ISO 14692-3: GRP Piping System Design Standard

INTERNATIONAL
STANDARD
ISO
14692-3
Second edition
2017-08
Petroleum and natural gas
industries — Glass-reinforced plastics
(GRP) piping —
Part 3:
System design
Industries du pétrole et du gaz naturel — Canalisations en plastique
renforcé de verre (PRV) —
Partie 3: Conception des systèmes
Reference number
ISO 14692-3:2017(E)
© ISO 2017
ISO 14692-3:2017(E)
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© ISO 2017 – All rights reserved
ISO 14692-3:2017(E)
Contents
Page
Foreword .................................................. ................................................... ................................................... ................................................... ............................... v
Introduction .................................................. ................................................... ................................................... ................................................... ..................... vi
1
2
3
4
Scope .................................................. ................................................... ................................................... ................................................... ...................... 1
Normative references .................................................. ................................................... ................................................... .............................. 2
Terms and definitions .................................................. ................................................... ................................................... ............................. 3
Layout requirements .................................................. ................................................... ................................................... ................................ 3
4.1
4.2
4.3
4.4
4.5
4.6
5
Hydraulic design .................................................. ................................................... ................................................... ........................................... 7
5.1
5.2
5.3
5.4
5.5
6
General .................................................. ................................................... ................................................... ................................................... 7
Flow characteristics .................................................. ................................................... ................................................... .................... 7
General velocity limitations .................................................. ................................................... ................................................... . 7
Erosion .................................................. ................................................... ................................................... ................................................... 8
5.4.1 General ................................................... ................................................... ................................................... ............................. 8
5.4.2 Particulate content .................................................. ................................................... ................................................... . 8
5.4.3 Piping configuration .................................................. ................................................... ................................................ 8
5.4.4 Cavitation .................................................. ................................................... ................................................... ....................... 8
Water hammer ................................................... ................................................... ................................................... ............................... 8
Generation of design envelopes .................................................. ................................................... ................................................... .... 9
6.1
6.2
6.3
6.4
7
General .................................................. ................................................... ................................................... ................................................... 3
Space requirements .................................................. ................................................... ................................................... .................... 4
System supports ................................................... ................................................... ................................................... ............................ 4
4.3.1 General ................................................... ................................................... ................................................... ............................. 4
4.3.2 Pipe-support contact surface .................................................. ................................................... ........................... 5
Isolation and access for cleaning .................................................. ................................................... ........................................ 5
Vulnerability .................................................. ................................................... ................................................... ...................................... 5
4.5.1 Point loads .................................................. ................................................... ................................................... ..................... 5
4.5.2 Abuse ................................................... ................................................... ................................................... ................................. 5
4.5.3 Dynamic excitation and interaction with adjacent equipment and piping ................... 6
4.5.4 Exposure to light and ultraviolet radiation .................................................. ............................................. 6
4.5.5 Low temperatures and requirements for insulation .................................................. ...................... 6
Fire and blast .................................................. ................................................... ................................................... .................................... 6
Partial factors .................................................. ................................................... ................................................... ................................... 9
6.1.1 Design life .................................................. ................................................... ................................................... ....................... 9
6.1.2 Chemical degradation .................................................. ................................................... ............................................. 9
6.1.3 Fatigue and cyclic loading .................................................. ................................................... ................................... 9
Part factor, f2 ................................................... ................................................... ................................................... ................................... 10
Combinations of part factor and partial factors .................................................. ................................................... . 11
Design envelope .................................................. ................................................... ................................................... .......................... 11
Stress analysis .................................................. ................................................... ................................................... .............................................. 13
7.1
7.2
7.3
7.4
7.5
7.6
7.7
Analysis methods .................................................. ................................................... ................................................... ....................... 13
Pipe stress analysis so ftware .................................................. ................................................... .............................................. 14
Analysis requirements .................................................. ................................................... ................................................... ........... 14
Flexibility factors ................................................... ................................................... ................................................... ....................... 14
Stress intensification factors .................................................. ................................................... ............................................... 14
Modelling fittings .................................................. ................................................... ................................................... ....................... 15
Allowable deflections .................................................. ................................................... ................................................... ............. 15
7.7.1 Vertical deflection in aboveground piping systems .................................................. ...................... 15
7.7.2 Vertical deflection in buried piping systems ................................................... ..................................... 15
7.8 Allowable stresses .................................................. ................................................... ................................................... ..................... 16
7.9 External pressure .................................................. ................................................... ................................................... ....................... 19
7.10 Axial compressive loading (buckling) .................................................. ................................................... ......................... 20
7.10.1 Shell buckling .................................................. ................................................... ................................................... ........... 20
7.10.2 Euler buckling .................................................. ................................................... ................................................... ......... 20
© ISO 2017 – All rights reserved
iii
ISO 14692-3:2017(E)
7.10.3 Buckling pressure — Buried piping .................................................. ................................................... ........ 21
7.10.4 Upheaval buckling pressure .................................................. ................................................... ........................... 22
7.11 Longitudinal pressure expansion ................................................... ................................................... .................................. 23
8
Other design aspects .................................................. ................................................... ................................................... ............................. 23
8.1
8.2
9
Fire ................................................... ................................................... ................................................... ................................................... ...... 23
8.1.1 General ................................................... ................................................... ................................................... .......................... 23
8.1.2 Fire endurance .................................................. ................................................... ................................................... ........ 24
8.1.3 Fire reaction .................................................. ................................................... ................................................... .............. 24
8.1.4 Fire-protective coatings .................................................. ................................................... ..................................... 25
.................................................. ................................................... ................................................... ........................... 25
S tatic electricity
Installer and operator documentation ................................................... ................................................... ................................. 26
(normative) Cyclic de-rating factor — A 3 .................................................. ................................................... ......................... 27
Annex B (normative)
f
f
................................................... ........... 29
Annex A
F
l
e
x
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b
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t
y
a
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s
Bibliography .................................................. ................................................... ................................................... ................................................... .................. 36
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© ISO 2017 – All rights reserved
ISO 14692-3:2017(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work o f preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters o f
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
di fferent types o f ISO documents should be noted. This document was dra fted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some o f the elements o f this document may be the subject o f
patent rights. ISO shall not be held responsible for identi fying any or all such patent rights. Details o f
any patent rights identified during the development o f the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is in formation given for the convenience o f users and does not
constitute an endorsement.
For an explanation on the voluntary nature o f standards, the meaning o f ISO specific terms and
expressions related to con formity assessment, as well as in formation about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www.iso.org/iso/foreword.html .
This second edition cancels and replaces the first edition (ISO 14692-3:2002), which has been
technically revised. I t also incorpo rates the Technical C o rrigendum I SO 1 469 2 - 3 : 2 0 0 2 /C o r 1 : 2 0 0 5 .
This document was prepared by Technical Committee ISO/TC 67, Materials, equipment and offshore
structures for petroleum, petrochemical and natural gas industries
equipment and systems
.
A list of all the parts of ISO 14692 can be found on the ISO website.
© ISO 2017 – All rights reserved
, Subcommittee SC 6, Processing
v
ISO 14692 -3 :2 017(E)
Introduction
T he obj e c tive o f th i s do c ument i s to en s u re that pipi ng s ys tem s , when de s igne d u s i ng the comp onents
qua l i fie d i n I S O 14 69 2 -2 , wi l l me e t the s p e c i fie d p er formance re qui rements . T he s e pipi ng s ys tem s a re
de s igne d
for u s e i n oi l and natura l gas i ndu s tr y pro ce s s i ng a nd uti l ity s er vice appl ic ation s . T he mai n
users of the document will be the principal, design contractors, suppliers contracted to do the design,
cer ti fyi ng authoritie s a nd govern ment agenc ie s .
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vi
© ISO 2017 – All rights reserved
INTERNATIONAL STANDARD
ISO 14692-3:2017(E)
Petroleum and natural gas industries — Glass-reinforced
plastics (GRP) piping —
Part 3:
System design
1 Scope
This
do c u ment
give s
re com mendation s
gu idel i ne s
apply
to
layout
for
the
de s ign
d i men s ion s ,
of
GRP
pipi ng
s ys tem s .
hyd rau l ic
de s ign,
s truc tura l
T he
re qu i rements
de s ign,
de tai l i ng ,
a nd
fi re
endu ra nce, s pre ad o f fi re and em i s s ion s a nd control o f ele c tro s tatic d i s ch arge .
T h i s do c ument i s i ntende d to b e re ad i n conj u nc tion with I S O 14 69 2 -1 .
Guidance on the use of this document can be found in Figure 1
steps 5 and 6 in ISO 14692-1:2017, Figure 1.
© ISO 2017 – All rights reserved
, wh ich i s a more de tai le d flowch ar t o f
1
ISO 14692-3:2017(E)
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Figure 1 — Guidance on the use of this document
2
Normative references
T he
fol lowi ng do c u ments are re ferre d to i n the te x t i n s uch a way that s ome or a l l o f thei r content
con s titute s
re qu i rements
o f th i s do c u ment.
For date d re ference s ,
on ly the e d ition c ite d appl ie s .
For
undate d re ference s , the l ate s t e d ition o f the re ference d do c u ment (i nclud i ng a ny amend ments) appl ie s .
ISO 14692-1:2017, Petroleum and natural gas industries — Glass-reinforced plastics (GRP) piping — Part 1:
Vocabulary, symbols, applications and materials
2
© ISO 2017 – All rights reserved
ISO 14692-3:2017(E)
ISO 14692-2:2017, Petroleum and natural gas industries — Glass-reinforced plastics (GRP) piping — Part 2:
Qualification and manu facture
ASTM D2992,
Standard Practice for Obtaining Hydrostatic or Pressure Design Basis for Fiberglass (GlassFiber-Reinforced Thermosetting-Resin) Pipe and Fittings
ASTM D2412,
Standard Test Method for Determination of External Loading Characteristics of Plastic Pipe
by Parallel-Plate Loading
AWWA Manual M45, Fiberglass pipe design
3
Terms and definitions
For the pu rp o s e s
o f th i s do c u ment,
the term s ,
defi n ition s ,
s ymb ol s
and ab breviate d
term s
given i n
I S O 14 69 2 -1 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at http://www.iso.org/obp
— IEC Electropedia: available at http://www.electropedia.org/
4 Layout requirements
4.1
General
GRP pro duc ts a re proprie tar y and the choice o f comp onent s i z e s , fitti ngs and materia l typ e s c an b e
l i m ite d dep end i ng on the s uppl ier. Po tentia l vendors s hou ld b e identi fie d e arly i n de s ign to de term i ne
p o s s ible l i m itation s o f comp onent avai labi l ity. T he level o f engi ne eri ng s upp or t that c an b e provide d b y
the s uppl ier shou ld a l s o b e a key con s ideration du ri ng vendor s ele c tion .
Where
p o s s ible,
pipi ng s ys tem s
s hou ld
ma xi m i z e
the u s e
o f pre fabric ate d
s p o olpie ce s
to
for
i n s ta l lation
(“c ut
m i ni m i z e
the amount of site work. Overall spool dimensions should be sized taking into account the following
considerations:
— limitations of site transport and handling equipment;
— installation and erection limitations;
—
l i m itation s
c au s e d
requirements).
by
the
ne ce s s ity
to
a l low
a
fitti ng
T he de s igner s ha l l eva luate s ys tem l ayout re qu i rements
pipi ng s ys tem s ava i lable
tolerance
i n rel ation to the prop er tie s
to
fit”
o f proprie tar y
from manu fac tu rers , i nclud i ng but no t l i m ite d to the fol lowi ng:
a) axial thermal expansion requirements;
b) ultraviolet radiation and weathering resistance requirements;
c) component dimensions;
d)
j oi nti ng s ys tem re qu i rements;
e) support requirements;
f) provision for isolation for maintenance purposes;
g) connections between modules and decks;
h)
fle xi ng duri ng l i fti ng o f mo du le s;
© ISO 2017 – All rights reserved
3
ISO 14692-3:2017(E)
i) ease of possible future repair and tie-ins;
j)
vu l nerabi l ity to ri sk o f da mage duri ng i n s ta l lation and s er vice;
k)
fi re p er formance;
l) control of electrostatic charge.
T he hyd ro te s t provide s the mo s t rel iab le me a n s o f as s e s s i ng s ys tem i nte grity. Whenever p o s s ible, the
s ys tem shou ld b e de s igne d to enable pre s s ure te s ti ng to b e p er forme d on l i m ite d p a r ts o f the s ys tem
as s o on
as
i n s ta l lation
o f tho s e
p a r ts
i s comple te .
This
i s to
avoid
a fi na l
pre s s u re
te s t late i n the
con s truc tion work o f a large GRP pipi ng s ys tem, when problem s d i s covere d at a l ate s tage wou ld have a
ne gative e ffe c t on the overa l l proj e c t s che du le .
4.2
Space requirements
The designer shall take account of the larger space envelope of some GRP components compared to
s te el . S ome GRP fitti ngs have longer l ay leng th s and are prop or tiona l ly more bu l ky th an the e qu iva lent
me ta l
comp onent
and may b e d i ffic u lt to
accom mo date
with i n
con fi ne d
s p ace s .
I f appropri ate,
problem c an b e re duce d b y fabric ati ng the pip ework or pipi ng as an i ntegra l s p o olpie ce i n the
the
fac tor y
rather than as s embl i ng it from the i nd ividua l pip e fitti ngs .
I f s p ace i s l i m ite d, con s ideration shou ld b e given to de s ign i ng the s ys tem to op ti m i ze the attribute s o f
both GRP and metal components.
4.3
System supports
4.3.1
General
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GRP pipi ng s ys tem s c an b e s upp or te d u s i ng the s ame pri ncip le s a s tho s e
for me ta l l ic pipi ng s ys tem s .
H owever, due to the proprie ta r y nature o f pipi ng s ys tem s , s ta nda rd- s i z e s upp or ts wi l l no t ne ce s s a ri ly
match the pipe outside diameters.
T he fol lowi ng re qu i rements and re com mendation s app ly to the u s e o f s ys tem s upp or ts .
a) Supports shall be spaced to avoid sag (excessive displacement over time) and/or excessive vibration
for the de s ign l i fe o f the pipi ng s ys tem .
b) In all cases, support design shall be in accordance with the manufacturer’s guidelines.
c) Where there are long runs, it is possible to use the low modulus of the material to accommodate
f
and guided. In this case, the designer shall recognize that the axial expansion due to internal
f
anchors.
a xi a l exp a n s ion and el i m i nate the ne e d
pre s s u re
d)
Va lve s
is
now
re s tra i ne d
and
or o ther he av y attache d
the
or e xp an s ion j oi nts , provide d the s ys tem i s wel l anchore d
corre s p ond i ng
th r u s t
lo ad s
are
p ar tly
tran s erre d
e qu ipment s ha l l b e ade quately a nd , i f ne ce s s ar y,
to
the
i ndep endently
supported. When evaluating valve weight, valve actuation torque shall also be considered.
NO TE
S ome va l ve s a re e qu ipp e d wi th he av y co ntrol me ch a n i s m s lo c ate d
and can cause large bending and torsional loads.
fa r from the pip e centrel i ne
e) GRP piping shall not be used to support other piping, unless agreed with the principal.
f)
GRP pipi ng s ha l l b e ade quately s upp or te d to en s ure th at the attach ment o f ho s e s at lo c ation s s uch
a s uti l ity or lo ad i ng s tation s do e s no t re s u lt i n the pip ework b ei ng pu l le d i n a ma nner that c an
overstress the material.
Pipe supports can be categorized into those that permit movement and those that anchor the pipe.
4
© ISO 2017 – All rights reserved
ISO 14692-3:2017(E)
4.3.2
Pipe-support contact surface
T he fol lowi ng re qu i rements and re com mendation s apply to GRP pipi ng s upp or t.
I n a l l c as e s s upp or ts s ha l l h ave s u ffic ient leng th to s upp or t the pipi ng without c au s i ng damage a nd
a)
shall be lined with an elastomer or other suitable soft material.
b)
Poi nt lo ad s
s ha l l
be
avoide d .
This
can
be
accompl i s he d
b y u s i ng s upp or ts
with
at le as t 6 0 °
of
contact.
c) Clamping forces, where applied, shall be such that crushing of the pipe does not occur. Local
c ru s h i ng c an re s u lt from a p o or fit a nd a l l-rou nd cr u sh i ng c a n re s u lt from over-tighten i ng.
d)
Supp or ts s hou ld b e pre ferably lo c ate d on plai n-pip e s e c tion s rather than at fitti ngs or j oi nts . O ne
e xcep tion to th i s i s the u s e o f a " du m my leg" s upp or t d i re c tly on a n elb ow or te e (or pie ce o f pip e) .
C on s ideration sh a l l b e gi ven to the s upp or t cond ition s o f fi re -pro te c te d GRP pipi ng. Supp or ts place d on
the outs ide o f fi re pro te c tion c an res u lt i n lo ad s i rregu larly tra n s m itte d th rough the co ati ng , wh ich c an
re s u lt i n she a r/cr u sh i ng damage a nd con s e quent lo s s o f s upp or t i ntegrity. Supp or ts i n d i re c t contac t
with intumescent coatings can also alter the performance of the coating (i.e. prevent expansion of the
f
f
order to protect the pipe at the hanger or pipe support.
co ati ng u nder fi re) . T h i s may re qu i re appl ic ation o
i ntu me s cent co ati ngs to the pip e s upp or t its el
in
P ip e re s ti ng i n fi xe d s upp or ts th at p erm it pip e movement s ha l l have abra s ion pro te c tion i n the form o f
saddles, elastomeric materials or sheet metal.
Anchor supports shall be capable of transferring the required axial loads to the pipe without causing
overstress of the GRP pipe material. Anchor clamps are recommended to be placed between either a
f
f
to the outer surface of the pipe. The manufacturer’s standard saddles are recommended and shall be
bonded using standard procedures.
th ru s t col lar la m i nate d to the outer s u r ace o
the pip e or two double 1 8 0 ° s add le s , ad he s ive -b onde d
4.4 Isolation and access for cleaning
T he
de s igner
exa mple,
s hou ld
ma ke
provi s ion
for i s olation
a nd
eas y
acce s s
for mai ntenance
pu rp o s e s ,
for
for remova l o f s c a le a nd blo ckage s i n d rai n s . T he j oi nt to b e u s e d for i s ol ation or acce s s s hou ld
b e s hown at the de s ign s tage and s hou ld b e lo c ate d i n a p o s ition where the fl ange s c an i n prac tice b e
j acke d ap a r t, e . g. it s hou ld no t b e i n a s hor t ru n o f pip e b e twe en two anchors .
4.5 Vulnerability
4.5.1
Point loads
Poi nt lo ad s sha l l b e m i n i m i z e d and the GRP pipi ng lo c a l ly rei n force d where ne ce s s a r y.
4.5.2
Abuse
The designer shall give consideration to the risk of abuse to GRP piping during installation and service
and the need for permanent impact shielding.
Sources of possible abuse include the following:
a)
a ny are a where the pipi ng c a n b e s tepp e d on or u s e d for p ers on nel s upp or t;
b)
i mp ac t from d ropp e d obj e c ts;
c)
d)
a ny are a where pipi ng c a n b e da m age d b y adj acent c rane ac ti vity, e . g. b o om s , lo ad s , c ab le s , ro p e s
or chains;
weld s pl atter from ne arb y or overhe ad weld i ng ac tivitie s .
© ISO 2017 – All rights reserved
5
ISO 14692-3:2017(E)
Small pipe branches (e.g. instrument and venting lines), which are susceptible to shear damage, should
b e de s igne d with rei n forci ng gu s s e ts to re duce vu l nerabi l ity. I mp ac t s h ield i ng , i f re qu i re d, s hou ld b e
de s igne d to pro te c t the pipi ng to ge ther with any fi re -pro te c tive co ati ng.
4.5.3
Dynamic excitation and interaction with adjacent equipment and piping
T he de s igner s ha l l give con s ideration
pipi ng to
b e come
overs tre s s e d .
to the relative movement o f fitti ngs , wh ich c an c au s e the GRP
Where
re qu i re d,
con s ideration
sh a l l
b e gi ven
to
the u s e
o f fle xible
fitti ngs .
T he de s igner s hou ld en s u re that vibration due to the d i fferent dyna m ic re s p on s e o f GRP (as comp a re d
with c a rb on s te el pipi ng s ys tem s) do e s no t cau s e we ar at s upp or ts or overs tre s s i n bra nch l i ne s . T he
de s igner
be
shou ld
c au s e d
en s u re
b y tran s ient
that the GRP pipi ng i s ade quately
pre s s u re
pu l s e s ,
Reference [8] provides further guidance.
4.5.4
e . g.
op eration
s upp or te d
o f pre s s u re
to re s i s t s ho ck lo ad s
s a fe ty va lve s ,
va lve
th at c an
clo s ure
e tc .
Exposure to light and ultraviolet radiation
Where GRP piping is exposed to the sun, the designer shall consider whether additional ultra violet
radiation (UV) protection is required to prevent surface degradation of the resin. If the GRP is a
translucent material, the designer should consider the need to paint the outside to prevent possible
algae growth in slow-moving water within the pipe.
4.5.5
Low temperatures and requirements for insulation
The designer shall consider the effects of low temperatures on the properties of the pipe material, for
example, the e ffe c t o f fre e z e/thaw. For l iquid s er vice, the de s igner s hou ld p ar tic u la r p ay attention to
the
fre e z i ng p oi nt o f the i nterna l l iquid . For comple tely fi l le d l i ne s , s ol id i fic ation o f the i nterna l fluid
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can cause an expansion
of theFREE
liquidstandards
volume, which
can cause Sharing
the GRP Group
piping to
crack
or fail. For water
f
f
GRP piping to fail.
s er vice, the volume tric e xp an s ion du ri ng s ol id i fic ation or
re e z i ng i s more th an s u fic ient to c au s e the
T he pip e may ne e d to b e i n s u late d a nd/or fitte d with ele c tric a l s u r face he ati ng to prevent
fre e z i ng i n
cold we ather or to mai nta i n the flow o f vi s cou s flu id s . T he de s igner sha l l give con s ideration to:
a) additional loading due to mass and increased cross-sectional area of the insulation;
b) ensuring that electrical surface heating does not raise the pipe temperature above its rated
temperature.
H e at traci ng s hou ld b e s pi ra l ly wou nd onto GRP pipi ng i n order to d i s tribute the he at even ly rou nd the
pip e wa l l . H e at d i s tribution c an b e i mprove d i f a lu m i n iu m
4.6
foi l i s fi rs t wrapp e d a rou nd the pip e .
Fire and blast
T he e ffe c t o f a fi re event (i nclud i ng bla s t) on the layout re qu i rements sh a l l b e con s idere d . T he p o s s ible
events to b e con s idere d i n the layout de s ign o f a GRP pipi ng s ys tem i ntende d to fu nc tion i n a fi re i nclude
the following:
a)
bla s t overpre s s u re, d rag force s and proj e c ti le i mp ac ts;
b)
fi re pro te c tion o f j oi nts and s upp or ts;
c)
i nter face with me ta l fi x ture s;
d) formation of steam traps in piping containing stagnant water, which would reduce the conduction
o f he at away b y water;
e)
6
j e t fi re;
© ISO 2017 – All rights reserved
ISO 14692-3:2017(E)
f)
g)
he at rele a s e and s pre ad o f fi re for pipi ng i n man ne d s p ace s , e s c ap e route s or are as where p ers on nel
are at risk;
s moke em i s s ion, vi s ibi l ity and toxicity
personnel are at risk.
Pene tration s
(wa l l,
re qu i rements
are to prevent p a s s age
bu l khe ad ,
de ck)
sha l l
for pipi ng i n ma n ne d s p ace s , e s c ap e route s or are as where
no t
o f s moke
we a ken
the
a nd flame s ,
d ivi s ion
to
that
mai ntai n
they
p ene trate .
s truc tu ra l
T he
ma i n
i nte grity and to
l i m it the temp eratu re ri s e on the une xp o s e d s ide . Pene tration s sh a l l there fore comply with the s a me
re qu i rements
that apply to the releva nt ha z ardou s
b e en fi re -te s te d and approve d
5
T h i s re qu i re s
the p ene tration
to have
Hydraulic design
5.1
T he
d ivi s ion s .
for u s e with the s p e ci fic typ e o f GRP pipi ng u nder con s ideration .
General
ai m
s p e ci fie d
o f hyd rau l ic
de s ign
flu id
s p e ci fie d
at
the
is
to
en s u re
rate,
that GRP
pre s s u re
a nd
pipi ng s ys tem s
temp eratu re
are
c ap able
th roughout
o f tran s p or ti ng
thei r
i ntende d
the
s er vice
life. The selection of nominal pipe diameter depends on the internal diameter required to attain the
ne ce s s ar y flu id flow con s i s tent with the flu id and hyd rau l ic cha rac teri s tic s o f the s ys tem .
5.2
Flow characteristics
F lu id
velo c ity,
den s ity
o f flu id ,
i n s ide d i a me ter o f pip e s ,
i nter io r
s u r face
a s wel l a s re s i s tance
ro ugh ne s s
o f pip e s
a nd
fitti ngs ,
leng th
o f pip e s ,
from va lve s a nd fitti ngs s h a l l b e ta ken i nto acco u nt
when estimating pressure losses. The smooth surface of the GRP can result in lower pressure losses
pressure losses.
comp a re d to me ta l pip e . C onvers ely, the pre s ence o f e xce s s ive pro tr ud i ng ad he s i ve b e ad s wi l l i nc re a s e
5.3
General velocity limitations
When s ele c ti ng the flow velo c ity
for the GRP pipi ng s ys tem, the de s igner sh a l l ta ke i nto accou nt the
fol lowi ng concern s that c an l i m it velo citie s i n pipi ng s ys tem s:
a) unacceptable pressure losses;
b) prevention of cavitation at pumps and valves;
c) prevention of transient overloads (water hammer);
d) reduction of erosion;
e) reduction of noise;
f) reduction of wear in components such as valves;
g)
pip e d ia me ter and ge ome tr y (i ner tia lo ad i ng) .
For typic a l GRP i n s ta l lation s , the me an l i ne a r velo c ity for conti nuou s s er vice o f l iquid s i s b e twe en 1 m/s
and 5 m/s with i nterm ittent e xc u rs ion s up to 10 m/s . For ga s , the me an l i ne ar velo city
for conti nuou s
service is between 1 m/s and 10 m/s with intermittent excursions up to 20 m/s. Higher velocities are
ff
into the atmosphere.
accep table i
ac tors th at l i m it velo citie s a re el i m i nate d or control le d , e . g. vent s ys tem s that d i s charge
© ISO 2017 – All rights reserved
7
ISO 14692-3:2017(E)
5.4 Erosion
5.4.1
General
The following factors influence the susceptibility o f GRP piping to erosion damage:
a) fluid velocity;
b) piping configuration;
c) particle size, density and shape;
d) particulate/fluid ratio;
e) onset of cavitation.
The designer shall re fer to the manu facturer and consider reducing the velocity i f doubts exist on
erosion performance.
5.4.2
Particulate content
The erosion properties of GRP are sensitive to the particulate content. The designer shall take into
account the likely particulate content in the fluid and reduce the maximum mean velocity accordingly.
For GRP, the maximum erosion damage typically occurs at a hard-particle impingement angle o f
between 45° and 90°, i.e. at bends and tees. At low impingement angles (<15°), i.e. at relatively straight
sections, erosion damage is minimal. Further information on erosion can be found in DNV RP 0501.
5.4.3
Piping configuration
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The presence o f turbulence
generators
can have
significant
influence
on and
the our
erosion
piping, depending on fluid velocity and particulate content. The designer shall consider the degree o f
turbulence and risk o f possible erosion when deciding the piping configuration. To minimize potential
erosion damage in GRP piping systems, the following shall be avoided:
a) sudden changes in flow direction;
b) local flow restrictions or initiators o f flow turbulence, e.g. excessive adhesive (adhesive beads) on
the inside of adhesive-bonded connections.
5.4.4
Cavitation
GRP piping is susceptible to rapid damage by cavitation. Cavitation conditions are created in piping
systems more easily than is generally realized, and the general tendency for systems to be designed
for high velocities exacerbates the situation further. Potential locations of cavitation include angles at
segmented elbows, tees and reducers, flanges where the gasket has been installed eccentrically and
joints where excessive adhesive has been applied.
The designer shall use standard methods to predict the onset o f cavitation at likely sites, such as
control valves, and apply the necessary techniques to ensure that cavitation cannot occur under normal
operating conditions.
5.5 Water hammer
The susceptibility o f GRP piping to pressure transients and out-o f-balance forces caused by water
hammer depends on the magnitude o f pressure and frequency o f occurrence. A full hydraulic transient
analysis shall be carried out, i f pressure transients are expected to occur, to establish whether the GRP
piping is susceptible to water hammer. The analysis shall cover all anticipated operating conditions
including priming, actuated valves, pump testing, wash-down hoses, etc.
8
© ISO 2017 – All rights reserved
ISO 14692-3:2017(E)
I f there is a significant risk o f water hammer, the designer shall employ standard techniques to ensure
that pressure transients do not exceed the hydrotest pressure.
A typical cause o f water hammer is the fast closing o f valves. The longer the pipeline or piping section
and the higher the liquid velocity, the greater the shock load will be. Shock loading generally induces
oscillation in the piping system. Since GRP pipe has a lower axial modulus o f elasticity than the
equivalent steel pipe, longitudinal oscillations are generally more significant.
A hydraulic transient analysis can identi fy the potential requirement for vacuum breakers to prevent
vacuum conditions and vapour cavity formation. The proper selection and sizing o f vacuum breakers
(also known as air-vacuum valves) can prevent water-column separation and reduce water hammer
effects. The sizing and the location of the vacuum breakers are critical. The air shall be admitted
quickly to be e ffective and shall be sized to account for the substantial pressure that can occur due
to the compression of the air during resurge. Air removal is often accomplished with a combined
air-release/air-vacuum valve.
6 Generation of design envelopes
6.1 Partial factors
6.1.1
Design life
0 shall be used to scale the long term envelopes to the design envelopes at design lives other than
20 years. A 0 shall be defined by Formula (1):
A
A0 =
where
G
6.1.2
10
(1)
is the time expressed in h;
t
A
1
t − log ( 175 200 ) ) × G xx
( log ( )
xx is the gradient o f regression line at xx °C;
0 shall not be greater than 1,0.
Chemical degradation
2 shall be used to scale the long term envelopes to the design envelopes to account for the effect of
chemical degradation. See ISO 14692-2:2017, 4.5.2.
A
6.1.3
Fatigue and cyclic loading
3 shall be used to scale the long term envelopes to the design envelopes and shall be calculated taking
into account Figure 2 and Annex A.
A
© ISO 2017 – All rights reserved
9
ISO 14692-3:2017(E)
Key
1
2
Rc
fc
fully s tatic lo ading
fully cyclic lo ading
cyclic lo ading ratio , =
σmin / σmax
cyclic lo ng term s trength facto r (de fault value o f 4, 0 ) , =
σ100 000 (static) / σ
1 5 0 0 0 0 0 0 0 (cyclic)
FigureGet
2—
A 3 as
a function
of the
number
of cycles
andGroup
the loading
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6.2 Part factor, f2
The part factor for sustained loading, f2 , to be used in the assessment of sustained loads, shall be
de term i ne d ta ki ng i nto account op erati ng cond ition s and ri s k as s o c iate d with the pipi ng s ys tem . T he
va lue to b e appl ie d
for s p e ci fic pipi ng s ys tem s s ha l l b e s p e ci fie d b y the u s er. Re com mende d typic a l
values for f2 are
a) 0,67 for sustained loading conditions,
b) 0,83 for sustained loading plus self-limiting displacement conditions, and
c) 0,89 for occasional loading conditions.
Table 1
f
provide s
e xa mple s
o
lo ad s
e xp erience d
by a
GRP
pipi ng
s ys tem .
T he
de s igner
sha l l
h ave
d i s cre tion i n defi n i ng the lo ad ca s e s .
10
© ISO 2017 – All rights reserved
ISO 14692-3:2017(E)
Table 1 — Examples of loads experienced by a GRP piping system
Sustained, f2 = 0 , 67
Sustained + self-limiting
displacements, f2 = 0 , 8 3
Occasional, f2 = 0 , 8 9
H yd ro te s t a nd o ther o cc a s ion a l
Operating and sustained internal,
external or vacuum pressures, MOP
(maximum operating pressure), Pdes
pressures
Water hammer or other pressure
transients
Thermal induced loads, electric
surface heating or other heat
tracing methods
P re s s u re s a fe ty va l ve rele a s e s
Piping self-mass, piping insulation
-
Installed curve radius (roping)
m a s s , fi re pro te c tion m a s s , tra n s
Impact
O cc a s ion a l veh ic u l a r tra ffic lo ad s on
buried pipes
Occasional inertia loads (e.g. motion
during transportation, storms, etc.)
wave action, ship movement, inundation through high tides, other
horizontal and
Ring bending due to long term verti- Earthquake-induced
motions during operation)
vertical forces
Displacement of supports due to opDisplacement of supports due to ocof the hull during operations)
during lifting)
Environmental loads, ice
Soil loads (burial depth)
Adiabatic cooling loads
f
Wind
(from occasional conditions
Soil subsidence
pipes
such as a storm)
Encapsulation in concrete
Blast over-pressures
Thermal induced loads due to upset
conditions
p or te d me d iu m m a s s , buo ya nc y,
o ther s ys tem lo ad s
Su s ta i ne d i ner ti a lo ad s (e . g. d a i l y
cal pip e deflec tion i n a buried s ys tem
eratio n a l co nd ition s (s uch a s fle xi ng
c a s io n a l cond i tio n s (s uch a s fle xi ng
Veh ic u l a r tra fic lo ad s on bu r ie d
NO TE
1
S o me c a s e s , s uch a s ice a nd s no w, m ay b e co n s ide re d
ei the r s u s ta i ne d
o r o cc a s io n a l ,
de p e nd i ng o n the lo c a l
environment.
NOTE 2 The sustained + self-limiting displacements column is meant to cover those load cases where both sustained loads
a nd s e l f- l i m i ti n g d i s p l ace ments o cc u r s i mu l ta ne o u s l y.
NO TE 4
S o i l s ub s ide nce m ay b e co n s ide re d a s u s ta i ne d + s el f- l i m i ti n g d i s p l ace ments lo ad .
NO TE 4
I n b u r ie d s ys tem s , the hyd ro te s t lo ad c a s e m ay ne e d to b e e va lu ate d i n the o p e n tre nch (i . e . no t b u r ie d) co nd i tio n .
NO TE 5
I n b u r ie d s ys tem s , s tab le s o i l s a re re qu i re d fo r lo ad s to b e s e l f- l i m iti n g.
6.3 Combinations of part factor and partial factors
The designer shall determine the applicable combination(s) of loading cases.
A 0 , A 2 and A 3 shall be 1,0 and f2 shall be 0,89.
For the field hyd ro te s t lo ad i ng c as e,
6.4 Design envelope
Construct each design envelope based on the following formulae. The design envelope shall be based on
Formulae (2) through (7)
Figure 3:
σ h,des,2: 1 = f2 × A 0 × A 2 × A3 × σ h,LT,2:1,xx
(2)
and a s graph ica l ly pre s ente d i n
σ a,des,2: 1 = f2 × A 0 × A 2 × A3 × σ a,LT,2:1,xx
(3)
σ h,des, Rtest = f2 × A 0 × A 2 × A3 × σ h,LT, Rtest,xx
(4)
σ a,des, Rtest = f2 × A 0 × A 2 × A3 × σ a,LT, Rtest,xx
(5)
© ISO 2017 – All rights reserved
11
ISO 1 469 2 -3 : 2 01 7(E)
σ a,des,0: 1 = f2 × A 0 × A 2 × A3 × σ a,LT,0:1,xx
(6)
σ a,des,0:-1 = 1, 25 × f2 × A 0 × A 2 × A3 × σ a,des,0:1
(7)
where
is the part factor for loading;
is the partial factor for design life;
is the partial factor for chemical resistance;
f2
A0
A2
A3
i s the p ar tia l fac tor for c ycl ic s er vice;
σa,LT,2:1,xx
i s the long term envelop e a xi a l s tre s s for a n u nre s trai ne d, hyd rau l ic (2 : 1) cond ition at
x x ° C , expre s s e d i n M Pa;
σh,LT,2:1,xx
i s the long term envelop e ho op s tre s s for an u n re s trai ne d, hyd rau l ic (2 : 1) cond ition at
x x ° C , expre s s e d i n M Pa;
σa,LT,0:1,xx
NO TE
-
i s the long term envelop e a xi a l s tre s s for a pure a xi a l lo ad i ng cond ition at x x ° C , ex
pressed in MPa.
T he de s i gn pro ce du re i n th i s do c u ment i s b a s e d o n the prem i s e th at the fi tti n gs a nd j oi nts a re at le a s t
a s s tron g a s the p l a i n pip e u nder a ny lo ad i ng cond i tion . T he a n gle o f rei n forcement i n the con s tr uc tion me tho d
o f s ome fi tti ngs a nd j oi nts , howe ver, c a n va r y gre atl y fro m the typ ic a l 5 5 ° wi nd i ng a ngle o f fi l a ment wo u nd pip e .
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T hu s , the the o re tic a l s h ap e o f a lo ng ter m envelop e o f a fitti n g or j oi nt wi th e qu a l a mo u nts o f rei n forcement i n
the axial and hoop directions can be closer to a rectangular shape or can even approach that of a square. The use
of these construction methods which differ from the pipe can have an effect on the long term envelope(s), design
envelope(s) and f3 f
ac tor. I n s ome c a s e s , the fitti ng or j o i nt c a n b e s i gn i fic a ntl y s tro nger th a n the fi l a ment wou nd
pl a i n p ip e i n the a xi a l d i re c tion , but we a ker i n the ho o p d i re c tio n . I n o thers , the op p o s i te c a n b e tr ue . To s ati s fy
the prem i s e th at the fi tti ngs a nd j oi nts a re at le a s t a s s tro ng a s p l a i n pip e m ay re qu i re add ition a l rei n forcement,
additional wall thickness or other means of improving the strength.
12
© ISO 2017 – All rights reserved
ISO 14692-3:2017(E)
Key
1 long term envelope
2 design envelope
Figure 3 — Relationship between the long term envelope(s) and design envelope(s)
7
7.1
Stress analysis
Analysis methods
E ither
manua l
or
computer
me tho d s
sha l l
be
used
for
the
s truc tura l
a na lys i s
o f pipi ng
s ys tem s .
H owever, the de gre e o f a na lys i s dep end s on the fol lowi ng fac tors:
a)
pip ework fle xibi l ity;
b)
l ayout comple xity;
c) pipe supports;
d) pipework diameter;
e) magnitude of temperature changes;
f)
s ys tem c ritica l ity a nd fai lu re ri s k a s s e s s ment.
© ISO 2017 – All rights reserved
13
ISO 14692-3:2017(E)
7.2 Pipe stress analysis software
All current pipe stress analysis so ftware for pipelines and piping starts with an isometric “stick
drawing”. The hoop stress and axial stress from pressure are calculated separately, outside the analysis.
The analysis utilizes a “beam element” in order to calculate axial bending stresses from externally
applied moments and axial stress from externally applied axial forces. Global forces and moments are
translated to local axial forces and bending moments. Out of plane shear that is perpendicular to the
pipe wall is ignored since the stress values are low.
In an analysis o f the piping system, the calculated stresses are all based on the pipe wall properties
using a beam element that models the properties o f the pipe wall throughout the isometric “stick
diagram”. Calculated pipe response (stress and deflection) is then modified by the use o f de fault axial
SIFs and axial flexibility factors for each component in order to mimic or predict the per formance o f the
component (fitting or joint) versus the calculated values in the analysis based on the pipe wall response.
The default axial SIFs account for unknown performance of the components for applied loads between
R = 0 and R = 2,0. True or measured axial SIFs can be determined in 1 000 h qualification testing at
Rtest for each component at the discretion o f the supplier. Hoop pressure modifiers are not needed for
components, since all components have been qualified at R = 2.
This document compares calculated stresses in the hoop and axial directions to a “trapezoidal design
envelope”. This envelope defines the allowable combinations o f axial and hoop stress. Other standards
might report Von Mises stress or maximum shear stress such as those determined by Mohr’s circle.
These reported or calculated stresses have no correlation for an anisotropic material like a composite
and only apply to an isotropic material like steel. As such design standards that report these stresses
(e.g. BS 7159) should not be selected as the design code.
7.3 Analysis requirements
The designer shall Get
evaluate
totalstandards
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criticality
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riskchats
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operating/material factors, in order to assess the need for flexibility/stress analysis. Anchor (support)
loading shall be checked for acceptability.
NOTE 1
At large diameters, the design o f the piping system can be determined more by the support conditions
NOTE 2
The dimensions o f GRP piping are usually re ferenced in terms o f the inner diameter and wall thickness
than the internal pressure conditions.
because of the nature of the manufacturing process.
7.4 Flexibility factors
Flexibility factors for GRP bends and tees shall be determined in accordance with Annex B.
7
.
5
S
t
r
e
s
s
i
n
t
e
n
s
i
f
i
c
a
t
i
o
n
f
a
c
t
o
r
s
Axial stress intensification factors (both in-plane and out-o f-plane) for GRP bends and tees shall be
— 1,5, or
— qualified in accordance with B.5.
Since all components are subject to the qualification programme in ISO 14692-2, which includes the
generation of hoop stresses from an R = 2 test, hoop SIFs are not required for any components.
There are no SIFs for flanges nor reducers nor pipe joints.
Since all components are subject to the qualification programme in ISO 14692-2, pressure stress
multipliers are not required.
Additional in formation on stress intensification factors is given in Annex B.
14
© ISO 2017 – All rights reserved
ISO 1 4692 -3 : 2 01 7(E)
7
.
6
M
o
d
e
l
l
i
n
g
f
i
t
t
i
n
g
s
For fittings that have an MPR equal to the plain pipe, the fitting shall be modelled in the stress analysis
with the dimensional properties (ID, tr,min) o f the pipe, not the fitting.
For fittings that have an MPR di fferent than the plain pipe, the fitting shall be modelled in the stress
analysis with the dimensional properties (ID, tr,min) o f the equivalent-rated pipe, not the fitting.
EXAMPLE
A 200NB piping system is constructed with 10 bar rated plain pipe and 20 bar rated fittings.
The minimum reinforced wall thickness of the 10 bar components is 3,0 mm for the plain pipe and 5,0 mm for
the bends. The minimum reinforced wall thickness of the 20 bar components is 6,0 mm for the plain pipe and
10,0 mm for the bends. The fitting should be modelled in the stress analysis with a 6,00 mm wall thickness,
which is the wall thickness for the equivalent-rated (20 bar) pipe.
Some so ftware programs for stress analysis model tees and other branches as a single node (the
intersection). This does not allow for modelling the tee different than the plain pipe. If the tee has an
MPR di fferent than the plain pipe and the designer wishes to properly model the tee, it will require the
designer to model 3 nodes for the tee. For simplicity, it may be acceptable to use a de fault laying length
of 1,0 × D for each leg of the tee, where D is the nominal pipe size. The same practice would be required
or saddles (also called olets), except that only one additional node would be required.
f
7
7
.
.
7
7
.
A
1
l
l
o
V
e
w
a
r
t
i
b
c
l
a
e
l
d
d
e
e
f
l
f
l
e
e
c
c
t
i
t
i
o
o
n
n
i
s
n
a
b
o
v
e
g
r
o
u
n
d
p
i
p
i
n
g
s
y
s
t
e
m
s
For aboveground piping systems, vertical deflections shall not exceed 12,5 mm or 0,5 % o f span
length or support spacing, whichever is smaller. I f the manu facturer's minimum spacings for support
are not exceeded, then deflections shall be within these allowable limits. It shall be agreed between
the principal and the manufacturer that the quoted minimum spacings for support do not result in
deflections greater than prescribed.
7
.
7
.
2
V
e
r
t
i
c
a
l
d
e
f
l
e
c
t
i
o
n
i
n
b
u
r
i
e
d
p
i
p
i
n
g
s
y
s
t
e
m
s
The predicted vertical pipe deflection, Δy, as a fraction of D r,min , shall be less than 5 %:
Dy ≤ 5 %
(8)
D r,min
The predicted vertical pipe deflection, as a fraction o f D r,min, shall be calculated according to
Formula (9):
∆y
D r,min
where
=
(D
L ×
Wc + WL ) × K x
149 × PS + 61 000 × M s
(9)
L is the deflection lag factor, see AWWA Manual M45 (second edition), 5.7.3.3; D L shall be 1,0 for
the hydrotest loading case;
Wc is the vertical soil load on the pipe, expressed in N/m 2 , AWWA Manual M45 (second edition),
D
5.7.3.5;
WL is the live load on the pipe, expressed in N/m 2 , see AWWA Manual M45 (second edition),
5.7.3.6; the designer shall have the option of setting WL = 0 for the hydrotest loading case i f
live loads are not present;
© ISO 2017 – All rights reserved
15
ISO 14692-3:2017(E)
x is the dedding coe fficient, see AWWA Manual M45 (second edition), 5.7.3.4;
K
PS
is the pipe sti ffness, expressed in kPa, determined by conducting parallel-plate loading tests
in accordance with ASTM D2412 with a vertical diameter reduction o f 5 %;
s is the composite soil constrained modulus, expressed in MPa, see AWWA Manual M45 (second
M
edition), 5.7.3.8.
NOTE 1 Formula (9) is similar to AWWA Manual M45 (second edition), Formula (5) to Formula (8) with D r,min
substituted for D.
NOTE 2 There is no check o f predicted vertical pipe deflection against any allowable vertical pipe deflection
other than the 5 % limit. This is because a combined stress will be checked using Formula (10) to Formula (12).
NOTE 3 The deflection lag factor is intended to convert the short-term deflection o f the pipe to the long-term
deflection a fter several years. This increase in deflection is due to an increase in the overburden load due to
the loss o f soil arching [see AWWA Manual M45 (second Edition), 5.7.3.3]. While a majority o f this increase in
deflection is theorized to occur in a matter months (and even weeks), it is most likely not appropriate to include a
deflection lag factor for the hydrotest case. The designer has the option to set D L to 1,0 for the hydrotest loading
case i f the pipework have not been backfilled.
7.8
Allowable stresses
The sum o f the hoop stresses shall be defined by the following formulae:
(10)
σ h,sum = σ hp + σ hu
σ hp =
P×D
r,min
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2 × t r,min
σ hu = rc × D f × E hb ×
where
∆y
D
r,min
×
t
(12)
r,min
D
(11)
r,min
is the internal pressure, expressed in MPa;
tr,min
is the minimum reinforced pipe wall thickness, expressed in mm;
D r,min
is the mean diameter of the minimum reinforced pipe wall, expressed in mm;
tl
is the internal liner thickness of the pipe wall, expressed in mm;
rc
is the rerounding coe fficient, for P ≤ 3 then rc = 1 – P / 3, for P > 3 then rc = 0;
Df
is the shape factor, see AWWA Manual M45 (second edition), Table 1;
Δy/D r,min is the predicted vertical pipe deflection [see Formula (9)];
Ehb
is the hoop bending modulus, expressed in MPa.
P
NOTE 1 Because of the combined effects of internal pressure and burial conditions, it is possible that the sum
of the hoop stresses can be outside the design envelope even though the designer is using the product within the
design limits o f the product. In this case, the designer may need to select a product with a higher MPR, de-rate the
product, lower the design conditions, reduce the stresses due to earth load, and/or go back to the manufacturer
for more data points on the design envelope.
16
© ISO 2017 – All rights reserved
ISO 1 4692 -3 : 2 01 7(E)
NOTE 2
The σhu term is calculated by deflection and Ehb . It is not based on long term testing according to
ASTM D5365 or ASTM D3681. Those particular tests are loaded in the hoop direction only and the mode o f
failure can be glass rupture. However, piping that is only loaded in the hoop direction is outside the scope o f
this document (e.g. joining method has to be a restrained joint). The strain or stress obtained from ASTM D5365
and ASTM D3681 will be much higher than that predicted by ASTM D2992 simply because the samples are only
loaded in the hoop direction. Data from ASTM D5365 and ASTM D3681 are not needed and are excluded from
consideration.
NOTE 3 The σhu term can be positive or negative (tensile or compressive), but it is only necessary to consider
the tensile component in the stress calculations.
NOTE 4 The rerounding coe fficient, which is theorized to be primarily a function o f internal pressure, accounts
for the reduction in ring bending stress as internal pressure increases. When the piping is initially installed, it
deflects due to the weight o f the soil. This is the initial bending strain. When they are pressurized, the piping
“re-rounds” and some o f that strain is removed. The formula in the AWWA Manual M45 is meant to approximate
the ratio of the bending strain at a given pressure to the initial bending strain. Rc may be an important concept
for the hydrotest loading case for large diameter, lower pressure rated piping, but may not be needed for high
pressure, thick-wall piping.
NOTE 5 Deflection is a very important parameter for buried piping design that needs controlling. The soil
loads, live loads, soil properties (most importantly sti ffness) and the pipe sti ffness all have a direct e ffect on the
calculated (or predicted) vertical pipe deflection. The AWWA Manual M45 makes the conclusion that the theories
used to predict the vertical pipe deflection can provide results that vary from the actual deflections in the field.
It also states in AWWA Manual M45 Second Edition, 5.7.3.2 “Experience has shown that deflection levels… can be
higher or lower than predicted by calculation i f the design assumptions are not achieved.” There fore, the AWWA
Manual M45 recommends that the permitted vertical pipe deflection (which is typically set at 5 %, as a fraction
o f the mean pipe diameter) is to be used in the calculations. This document specifies that Δ y be used in lieu of δd
when calculating the hoop (ring) bending stress due to earth loads.
NOTE 6 Df is a factor to account for the deviation of the shape of the pipe compared to the idealized ellipse in a
deflected condition. This factor was determined experimentally by measuring the local shape changes in buried
pipe of various pipe stiffnesses in various soil conditions. D f is not a derived number.
The sum o f the axial stresses shall be defined by the following formulae:
σ a,sum = σ ap ± σ ab + σ af ± σ ac + σ at
σ ap =
P × D r,min
(13)
(14)
4 × t r,min
for a closed, unrestrained pipe
σ ap = υ ah ×
P × D r,min
(15)
2 × t r,min
or an axially restrained pipe
f
σ ab = 1 000 ×
Zr =
π
32
σ af =
×
Fa
Ar
(
(
SIFai × M i ) 2 + ( SIFao × M o ) 2
Zr
4
OD r,min
− ID r4 )
OD r,min
=
Fa
π
4
2
× ( OD r,min
− ID r2 )
© ISO 2017 – All rights reserved
(16)
(17)
(18)
17
ISO 1 469 2 -3 : 2 01 7(E)
OD r,min
× Ea
2 × C × 1 000
(19)
σ at = α a × (Tinstall − Tdesign ) × E a
(20)
σ ac =
where
is the internal pressure, expressed in MPa;
ID r
is the inside diameter of the reinforced pipe wall, expressed in mm;
OD r,min is the minimum outside diameter of the reinforced pipe wall, expressed in mm;
σap
is the axial stress from internal pressure, calculated using either Formula (14) or Formula (15), expressed in MPa;
P
νah
i s the m i nor Poi s s on's ratio , ho op s trai n re s u lti ng from a s tre s s i n the a xi a l d i re c tion;
ai
i s the a xi a l i n-pl ane s tre s s i nten s i fic ation
ao
i s the a xi a l out- o f-pl ane s tre s s i nten s i fic ation
SIF
SIF
fac tor;
is the in-plane bending moment, expressed in Nm;
is the out-of-plane bending moment, expressed in Nm;
is the minimum reinforced pipe wall section modulus, expressed in mm 3 ;
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is theGet
localised
expressed
N;
is the minimum reinforced pipe wall cross section, expressed in mm 2 ;
is the curve radius, expressed in m;
is the axial tensile modulus, expressed in MPa;
i
M
o
M
r
Z
a
F
r
A
fac tor;
C
a
E
αa
i s the co e ffic ient o f therma l e xp an s ion i n the a xi a l d i re c tion, e xpre s s e d i n m m/m m/° C ;
install
i s the i n s ta l lation temp eratu re, e xpre s s e d i n ° C ;
design
i s the de s ign temp eratu re, e xpre s s e d i n ° C .
T
T
NOTE 7 σat
an expansion loop or direction change), thermal growth can create reaction forces and moments which need to
on l y o cc u rs i n p ip i ng s ys tem s where a xi a l grow th i s re s tra i ne d . I n o ther con fi gu ratio n s (s uch a s i n
b e p rop erl y a na l ys e d .
NOTE 8
Temperature changes are assumed to produce no hoop stress component.
NO TE 9
P ipi ng s ub j e c t to i nter n a l p re s s u re wi l l b e tre ate d a s u n re s tra i ne d p ip e s , wh ich wi l l grow a xi a l l y wi th
i nc re a s i n g p re s s u re , p lu s a n a xi a l end lo ad , wh ich , for a fu l l y re s tra i ne d s ys tem , wi l l re tu r n the pip e to its o r i gi n a l
leng th (i . e . no leng th ch a nge for a fu l l y re s tra i ne d s ys tem) . T h i s me tho d wi l l p rovide a co n s i s tent app ro ach for the
a n a l ys i s o f u n re s tra i ne d , a ncho re d a nd bu r ie d p ip i ng s ys tem s . I n a s i m i l a r m a n ner, pip i n g s ub j e c t to temp eratu re
ch a nge s wi l l b e tre ate d a s u n re s tra i ne d p ip e s , wh ich wi l l grow a xi a l l y wi th i nc re a s i ng temp eratu re , p lu s a n a xi a l
end lo ad , wh ich , fo r a fu l l y re s tra i ne d s ys tem , wi l l re tu r n the p ip e to i ts or i gi n a l leng th . Temp eratu re ch a nge s a re
assumed to produce no hoop stress component.
18
© ISO 2017 – All rights reserved
ISO 14692-3:2017(E)
N O T E 10
Re s tra i ne d pip i ng i s a s s u me d to b e re s tra i ne d i n the a xi a l d i re c tion o n l y, there i s no re s tra i nt i n the
hoop direction. In long buried piping, the axial friction forces accumulate to prevent axial movement. But, in the
ho o p d i re c tion , the typic a l s o i l el a s tic mo du lu s i s much lower th a n the p ip e ho o p mo du lu s a nd i s i ne ffe c ti ve i n
re s tra i n i ng the p ip e . C o n s e quentl y, the c a lc u l ate d ho op s tre s s
re s tra i ne d pip e s i s the s a me . T he c a lc u l ate d a xi a l s tre s s
from i nter n a l pre s s u re for b o th u n re s tra i ne d a nd
from i nter n a l p re s s u re , howe ver, i nclude s the Poi s s on's
e ffe c t for re s tra i ne d p ip e s on l y. O ne e xcep tio n to th i s r u le m ay b e p ipi ng enc a s e d i n co nc re te where the i nter n a l
pressure is unable to generate a hoop stress. In this exception, the assumption regarding directional restraint
would produce a conservative design and should remain safe.
NOTE 11 σat can be considered a form of σaf, taking care that these stresses are twice not applied. σat is intended
to b e app l ie d to fu l l y-re s tra i ne d pipi n g s ys tem s (ei ther ab ove gro u nd o r bu rie d) .
The σab
term
wi l l
typic a l ly
i nclude
b o th
ten s i le
and compre s s ive
s tre s s e s
on opp o s ite
s ide s
o f the
pip e . T he s e s ide s may b e the top/ b o ttom or the le ft/right s ide s . C on s e quently, it s ha l l b e ne ce s s a r y to
prop erly s u m the s tre s s e s (ta ki ng no te o f whe ther e ach s tre s s i s p o s itive or ne gative) i n e ach pl ane a nd
determine a vector sum of the two totals according to Formula (21):
σ a,sum = σ ap +
NO TE 1 2
(
(21)
∑ σ ab,top/bottom 2 + ∑ σ ab,left/right 2 + σ af ± σ ac + σ at
)
(
)
Fo r ab o ve grou nd c ro s s co u ntr y p ip el i ne s , b o th
σac (roping curvature) and σab (free span bending) can
b e pre s ent i n b o th p l a ne s at s ome lo c ation s a nd thu s re qu i re the re s u lti ng s tre s s e s to b e de ter m i ne d b y pro p er
vector-summation.
NO TE 1 3
T he re ference to re s tra i ne d a nd u n re s tra i ne d i n the gu ida nce ab o ve i s no t re fer ri n g to the typ e o f j oi nt
(e . g. a l a m i n ate d or ad he s i vel y b onde d j oi nt i s a re s tra i ne d j oi nt) . Rather, i t i s re fer r i ng to the typ e o f i n s ta l l atio n
for the s ys tem .
The sum of the hoop stresses and the sum of the axial stresses shall be within the design envelope for
each loading case.
7.9
External pressure
Pla i n pip e and fitti ngs sh a l l h ave s u ffic ient s ti ffne s s to re s i s t vac uu m a nd/or ex terna l pre s s u re lo ad s .
T he m i ni mu m s ti ffne s s sh a l l b e s u ffic ient to re s i s t a shor t-term vac uu m (e . g. b y the op eration o f an
up s tre am va lve) with a s a fe ty fac tor
e of 1,5.
F
P ipi ng s u s cep tible to long-term vac uu m and/or e x terna l pre s s u re lo ad s s ha l l have a s ti ffne s s s u fficient
to re s i s t the i nduce d lo ad with a s a fe ty fac tor
The external collapse pressure, Pe
e of 3,0.
F
, i n M Pa, o f GRP pip e s s ha l l b e c a lc u late d
as s u me s that the leng th o f the pip e i s s ign i fic antly gre ater tha n the d ia me ter:
 t r,min 


P = 2×
×
E
×
e
hb 

F
D
e
 r,min 
1
by
Formula (22) which
3
(22)
where
e
F
i s the s a fe ty fac tor, e qua l to 3 , 0 ;
is the hoop bending modulus, expressed in MPa;
tr,min is the minimum reinforced pipe wall thickness, expressed in mm;
D r,min is the mean diameter of the minimum reinforced pipe wall, expressed in mm.
E
hb
© ISO 2017 – All rights reserved
19
ISO 14692-3:2017(E)
7.10 Axial compressive loading (buckling)
7.10.1 Shell buckling
The axial elastic buckling stress, σu,s
σ u,s = 0, 90 × β ×
E
, i n M Pa, for a c yl i nder i n pure b end i ng sh a l l b e ta ken as:
a × t r,min
D
where
(23)
r,min
is the axial tensile modulus, expressed in MPa;
tr,min
is the minimum reinforced pipe wall thickness, expressed in mm;
D r,min
is the mean diameter of the minimum reinforced pipe wall, expressed in mm.
The value β is obtained from Formula (24):
a
E
(24)
β = 0, 188 7 + 0, 811 3 × β 0
The value β0 is obtained from Formula (25):
0, 83
β0 =
0, 1 + 0, 005 × (
ID
t
(25)
r
)
r,min
Getelastic
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The ratio of the axial
stress to from
σab shall
be greater
thanGroup
or equal
3: chats
σ u,s
σ ab
NO TE
(26)
≥ 3, 0
S hel l b uckl i ng i s p r i m a r i l y a n i s s ue fo r th i n- wa l le d l a rge - d i a me ter p ip e .
7.10.2 Euler buckling
For a xia l
compre s s ive
s ys tem
lo ad s ,
e . g.
con s tra i ne d
therma l
e xp a n s ion
or ver tic a l
pip e
ru n s
with
end compressive loads, and a given length of unsupported pipe, L , the axial compressive load shall not
exceed Fa,max
Formula (27):
, i n N , defi ne d u s i ng
F
a,max =
where
π 2 × Ir
2
L
(27)
× E a × 10 6
is the minimum reinforced pipe wall moment of inertia, expressed in mm 4;
L
is the length of unsupported pipe, expressed in m;
Ea is the axial tensile modulus, expressed in MPa.
Ir
NO TE 1
B o th end s o f the p ip e a re a s s u me d to b e pi n ne d or fre e to ro tate . I f the end s o f the p ip e a re fi xe d or
anchored, the value of Fa,max
20
i nc re a s e s b y a fac to r o f 4.
© ISO 2017 – All rights reserved
ISO 14692-3:2017(E)
T he e qu iva lent Eu ler buckl i ng s tre s s , i n M Pa, i s given b y
σ u,e =
Formula (28):
Fa,max
(28)
Ar
where
is the maximum axial compressive load, expressed in N;
Ar
is the minimum reinforced pipe wall cross section, expressed in mm 2 .
The ratio of the equivalent Euler buckling stress to the maximum compressive stress shall be greater
than or equal to 3:
Fa,max
σ u,e
σ a,comp
(29)
≥ 3, 0
where
is the equivalent Euler buckling stress, expressed in MPa;
σa,comp is the maximum compressive stress on the unsupported length of piping, expressed in MPa.
σu,e
NOTE 2
σap , σaf and σat can have axial compressive stress components that are due to axial compressive
s ys tem lo ad s . O n l y co mp re s s i ve lo ad s a re co n s idere d when e va lu ati ng E u ler buckl i n g.
NO TE 3
T he de s i gner m ay a l s o ne e d to con s ider Eu ler buckl i n g
i s wh at i s c au s i n g the buckl i n g) . T he o re tic a l l y,
from i ntern a l p re s s u re (i . e . the water co lu m n
th i s b uckl i ng pre s s u re i s e qu a l to the p re s s u re th at provide s a
“vi r tu a l” a xi a l pre s s u re th r u s t lo ad e qu a l to the E u ler colu m n b uckl i ng lo ad . T h i s p henomenon c a n o cc u r i n s m a l l
b ore ab ove gro u nd p ipi n g s ys tem s .
7.10.3 Buckling pressure — Buried piping
The external radial stress, σu,b , in MPa, for buried pipe shall be calculated using either Formula (30) or
Formula (31):
σ u,b =
σ u,b =
where
γw
γ w × h w + R w × Wc
+ Pv
(30)
γ w × h w + R w × Wc + WL
(31)
10 6
10 6
i s the s p e ci fic weight o f water, 9 8 0 0 N/m
3;
hw
is the height of water surface above the top of the buried pipe, expressed in m;
Rw
i s the water buoya nc y fac tor;
© ISO 2017 – All rights reserved
21
ISO 14692-3:2017(E)
is the vertical soil load on the pipe, expressed in N/m 2 , see AWWA Manual M45 (second
edition), 5.7.3.5;
is the live load on the pipe, expressed in N/m 2 , see AWWA Manual M45 Second Edition,
5.7.3.6; the designer shall have the option of setting WL f
f
live loads are not present;
is the internal vacuum pressure, expressed in MPa, calculated as the atmospheric pressure
less the absolute pressure inside the pipe.
c
W
L
W
= 0
P
v
or the hyd ro te s t lo ad i ng c as e i
Live lo ad s a nd i nterna l vac uu m a re typic a l ly no t con s idere d s i mu ltane ou s ly i n any s i ngle lo ad i ng c a s e .
T he a l lowable buckl i ng s tre s s , i n M Pa, i s given b y
3
σ q,a =
1, 2 × C n × ( E hb × 10 ×
where
n
C
i s the s c a la r c a l ibration
t
3
r,min 0 , 33
)
Formula (32):
× (φ s × 10 6 × M s × k v ) 0 , 67
(32)
12
0, 5 × D r,min
fac tor to accou nt for s ome non l i ne a r e ffe c ts , = 0 , 5 5 ;
is the hoop bending modulus, expressed in MPa;
tr,min is the minimum reinforced pipe wall thickness, expressed in mm;
E
hb
Φs
s
M
v
k
i s the fac tor to accou nt for va ri abi l ity i n s ti ffne s s o f comp ac te d s oi l, = 0 ,9 i f no o ther data i s
available;
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is the constrained soil modulus, expressed in MPa, see WWA Manual M45 (second edition),
5.7.3.8;
i s the mo du lu s corre c tion
fac tor for Poi s s on's ratio o f the s oi l .
The ratio of σq,a to σu,b , the external radial pressure shall be greater than or equal to 2,5:
σ q,a
σ u,b
≥ 2, 5
(33)
where
σq,a
σu,b
is the allowable buckling stress, expressed in MPa;
is the external radial pressure, expressed in MPa.
7.10.4 Upheaval buckling pressure
Upheaval buckling is a common design issue for buried pipelines operating at high temperatures and/or
high pressures. When the high axial compressive forces are imposed on the pipeline due to the operating
conditions, the pipeline tends to buckle upwards. In order to prevent upheaval buckling, the pipeline
sha l l b e burie d de ep enough s o that the s oi l cover provides s u fficient res i s tance to the uphe ava l forces .
The designer shall consider acceptable practices to design for upheaval buckling in buried pipelines.
22
© ISO 2017 – All rights reserved
ISO 14692-3:2017(E)
7.11 Longitudinal pressure expansion
T he s trai n
from longitud i na l pre s s ure exp an s ion i n an u n re s trai ne d pipi ng s ys tem, ε
re ferre d to as " Poi s s on's e ffe c t", c an b e de term i ne d with
ε ap,avg =
where σhp,avg
σ hp,avg =
and σap,avg
8
Ea
− υ ha ×
Formula (35):
(35)
r
2 × t r,min
P × ID
OD
, com mon ly
(34)
Eh
i s c a lc u l ate d d i fferently from
P × ID
p,avg
σ hp,avg
i s c a lc u late d d i fferently from
σ ap,avg =
NOTE
σ ap,avg
Formula (34):
Formula (36):
2
r
(36)
2
− ID r2
r,min
Elastic response is associated with the average stress in the pipe wall.
Other design aspects
8.1
Fire
8.1.1
General
T he de s igner sh a l l de term i ne the fi re p er forma nce re qu i rements o f the pipi ng s ys tem . Fi re p er formance
is characterized in terms of the following properties:
a)
fi re endu rance;
b)
fi re re ac tion .
Fi re endu rance i s the abi l ity o f an element o f the s truc ture or comp onent to conti nue to p er form its
fu nc tion as a b arrier or s truc tu ra l comp onent du ri ng the cou rs e o f a fi re for a s p e c i fie d p erio d o f ti me .
Fi re re ac tion prop er tie s are materi a l-relate d
s pre ad
cha rac teri s tics
i nclud i ng
smoke and toxic gas release.
I f pipi ng
c an no t s ati s fy the
s mou lderi ng
re qui re d
fi re
consider alternative options which include
—
the s ur face fla me
a nd concerne d with ti me to ign ition;
and
p o s t-fi re - e xp o s ure
endu ra nce
or fi re
re ac tion
flam i ng;
and
prop er tie s ,
the
the
rate
o f he at,
de s igner
sh a l l
re -routi ng o f pipi ng to re duce or el i m i nate the fi re th re at,
— use of alternative materials, and
—
appl ic ation o f a s u itab le fi re -pro te c tive co ati ng.
I f a fi re -pro te c tive co ati ng i s u s e d, the de s igner sh a l l ta ke i nto con s ideration the rel i abi l ity b y wh ich the
co ati ng c an b e appl ie d and its abi l ity to mai ntai n its prop er tie s over s er vice l i fe ti me .
T he de s igner sha l l as s ign
the re qu i re d
fi re p er formance
o f the pipi ng s ys tem
cla s s i fic ation co de given i n I S O 14 69 2 -2 : 2 017, 5 . 5 .4. I t i s no t ne ce s s ar y
accord i ng to the fi re
for the enti re pipi ng s ys tem to
have the s a me fi re cla s s i fic ation .
© ISO 2017 – All rights reserved
23
ISO 14692-3:2017(E)
8.1.2
Fire endurance
The fire protection requirements for piping shall be evaluated from the total endurance time established
in the sa fety case for the facility and/or requirements for asset protection. The designer shall consider
the alternative use o f protective shielding, particularly i f the severest fire threat, for example a jet fire,
concerns just a small proportion o f the piping.
The fire endurance o f GRP piping components shall be determined using the appropriate method in
ISO 14692-2:2017, Annex H as agreed between the principal and the authority having jurisdiction.
The designer shall also take into consideration the following factors:
a) orientation o f the piping and fittings;
b) fluid conditions inside the piping, i.e. dry, stagnant or flowing;
c) possibility o f the formation o f steam traps within the piping, i.e. local removal o f the cooling e ffect
provided by water;
d) fire per formance o f penetrations;
e) inter face with metal fittings (e.g. valves, support clamps) that may provide a path for heat
conduction into the GRP component. Consideration shall be given to applying fire-protective
coatings;
f
) risk o f premature failure o f the supports in a fire, which can subject the piping to additional
stresses;
g) length o f support span compared to the length used to quali fy the fire per formance in
ISO 14692-2:2017, Annex H. I f necessary, the designer shall reduce the span or provide additional
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wall thicknessGet
to ensure
the piping
can maintain
its integrity
whileGroup
subject
to our
sel f-weight
NOTE
GRP is able to provide substantial fire resistance over a prolonged period o f time because o f the
insulating and mechanical properties o f the glass rein forcement and because pyrolysis o f the resin, which is an
endothermic reaction, absorbs heat from the fire and delays temperature rise. Both also enable an insulating and
protective char to form, which protects the underlying material.
For non-fire-protected water service piping, the slow weepage o f water through the pipe wall is an
important factor that contributes to the fire per formance o f GRP piping since it reduces the sur face
temperature o f the piping. The designer shall be satisfied that the fluid loss by weepage will not
adversely a ffect the function o f the system. The fire endurance properties o f GRP piping may be
di fferent for piping containing fluids other than water, for example produced water, glycol, diesel fuel
lines and closed drains. The designer shall be satisfied that the GRP piping can provide the required
fire resistance under these conditions. This may require a risk analysis and/or additional testing to be
carried out.
8.1.3
Fire reaction
Fire reaction is concerned with the following properties:
a) ease of ignition;
b) sur face spread o f flame characteristics;
c) rate of heat release;
d) smoke emissions;
e) toxic gas emissions.
24
© ISO 2017 – All rights reserved
ISO 14692-3:2017(E)
8.1.4
Fire-protective coatings
T he de s igner sh a l l con s ider the
coating:
fol lowi ng when de term i n i ng the p er formance o f the fi re -pro te c tive
a)
fi re ri s k (fi re zone) a nd fi re typ e for the are a i n wh ich the pipi ng i s i n s ta l le d;
b)
typ e, grade a nd d ia me ter(s) o f pip e;
c)
j oi nti ng s ys tem(s) u s e d;
d)
whe ther the pipi ng i s “d r y” or contai n s s tagna nt or flowi ng water;
e)
typ e and th ickne s s o f p a s s ive fi re -pro te c tive co ati ng;
f) effect of long-term weathering, exposure to salt water, temperature and exposure to UV radiation;
g)
e ffe c t o f fle xi ng , vibration, me chan ic a l abu s e, i mp ac t and therma l e xp an s ion;
h)
l iquid- ab s orp tion prop er tie s o f the co ati ng and pipi ng. T he fi re -pro te c tive prop er tie s o f the co ati ng
shall not be diminished when exposed to salt water, oil or bilge slops;
i) ease of attachment of the coating under site conditions and the effect of interfacial liquid
entrapment. T he ad he s ion qua l itie s o f the co ati ng s ha l l b e s uch th at the co ati ng do e s no t fla ke, ch ip,
or p owder when s ubj e c te d to a n ad he s ion te s t;
j)
e a s e o f rep ai r.
T he
fi re -pro te c tive
app l ic ation
co ati ng
o f fi re -pro te c tive
s hou ld
pre ferably
materia l s
be
appl ie d
by
the
manu fac tu rer
in
the
fac tor y.
T he
to ach ieve the fl ame s pre ad, s moke or toxic ity re qu i rements
shall be permanent to the piping construction. On-site application of such material shall be limited to
that re qu i re d for i n s ta l lation pur p o s e s , e . g. field j oi nts a nd pip e s upp or ts .
8.2
Static electricity
Po s s ible
s tatic
ele c tricity
bu i ld-up
in
GRP
pipi ng
s ys tem s
and
s ub s e quent
d i s chargi ng
s ha l l
be
con s idere d du ri ng de s ign . Fac tors that a ffe c t the bu i ld-up o f s tatic ele c tric ity i nclude the fol lowi ng:
a)
conduc tivity o f pip e lam i nate;
b)
conduc tivity o f tra n s p or te d flu id;
c)
flow rate s;
d)
tu rbu lence o f flow;
e)
envi ronmenta l hu m id ity;
f) external impingement of non-conducting media (e.g. wind, steam, etc.) ;
g)
i nter face are a b e twe en pip e and flu id .
E le c tro s tatic
cha rge s c a n b e generate d
s urrou nd i ng
explo s ive
on the i n s ide and outs ide o f GRP pipi ng or on any i n s u late d
metallic components in the line. Sparks from subsequent discharging can puncture pipe walls, ignite
atmo s phere s ,
or
ign ite
fla m mable
pip e
contents
i f s u fficient
air
is
pre s ent.
C on s ideration duri ng de s ign s ha l l there fore b e given to the s e ha z ard s when GRP pipi ng s ys tem s are
u s e d to c arr y flu id s c ap ab le o f generati ng ele c tro s tatic d i s cha rge s (s tatic acc u mu lators) or when u s i ng
GRP pipi ng s ys tem s
atmosphere).
i n h a z a rdou s
are as (i . e . a re a s that c an i n
fau lt cond ition s , contai n an e xplo s ive
I n prac tice, fluid s with a conduc tivity o f le s s than 1 0 0 0 p S/m are con s idere d to b e non- conduc tive
and there fore c ap able
o f generati ng
ele c tro s tatic
charge s .
Refi ne d
pro duc ts
and d i s ti l late s
fa l l i nto
th i s c ategor y a nd pipi ng u s e d to convey the s e l iqu id s sh a l l there fore b e ele c tric a l ly conduc tive . F lu id s
© ISO 2017 – All rights reserved
25
ISO 14692-3:2017(E)
with a conductivity o f greater than 1 000 pS/m are considered to be static non-accumulators, and can
there fore be conveyed through pipes not having special conductive properties when located in nonhazardous areas. Where conductive piping is required due to the fluid being non-conductive, volume
resistivity o f the GRP piping shall not exceed 10 3 Ωm.
Regardless o f the fluid being conveyed, the need for GRP piping to be electrically conductive shall be
considered if the piping passes through a hazardous area. Where conductive piping is required in a
hazardous area, sur face resistivity shall not exceed 10 5 Ω/mr.
NOTE 1 A definition o f a hazardous area is provided in ISO 14692-1. This definition can di ffer from the
definitions in the International Electrotechnical Commission (IEC) nor the National Electric Code (NEC).
NOTE 2
More recent studies (see References [9] and [10]) have shown that non-conductive GRP is not capable
o f producing an incendive discharge in methanol, which has a minimum ignition energy that is approximately hal f
that o f typical hydrocarbons. There fore, the risk o f incendive discharge in a hazardous area will be primarily due
to metal objects o f significant size that are electrically isolated on the piping, rather than the GRP piping itsel f.
The resistance to earth from any point in the piping system shall not exceed 10 6 Ω. In addition, metallic
fittings and mechanical joints shall be individually grounded i f there is not a su fficient electrical path
through the GRP piping.
Reference should be made to API RP 2003 for further details on controlling the risk of static discharge.
9
Installer and operator documentation
The system designer shall provide design in formation for use by the installation and operation
personnel. The information shall include, but not be limited to the following:
a) operating and design parameters;
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1) design pressure;
2) design temperature;
3) degree of cure properties;
4) MPR of each component;
5) mean and maximum velocity conditions in each piping system;
6) chemical resistance limitations, if applicable;
7) procedures to eliminate or control water hammer and cavitation, if applicable;
8) fire classification and location o f fire-rated pipe, i f applicable;
9) conductivity classification, location o f conductive pipe, earth linkage/grounding requirements
and location of earthing points;
10) criticality;
b) system drawings and support requirements for heavy equipment;
c) pre ferred locations for connection o f final joint in pipe loops, where appropriate;
d) guidance to enable early pressure-testing o f piping sections, i f appropriate.
26
© ISO 2017 – All rights reserved
ISO 14692-3:2017(E)
Annex A
(normative)
Cyclic de-rating factor — A 3
A.1 General
A 3 is the de-rating factor o f the e ffects o f cyclic variation in pressure. This annex outlines its derivation.
A.2 Formulae for A 3
When determining A3 , the following formulae may be used in lieu o f the graph.
fc =
σ Static 100 000
(A.1)
σ Cyclic 150 000 000
The cyclic long term strength factor, fc, is defined as the ratio o f the projected stress values at 100 000 h
(static loading) and 150 000 000 cycles (cyclic loading) respectively. These values shall be determined
from regression analysis as defined in the ASTM D2992-96, Procedures A (cyclic) and B (static). In case
no test data is available, fc shall be 4,0.
When Rc > 0,4:
A3 = (
1 − fc
0, 6 fc
)(
1 − Rc
log ( 150 × 10 6 ) − log ( 7 000 )
) log (
N)
 1− f

1 − Rc
c

+1 − TAN  (
)(
) ( log ( 7 000 )
 0, 6 f log ( 150 × 10 6 ) − log ( 7 000 ) 
c


(A.2)
When Rc ≤ 0,4:
A3 = (
+1 − (
1 − fc
fc
1 − fc
fc
)(
)(
1
log ( 150 × 10 6 ) − log ( 7 000 )
log ( 7 000 )
log ( 150 × 10 6 ) − log ( 7 000 )
) log (
N)
(A.3)
)
shall be greater than or equal to 1/fc . A3 shall be 1,0 if the calculated value is between 0,9 and 1,0. At
7 000 cycles or less, A 3 shall be 1,0. The minimum value for A 3 shall be 0,25.
A3
A.3 Theory and background
A review of Figure 2 will show a red line at R = 0,4. This line is the cyclic regression line from ASTM D2992
Procedure A, so there shall be no argument for using this line, since it is comes from “per formance
based testing” [critical concept in ISO 14692 (all parts)]. The de fault value o f 4,0 for the ratio o f static
regression to cyclic regression is conservative based on actual test data. Using the ratio o f cyclic
regression at 150 000 000 cycles to static regression at 100 000 hours is necessary to superimpose
cyclic on top o f static regression (i.e. both have the same exposure time for chemical degradation). Note
the values for cyclic regression have no sa fety factor (nominal regression line). The reason for this is A 3
superimposes the cyclic degradation factor on top o f the static degradation and the static degradation
© ISO 2017 – All rights reserved
27
ISO 14692-3:2017(E)
value is a lower confidence limit value (LCL stress) and applies f2 for design under different load cases.
I f this was not done, two sa fety factors would be applied to the design envelope.
I f there are no cracks, there is nothing to propagate. The strain limit from cyclic testing establishes the
strain limit for first crack. The very low strain limit will not intersect the static regression line, so the
mechanism o f resin matrix cracking from loads transverse to the fibres will continue for the 20 year
service life.
A.3.1 Uni-directional versus 54° laminates
Cyclic fatigue data for unidirectional laminates does show the potential for a strain limit in the resin,
below which there is no further cyclic fatigue when testing in the fibre direction, so the issue o f a strain
limit for the resin needs further review. However, a 54° pipe is not stressed just in the fibre direction.
Each ply is also stressed in the direction transverse to the fibres. This can be visualized by realizing
that strain along the fibres in the plus ply direction produces strain transverse to the fibres in the
adjacent minus ply direction and visa versa. There fore, data for fatigue in unidirectional rods, tested in
the direction o f the fibres provides little guidance for fatigue or resin strain limits in a laminate that is
bi-directionally loaded and produces strains and stresses transverse to the direction o f the fibres.
A.3.2 Fatigue limit
Data assembled by Battelle [17][18] from numerous pipe manufacturers indicated there was a fatigue
limit between 10 8 and 10 9 cycles. Data from Talreja [19] also implies a fatigue limit for strain in the resin
and the two values correlate fairly well. Based on this, a fatigue limit was arbitrarily set at 150 000 000
cycles, since this was the projected value from ASTM D2992 Procedure A.
A.3.3 Cyclic regression rate versus load ratio, Rc
There is not a lot oGet
f data
on the
possibility
o f the
cyclic
regression
rate Group
changing
thechats
load ratio (Rc) is
more
FREE
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from
Standard
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andasour
increased. However, the Battelle data did indicate there was a slower regression rate (slope) as the load
ratio increased. The current values are supported in the limited data that is available.
NOTE
This is the weakest part of the proposed partial factor A 3 (i.e. how to interpret between full cyclic
load and partial cyclic load). Any future data or theories may improve on the methodology for A 3 , but the current
values do have some support in the limited Battelle data.
28
© ISO 2017 – All rights reserved
ISO 14692-3:2017(E)
Annex B
(normative)
F
l
e
x
i
b
i
l
i
t
y
f
a
c
t
o
r
s
a
n
d
s
t
r
e
s
s
i
n
t
e
n
s
i
f
i
c
a
t
i
o
n
f
a
c
t
o
r
s
B.1 General
Flexibility factors shall be applied to bends and tees. Axial stress intensification factors (both in-plane
and out-of-plane) shall be applied to bends and tees.
Since all components are subject to the qualification programme in ISO 14692-2, which includes the
generation of hoop (and axial) stresses from an R = 2 test, hoop SIFs are not recommended for any
components.
There are no SIFs for flanges nor reducers nor pipe joints.
Since all components are subject to the qualification programme in ISO 14692-2, pressure stress
multipliers are not required.
B.2 Flexibility factors
B.2.1 General considerations
A flexibility factor describes the relationship between the axial flexural sti ffness o f a straight piece o f
or plain pipe and elbow (or tee), assuming that the plain pipe and elbow (or tee) have the same diameter
and wall thickness and are subject to the same bending moment. A flexibility factor greater than 1,0
indicates the elbow (or tee) is not as sti ff as the plain pipe (i.e. it is more flexible and will deflect/rotate
more than the plain pipe). An alloy elbow or tee is typically less sti ff than plain pipe. This is true because
as bending occurs in an elbow or tee, the cross-section changes shape (i.e. it is no longer circular). This
change in the cross-section reduces the moment of inertia, thus reduces the stiffness.
Standards such as ASME B31.3 and BS 7159 provide empirical formulae for flexibility factors for
di fferent pipe fittings. The formulae for flexibility factors are based only on the geometry o f the fitting.
There are a number of issues with GRP bends and tees that shall be taken into account when determining
the flexibility factors.
a) GRP, being an orthotropic material, typically has a hoop modulus that is higher than the axial
modulus. Compared to isotropic materials, where the axial and hoop moduli are the same, the
change in cross-section for GRP is typically less than the change in an isotropic material.
b) The thickness o f the bend is typically larger than the thickness o f plain pipe. This is typically
amplified further at the intrados and extrados o f the bend.
c) There is a stiffening effect from the overlap in material at the plain pipe/bend interface. These
issues seem to be supported by the o ffshore composites Joint Industry Project by SINTEF (see
Reference [11]) that showed the sti ffness o f bends to be much higher (i.e. the flexibility factor is
much lower) than calculated by empirical formulae.
NOTE
Incorrect flexibility factors can have a significant e ffect on the calculations o f stress in a piping
system. Unlike the stress intensification factor, a flexibility factor that is much higher than the actual value is not
necessarily conservative.
© ISO 2017 – All rights reserved
29
ISO 14692-3:2017(E)
B.2.2 Flexibility factors for bends
The calculations given in Formula (B.1) to Formula (B.5)
de term i ne the flexibi l ity fac tor for b end s , fi rs t
i n term s o f the comp onent its el f and then tran s late d to a glob a l flexibi l ity
fac tor th at c a n b e u s e d i n
pipi ng a na lys i s computer pro gra m s . T h i s i s ach ieve d b y mu ltiplyi ng the lo c a l flexibi l ity
ratio of
fac tor b y the
.
f
κb , for GRP bends is based on the pipe factor, λb , and the axial pressure correction
factor, δa, due to the effect of internal pressure.
Formula (B.1):
λb
(E I )
a b pipe
(E I )
a b bend
T he flexibi l ity
ac tor,
i s given b y
λb =
4t b R b
D
where
is the average wall thickness of the reference laminate of the bend, in mm;
b
t
D
i
R
b
(B.1)
2
i
i s the i nterna l d ia me ter o f the rei n force d b o dy o f the b end, i n m m;
is the mean pipe bend radius, in mm.
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Key
bend
t
toverlay
pipe
t
a
b
F
wall thickness of bend (mm)
thickness of lamination (mm)
wall thickness of pipe (mm)
angle s ub teded by tap er length o f laminatio n
angle s untended by overlap length o f laminatio n
i
30
g
u
r
e
B
.
1
—
T
e
r
m
i
n
o
l
o
g
y
f
o
r
c
a
l
c
u
l
a
t
i
n
g
t
h
e
f
l
e
x
i
b
i
l
i
t
y
f
a
c
t
o
r
o
f
a
b
e
n
d
u
s
i
n
g
l
a
m
i
n
a
t
e
d
j
o
i
n
t
s
© ISO 2017 – All rights reserved
ISO 14692-3:2017(E)
Key
wall thickness of bend (mm)
bend
tbell
tpipe
t
thicknes s o f b ell end o f j o int (mm)
wall thickness of pipe (mm)
a
b
angle s ub teded by no minal thicknes s o f b ell end
angle s untended by end thicknes s o f b ell end
Figure B.2
—
T
e
r
m
i
n
o
l
o
g
y
f
o
r
c
a
l
c
u
l
a
t
i
n
g
t
h
e
f
l
e
x
i
b
i
l
i
t
bonded joints
y
f
a
c
t
o
r
o
f
a
b
e
n
d
u
s
i
n
g
a
d
h
e
s
i
v
e
-
To determine tb for a bend, see Figure B.1 or Figure B.2 and Formula (B.2):
t
bend =
b
45
× ( t bend + t overlay ) + ( 1 −
b
45
)
(B.2)
× t bend
δa i s given b y Formula (B.3):
δa =
where
1
(B.3)

1 /3


⋅ ( Di / 2t b ) 2  
 1 +  2, 53 p / ( E h,bend ) ⋅ R b / t b



(
)
is the applied pressure, in MPa;
Eh,bend is the hoop modulus of the bend, in MPa.
p
T he fle xibi l ity fac tor for s mo o th b end s i s given a s a fu nc tion o f
κb = δa ⋅
0, 7
λb
⋅
E
a,pipe ⋅ t pipe
E
a,bend ⋅ t b
λb :
(B.4)
For a hand-lay b end , the fac tor 0 ,7 i s to b e replace d b y 1 , 0 .
© ISO 2017 – All rights reserved
31
ISO 14692-3:2017(E)
The flexibility factor for mitred bends is given as a function o f λb :
κb = δa ⋅
where
0, 64
(
λ b ) 0 , 83
⋅
E
t
a,pipe ⋅ pipe
E
(B.5)
a,bend ⋅ t b
is the axial modulus of the attached pipe, in MPa;
Ea,bend is the axial modulus of the bend, in MPa.
The ratio of the wall thicknesses is taken as an approximation of the ratio of the second moment of
areas. The axial modulus o f the pipe may be used in place o f that for the bend i f the modulus o f the bend
is not known.
An upper limit, based on experience, is placed on κb. For either smooth or mitred bends, it shall not be
greater than 3.
Ea,pipe
B.2.3 Flexibility factors for tees
The flexibility factor for tees shall be 1,0.
B.3 Stress intensification factors
Stress intensification factors, or SIFs, describe the relationship between the stress that would fail a
plain pipe and that which would fail an elbow or tee. While flexibility factors a ffect the sti ffness matrix
in a beam based finite element analysis, SIFs are typically used to modi fy the computed stresses at the
fittings. For alloys,Get
SIFsmore
are based
fatigue tests
were conducted
on thin,
pipe, elbows and
FREEon
standards
fromthat
Standard
Sharing Group
andsteel
our chats
tees, by Markl [12] using displacement controlled fatigue tests on piping components.
Since the fatigue behaviour o f GRP is likely to be considerably di fferent from that o f steel, the SIFs from
Markl's work has little value in the analysis o f GRP.
Furthermore, the availability o f SIF test data for GRP is limited due to the following.
a) The fabrication method o f the elbow/tee changes (e.g. spiral/filament wound versus
hand-lay/laminated) between products and between manu facturers.
b) The joint type will vary along with the fabrication method, thus resulting in di fferent levels o f
stress concentration at the connections.
c) The material properties o f the elbow/tee are not similar to those o f the plain pipe to which they are
attached.
d) The material properties o f the elbow/tee are not uni form within the fitting.
e) The wall thickness o f the fitting will vary from manu facturer to manu facturer and from one
fabrication method to another. Furthermore, the wall thickness will vary within the fitting itsel f
(e.g. the wall thickness at the intrados will be different than the wall thickness at the extrados).
The stress intensification factors in BS 7159 appear to be based on the work o f Kitching and Bond [13] .
SIFs are provided for bends, tees and reducing tees, both in-plane and out-of-plane. Correction factors
for internal pressure are also provided. The SIFs are based on the pipe factor, which is a function of the
geometry and dimensions o f the bend/tee. Additional work has been conducted by the same authors as
well as Hose and Myler a fter publication o f BS 7159 in1989 (see Re ference [12] to Reference [15]).
Care should be taken when using these factors because of the following.
a) Work carried out by the SINTEF o ffshore composites Joint Industry Project showed that some GRP
bends may be substantially sti ffer.
32
© ISO 2017 – All rights reserved
ISO 1 4692 -3 : 2 01 7(E)
b) Some manufacturing processes have changed since 1989 resulting in a reduction in the wall of the
plain pipe, but sometimes little to no change in the thickness o f the fitting.
c) Much o f the in formation about the stress intensification factors o f bends and tees is related to the
properties o f its equivalent plain pipe, which may not be representative o f the properties o f the
bend or tee.
One industry practice is to use an axial SIF o f between 2.2 to 2.5 for all bends and tees for both in-plane
and out-plane stress intensification factors (see Re ference [16 ]). However, this philosophy was based
on modelling the fitting wall thickness with its actual wall thickness, not that o f the equivalent plain
pipe. The philosophy in this document is to model the fitting wall thickness with its equivalent-rated
plain pipe wall thickness. Thus, one cannot make a direct comparison between the default SIF in this
document and other SIFs based on the actual wall thickness o f the fitting.
B
.
4
M
o
d
e
l
l
i
n
g
f
i
t
t
i
n
g
s
Design for pipe fittings will be primarily based on the fittings being stronger than the plain pipe to
which they can be connected (i.e. pipe o f similar materials and MPR).
NOTE
For some applications, such as marine piping in the bottom of the tanker where the pipe wall is
determined by external collapse pressure, the above statement will not be true and the MPR o f the plain pipe
thickness will be higher than the fittings.
It is expected that the e ffective failure and allowable stress envelope for fittings will be demonstrated to be
everywhere (i.e. for all R ratios) equal to or larger than that of the associated plain pipe, where associated
means the plain pipe (o f similar MPR) which the fitting was tested against (the “re ference” pipe).
Since fittings are to be (demonstrated) to be as strong or stronger than a (re ference) pipe o f the same
MPR and typically pipe fittings will be attached to plain pipe o f a lower or similar MPR, the fittings can
sa fely be ignored in the strength design in the same way that pipe joints can be ignored.
In particular installations, such as in the bottom of shipboard tanks, additional pipe wall thickness
may be utilized to increase free spans or to improve resistance to external pressure yet the MPR o f the
fittings does not need to be increased. In these instances the fitting may not be as strong as the plain
pipe to which it is attached and cannot be ignored in the design.
It is proposed to carry out design for fittings based on the strength and properties o f the re ference plain
pipe. Fittings would be modelled as short beam elements having the same ID and OD as the reference
plain pipe (i.e. the plain pipe that the fitting was shown to be stronger than and not necessarily the
plain pipe to which it is attached) and to have the same elastic properties and material strength as the
re ference plain pipe. At the fitting end nodes, the stress analysis model would transition from the real
adjacent plain pipe section and properties to the re ference pipe dimensions and properties.
The fittings can be installed into a library file using the ID, OD and elastic properties o f the re ference
plain pipe (not the real fitting dimensions or properties) and the end to end dimensions o f the fittings.
Details of the allowable design envelope for the reference plain pipe will be provided (for use on
the fittings). It is expected that pipe manu facturers would provide these library files for use by the
designers.
SIFs (values to be determined) would be provided for factoring the stresses at the end nodes. It is likely
that these SIFs would largely be based on the joint type rather than the fitting itsel f. Note that given the
qualification criteria SIFs shall not be required for the fittings themselves.
The stress analysis so ftware will calculate the associated re ference pipe stresses (not the real stress
in the fittings) at the intersection and end nodes. The compliance check for fittings will be carried out
based on the reference pipe code stresses and the reference pipe allowable stress envelope.
The stress analysis so ftware will calculate the adjacent pipe stresses at the end point nodes and apply
the SIF. The compliance check for pipe will be carried out based on the adjacent pipe code stresses and
the adjacent pipe allowable stress envelope.
© ISO 2017 – All rights reserved
33
ISO 14692-3:2017(E)
T h i s de s ign me tho d wi l l de a l corre c tly with s ituation s where add itiona l pip e wa l l th ickne s s has b e en
utilized to increase free spans or to improve resistance to external pressure.
f
See Figure B.3 f
or the prop o s e d me tho dolo g y
or mo del l i ng b end s a nd te e s .
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Figure B.3 — Proposed design methodology for bends and tees
B.5 Optional combined loading test
Instead of using the default SIF values, the manufacturer has the option of conducting a combined
test with in-plane bending, so that R is between 0,5 and 1,0.
As with the Rtest survival test in ISO 14692-2:2017, B.2.2, the hoop stress, σh,thr,SIF-test , and axial stress,
σa,thr,SIF-test
Formula (B.6) and Formula (B.7)
lo ad i ng te s t. T he i ntention o f the te s t i s to s ubj e c t a plai n pip e and a b end or te e to a 1 0 0 0 h s u r viva l
, comp onents sha l l comply with
σ h,thr,SIF-test =
, re s p e c tively.
σ h,thr,2:1
(B.6)
2
(B.7)
σ a,thr,SIF-test ≥ σ a,thr,2:1
This will generate an Rtest
f
PT 1000,SIF-test , for the Rtest
condition for GRE can then be calculated as the higher of the values in Formula (B.8) and Formula (B.9):
ratio o
34
≤ 1 , 0 . T he e qu iva lent 1 0 0 0 h te s t pre s s u re,
P
T 1000,SIF-test
= 0, 5 × rd 1 000 65 ×
P
T 1000,SIF-test
= 0, 5 × rd1 000 65 ×
,
,
MPR
65
0, 67
MPR
65
0, 67
×
t
r,act ×
t
r,mi n × D r,act
D
r,min
(B.8)
(B.9)
© ISO 2017 – All rights reserved
ISO 1 4692 -3 : 2 01 7(E)
NOTE
Since both a plain pipe and a fitting (bend or tee) are being tested, the test pressure for both the plain
pipe and the fitting is calculated. By using the higher o f the two values, the minimum stress requirements for
both components are satisfied.
In Formula (B.8), the actual dimensions of the test sample are required. For GRUP and GRVE, replace
rd1 000,65 with rd1 000,21 .
The temperature for this test shall be the same as the temperature in the Rtest survival test for the pipe
in ISO 14692-2:2017, B.2.2.
The in-plane bending moment, M, for this test shall satis fy the requirement o f Formula (B.7) and
Formula (B.10):
 PT1 000,SIF-test × D r,min 1 000 × M 

σ a,thr,SIF-test =
×
+


Z
rd
4 × t r,min

r
1 000 65


1
where
rd1 000,65
is the 1 000 h to 20 a scaling ratio at 65 °C;
rd1 000,21
is the 1 000 h to 20 a scaling ratio at 21 °C;
PT1 000,SIF-test
tr,min
D r,min
(B.10)
,
is the pressure applied during the 1 000 h test, expressed in MPa;
is the minimum reinforced pipe wall thickness (of the reference pipe based on the
fitting MPR), expressed in mm;
is the mean diameter of the minimum reinforced pipe wall (of the reference pipe
based on the fitting MPR), expressed in mm;
is the in-plane bending moment applied to the test sample, expressed in Nm;
Zr
is the actual reinforced section modulus of the pipe in the test sample, expressed in mm 3 .
For GRUP and GRVE, replace rd1 000,65 with rd1 000,21 .
M
I f the plain pipe, fitting and joint survives this combined loading test, the SIF is 1,0. I f any component
ails this combined loading test, the manu facturer may repeat the test at a lower bending moment. I f the
plain pipe, fitting and joint passes at the lower bending moment, the manu facturer may then linearly
f
interpolate a SIF between the default value of 1,5 and 1,0 based on the bending moment in the failed
test and the bending moment in the test that passed.
The test is only applicable for the plain pipe/fitting combination used in the test. For example, i f a 20
bar pipe and a 10 bar fitting is tested, these results may not necessarily extrapolate to a 20 bar pipe
with a 16 bar fitting. Also, the requirements for representative products in ISO 14692-2:2017, Annex E
and the requirements for scaling rules in ISO 14692-2:2017, Annex D apply.
© ISO 2017 – All rights reserved
35
ISO 14692-3:2017(E)
Bibliography
[1]
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[2]
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[5]
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[6]
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P iping F le xibili ty A nalysis A.R. C Markl. Tran s. Am . Soc. Mech . Eng. 1955
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[19] Talreja R. Fatigue of Composite Materials . CRC Press, First Edition, 1987
36
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