Technical Papers

Evaluation of Mechanical Properties andSealing Performance of 24” Pipe Flange
Connections with No.GF300 Gasket
track record as asbestos gaskets do until now, and for

1. Introduction

this theoretical property study or research is required.
We have been investigating the mechanical behavior of

petrochemical plants, power, steel plants, etc.

connection flange joints incorporating our PTFE

Asbestos gaskets are widely used because of theircompound gasket No. GF300 under normal and highhigh heat resistance, sealing properties, high strength,

temperature environments and under pipe bending6）-8）.

easy handling properties, and economical with

It is known that gasketed connection flange connections

numerous studies having been conducted1）-3）. There

have various nominal dimensions, and their characteristics

have been numerous reports of human health hazards

change when the nominal diameters are different. In

with asbestos gaskets published and regulations haveparticular, it is said that the sealing property of the

been established in Japan since around the year 2000.

connections deteriorate as the nominal diameter

However, this trend has been advancing in Europe

increases. However, due to cost and time issues, mostand the United States for some time. Since 2008,of the research on connection flange connections with4）

asbestos gaskets cannot be used in Japan .

gaskets has targeted relatively small diameter

There are two types of asbestos gaskets which are

dimensions of 2 to 6 inches, and the characteristics ofasbestos filled spiral wound gaskets and asbestos joint

large diameter flange connections are yet to be clarified.

sheet gaskets. There were no major problems in

Sawa et al. used a 20 inch sized pipe flange connection

replacing asbestos filler with expanded graphite filler ofto characterize a spiral wound gasket connection,spiral wound gaskets. On the other hand, as alternatives

demonstrating that it differs from the characteristics

for asbestos joint sheet gaskets, a non-asbestos jointof a small diameter pipe flange connection and that it

sheet gasket containing aramid fibers, an expanded

is less sealable9）-13）. However, the ASME standard

graphite sheet gaskets, and a PTFE compound sheet

stipulates a 24 inch flange size with a larger nominal

5）

gaskets were developed and evaluated . Since thediameter, in addition, the mechanical properties andaramid joint sheet gasket contains a large amount ofsealing properties of a large-diameter connection

rubber, it hardens and cracks in a high temperature

flange fastening body incorporating a widely usedenvironment, and the bolts cannot be tightened. The

PTFE compounded gasket hanve not yet been

expanded graphite sheet gasket is easily damaged andinvestigated. Therefore, study of a pipe flange connection

has poor handling properties. From this background,using such a gasket is necessary.

PTFE compound gaskets have become widely used in

The purpose of this study is to evaluate the mechanicalJapan. PTFE is excellent in heat resistance, chemical

properties of the 24 inch tube flange fastener withresistance, and sealing properties, and the problem of

No.GF300 by FEM analysis and experimentally. First,

large creep has been greatly improved by improving thethe basic characteristics of No.GF300 gasket arecompounding formulation and manufacturing method.

investigated in accordance with JIS B 249014）. These

However, the PTFE compound gasket do not have abasic data are to be used in the FEM-analysis to12

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Gasketed pipe flange connections are used in many

No.36

Evaluation of Mechanical Properties and Sealing Performance of 24”Pipe Flange Connections with No.GF300 Gasket

calculate the axial bolt force variations and gasket
contact-stress distributions. In addition, the amount ofleakage from the pipe flange connection is estimatedusing the gasket contact stress distribution calculated
from the FEM analysis and the leakage gasket stressrelationship obtained from the experiment. Experiments
will be conducted to show the validity of the FEM
analysis, and the experimental results and the FEM
analysis results will be compared and examined.
In the experiment, the amount of leakage from thepipe flange connection and the fluctuation of the axial
bolt force are measured. The pipe flange connections
used in this study were ASME class 300 24 inch-sized
connections.
Our high-performance sheet gaskets containing PTFE,
such as No.GF300 used in this research, are widelyused because of their excellent heat resistance,
chemical resistance, sealing properties, and handling

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property. In addition, since it does not contain any
rubber, material deterioration does not occur attemperatures below 300 ℃ or over time and it isconsidered that mechanical properties can beevaluated with high accuracy in this study.

Figure1 Experimental equipment of 24-inch pipe flange connection

2. Experimental method

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⑴

Figure1 shows the No.GF300 gasketed pipe flange
connection equipment for measuring axial bolt force
fluctuations and leaks. The pipe flange connection size

Here, L：leakage amount, M：molar mass, V：internal

is ASME class 300 24 inches, and the material isvolume of the apparatus, t：measurement time, R：gas. It is known that the characteristics of theconstant, T1：temperature at the start of measurement,

pipe connector change greatly depending on the

T 2：temperature at the end of measurement, P 1：

presence or absence of a pipe, and this device has ainternal pressure at the start of measurement, andlong pipe like the actual pipe connection. The size of

P2：internal pressure at the end of measurement.

the gasket is ASME class 300 24 inches, the thickness

The initial internal pressure P1 is set to 2 MPa, andis 3.0 mm, and the bolt nominal diameter is M39.

the experiment is performed in ambient temperature

Strain gauges are attached to the longitudinal axis ofenvironment. Tightening applies as initial axial bolt

all 24 bolts, and the axial bolt force can be measured

forces of 34.2kN, 68.5kN, 102.7kN and 136.9kN

and recorded by connecting to a strain gauge. All

corresponding to mean gasket stresses of 10, 20, 30,

strain gauges are pre-calibrated. The amount ofand 40MPa. After tightening, helium is introduced,

leakage from the pipe flange connection is measured

and the leakage is measured.

15）

SUS304by the following equation（1）using the pressure drop
method.
13

Technical Papers

hysteresis are seen in the compression anddecompression curves. These behaviors are also takenStress［MPa］

into consideration in the FEM analysis for calculation.

Figure2Dimensions of 24-inch pipe flange connection

3. Gasket characteristics

Compression amount［mm］

Figure4

Gasket compression characteristics

3-2）Sealing property
In the same manner as the compressive characteristics,

stress relationship of No.GF300 gasket are measured

a platen device shown in Figure 3 is used to measurein advance by experiments, and the measured values

the relation between gasket leakage and gasket

are used for FEM analysis.

stresses in accordance with JIS B 2490. The gasket iscompressed in stages by a material-testing machine3-1）Compression characteristics

and the leak rate is measured when the material isFirst, the compression characteristics of the No.GF300

loaded with helium at 2 MPa. The gas leaked from thegasket at room temperature are measured using thegasket is collected by the rubber O-ring and sleeve,

experimental equipment shown in Figure 3. The size

and measured using a soap membrane flow meter.

of the platen for compression test is JIS 10K 50A with

Figure5 shows the measured leakage-gasket stressraised face. A gasket is inserted between a pair ofrelationship. The vertical axis shows the logarithmic

platens and compressed by a material-testing machine,display of the amount of leakage, and the horizontal

and the amount of compression at that time isaxis shows the gasket stress. It can be seen that themeasured. Figure4 shows the stress-compression

greater the gasket stress, the smaller the leakage.

amount relationship（compression characteristics）

When the gasket stress was 30 MPa or more, theobtained by the material test. Non-linearity andleakage was very small and could not be measured, so

Leak rate［Pa・m3/s］

the data are not shown.

Gasket contact-stress［MPa］

Figure3

Gasket characteristic measuring equipment

Figure5Gasket leakage-stress relationship
14

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The compression characteristics and leakage gasket

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Evaluation of Mechanical Properties and Sealing Performance of 24”Pipe Flange Connections with No.GF300 Gasket

4. FEM analysis

analyses, fluctuations in axial bolt force and gasket
contact stress distribution are calculated.

Figure6 is an FEM analysis model of a 24 inch sizedgasketed pipe flange connection. A general-purpose
code ABAQUS is used for the analysis and the

5. Experimental and FEM Analysis results

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number of elements is 2695 and the number of nodes

5-1）Axial bolt force

is 4408. Considering the symmetry of the pipe flange

Figure8 shows the results of axial bolt force

connection, the 1 / 96 model（1 / 48 in the circumferential

fluctuations reacting to internal pressure fromdirection and 1 / 2 in the axial direction）is used. In

experiments and FEM analysis. The horizontal axis is

this model, for simplification, the hexagonal nut has a

the internal pressure, the vertical axis is the axial bolt

circular shape with an equivalent cross-sectional area,

force, the solid line is the experimental result, and theand the screws are omitted. Figure7 shows thebroken line is the FEM result. The axial bolt force ofboundary conditions in the FEM analysis. All

the experimental results is the average value of 24

elements are constrained in each direction at thebolts. Initial tightening is applied as axial bolt forces

symmetric interface. An initial tightening force is

34.2kN, 68.5kN, 102.7kN, and 136.9 kN, whichapplied to the bolt model by applying an axial load,correspond to gasket contact-stresses of 10 MPa, 20

and it is restrained when an internal pressure load isMPa, 30 MPa, and 40 MPa, respectively. Under all

applied. The internal pressure exerts pressure on theconditions, the axial bolt force decreased as theflange and the inner surface of the pipe.

internal pressure increased. It is considered that thisElastic elements are used for flange and bolt models,is because the flange rotation increases due to theand ABAQUS gasket elements are used for gaskets.

internal pressure and the bolt axis contracts.

This ABAQUS gasket element can take into accountExperimental results and FEM analysis are in fairly

non-linearity and hysteresis characteristics. In FEM

good agreement, indicating the validity of the FEM
analysis.

No.36

Pipe flange

Axial bolt force［kN］

GasketM39 Bolt
Figure6

FEM analysis model of pipe flange connection

Internal pressure［MPa］

Figure8Bolt axial force fluctuation during applicationof internal pressure

Internal pressure P5-2）Gasket contact-stresses and leakage
Figure9 shows the gasket contact stress distribution at thetime of tightening and at the time of applying 2 MPainternal pressure obtained from FEM analysis. The
Bolt axial force

average gasket contact-stress at initial tightening is 10
MPa, 20 MPa, 30 MPa and 40 MPa. In all the contour

Figure7
15

Boundary conditions for FEM analysis

diagrams obtained, it can be seen that the gasket outerTechnical Papers

diameter is disengaged from the flange flat seat and isstress relationship also shown in Figure4 obtained by

not in contact with the flange and that the contact

experiment11）, 12）. Figure10 shows a comparison of thestresses are zero. Looking at the data at the time ofleak measured experimentally and the estimated leak.

initial tightening, the contact stress becomes larger

The vertical axis is the leakage per unit length by

toward the outer diameter side due to the flange

dividing the total leakage by the contact of the gasket atrotation. It can also be seen that the gasket contact-

the outer circumference. It can be seen that the larger

stress on the inner diameter is zero even when thethe gasket contact-stress, the smaller the leakage. Inmean gasket contact-stress is large. This is because theaddition, the estimated leakage and the experimental

inner diameter of the gasket is separated from theresults are in good agreement, demonstrating theflange by the flange rotation and is not in contact withvalidity of the leakage estimation method and FEM

the flange In addition, it was found that the change inanalysis.

was very small. When internal pressure applied, the sumof the gasket contact stresses decreases due to thethrust force in the axial direction.
Here, the leakage from the flange connections isestimated from the gasket contact-stress distribution
obtained from the FEM analysis and the leakage gasket

Leak rate［Pa・m3/s・m］

the circumferential distribution of gasket contact stress

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Gasket contact-stress［MPa］

Figure10

 omparison of measured and estimatedC
leaks from gaskets

6. Discussion
6-1）‌Effect of nominal diameter of pipe flange
connection on axial bolt force fluctuation
Figure11 shows the values of the load factor wheninternal pressure is applied to the 2 inch, 4 inch,
8 inch, 12 inch, 16 inch, 20 inch, and 24 inch pipe
flange connections incorporating the No.GF300 gasket
calculated from FEM analysis. The average target
gasket contact-stress is 20 MPa, and the internalpressure is set to 2 MPa. The load factor shown on
the vertical axis is the increment rate of the axial bolt
force when an external force（in this case, internalpressure）is applied. A positive value means that theaxial bolt force increases, and a negative value
indicates that the axial force decreases. It was foundthat the load factor tends to decrease as the nominal
diameter of the pipe flange increases. This is because
the larger the nominal diameter of the pipe flange, theFigure9 Gasket contact-stress distribution obtained from FEM analysis

smaller the bending rigidity of the flange ring, and
16

No.36

flange rotation is likely to be promoted when internalpressure is applied, and as a result, the bolt is easily
contracted. Figure12 shows the gasket contact stress
distribution for each nominal diameter pipe flange.
The horizontal axis is the ratio of the gasket widthand is dimensionless. Under all dimensional conditions,the gasket contact-stress decreased when internalpressure was applied, but this became more apparent
as the nominal diameter increased. It is consideredthat the larger the nominal diameter, the larger thearea for receiving the internal pressure, the larger thethrust force, and the larger the value of the loadfactor, so that the ratio of the loss of gasket contactstress increases.
Figure13 shows the leakage estimated by the same
method as the result in Figure10 for a 2 inch to 24
inch pipe flange connections. The average value of thetarget gasket contact stress is 30 MPa, and thedividing the total leak by the gasket outer contact

Nominal diameter［inch］

Figure13 E
 ffect of pipe flange nominal diameter on leakage
amount per unit length

circumference. As the nominal diameter of the pipe
flange increases, the leakage per unit length increases,
but the vertical axis is not a logarithmic scale but alinear scale, and the difference is not so large inreality.
6-2）‌Comparison of sealing properties of pipeflange connections using No. GF300
and No. 6596V expanded graphite filledgasketLoad factor

Figure14 shows the relationship between the leakage
per unit length and the gasket contact-stress of thepipe flange connections using No. GF300 and No.
6596V expanded graphite filled gasket. As before, thepipe flange connection size is ASME class 300 24
inches and the internal pressure is 2 MPa. The

Figure11Nominal diameter［inch］

validity of the FEM analysis method has been confirmed

 ffects of nominal diameter on load factor inEpipe flange connections

by comparing the FEM analysis and the experiment

Gasket width ratio

Figure12

17

for the pipe flange fastener using No. 6596V. It was

Leak rate［Pa・m3/s・m］

Gasket contact-stress［MPa］

Winter 2019No.36

leakage is the leak per unit length obtained by

Estimated leakage amount［Pa・m3/s・m］

Evaluation of Mechanical Properties and Sealing Performance of 24”Pipe Flange Connections with No.GF300 Gasket

 adial gasket contact stress distribution in theRconnection of each pipe flange nominal diameter

Gasket contact-stress［MPa］

Figure14 C‌ omparison of seal performance of each pipe
flange connection using No. GF300 and No. 6596V

Technical Papers

observed that when the gasket contact stress is（4） Using FEM analysis and basic gasket data, it was

smaller, the leakage rate is relatively large, but whenclarified that the larger the nominal diameter ofthe gasket contact stress is larger, the sealing

the pipe flange, the smaller the load factor andproperty of the pipe flange connection using thethe larger the leakage amount.

No. GF300 is better than that of the pipe flange（5） It was clarified that No. GF300 exhibits higher

connection using the No. 6596V. The pipe flange

sealing performance than a pipe flange

connection using expanded graphite, which has theconnection using an expanded graphite filled

filler material of No. 6596V, exhibits good sealingspiral wound gasket when a recommended

performance even with relatively small stress. On thesurface pressure of 35 MPa is applied. From theother hand, it is considered that the No. GF300 could

strength calculation, it was found that even in

not conform to the flange surface with a smaller

the pipe flange connection to which the spiralstress, but was able to when the gasket contact-stresswound gasket cannot be applied, the sealing

became larger, and exhibited a higher sealing

performance of GF300 is equal to or better thanproperty by compression of the material. From thethat when the spiral wound gasket is used.

strength calculations, some pipe flange connections
are not applicable for spiral wound gaskets. However,it was found that in these locations, the sealing
property of No.GF300 is same or better than that

1）T . TAKAKI, K. SATO, Y. YAMANAKA, T.
FUKUOKA, "Effects of Flange Rotation on the
Sealing Performance of Pipe Flange Connections",

7. Conclusions

ASME PVP Vol.478,（2004）, pp.121-128.
2）T . SAWA, N. OGATA, T. NISHIDA, "Stress

In this study, the mechanical properties of ASME

Analysis and Determination of Bolted Preload inclass 3000 24 inch pipe flange connection with No.

Internal pressure", Transactions of the ASME,

GF300 were investigated by experiment and FEM

Journal of Pressure Vessel Technology, Vol.124,

analysis, and the following conclusions were obtained.

（2002）, pp.22-27.

（1） In accordance with JIS B 2490, the compression3）T. KOBAYASHI, T. NISHIDA, Y. YAMANAKA,

characteristics and leakage gasket contact-stress"Effect of Creep-Relaxation Characteristics ofrelationship of No. GF300 were measured.

Gaskets on the Bolt Loads of Gasketed Joints",（2） ‌The leakage from the pipe flange connection was

ASME PVP Vol.457,（2003）, pp.111-118.

estimated from the above gasket characteristics

4）Ministry of Health, Labour and Welfare, "Law forand the gasket contact stress distribution results

Partial Amendment of the Order for Enforcement of

were obtained from the FEM analysis. In

the Industrial Safety and Health Law", Cabinet

addition, both results were in good agreement

Order No. 349（2008）.

with the experiment demonstrating the validityof the estimation method.

5）
Nippon Valqua Industries, Ltd., GASKET, Catalogue
No.YC08,（2016）.

（3） Through FEM analysis and experiments, it was6）K. SATO, A. MURAMATSU, T. KOBAYASHI,

clarified that the axial bolt force decreases due

T.SAWA,"FEM Stress Analysis and Sealing Perfor-

to flange rotation when internal pressure ismance of Bolted Flanged Connections using PTFE

applied to the 24 inch pipe flange connection

Blended Gaskets under Internal Pressure", PVP

with No. GF300. It was also shown that the FEM

2 015 - 4 52 6 8 , Proceeding of ASM E PV P 2 015

analysis results are in good agreement with theexperimental results.

Conference,（2015）.
7）K . SATO, T. SAWA, T. KOBAYASH I ", FEM
18Winter 2019obtained from the spiral-wound gasket.

8. References

No.36

Evaluation of Mechanical Properties and Sealing Performance of 24”Pipe Flange Connections with No.GF300 Gasket

S T R E S S A NA LY S I S of L ong- t er m S e a l i ng
Performance for Bolted Pipe Flange Connections

PVP2010-25499, Proceeding of ASME PVP2010
Conference,（2010）.

with P TFE Blended Gaskets under Elevated11）Y. OMIYA, T. SAWA, Y. TAKAGI", Stress Analysis

Temperature" PVP2016-63372, Proceeding of ASME

and Design of Bolted Flange Connections under

PVP 2016 Conference,（2016）.

Internal Pressure", PVP2014-28606, Proceeding of8）K . S AT O , T. S AWA , R . M O R I M O T O , T.

ASME PVP 2014 Conference,（2014）.

KOBAYASHI, "FEM Stress Analysis and Mechanical12）
Y. OMIYA, T. SAWA", Stress Analysis and Sealing

Characteristics of Bolted Pipe Flange Connections

Performance Evaluation of Bolted Pipe Flangewith PTFE Blended Gaskets Subjected to External

Connections with Smaller and Larger Nominal

Bending Moments and Internal Pressure", PVP2017-

Diameter under Repeated Temperature Changes",

65332, Proceeding of ASME PVP 2017 Conference,

PVP2014-28730, Proceeding of ASME PVP
2014, Conference,（2014）.

（2017）
9）Y . TAKAGI, T. SAWA, H. TORII, Y. OMIYA,

13）A . MURAMATSU, K. SATO, M. U. KHAN,"Effects of Scatter in Bolt Preload on the Sealing

T.SAWA,"FEM Stress Analysis and the Sealing

Performance of Pipe Flange Connections Under

Performance evaluation of Bolted Pipe Flange

Internal Pressure （Case Where the Nominal

Connections with Large Nominal Diameter Subjected

Diameter of Pipe Flange Connection is 20"）", PVP

to Internal Pressure", PVP2016-63407, Proceeding of

PVP2010- 25499, Proceeding of ASME PVP2010

ASME PVP 2016 Conference,（2016）.

Winter 2019

Conference, （2010）.
10）Y . TAKAGI, T. SAWA, H. TORII, Y. OMIYA,"Effects of Scatter in Bolt Preload on the Sealing
Performance of Pipe Flange Connections Under
Internal Pressure （Case Where the Nominal

14）Japanese Industrial Standards. JIS B 2490 "Testmethod for sealing behavior of gaskets for pipe
flanges",（2008）.
15）
A NSI / ASME B 16.5,"Pipe Flanges and Flanged
Fittings",（1996）.

Diameter of Pipe Flange Connection is 20"）",No.36

Kouji Satou
Corporate Research andDevelopment Group
Product Development
Division

Toshiyuki Sawa
Hiroshima University,
Professor Emeritus
19

Xing Zheng
China Research Institute
Seal Engineering
Development Group