New revision of DNV’s Pipeline standard is released

DNV issued its first ‘DNV Submarine Pipeline Rules’, the first code specifically for offshore use, back in 1976. “A number of updates have been released since then. Now, eight years after the previous update, the DNV-OS-F101 Submarine Pipeline Standard provides upgrades in four areas,” explains Leif Collberg, DNV Energy’s project manager and chief pipeline specialist.

“The revised Submarine Pipeline Standard complies now with the new ISO 3183 on line pipe material, with additional and modified requirements. This is the only pipeline standard in the world in compliance with ISO 13623 on pipeline design. The DNV standard also has increased focus on pipeline integrity during the operational phase. Further, the document is easier to follow and gives improved guidance and interpretations compared with the previous revision,” explains Leif Collberg.

1) ISO harmonisation
The main trigger for this revision was the newly revised ISO 3183, the material standard for C-Mn steel line pipe. DNV wants to harmonise its standards with the ISO codes, and DNV-OS-F101 has mainly been harmonised with two ISO codes: ISO 3183 (material) and ISO 13623 (design). The major achievement of the new revision of ISO 3183 is that it constitutes a merger between the old revision and API 5L. Hence, hopefully the industry may now use the same standard for line pipe in the US and the rest of the world.

DNV has chosen to provide a self-contained standard instead of only providing additional requirements to ISO. This decision was made after significant industry feedback showed that this was the best way forward.

The ISO requirements are repeated, with any additional or modified requirements clearly marked. DNV's intention is therefore to get the best out of two worlds; in compliance with ISO but still self-contained. This part has included revision of the welding and Non Destructive Testing (NDT) requirements. In total, 15 companies supported this update of the material section.

In addition to the line pipe section, the component section has been updated to reflect new ISO standards. A list of other relevant standards, although not compulsory, has been included.

DNV’s intention is for this document to now stipulate most of the additional requirements that purchasers normally specify regarding ISO/API.

2) Requirements for an integrity management system
The second reason for the update was to improve the requirements regarding the in-service phase. Here also, the industry made a solid contribution. “We have changed from a reactive to a proactive focus, and have introduced new requirements for an integrity management system,” explains Leif Collberg.

Another important related aspect of safe operation is the documentation requirements and the transition or hand-over from the design phase This has been emphasised by a separate section on documentation.

3) Improved document structure
The third and last major incentive for the update was to generally improve the document structure. The pipeline life cycle is subdivided into Concept and Business development, Design, Construction, Operation and Abandonment. All the standard's sections now refer directly to one of these phases and some of the contents have been moved to fit in with this structure. In particular, a new section on ‘Design – materials engineering’ has been introduced, with design phase requirements relating to material selection, corrosion, sour service, Hydrogen Induced Stress Cracking (HISC), etc.

4) Minor design changes
Only minor modifications have been made on the design side. Most of these changes are interpretations of what was there before and do not alter the requirements. One issue, however, is pressure definitions, and the slightly modified criterion will clarify the requirements regarding the pressure protection system with respect to, for example HIPPS.

The pipeline standard history
DNV issued its first “DNV Submarine Pipeline Rules”, the first code specifically for offshore use, back in 1976. This was updated in 1981 and has been adopted world wide.

In 1996, a third revision was issued. This was a completely re-written code, adopting the more modern and generally applicable limit-state-based design with calibrated safety factors instead of the old stress-based design. The 1996 version was based on a large Joint Industry Project called SUPERB, which collected the necessary basic materials.

In 1999, DNV changed the structure of its offshore-related documents from Rules to Offshore Service Specifications, Offshore Standards and Recommended Practices. An Offshore Standard only states technical requirements and makes no references to DNV services, etc, as the old Rules did. DNV-OS-F101, in its second revision of the limit-state-based format, was one of the first Rules to be converted to this Offshore Standard format.