ISO 16708:2006
(Main)Petroleum and natural gas industries — Pipeline transportation systems — Reliability-based limit state methods
Petroleum and natural gas industries — Pipeline transportation systems — Reliability-based limit state methods
ISO 16708:2006 specifies the functional requirements and principles for design, operation and re-qualification of pipelines in the petroleum and natural gas industries using reliability based limit state methods as permitted by ISO 13623. Reliability-based limit state methods provide a systematic way to predict pipeline safety in design and operation. ISO 16708:2006 supplements ISO 13623 and can be used in cases where ISO 13623 does not provide specific guidance and where limit states methods can be applied, such as, but not limited to - qualification of new concepts, e.g. when new technology is applied or for design scenarios where industry experience is limited, - re-qualification of the pipeline due to a changed design basis, such as service-life extension, which can include reduced uncertainties due to improved integrity monitoring and operational experience, - collapse under external pressure in deep water, - extreme loads, such as seismic loads (e.g. at a fault crossing), ice loads (e.g. by impact from ice keels), - situations where strain-based criteria can be appropriate. ISO 16708:2006 applies to rigid metallic pipelines on-land and offshore used in the petroleum and natural gas industries.
Industries du pétrole et du gaz naturel — Systèmes de transport par conduites — Méthodes aux états-limites basées sur la fiabilité
General Information
Relations
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 16708
First edition
2006-04-01
Petroleum and natural gas industries —
Pipeline transportation systems —
Reliability-based limit state methods
Industries du pétrole et du gaz naturel — Systèmes de transport par
conduites — Méthodes aux états-limites basées sur la fiabilité
Reference number
ISO 16708:2006(E)
©
ISO 2006
---------------------- Page: 1 ----------------------
ISO 16708:2006(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.
© ISO 2006
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2006 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 16708:2006(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 1
4 Symbols and abbreviated terms . 5
4.1 Symbols . 5
4.2 Abbreviated terms . 6
5 Principles for design and operation . 7
6 Reliability based limit state methods. 9
6.1 General. 9
6.2 Design and operational data basis — Data gathering . 9
6.3 Safety requirements — target. 9
6.4 Failure mode analysis . 10
6.5 Uncertainty analysis. 10
6.6 Reliability analysis. 11
6.7 Safety and risk assessment. 11
7 Design and operational requirements . 12
7.1 General. 12
7.2 Design and construction. 12
7.3 Operation and maintenance . 12
7.4 Re-qualification . 13
7.5 Hazards . 13
8 Acceptance criteria and safety classes. 13
8.1 Safety requirements . 13
8.2 Classification of limit states . 14
8.3 Categorization of fluids. 14
8.4 Pipeline location and consequence categorization . 15
8.5 Safety classes . 16
9 Target safety levels and risk levels. 17
10 Failure modes. 17
10.1 General. 17
10.2 Internal pressure induced failure modes .17
10.3 External pressure induced failure modes . 18
10.4 Failure due to external load effects . 18
10.5 Failure due to third-party activity. 19
10.6 Corrosive environment induced failure modes . 19
10.7 Failure due to combined loads. 19
11 Pipeline operational management . 20
11.1 General. 20
11.2 Operational management procedures. 20
Annex A (informative) Uncertainty and reliability analysis — Method description. 23
Annex B (informative) Statistical database — Uncertainty values. 43
Annex C (informative) Target safety levels — Recommendations. 49
Bibliography . 56
© ISO 2006 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 16708:2006(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of 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 of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 16708 was prepared by Technical Committee ISO/TC 67, Materials, equipment and offshore structures
for petroleum, petrochemical and natural gas industries, Subcommittee SC 2, Pipeline transportation systems.
iv © ISO 2006 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 16708:2006(E)
Introduction
The International Standard ISO 13623 allows the use of innovative techniques and procedures such as
reliability-based limit state methods providing the minimum requirements of ISO 13623 are satisfied.
This International Standard provides the supplement to ISO 13623 in giving recommendations and specifying
the framework and principles for the application of the probabilistic approach, i.e. “reliability-based limit state
methods”.
Pipeline integrity management during design and operation are performed by the following two limit state
approaches:
⎯ a deterministic approach, with the use of safety or usage factors applied to characteristic loads and
resistances; and
⎯ a probabilistic approach, based on structural reliability analysis applied to the relevant limit states, e.g.
reliability-based limit state methods.
Both approaches satisfy the safety requirements; implicitly by the deterministic approach (via earlier-calibrated
safety factors) and explicitly by the probabilistic approach (a direct check on the actual safety level) as
illustrated in Figure 1.
Significant differences exist among member countries in the areas of public safety and protection of the
environment. Within the safety framework of this International Standard, such differences are allowed for and
individual member countries can apply their national requirements for public safety and the protection of the
environment to the use of this International Standard.
© ISO 2006 – All rights reserved v
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 16708:2006(E)
Petroleum and natural gas industries — Pipeline transportation
systems — Reliability-based limit state methods
1 Scope
This International Standard specifies the functional requirements and principles for design, operation and re-
qualification of pipelines in the petroleum and natural gas industries using reliability-based limit state methods
as permitted by ISO 13623. Reliability-based limit state methods provide a systematic way to predict pipeline
safety in design and operation.
This International Standard supplements ISO 13623 and can be used in cases where ISO 13623 does not
provide specific guidance and where limit states methods can be applied, such as, but not limited to,
⎯ qualification of new concepts, e.g. when new technology is applied or for design scenarios where industry
experience is limited,
⎯ re-qualification of the pipeline due to a changed design basis, such as service-life extension, which can
include reduced uncertainties due to improved integrity monitoring and operational experience,
⎯ collapse under external pressure in deep water,
⎯ extreme loads, such as seismic loads (e.g. at a fault crossing), ice loads (e.g. by impact from ice keels),
⎯ situations where strain-based criteria can be appropriate.
This document applies to rigid metallic pipelines on-land and offshore used in the petroleum and natural gas
industries.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 13623:2000, Petroleum and natural gas industries — Pipeline transportation systems
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
basic variable
load or resistance variable entering the limit state function including the variable accounting for model
uncertainty in the limit state function itself
3.2
characteristic load
nominal value of a load to be used in determination of load effects
NOTE Characteristic load is normally based upon a defined fractile in the upper end of the distribution function of the
load.
© ISO 2006 – All rights reserved 1
---------------------- Page: 6 ----------------------
ISO 16708:2006(E)
3.3
characteristic resistance
nominal value of a strength parameter to be used in determination of capacities
NOTE Characteristic resistance is normally based on a defined fractile in the lower end of the distribution function of
the resistance.
3.4
characteristic value
nominal value to characterize the magnitude of a stochastic variable
NOTE Characteristic value is normally defined as a fractile of the probability distribution of the variable.
3.5
commissioning
activities associated with the initial filling of a pipeline with the fluid to be transported
[ISO 13623]
3.6
construction
phase comprising installation, pressure testing and commissioning
3.7
design life
period of time selected for the purpose of verifying that a replaceable or permanent component is suitable for
the anticipated period of service
[ISO 13623]
3.8
design point
most probable outcome of the basic variables when failure occurs
NOTE The design point is the point on the limit-state surface with the highest probability density.
3.9
design value
value to be used in the deterministic design procedure, i.e., characteristic value multiplied by the safety factor
3.10
failure
loss of ability of a component or a system to perform its required function
3.11
fluid category
categorization of the transported fluid according to hazard potential
3.12
importance factor
dimensionless number between zero and one describing the contribution of a random variable to the overall
uncertainty
3.13
inspection
processes for determining the status of items of the pipeline system or installation and comparing it with the
applicable requirements
EXAMPLE Inspection can be by measuring, examination, testing, gauging or other methods.
2 © ISO 2006 – All rights reserved
---------------------- Page: 7 ----------------------
ISO 16708:2006(E)
3.14
limit state
state beyond which the pipeline no longer satisfies the design requirements
NOTE Categories of limit states for pipelines include serviceability limit state (SLS) and ultimate limit state (ULS).
3.15
limit-state design
structural design where specific limit states relevant for the actual case are explicitly addressed
NOTE A limit-state design check can be made both using the deterministic approach or using the probabilistic
approach where uncertainties are modelled.
3.16
limit state function
function of the basic variables, which has negative values when the structure fails and positive values when
the structure is safe
3.17
load
any action causing deformation, displacement, motion, etc. of the pipeline
3.18
load combination
set of loads acting simultaneously
3.19
load effect
effect of a single load or load combination on the pipeline
EXAMPLE Load effects include stress, strain, deformation, displacement.
3.20
location class
geographic area classified according to criteria based on population density and human activity
[ISO 13623]
3.21
maintenance
all activities designed to retain the pipeline in a state in which it can perform its required functions
[ISO 13623]
NOTE These activities include inspections, surveys, testing, servicing, replacement, remedial works and repairs.
3.22
maximum allowable incidental pressure
MAIP
maximum allowable internal pressure due to incidental operation of the pipeline or pipeline section
3.23
maximum allowable operating pressure
MAOP
maximum allowable pressure at which a pipeline, or parts thereof, is allowed to be operated
[ISO 13623]
© ISO 2006 – All rights reserved 3
---------------------- Page: 8 ----------------------
ISO 16708:2006(E)
3.24
mean value
first order statistical moment of the probability distribution function of the considered variable
3.25
mill test pressure
test pressure applied to pipe joints and pipe components upon completion of manufacture and fabrication at
the mill
3.26
model uncertainty
uncertainty in the predictions of a selected calculation model that remains when the exact values of all input
parameters are known
EXAMPLES Load model, strength model, function model for the pipeline.
3.27
nominal wall thickness
specified wall thickness of a pipe, which is equal to the minimum design wall thickness plus the negative
manufacturing tolerance and the corrosion allowance
3.28
normal operation
conditions that arise from the intended use and application of the pipeline, including associated condition and
integrity monitoring, maintenance and repair
NOTE Normal operations includes steady flow conditions over the full range of design flow rates, as well as possible
packing and shut-in conditions.
3.29
ovality
deviation of the pipeline perimeter from a circle, having the form of an elliptical cross-section
3.30
pipeline
those facilities through which fluids are conveyed, including pipe, pig traps, components and appurtenances,
up to and including the isolating valves
[ISO 13623]
3.31
offshore pipeline
pipeline laid in maritime waters and estuaries seaward of the ordinary high water mark
[ISO 13623]
3.32
on-land pipeline
pipeline laid on or in land, including lines laid under inland water courses
[ISO 13623]
3.33
reliability
ability of a component or a system to perform its required function without failure during a specified time
interval
NOTE Reliability equals 1 minus the failure rate, P .
f
4 © ISO 2006 – All rights reserved
---------------------- Page: 9 ----------------------
ISO 16708:2006(E)
3.34
risk
combination of the probability of an event and the consequences of the event
[ISO 17776]
NOTE Individual risk is related to the risk of a single person injury/death and societal risk is the risk of human safety
in the entire society affected by the pipeline.
3.35
safety class
concept to classify the criticality of pipelines
3.36
safety factor
γ
factor by which the characteristic value of a variable is multiplied to give the design value
3.37
specified minimum tensile strength
SMTS
minimum ultimate tensile strength required by the specification or standard under which the material is
purchased
3.38
specified minimum yield strength
SMYS
minimum yield strength required by the specification or standard under which the material is purchased
[ISO 13623]
3.39
system reliability
reliability of a system of more than one element, or the reliability of an element which has more than one
relevant failure mode
3.40
target safety level
maximum acceptable failure probability level for a particular pipeline and limit state condition
4 Symbols and abbreviated terms
4.1 Symbols
C consequences of a given failure
f
P probability of a failure, i.e. the actual failure rate calculated
f
P target safety level, equal to the target probability of failure
f, target
R resistance or the capability of a structure or part of a structure to resist load effects
S load effect on a structure or part of a structure
γ safety factor
g(x) limit state function
© ISO 2006 – All rights reserved 5
---------------------- Page: 10 ----------------------
ISO 16708:2006(E)
D pipe diameter
L gouge length of impacts
d gouge depth of impacts
d dent depth of impacts
d
f frequency of occurrence of impacts
imp
f ovality
σ yield strength
y
σ ultimate tensile strength
u
t time
f (x) joint distribution
x
I(x) indicator function
H(x) event margin
C vector of serviceability constraints
∆K stress intensity factor range
p random pressure variable
λ scale parameter
S characteristic load effect
C
S environmental load effects
C,E
S functional load effects
C,F
R characteristic value of component resistance, based on characteristic values of material properties
C
f characteristic values of material properties, for example yield strength
C
γ partial load effect factors
i
η resistance or strength usage factors
R
γ partial material factors
m
∆α additive partial geometrical quantities
4.2 Abbreviated terms
ALS accidental limit state
CTOD crack tip opening displacement
FLS fatigue limit state
LRFD load and resistance factor design
6 © ISO 2006 – All rights reserved
---------------------- Page: 11 ----------------------
ISO 16708:2006(E)
MAIP maximum allowable incidental pressure
MAOP maximum allowable operating pressure
QRA quantitative risk analysis
SLS serviceability limit state
SMTS specified minimum tensile strength
SMYS specified minimum yield strength
SRA structural reliability analysis
ULS ultimate limit state
5 Principles for design and operation
Pipeline design and operational principles can be implemented using different methods with varying levels of
detail as indicated in Figure 1. In order of decreasing level of detail, these methods are quantitative risk
analysis (QRA) and structural-reliability analysis (SRA), both of which are probabilistic, and the deterministic
limit-state design methods [partial safety-factor design and load and resistance-factor design (LRFD)], which
are collectively termed LRFD in this document.
The LRFD formats apply partial safety factors to the characteristic load and resistance properties,
representing more traditional design for pipelines. This is the format applied in ISO 13623 by the use of the
hoop stress design factor and the equivalent stress design factor, i.e. one partial factor only. This approach is
classified as deterministic, as no quantitative information about the safety margin is given. The partial safety
factors in the LRFD format have to be calibrated by the use of reliability-based methods prior to the publication
to satisfy its design requirements and provide a satisfactory safety margin. The routine use of the LRFD
formats do not, therefore, require the partial safety factors to be determined. In LRFD approaches (see left
side of Figure 1), the load and resistance are defined by their characteristic values and partial safety factors
are applied separately (as required) to the characteristic values of load, resistance and material properties.
Application of the probabilistic approach (SRA and QRA) involves the steps on the right hand side of Figure 1.
The limit-state definition is generally the same as for the LRFD. In this approach, load effects and resistance
are represented by probability functions, given in terms of distribution type, mean value and standard
deviation. This approach is classified as probabilistic, as quantitative information about the safety margin in
terms of reliability or the complementary failure probability is given. The most comprehensive probabilistic
method is QRA, as it takes into consideration the consequences of failure.
The format and requirements for the reliability-based limit state method are described in Clause 6.
© ISO 2006 – All rights reserved 7
---------------------- Page: 12 ----------------------
ISO 16708:2006(E)
Figure 1 — Pipeline design and assessment approaches
8 © ISO 2006 – All rights reserved
---------------------- Page: 13 ----------------------
ISO 16708:2006(E)
6 Reliability-based limit state methods
6.1 General
Use of the reliability-based limit state approach shall include
⎯ determining the design and operational data basis: data gathering, see 6.2,
⎯ determining the safety requirements: targets, see 6.3,
⎯ failure mode analysis; see 6.4,
⎯ uncertainty analysis including estimation of probability functions; see 6.5,
⎯ reliability analysis, see 6.6, and
⎯ safety and risk assessment, see 6.7.
6.2 Design and operational data basis — Data gathering
Data gathering is collecting and defining all relevant information related to the pipeline to be considered and
shall include the following information:
a) design basis and operational information including
⎯ pipe system characteristics, e.g. pipe diameter, pipeline length, product composition, operating
conditions (pressure, temperature), design life and interface facilities,
⎯ definition of loads and load effects and associated hazards,
⎯ definition of linepipe properties (resistance) and relevant pipeline capacities, and
⎯ inspection and monitoring philosophy for operation, e.g. integrity management plan;
b) Hazard identification and classification of failure conditions including
⎯ determination of limit state conditions which constitute structural non-compliance for the pipeline as
judged against the safety requirements and constraints, e.g. partial or total loss of supply, any loss of
fluid, loss of operability or serviceability without loss of fluid, and
⎯ determination how the pipeline can become structurally non-compliant, in terms of loadings,
resistance, and degradation; i.e. hazard identification.
Determination of operational requirements and classification of failure conditions shall be performed in
accordance with Clauses 7 and 8.
6.3 Safety requirements — target
The objective of this step is to define the relevant safety requirements for the hazards/failure modes.
a) The target safety level shall be defined for all pipeline sections according to the location and
consequence categorization in Clause 8;
b) Target safety levels shall be determined for all phases of the pipeline design life; e.g. construction, normal
operation, and any temporary conditions.
© ISO 2006 – All rights reserved 9
---------------------- Page: 14 ----------------------
ISO 16708:2006(E)
Target safety levels shall be based upon public safety, environmental and business issues, taking account of
safety and serviceability principles dictated by society, the local regulator, the specific company involved, and
the performance requirements for the pipeline under consideration.
These targets should be clearly communicated to all relevant stakeholders.
Target safety levels shall be defined in accordance with Clauses 8 and 9. If no risk and/or safety levels are
predefined, equivalent target probabilities of failure, P , may be taken from Annex C based on the current
f,target
state of technology and design practice.
6.4 Failure mode analysis
The objective of this step is to identify all relevant failure modes (i.e. significant hazards with a probability of
occurrence larger than the target safety level for the appropriate condition). The steps involved are
a) the gathering of data to assess the severity of all hazards identified,
b) the assessment of each hazard against the target safety requirement to determine whether each hazard
is possible but incredible (e.g. a plane crash on a particular pipeline), or both possible and credible (e.g.
corrosion),
This analysis may be undertaken in a semi-qualitative manner, e.g. a return period of a particular hazard
−5
estimated as being below 10 /km/year, being smaller than the target performance requirement, implies that
the hazard is insignificant, and therefore a probabilistic assessment is not necessary and the hazard can be
excluded from the further analysis.
Failure conditions shall be considered according to the classification given in 8.2. Justification shall be given
for the classification of any hazard determined to be as “possible but incredible”, such documentation can, for
example, be frequencies of occurrence. The significant (possible and credible) failure conditions shall be
included in the uncertainty and reliability analysis.
6.5 Uncertainty analysis
In the uncertainty analysis, the significant failure conditions shall be considered, including
a) establishment of all measures that are (or can be) implemented to mitigate against the hazard,
b) determination of the appropriate method of assessment and identification of the most relevant limit state
function, e.g. rupture, leak,
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.