During the creation.

Experimental Studies on Vibration Tseting
of Pipe Joints Metal Gaskets

NAN BU, NAOHIRO UENO, SATORU KOYANAGI
MASAHIRO iCHIKI, OSAMU FUKUDA, and MORITO AKIYAMA

National Institute of Advanced Industrial Science and Technology
807-1, Shuku-machi, Tosu, Saga, 841-0052 JAPAN (bu@ieee.org)
TOKi Engineering Co., Ltd.
1-18-4F, Hie-machi, Hakata-ku, Fukuoka, 812-0014 JAPAN

  Abstract: Pipe joints have been widely utilized in industrial plants, where dynamic load of vibration is considerably
  harmful for sealing performance. However, there is a lock of design codes and experimental procedures developed
  for vibration testing of pipe joints. This paper proposes an experimental setup for testing of pipe jpints, which ose
  metal gaskets, in vibratory conditions. Also, a flexible piezoelectric film sensor is introduced into this test rig for
  monitoring of stress in pipes. With the proposed test rig, vibration testing of pipe joints can be conducted, therefore
  further investigations such as fatigue analysis of the concatc surfaces, and computational analysis of metal gaskets
  and seal devices are readily available. Finally. some experimental results of a gasketed flange joint, which uses a
  1.5-inch diameter stainless steel gasket, were reported.

  Key-Words: Pipe joints, Metal gasket, Vibretion testing, Sealing performance, Leak-free.

1 Introduction

Pipe joints are one of the most frequently used ele-
mens in power plants, food processing equipment,
pharmaceutical industries, etc. Elastomeric material
has long predominated the field of static sealing tech-
nology. Due to the progress in industrial techniques,
new demands have gone up rapidly for pipe joints
working under high pressure, high vacuum, very high
temperature, and various chemical operation conde-
tions. To deal with these demands, a variant of metal
and semi-metallic gaskets have been developed [1]-
[3]. Although these gaskets offer a high level of seal-
ing performance, since they are usually designed to
work with flanges, which are made of much stiffer
materials, it is recommended not to reuse these gas-
kets due to unrecoverable deformation in gasket con-
tact surfaces.
   Recently, a new concept of metal gasket, called
SUS DETOP stainless steel gasket, was proposed
[4]. During assembly process, an annular seal line is
formed with an tapered face of gasket and the edge of
inner wall of the groove in ferrule (see Fig. 1). Since
this gasket uses the same stainless steel material as
pipe ferrules, good recovery characteristics can be ex-
pected.
   In most pipe systems, vibration is a critical prob-
lem [5],[6]. At pipe joints, vibration-induced loos-
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SUS De TOP is the trademark of TOKi Engineering Co.,Ltd.

ening of joint assembly may finally result in sealing
failure. Especially, in case of metal gaskets, vibration
may also cause fluctuation of gasket stress and fatigue
of sealing surfaces. in order to achieve reliable sealing
performance, pipe joints, especially those using metal
gaskets, should be examined under vibration condi-
tions.
  So far, many researches have been conducted to
innestigate characteristics of gaskets using experimen-
tal methods and/or computational analysis, such as fi-
nite element modeling (FEM) [7]-[10] Also, Interna-
tional organizations like ASME, CEN, and ISO have
been engaged in developing design and test standards
for gaskets and pipe joints [11]-[13]. However,most
of the concentration has been focused on hydraulic
leak testing and stress-strain terms in pipe joints un-
der internal pressurized and unpressurized conditions,
such as bolt stress and contact stress of gasket [7]-
[9]. Although, Nash and Abid [7] had studied com-
binations of operation loads on gasketed flange joints,
where load of bending moment was considered, it was
just examination of static load. Fatigue of gasket was
examined under pulsate cycle of working pressure,
howener, bending moment was not considered in this
study, and the gasketsused were non-metallic [10].
  To the authors' knowledge, there is no guideline
and standard issued for testing of pipe joints with
metal gaskets under vibration operation conditions
yet. In this paper, we propose a testing method for



Figure 1:  The SUS DE TOP metal gasket.  (a) A
schematic view of a pipe joint assembled with tow fer-
rules (Fa: assembly foree). (b) An enlarged view of
the seal area.

examination of metal gasket's sealing performance in
cyclic vibration conditions. The frequencies and am-
plitudes of vibration are considered as parameters in
this testing method. Also, aflexible piezoelectric film
sensor [14] is introduced into the proposed test rig to
monitor stress of pipes. With the proposed merhod,
vibration testing of a xariant of gasketed flange joints
and pipe fittings can be conducted, Based on the ex-
perimental results, further investigations such as fa-
tigue analysis of the contact surfaces, and detailed re-
searches combined with FEM analysis of metal gas-
kets and seal devices are avalable.
   This paper is organized as follows: the next sec-
tion will briefly introduce the SUS DE TOP stain-
less steel gasket, which is used in the experiments
in this paper.  Then, Section 3 describes the pro-
posed vibration test rig and the experimental prose-
dite. Some preliminary experimental results of our
study are given in Section 4. Finally, Section 5 con-
cludes this paper.


2 The SUS DE TOP Metal Gasket

The SUS DE TOP type of metalgasket is designed for
ferrules or flanges with grooves on the contact sur-
faces.Fig. 1 depicts a schematicview of a pipe joint
that consists of a gasket and two ferrules. For hoints
using ferrules, assembly can be made by an adjustable
two or three-part clamp with a tapered ring or two
loose hubbed flanges using bolts.
   One of the major features of this metal gasket is
the seal area that is formed with the gasket's taper-face
and the inner edge of flange groove. Since sealing per-
formance is proportional to the contact stress at the in-
terface between the gasket and the flanges, the smaller
the seal area is, the higher the contact stress may be.
An annual seal line may be the best choice for seal
area, sepecially in case that both gasket and flanges


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