Page 38 - Gi flipbook April 2018

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dust and oil was discovered. This
provided us with confirmation that FIGURE F: Evidence of dry grease and FIGURE I: Drawing detailing sections of
the filters were operating effectively metal deposits visible within the valve seat pipeline identified for camera inspection
and brought us to the conclusion that
the metal debris found within the
valve was more than likely a result of
a site filter replacement seven years
ago. (See Figure G)
Dry grease deposits are common
within high pressure natural gas
pipelines fed off compressor stations
such as St Fergus, and are a result of
oxidised oil drying lubricant grease
within valves over a period of time.
I explored this theory further with
the help of a technical inspector from
Mobil Industrial who informed me
that the potential effects of oxidised FIGURE G: Large mixture of metal debris, FIGURE J: The camera inspection operative
oil on lubricant grease is one of their dust and oil found within the site inlet filters and I in the surveillance control room
biggest challenges as an industry
lubricant provider.
This brought us to our next
conclusion; a month prior to the valve
failure, maintenance was carried out
on the NTS which involved down-
rating of the site inlet from 82bar to
35bar. The pressure differential across
the pipeline would have been more
than sufficient to allow for dry grease
deposits located after the site inlet
filters to become dislodged and travel
downstream. (See Figure H)

WHAT HAS HAPPENED SINCE? FIGURE H: Dry grease and small metal FIGURE K: An image captured from within
As a result of our findings, we took deposits found within Mokveld valve the pipeline
the decision to inspect the pipeline
further in order to identify any
potential areas of concern.
My colleagues and I were tasked
with organising an inlet pipeline
inspection during which we requested
the assistance of a specialist camera
surveillance team. We carefully
examined site drawings and
established areas where dry grease
could be present (See Figure I).
Red line = above ground pipeline.
Blue line = below ground pipeline.
Pink circle = Mokveld FCV. and foreign debris discovered within the industry and has furthered my
Along with the camera surveillance the valve, our findings from the filter understanding of transmission pressure
operative, I assisted in the supervision and pipeline inspections, and the final control, high pressure pipelines and
and co-ordination of the camera diagnostics report from Mokveld, we procedures surrounding operational
pipeline inspection in order to ensure had an opportunity to accurately supervision. ■
all areas of interest were fully review and identify key aspects of the
reviewed and captured for further valve failure to support our efforts to REFERENCES
analysis. (See Figure J) explore further potential maintenance Mobil Industrial: www.mobil.com/en/industrial/
The camera inspection was strategies and prevent such an event lubricants/applications/natural-gas-compressors
successful and we were able to fully from reoccurring. Mokveld: www.mokveld.com/en/axial-control-
inspect all potential areas of concern On a personal level, the events valve#product-summary
without discovering any further surrounding the valve failure provided SGN: www.sgn.co.uk/uploadedFiles/Marketing/
deposits of dry grease or foreign me with the opportunity to be involved Pages/Publications/Docs-Annual-Reports/
SGN-Annual-Report-2016.pdf
debris. (See Figure K) in a very specific operation which was ACKNOWLEDGEMENTS
highly unlikely to occur again. The
SUMMARY experience has been fundamental in Acknowledgement and thanks go to my colleagues
at SGN who have supported me in gathering
As a result of the dry grease deposits my development as a manager within information and offering feedback on my progress.

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