RDNV-RP-F113: two decades of subsea pipeline repair

In the latest episode of the World Pipelines Podcast, Rustem Khalikhan, Junior Project Engineer at DNV, talks about the enduring importance of DNV-RP-F113 and its role in guiding safe, effective subsea pipeline repair.

 

We discuss:

• Why the Recommended Practice was developed and the industry challenges it addresses.
• The role of engineering judgement alongside established standards.
• Why quality assurance and documentation are critical to successful repairs.
• How existing repair frameworks are being considered for emerging CO₂ and hydrogen infrastructure.
• The influence of digitisation on the future of pipeline repair.

 Whether you're involved in pipeline integrity, offshore engineering, or subsea operations, this episode offers valuable insight into the standards that help keep critical infrastructure operating safely and reliably.

Creators and Guests

Host

Elizabeth Corner

Elizabeth leads the editorial teams at World Pipelines, commissioning articles and features, and representing the magazine at industry events.

Guest

Rustem Khalikhan

Junior Project Engineer at DNV

What is World Pipelines Podcast?

The World Pipelines podcast, with Elizabeth Corner, is a podcast that connects and unites pipeline professionals to learn about issues affecting the midstream oil and gas industry.

Elizabeth Corner: 00:01

Hello, and welcome back to the World Pipelines Podcast. With me for this episode is Rustem Khalikhan , junior project engineer at DNV, the global independent risk management and assurance provider. DNV primarily acts as a classification society for the maritime industry and as a technical adviser to the energy sector. Headquartered in Norway, DNV sets industry standards for safety, sustainability and quality and operates in over 100 countries. Rustem is based in Milan, Italy, and he is a civil and environmental engineer.

Elizabeth Corner: 00:38

He previously worked in academia and joined DNV three years ago as structural engineer in the verification team of the offshore, midstream, and downstream departments. Since then, he has worked on the structural verification of offshore assets as well as taking part in projects related to pipeline damage and fitness for purpose assessment and research on pipeline integrity management and pipeline repurposing. Now the starting point for our conversation today is DNV RPF113, a standard that has been in existence for nearly twenty years and one that has had quite an impact on subsea pipeline repair. World Pipelines helps oil and gas pipeline professionals stay informed about the midstream oil and gas sector, offering technical articles, regional briefings, project and contract news, and think pieces on pipelines all over the world. Register to receive a print or digital copy at worldpipelines.com and search World Pipelines on LinkedIn to join our community.

Elizabeth Corner: 01:54

So thank you for joining the Podcast for Stem.

Rustem Khalikhan: 01:57

Thank you. Very cheerful for us it's morning and I'm glad to be here.

Elizabeth Corner: 02:02

Now before we get into the detail of this standard, maybe you can set the scene for us. So what was the industry challenge that this particular recommended practice was originally trying to solve or trying to address?

Rustem Khalikhan: 02:16

Okay, so one of the key challenges faced by the offshore industry was that although pipelines were designed to very high reliability standards sometimes people may say too conservative but still there was no consistent industry framework for what should happen when a subsea pipeline was actually damaged. Repair systems existed but operators often approached preparedness and qualification and repair planning differently from one another. And historically subsea repair was still viewed as a contingency activity something that would hopefully never happen. The problem was that when damage did actually occur, decisions had to be made quickly and often under significant operational and obviously commercial pressure. The industry needed guidance not only on repair hardware but also on repair qualification, damage assessment and obviously the preparedness.

Rustem Khalikhan: 03:10

The RPF113 was developed to establish a common approach for designing, qualifying and implementing subsea repair systems. It transforms the repair from a reactive emergency response into a structured engineering discipline at the end of the day. Recognize that successful repair starts long before damage occurs through preparation, risk assessment and the qualification of the repair systems. Here it's also important not to forget that the repair system, the hardware or software, was commonly requested by insurance companies to withstand a strategic project like a transcontinental gas link, But it was not the case for subsea pipeline networks, particularly in very deep waters for which the request is actually relatively recent.

Elizabeth Corner: 03:56

And in terms of what RPF113 covers, whereabouts does it sit in the life cycle of a pipeline?

Rustem Khalikhan: 04:04

First it covers the qualification and application of subsea repair technologies and repair strategies for submarine pipelines. Technically it deals with the pipeline repair systems and fittings that include clamps, mechanical couplings, t branch connections, hot tappings and many more. Importantly it also covers the procedural requirements or recommendations So these are repair preparedness, selection of repair methods, manufacturing and testing requirements, as well as lifecycle management. The standard occupies the last quarter within the DNV's broader integrity management, so the repair intervention portion of the pipeline integrity management cycle. In this particular framework, it is not treated as an isolated activity, but as a part of a continuous process of risk assessment, inspection and monitoring, as well as integrity assessment and obviously mitigation and repair.

Rustem Khalikhan: 04:59

A key message at the end of the day of the RP-one hundred and thirteen is that the technological approach to repair should be considered from the very beginning and throughout the pipeline life cycle, not only when or after failure accuracy. And quite honestly I would like to point out even from several client inquiries this year that this message has been heard.

Elizabeth Corner: 05:21

Great. The average observer might think that standards are invisible. They might only notice that standards exist when something goes wrong. Do you think that the industry fully appreciates the role that standards play?

Rustem Khalikhan: 05:36

I have to admit that I don't really know if I can talk about the sentiments in the industry. In my humble opinion, people do tend to notice standards only either when something goes wrong or when the project constraints arise. So for example, if there is a requirement, direct requirement from the end user to follow a specific code and then designers do get into standard detail. At the same time I also see the standards, guidelines, recommended practices as a common engineering language. Standards help ensure that operators, contractors, manufacturers, certifying bodies, regulators are all working from the same technical basis or at least trying to do so.

Rustem Khalikhan: 06:18

So not to wander off, I cannot fully say if the industry does or does not appreciate the standards. What I can say is that there is a confidence when the industry uses them and then there is a general trend towards harmonization of these standards so that the standards are actually well put together. And without the codes and the RPs, every project at the end of day would have to rein when the wheel every time. Consequently, the methodology and acceptance criteria would differ, whereas in offshore projects involving many stakeholders in different countries consistency is crucial. The real value of the RPF113 in my opinion is not simply that it belongs to a complete, if I may, DNV standard ecosystem and defines how repair should be performed.

Rustem Khalikhan: 07:03

It creates confidence that repair systems will perform when they are needed often many years after being designed and qualified. And as my senior colleagues like to say at the end you cannot have a draft over repair technology, you actually need it to work.

Elizabeth Corner: 07:17

And these offshore projects we're talking about, what are the real world scenarios that we're dealing here? What typically goes wrong?

Rustem Khalikhan: 07:26

First, fortunately nothing grows catastrophically wrong. However, pipelines operate for decades in challenging environments and damage mechanisms do occur. Examples include dropped objects during a shore construction, dragged anchors, fishing gear, interaction, excessive free spanning, geo hazards that's a big advantage of landslides, seabed instability, turbidity currents, corrosion damage roughly one third of the cases, fatigue cracking and cold cracking like due to hydrogen for example. Here it is always about a specific case with its own context like external mechanical damage is more common in busy areas where you have deficient vessels for example, whereas repurposed hydrogen pipelines typically experience completely different sets of problems. One lesson that comes from all the fitness purposes assessments that I was involved in at least is that not every damage indication actually automatically requires a repair.

Rustem Khalikhan: 08:29

The key challenge is actually the determining of what the defect is, its exact location, its dimensions, the root cause so in case of an external interference again you also need the dimensions of the thing that did the damage so the anchor, the rock, whatever it is. Whether and how it compromises the structural integrity, whether operation can continue safely because at the end of this is the main topic there because you may have major damage where you can automatically you need the repair, minor damage when you do need it, but a lot of the cases fall in the middle ground where you don't really know. And lastly, whether monitoring is sufficient or whether immediate intervention is actually necessary.

Elizabeth Corner: 09:11

So it's an investigative process in that respect?

Rustem Khalikhan: 09:14

For sure.

Elizabeth Corner: 09:15

Okay, one thing then I would like to focus on is DNV's emphasis on method and philosophy. From what you're saying, is a method to this, it's not just a set of rules. How would you describe DNV's approach to design and repair?

Rustem Khalikhan: 09:32

To me, this philosophy, not even only in design and repair, but in general, the DNV philosophy lies in being fundamentally risk based and performance based so you really have to dig in into the probability side of that. And the goal is not simply to prescribe rules but to understand how a structure behaves under realistic loading conditions and then demonstrate sufficient reliability. At the end of the day, you can always go conservative. There's always this preference to be conservative. But typically, you would like a realistic assessment to save the costs without compromising on safety.

Rustem Khalikhan: 10:05

And the NVIS ecosystem of standards and guidelines and the general approach allows just that. The ecosystem may be seen in the case of iClient for example it may be seen throughout the pipeline framework so it's the standard F101 for design, F113 for repair, F116 for integrity management, plus numerous joint industry projects for more specific cases. The approach here relies heavily on quantifying uncertainties and engineering verification and the standards actually aim to provide robustness rather than simple compliance and that's particularly important for repays because as mentioned every damage scenario is unique and the standards therefore provides an engineering framework rather than a simple checklist.

Elizabeth Corner: 10:52

Now you mentioned this earlier I think. Do you ever hear criticism that standards like this are too conservative that they slow things down? And if so, what's your response to that?

Rustem Khalikhan: 11:03

Well, as a verification engineer, I do hear that conservatism claim quite often and sometimes even as a direct response to comments that I raise. My response would be related to this common language aspect that I mentioned before. So the standards may be seen as common language whereas industry shareholders may use, and given the difference between the shareholders in the energy sector there must be something that all the shareholders understand. So it's like the key to a code or the language. And I see probabilistic approach to failure and quantitative risk assessment that typically is the conservative part there as the keys that everybody has and has to understand as well.

Rustem Khalikhan: 11:42

Thus my response is quite simple: standards are there not to complicate one's life at the end of the day but to ensure safety based on probabilistic and quantitative methods. Conservativeness is often claimed when dealing with like in the case of repair it's claimed when dealing with diagnostic fakes when you're actually trying to understand what happened what to do about that. And I think it is important to distinguish between conservatism and robustness that I mentioned previously. In case of a subsea pipeline damage, where every case is unique, you may still try to classify the damage as I mentioned before: major damage, minor damage, and this middle ground that is quite often the case. An example may be external impact resulted in concrete way coating damage.

Rustem Khalikhan: 12:25

Okay, you know that. You do not know what happened inside. The pipe may be dented, may be bent and here during the diagnostic phase it is important to be robust since you are dealing in the uncertainty field. And yes, in this regard that's actually the case. Most safety factors exist because experience has shown where uncertainties exist.

Rustem Khalikhan: 12:45

In the context of this discussion subsea repair systems operate in environments where intervention is expensive and difficult and sometimes even impossible to override once installed. A repair that fails may require another major offshore campaign or even result in production shutdown. And so what sometimes appears conservative is often simply a method of managing the asset.

Elizabeth Corner: 13:09

I hope this next question isn't a silly one, but is there any point where engineering judgment sort of takes over from this standard or overrides this standard?

Rustem Khalikhan: 13:19

It's very important to distinguish between, again, judgment and critical thinking and the tool. At the end of the day a standard guides process but the interpretation of the results remains an engineering responsibility. And I think that in many ways standards create the foundation upon which sound engineering judgment can be exercised. A standard provides the framework but at the end of the day the qualification has to be judged by an engineer. Moreover, when we are talking about standards it's important that at the end of the day like RP-F11P is twenty years old so it had to stay up to date and you only can do that when you have the engineering judgment.

Rustem Khalikhan: 14:02

One of the cases is we have been witnessing the technology evolution. I don't know, last year I presented the paper, we actually talked about the evolution. 1960s was hyperbaric diving, nowadays we have remotely operating or unmanned vehicles employing some machine learning algorithm within them or even real time inspection methods and this has to be also replicated within the standards and in my opinion this can only be done when you do have the engineering judgment behind that you can actually understand what you may have and what you can do with that.

Elizabeth Corner: 14:39

How important are qualification documentation and quality assurance when it comes to getting those repairs right?

Rustem Khalikhan: 14:47

One may see that as bureaucracy I believe but to me they are absolutely fundamental at the end of the day Because a repair system like in this context a repair system has been designed tested and qualified but it may remain unused for years before deployed and actually hopefully it will never be deployed but it may remain unused for many years and when needed it must work exactly as intended. This is why the RPF113 places such a strong emphasis on qualification programs, manufacturing verification and traceability, testing, documentation and quality control. If something has not been properly documented, demonstrated and verified, confidence in its performance is reduced and RPF113 covers repair systems that are going to be needed in the case of an accident. You do not want your emergency parachute not to work if the time comes, you know. And quality assurance here actually transforms the design into a dependable repair solution.

Elizabeth Corner: 15:50

Lovely. Now we like to look ahead on this podcast. So if we're looking ahead at hydrogen or CO2 service, how well do existing frameworks like RPF113 translate to these newer use cases?

Rustem Khalikhan: 16:05

I actually like this one because just this year I was working on the repurposing for hydrogen pipelines and so I had to go through the framework itself. I think the underlying framework, not just the RPF113 but the whole framework that I mentioned previously, actually translates very well, especially given that they do not operate in a vacuum but are afraid of greater systems or standards and codes that are more or less harmonized. And so the process of risk is the processes of risk assessment, qualification, repair planning and integrity management as well remain largely the same. The challenge lies in the material specific interactions with the transported fluid. So like for hydrogen for example concerns include hydrogen embrittlement and crack growth rate and then also material compatibility due to differences in microstructure low versus high grade heat affected zones, while for CO2 systems impurities management and fracture propagation in dense space conditions are critical.

Rustem Khalikhan: 17:01

And I think that even there this framework works well because it actually is based on risk assessment and probabilities but even in addition to that the industry itself is already addressing these issues. For example through new guidance this year DNV has published the RP-one-two specifically for hydrogen pipelines plus there are currently the joint industry projects called CO2 safe pipe and H2 pipe GIPs and obviously these are being based on the existing framework. So first means that the existing framework allows that and second even if there is something it means that it allows actually staying up to date on all the fronts you know. So I think it does translate very well there.

Elizabeth Corner: 17:46

Great. It builds the framework on which those new standards come out of. And I wonder how the digital world influences how standards are developed or applied. Maybe it doesn't.

Rustem Khalikhan: 17:57

Well, they do. Because as I mentioned before, the technology itself has been developing quite fast and especially in the later decades I believe. And one big part of that is data itself. So one example in my opinion is the risk related assessment that rely on probability data. You want at the end of the day to have a more conscious diagnosis when you talk about subsea pipeline repair and thus typically the more data you have the lower the level of uncertainty is.

Rustem Khalikhan: 18:30

And modern inspection technologies generate vastly larger data sets than before and more even allow real time monitoring due to high resolution surveys, laser scanning, optic fiber and digital. And data is both better and more available and it's also digitalized. But even there you need actually to go through that because most of the standards still are being worked on right now do add this criteria that the level of certainty that you have in your data has to be high and thus this all this digital data at the end of the day needs to be analyzed quite well. And so for engineering, for engineers performing the fitness purpose assessment, improved inspection data and this faster assessment, reducing certainty and support more reliable conclusions. And if it is done in timely manner it's actually due to the fact that most of the data being digitalized.

Rustem Khalikhan: 19:24

And all this is and I believe will be further incorporated in the industry standards.

Elizabeth Corner: 19:29

Great. Now the August issue of World Pipelines includes an article from DNV on evolving sub repair methods, so readers can look out for that. To finish us up today, Rustem, are there mistakes or issues in pipeline repair that you feel that we should have solved by now, but they still come up?

Rustem Khalikhan: 19:48

Certainly, there is always a place where you can improve further. One example I think it's that engineers can perform some sophisticated calculations, but at the end of the day the conclusions are only as reliable as the inspection information that they are based on and the more information the better and even more so the more structured it is. The more flow it has the better you may see the marginal difference there. And the problem that I see nowadays too is the tendency to treat pipeline integrity as a periodic activity rather than a continuous process. And I believe that successful integrity management depends on good baseline data, consistent monitoring, timely assessment and repair preparedness before an event occurs.

Rustem Khalikhan: 20:34

And all that actually requires operators and everybody to treat the repair parts of the last quarter or the life cycle, at least in the RDNV framework, as something continues that has to be worked on repeatedly. And I'm not sure if it is 100% like that throughout the industry. But that's actually the ultimate central message of the RP in my opinion that repairs do not start when damage is discovered or found, they start years earlier through preparedness, technology qualification and obviously the engineering judgment, engineering foresight. Thank

Elizabeth Corner: 21:14

you so much for talking to the Podcast Rustem.

Rustem Khalikhan: 21:16

Well thank you for having me. I would also like to thank my senior colleague Roberto Bruski who gave me the opportunity as well.

Elizabeth Corner: 21:24

That was Rustem Khalikhan at DNV, offering his expertise on enduring pipeline subsea repair standards and how they continue to serve the industry today. Don't miss the August 2026 issue of World Pipelines for that article from DNV on evolving subsea repair methods. Thanks for listening to the World Pipelines Podcast. Subscribe for free, and please rate and review. World Pipelines helps oil and gas pipeline professionals stay informed about the midstream oil and gas sector, offering technical articles, regional briefings, project and contract news, and think pieces on pipelines all over the world.

Elizabeth Corner: 22:05

Register to receive a print or digital copy at worldpipelines.com and search World Pipelines on LinkedIn to join our community.