Page 219 - Pipeline Pigging Technology

Pipeline Pigging Technology

Fig.6. Summary of inspection runs.

safe passage. However, problems did occur for the corrosion vehicles due to
some heavy-wall tees with internal diameters less than the allowable. Indica-
tions are that the calliper log did indicate the restrictions; however, more
careful interpretation would have been required to highlight these. Likewise
for the profile tools; it was a difficult task to determine what was normal wear
on the gauge plates and what was the result of a mild diameter restriction.
Particular care must be taken to evaluate all the information thoroughly and
collectively.
A nitrogen line pack of 3500kPa was used to prevent tool surge. This is
somewhat lower than at first thought necessary, yet it proved to work
consistently well for all inspection runs. Only one velocity excursion was

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