Page 18 - Gi August 2020

pipelines for a hydrogen future

Hydrogen durability trials FIGURE 4 TEST PIPE WITHOUT ENVIRONMENTAL OUTER LAYER SHOWING STRAIN GAUGES AND OPTICAL FIBRE CABLE
A gas mix including 30 per cent hydrogen
and 70 per cent methane has been used in
a flow loop setup at DNV GL Spadeadam,
with pressure cycling over an eight-
month period designed to simulate the
operational gas pressures of National
Grid Gas Transmission in the UK. This
programme is ongoing but has so far
been successful in proving hydrogen
durability alongside standard X52 pipe.

Advantages of spiral wound optical fibre
Optical fibre systems are a powerful
source of accurate data, but generally
the fibre is laid in a straight line in a
separate trench next to the pipeline. FIGURE 5 WATERFALL OUTPUT FROM CHANNELS ALONG THE TEST PIPE
The advantages of spirally winding the
fibre around the pipe are that the 360°
data collection offers a complete view of
the whole pipe and the intimate contact
enhances the data that can be collected.
Additionally, the optical fibre can be
incorporated into the structure of the
pipe at fabrication and the two-layer
environmental coating provides
protection to the fibre.
Tests were carried out using test
pipe sections with strain gauges to
calibrate the stress/strain outputs from
the fibre optic system.
The physical tests consisted of
applying a series of pressure cycles to
12-inch diameter MASiP test pipe.
When there is a pressure cycle, there
is a clear change on the pattern of hoop
and axial stress/strain distributions,
which allow a healthy pipe profile to be
recorded and used as a benchmark for FIGURE 6 INDICATIVE FRONT END VISUALISATION
data analysis.
The optical fibre cable provides
complete connectivity along the pipe.
Data gathering and pre-processing was
carried out using Optasense advanced
system, which uses interference fringes
created when light pulses are fired down
the fibre to construct baseline data on
hoop strain as well as temperature
change and acoustic transients. This is
an advanced system already in service
with linear optic fibre systems.
It was found that there was a good
correlation between the strain gauge
outputs and the fibre optic outputs for
stress strain along the pipe.
The ability of a closely wound optical
fibre to generate a large amount of data
and for this data to offer resolution to every Data management Comms node passes pre-processed
six inches of pipe length in real time offers This system generates a huge amount of data onto the main computing system
a ground-breaking approach to pipeline data on a daily basis so it is important using spare fibres
integrity management. Spare fibres in the to have an organised data management Data aggregator is the first level of
cable allow dedicated fibres for specific system. processing at the main servers,
parameters of interest and also for general The processing system comprises formulating data for bulk storage
communications. All these benefits in one seven areas: Storage is a large volume data store
fibre cable provide a real advantage over DAS is the field equipment on the pipe for long term access to data
conventional systems. referred to above Data analysis is where the main

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