Consequence Assessments

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AS2885.6 Clause 3.5.2 Severity Analysis
AS2885.6 Appendix G Consequences Assessment

Q: Have there been any fatalities from non-ignited loss of containment events?

There has never been a fatality in Australia from failure of an operating pipeline, ignited or otherwise. I'm unable to comment on overseas data. (Peter Tuft)

Q: Where there is no fatality and no loss of supply, would you consider asset damage in the same category as risk to people?

(Jeff Jones/Susan Jaques) The AS2885.6 SMS and risk assessment process does not explicitly focus on asset damage but it may be relevant in assessing threats having Supply consequences, or threats with delayed failure (gouge/dents). Otherwise it's probably an issue for the owner/operator in terms of business or commercial outcomes, and that is very much not the intended domain of AS2885.

If the threat is excavator penetration with a leak, what is the assessment within different location classes e.g. in T1 versus R2. How do Major versus Catastrophic assessments apply?

(Jeff Jones) Regardless of the location class defined in the context of the threat description, the consequences of the threat impact scenario need to be defined, and then selected from the risk assessment Severity Table in Part 6. i.e. - just because you have a threat scenario in a T2 location, doesn't mean the threat consequence is automatically a "Catastrophic" (multiple fatalities) consequence.

See Also High Consequence Recognition

Shouldn’t the ‘supply’ consequence be a commercial decision by the licensee and not be dictated by the standard?

(Peter Tuft) That is correct if the supply consequences are in fact purely commercial. However for a pipeline that is the major or sole source of supply to a community, the loss of supply can be highly disruptive to the community, and it is those community consequences that AS 2885 is concerned about. Just ask anyone who was in Melbourne when the Longford gas plant exploded in 1998 (not a pipeline failure, but consequences for Melbourne were the same).

The societal consequences of supply disruption are beautifully demonstrated in this fascinating video about the 2004 Pohangina Bridge incident in New Zealand.

If we have a pipeline rupture that led to large industrial load shedding for a city for a week, but with no load loss at all any domestic or commercial customers would you see the severity as Minor, Major or Severe?

First of all, there is good guidance on severity assessment in Appendix G of AS 2885 Part 6, and G3 is particularly relevant to this question about supply disruption. The points made there are not repeated here, other than to reiterate the first sentence from G3 (with emphasis added): “This Standard is concerned about the impact of supply disruption on society”.

The starting point to answer the question is the severity descriptions in Table 3.1 of Part 6. However before the question can be assessed against those descriptions it is vital that we understand exactly how society is impacted by this particular disruption. And because those severity descriptions are necessarily brief some interpretation and judgement is often necessary to apply them to a specific case.

An SMS workshop considering an issue such as described by the question would need to consider the nature of the industrial customer(s) whose supply is curtailed, what their activities are and whether there are flow-on impacts to broader society. We also need to know whether the city in question is a regional centre (maybe 100,000 or so people) or a capital (well over a million). To pick some examples:

  • If one of the industrial loads was a milk processor and interruption meant no fresh milk in a capital city for a week then that would probably rank as Severe. It is not literally “Localised societal impact or short-term supply interruption (hours)” because it is neither localised (whole city is affected) nor short term (a week rather than hours). But nor is it a complete interruption of everything dependent on gas so it does not seem serious enough to deserve Major: “Widespread loss of supply to a major city for city for a short time (hours) or to a localised area for a longer time”.
  • If a fertiliser manufacturer lost supply it may have negligible broader impact provided that they have reasonable stockpiles, and even if they don’t it would at worst mean farmers getting their fertiliser a week late which doesn’t sound too terrible. That would probably be Minor: “Interruption or restriction of supply but shortfall met from other sources”.

Having said all that, bear in mind that the ultimate objective of consequence assessment is to identify whether or not the risk is tolerable (and to specify corrective actions if it not tolerable). High precision in estimating the consequences of supply disruption is not necessary. In most cases a properly constituted SMS workshop should have enough people with enough knowledge to make an adequate judgement. Because these are matters of judgement and there are no absolute answers.