A direct
Shamus McDonnell,
PureHM (formerly
Hunter McDonnell
Pipeline Services),
Canada,
discusses
integrity management:
how direct assessment
is improving pipeline
inspection.
O
il and gas
pipelines
have
been
around for well over a century, and some
of the earliest constructed are still in service
today. Although early pipelines were made of wood
– and in the past few decades plastics and composite
materials, which have increased in popularity – the vast
majority of pipelines in service today are constructed with
steel.
Like any pipe material, steel has its downfalls. Steel has a
propensity to dent, buckle, corrode and crack when exposed
to the environment. Steel pipelines carrying combustible
hydrocarbons are buried underground with typically ~1 m
(3 ft) of cover to protect them. In order to mitigate corrosion,
pipelines are covered with a protective coating, utilise
cathodic protection (CP), and have their pressure regulated to
reduce crack formation and propagation.
Despite all of the design innovations made over the past
century, it has not been enough to prevent failures – even
on the most recently constructed pipelines. Weather cycles,
frost heaves, and road loadings cause physical damage to
the pipeline and protective coating. Operational errors and
material defects cause the steel to succumb after years of
relentless pressure cycles from the pipeline product itself.
Therefore, proactive pipeline inspections are needed to
identify defects, before they cause a leak or rupture.
Pipeline integrity can be validated and assessed using three
primary techniques: hydrotesting, the use of inline inspection
(ILI) tools and direct assessment (DA).
APPROACH
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