Summer 2017
No.33

【Customer Solutions Special】● Greetings・
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Senior Excutive Officer Director of Corporate Research and Development Group

Mutsuo Aoki

● Technical Papers

Unsuitable Usage Conditions of Gaskets and Countermeasures・・・2
Sales Group

Technical Solution Division

Toshihiko Enishi● Technical Papers

Evaluation of Basic Sealing Properties of the Pipe
Flange Connection with Metallic Flat Gasket・
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Corporate Research and Development Group Development Division

Kouji Satou

SHINKO PLANTECH CO., LTD.

Yasuharu Kondou

Professor Emeritus at the University of Hiroshima

Toshiyuki Sawa

Corporate Research and Development Group

Satomi Takahashi● Technical Papers

Troubles While Mounting Gaskets and Countermeasures・・・11
Sales Group Technical Solution Division

Satoshi Akiyama● Technical Papers

An Introduction and How to Use Seal Quick SearcherTM（SQS）‒Elastomer Version‒・
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・15
Corporate Research and Development Group Development Division

Akira Ueda

● Technical Papers

Seal Training Center (STC) ‒Interactive Training for Sealing Operation・
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・19

Ｈ＆Ｓ BUSINESS GROUP

Akira Muramatsu● Contribution

Management of Tightening of Flanged Fasteners at Plants・・・24
Mitsubishi Chemical Corporation Mizushima Plant Mechanical Group 2
Maintenance and Engineering Department

Riichi Morimoto● Recent Technology News Back Issues・・・・29

GreetingsThank you for your continuing interest in our magazine.
Amid the rapidly changing global environment, 2017 marks the final year of the Valqua Group's 7th
medium-term management plan, NV・S7. We also reached a major milestone toward the 8th mediumterm management plan. Under our corporate philosophy The Valqua Way, we offer "H & S"
（H［hardware = products］" and "S［sealing-engineering service］）" in order to maximize customer
value and satisfaction. We are also laying the foundation for our growth to prepare for the coming
100th anniversary year through creative ideas, nimble action, and enhanced global risk management.
Valqua Technology News, our technical journal, celebrates its 60th anniversary year since the first

Summer 2017

issue of Valqua Review in 1957. This issue is the 33rd since Valqua Review was rejuvenated andbecame VALQUA Technology News in 2001.
Like the 31st and 32nd issues, this issue examines how we solve problems for customers. Especially,
this issue features solution services to prevent troubles caused by corrosion and leaking from theperspective of "security and safety".

No.33

Regarding gaskets, we introduce case examples of problems and countermeasures against them, andas for elastomer sealing, this issue introduces our sealant-selection service "Seal Quick SearcherTM Elastomer Ver." We also provide an introduction of Seal Training Center（STC）, which offers on-thejob training for sealing work.
The contents of this issue consist of our technical knowledge and evaluation & analysis results, which
we have accumulated over the decades. We believe they are quite useful information for you to takecountermeasures in order to prevent problems.
Valqua will continue to develop new products, unique technologies, and new services to meet yourneeds, and hope this issue provides useful information for understanding our technology development
efforts. We appreciate our valued customers for their continued support of our products and services,and look forward to continuing to serve you.
Senior Excutive Officer

1

Director of Corporate Research and Development Group

Mutsuo Aoki

Technical Papers

Unsuitable Usage Conditions of
Gaskets and Countermeasures
1. Introduction

suggest that the phenomenon might be caused
through the following mechanism: monomeric fluid
permeates the inside of a gasket; the permeating fluidof a gasket to resist corrosive fluids including acidic andcauses polymerization inside the gasket; thealkaline fluids. It also sometimes refers to countermeasurespolymerization results in volume expansion; and thefor events that could occur with given fluids. To address

expansion causes the gasket to break.

such events, not only seal materials themselves, but also

To address these problems, it is recommended toproper selection and application of seal materials arechange to a spiral wound gasket（No. 7596V）, which

important. This report introduces examples of such

does not break when fluid permeates and polymerizes,

events and countermeasures.

and to use gaskets made of PTFE only which are lesslikely to cause permeation. Also, inadequate tightening

2. Examples of Troubles andCountermeasures

is possible o cause permeation, so proper tightening２-1）Blooming phenomenon of resin-type gaskets２-2）Chemical degradation of a core joint sheet

caused by polymerizable monomers

can be a countermeasure in some cases.

caused by permeation of strong acids into

The phenomenon of blooming occasionally occurs in

the PTFE jacket of the N 7030 series

the fluororesin jacketed gasket: No. N 7030 series andBecause of PTFE jackets, PTFE jacket gaskets are

the filler-added fluororesin gaskets: No. 7020, No. 7026,

superior in chemical resistance to joint sheets.

and No. GF300 series. Chemical reaction between the

However, PTFE could permeate some chemicals whenconstituent materials and fluid is not considered toa PTFE jacket gasket is used for a long period. The

cause this phenomenon. In addition, the results ofPTFE may occasionally allow fluid, especiallyanalyzing affected gaskets, which revealed thehydrochloride, to permeate the gasket's core andinvolvement of a material not contained in theaffect the core. If that happens, the following events

gaskets, and the morphology of affected gaskets,

may occur: fluids accumulate into the inside of thePTFE jacket and the inner core; traces of permeation
including discoloration are observed; and fluid
contents are detected by analyzing the inside of thecore. As countermeasures, it is recommended toincrease the thickness of the PTFE jacket and tochange the gasket material（for example, to use thePTFE blended gasket No. MF300 and the spiralwound gasket containing PTFE filler）.

Figure1

Blooming phenomena of a resin-type gasket
2

Summer 2017

The term "gasket corrosion resistance" means the ability

No.33

Unsuitable Usage Conditions of Gaskets and Countermeasures２-3）Decomposition of expanded graphitesmoothly and efficiently. It means they are easy tocaused by oxidation using the gasket

permeate into gaskets. In general, expanded graphite

above the recommended temperature

itself shows lower coefficient of thermal expansion andAs a seal material, expanded graphite has ideal

thermal stability, and could be highly suitable material

properties including excellent chemical resistance andfor seal. However, expanded graphite shows relatively

low creep relaxation, but when the temperature ispoor resistance in permeation and sometimes it results

450ºC or higher, its oxidation reaction with oxygen in

in leakage through the sheet gaskets.

the air usually causes gasification, which transforms

In general, permeation through materials could be

the content into carbon monoxide, carbon dioxide, etc.,

decreased with increasing density by compression, so

resulting in fade-out. Therefore, recommended ranges

it could be a countermeasure to generate tighteningof temperature are maximum 400ºC for the graphiteload to suitable for sealing. For trustworthy sealing,

sheet gaskets: No. VF-30 and No. VF-35E, which arechanging to spiral wound gaskets containing

comprised of carbon only and are significantly

expanded graphite filler such as the No. 6590 series isaffected by temperature, and maximum 450ºC evenrecommended.

for the spiral wound gasket containing expandedgraphite filler of the No. 6590 series because of theSummer 2017
No.33

２-5）Chemical degradation of a joint sheet

structural advantage. When those gaskets are used at

gasket in applying to solvent（acid/temperatures above the recommended range, leakage

alkaline）process line

occurs due to loss of the constituent material in a

When a gasket is used for a fluid for which it does not

relatively short time. In the case of spiral woundhave enough resistance, the resulting fade-out or

gaskets, placing non-asbestos filler or mica filler along

dissolution of some constituent materials make thethe inner and outer periphery blocks oxygen contact,gasket more fragile and softer, leading to reduce

inhibits oxidation decomposition, and maintains sealing

tightening stress and other phenomena. These eventsfunctions at 450ºC or higher. Although non-asbestos

can readily be determined by analyzing usedfiller loses organic constituents at high temperatures,products. In these problems, it is especially dangerous

usually, inorganic constituents will not change.

that a gasket breaks so markedly that it does not

Therefore, during non-asbestos filler remains withinkeep its original shape.

hoops, it prevent expanded graphite from oxidation

As a countermeasure, it is recommended to change tobecause of oxygen shielding effects.

gaskets, such as No. UF300, which have moreresistant to fluid.
２-6）Erosion of soft gaskets caused by slurry fluid
When a gasket looks severely broken in appearance
but has no tightening problems, and an analysis of aused product shows no chemical deterioration causedby fluid and heat, even if it is very rare case, physicalfracture by erosion from fast-moving powder crashing

Figure2 O
 xidation loss of expanded graphite from a spiralwound gasket

against the gasket could be considered. Although thefluid's properties and the channel's design influence
the erosion, erosion usually occurs in slurry fluids２-4）Leakage of heat transfer oil through gasket

which contain fine particles.

Oils and fats used as heat media are generally

As a countermeasure, it is effective to placedesigned to have a low viscosity so as to flow

constituent materials that have adequate resistance3

Technical Papers

against erosion inner side of gasket such as spiralwound gasket with inner ring or sheet gasket withgrommet.

3. Conclusion
We introduced a part of cases of gasket corrosion
troubles and countermeasures. We hope this reportwill help you to select and determine seal products tosolve leakage problems and achieve the required
sealing.

Figure3

Erosion of a soft gasket

Sales Group

Summer 2017

Toshihiko Enishi
Technical Solution Division

No.33

4

Evaluation of Basic Sealing Propertiesof the Pipe Flange Connection with
Metallic Flat Gasket
1. Introduction

leakage of 1×10−4 Pa･m3/s level due to the limitationsof the measuring functions of evaluation equipment.

flat gaskets and ring joint gaskets are widely used

The objective of this paper is to discuss the leak rate

within the flange connection under high temperatureof 1×10−4 〜 10−7 Pa･m3/s for metallic gaskets. The

and high internal pressure conditions in petroleum

sealing performance of the gaskets under compression

refining, petrochemical, and power plants. However,was measured for two types of gasket materials

the some leakage accidents occur in the connections.

（aluminum and copper）and three types of gasket

The main reasons of those are considered that thewidth using platen by the experiments and the FEM

mechanical characteristics and tightening method of

calculations. In addition, the mechanical characteristics

the gasketed connection have not been clarified. Manyof pipe flange connection with metallic gasket wereprevious studies for soft gasket such as theevaluated using the ASME/ANSI class 300 2-inch

compressed fiber sheet gaskets, PTFE gaskets, andflange.

High Pressure Institute of Japan（HPI）, universities,
and manufacturers. However, there have been few
studies on a flanged connection with the metallic
gasket, so their behaviors remain unknown1）,2）.
Kondo et al. reported the plastic strain on the gasket

Leakage volume [Pa･m3/s]

spiral wound gaskets have been performed in

Aluminum

Chromiummolybdenum steel
Copperface made the sealing performance in metallic flat
gasket improved3）-7）.
The relationship between the leak rate of metallic flat

Mean gasket stress [MPa]（a）The relationship between leak rate and mean contact gasket stressgaskets made by chromium-molybdenum-steel, copperand aluminum and the mean contact gasket stresswere shown in Figure1（a）. It was found the sealing
performances were improved as Young’s modulus andsurface hardness of material decrease. In addition,
when the ratio of mean contact gasket stress for theyield stress was related with leak rate, the leak rate

Leakage volume [Pa･m3/s]

Summer 2017

It is known that the metallic gaskets such as metal

American Society of Mechanical Engineers（ASME）,

No.33

of prior studies have been discussed around thedecreased exponentially at the value of ratio is near
1.0 as shown in Figure1（b）. Those data indicated that

Chromiummolybdenum steel

CopperAluminum

Mean gasket stress/yield stress [MPa]the sealing performance of metallic gasket was（b） The relationship between the leak rate and the rationof the mean contact gasket stress for yield stressinfluenced so much by the yield stress. However, mostFigure1

5

The sealing performance of metallic flat gaskets

Technical Papers

2. Experimental Methodwith the axi-symmetric model, however, the 3-D model
was employed to compare with one for the pipe flange

Figure2 showed the experimental setup of platenconnection. The gasket was modeled as elastoplastic

device in which metallic flat gasket was compressed

element, and the Platens were modeled as elastic

for measuring an amount of leakage. The experimental

element. The platen was under compression, then the

setup was consisted of the compression tester（AUTO

gasket stress, compression displacement and

GRAPH 500KND; made by Shimadzu Corporation）

corresponding plastic strain were calculated. Here, theconsisted of the platen made of SUS304, a helium gas

corresponding plastic strain is defined as:

cylinder, a pressure gauge, a flow meter for amount ofleakage and the displacement gages. The device formeasuring leak rate could be alternately switchedfunctions between a soap-film flowmeter and helium
leak detector（made by ULVAC）. When the leak rate
was 1×10−4 Pa･m3/s or lower, the measurement was
performed using the helium leak detector. The
materials of flat metallic gasket were aluminum

Gasket（A1050）and copper（C1020）. The sizes of gasket
were φ25×φ20（outside×inside diameter）,φ30×φ20,

Platenchosen as 3.0mm. The helium gas was applied to

Figure3

FE model for platen testing

4MPa after the platen with gasket is compressed, andthen, the leak rate and displacements of gasket were
measured. In a test sequence of compression andrecompression, the contact gasket stress was changedin the following stepwise: 0→ 180→ 0 MPa foraluminum, and 0 → 450 → 0 MPa for copper.

4. Results of Experiments and FEM
calculations
Figure4 showed the results of platen test foraluminum and copper gaskets. It was found that the
deformation increased as the outer diameter of gasket

GasketCompression Rubber O-ring Soap-film
flowmeter

decreased（as the gasket width decreased）in bothmaterials. This was resulted in the influence of shapeof gasket.

PlatenFigure5 showed the surface conditions of the
Sleevealuminum flat gasket with a diameter of φ20×φ40 andthe platen after the compression test. It seemed that
there were white discolorations at inner and outer

Illustration of platen test equipment

side positions of gasket on both the gasket face and3. FEM Calculations Method

aluminum gasket would have been deformed to inner

Figure2

the platen faces. Those imply that the compressedand outer diameter and be sharpened by the friction

The FEM calculations were performed for the platenwith the platen faces because of remained small

test shown in section 2, using the numerical code

aluminum particles on the surface.

ABAQUS. Figure3 showed the 3-D FE model of the

The relationship between leakage volume obtained

platen test equipment with metallic flat gasket.

from the platen test and the mean gasket stress was

Originally, an effective evaluation can be calculated

shown in Figure6. Use of a helium leak detector
6

Summer 2017

φ40×φ20, φ65×φ 55mm, and the gasket thickness was

No.33

Evaluation of Basic Sealing Properties of the Pipe Flange Connection with Metallic Flat Gasket

allowed the measurement of very small leakage
results for both aluminum and copper gaskets showedthat application of a higher average gasket stress
reduced the leakage volume and that a reduction of
the mean gasket stress increased the leakage volume.
Also, the reduction rate of leakage volume became
more moderate at around 120 MPa for aluminum and

Gasket stress [MPa]volume of approx. 1×10−7 Pa･m3/s. The measurement

at around 250 MPa for copper.
In general, the relationship between leakage volume

Compression amount [mm]and mean gasket stress is known unchanged even（a）Compression properties of aluminum flat gaskets

when the gasket width is changed. Therefore, theorganized according to the mean gasket stress.
During the unloading process, the leakage volume
rapidly increased at approximately 30 MPa foraluminum gaskets and at approximately 50 MPa forcopper gaskets. This was considered to have beenloading between the flange and gasket surfaces.
Figure7 showed the results of a Finite Element（b）Compression properties of copper flat gaskets

showed the distribution contours of gasket stress andcorresponding plastic strain when the gasket material

No.33

Compression amount [mm]Analysis which replicated the platen test. The figure

Figure4Compression properties of copper flat gaskets

is aluminum and the gasket dimensions are φ20×φ25.
The figure indicated that the corresponding plasticstrain rapidly increased when the mean gasket stressincreased from 100 MPa to 120 MPa. At that time, thegasket might have undergone a marked plastic
deformation to fill the very small roughness on theflange surface to improve sealing properties. This

Figure5

Surfaces of gasket and flanges after compression test

result indicates that plastic strain of a gasket surface
is necessary for metal gaskets to exert their excellent
sealing properties.

Leakage volume [Pa･m3/s]

Summer 2017

caused by the loss of conformability of initial step ofGasket stress [MPa]sealing properties of metal flat gaskets can be

Gasket stress [MPa]（a）Relationship between leak rate and contact gasket
stress for aluminum flat gaskets
7Technical Papers

Leakage volume [Pa･m3/s]

stress was applied to the cross sectional area in thebolt at initial tightening, while the displacements ofthe symmetrical plane were fixed in the axial
direction. In the experiments, each axial bolt force wasmeasured using the strain gauge attached to theshank of each bolt and the outputs are recorded in adata logger. The helium gas 4MPa was applied fromcylinder and the leak rate is measured by pressure
Contact pressure [MPa]（b）Relationship between leak rate and contact gasket
stress for copper flat gaskets
Figure6 Relationship between leak rate and contact gasket stressdrop method.
Figure10 showed the leak rate from aluminum flat
gasket with dimensions of φ65×φ55 for the bolted
flange connection (2inch) with metallic flat gasket
which was described in dotted line and the measured
result in the platen tests was described in line.
Although the value of lower leak rate from pipe flange
connection could not be measured by the pressure（a）Contact gasket stress distributions

drop method, it was found that the leak rate of bolted
flange connection behaved similar with that in thethe bolted flange connection and the plastic
deformation occurred in lower average gasket stress（b）Corresponding plastic strain distributions

region. The leak rate decreased substantially when

Figure7 D istributions of contact gasket stress andcorresponding plastic strain at each step obtained
from FEM calculations

the contact gasket stress was applied 100MPa.

Summer 2017

platen test because it was due to the flange rotation in

Figure11 showed the corresponding plastic strain
distributions at that timing using FEM calculations. It

5. E
 valuations of pipe flanged
connection with the metal gasket

indicated that the corresponding plastic strain was

The previous sections described the evaluation using

100MPa. It was considered that the sealinga platen, which enabled ideal homogeneous compression.

performance increased so much under un-uniform

In this section, the evaluation of characteristics using

stress compression in pipe flange connection because

actual pipe flange connection was discussed.

of increasing of the corresponding plastic strain.

Figure8 showed the test equipment for pipe flange

The method of determining bolt preload for achieving

connection, and figure9 showed the FEA model of theallowable leak rate（less than 1×10−4［Pa･m3/s］）was

pipe flange connection with gasket. The connection

proposed in reference 8）. This equation is described insizes were chosen as ASME/ANSI class 300 2 inch

Eq.（1）.

small when the contact gasket stress was 90MPa,
however rapidly increased at contact gasket stressand bolts were eight M16. Taking into account the（1）symmetry of the connection, a one-thirty two part ofwhere, d2 is the outside diameter and d1 the insideconnection was analyzed. In the FEM model, it wasdiameter of the gasket, N is the bolt number and b isassumed that the nut was connected with a bolt andthe coefficient which indicates the initiation of thethe screw thread of the bolt was not taken into

plastic deformation in the metallic gasket.

account. In addition, for simplicity, the hexagonal nuts

Figure12 showed the leak rate of 2”bolted flange

were replaced with a circle shape. The uniform bolt

connection, the abscissa was bolt preload from
8

No.33

Evaluation of Basic Sealing Properties of the Pipe Flange Connection with Metallic Flat Gasket

average gasket stress in Figure9 The triangle marks
Eq.（1）. The compressive yield strength of aluminumand copper gaskets were 120 and 250MPa, respectively.
In addition, the factor of better sealing used was 0.8 in
the previous paper 6）. The leak rate less than 1×10−4［Pa･m 3/s］ can be obtained by the bolt preloads

PlatenLeakage volume [Pa･m3/s]（○ , △ , □）showed the bolt preload calculated by

Pipe flanged fastener

calculated by Eq.（1）. Thus, Eq.（1）was verified for
determining the bolt preload to satisfy the allowableleak rate in bolted flange connection with flat metallic
gasket.

Gasket stress [MPa]Figure10 C omparison of leak rate from platen test and pipe
flange connection

StressCorresponding plastic strain

Summer 2017

Leakage volume [Pa･m3/s]

Figure11 T he corresponding plastic strain distributions ofaluminum flat gasket in pipe flange connection

No.33

Figure8

Illustration of pipe flanged connection

Bolt axial tension [kN]

Leakage volume [Pa･m3/s]（a）Aluminum flat gasket

Bolt axial tension [kN]（b）Copper flat gasket
Figure9 F
 EA model of pipe flange connection with metal
flat gasket
9

Figure12 easurement results and estimated results ofMleak rate for pipe flanged connection

Technical Papers

Japanese）Vol. 75, 756th issue, pp. 51–56; 2009

6. Conclusion

3）Koji Kondo, Shota Tsubaki, Toshiyuki Sawa, andIn the present paper, the leak rate of 10−7 level for flat

Yuya Omiya. The Sealing Characteristics of Bolted

metallic gaskets which were compressed using theFlanged Connections with Metal Flat Gasket underplaten devise testing machine was measured. In

Internal Pressure, Journal of High Pressure Instituteaddition, the leak rate in the bolted flange connectionof Japan Vol. 52 No. 1, pp. 4–15; 2014

with flat metallic gaskets was also measured. The

4）Koji Kondo, Shota Tsubaki, Toshiyuki Sawa, andcontact gasket stress distributions in both platen test

Yuya Omiya. FEM stress analysis and sealing

and bolted flange connection with flat metallic gasket

performance evaluation of bolted flanged connections

were analyzed using FEA calculations. The resultswith ring joint gasket under internal pressure,obtained are as follows.

Transactions of the JSME（in Japanese）Vol. 80,（1） The leak rate of the metallic gaskets which were816th issue, pp. 1–13; 2014

compressed in the platen devices was measured−75）Kondo, K.，
Sawa, T.，
Sato, K.，
T., Kikuchi，and Tsubaki,3in the 1×10 ［Pa･m /s］） level using both

S.，
“The sealing characteristics of bolted flange

methods of a soap film flow meter and a helium

connection with metal gasket”，ASME Pressure
Vessels and piping Conference, PVP2012-78413（2012）leak detector.

6）Kondo, K.，
Tsubaki, S.，
Sawa, T.，
Sato, K.，
and Omiya,leak rate was independent of the dimensions ofY.，“Sealing performance evaluation in bolted flange

gaskets. In addition, the leak rate decreased withconnections with ring joint gasket subjected to

an increase of the gasket stress linearly to theinternal pressure”, ASME Pressure Vessels andleak rate level of 10−6 which corresponded to thepiping Conference，PVP2013-97173（2013）7）Kondo, K.，
Tsubaki, S.，
Sawa, T.，
Omiya, Y.，
and Sato,

gasket yield strength.
（3） In an ASME/ANSI class 300 2-inch pipe flange

K.，“FEM stress analysis and the sealing

connection, sealing properties were also found to

performance evaluation of bolted flange connections

have been markedly improved when part of thewith metal flat gaskets”，ASME Pressure Vessels

gasket's contact surface had yielded.

and piping Conference，PVP2013-97828（2013）（4） It was provided a method for calculating the axial8）Kondo, K.，and Sawa, T.，“A Determination method

tension required for initial bolt fastening of aof bolt preload for bolted pipe flange connections−6

fastener under a basic leakage volume of 1×10

with metal gaskets under internal pressure”，
ASME

Pa･m3/s and compared calculated values withPressure Vessels and piping Conference，PVP2015-

experimental results to verify the method.

45163（2015）

7. References
1）SAWA, T., HIGURASHI, N., AKAGAWA, H,“Stress
Analysis of Pipe Flange Connections”, Transactionsof the ASME, Journal of Pressure Vessel Technology,
Vol.113, No.4, pp.497-503（1991.11）
2）Tadao Fukuta, Koichi Ozaki, Jun Kajiya, and Teiji
Hayakawa. Structural Behavior and Leakage
Characteristics of Pipe Flange Structure under
Bolting up Load and Internal Pressure（In Case of
Flat Metal Gaskets）, Transactions of the JSME（inKouji Satou
Corporate Research andDevelopment Group
Development Division

Yasuharu Kondou SHINKO PLANTECH CO., LTD.
Toshiyuki Sawa Professor Emeritus at the University of Hiroshima
Satomi Takahashi Corporate Research and Development Group10

Summer 2017（2） In the platen device tests, it was found that the

No.33

Troubles While Mounting Gaskets
and Countermeasures
1. Introduction
The term seal means to prevent a fluid from leaking

circumference does not need to be welded completely;
partial side spot welding or simple welding issufficient.

from inside to outside or from outside to inside in piping,Common typedevices, and equipment at various plants and themembers for such purposes. To achieve sealing as

Circumference-sutured type

intended, not only the seals themselves but also theproper selection and application of seals are important.

Circumference-fusion bonded type(partial or simplified fusion)

Among sealing-related information, we previously

Summer 2017

introduced gasket-tightening troubles andcountermeasures1）. This report introduces additional
troubles that may occur while mounting gaskets andcountermeasures.

※）Note: The circumference-sutured type can be used only in gaskets withdiameters of φ400 or narrower. When circumference-sutured types are
not applicable, circumference-fusion bonded types can be used.

Figure1

Jackets of fluorocarbon resin envelope gaskets2-2）Wetting of a felt sheet of a fluorocarbon
resin envelope gasket

2. Examples of Mounting Troubles
and Countermeasures

Some No.N7030-series fluorocarbon resin envelope2-1）Jacket's fold-over in fluorocarbon resin

sheet is vulnerable to compression fracture when it is

No.33

envelope gaskets
The fluorocarbon resin envelope gaskets, No.N7030

gaskets use felt sheets as their cores; however, a felt
wet. Therefore, they should not be mounted andtightened in rainy weather.

series, have the jacket sideways V- or U--shaped crosssection, all of which have openings on the side ofoutside diameter. Due to such jacket’s structure, when2-3）Scratching on the surface of expandedgraphite gaskets

a gasket is mounted, especially when it is mounted

Expanded graphite material has ideal properties as a

into a narrow space inside a flange, the gasket's

seal material including excellent chemical resistance

fluorocarbon resin jacket sometimes folds over and isand minimal creep relaxation; on the other hand, it has

tightened while the jacket is left bent toward thehandling disadvantages including vulnerability andinside. This bent part causes a level difference whichfragility. If expanded graphite gaskets are roughly

becomes a channel for leakage, resulting in poor

handled during transportation or mounting, it could besealing. Therefore, care should be taken not to cause aeasily to develop leakage channels on the surface andfluorocarbon resin jacket to fold over when mounting.

the risk of poor sealing.

Fold-over can be prevented by using the following

Therefore, the following products should be stored

countermeasure products whose outer sides are

and transported in the packaged condition to prevent

adhered and closed. In such products, the wholesurface scratching: the expanded graphite sheet

11Technical Papers

gasket; No.VF-35E, the expanded graphite spiralwound gasket; No.6590 series, the serrated metal2-5）Misaligned mounting of large-diameterspiral wound gaskets

gasket with expanded graphite sheet: No.6540H, theIn a male-female flange and groove flange which havemetallic flat gasket with expanded graphite attached:a large roughness clearance, especially in a vertically

No.6560, and the metal jacketed gasket with expanded

placed spiral wound gasket, the main body of thegraphite attached: No.N6520. Also, care should begasket is dislocated from the flange face, and thetaken when mounting them, such as avoiding

flange face edge sometimes contacts the inside area ofscratching the gaskets with sharp objects including

seal body. In this case, a spiral wound gasket might

nails and tools and not placing them directly on the

protrude beyond the gap, resulting in breakage or

ground.

leaking.
Therefore, for a spiral wound gasket used in a heat2-4）Breakage of large-diameter spiral woundexchanger, the number of the inner metal strip

gaskets in pre-utilization conditions

without filler and the number of spot welding applied

including transportation

to each winding are increased; in addition, the gasket’s outer diameter is manufactured to ensure over-easily, but large-diameter spiral wound gaskets withtolerance . These approaches reduce the risk ofor without inner / outer rings have a risk of breakage

protrusion, breakage, and leakage even when the main（so-called loosening）when excessive force is applied

body is dislocated from the flange face.

during storage, unpacking, transportation, andWhen such problems occur despite these approaches,mounting. Especially, spiral wound gaskets with aadditional metal strip without filler for a 3.2-mm main

diameter of over 2000 mm have higher risks. If the

body can be applied to the outside and inside of thegaskets break, they cannot be used anymore.

regular 4.5-mm main body. This process can prevent

Therefore, take care not to apply excessive force

the main body from becoming dislocated from theincluding twisting and strain to these products.

flange face. Also, for the same purpose, a metallic

・Avoid placing a gasket in the standing position; theround bar can be placed inside.

No.33

horizontal position is desirable.
・Do not forcibly dismount fixtures when unpacking（a written unpacking procedure is enclosed with alarge-diameter spiral wound gasket; read and follow
the dismounting steps）.
・The number of staff required for transportation andmounting varies depending on the product's size.
The following table shows the ideal number of staff
for the operation.

Ideal
configuration

Figure2

An example in which themain body is dislocatedfrom the flange buckling

An example in which a
3.2-mm hoop is added tokeep the main body within
the flange buckling ositional relation of spiral wound gaskets toPflange face

Other than the above-mentioned approaches, theTable1

Approximate number of staff required to handle
gaskets of a given size

Summer 2017

Small-diameter spiral wound gaskets do not breakfollowing mounting method can be used: for tentative
holding, a retainer plate and bolts specialized for the

Gasket's inner diameter

Number of handling staff

1000 ～ 1500 mm

2 or 3

retainer plate are used to hold the gasket in an

1500 ～ 2000 mm

3 or 42000 ～ 3000 mm

4 to 6

appropriate position; guide bolts are used to3000 ～ 4000 mm

6 to 8appropriately adjust the flange; the gasket is tentatively
held with bolts which are used in actual equipment;
then, the retainer plate is removed and final tightening
is applied to the gasket.
12Troubles While Mounting Gaskets and Countermeasures2-6）Mounting a metal jacketed gasket in thewrong direction

then the gasket can be used.
When contact is not confirmed on the whole

When a metal jacketed gasket is used in a male-circumference, grinding is needed. Also, grinding isfemale flange or groove flange and the metal jacket isused to remove scratches and corrosion of a flange's

mounted in such a direction that the folded part of thegroove. In the grinding process, polishing powders aremetal jacket contacts with the convex part of theapplied to the gasket and then the gasket is rotated inflange, the flange's convex edge sometimes breaks thethe flange's groove. Red lead primer or otherfolded part of the metal jacket during tightening.

pigments are used to confirm whether whole-

Therefore, a metal jacketed gasket needs to be

circumference contact is achieved. In the case of anmounted in such a manner that the folded part becomes

octagonal type, grinding can be performed by using

the groove bottom. In addition, since the gasket has anan octagonal gasket itself which is to be mounted.

inside and an outside, in the case of non-symmetrical

However, in the case of an oval type, grinding using

branching gaskets, mounting instructions clarifying

an oval gasket itself reduces the excellent sealing

the direction of the metal folded part must be

properties attained through line contact, so, an

included on the drawing.

octagonal gasket or tool specialized for grinding isused for the process.
In addition, in the case of gas seal and in case of using
hard materials such as stainless steel, the gasket paste

Summer 2017

should be thinly applied.
When sealing functions are inadequate despite
Figure3

Mounting direction of a metal jacketed gasket

countermeasures can be taken: replacing the gasket
with a ring joint gasket loaded with a cover made of a2-7）Incomplete contact of a metal ring joint

No.33

applying gasket paste, the following othergasket to a flange
When both a flange and a gasket are new, no contact

soft material including expanded graphite or copper,
or arranging a gasket in a special dimension fitted fora flange.

problems would occur; however, when a ring joint
gasket is used in a flange that has been used for a2-8）Common checks for all gaskets

long time, incomplete contact between the flange andCommon checks for all gaskets while mounting are as

gasket sometimes results in inadequate sealing.

follows:

Therefore, firstly it is necessary to confirm whether

・Whether a flange has rust, scratches, or dents

the whole circumference of the gasket contacts withwhich adversely affect the flange's sealing

the flange（hereafter, contact）. To confirm this,pigments including red lead primer are applied to thegasket, the gasket is tightened to approximately 20%of the target torque, and then it is opened to checkproperties
・Whether part of a gasket which was previously
used adheres to the flange
・Whether the gasket's surface has scratches or

how the pigments remain on the surfaces.

adhesion of foreign substances

Confirmation can be conducted either on the outside（Especially, if a bolt hole has foreign substances

or inside contact（when the pressure is high, theinside while an upper bolt is being inserted in aoutside is desirable）, to check whether contact ishorizontal pipe, the substance can fall off andpresent on the whole circumference（line contact isadhere to a gasket.）acceptable）. After whole-circumference contact is・Whether the gasket's dimensions are correct

confirmed, the gasket is appropriately tightened, and（Even when a gasket has the same outside

13

Technical Papers

diameter as the specifications, sometimes, the innerfor various types of gasket. Since customers conduct

diameter is different from the specifications. In suchsealing themselves, we hope this report will help themcases, smaller inner diameters can cause leakage

to avoid leakage troubles and achieve sealing as

into a channel.）intended.

・Whether the gasket type is correct

4. Reference

3. Conclusion

1）Takahiro Fujihara, VALQUA Technology News No.

This report introduced troubles occurring while

31, pp. 8–11; 2016

mounting gaskets and countermeasures against them,

Satoshi Akiyama
Sales Group

Technical Solution Division

Summer 2017
No.33

14

An Introduction and How to Use
Seal Quick SearcherTM（SQS）–Elastomer Version–
part numbers of optimal products; that the customer

1. Introduction

has already determined a material based on

We started our gasket version of Seal QuickTM

performance, but does not know available options

Searcher （SQS）in April 2014 under the following

regarding the shape, or that the customer has alreadyconcept: the user can freely select search keywords todetermined a usage condition, but does not know theobtain product information and specifications more

optimal shape and material.

easily and quickly through SQS, which can process a

Summer 2017
No.33

much wider vocabulary.

2-2）Selection of optimal material

This SQS can not only retrieve product information

Ten to 15 types of elastomer material can be used assuch as Web catalogs but also includes Valqua's

sealants. However, even just one material has

unique system of employing temperature- anddifferent physical, oil-resistance, and chemical-

pressure-selection figures and graphs in the output

resistance characteristics depending on how it is used.

displays for assisting product selection （patent

One example of a marked difference in characteristics

pending for "A system to select recommended sealingis as follows. Even for O-rings having the same shape,materials"）.

the material should be chosen depending on theThis report introduces the elastomer version of SQS,

purpose. For O-rings used under static conditions inwhich we started in October 2014.

which long-term reliability is a priority, materials
offering good anti-compression set（settling resistance）

2. Characteristics of Seal Quick Searcher

are optimal; for O-rings used under dynamic conditions,

Seal Quick SearcherTM is designed to support diverse

damage caused by sliding, such as abrasion resistance,

customers ranging from those who usually use ourshould be prioritized when selecting a material.

products to those who do not know what products to

The elastomer version of SQS employs our expertiseuse under given conditions or whether their intended

in material selection. In SQS, customers can select a

product is suitable for their objectives. This report

product application and usage conditions, and thenintroduces these features for assisting product

SQS automatically suggests the optimal material.

TM

not only anti-compression set but also resistance toselection.
2-1）Various approaches

2-3）Links to technical information

The elastomer version of SQS enables a search to be

As Figure1 shows, SQS displays associated information

made based on shape, application, and rubber

as a search result on product characteristics andmaterial. This search mechanism was designed forservice conditions （the range of applicableproduct search assuming: that the customer has

conditions）. SQS also shows links to technical andalready determined the shape, but does not know thedimensional data of VALQUA Handbook to facilitate

15

Technical Papers

understanding of more detailed product informationand dimensional lineups.

② Regarding the approach based on productapplication and industrial field, customers enter afield and then usage conditions. SQS then displays
the primary output as shown in Figure4.
③ Regarding the approach based on rubber material,customers select the material/material No. asshown in Figure5, then SQS displays the primary
output as shown in Figure6.

Figure2

Search approach

Summer 2017

Figure1

An example of SQS search result

No.33

3. An Example of Searching Using SQSAlthough most customers have already used SQS, thissection introduces practical examples of using theelastomer version of SQS for searching, which wasintroduced in the above section, focusing on its main
characteristics.
Figure3 ①

Input for searching based on shape

Figure4 ②

Input for searching based on field

3-1）Searching approach
As Figure2 shows, the elastomer version of SQS
enables searching based on the following variables:① shape, ② product application and industrial field,③ rubber material.
① Regarding the approach based on shape, customers
choose one of the shapes shown in Figure3, andenter usage conditions. SQS then displays theprimary output as shown in Figure6.

16

An Introduction and How to Use Seal Quick SearcherTM（SQS）–Elastomer Version–

Figure5 ③

Summer 2017
No.33

Input for searching based on material

Figure6

Primary output

Figure7

Secondary output3-2）Search Results
Part numbers and products shown as the primary
output are a list of applicable products whichcorrespond to the input variables. When a given partnumber or product is selected, detailed productinformation is shown as the secondary output as

Figure8Tertiary output: product contents and main
applications

Figure9Tertiary output: operating pressure, pressure
direction, and pressure typeshown in Figure7. After selecting a given variablefrom the secondary output （tabs on the bottom
section of the display）, more detailed information
including the information shown in Figures8 and 9（product information and operating-pressure
information）is provided（the information shown is an
example）.

17

Technical Papers

4. Conclusion

without making mistakes in product selection. Please
use SQS, which will help you to find the ideal sealant

The elastomer version of Seal Quick SearcherTM is afor your needs.

search system programmed to use information which

Looking ahead, we will make SQS even more user-

customers select from a Web product catalog, tofriendly, easier to understand the output, and moresuggest seal options which meet the customer's usage

technologically informative, thus supporting

conditions and equipment, more quickly and robustly,

customers further.

Akira Ueda
Corporate Research and Development Group
Development Division

Summer 2017
No.33

18

Seal Training Center (STC) –Interactive Training for Sealing
Operation
1. Introduction

To meet those needs and to provide training
opportunities regarding various on-site sealing

In recent years, technology succession issues in plant

operations, Valqua started to produce skill-training

maintenance skills have gained attention in Japan due

curriculums. The first Seal Training Center（STC）

to the retirement of the baby-boomer generation andwas established in our R&D center in Nara, Japan in

the deterioration of plant equipment. Therefore,

2014 to train specialized trainers. It offers interactive

maintenance management is becoming moretraining of sealing operation curriculum with

important. However, as extension of continuous

organizing hardware-side educational accommodation.

running periods, there are fewer opportunities for

Summer 2017
No.33

younger operators to experience on-site periodical
repair, and making it difficult to maintain and improve

2. Market Development

plant-maintenance skills. Especially, it is said thatAs Figure1 shows, starting from STC in our Nara

plant managers who are educated with only basic

R&D center, we opened other STCs including inknowledge of flange operation including specifications

Machida, Tokyo, Japan and also in China, Taiwan,

and procedures without enough on-site experience

Vietnam, Thailand, and South Korea to provide

have increased. In spite of that, they need to face on-training on sealing operations for Japanese andsite troubles and field operators tend to follow theiroversea customers. This training program has become

experience and intuition for troubleshooting. In

widely known and been rated high.

general, finding root causes of troubles by knowledge

Especially, in Vietnam, Petrovietnam Manpower

only from education is not easy. It is considered that

Training College（PVMTC）, a technical-educationsome serious seal-related accidents have occurred byschool under the control of Petrovietnam, the largest

luck of on-sight experience. According to the Fire andnation energy company, adopted our training system

Disaster Management Agency, the number offor their technical training on handling industrial-use

accidents including fires and leakage（except forseal products. PVMTC is Vietnam's only vocational

those caused by earthquakes）occurring at major

training school for processing plants, where overpetrochemical complexes around Japan has been

15,000 field workers from various industries study.

increasing rapidly since 2006.

We dispatched several Vietnamese specialists as aAlso, in developing nations, where many projects fortrainer to PVMTC, and lent main equipment of STC

the new construction and expansion of facilities andand transferred it to PVMTC. We also provide ourequipment are planned, manpower shortages cause

technologies through essential training-associatedleakage troubles due to inappropriate selection of seal

knowledge, textbooks and other materials, thus

product and unstable operation. To address suchoffering practical training on sealing skills toproblems, these countries are urgently demanded tocontribute the heavy chemical industry of Vietnam.

develop and secure operators.

We also expect to promote the Valqua brand through19

Technical Papers

those activites.

and disclosed the results as shown in Table 1. The

Furthermore, in China, we have co-held“Valquacolored cells in the table show the number ofTraining Session”with China Petroleum and Chemical

accidents caused by seals, which account for 20 toIndustry Federation which have been sponsored by

25% of all accidents.

the China Friction & Sealing Material Association forAmong accidents caused by seals, over 80% were due

seals and fluororesin products since 2003. At“Valqua

to inappropriate selection of seal product and unstable

Training Session”in 2016, our new on-site service of

operation, as shown in Figure2.

conducting STC training at users' sites wasintroduced with user’s great interest.

Poor
operation

Seal Training Center

Locations of STC

Korea

China
Vietnam

MACHIDA-SHI, TOKYO

Poor
selection

GOJO-SHI, NARA

OthersTaiwan※ Source: The High Pressure Gas
Safety Institute of Japan

ThailandCauses of leakage

Therefore, as Figure3 shows, we extracted on-site

Locations of STC

problems, analyzed seal-related troubles, introduced
countermeasures against the problems and applied theknowledge into our STC training curriculums. In

3. Concept

short, the STC training covers the processes from the

STC, which has attracted great interest from thebasics of seal product selection to the management ofmarket, was developed through our accumulated

sealing-associated components. Based on "Know-Why";

sealing skills, especially engineering skills obtained by

to know the causes of leakage and why selection andanalyzing and solving troubles.

operation are important, we have developed training

The High Pressure Gas Safety Institute of Japan has

which integrates classroom-lecture theories andanalyzed the causes of high-pressure-gas accidents

operational training to teach our Know-How including
what operations are required and how to solve
problems.

Total

Total

Malpractice

Total

Total

Poor sealing management

Poor inspection

Poor fastening management

9 40 6 46 345

Total

1

Poor manufacturing

6

Poor design2015 54 9 24 87 85 30 13 28 26 21 203 2

Year

Insufficient communication

4. Training Program

Insufficient operational
standard and others

Errors in operation and judgment

Poor
Human
organization factors
Poor organizational management

Poor vessel management

Poor testing management

Poor maintenance andadministration of equipment
Poor corrosion management

Poor design andmanufacturing ofequipment

Poor operational management

Classification

Table 1 C ause-specific analysis of high-pressure-gas
accidents

We analyzed mistakes in seal-product selection andoperation which are the major causes of accidents
stemming from sealing and then devisedcountermeasures. STC offers training focusing on such

2014 53 14 19 86 72 19 11 29 26 17 174 0 15 6 21 33 6 39 320

countermeasures. In selection training of seal product,2013 38 14 23 75 77 28 18 23 33 19 198 0 15 1 16 50 4 54 343

trainees study the basic selection guidelines to learn

2012 35 11 10 56 65 65 8 28 31 11 208 0 13 1 14 69 13 82 360

how to select optimal gaskets based on fluid type,2011 22 17 11 50 67 66 8 38 28 20 227 0

pressure, and temperature specified by the customer.

81

9 45 4 49 335

The High Pressure Gas Safety Institute of Japan, Summary Report of
Accidents Associated with High-Pressure Gas（as of December 2015）

Then, they learn about the dynamic behavior of
20

Summer 2017

Figure1

Figure2

No.33

Seal Training Center (STC) – Interactive Training for Sealing Operation

Seal Training Center（STC）
Cooperation with customers to investigate the root cause of a leakSelection error

Operational mistake

Pressure

Fluid

Tightening

Mounting

Practicing "Know-Why"and turning "KnowWhy" into skills
Exceeds the range of utilizationpressure → Breakage

Temperature

Fluid mismatch and breakage

Life cycle

Misaligned mounting →reduction in seal width

Overtightening →BreakageTransportation

Storage

MaintenanceAccumulation of "seal engineering"
Hands-on training of maintenance functions
through integration of theory and experience

Seal Training Center
Figure3

Summer 2017
No.33

Concept of STC

gaskets under special environments to understand thetrainee's tightening force with the target force andmalfunctions and troubles caused by inappropriatethen shows how a particular trainee can conduct a

selection.

tightening operation. In the process, the special sensor

In addition, trainees learn the effects of management

bolts output the axial bolt force applied during flange

conditions regarding not only gaskets but also sealing-tightening as an electronic signal, then the data logger

associated components including flanges and bolts,

transforms the signal into axial bolt force, which iswhich are used in flanged fasteners, to acquire key

shown on the PC display. The display can compare theaspects of on-site management/supervising operations.

trainee's results with the predetermined target axial

In operational training, trainees use the flange training

bolt force.

device shown in Figure4 to confirm their own bolt-

Trainees then use the torque-sensor training device,tightening skills. In the confirmation process, theshown in Figure5, to confirm their own tightening

device uses special sensor bolts to compare thecharacteristics and power-adjustment skills, andFlangeReset button

Display

Socket opening

Display

Specialized sensor bolt

Data logger

Figure421

Flange-tightening training device

Figure5Torque-sensor training device

Technical Papers

practice repeatedly until there is no deviation in bolttightening. The torque-sensor training device inserts atightening tool in the socket opening and the display
shows the tightening torque under the trainee's

FlangeBolt

posture and power adjustment.
In addition, trainees receive training on recognizing
malfunctions which occur due to over-tightening andunder-tightening. The training proceeds as follows.
First, the trainee fastens flanges loaded on the sealingproperty training device, as shown in Figure6, to
make the contact pressure lower than the contact
gasket stress necessary for sealing. Then, thepressure gauge adjusts the pressure to replicate air

Figure7Compression-fracture training device

At the end of the training, the on-site tightening-understand the necessity of selecting the optimal

simulation training device shown in Figure8 replicates

fastening conditions. Next, the trainee uses thethe following situations to confirm the effectiveness ofcompression-fracture training device shown in

the training and whether the trainees have acquired

Figure7 to experience and understand problems

tightening skills and whether they can operate

which occur due to over-tightening.

properly: a） a work environment with a narrowfooting, assuming that the trainee works at a highplace; and b）a work environment which replicates a

Pressure gauge

narrow work space due to the presence of piping
which is not subject to tightening.

Air

These efforts of ours are highly evaluated by manycustomers including plant owners and companies

Flangeassociated with plant engineering.

Flange Piping
Figure6

Summer 2017

leaking, so the trainee experiences the leakage to

Working
stand

Sealing-property training device

In addition, we established a curriculum in which
trainees can learn other important points. For
example, some devices, which are replicated device
and piping alignments, are used to make trainees
understand the phenomenon of creep, which isdependent on the gasket's temperature, so they canexperience and understand the resulting problems

Figure8On-site tightening-simulation training device

and countermeasures.

22

No.33

Seal Training Center (STC) – Interactive Training for Sealing Operation

5. Conclusion

Overseas, we are planning to expand collaboration
with public institutions, such as we have already done

To date, STC users have given us feedback that theyin Vietnam and China, in other countries.

want to continue with such training programs. They

Furthermore, we are establishing service package

have also requested additional training on trouble-

systems which include IT-based maintenance supports

prone devices including heat exchangers, so we will

and abnormality diagnoses as a "Hardware & Seal-

continue to develop new curriculums. We have also

engineering service" business, which integrates

received inquiries for training all operators engaging

products and services to meet needs obtained at skill

in flange operations at periodical-repair sites, and aretrainings.

now studying ways to improve on-site services.

Akira Muramatsu
Ｈ＆Ｓ BUSINESS GROUP

Summer 2017
No.33

23

Management of Tightening of Flanged
Fasteners at Plants
1. Introduction
Let me express my congratulations on the 90th
anniversary of the establishment of Nippon Valqua
Industries, Ltd. and on the publication of the 90th
anniversary issue. I greatly respect everyone who has
supported the sealing industry.
Skills to prevent the fluid within flanged fasteners
from leaking are very important for stable and safe
plant operation. In addition, high reliability is requiredin response to the lengthening period of continuous
plant operation, environmental problems, and emission
regulations regarding leakage. To ensure reliability, it
is necessary steadily to build skills and techniques, as

1. Designing of fasteners
・Gasket selection
・Designing according to a leakagevolume standard
2. Setting of the initial fastening conditions
・Tightening force set by taking
operational conditions into account・Tightening methods
3. Tightening techniques
・Evaluation and improvement oftightening techniques
4. Maintenance and management during operation
・Understanding of behavior during operation
・Life cycle（decrease of tightening force,
deterioration of materials, and other problems）
Figure1

Concept of fastener management

shown in Figure1. Especially, regarding sheet gaskets,for asbestos joint sheets, non-asbestos joint sheets,

asbestos materials, and so fluororesin sheet gaskets

which contain organic fibers including aramid fibers

became the norm. So, we needed to take into accountand inorganic fibers, were considered the primary

the operational behavior of fluororesin sheet gaskets

candidate. However, non-asbestos joint sheets containto set the tightening force for them. Robust tightening

non-asbestos fibers, which are stronger than asbestos

operation and management for such settings also

fibers and have weaker fiber-to-fiber interwinding

became important.

power than asbestos fibers. In asbestos fiber joint-

This report describes the evaluation of alternatives heet gas ket s , t hin and long as bes t os fibers

gaskets to asbestos, the results of collaborative studies

themselves were the strength members of a gasket,

to clarify the behavior of fluororesin gaskets during

whereas in a non-asbestos joint sheet, rubber as aoperation, and Mitsubishi Chemical Corporation'sbinder served as the strength member. Therefore,

certification system to ensure proper tightening

functional decline due to hardening of the rubber was

management.

a concern for gaskets used at temperatures above theheatproof temperature of rubber. To address this

2. Gasket Selection

concern, we decided to conduct evaluation tests

Regarding sheet gaskets, asbestos fiber joint-sheet

regarding the temperatures of non-asbestos joint

gaskets have mainly been used for their excellent

sheets.

heat resistance, sealing properties, ease of handling,

Figure2 illustrates the test line. We set up test piping

and cost performance.

in a plant steamline with an inner pressure of 1.3 MPa

In 2006, an ordinance amending the Industrial Safety

and a temperature of 190ºC and then conducted aand Health Law Enforcement Ordinance was issued.

6-month loading test. During the course of the study,

The ordinance banned the manufacture and use ofno macroscopic external leakage was found. However,asbestos and other substances, with an exception forin an opening process after the test, cracks developed

some products. Therefore, asbestos gaskets needed towhen a non-asbestos joint-sheet gasket was removed

be replaced with non-asbestos gaskets. As substitutes

from the surface of a flange sheet as shown in
24

Summer 2017

restrictions on asbestos led to greater use of non-

No.33

Management of Tightening of Flanged Fasteners at Plants

sheet gaskets cannot be used for a long time at high

3. Tests to confirm the behavior offluororesin gaskets

temperatures and that additional tightening cannot be

Fluororesin sheet gaskets had been used as gaskets

applied to those gaskets. So, we concluded that non-with excellent chemical resistance before the non-asbestos joint-sheet gaskets cannot be a substitute.

asbestos trend caught on. When fluororesin-specificAlso, in this test, other types of gaskets were

flow causes a reduction of tightening force, we haveassembled simultaneously. Foamed-carbon gaskets

applied additional tightening to solve the problem.

stuck to the surface of a flange sheet and were not

However, the possibility and timing of additional

easy to handle, and so we concluded that foamed-tightening depend on empirical rules. For proper

carbon gaskets could not be a substitute either. On

maintenance and management, we needed tothe other hand, no major macroscopic problems

understand the behavior of gaskets and devise proper

occurred with fluororesin gaskets, making thesecountermeasures. Therefore, we conducted various

gaskets the primary candidate.

tests to understand their behavior.

Figure3. This result showed that non-asbestos joint-

Mounting of test-use gaskets

3-1）Test equipment
Figure4 illustrates the test procedures, and Table 1
shows the test conditions1）. A strain gauge attached tofastening bolts was used to measure bolt axial tension,

Summer 2017

and the contact pressure of the gasket was calculated
from the contact area with the gasket. Tightening was
conducted according to JIS B 2251（2008）to achieve agasket contact pressure of 25 MPa2）（hereafter, bolt
tightening was conducted according to the same
standard）. No. GF300 gaskets were used.

No.33

Steam trap
Figure2 Outline of the test line

Figure4

Illustration of the stress-mitigation equipment

Table1Figure325

Removed gasket

Conditions for the stress-mitigation test

Test-use dimension

JIS 10K 50A RF

Test-use temperature

200ºC（24-hour cycle）

GasketV/NO.GF300

FlangeMaterial: SS400
Roughness of sealing surface:Rz = 14.4 μm（ave.）Bolt（loaded with astrain gauge）

Dimensions: M16 × 4 bolts
Material: SS400

Contribution3-2）Heat cycle-stress mitigation test
Gaskets were heated at 200ºC in an electric furnace,3-3）Confirmation of the effects of additionaltightening
Usually, as a countermeasure against reduced contact

were measured over time. Heating was conductedpressure, additional tightening is applied. Regarding

under the following three conditions: room temperature;

the timing of performing this additional tightening, thecontinuous heating at a consistent temperature offollowing two conditions are taken: application at high200ºC; and application of a heat cycle alternating

temperatures after the start of operation; andbetween 200ºC and room temperature. In this test,

application at room temperature during operational

one heat cycle was 24 hours with 2 hours ofsuspension for periodic maintenance and othertemperature rise and approximately 3 hours of

reasons.

temperature fall.

Figure6 shows the test results. Additional tightening

Figure5 shows the test results. The rate of contact

increased the residual contact pressure, and thepressure reduction with temperature load was more

effects of contact-pressure retention were confirmed.

reduced than that at room temperature. In the heat-

Regarding the timing, additional tightening at higher

cycle case, a great reduction in contact pressure

temperatures resulted in greater residual contact

during the temperature-fall period was confirmed.

pressure than at room temperature. Since the stiffness

Although the contact pressure of the gaskets

of gaskets decreased at high temperatures, tightening

increased during re-heating, it did not reach thewas conducted while flowing, which resulted incontact pressure before temperature reduction. After

weaker flow after additional tightening. Such

periodic maintenance and before the start of

weakening was supposed to reduce stress mitigation.

operation, airtight tests are conducted. When the fall

In the case of additional tightening under decreasedin temperature greatly reduces the contact pressure,stiffness, crushing strength is also expected tocountermeasures to restore the contact pressure

decrease, so the tightening force must be carefully

should be taken to confirm the absence of leakage andconsidered. Although additional tightening at room

then to prepare for the start of operation. Also, in

temperature resulted in weaker effects than that atareas where frequent heat cycles develop, the contact

high temperatures, it is considered an adequate

pressure of gaskets decreases gradually, so the same

countermeasure in pre-operation airtight tests.

countermeasure to restore the contact pressure
should be taken.

Maintained at 200ºC
Additional tightening
at high temperature
Additional tightening
at room temperature

Room
temperature
Maintained
at 200ºC
Heat cycle

Figure5

Results from the heat cycle-stress mitigation test

Figure6

Results of verification testing of additionaltightening

26

Summer 2017and changes of the contact pressure of the gaskets

No.33

Management of Tightening of Flanged Fasteners at Plants

4. In-house certification system

including new employees who had no on-site

Ideally, a flanged fastener's behavior is clarified,experience and skilled operators who had 30 years oftightening is quantitatively managed for all

experience participated in the training. Regarding

procedures, and tightening is performed in a controlled

their post-training impression,“understood very well”

manner. However, due to limitations of managing

and“understood”accounted for over 90%. In addition,

tools, measurement cost, and limited work period, we

the training received good feedback including

select the target. So, most flanged fasteners are“visualization of changes in bolt axial tension madetightened based on the operator's skills and experience.

the training easy to understand”. So, the training

In the past, assembling while misunderstanding aappeared to be very effective. We are now studying

gasket's specifications, inadequate tightening, andhow to utilize the mobile training system anduneven clamping caused malfunctions. To address

incorporate it into our certification system. In

these problems, Mitsubishi Chemical Corporation

Mizushima's case, the number of trainees was 40.

introduced and is utilizing a certification system for

Therefore, we need to study the curriculum contents

chief gasket operators. Table 2 shows the contents ofand training using multiple training devices to enable

the certification training. Chief gasket operators who

hundreds of trainees to participate during periodic

have passed the test instruct, mentor, and supervise

maintenance.

operators and conduct the final confirmation ofassembling operations. In this way, they have

Summer 2017

responsibility for gasket assembling. Gasketassembling cannot be conducted without the presenceof a chief gasket operator. To date, approximately
3000 operators have been certified as chief gasket
operators. This system appears to be effective forpreventing malfunctions. All certification training

No.33

sessions are provided in a classroom, which is
expected to enhance knowledge, but skills are alsoacquired through on-site experience. Nonetheless, only
on-site experience causes the problem that although

Table2

Contents of the training session

１．Responsibilities of a gasket operator
２．Training to prevent mistakes in gasket mounting
・Gasket types and their handling・Pressure rating and flange specifications
・Bolt specifications at each plant・Points to confirm regarding core tightening anduneven clamping
・Tightening methods (circling tightening)・Inspection and record submission
3．Handling of asbestos gaskets
4．Previous trouble cases
5．Verification testing

operators understand differences in tightening
conditions occurring when bolt axial tension is
reduced by elastic interaction and when a different
tightening attitude is applied, the timing andmechanism of the effects of bolt axial tension andtorque cannot be visualized numerically and othermeasures remained as a problem. Therefore, part ofour mobile training system was introduced in the
Mizushima Plant and a practice training session washeld for operators. Figure7 shows a picture of thepractice training session. The training session includes
the following four contents: evaluation of flangetightening skills, torque-sensing training, understanding
the importance of bolt maintenance, and recognition of
crushing-prone gaskets. A total of 43 operators
27

Figure7

Training session

Contribution

5. Conclusion

systems, as well as training sessions utilizing our

Due to the retirement of old skilled operators and themobile training system. Through such training media,

trend of younger operators to leave work, there has

we will strive to maintain the levels of our operators'

been a declining number of operators specialized inskills. We will also introduce new systems in theflange-tightening operation and a decrease in the levelpursuit of more reliable leakage-preventionof techniques and skills. A system for conducting

technologies.

proper tightening management without depending on
skilled workers is necessary. For example, sealing-

6. Reference

operation management systems enable automatic1）H ajime Nonogaki, Masayuki Yamabe, Riichi

tightening tools to conduct tightening according toMorimoto. Stress-Mitigation Characteristics ofprogrammed procedures, enabling even novices to

Gasket Fasteners, Piping Engineering, Vol. 52, No. 7,

systematically apply tightening force at ap. 28; 2010predetermined torque value.

2）JIS B 2251“Flange Joint Assembly Guidelines”,

This report introduced our education and certification（2008）

Riichi Morimoto
Summer 2017

Mitsubishi Chemical Corporation
Mizushima Plant
Mechanical Group 2
Maintenance and Engineering Department

No.33

28

Recent Technology News Back Issues
No.32 Spring 2017
【The 90th Anniversary Special Edition】●Greeting

President & CEO

Toshikazu Takisawa●Greetings upon the Publication of the 90th Anniversary Special Issue
Senior Excutive Officer Director of Corporate Research and Development Group Mutsuo Aoki
●Upon the Publication of the 90th Anniversary Special Issue
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

Senior Fellow

Takahito Nishida●Contribution Congratulations on the 90th Anniversary Special Issue of Valqua’s Establishment
Professor Emeritus at the University of Hiroshima Toshiyuki Sawa

●Contribution Evolving Gasketing and Sealing Technologies
Professor at Mechanical Engineering, National Institute of Technology, Numazu College Takashi Kobayashi●Contribution Congratulations on the 90th Anniversary Year of the Founding

NIPPON VALQUA INDUSTRIES, LTD.

Takao Iwane

former Managing Director (Technical Manager)●Contribution Congratulations on the Publication of the 90th Anniversary Special Issue of Valqua Technology NewsNIPPON VALQUA INDUSTRIES, LTD.

former Managing Director (Technical ･ Business development)

Yoshiaki Mori

Summer 2017

●Contribution Memories of My Tenure as CTONIPPON VALQUA INDUSTRIES, LTD. former CTO Hiroyuki Kuroda

●Technical Papers Types and Application of Filler-added PTFE Materials


Corporate Research and Development Group

Development DivisionHigh Performance Plastics Development Division

Youichiro Wada●Technical Papers Accuracy and Mold Direction of PTFE Products

No.33



Corporate Research and Development Group Development Division High Performance Plastics Development DivisionTechnical

Service

SectionNo.3

Shigeko Kawai

Corporate Research and Development Group Development Division High Performance Plastics Development DivisionTechnical

Service

SectionNo.3 Nobuyuki Ota●Technical Papers Introduction and Utilization of Seal Quick SearcherTM（SQS）– Gasket Version –

Sales Group

Technical Solution Division

Toshihiko Enishi●Technical Papers Causes of and Countermeasures for Allophone Trouble in a Piston Seal System for Cylinders
Corporate Research and Development Group

Development Division kenichi Takahashi●Technical Papers Sticking Troubles of O-Rings and Countermeasures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

Corporate Research and Development Group●VALQUA’s Technical History●Recent Technology News Back Issues

29

Development Division Kouji SatouNo.31 Summer 2016
[Customer Solutions Special]●Greeting●Commentary

Customer Solutions and Evaluation Technologies

Senior Excutive Officer

Mutsuo Aoki

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

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

Takaharu Ikeda

General Manager

Takahiro Fujihara

Development Division

Large Diameter Gland Packing Installation Problem Examples and Installation GuidelinesCorporate Research and Development Group

Masato Hamade

Development Division

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	Lining Pipe Problem Examples

Corporate Research and Development GroupHigh Performance Plastics Development Division

Technical Service Section No.1

Explaining the PTFE Linear Coefficient of Expansion
Division

Development Division

Ryosuke Nishi

Development Division

Yoshifumi Kutsuzawa

Corporate Research and Development Group

Development

Technical Service Section No.3 Nobuyuki Ota

High Performance Plastics Development Division●Contribution	Characteristics of Hydraulic Cylinders Used in Standard Industrial Machinery and
Their Seal System Problems―Responding to the MRO Market
TAIYO,LTD. Toshinori Ueda

[Core Japanese Industry-Supporting Elastomer Products Special Issue]● G r eet i ng



President & CEO

Toshikazu Takisawa

Summer 2017

No.30 Winter 2016

● On Issuing the Core Japanese Industry-Supporting Elastomer Products Special Issue● Technical Papers

Senior Excutive Officer

Mutsuo Aoki

Director of Corporate Research and Development Group

High-pressure Hydraulic Seal Systems



Corporate Research and Development Group

Development Division

Zyunichi Yamashita

Low-torque Seals for Rotating Joints



Corporate Research and Development Group

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

30

No.33

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.33 Summer 2017

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