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DNV-OSS-304 Risk Based Verification of Offshore Structures
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SECTION 1
General Sec.1
A. General
Sec.1
A 100 Introduction
Sec.1 A
101 This DNV Offshore Service Specification (DNV-OSS 304) describes
DNV services for risk based verification of structures. For structures
subject to DNV classification services see DNV-OSS-101, 102 or 103.
Sec.1 A
102 This specification falls under the top level document DNV-OSS-300
Risk Based verification.Guidance note:
The latest revision of all DNV documents may be found in the publications
list in the DNV web site www.dnv.com.---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
Sec.1
A 200 Objectives
Sec.1 A
201 The objectives of this specification are:
| — | to describe a method to define
a verification scope |
| — | give guidance on how to select the level of involvement
of the verifier |
| — | give guidance on how to establish a verification plan. |
Sec.1
A 300 Scope of application
Sec.1 A
301 This specification is intended to be used for specifying verification
services for total or part of the structure for offshore installations
for all or selected project phases. The document is developed for
structures to both fixed and floating platforms, but is also applicable
for onshore structures if found relevant.
Sec.1 A
302 The verification may be done against DNV Offshore Standards
or other recognized structural standards when applicable. Sec.1
A 400 Structure of this document
| — | Section
1 explains the overall principles of risk based verification. |
| — | Section 2 describes
the activities for each project and the various project phases. |
| — | Appendix
A gives guidance to assist in the selection
of verification level. |
| — | Appendix B gives
examples of verification scope of work for certification of fixed
platforms. |
| — | Appendix C gives
example verification documents and describes the documents issued
during and as a result of the verification process. The use of quality
management systems is addressed here also. |
Sec.1
B. Risk Based Verification
Sec.1
B 100 Elements of the service
Sec.1 B
101 The risk based verification concept is described in DNV-OSS-300
and shown in Figure 1.
Sec.1 B
102 The Verification Plan is the pivot element, with the Asset
Specification, Risk Assessment and Definition of Involvement Level
as input and the Verification Execution being the implementation
process.
Fig. 1 The DNV risk based verification flow chart
Sec.1
B 200 Asset specification (verification
object)
Sec.1 B
201 The structure subject to verification need to be defined accurately
and shall be agreed with the client. Definition of the verification
object is usually made by reference to structural drawings. A list
of drawings including revision number will be the main body of the
specification.
Sec.1 B
202 In cases where the verification is limited to parts of what is
shown on the referred drawings a precise description of which parts
that are subjected to verification shall be given. Guidance note:
The verification can be limited to e.g. the part of the structure
that contribute to the global strength (main structure) or where
failure will imply loss of life, major pollution or major business
risk.---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
Sec.1 B
203 The definition of verification object shall include accurate
description of the design conditions that is covered by the service.
Sec.1 B
204 The objective of the verification shall be formulated as part
of the description of the verification object.
Sec.1 B
205 The acceptance criteria to be applied during the verification
shall be stated as part of the definition of the verification object. Guidance note:
The acceptance criteria are for verification of structures
usually defined by reference to structural standards and specifications.---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
Sec.1
B 300 Risk assessment
Sec.1 B
301 Before making the verification plan the various risk for the
structure subjected to verification shall be assessed.
Sec.1 B
302 The risk assessment may be given by the client, developed
in cooperation with DNV or made solely by DNV.
Sec.1 B
303 The risk assessment shall identify and clearly specify the various
risk elements for the structure. The risk assessment is usually
done by a systematic review of the structure for all phases in order
to identify the consequences and the probabilities of failures e.g.
by use of HAZID techniques.
Sec.1 B
304 The risk assessment should be based on experience from similar
structures and by giving due consideration to the requirements imposed
on the structure in order to maintain the main safety functions
of the installation.
Sec.1 B
305 The relevance of the experience of the designer and the fabricator
will influence the probability of errors that may lead to structural
failures. In cases where the experience of the designer is unknown
technical audits can be used. In order to assess the relevance of
the fabricator's experience, technical audits or the use of
assessment techniques like MPQA may be used.
Sec.1 B
306 The risk assessment may be based upon results from Quantitative
Risk Analysis.
Sec.1 B
307 The initial risk assessment may need to be updated as the verification
work progresses and reveals that the judgements originally made
prove to be inaccurate. Sec.1
B 400 Definition of verification involvement
Sec.1 B
401 Based on the overall risk level for the structure the client should
decide on the amount of resources to be used for the verification
work by selecting among three different levels of verification.
Guidance for selecting the levels of verification is given in Appendix A.Sec.1
C. Defining a Verification Plan
Sec.1
C 100 Risk based verification planning
Sec.1 C
101 Based on the Asset Specification, the Risk Assessment and
the Definition of the Verification Involvement, a verification plan
shall be developed.
Sec.1 C
102 The verification plan shall describe the method to be applied
for the different verification activities.
Sec.1 C
103 The verification plan shall be communicated to the client
before verification work commences. Sec.1
D. DNV Statements and Certificates
Sec.1
D 100 General on verification
Sec.1 D
101 Verification describes the individual activities undertaken
by DNV at the various stages of design, construction and operation
of the facility. The scope of the verification plan is ultimately
determined by the Client.
Sec.1 D
102 A statement of Compliance may be issued by DNV to confirm
that a specified asset complies with the acceptance criteria according
to the agreed scope of work. See Appendix C for examples.Sec.1
D 200 General on certification
Sec.1 D
201 Certification describes the totality of verification activities
leading up to the issuance of a Certificate of Conformity. The scope
of work and verification plan, called a Certification Plan, is set
by DNV. All design and construction aspects, related to the structural
integrity, must be covered by the Certification Plan. See Appendix
C for examples.Sec.1
E. Definitions / Abbreviations
Sec.1
E 100 General
Sec.1 E
101 Relevant definitions in ISO 10418 (API RP 14C) also apply
to this OSS. Sec.1
E 200 Abbreviations
| ALS | Accidental Limit State |
| API | American Petroleum Institute |
| DNV | Det Norske Veritas |
| FE | Finite Element Analysis |
| FLS | Fatigue Limit State |
| HAZID | Hazard Identification |
| HAZOP | Hazard and Operability Review |
| OS | DNV Offshore Standard |
| OSS | DNV Offshore Service Specification |
| MPQA | Method and Product Quality Assessment |
| MPQT | Manufacturing Procedure Qualification Test |
| MPS | Manufacturing Procedure Specification |
| NDT | Non-destructive testing |
| QRA | Quantitative Risk Analysis |
| RP | Recommended Practice |
| SCF | Stress Concentration Factor |
| SHE | Safety, Health, Environment |
| ULS | Ultimate Limit State |
| VIV | Vortex Induced Vibration |
| WSD | Working Stress Design |
| WPS | Welding Procedure Specifications |
| WPQR | Welding Procedure Qualification Record |
Sec.1
E 300 Verbal forms
Sec.1 E
301 "Shall":
Indicates requirements strictly to be followed in order to conform
to this OSS and from which no deviation is permitted.
Sec.1 E
302 "Should":
Indicates that among several possibilities, one is recommended as
particularly suitable, without mentioning or excluding others, or
that a certain course of action is preferred but not necessarily
required. Other possibilities may be applied subject to agreement.
Sec.1 E
303 "May":
Verbal form used to indicate a course of action permissible within
the limits of the OSS.Sec.1
E 400 Definitions
Sec.1 E
401 Client: DNV's
contractual partner. It may be the Purchaser, the Owner or the Contractor.
Sec.1 E
402 Certificate of conformity:
A document signed by a qualified party affirming that, at the time
of assessment, the product or service met the stated requirements.
Sec.1 E
403 Construction phase:
All phases during construction, including manufacture, fabrication,
installation, testing and commissioning, up until the installation
or system is safe and operable for intended use. In relation to
fixed structures, this includes on-shore fabrication, lifting during
fabrication, load out and transportation on barge assembly, installation,
rectification.
Sec.1 E
404 Design: All related
engineering to design the fixed structure as well items related
to materials.
Sec.1 E
405 Design phase: An initial
phase that takes a systematic approach to the production of specifications,
drawings and other documents to ensure that the structure meets
specified requirements (including design reviews to ensure that
design output is verified against design input requirements).
Sec.1 E
406 Fabrication: Activities
related to the assembly of objects with a defined purpose. In relation
to fixed structures, fabrication typically refers to the process
of assembly or transformation of e.g. plates, profiles and tubulars
into a fixed structure.
Sec.1 E
407 Hazard: A deviation
(departure from the design and operating intention) which could
cause damage, injury or other form of loss (Chemical Industries
Association HAZOP Guide).
Sec.1 E
408 HAZID: (HAZard Identification):
A technique for the identification of all significant hazards associated
with the particular activity under consideration.
Sec.1 E
409 HAZOP: The application
of a formal systematic critical examination to the process and engineering
intentions of new or existing facilities to assess the hazard potential
of mal-operation or mal-function of individual items of equipment
and their consequential effects on the facility as a whole (Chemical Industries
Association HAZOP Guide).
Sec.1 E
410 Installation (activity):
The operations related to installing the equipment or structure,
e.g. marine operations related to placing equipment on seabed, tie-in,
piling of structure etc., including final testing and preparation
for operation.
Sec.1 E
411 Manufacture: Making
of articles or materials, often in large volumes. In relation to
process facilities, this typically refers to activities for the
production of various components under contracts from one or more
Contractor or Supplier.
Sec.1 E
412 MPQA: Manufacturer Product Quality
Assessment A rating system developed by DNV, which measures
the Client's capability to control product quality or to
benchmark processes enabling:| — | assessment of the capability
levels of suppliers of products or potential partners |
| — | choosing the best supplier for products and services |
| — | MPQA may be used as a supplement to confirming the Client's
quality management system and in Risk Assessment processes. |
Sec.1 E
413 Operations (phase):
The phase when the process facilities are being used for the purpose
for which it was designed.
Sec.1 E
414 Risk: The qualitative
or quantitative likelihood of an accident or unplanned event occurring,
considered in conjunction with the potential consequences of such
a failure. In quantitative terms, risk is the quantified probability
of a defined failure mode times its quantified consequence.
Sec.1 E
415 Risk Reduction Measures:
Those measures taken to reduce the risks to the operation of process
facilities and to the health and safety of personnel associated
with it or in its vicinity by:| — | reduction in the probability
of failure |
| — | mitigation of the consequences of failure. |
Guidance note:
The usual order of preference of risk reduction measures is:- Inherent Safety
- Prevention
- Detection
- Control
- Mitigation
- Emergency Response
---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
Sec.1 E
416 Safety Objectives:
The safety goals for the design, construction, installation operation
and abandonment the fixed offshore structure including acceptance
criteria for the level of risk acceptable to the Owner.
Sec.1 E
417 Statement of Compliance:
A statement or report signed by a qualified party affirming that,
at the time of assessment, the defined facility, phase, or collection
of activities, met the requirements stated by the Owner.
Sec.1 E
418 Verification: An examination
to confirm that an activity, a product or a service is in accordance
with specified requirements.Guidance note:
The examination shall be based on information, which can be proved
true, based on facts obtained through observation, measurement,
test or other means.
ISO 8402: 1994: Verification:
Confirmation by examination and provision of objective evidence
that specified requirements has been fulfilled.---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
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