oSIST prEN ISO 16708:2026

SLOVENSKI STANDARD
01-november-2026
Naftna in plinska industrija, vključno z nizkoogljično energijo - Transportni
cevovodni sistemi - Metode na podlagi mejnih stanj zanesljivosti (ISO/DIS
16708:2026)
Oil and gas industries including lower carbon energy - Pipeline transportation systems -
Reliability-based limit state methods (ISO/DIS 16708:2026)
Erdöl- und Erdgasindustrie - Rohrleitungstransportsysteme - Zuverlässigkeitsanalysen
(ISO/DIS 16708:2026)
Industries du pétrole et du gaz, y compris les énergies à faible teneur en carbone -
Systèmes de transport par conduites - Méthodes aux états limites basées sur la fiabilité
(ISO/DIS 16708:2026)
Ta slovenski standard je istoveten z: prEN ISO 16708
ICS:
75.200 Oprema za skladiščenje Petroleum products and
nafte, naftnih proizvodov in natural gas handling
zemeljskega plina equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 16708
ISO/TC 67/SC 2
Oil and gas industries including
Secretariat: UNI
lower carbon energy — Pipeline
Voting begins on:
transportation systems —
2026-08-25
Reliability-based limit state
Voting terminates on:
methods
2026-11-17
ICS: 75.200
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
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PUBLISHED AS SUCH.
This document has not been edited by the ISO Central Secretariat.
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Reference number
ISO/DIS 16708:2026(en)
DRAFT
ISO/DIS 16708:2026(en)
International
Standard
ISO/DIS 16708
ISO/TC 67/SC 2
Oil and gas industries including
Secretariat: UNI
lower carbon energy — Pipeline
Voting begins on:
transportation systems —
Reliability-based limit state
Voting terminates on:
methods
ICS: 75.200
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document has not been edited by the ISO Central Secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2026
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
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Published in Switzerland Reference number
ISO/DIS 16708:2026(en)
ii
ISO/DIS 16708:2026(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols and abbreviated terms. 6
4.1 Symbols .6
4.2 Abbreviated terms .7
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 .10
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 . 12
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 . 15
9 Target safety levels and risk levels .16
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 . 20
11 Pipeline operations management . .20
Annex A (informative) Uncertainty and reliability analysis — Method description.22
Annex B (informative) Statistical database — Uncertainty values .42
Annex C (informative) Target safety levels — Recommendations .49
Bibliography .53

iii
ISO/DIS 16708:2026(en)
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.
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 different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 67, Oil and gas industries including lower
carbon energy, Subcommittee SC 2, Pipeline transportation systems.
This second edition cancels and replaces the first edition (ISO 16708:2006), which has been technically
revised.
The main changes are as follows:
— Adaption to latest research
— Consideration of updated damage data bases
— Consideration of updated calculation methods
— Consideration of conversion of transported media
— Alignment with other standards
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
ISO/DIS 16708:2026(en)
Introduction
The International Standard ISO 13623 allows the use of innovative techniques and procedures providing the
requirements of ISO 13623 are satisfied but still allowing to change the applied safety margins provided the
target safety levels given in this standard are fulfilled.
Reliability limit states methods have been developed and considered as included in those allowed techniques
and procedures.
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.

v
DRAFT International Standard ISO/DIS 16708:2026(en)
Oil and gas industries including lower carbon energy —
Pipeline transportation systems — Reliability-based limit
state methods
1 Scope
This International Standard specifies the functional requirements and principles for design, operation and
requalification 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 or change of
the transported fluid, which can include reduced or increased uncertainties due to improved integrity
monitoring and operational experience or limited information on pipeline properties relevant to the new
service
— 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 oil and gas industries including
lower carbon energy.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements 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 3183, Petroleum and natural gas industries — Steel pipe for pipeline transportation systems
ISO 12747, Oil and gas industries including lower carbon energy — Pipeline transportation systems —
Requirements and guidance for pipeline life extension assessment
ISO 13623, Petroleum and natural gas industries — Pipeline transportation systems
ISO 13623, Petroleum and natural gas industries — Pipeline transportation systems
ISO 17776, Petroleum and natural gas industries — Offshore production installations — Major accident hazard
management during the design of new installations
ISO 19345, Petroleum and natural gas industry — Pipeline transportation systems — Pipeline integrity
management specification
EN 1991-1, Eurocode 1, Basis of Design and Actions on Structures, Part 1, Basis of design

ISO/DIS 16708:2026(en)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
basic variable
text of the definition 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 1 to entry: Characteristic load is normally based upon a defined fractile in the upper end of the distribution
function of the load.
3.3
characteristic resistance
nominal value of a strength parameter to be used in determination of capacities
Note 1 to entry: 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 1 to entry: 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 system with the fluid to be transported
[SOURCE: ISO 13623]
3.6
construction
phase comprising installation, pressure testing and commissioning
3.7
design life
period for which the design basis is planned to remain valid
[SOURCE: ISO 13623]
3.8
design point
most probable outcome of the basic variables when failure occurs
Note 1 to entry: 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
ISO/DIS 16708:2026(en)
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.
3.14
limit state
state beyond which the pipeline no longer satisfies the design requirements
Note 1 to entry: Categories of limit states for pipelines include serviceability limit state (SLS) and ultimate limit state
(ULS). Ultimate limit states include fatigue and accidental limit states as well.
3.15
limit-state design
structural design where specific limit states relevant for the actual case are explicitly addressed
Note 1 to entry: 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, bending moment, axial force.
3.20
location class
geographic area classified according to criteria based on population density and human activity
[SOURCE: ISO 13623]
ISO/DIS 16708:2026(en)
3.21
maintenance
all activities designed to retain the pipeline system in a state in which it can perform its required functions
Note 1 to entry: These activities include inspections, surveys, testing, servicing, replacement, remedial works and
repairs.
[SOURCE: ISO 13623]
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 system, or parts thereof, is allowed to be operated in
compliance with this document
Note 1 to entry: The MAOP is established by the maximum pressure achieved during testing
[SOURCE: ISO 13623]
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
EXAMPLE 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 1 to entry: Normal operations include 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

ISO/DIS 16708:2026(en)
3.30
pipeline
those components of a pipeline system connected together to convey fluids between stations and/or plants,
including pipe, pig traps, components, appurtenances, spools, risers, isolation valves, and sectionalizing
valves
[SOURCE: ISO 13623]
3.31
offshore pipeline
pipeline laid in maritime waters and estuaries seaward of the ordinary high water mark
[SOURCE: ISO 13623]
3.32
onshore pipeline
on-land pipeline
pipeline laid on or in land, including lines laid under inland waterways
Note 1 to entry: pipelines laid in large inland water bodies such as lakes can be designed, constructed and operated in
the same way as offshore pipelines.
[SOURCE: 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 1 to entry: Reliability equals 1 minus the failure rate, P .
f
3.34
risk
combination of the probability of an event and the consequences of the event
Note 1 to entry: 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.
[SOURCE: ISO 17776]
3.35
safety class
concept to classify the criticality of pipelines in the event of failure
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
[SOURCE: ISO 13623]
3.38
specified minimum yield strength
SMYS
minimum yield strength required by the specification or standard under which the material is purchased
[SOURCE: ISO 13623]
ISO/DIS 16708:2026(en)
3.39
system effect
System effects are present when potential structural failure occurs in connection with the weakest pipe
joint.
[1]
[SOURCE: DNV ST F101 modified “pipe section” with “pipe joint”]
3.40
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
3.41
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
g(x) limit state function
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
R characteristic value of component resistance, based on characteristic values of material properties
C
S load effect on a structure or part of a structure
S characteristic load effect
C
S environmental load effects
C,E
S functional load effects
C,F
γ safety factor
γ partial load effect factors
i
γ resistance factor
R
µ mean
σ standard deviation
σ yield strength
y
σ ultimate tensile strength
u
γ resistance factors
Ri
ISO/DIS 16708:2026(en)
4.2 Abbreviated terms
ALS accidental limit state
CTOD crack tip opening displacement
CoV coefficient of variation
FLS fatigue limit state
FORM First-order reliability method
LRFD load and resistance factor design
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
SORM Second-order reliability method
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 to be compared with the target failure
rate to be defined in accordance with this standard. 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/DIS 16708:2026(en)
Figure 1 — Pipeline design and assessment approaches

ISO/DIS 16708:2026(en)
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,
— inspection and monitoring philosophy for operation, e.g. integrity management plan and
— for assessment of an existing pipeline, operations, inspection and monitoring data as summarised in
Annex C of ISO 12747: 2025.
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.
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.

ISO/DIS 16708:2026(en)
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
f,target
current 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, etc.,
c) collection of data that is required to quantify the variables in the limit state function,
d) assessment of the uncertainty associated with the data and limit state function (model uncertainty),
and
e) selection of appropriate values for all variable parameters.
Uncertainty analysis and probabilistic modelling can be performed according to procedures given in Annex A
and, if no other case-specific information is available, uncertainty measures can be found in Annex B. The
uncertainty modelling should include all variables entering the limit state equation. The most relevant
statistical properties are the mean value and the standard deviation in addition to information about the
distribution function. Any correlation between parameters is important and shall be evaluated.
EXAMPLE For external corrosion of the pipeline, the mitigation measures can be a combination of any of the
following: corrosion allowance, anti-corrosion coating, cathodic protection system, inspection and repair policy. It is
noted that there are several ways of implementing an inspection, monitoring and repair policy.
6.6 Reliability analysis
The reliability analysis is to calculate the failure probability (P ) for each significant limit state identified.
f
The steps to be included are as follows.
a) Probabilistic modelling of the limit state function, i.e. analytical formulation of the failure criteria. For
a given limit state, a probabilistic design models the load, S, and resistance, R. The corresponding limit
state function may be expressed in the form:

ISO/DIS 16708:2026(en)
gx RS (1)

b) Selection of the most appropriate probabilistic calculation method for the problem and level of accuracy,
possible methods include first order second moment (FOSM), “reliability” methods (FORM/SORM),
Monte Carlo, or direct integration.
c) Perform probabilistic calculations, i.e. calculate the failure probability for each relevant limit state. The
reliability analysis may then be performed when the statistical properties of the limit state functions
are defined (load effect and resistance properties). When the distribution functions for R and S are
established through uncertainty analysis, the failure probability is calculated by
Pf RS, dRdS (2)

fR ,S
gx 0

The reliability analysis can be performed in accordance with the guidance given in Annex A or other relevant
calculation procedures.
A calculated probability of failure is not a physical property of the pipeline itself, but gives a notional value.
The calculated probability of failure depends on the method and procedure applied, including uncertainties
in data and methods. It is, however, the intent of this document to standardize the methods and procedures
used for the reliability-based approach and thus to bring this into a comparable level within the industry.
6.7 Safety and risk assessment
This step is to check that the pipeline meets the safety requirements (criteria). The reliability shall be
compared with the requirements by ensuring that:
PP≤ (3)
f f,target
where
P is the calculated probability of failure from the reliability analysis;
f
P is the target safety level that should not be exceeded for a design and/or operation to be
f,target
accepted.
If the requirements are not met, the pipeline details should be modified and the assessment repeated (new
iteration in Figure 1).
When applying Equation (3), the correct comparisons shall be undertaken; i.e. individual or system failure
modes; for the correct time and spatial units; for the correct phase in the design life, e.g. operational or
temporary.
The physical design parameters (e.g. wall thickness) selected to mitigate against failure shall satisfy all
performance requirements.
The safety check shall be performed in accordance with Clauses 8 and 9.
Similar safety principles apply to both offshore and on-land pipelines, but differences in failure consequences
and safety regimes result in different required target safety levels, P .
f,target
For both offshore and on-land pipeline applications, it is appropriate to control the failure probability (P )
f
as a function of the consequences, as established by the safety class designation (see Clause 8) to obtain a
uniform risk level. For on-land pipelines, the acceptable probability of failure is also a function of the pipeline
pressure and diameter to account for the impact of these parameters on the failure consequences. A uniform
risk level is generally the objective for any application.

ISO/DIS 16708:2026(en)
Equation (3) is equivalent to Equation (4) when risk is calculated as the product of probability of failure and
consequences of that failure:
calculated risk ≤ allowable risk (4)
The target safety levels, P , given in Annex C have been derived from risk assessments and these values
f,target
may be applied if no additional explicit risk assessment is performed.
Further technical details and requirements of the various items to be considered in the reliability-based
approach are described in Clauses 7 to 10 and in Annex A.
7 Design and operational requirements
7.1 General
The safety against potential failure modes shall be checked for all conditions during construction and
operation (including re-qualification) throughout the lifetime of the pipeline.
7.2 Design and construction
The pipeline shall be designed and constructed to satisfy the following performance requirements:
a) to perform adequately under all anticipated load effects (serviceability limit state requirement);
b) to withstand anticipated load effects during its construction and operation (ultimate limit state
requirements);
c) to avoid failure under repeated load effects during construction and operation (ultimate limit state —
fatigue limit state);
d) to avoid failure due to accidents during construction and operation (ultimate limit state — accidental
limit state).
7.3 Operation and maintenance
The pipeline shall be operated and maintained such that the safety and the integrity is kept within the target
safety level.
An integrity management programme shall be implemented by the operator to satisfy the safety
requirements given in this document. Maintenance includes the requirements of inspections, inspections
on special occasions (e.g., after an accident or severe environmental events), the upgrading of protection
systems and repair of components.
The integrity of the pipeline may be achieved by either a maintenance programme and/or designing to avoid
deterioration that can affect the integrity of the pipeline in those areas where the pipeline cannot or is not
maintained.
The rate of deterioration may be estimated based on numerical calculations, experimental investigations,
experiences from other pipelines or a combination of these.
7.4 Re-qualification
Re-qualification of the pipeline integrity shall be performed when
— the design life is to be extended,
— the pipeline has been found to have deteriorated or have been seriously damage
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