using the ROV-iT, an ROV-deployed ultrasonic inspection tool
developed by the company.
A major objective of the inspection was to validate
absence of low level degradation so that a case could be
made for operation without the need for inline inspection.
Since the coverage for the subsea inspection was low, meeting
this objective was dependent on providing a highly sensitive
inspection with accurate wall thickness measurements on a
fine scan increment.
The inspection performance achieved at a depth of
1435 m, through a 3-layer polypropylene coating, matched that
in shallow water, demonstrating Sonomatic’s capability to
deliver its world leading corrosion mapping accuracy even at
great depth. The results of the detailed analysis of inspection
performance, as achieved in
the field, were central to the
integrity assessment. This was
based on statistical methods
developed by Sonomatic
for planning and evaluation
of targeted inspections on
unpiggable gas pipelines. The
inspection demonstrated that
the probability of degradation,
with potential to threaten
integrity for the line as a
whole, was within acceptable
limits.
Sonomatic’s industry
leading measurement
performance was central to
ensuring this objective was
met and that the result was a
substantial cost saving to the
client. An inline inspection,
which would have relied on
a very expensive deepwater
launch of the intelligent
pig, was avoided. The
subsea inspection work
was completed safely and within the planned
schedule, with Sonomatic’s equipment operating
effectively and reliablly throughout the
campaign.
New techniques for subsea
deployment
Sonomatic’s ROV-deployed tools have been
designed for inspecting pipelines, risers, caissons
and structural assets. The tools are adaptable,
operating on both horizontal and vertical pipes
ranging from 6 - 30 in. dia. A range of ultrasonic
inspection techniques can be deployed including
corrosion mapping, time of flight diffraction (TOFD),
automated shear wave pulse echo and component
geometry measurement.
The inspection techniques, and combinations
thereof, that are deployed means the following applications
can be addressed:
)
)
Verification of ILI tool findings.
)
)
Targeted inspection for unpiggable pipelines.
)
)
Inspection for internal corrosion and erosion.
)
)
Inspection for preferential weld corrosion/erosion.
)
)
Inspection for fatigue or stress corrosion cracking.
)
)
Inspection for wet H
2
S damage in sour service.
)
)
Inspection for chloride pitting/SCC in corrosion resistant
alloys.
Figure 1.
Inspection carried out using the ROV-iT, an ROV-deployed ultrasonic inspection tool
developed by Sonomatic.
Figure 2.
Corrosion map of region of subsea pipeline with internal
degradation.
68
World Pipelines
/
JUNE 2015
