Page 195 - Pipeline Pigging Technology

Pipeline Pigging Technology

pipeline is at or near maximum flowrate, but the debris amounts have been
insignificant and easily controlled with routine filtration.

CONCLUSIONS

1. The conversion of existing or abandoned crude oil pipelines to natural
gas service can be accomplished, in a manner which will reduce debris and
residual crude oil in the pipeline, thereby reducing potential operational and
environmental problems. Gellypigs and an appropriate degreaser are very
effective in removing residual crude oil and debris in these pipelines.
2. Solvent testing under laboratory conditions may not always be indicative
of the actual degree of residual crude oil removal under dynamic field
conditions. There are many variables which may cause residual crude oil
removal to be significantly different. In this case, the degreaser performed
beyond expectations for the given contact times and volumes.
3. The removal of debris and residual crude oil can be performed by a single
complex cleaning pig train.
4. The effectiveness of activated carbon or other filtration devices for
satisfying EPA specifications for discharge, were inconclusive, since they
were not used, although laboratory testing indicated that activated carbon
would be very effective in reducing oil and grease content. Traditional
methods of filtration (i.e. cartridges or bags) could adequately control sus-
pended solids.
5. Representative sampling and efficient mechanical pigs are critical
components for the total success of a gellypig pipeline service. The sample
submitted for analysis appears to have been in worse condition than the
average, therefore making the design conservative. The mechanical pigs
appear to have performed to expectations. Both would contribute to a
successful service.
6. All the following results suggest that the pipeline should be relatively
free of loose debris and residual crude oil:

(a) the final gels contained extremely low amounts of debris;
(b) the final hydrotest water contained low amounts of oil and grease
and suspended particles (i.e. approximately 5 and 40ppm, respec-
tively);
(c) large amounts of debris, and oil and grease, were removed in the
front portion of the pig train;
(d) the train velocities were excellent for optimum debris removal;

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