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Confirming that an offshore unit meets applicable requirements at all times is key to ensuring safety at sea. DNV develops a tailor-made In-service Inspection Program (IIP) for each mobile offshore unit, and carries out regular surveys to ensure that the unit is maintained at a satisfactory level. Reported damages, such as cracks, serious corrosion, indentations, etc., are logged in a central damage database. The results from the database are used to provide owners and operators of offshore units continuous improvement of our services.

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Purpose

Verify that the classed unit continues to meet the original safety standard obtained at newbuild.

Benefits

The combination of DNV’s tailor-made In-service Inspection Program (IIP) and regular surveys ensures that units are maintained at a satisfactory level, thereby safeguarding life at seas. Reported damages, such as cracks, serious corrosion, indentations, etc., are logged in a central damage database. Results from the database provide owners and operators of offshore units continuous improvement of our services.

Our approach

Classification in the operation phase implies independent surveys to verify that the governing technical requirements associated with the actual class of the unit are maintained at a satisfactory level. The scope of a periodical survey is aligned with the level of significance for the systems and objects surveyed, based on risk and consequence assessments combined with relevant experience. DNV develops a tailor-made In-service Inspection Program (IIP) for the hull structure of each mobile offshore unit. This highlights areas and details to be surveyed by visual and close visual inspection, as well as NDT, and addresses:

  • Frequency of the various types of inspection
  • Relevant data from previous surveys
  • Experience from similar structures.

The IIPs are based on design calculations as well as relevant information from the fabrication phase. In addition, we apply qualitative consequence considerations in relation to possible failure modes to determine the extent and frequency of inspection.

Reported damages, such as cracks, serious corrosion, indentations, etc., are logged in a central damage database, which currently holds more than 4,000 entries. The data is then balanced against other sources of information and can contribute to:

  • Trend analysis
  • Highlighting typical defects
  • Initiation of safety alerts and corrective actions
  • Modification of survey frequency and extent, as defined in the IIP
  • Improvement of classification rules.

Survey information, inspection program and relevant check-lists are made available through the database in the Nauticus Production System, which is available to DNV surveyors world-wide and facilitates reporting and follow-up. Survey information is readily available to owners via the web-based DNV Exchange system, which is a client-operated class management tool that provides secure access to class status, survey, certificates and DNV reference information through the World Wide Web. DNV has survey stations in more than 100 countries and may perform surveys at owners’ request on short notice anywhere. A formal qualification scheme applies to all DNV technical personnel and ensures that a surveyor has appropriate competence and experience for the survey to be performed.

DNV has adapted to modern maintenance techniques by allowing for alternative survey arrangements. Examples of the most common alternatives to traditional ‘open-up inspection techniques’:

  • Continuous surveys on a rotational basis according to an agreed and accepted sequence
  • Survey arrangements based on owner’s approved planned inspection and/or maintenance systems (PMS). Such arrangements may be accepted for mechanical, electrical and instrumentation systems and components. When implemented, the unit’s own PMS will be taken as basis for class surveys, provided that the owner’s PMS is satisfactorily implemented.