The AS 2885 risk evaluation process requires the consequences of pipeline failure to be assessed on three dimensions (Appendix F2):
- human injury or fatality
- interruption to continuity of supply with economic impact
- environmental damage
(Also known as the people, supply and environment dimensions.)
It is interesting that the formal definition of supply impact includes the words “with economic impact“. For some time now I have considered that a supply impact is significant only if it has an effect on the community rather than an economic effect.
In the AS 2885 risk matrix a severity of “Major” should be assigned if the consequence for people is “a few fatalities or several people with life-threatening injuries” or if the supply consequence is “prolonged interruption or long-term restriction of supply”. But consider two pipelines with different delivery points:
- A plant producing LNG for export
- A major city that depends on the pipeline for 70% of its gas
A prolonged interruption to Pipeline 1 has a purely economic impact, affecting only the businesses involved in the pipeline and LNG plant, with no community or third party involvement. In my opinion that is not a consequence that is comparable to “few fatalities or several life-threatening injuries”. On the other hand a prolonged interruption to Pipeline 2 does seem to sit at roughly the same point on the severity scale as “few fatalities …”, as residents of Melbourne during the aftermath of the 1998 Longford disaster would probably agree. The affected community would be severely inconvenienced, and in my mind that is what counts.
A bit of thought is necessary to understand the ramifications of supply interruption. A pipeline that supplies a power station may have a major effect on a community, or none, depending on what other power supply options are available. For a pipeline I once looked at in a third-world country the effect of supply interruption appeared at first glance to be purely economic (loss of profits to the multinational company that owned it) but once I remembered that the pipeline and associated projects would contribute something like 30% of the country’s GDP the loss of supply took on a whole different complexion because of the impact on a struggling society.
I have used the Major severity score in the examples discussed here, but similar illustrations could be developed for the other severity scores from Trivial to Catastrophic. The principle is the same – impact on the community should count more than purely economic impact.
Of course nothing is ever perfectly clear-cut. The Varanus Island failure in June 2008 was said to cost the WA economy $3 billion. I don’t know how that was calculated but can guess it was probably the effect on third party industrial gas consumers who were shut down so that the limited gas available could continue to supply domestic consumers. The community might not have been inconvenienced by cold showers and threats to hospital boilers, but the supply restriction had effects much more widespread than the parties directly involved (gas supplier and shippers).
I think that is the point – supply interruption counts when it affects third parties, either directly (blackouts, cold showers) or economically. To my mind economic impacts on first and second parties (pipeline owners, gas shippers) don’t count for the purpose of the safety management study.
Discussion welcome …