OS-C501

Offshore Standard DNV-OS-C501, November 2013
Sec.12 Operation, maintenance, reassessment, repair – Page 174
SECTION 12 OPERATION, MAINTENANCE, REASSESSMENT, REPAIR
1 General
1.1 Objective
1.1.1 The objective of this section is to provide requirements for operation and in-service inspections. This
section also provides general guidance on structural integrity assessment of composite components to
demonstrate fitness for purpose in case deviations from design appear during operation.
2 Inspection
2.1 General
2.1.1 An inspection philosophy for the component should be established. The philosophy shall at least contain:
— the items to be inspected, arranged according to their order of importance
— the parameters to look for and or measure, e.g.
cracks, delaminations, impact damages, overheating (or damages from local burning), visible overloading
(bending, unintended use), discoloration
— methods of inspection to be applied for each item
— inspection frequency
— acceptance criteria
— reporting routines.
2.1.2 In case of findings at the inspections, a plan should be worked out listing suggested actions to be taken,
depending on the type of findings. The plan may be included in the inspection philosophy.
2.1.3 Inspection procedures shall be defined for:
— manufacturing control
— detection of damage due to accidental loads or overloads in all phases
— detection of damage due to unexpected high degradation of long term properties in all phases.
2.1.4 Inspection shall be linked to possible failure modes and mechanisms identified in the design.
2.2 Inspection methods
2.2.1 Available inspection methods can often not detect all critical failure mechanisms. However, the methods
may detect preceding failure mechanisms. A link between detectable failure mechanisms and critical failure
mechanisms shall be established.
2.2.2 The reliability and functionality of all inspection methods should be documented.
2.2.3 In many cases a complete inspection programme cannot be developed due to the limited capabilities of
available NDE equipment. In that case the following alternatives in [2.2.4] to [2.2.8] may be used.
2.2.4 Inspection of components during or right after manufacturing may be replaced by well documented
production control.
2.2.5 Inspection to detect damage due to accidental loads or overloads may be compensated for by monitoring
the loads and comparing them to the design loads.
2.2.6 Effect of higher degradation than expected can be compensated for by using the failure type brittle in the
long term analysis. If this method is used the component must be replaced or re-evaluated after all overloads
or other events exceeding the design requirements. This approach shall be agreed upon with the customer.
2.2.7 If the failure mechanisms are not fully understood, or competing failure mechanism are present and one
is uncertain about their sequence, inspection is required.
2.2.8 Inspection frequencies and acceptance criteria should be determined for each project.
3 Reassessment
3.1 General
3.1.1 Reassessment of composite components shall be based on the same criteria as designing and building a
new component.
3.1.2 Old calculations and test data may be used as far as applicable.
DET NORSKE VERITAS AS