28730, Proceedings of ASME PVP 2014Society of Mechanical Engineers （Ver. A）, Issue

Conference（2014）

671 of Vol. 68（2002）,pp. 1120–11284）Kobayashi, T., Nishida, T., Yamanaka, Y.:“Effect ofCreep-Relaxation Characteristics of Gaskets on the
Bolt Loads of Gasketed Joints,”ASME PVP Vol. 457（2003）,pp. 111–118

Kouji Satou
Corporate Research andDevelopment Group
Development Division
5314）ASME Boiler & Pressure Vessel Code Section VIII,Division 1: “Rules for Construction of Pressure
Vessels”App. 2（2004）

Technical History
Year

VALQUA’s Technical History

1927

Founded NIPPON BRAKE LINING SEISAKUSHO for manufacturing of brake linings for automobiles and various
high-speed machines.

1929

Started research of Compressed Asbestos Sheet and various gaskets.

1930

Started manufacturing of clutch facings.

1931

Started manufacturing of asbestos braided gaskets.
Started manufacturing of high-test lining.

1932

Started manufacturing of asbestos spiral gaskets.
Started research and prototype manufacturing of cloth-inserted rubber molds.
Started manufacturing of laminated compressed sheets.

1933

Received a request from the Imperial Japanese Navy Technical Department to research special high-temperatureand high-pressure metal gaskets.
Started manufacturing of laminated Compressed Asbestos Sheet (No. 902, 305, and 1000).

1934

Completed research on special high-temperature and high-pressure gaskets (No. 1250).
Registered special high-temperature and high-pressure gaskets in the Navy Purchasing List.

1935

Installed Japan’s first manufacturing equipment for large Compressed Asbestos Sheet (for 120-inch sheets).
Started manufacturing of prototypes of large Compressed Asbestos Sheet.

1936

Started research work on fabrication of synthetic rubber.

1937

Had synthetic rubber gaskets installed in KAMIKAZE as the first Japanese product in a round-the-world flight.
Started manufacturing of grease (No. 1).
Obtained polysulfide synthetic rubber, HITACOLE,＊1 and started research work on oil resistance gaskets.

1941

Started manufacturing of synthetic rubber gaskets for aircraft and asbestos compression sheets.

1943

Appointed by the Army Fuel Plant for research on gaskets for oil refining equipment.

Spring 2017

1939

Started manufacturing of aircraft gaskets.
Following the National General Mobilization Law (Article 25), ordered to conduct research tests for powergenerating high-temperature and high-pressure gaskets.
Started manufacturing of metal gaskets for fuel and industrial use.
1947

Started manufacturing of piston valves.

1949

Completed a molding processing method for polyvinyl chloride resin and started sales.

No.32

Started research work on a new braiding method for asbestos mole-braided gaskets.
Commissioned by the Ministry of International Trade and Industry for research on high-temperature, high-pressure,and superheated steam gaskets.
1950

Successfully completed research work on new braiding methods and started manufacturing mole-braided (latticing)gaskets.
Completed research work on high-temperature, high-pressure, and superheated steam gaskets commissioned by
the Ministry of International Trade and Industry.

1951

Completed research work on synthetic rubber oil seals for bearing oil prevention.
Started research work on silicon rubber processing.
Imported Teflon powder＊2 from the United States and started research work on the Teflon molding method.
Started research work on O-rings.

1952

Completed research work on the fabrication of Teflon and started sales as VALFLON®.
Started manufacturing of synthetic rubber oil seals.
Completed research work on metal spiral gaskets and started manufacturing and sales as VALQUATIGHTTM.

1953

Completed MECHANICAL SEAL for rotators and started manufacturing and sales.
Received subsidiary aid from the Ministry of International Trade and Industry for research on the performance of
aircraft gaskets made mainly of silicon or Teflon.

1954

Started manufacturing and sale of O-rings.

54

Technical History
Year

VALQUA’s Technical History

1955

Received subsidiary aid from Ministry of International Trade and Industry for fabrication and manufacturing technology
of polytetrafluoroethylene.

1956

Started manufacturing and sale of Teflon-coated adhesive tape.
Imported Teflon extruders and started research work on thin-walled tubes, hoses, and coated cables.
Started manufacturing and sale of fluorocarbon rubber.
Synthetic rubber gaskets used for fighter jets (F-86) for the first time in Japan.

1957

Completion of industrialization tests for fabrication and manufacturing technology of polytetrafluoroethylene
approved by the Ministry of International Trade and Industry.
Released technical report, VALQUA REVIEW.

1958

Started manufacturing and sale of Combined Drip-Ring Gaskets (No. 2800).

1959

Started manufacturing and sale of screw joint seals, TAPE SEALTM.

1960

Started manufacturing and sale of VALFLON® glass cloths (No. 7920).
Started manufacturing and sale of ball valves.

1962

Started manufacturing and sale of ultrahigh molecular weight polyethylene (HOSUTAREN GUR＊3) products.
Product name: VALREN.

1963

Started manufacturing and sale of Teflon grease SPRAY WAX (ＵＮＯＮ S).

1964

Developed Japan’s first Teflon fiber and started manufacturing and sale.
Completed the world’s largest (400 mm) VALFLON® large-diameter pipes.

1965

Founded NIPPON ELASTON, CO. as a joint venture with the German company ELASTOMER AG and started
manufacturing and sale of thermoplastic polyurethane, ELASTORUN.*4Started manufacturing and sales of Cordseal<Soft>TM.

Spring 20171966

and sale of DURA SEAL.
1967

Newly developed fire-resistant coating material, REF-LIGHT, received certification by the Ministry of Construction.
Jointly developed valve seals with the American company DINNER CO.
Started manufacturing and sale of high-temperature metal coating, VALFLON® BELLOWS.

1968

No.32

Entered a technologically cooperation with the American company DURA METALLIC and started manufacturingStarted manufacturing and sale of carbon fiber-braided gaskets (No. 97-CT, Current No. 6232).
Completed standardization of mechanical seals for mixers and started manufacturing and sales.

1969

Started manufacturing and sale of PURE VALFLON® PASTE.
Started manufacturing and sale of flexible duct connectors, FLECTORTM.

1970

Started manufacturing and sale of metal hollow O-rings.

1971

Started manufacturing and sale of VALFLON® powder gaskets, PHLOROTIGHT.
Received approval to display the API (American Petroleum Inst.) certification mark for ball valves meeting API
Standard 6D.
Started manufacturing and sale of VALFLON® Lining Ball Valve.
Started sale of DOH and MS-type gas removal apparatuses.
Started manufacturing and sale of heat transfer spiral gaskets with twigs, HEAT TRANSFER VALQUATIGHTTM
WITH TWIG.
Started manufacturing and sale of fire-safe ball valves.

1972

Started sale of flexible tubes for air conditioners, VALFLC.
Started manufacturing and sale of ELASTORUN Laminated Films.
Started manufacturing and sale of Gasket Cutter in new design.
Started manufacturing and sale of VALFLON® FLAWLESS GASKET.

1973

Developed completely wet spraying VALQUA WET and started accepting orders.
Started sale of gasket tools in new design.
Started manufacturing and sale of VALFLON® THERMAL CONTRACTION TUBE.

1974
55

Started manufacturing and sale of gland gaskets with braided carbon fibers, CHEMSEALTM.

Technical History
Year

VALQUA’s Technical History

1974

Started manufacturing and sale of soundproofing construction material, NOISE DAMPER.

1975

Started manufacturing and sale of Japan’s first completely unlubricated gasket, NORPACKTM.
Received development subsidiary paid from the Ministry of International Trade and Industry, Agency of Industrial
Science and Technology for research on non-contact seal applications.
Developed anti-corrosive Compressed Asbestos Sheet (No. 1500AC, No. 1501AC, and No. 921AC) and started
manufacturing and sales.
Jointly developed steel-fiber-mixed lightweight concrete slabs with Kajima Corporation.
Entrusted by the Research Development Corp. of Japan with the development of manufacturing technology forheat and alkali-resistant glass fibers.

1976

Developed acid-proof Compressed Asbestos Sheet made from chrysotile (No. 1000) and started manufacturing andsales.
As an important technology research and development project, received subsidiary aid from the Ministry ofInternational Trade and Industry, Agency of Industrial Science and Technology for industrialization tests for
manufacturing of heat-resistant and fireproof building materials with Shirasu glass fibers.
Terminated contract with the British company TBA INDUSTRIAL PRODUCTS LTD. for technical cooperation for
dust laying asbestos cloth.

1978

Terminated contract with the American company FLUOROWARE INC. for cross-licensing of fluorocarbon resin PFA injection
molding, transfer and compressing molding techniques.

1979

Started manufacturing and sale of fused fluorocarbon resin PFA wafer carrier containers and jigs forsemiconductor manufacturing.

1982

Started manufacturing and sale of Compressed Non-Asbestos Sheet.

1983

Spring 2017

Started sale of metal-coated spring gaskets, TRYPACKTM.
Started sale of Oil Sheet.
Started sale of gland gaskets for aramid fiber rotation shafts.
1984

Started sale of VALFLON CRYSTAL RUBBERTM.

1985

Promoted development of various non-asbestos products.
Started sale of GREENTIGHT.

1990

Started sale of VALFLON® Semi-rigid Coaxial Cable.

1993

Received the Plunket Award from the American company DU PONT for ALL FLUOROCARBON RESIN BAR

No.32

CODE.
Established Nara Works in Gojo, Nara, and started manufacturing of highly functional rubber products.
1994

Started sale of CLEANTIGHT®.

1995

Received the Plunket Award from the American company DU PONT for PFA tubes for copying machine rolls.
Started sale of large-capacity, site-construction-type VALFLON® Sheet Lining Tank.

1997

Received the Plunket Award from the American company DU PONT for site-construction-type VALFLON® Sheet
Lining Large-CapacityTank.

1998

Started sale of high-purity fluorocarbon rubber seals for liquid crystal/semiconductor devices, ARMOR® series(4 types).

1999

Started sale of rectangular gate valves for semiconductor or FPD manufacturing device manufacturers.

2001

Started publishing quarterly issues of VALQUA Technology News to pass down most of the roles of the VALQUA
REVIEW.

2002

Received the Plunket Award from the American company DU PONT for electrode films of electric double-layer
capacitors.

2004

Started sale of heat-resistant non-asbestos sheet gaskets, BLACKHYPER®.
Founded the Fluorocarbon Resin Search Institute and VALQUA Seal Research Institute in Shanghai, China.

2005

Completely terminated manufacturing of asbestos products.

2006

Completely terminated sale of asbestos products.
56

Technical History
Year

VALQUA’s Technical History

2006

Started sale of high-temperature VALFLON® jacket gaskets, No. N7030 (H) SERIES.

2008

Integrated the Fluorocarbon Resin Search Institute and VALQUA Seal Research Institute into the VALQUA China
Research Institute (newly established in Shanghai).

2010

Founded J/V VALMEI Corporation (headquartered in Tokyo) to reinforce Expanded Fluoroplastics (sa-PTFE™)
business.
Founded China Membrane Institute in VALQUA China Research Institute in Shanghai, China.
Launched enhanced China operations through an operational and capital tie up with Daikin Industries, Ltd.
Started sale of PTFE sheet gaskets with white filler, BRIGHTHYPER®.

2011

Established the China Functional Resign Research Institute in Shanghai VALQUA Fluoroplastics Corp. Ltd. as atechnological development base.

2012

Started sale of CRYSTALLINE SILICA FREE SERIES using amorphous silica instead of crystalline silica as anenvironmental measure.

2013

Founded ADVANCE FLON TECHNOLOGIES (SHANGHAI) CO., LTD. as a joint venture with Guarniflon S.p.A.,
Italian company, in China.
Started sale of PTFE sheet gaskets with filler, UNIVERSALHYPER®.
Started sale of earthquake-proof countermeasure gaskets No. 6596A.

2015

Published“New Gaskets and Gasketing Technology”(by Takahito Nishida, senior fellow at VALQUA).

2016

Started sale of RCF FREE SERIES using materials other than ceramic fibers as an environmental measure.
Opened APPLIED R&D INSTITUTE in South Korea.
Started sales of improved seal paste, classified as non-dangerous goods with a safe, environmental, carcinogenfree combination.

Spring 2017

＊1 HITACOLE is the name of a product manufactured by HITACHI, LTD.
＊2 Teflon is the name of a fluorocarbon resin product manufactured by DU PONT.
＊3 HOSUTAREN GUR is the name of a product manufactured by HOECHST.
＊4 ELASTORUN is a trademark of BASF Polyurethanes GmbH (Gesellschaft mit beschränkter Haftung).

No.32

57

Recent Technology News Back Issues
No.31 Summer 2016
[Customer Solutions Special]●Greeting●Commentary

Customer Solutions and Evaluation Technologies

Senior Excutive Officer

Director of Corporate Research and Development Group Corporate Research and Development Group

Development Division

Mutsuo Aoki

Takaharu Ikeda

General Manager●Technical Papers Gasket Clamping Problems and Their Solutions
Corporate Research and Development Group

Development Division Takahiro Fujihara
Large Diameter Gland Packing Installation Problem Examples and Installation GuidelinesCorporate Research and Development Group Development Division Masato Hamade
Causes of Blister Problems Resulting from High-pressure Gas and Highly Volatile LiquidsCorporate Research and Development Group Development Division Hirofumi Zushi
Causes of O-ring Transfer Problems and Their Solutions
Corporate Research and Development Group Development Division Ryosuke Nishi
	Lining Pipe Problem Examples
Corporate Research and Development Group Development DivisionHigh Performance Plastics Development Division Technical Service Section No.1 Yoshifumi Kutsuzawa
Explaining the PTFE Linear Coefficient of Expansion
Corporate Research and Development Group
Development
Division High Performance Plastics Development Division Technical Service Section No.3 Nobuyuki Ota●Contribution	Characteristics of Hydraulic Cylinders Used in Standard Industrial Machinery and

Their Seal System Problems―Responding to the MRO Market

TAIYO,LTD. Toshinori Ueda

No.30 Winter 2016
[Core Japanese Industry-Supporting Elastomer Products Special Issue]● G r eet i ng



President & CEO

Toshikazu Takisawa● On Issuing the Core Japanese Industry-Supporting Elastomer Products Special Issue● Technical Papers
Senior Excutive Officer

Director of Corporate Research and Development Group

High-pressure Hydraulic Seal Systems
Corporate Research and Development Group

Low-torque Seals for Rotating Joints

Development DivisionCorporate Research and Development Group

Mutsuo Aoki

Zyunichi Yamashita

Development Division

Akihiro Nagano● Product Introduction

Developing Radiation Resistant Elastomer Products―High-functional EPDM H3070 and H0880
Corporate Research and Development Group
Development Division Ken Suzuki
Elastomer Products for Industrial MachineryCorporate Research and Development Group
Development Division Mitsuru Minami
Elastomer Products for the Beverage Industry
Corporate Research and Development Group
Development Division Masanori Okazaki
High-Functional Perfluoroelastomer Products
Corporate Research and Development Group Development Division Naoki Oosumi

No.29 Summer 2015
[Soft Gasket Special Issue]● G r eet i ng

Senior Excutive Officer

Director of Corporate Research and Development Group● General Remarks Changes in the Social Environment Surrounding Gaskets
Seal Sales Group Technical Solution Division

Mutsuo Aoki

Hajime Nonogaki● Technical Papers Surface Pressure Behavior in Gasket Connections and the Effects of Tightening	
Solution Development Group Kazuya Kurihara
Predicting Long-term Behavior in Fluorocarbon Resin Gaskets Using Finite Element Analysis
Corporate Research and Development Group
Development Division Development Group Kouji Satou● Product Introduction

An Introduction to High-Functional Seal Gaskets and Their Different Uses
Corporate Research and Development Group Development Division Development Group Shinya Kurokawa● Contribution On the Sealing Behavior of Pipe Flange Connections with Joint Sheet Gaskets
Professor Emeritus at the University of Hiroshima

Toshiyuki Sawa
58

Earth-friendly, Human-friendly Manufacturing

New Gaskets andGasketing Technology
Recent environmental regulations have led to a majortransformation in the different types of gaskets and theirmaterials. Likewise, we are also seeing major changes
in the design standards for bolted flange connections.
In response to this technical situation, JISB0116“Glossary of Terms for Packings and Gaskets” wascompletely revised for the first time in 37 years.
The recently published “New Gaskets and GasketingTechnology” is the first handbook that both covers thetechnical background leading up to this JIS terminology
standards revision and explains the technical basics ofgaskets and bolted flange connections in an easy tounderstand manner. As such, we feel it will serve as areference for many of those involved in gaskets.
Author: NIPPON VALQUA INDUSTRIES, LTD.
Takahito Nishida, Senior Fellow

ThinkPark Tower 24F
2-1-1 Osaki, Shinagawa-ku, Tokyo 141-6024, Japan
Contact: NIPPON VALQUA INDUSTRIES, LTD.
Email: sr@valqua.co.jp
TEL：(81)3-5434-7370
FAX：(81)3-5436-0560

VALQUA's Sales Network■JAPANNIPPON VALQUA INDUSTRIES, LTD【Main Number】 TEL : (81)3‑5434‑7370 FAX : (81)3‑5436‑0560【Sales Group】
TEL : (81)3‑5434‑7379 FAX : (81)3‑5436‑0571

No.32 Spring 2017

VALQUA SES CO., LTD.
TEL : (81)436‑20‑8511 FAX : (81)436‑20‑8515
VALQUA TECHNO, LTD.
TEL : (81)3‑5434‑7520 FAX : (81)3‑5435‑0264
GARLOCK VALQUA JAPAN, INC.
TEL : (81)3‑5510‑2177 FAX : (81)3‑3591‑5377■CHAINA

VALQUA(SHANGHAI) TRADINGCO., LTD.
TEL : (86)21‑5308‑2468 FAX : (86)21‑5308‑2478
SHANGHAI VALQUA FLUOROCARBON PRODUCTS CO., LTD.
【Head Oﬃce】
TEL : (86)21‑5774‑1130 FAX : (86)21‑5774‑1244【Jingansi Oﬃce】 TEL : (86)21‑3253‑5588 FAX : (86)21‑3253‑5568■KOREA

VALQUA KOREA CO., LTD.
【Head Oﬃce】
TEL : (82)2‑786‑6718 FAX : (82)2‑786‑6719【Ulsan Oﬃce】
TEL : (82)52‑227‑6717 FAX : (82)52‑227‑6719■TAIWANTAIWAN VALQUA ENGINEERING INTERNATIONAL, LTD.
【Head Oﬃce】
TEL : (886)7‑556‑6644 FAX : (886)7‑556‑9907【Hsinchu Oﬃce】 TEL : (886)3‑572‑0467 FAX : (886)3‑573‑7232【Luzhu Oﬃce】 TEL : (886)7‑696‑2400 FAX : (886)7‑696‑7100■SINGAPOREVALQUA INDUSTRIES(THAILAND), LTD.
SINGAPORE BRANCHTEL : (65)6352‑2650
FAX : (65)6352‑2653■THAILANDVALQUA INDUSTRIES(THAILAND), LTD.
【Head Oﬃce】
TEL : (66)2‑324‑0400 FAX : (66)2‑324‑0787【Bangkok Branch】TEL : (66)2069‑9961
FAX : (66)2069‑9964【Rayong Branch】 TEL : (66)3802‑6136
FAX : (66)3802‑6137■USA

VALQUA AMERICA, INC.
TEL : (1)408‑986‑1425

FAX : (1)408‑986‑1426

VALQUA NGC, INC.
TEL : (1)713‑691‑1193

FAX : (1)713‑691‑4407■VIETNAM

VALQUA VIETNAM CO., LTD.
【Head Oﬃce】
TEL : (84)220‑357‑0075 FAX : (84)220‑357‑0079【Hanoi Branch】 TEL : (84)4‑3222‑2213 FAX : (84)4‑3222‑2216*The VALQUA registered trademark stands for VALUE and QUALITY.
*The contents of this journal also appear on our home page. *Unauthorized reprinting/reproduction is prohibited.