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GPI Journal Vol. 2, No. 2
187
GPI Standards Committee
GPI7G-039 Published on Dec 27, 2016
Regular Article
Received on Aug 18, 2016.
Revised on Sep 26, 2016.
Accepted on Oct 9, 2016.
Featured Technology
FRP flange design (Part 1): Necessary strength and optimum structure
Yoshinori NISHINO1, Allen S CHIU2, Shinichi TAMURA1,
Masaki NISHINO1, Taiga TATSUMI1 1NBL Technovator Co., Ltd., 2NOV FGS Singapore (Pte) Ltd.
Abstract: Generally from the course of corrosion-resistant FRP pipe has been developed as an alternative material
of the corrosive metal pipe, combination with existing metal flange is required. Basically, by mating surfaces unified,
common commercialization can be achieved. So, after standards of PCD/ hole diameter of the bolt, a flange inner
and outer diameters are defined, from the specifications of unevenness of the flange contact surface, waterproof
function, applied bolts/ number, and the allowable pressure, product design is carried out.
Keywords: corrosion-resistant materials, FRP, flange, strength design of flameproof, sealed
1. Introduction
Fittings necessary to the piping is flange. Flange is made
from a metallic material or FRP (Fiber Reinforced Plastic)
material. The present study, optimal product design research
has been carried out to the reference flange of ASA150 and
ASA300 that the most commonly and frequently used in size
from the product which outer diameter of 25 mm up to about 3
m. As a result, as compared with the conventional FW molding
method or hand-layup molding method, the product was about
50% lighter, the quality was improved about twice. It should be
noted that the product introduced here is the write-once that it
is a pending patent application preparation.
In general flange molding, large compounds that the most
popular is FW molding method. Compression molding, such as
SMC is less than 10 inches of small size are common. This
study describes the optimum design method for flange products
with the latest molding technology of the new centrifugal
molding method (NBL company development called CW
method) and NMC molding method (NBL company
development) that the bulk of the material was compression-
molded.
2. Basic design conditions
Flange design basics bonded mains with the tapered working
surface is selected from the following conditions. (ASA150,
ASA300, JIS10 / 16K, such as international standards apply)
Figure 1 is a flange made in the thick of the hat-shaped called
Vanstone flange.
Its feature is simple and heavy, and shear stress of its
adhesive surface to tube surface shown in the figure will be
concentrated to the end since the rigidity balance of the joint
surface works, its adhesive strength should be weak. Figure 2
is called contact molded flange that plate thickness of its flange
surface is thin.
Its feature is that shear forces should be smoothed and
adhesive strength should be stronger since it is light we 1eight
and the adhesive surface is made of a scarf wrap shape.
Generally, it is said that corrosion resistant FRP pipe [1] have
been developed as a substitute material for corrosive metal tube,
it should be demanded to be used in combination with the
existing metal flange. Basically, the mating surfaces is to
become a possible common commercialized by being
standardized and unified, product design starts from ②③
specification after ① criteria is stipulated.
Fig 1 Vanstone Flange
Y. Nishino et al. / GPI Journal 2(2) (2016) 187-192
Global oil & gas Pipe Institute 188
«Flange Basic Specifications»:
① PCD of bolt · hole diameter, flange ID and OD
② flange contact surface of the irregularities, watertight
function
③ applied bolts and number, allowable breakdown
pressure
«Seal of the flange surface»:
Figure 3 shows a structure for joining using the O-ring on the
inside back-up ring and the groove over blanking the structure
of the new development.
Both have a seat surface seal structure that can be shared with
metal flange. The former is an existing structure, the latter is a
single & double O-ring that can be used in combination glove
was developed to common functions in the various flange
surfaces. A new O-ring seal (patent pending preparation).
Feature is that it can be applied to any flange surface, acceptable
breakdown pressure Max 10MPa of ASA150 / 300 is satisfied.
At the same time the seat surface pressure load is smaller than
a gland packing type, shown in Figure 4. Face seal structure of
the place where the packing over the flange entire surface of a
large bolt load burden for the seal. Small area gland packing of
the inner surface side open glove is small bolt load burden for
the seal.
«Flange of production»:
The system for manufacturing flanges are roughly 3 pattern.
Figure 5 shows an overview in the illustration. There is a most
primitive type hand lay-up molding method to perform, such as
drilling in the secondary processing after lamination of curing
the FRP in hand, in addition, the resin and the short glass fiber
were put in the rotary-type mold and be produced by centrifugal
casting called CW molding method [2, 3], in the filament
winding, there is a method of machining finishing such as hole
in the secondary processing followed by FW molded into a
mold of the outer surface.
In this study, we describe
CW molding method which is
most productive such as
possible one piece per one hour
(1-type) in the large flange with
fully automatic, which is
shown in Figure 6. In addition,
this is to report on the outcomes
of performing product design,
which was the basic O-ring
specification of contact flange
that material cost is inexpensive.
3. Basic design of the flange
Figure 7 is a flow diagram of a flange design. Since flange
provided in the conduit, performs enhancement layer design to
ensure acceptable distortion design of the corrosion-resistant
layer and corrosion-resistant layer needed to ensure the cost and
pipe design and durability further reduce the necessary
functions from quality assurance.
New 0-ring seal
Back up ring 0-ring seal
Fig 3 0-ring seal flange
Grand packing seal New groove grand packing seal
Fig 5 ASA 150/Maxφ3.5m-300/Maxφ1m,
Production System
Fig.6 Contact molded
flange
GPI Journal Vol. 2, No. 2
189
GPI Standards Committee
GPI7G-039 Published on Dec 27, 2016
Regular Article
Received on Aug 18, 2016.
Revised on Sep 26, 2016.
Accepted on Oct 9, 2016.
Furthermore, for the total cost reduction, it is necessary to
adhere to the design conditions of 4 items shown in Figure 7.
From design basic conditions, for example standard flange
such as ASA150 is applied tube ID and flange OD and bolts
have been established. Therefore, it should be started from
structural design to reduce the load on the flange bolts required
to seal the flange surface in order to increase the first
performance.
3.1 O-ring seal design
Figure 8 is a significant seal theory of the smallest O-ring of
the load. O-ring, if added to sealing pressure Pci the seat surface
required initially, by automatically own deformation required
seal surface pressure Pc (about 1.5Ps fold pressure load) in
proportion to the pressure load Ps, it is maintained. Then, O-
ring and gasket is a theory of history that stability is obtained in
the seat surface seal of the small area on the same principle.
Since the only drawback is made from the material is weak
rubber, short-term maximum pressure is about 20MPa and low.
However, it is necessary and sufficient for the pipe flange.
3.2 Flange strength design
Load applied by the internal pressure load P1 of the flange,
in the axial direction shown in Figure 9, axial force Fs generated
by a seal that acts on the tube by the clamping force F and the
internal pressure by the flange bolts and each stress of axial
force F-Fs acting on the tube by the internal pressure is
generated.
Bolt maximum load F requires a stress relief, such as a bolt
washer equal to or less than the allowable compressive stress
200MPa of FRP flange.
Various stress generated in the flange structural member,
the axial pulling force on the tube via a junction surface
between the bolt load, the tensile force in the circumferential
direction due to internal pressure, resulting from the combined
load due to compression force in the thickness direction.
Adhesive shear stress is generated on the weakest member of
joining surface. This shear stress is precisely consists frictional
force between the laminated and the adhesive shearing force
Fig 4 Grand packing Seal fiange
Fig 7 Strength of Flange Design System4)
Fig 8 Basic Mechanism Design of Rubber Seal4)
Fig 9 Strength Design of Flange
Fig 10 Adhesive Strength of Joint System &
Adhesive Length7)
Y. Nishino et al. / GPI Journal 2(2) (2016) 187-192
Global oil & gas Pipe Institute 190
between materials. Figure 10 shows the characteristics.
Effective bonding length is eight times the length of the tube
thickness at the scarf wrap connection structure in the 1/16 taper
is ideal bonding length. Subject of the other member is a
bending stress. From the fact that these analysis and theoretical
calculation method has already become apparent to by GPI
technology standard by the author, the details will be omitted.
Formulas required for strength design is shown in Figures 9 and
12.
3.3 Inner surface peeling (prevention of corrosion
degradation)
Structural considerations of the bonding flange, shown in
Figure 11, since the secondary bonding or the like thin
laminated resin (Mylar) there is a peeling of the laminate by the
high-speed running water. The flow rate of the Mylar peeling
prevention is usually not more than 3m / s, cavitation, erosion,
where corrosion environment deteriorates, the lamination
structure shown in Figure 13 is antiaging. The thickness of the
case corrosion-resistant layer criteria PS-15-69 is valid.
Mylar is due to decrease by incomplete curing and in
strength of the bonding portion. If these measures are cleared,
allowable flow rate is applied to 6 m / sec. Incidentally, Figure
13 shows the relationship between the allowable flow rate and
the laminated thickness of the resin. They are already published
written by authors that details of technology standard that got
from a lot of experience will be omitted.
3.4 Stress calculation
Performing stress calculation flange structural member is
shown in Figure 9. Figure 11 shows a theoretical calculation
formula for the mechanical properties to be used in the design
of the laminated material usable in CW molding. It can be used
for the simulation of the laminate strength design of the
materials used. In other words, it can be calculated allowable
strength of the laminate material to the design of the selected
material. Since it is significant theoretical formula that has
already been published by authors, omitted in this paper. Figure
Fig 11 Position and Mechanism of Internal7)
Delamination for Transfer Line
Fig 12 Approximate equations for material constant applied for the design of reinforced layer6)
Fig 13 Delamination Characteristics of
Secondary Lamination and Design for Delamination
Prevention7)
GPI Journal Vol. 2, No. 2
191
GPI Standards Committee
GPI7G-039 Published on Dec 27, 2016
Regular Article
Received on Aug 18, 2016.
Revised on Sep 26, 2016.
Accepted on Oct 9, 2016.
14 is an approximate theoretical formula and the approximate
stress analysis model of the flange structure. Allowable strength
of the design laminate material according to Figure 11 to select
the calculated value of the generated stress shown in Figure 9,
optimal choice value of commodity durability performance
(AWWA: Sf; 5 times, GPI: Life 10 year (Sf: 3 times), Life 40
year (Sf: 5 times)) is obtained.
4. Structure of optimal FRP flange
Optimum FRP flanges are required to share with metal
flanges which is frequently used, such as ASA150 / 300,
JIS16K. Contact flange is better that its bolt length is short from
the cost and the amount of material is less. Single & double ring
of the new O-ring system that the seat surface can be shared
with the metal flange is recommended to seal format that is the
least the seat ring area, less bolt burden of the necessary load.
Since stress that occurs is a multi-directional to join the radial
direction from the load bending the circumferential direction
and the axial direction, to the laminated material consulting
these flanges, the glass fiber to be applied in the short-fiber,
high-strength multi-end roving of 7 to 25 mm are suitable.
In other words, this shows the new O-ring system shown
in Figure 3. The flange of these selected design structure with
the exception of the grinding processing of secondary adhesive
surface, for all that can be integrally molded is a centrifugal
casting method using a centrifugal molding. Using the fast
curing vinyl ester resin matrix resin, contact flanges optimally
designed can be produced at the fastest.
On the other hand, here it is omitted the description of the
detailed design result, if flange bolts to be used by the general
steel (yield point is 200MPa) to use, for example, in the
ASA150 standard flange, and to apply the AWWA durability
criteria, apply pressure application diameter 3MPa can design
up to about 3.5 m. In ASA300 standard applied pressure can
design application diameter 5MPa up to about 1m. Furthermore,
by using about twice the high-strength bolt, is also allowable
breakdown pressure is doubled in proportion, more high tensile
bolt is not applicable to exceed an allowable compressive
strength of the FRP laminate material.
5. Conclusion
The results obtained in this study, the standard in the FRP
flange ASA150 class of the pipe flange standard about 3.5 m,
in the 300 class can be designed up to about 1 m. Optimal design
results is O-ring seal of contact type flange. Fit production
method is suitable is produced by centrifugal casting. However,
small diameter (about 400 ㎜ below) the combination of the
compression molding method is effective. Use material is glass
fiber and fast curing of the vinyl ester resin of short fiber is
suitable, the epoxy resin is also possible. If you change the
flange bolts in high tension, breakdown pressure of the same
materials used in the same design conditions can be designed
up to 2 times at the maximum. The results of this research
conventional design, as compared to products made in the
manufacturing process, it is possible to obtain about 50% less
product weight(material cost) about twice the allowable
breakdown pressure (performance), and the production rate it
became clear that take about 10 times higher.
In the second report, we will describe in detail the specific
design and development products. .
References
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Tubular for Oil & Gas Production, Japan Reinforced
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[2] Masaki Uhara, Taiga Tatsumi, Masaki Nishino, Shinichi
Tamura, Yoshinori Nishino, Study on the production of
the flange by the centrifugal forming method (Part 1),
GPI Journal Vol. 1, No. 2, pp. 262-267 (2015).
[3] Masaki Uhara, Taiga Tatsumi, Masaki Nishino,
Shinichi Tamura, Yoshinori Nishino, Study on the
production of the flange by the centrifugal forming
method (Part 2), GPI Journal Vol. 1, No. 2, pp. 268-273
(2015).
[4] Yoshinori Nishino, Merits of and design method for
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[5] Takashi Shimosakon, Shinichi Tamura, Yoshinori
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Y. Nishino et al. / GPI Journal 2(2) (2016) 187-192
Global oil & gas Pipe Institute 192
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