HAZOPs

I continue to be surprised at some of the pipeline incidents reported in the US.  This recent article talks about two occasions on which pipelines were over-pressured to nearly 160% and nearly 190% of MAOP.  Fortunately there were no further consequences such as loss of containment.  One of the pipeline sections was 21 miles long (34 km), and with that volume of linepack the overpressure was clearly not a momentary failing.  But the article is in the general media, not a technical report, so there is a lot unsaid.  Reading between the lines one can infer that in each case there was a lack of redundancy in the pressure control system so that a simple failure had a serious outcome.

It would be interesting to know whether HAZOP studies had been done for these pipelines.  While no HAZOP is perfect (nor any other risk identification technique) one would expect that a properly completed HAZOP should have a high likelihood of identifying and fixing single failures that can lead to such extreme overpressure.

Pipelines and their facilities are very simple in comparison to process plants, but not so simple that a HAZOP review is a  trivial exercise.  Those in which I have participated have always made quite a number of recommendations for improvement in both the safety and operability of the installation.  I’ve also had the experience of being in a HAZOP for a routine new installation using an older “standard” design that was found to have some significant shortcomings, to the surprise of those who had been using it for a long time.

In my experience HAZOP studies were not done for Australian pipelines until the early 1990s.  If that’s generally true then there are possibly a lot of older installations out there that have never been through the process.  HAZOP is now mandatory for new pipeline designs under AS 2885.1-2007 – see Clause 2.4.2(a).   However the standard is not retrospective so it doesn’t mandate HAZOPs for existing pipelines.  Nevertheless if there is no record of a HAZOP for your pipeline then that’s something you should think about quite seriously.

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10 Responses to HAZOPs

  1. Michael Malavazos says:

    Good point made in last sentence, this is something as a regulator I expect pipeliners to revisit as part of their regulatory mandated 5 year fitness for purpose review

    • petertuft says:

      Mike,
      Am I correct in thinking that the 5 year fitness for purpose review is something that you have in the South Australian regulations? AS 2885.3 requires regular reviews of a few things but not as broad as overall fitness for purpose.

  2. Chris Hughes says:

    One of the things that I query and comment on often is the fact that the overpressure control for the pipeline is frequently outside the remit of the pipeline design e.g. the pipeline is supplied from a compressor station designed and operated by others and the pipeline has no overpressure control of its own apart from that incorporated into the compressor station design. It is debatable whether this actually meets the pipeline licence condition of complying with AS2885 since the pipeline, taken as an independent entity, does not have the necessary two levels of overpressure control.

    I remember when I was Engineering Manager for a pipeline in the Philippines, when we held the HAZOP I insisted that the designers of the upstream plant should be present: when we got to one part talking about the delivery parameters from the plant to the pipeline we discovered that the design they were currently working on was different to the one in the FEED and our scope of work documentation. If they hadn’t been there our design would have been based on a totally incorrect premise (this related to temperature, not pressure, but the reasoning remains the same).

    If you don’t have control over the upstream design and cannot include it in your HAZOP then I believe you have to include your own independent overpressure control.

    • petertuft says:

      Good point. I too have seen a few projects where pressure control by an upstream party is just assumed to be effective. Definitely a lesson in that one, to at least maintain close liaison with the upstream people even if they can’t be persuaded to participate in the HAZOP (which I agree is better).

  3. Mike Dunkerton says:

    A HAZOP is great in design. However, there seems to be an assumption that this was a design issue. Perhaps controls were in place as required by a HAZOP, but they didn’t work. Who is auditing that safety critical systems such as trips are being tested, pressure safety valves are being tested etc? Investigations of recent events (admittedly, not pipelines) in the States have identified a lack of regulatory oversight. The system appears to be only as good as the integrity of the operating company.

    • petertuft says:

      I think there’s a common theme underlying all of these comments so far – vigilance. Good and safe design (helped by HAZOP among other things) is prerequisite for safe operation, but it certainly doesn’t end there. Also necessary are regular reviews, audits, change management systems, etc.

  4. Michael Malavazos says:

    Peter,

    In response to your query, yes under section 86A of the Petroleum and Geothermal Energy Act 2000 in SA and Regultion 30, all licensees operating facilities and pipelines licensed under this Act must undertake fitness for purpose assessments at least every 5 years, such reports are also publicly available. We as regulator then use these reports to validate conclusions mad int hereport by requesting additional and more detailed emonstrations from the licensee.

  5. Jan Hayes says:

    Good idea about not ignoring HAZOP for pipelines although speaking as a HAZOP chair, I think that a HAZOP of a pipeline on its own would need to be scoped very carefully. The pipeline is pretty passive from a process perspective and it would be a very poor HAZOP that did not take into account the full possible range of both the upstream and downstream conditions. This would normally mean that you would need people with design /operations experience from adjacent facilities involved as well as those who really understand the pipeline itself.

    Of course the converse is true too – you can’t say the pipeline was effectively HAZOPed just because the adjacent facilities were HAZOPed although I have seen people try to put forward that argument.

    • petertuft says:

      Pipelines almost always have mainline valve and scraper trap assemblies, which are pretty simple but still need a HAZOP. They also very often have metering facilities and pressure regulation stations complete with filters and heaters, which are starting to become mildly complex assemblies of equipment. All this stuff comes under AS 2885 and is unlikely to be covered by HAZOP of the upstream supply plant or downstream customer facilities. So even though the pipe bit of a pipeline system is pretty passive there is usually enough control and ancillary equipment to keep a HAZOP team fully occupied for at least a day.

      No argument with the need for representatives from the upstream and downstream facilities, as also noted in Chris Hughes’ earlier comment.

  6. Anonymous says:

    But the question here will remain whether the HAZOP is required for an existing Pipeline Network from time to time OR its enough to consider only HAZOP for newly added pipeline with its Tie In point only.

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