New edition of the DNV pipeline standard, DNV-ST-F101

Dear colleagues,

I am happy to announce that on the 25th of August, a new edition of our offshore standard for submarine pipeline systems was released now with the acronym DNV-ST-F101 due to the recent re-branding of DNV.

It is the tenth edition of the pipeline standard since the first 45 years ago. In 2000 it was converted from DNV rules to its current “standard” format and it has since then on average been revised every fourth year. The 2021 revision has been on industry hearing and more than 400 comments from 15 companies around the world were received. This may sound like a lot of comments but the number of comments has actually declined for every new edition from 7000 in 2000! The reduced number of comments hopefully reflect that it is in general more mature and that there are less changes between the newer editions, which may be a relief to several of you! This reduction in comments has happened even though the numbers of users has likely increased!

The 2000 edition inherited the safety philosophy with limit state principles and target failure probabilities developed in the Joint Industry Project (JIP) SUPERB in the 1990’s. As part of the SUPERB JIP, some criteria were made more conservative and others less conservative with the objective to provide an overall more uniform safety level across the range of applicable parameters. This safety philosophy foundation has proven to be a good basis also for more recent development of other specific pipeline assessments which our 17 related Recommended Practices show.

New editions of the standard are normally triggered by including new knowledge from performed JIP’s, experience feed-back from the industry or DNV internal work. An important feed-back arena to the industry is the DNV Pipeline Committee, now representing close to 30 companies, that meet twice a year. This new edition of the standard includes all of the three above initiators and truly shows their importance for development of modern design codes.

The new edition includes strength contribution from the Corrosion Resistant Alloy (CRA) for lined and clad pipes in some limit states from the lined and clad JIP performed over the last decade. This has the highest impact on the pressure containment capacity where the strength of the liner or clad contribute to reduced wall thickness.?Strength contribution from CRA is also included in some other limit states to allow higher utilization of the pipeline.

With the challenges in extreme deep water with high pressures as relevant outside Brazil and Africa, extremely thick pipes have been required in order to enable these field developments. Studies performed by the European Pipeline Research Group (EPRG) as well as the DNV collapse JIP, have shown that the previous lower diameter to thickness ratio limit in the local buckling formulations of 15 could be waived. Thus, enabling this type of design without comprehensive documentation requirements required once stepping outside the boundaries of the standard,

Some other changes in the new standard, with less influence but still important are:

• Changed categorization of CO2 from C to E in line with last revision of ISO 13623. This is in line with the recommendation in the previous edition of the standard. The standard is also supported by the recently updated DNV-RP-F104 for design and operation of CO2 pipelines.
• It has been highlighted that it is required to determine relevant pressure containment safety factors for not fully rated pipelines, i.e. pipelines that during an accidental event may experience a pressure in excess of incidental pressure. This is likely to happen when instrumented pressure controls fails and are linked to their Safety Integrity Level (SIL) and probability for the scenario to occur. Further guidance on this is anticipated to be released in next edition of the standard based on an on-going JIP.
• Some relaxation on welding qualification requirements.
• Refined calculation of restrained force of multiple pipes developed internally are provided
• Portland composite cement may also be used as weight coating for certain conditions

And some more editorial changes:

• Section one has been partly re-structured in line with the general principles for standards in DNV.
• Definitions that previously appear throughout the document have now been gathered in section one.
• A new section including the relevant bibliographies has been included.

An example of feed-back from the pipeline committee is the confusion of the term de-commissioning and abandonment where abandonment implies taking a pipeline permanently out of operation, in line with the definition in ISO 13623. Many companies use the term de-commissioning instead of abandonment. Based on short and intense discussion in the pipeline committee, the terms have not been re-defined but the potential confusion has been highlighted in the definitions.

I will also ask you to explore the possibilities that is in our “rules and standards explorer”, that you get access to by subscription. You can put bookmarks and notes in your on-line version. Check it out!

I have always been proud of our pipeline standard but also recognizing that it can always be further improved. Luckily, I would say, such that we also have future challenges to enjoy! I am convinced of that the safety philosophy in the standard is very well suited also for future challenges. One such example is the recently launched H2Pipe JIP with more than 25 industry partners and 4 legislators that aims at developing the world's first recommended practice for transport of hydrogen gas in existing and new offshore pipelines as a supplement to this standard.

I do also believe that the future will bring the so called “Design by analyses” where both load effects and capacities are determined by detailed FE-analyses which, by the way, I also expect will remove the difference between load controlled and displacement controlled condition. To establish a solid safety philosophy for "Design by analyses" will then be a key challenge!

If you have proposals on modifications or technology development ideas it is easier to get this reflected in the standard if you contact me. The hearing process is not intended to include new aspects, only modifications on what is in the document that is issued for hearing. DNV is planning to develop a more transparent plan of future modifications on all our pipeline codes, where proposals from hearing process can be included. This plan will assist us also in initiating new JIP’s of similar research work for such developments.

I have been the main responsible for the last seven editions of our xxxx-yy-F101 as well as the 1996 Rules, with solid support from colleagues covering their specialist areas. This edition of the standard is likely the last revision where I am in charge of before retirement a few years into the future. But have confidence in us, Sigbj?rn R?neid has assisted me in this work since 2007 and he is still young.

?

Leif