Page 451 - Pipeline Pigging Technology

Pipeline Pigging Technology

Fig.6. Economic risk components.
Economic risk = outage probability x outage consequences

One of the most significant components included in the estimate of outage
consequences is the potential reduction in exported gas volumes, caused by
an outage. Although this is not a direct cost to NOVA and its estimated value
is subject to some assumptions, it is included to recognize the importance of
each pipeline segment to the reliable performance of the Alberta gas industry.
The other components of outage consequences are the value of lost gas and
repair cost.
The results of the economic risk assessment can be effectively illustrated
using the diagram in Fig.6, which shows how the probability and conse-
quences are contributing to the economic risk. In general, pipeline segments
with high outage probability are those with a history of known specific
problems, (Points 1,2 and 5, for example, in Fig.9) which require monitoring
and maintenance on a periodic basis to prevent operating failures. Inspection
and assessment projects for such lines have historically been the core of our
pipeline integrity programme; however, in recent years, projects have been
planned and carried out on other pipeline segments based solely on the
results of the economic risk assessment. These lines generally have only
moderate outage probabilities, no history of failures, but high outage conse-
quences (Points 3 and 4 in Fig.7, for example).
The effect of a pipeline integrity project is to reduce the outage probability
for a pipeline segment, shifting its position to the left, as shown for several
completed projects in Fig.8, to a lower value of economic risk.

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