Unpiggable pipelines

A brief follow-up to my recent request for comment on the pipeline integrity issues that trouble Australian pipeline engineers.   My reason for asking was that I had been invited to co-chair a workshop at the JTM on pipeline integrity and wanted to make sure that I could raise any issues that were important in Australia.

Thanks to those who responded.  The comments largely confirmed my impression that in this country we have few serious concerns about the integrity of transmission pipelines transporting clean fluids.  There may be a different situation in production fields where a diverse range of issues may create problems (as pointed out by a couple of comments), but my main interest (unstated) was in transmission pipelines.

Nevertheless I think one emerging issue, both here and overseas, is the question of how to assess the integrity of pipelines that are not suitable for in-line inspection – the unpiggable lines.  We don’t have many of those, but they tend to be older lines (so the likelihood of failure may be higher) and in populated areas (so the consequences are higher too).  San Bruno comes to mind.

It appears that there are currently no effective methods for inspection beyond the first few metres of an unpiggable pipeline (other than digging it up for direct inspection, which is of course not possible if the line is installed under, say, a railway).  It will be interesting to watch the technical developments as both pipeline owners and inspection specialists increase their focus on this area.

(I haven’t forgotten that I’m supposed to be writing a series of posts on location classification – hope to resume soon.)

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5 Responses to Unpiggable pipelines

  1. Anonymous says:

    There are tethered pigs which can crawl out without a pig launcher and crawl back. They obviously still require access to an open pipeline. The pipeline isn’t producing for the entire duration of the inspection, and the length that can be inspected is limited. The NACE ICDA and ECDA assessments are a huge step forward in my view in providing legitimacy to assessment methods which haven’t been consistently applied in the past, and giving guidelines to the use of direct assessment via dig-ups. There are long range UT and other methods which haven’t had universal acceptance.
    Don’t forget that there have been low strength X70 issues overseas, and we can’t claim to be immune if we import linepipe from the same sources, which I suspect is happening.

    • petertuft says:

      Quite right that there is a variety of tools available, but if they need the pipeline to be taken out of service they are of no use for the unpiggable pipelines that I’m aware of around Australia.

      I’m uneasy about the whole direct assessment concept. The fact that it almost universally involves sampling only a limited portion of the pipeline means that it leaves a lot of questions unanswered. At risk of being provocative I have a feeling that direct assessment methods owe more to US regulatory compliance than to true integrity assessment. One the one hand ILI people worry about probability of detection, probability of failure, etc, for a pipeline that has been 100% inspected, yet direct assessment advocates appear (as I understand it) to give a clean bill of health to a pipeline on the basis of just a few samples. There is a disconnect here that bothers me.

      • Anonymous says:

        I couldn’t agree more. My point is that failures are happening at locations which were entirely obvious, yet limited assessment had occurred with any method. In some cases, one might have wanted ILI to verify the condition, but one didn’t need it to know one had a serious risk that needed further investigation. This applies to failures here and overseas. Some failures have been so mind-blowingly obvious that one suspects the people were asleep on the job. Despite the shortcomings, ICDA and ECDA allow the regulator to assess the operating company’s efforts. If an operating company hasn’t checked with ILI and hasn’t even completed an ICDA and ECDA study, how serious are they? I’m not suggesting they are any sort of replacement for an ILI tool.

  2. Anonymous says:

    Pipetel Technologies in North America (www.pipetelone.com) specializes in pigging of unpiggable pipelines. However, their technologies are limited to gas pipelines only. The inspection is done without shutting down or even reducing flow in pipelines.

  3. Good points. The term “unpiggable” is often misapplied due to limited awareness of current capability and technological improvements. Many historical design and operational constraints are being overcome quite easily today. For example, the Quest Integrity Group provides a metal-loss and deformation tool with 1.0d, bi-directional capabilities even launching by hand directly into nominal pipe while negotiation multiple diameter changes. Difficult, challenging, and/or problem pipelines do exist and understanding and defining specific constraints is key both in finding commercialized solutions and helping vendors provide solutions for the future.

    For those interested in the “unpiggable” please consider joining LinkedIn “Difficult and Unpiggable Pipeline” Group: http://www.linkedin.com/groups?home=&gid=3356338&trk=anet_ug_hm

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