Page 38 - Gi flipbook - November 2018

IGEM NEWS | Young Persons Paper Competition 2018

SUMMARY
The 2015, ILI classified a single feature FIGURE 4: Main and secondary features after grit blasting and white background paint
as an ‘unknown feature’. This was
previously classified as an external
manufacturing feature. A desktop
study and site visit showed no obvious
cause for the feature. With the change
in classification and the feature being
oriented at the 12 o’clock position
with a circular profile, it was decided
to excavate. This revealed a hole that
had penetrated a reinforced concrete
slab and significant metal loss from
the pipeline. The damage was
produced by mechanised drilling
equipment. It was safely investigated,
assessed and remediated with no
impact on gas supply.
The four ILIs performed on the
pipeline used the same MFL
technology from the same ILI vendor.
A combination of change in threats to
pipeline integrity, a slight indication on
the calliper arm of the inspection tool,
30 years of experience inspecting
pipelines and data analysis, and an
individual’s discretion led to the
feature being classified as ‘unknown’.
The pylon in close proximity to the
pipeline damage was constructed after
the pipeline. There are no records of
boreholes in the area of the pipeline
damage. The council-owned land
where the damage was found is used
by a wildlife charity. The council has
a database of boreholes, but no FIGURE 5: Location of test posts marked and area of aerial marker highlighted in orange
records of boreholes in the vicinity
of the damage.
LESSONS LEARNT
Inspection data needs to be assessed
in accordance with credible threats.
These threats will change with time.
We must remain inquisitive and
mindful that past decisions were
made with the knowledge of the time.
Awareness of gas pipelines is
essential and stakeholder engagement
is key. We cannot become complacent PYLON
with the exceptional safety record to
date of pipelines. This case study has
been shared with the wider industry,
local councils and land users on an
ongoing basis.
Areas at risk from third party
interaction (e.g., where liquid pipelines
come in close proximity to NGN
pipelines) have been earmarked to be
surveyed at appropriate intervals. ■ AERIAL MARKER POST

REFERENCES
1. National Transportation Safety Board, ‘Pipeline Accident
Brief, DCA-10-FP-004’, Document Number NTSB/PAB-13/2, 9
Sept 2013
2. Northern Gas Networks, ‘P11 BISHOP AUCKLAND TO
RIVER TYNE SOUTH SB03 416447 564448’, 1 Sept 2016.
3. Land Registry, Title number TY532143, 6 Nov 2015.

38

IGEMNews_YPPC.indd 3 18/10/2018 13:39