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Sec.2: Service Overview [Table of Contents] App.B: Example Verification Scope for Certification of Fixed Offshore Structures

DNV-OSS-304 Risk Based Verification of Offshore Structures

[-] App.A: Selection of Verification Level

APPENDIX A
Selection of Verification Level

App.A
A. General

App.A
A 100   General principles

App.A A
101   The purpose of selecting a verification level is to direct greatest effort at those elements of the asset where the risk is highest and whose failure or reduced performance will have the most significant impact on the project objective and goals, e.g.:
—safety risks
—environmental risks
—economic or business risks.


App.A A
102   The selection of the level of structural verification should be made by assessment of the risk of structural failures. Risk is a function of both consequence of a failure and the probability of a failure occurring. Both consequence and probability need to be considered when selecting the verification level.

App.A A
103   The consequences of structural failure should be related to the overall risk analysis of the development with regards to the importance of the structures for the main safety functions of the total installation. Consequences from structural failures on the business risk like impact on schedule and cost should also be considered.

App.A A
104   The probability of failure is related to the complexity of the design, fabrication and installation of the structure.

App.A A
105   When selecting the verification level it should also be considered the cost of verification in relation to the possible reduction of risk.

App.A
B. Verification Levels for Design

App.A
B 100   Evaluation of consequences

App.A B
101   The consequence of a structural failure should be evaluated on the basis of the safety objectives for the project or of the company.

App.A B
102   The consequences of structural failures should be evaluated by consideration of the factors listed below among others:
—direct consequences for the safety of personnel
—indirect consequences for personnel or danger to the environment due to loss of support for process equipment or piping
—loss of structural support that may jeopardize safety functions as escape ways, fire walls etc.
—impact on project schedule due to redesign or rework.

App.A
B 200   Evaluation of probability

App.A B
201   The evaluation of probability of failure that is relevant for determination of the appropriate verification level should be based upon consideration of the following factors:
—status of implementation of quality management systems of the contractors
—degree of technical innovation in the structure
—new use of well known design solutions
—the number of contractors involved
—experience of the contractors in carrying out the work
—tightness of the schedule
—level of complexity of the analyses involved
—confidence in load determinations
—degree of structural optimisation.

App.A
B 300   Selection of verification level for design

App.A B
301   Low Verification Level will apply to well known types of structures that are designed by experienced designer and low or moderate consequences of failure.

App.A B
302   High Verification Level should be selected for innovative designs, inexperienced designer or high consequences of failure.

App.A B
303   Structures not categorised to be verified according to High or Low Verification Level should be verified according to Medium Verification Level.

App.A
C. Verification Levels for Fabrication

App.A
C 100   Evaluation of consequences

App.A C
101   The consequence of a structural failure as a result of faulty fabrication should be evaluated on the basis of the safety objectives for the project or of the company.

App.A C
102   The verification that are selected for fabrication should also consider the consequences identified for verification of design.

App.A C
103   The consequences of structural failures should be evaluated by consideration of the factors listed below among others:
—direct consequences for the safety of personnel
—indirect consequences for personnel or danger to the environment due to loss of support for process equipment or piping
—loss of structural support that may jeopardize safety functions as escape ways, fire walls etc.
—impact on cost and schedule from repair of fabrication faults
—impact on project schedule due to redesign or rework.

App.A
C 200   Evaluation of probability

App.A C
201   The evaluation of probability of failure that is relevant for determination of the appropriate verification level should be based upon consideration of the following factors:
—the contractors experience with the type of structure
—quality management systems of the contractors
—degree of technical innovation in the structure
—new use of well known design solutions
—sensitivity of the structure to fabrication faults. e.g. exposure to fatigue loading
—degree of optimization of the structure
—number of and experience of subcontractors
—the complexity of interfaces.

App.A
C 300   Selection of verification level for fabrication

App.A C
301   The verification level selected for fabrication may differ from what is selected for design.

App.A C
302   Low Verification Level will apply to well known type of structures that are fabricated by experienced fabricators and with low or moderate consequences of failure.

App.A C
303   High Verification Level should be selected for innovative design solutions, inexperienced fabricator or high consequences of failure.

App.A C
304   Structures not categorised to be verified according to High or Low Verification Level should be verified according to Medium Verification Level.
Sec.2: Service Overview [Table of Contents] App.B: Example Verification Scope for Certification of Fixed Offshore Structures