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DNV-OS-F101 Submarine Pipeline Systems
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SECTION 2
Safety PhilosophySec.2
A. General
Sec.2
A 100 Objective
Sec.2 A
101 This section presents the overall safety philosophy that shall
be applied in the concept development, design, construction, operation
and abandonment of pipelines.Sec.2
A 200 Application
Sec.2 A
201 This section applies to all submarine pipeline systems which
are to be built and operated in accordance with this standard.
Sec.2 A
202 The integrity of a submarine pipeline system shall be ensured
through all phases, from initial concept through to final de-commissioning,
see Figure 1. This standard defines two integrity stages: establish
integrity in the concept development, design and construction phases;
and maintain integrity in the operations phase.
Sec.2 A
203 This section also provides guidance for extension of this standard
in terms of new criteria, etc.Sec.2
B. Safety Philosophy Structure
Sec.2
B 100 General
Sec.2 B
101 The integrity of the submarine pipeline system constructed
to this standard is ensured through a safety philosophy integrating
different parts as illustrated in Figure 2.
Sec.2 B
102 The overall safety principles and the arrangement of safety
systems shall be in accordance with DNV-OS-A101 and DNV-OS-E201.Sec.2
B 200 Safety objective
Sec.2 B
201 An overall safety objective shall be established, planned and
implemented, covering all phases from conceptual development until
abandonment.Guidance note:
Most companies have a policy regarding human aspects, environment
and financial issues. These are typically on an overall level, but
may be followed by more detailed objectives and requirements in
specific areas. These policies should be used as a basis for defining
the Safety Objective for a specific pipeline system. Typical statements
may be:| - | The impact on the environment
shall be reduced to as far as reasonably possible.| - | No releases will be accepted during operation of the
pipeline system.| - | There shall be no serious accidents or loss of life
during the construction period.| - | The pipeline installation shall not, under any circumstances impose
any threat to fishing gear.| - | Diverless installation and maintenance. | | | | |
Statements such as those above may have implications for all
or individual phases only. They are typically more relevant for
the work execution (i.e. how the Contractor executes his job) and specific
design solutions (e.g. burial or no burial). Having defined the
Safety Objective, it can be a point of discussion as to whether
this is being accomplished in the actual project. It is therefore
recommended that the overall Safety Objective be followed up by
more specific, measurable requirements.
If no policy is available, or if it is difficult to define
the safety objective, one could also start with a risk assessment.
The risk assessment could identify all hazards and their consequences, and
then enable back-extrapolation to define acceptance criteria and
areas that need to be followed up more closely.
In this standard, the structural failure probability is reflected
in the choice of three safety classes (see B400). The choice of
safety class should also include consideration of the expressed
safety objective. ---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
Fig. 1 Integrity assurance activities during the pipeline system phases
*indicates Section in this Standard.
Fig. 2 Safety Philosophy structure
Sec.2
B 300 Systematic review of risksSec.2 B
301 A systematic review shall be carried out at all phases to identify
and evaluate threats, the consequences of single failures and series
of failures in the pipeline system, such that necessary remedial
measures can be taken. The extent of the review or analysis shall
reflect the criticality of the pipeline system, the criticality
of a planned operation, and previous experience with similar systems
or operations.Guidance note:
A methodology for such a systematic review is quantitative
risk analysis (QRA). This may provide an estimation of the overall risk
to human health and safety, environment and assets and comprises:| - | hazard identification| - | assessment of probabilities of failure events| - | accident developments| - | consequence and risk assessment. | | | |
The scope of the systematic review should comprise the entire pipeline
system, and not just the submarine pipeline system as defined by
this standard.
It should be noted that legislation in some countries requires
risk analysis to be performed, at least at an overall level to identify critical
scenarios that might jeopardise the safety and reliability of a
pipeline system. Other methodologies for identification of potential
hazards are Failure Mode and Effect Analysis (FMEA) and Hazard and
Operability studies (HAZOP).---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
Sec.2 B
302 Special attention shall be given to sections close to installations
or shore approaches where there is frequent human activity and thus
a greater likelihood and consequence of damage to the pipeline.
This also includes areas where pipelines are installed parallel
to existing pipelines and pipeline crossings.Sec.2
B 400 Design criteria principlesSec.2 B
401 In this standard, structural safety of the pipeline system is
ensured by use of a safety class methodology. The pipeline system
is classified into one or more safety classes based on failure consequences,
normally given by the content and location. For each safety class,
a set of partial safety factors is assigned to each limit state.Sec.2
B 500 Quality assuranceSec.2 B
501 The safety format within this standard requires that gross
errors (human errors) shall be controlled by requirements for organisation
of the work, competence of persons performing the work, verification
of the design, and quality assurance during all relevant phases.
Sec.2 B
502 For the purpose of this standard, it is assumed that the operator
of a pipeline system has established a quality objective. The operator
shall, in both internal and external quality related aspects, seek
to achieve the quality level of products and services intended in
the quality objective. Further, the operator shall provide assurance
that intended quality is being, or will be, achieved.
Sec.2 B
503 Documented quality systems shall be applied by operators and
other parties (e.g. design contractors, manufactures, fabricators
and installation contractors) to ensure that products, processes
and services will be in compliance with the requirements of this
standard. Effective implementation of quality systems shall be documented.
Sec.2 B
504 Repeated occurrence of non-conformities reflecting systematic
deviations from procedures and/or inadequate workmanship
shall initiate:| — | investigation into the causes of the non-conformities | | — | reassessment of the quality system | | — | corrective action to establish possible acceptability
of products | | — | preventative action to prevent re-occurrence of similar non-conformities. |
Guidance note:
ISO 9000 give guidance on the selection and use of quality
systems.---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
Sec.2 B
505 Quality surveillance in the construction phase shall be performed
by the operator or an inspectorate nominated by the operator. The
extent of quality surveillance shall be sufficient to establish
that specified requirements are fulfilled and that the intended
quality level is maintained.
Sec.2 B
506 To ensure safety during operations phase, an integrity management
system in accordance with Sec.11 C shall be established and maintained.Sec.2
B 600 Health, safety and environmentSec.2 B
601 The concept development, design, construction, operation and
abandonment of the pipeline system shall be conducted in compliance
with national legislation and company policy with respect to health,
safety and environmental aspects.
Sec.2 B
602 The selection of materials and processes shall be conducted
with due regard to the safety of the public and employees and to
the protection of the environment.Sec.2
C. Risk Basis for DesignSec.2
C 100 GeneralSec.2 C
101 The design format within this standard is based upon a limit
state and partial safety factor methodology, also called Load and
Resistance Factor Design format (LRFD). The load and resistance
factors depend on the safety class, which characterizes the consequences
of failure.Sec.2
C 200 Categorisation of fluidsSec.2 C
201 Fluids to be transported by the pipeline system shall be categorised
according to their hazard potential as given by Table 2-1.Sec.2 C | Table 2-1 Classification
of fluids | | Category | Description | | A | Typical non-flammable water-based fluids. | | B | Flammable and/or toxic fluids which
are liquids at ambient temperature and atmospheric pressure conditions.
Typical examples are oil and petroleum products. Methanol is an
example of a flammable and toxic fluid. | | C | Non-flammable fluids which are non-toxic gases
at ambient temperature and atmospheric pressure conditions. Typical
examples are nitrogen, carbon dioxide, argon and air. | | D | Non-toxic, single-phase natural gas. | | E | Flammable and/or toxic fluids which
are gases at ambient temperature and atmospheric pressure conditions and
which are conveyed as gases and/or liquids. Typical examples
would be hydrogen, natural gas (not otherwise covered under category
D), ethane, ethylene, liquefied petroleum gas (such as propane and
butane), natural gas liquids, ammonia, and chlorine. |
Sec.2 C
202 Gases or liquids not specifically identified in Table 2-1 should
be classified in the category containing fluids most similar in
hazard potential to those quoted. If the fluid category is not clear,
the most hazardous category shall be assumed.Sec.2
C 300 Location classesSec.2 C
301 The pipeline system shall be classified into location classes
as defined in Table 2-2.Sec.2 C | Table 2-2 Classification
of location | | Location | Definition | | 1 | The area where no frequent human activity is
anticipated along the pipeline route. | | 2 | The part of the pipeline/riser in
the near platform (manned) area or in areas with frequent human activity.
The extent of location class 2 should be based on appropriate risk
analyses. If no such analyses are performed a minimum distance of
500 m shall be adopted. |
Sec.2
C 400 Safety classesSec.2 C
401 Pipeline design shall be based on potential failure consequence.
In this standard, this is implicit by the concept of safety class.
The safety class may vary for different phases and locations. The
safety classes are defined in Table 2-3.Sec.2 C | Table 2-3 Classification
of safety classes | | Safety class | Definition | | Low | Where failure implies low risk of human injury
and minor environmental and economic consequences.
This
is the usual classification for installation phase. | | Medium | For temporary conditions where failure implies
risk of human injury, significant environmental pollution or very
high economic or political consequences. This is the usual classification
for operation outside the platform area. | | High | For operating conditions where failure implies
high risk of human injury, significant environmental pollution or very
high economic or political consequences. This is the usual classification
during operation in location class 2. |
Sec.2 C
402 The partial safety factors related to the safety class are given
in Sec.5 C100.
Sec.2 C
403 For normal use, the safety classes in Table 2-4 apply:Sec.2 C | Table 2-4 Normal
classification of safety classes* | | Phase | Fluid Category A,
C | Fluid Category B,
D and E | | Location Class | Location Class | | | 1 | 2 | 1 | 2 | | Temporary1,2 | Low | Low | - | - | | Operational | Low | Medium3 | Medium | High |
- Installation until pre-commissioning
(temporary phase) will normally be classified as safety class Low.
- For safety classification of temporary phases after
commissioning, special consideration shall be made to the consequences
of failure, i.e. giving a higher safety class than Low.
- Risers during normal operation will normally be classified
as safety class High.
*Other classifications may
exist depending on the conditions and criticality of failure the
pipeline. For pipelines where some consequences are more severe
than normal, i.e. when the table above does not apply, the selection
of a higher safety class shall also consider the implication, on the
total gained safety. If the total safety increase is marginal, the
selection of a higher safety class may not be justified.Sec.2
C 500 Reliability analysisSec.2 C
501 As an alternative to the LRFD format specified and used in
this standard, a recognised structural reliability analysis SRA)
based design method may be applied provided that:| — | the method complies with DNV
Classification Note no. 30.6 'Structural
reliability analysis of marine structures' | | — | the approach is demonstrated to provide adequate safety for
familiar cases, as indicated by this standard. |
Guidance note:
In particular, this implies that reliability based limit state
design shall not be used to replace the pressure containment criterion
in Sec.5 with the exception of accidental loads.---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
Sec.2 C
502 Suitably competent and qualified personnel shall perform the
structural reliability analysis, and extension into new areas of application
shall be supported by technical verification.
Sec.2 C
503 As far as possible, nominal target failure probability levels
shall be calibrated against identical or similar pipeline designs
that are known to have adequate safety on the basis of this standard.
If this is not feasible, the nominal target failure probability
level shall be based on the failure type and safety class as given
in Table 2-5.Sec.2 C | Table 2-5 Nominal
failure probabilities vs. safety classes | | Limit States | Probability
Bases | Safety Classes | Low | Medium | High | Very High4) | SLS | Annual per Pipeline1) | 10-2 | 10-3 | 10-3 | 10-4 | | ULS 2) | Annual per Pipeline1) | 10-3 | 10-4 | 10-5 | 10-6 | | FLS | Annual per Pipeline3) | | ALS | Annual per Pipeline | | - | Pressure containment | 10-4-10-5 | 10-5-10-6 | 10-6-10-7 | 10-7-10-8 | - Or the time period of the temporary phase.
- The failure probability for the bursting (pressure containment)
shall be an order of magnitude lower than the general ULS criterion
given in the Table, in accordance with industry practice and reflected
by the ISO requirements.
- The failure probability will effectively be governed
by the last year in operation or prior to inspection depending on
the adopted inspection philosophy.
- See Appendix F Table F-2.
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