ASME PVP 2016-Awarded Paper

1. Introduction

ceremony; Figure2 shows the certificate ofcommendation given at the ceremony.

In 2016, we contributed and presented the paper

This article introduces the paper’s contents and the“FEM Stress Analysis and the Sealing Performance

future prospects for basic research regarding thisEvaluation of Bolted Pipe Flange Connections withtheme.

Large Nominal Diameter Subjected to Internal
Pressure,”which examines the mechanical behavior offlange connections with large nominal diameter, at thePressure Vessels & Piping Conference（PVP）. PVP isWinter 2018a technical divisionof the American Society ofMechanical Engineers（ASME）.
ASME’s PVP, which consists of 12 committees, holds a
professional meeting annually, at which various papers
are presented. Among the papers presented,
approximately 10 are nominated and receive awards ofNo.34

excellence. Our paper received an award from theComputer Technology & Bolted Joints TechnicalCommittee, one of the 12 committees.
Figure1 shows a picture of the commendation

Figure2 ＡＳＭＥＰＶＰＡＷＲＤ

2. Approaches to basic research
Seal engineering is our core technology. Using thistechnology, we are developing and expanding ourservices associated with flange working methods tosuit the needs of customers’ plant operation.
The tightening force of a bolt varies depending on thesize of the flange. Therefore, different tools should be used
A Valqua staff member receives a commendation from Mr.
Trevor G. Seipp, Honors and Awards Chair（left）.
Figure1 Commendation ceremony
3

to fasten bolts depending on the flange size. We propose
optimal tools that suit the customer’s usage environment,
and such proposal work is one of our services.

Commentary

These services have been gradually recognized in themarket, and so we began to receive inquiries not only

3. ASME PVP 2016-awarded paper
In this study, stress analyses using the finite element

including optimal fastening procedures, regarding themethod（FEM）were conducted to propose a method

fastening of flanges with large nominal diameters.

to evaluate the sealing performance and develop a

However, more bolts are used in fastening flanges withbolt-tightening method.

large nominal diameters, and under such conditions, a

When gaskets are compressed, internal stressmarked phenomenon unique to flange tightening,develops. Since the sealing performance of a flangecalled elastic interaction, occurs. In elastic interaction,connection is considered to be determined by thisaxial bolt force, which secures the sealing performanceinternal stress, stress analyses using the finite elementof the gasket, is greatly affected by the tightening

method（FEM）were conducted to calculate the flange

force of the neighboring bolts. Therefore, more leakage

connection’s contact pressure when pressure is applied

troubles are known to develop regardless of theto the internal side of the flange connection throughgasket’s performance. For this reason, basic research isfluid after the gaskets are compressed using bolts. In

essential in order to propose optimal flange working

the analyses, spiral-wound gaskets containing foamedmethods. Based on such research, the mechanicalcarbon filler（No. 6596V）and joint sheet（No. 6500）,

behavior associated with flange connections will be

and the analysis code ABAQUS were used.

elucidated and bolt tightening methods will be

Figure4 is a model of a flange connection under inner

established.

pressure（P）.

Therefore, we built 24-inch flange connections asFigure5 shows an FEM model of element

shown in Figure 3. The 24-inch flange connection is thedecomposition. In the finite element analysis, we took

largest of the standard flanges. We then conducted

the symmetrical properties into account to divide thestress analyses using the finite element methodmodel in half in the axial direction and in 1-bolt length（FEM）to predict the flange’s seal performance. As ain the circumferential direction.

result, we established the method and published aNo.34

paper on it.
Stress analysis using the finite element method（FEM）involves calculating the deformation behaviorof a structure based on its mechanical characteristics
in order to predict changes.

Figure324-inch flange connection

Winter 2018about tool selection but also flange working methods,

Figure4

FEM model of a flange connection
4

ASME PVP 2016-Awarded Paper

Figure5 FEM model

Figure7 O utline illustration of the test equipment
stipulated by JIS B 2490

The basic leakage amount of the gasket was calculated
according to JIS B 2490.
Figure7 illustrates an outline of the test equipment
stipulated by JIS B 2490.

Winter 2018

Figure8 shows the results from a test conductedaccording to JIS B 2490; the bold line indicates thebasic leakage amount of the gasket, which wascalculated as the leakage amount plotted against thegasket’s contact pressure on unloading.
This basic leakage amount of the gasket wasNo.34

Figure6 contact gasket stress distribution of the spiralwound gasket in the radial direction

compared with the leakage amount obtained by anexperiment, in which the leakage amount of the flange

Figure6 shows the contact gasket stress distribution ofconnection was calculated based on the averagea spiral-wound gasket in the radial direction. The

contact-pressure pattern of the gasket shown inhorizontal axis indicates dimensionless numbers. TheFigure6.

number was calculated by dividing the length between
the center and the pressure point in the radial
direction by the gasket’s internal diameter. On theassumption that two flanges were tightened in parallelwith each other, this study was conducted under thecondition that the contact gasket stress does notchange much in the circumferential direction, but onlyin the radial direction.
This figure indicates the trend that the larger theflange, the greater the contact pressure on the side of
the gasket’s outside diameter. This trend indicates
that, after bolt tightening, the application of pressure
through fluid generates rotation which deforms flanges
in the circumferential direction.
5

Figure8 Measurements of basic leakage amount of spiral-wound gaskets

Commentary

customers, and then propose the optimal working
methods.
Receiving an award for this paper showed that ourstudy is highly evaluated in the United States, wheresealing technology is actively studied. This highevaluation not only raises the brand profile of Valqua
but also verifies our evaluation methods and working
methods regarding flange connections. We received aninquiry regarding tightening methods for flanges withlarge nominal diameters from a major U.S. oil company
soon after presenting this paper, indicating strong
Figure9 C omparison of the results from the experimentwith the analysis resultsinterest in this theme. This quick reaction indicatesthat even major oil companies have problems
regarding tightening methods for flanges with large

with the analysis results.

nominal diameters and wish to collaborate with

The red line represents the spiral-wound gasket andcompanies which possess advanced sealing technology.

the blue line represents the joint sheet; both gaskets

Cooperation with major oil companies might be

had less leakage when the gaskets’contact pressure

achieved by strengthening Valqua’s technologicalincreased. The experimental and analysis results

foundation using the results of this study.

matched closely, indicating the validity of theanalytical method.
With this analytical method, it is possible to predict the5. Conclusion

leakage amount of a flange connection. Also, theIn this study, an ideal flange connection wasresults indicate that setting a higher initial tightening

established as an ideal model, assuming the flange andforce of the bolts is effective for reducing the leakage

bolts had no scratches and the gasket was tightened

amount.

uniformly.
However, in actual working conditions, we cannot

4. Future prospects

fasten such ideal flanges; for example, gaskets arecompressed unevenly. In future, we aim to determine

Currently, we are studying how to apply these results

the effects of such uneven fastening on the sealing

to our proposal services regarding flange working

performance of flange connections, and to establish

methods, and are now introducing these services. Insolutions to on-site problems.

the long run, we believe that application of the results

In addition, since the thermal burden and externalof this basic research will allow us to evaluate andforce can affect actual piping, we intend to take theseanalyze working methods, which are difficult foreffects into account in further studies.

Akira Muramatsu
Ｈ＆Ｓ BUSINESS GROUP
6

Winter 2018

Figure9 compares the results from the experimentNo.34