Page 445 - Pipeline Pigging Technology

Pipeline Pigging Technology

Fig.l. Nova's Alberta gas transmission division.
800 segments, each with its unique characteristics of size, terrain, materials,
construction practice, operating history, and current gas flow.
The need for a comprehensive pipeline integrity programme to maintain
the structural integrity of our system arises from recognition of several factors
which are not unique to just our system:

1. Our own experience, like that of other companies, shows that
deterioration of structural integrity does occur in some pipeline
segments of our complex system due to mechanisms such as
external corrosion, slope instability and stress corrosion cracking.
2. We have a clear responsibility to our regulators, our customers and
our shareholders to prevent structural integrity problems from
adversely affecting public safety, the reliable and economic trans-
portation of gas, and the value of our assets.
3. Operating close to design capacity on a year-round basis, as Fig.2
shows we have been recently, requires that pipeline integrity
projects be scheduled with lead times of one to two years to
minimize disruption to operations. We need to do more to anticipate
and prevent problems rather than simply react to them.
4. There are continuing signs, from newspaper coverage [1], US Public
Law 100-561 [2], and NEB of Canada recommendations [3], for exam-
ple, that regulators may impose uneconomic requirements for
periodic inspection or testing unless operators demonstrate that
they are now meeting their responsibilities for maintenance of an
ageing buried pipeline system.

Most important in the discussion of pipeline integrity is our belief that we,
as owners and operators, know more about the structural integrity of our

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