Page 449 - Pipeline Pigging Technology

Pipeline Pigging Technology

Fig.4. Risk spectra for a specific location (accidents with N or more
fatalities).
integrity projects intended to reduce or eliminate corrosion failures, for
example, will reduce the total outage probability, but will not totally elimi-
nate failures which may still occur due to other causes.
The fault-tree branch for stress corrosion cracking (SCO was only recently
included, and is expected to evolve as industry understanding and experience
develops. Although SCC has been located in the system and led to one
hydrostatic testing project, no operating failures have occurred.

Safety risk

The probability of life loss for a leak or rupture can be considered as:

(Probability of life loss) = (probability of an ignited gas release) x
(probability of occupied lethal site)

The safety risks associated with deterioration of structural integrity really
amount to the risk of being in the wrong place at the wrong time, when a
failure occurs. With only a few exceptions, the NOVA system is remote from
populated areas, and these risks are estimated to be very low for both
employees and the public. This is consistent with the excellent safety record
of the NOVA system and other gas pipelines. No life-loss or injury incident has
been recorded from a leak or rupture over the life of the NOVA system. To the
present time, only one pipeline integrity project has been initiated specifi-
cally to reduce public safety risk because the risks are assessed as being very
low.

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