Page 186 - Pipeline Pigging Technology

Gellypig technology for pipeline conversion

Pipe samples were taken for analysis from the Sulfur Creek and St.Charles
Junction areas. The analysis results, shown in Table 1, were used in designing
the pig train. The caustic degreaser (M002, MOOS, M009, F057) proved to be
the solvent of choice for removal of the light crude oil found in the sample
pipe. Other solvent candidates included diesel-based emulsions, hydrocar-
bons such as kerosene, aromatics and chlorinated solvents. However, based
on solubility testing, disposal concerns, economics, and safety considera-
tions, the caustic degreaser was overall the most appropriate choice.
The amount of debris found in the sample averaged approximately 20g/ft 2
2
of internal surface area (or 0.044lb/ft ). Similar conversion projects in the
2
2
midwestern US have ranged from 0.031b/ft to more than 0.091b/ft ! A debris
loading factor of 0.051b/ft 2 was used in this case to calculate the required
amount of debris removal gel. This was slightly higher than the laboratory
value, which would provide some safety factor to account for loose debris
localized in the pipeline, or debris loading in excess of the sampled amount.
The debris removal gellypig (GP3100) is designed to entrain up to lib of
debris in Igal of gel. There are many variables which can affect this number
(e.g. pig train velocity, debris density, quantity of debris, mechanical pigs, and
more), but for design purposes 1 Ib/gal is the standard number used for "debris
gel strength".
The equation to calculate the amount of debris removal gel required is as
follows:

2
Total debris gel required=Internal surface area (ft) x Debris loading factor
2
Ob/ft) / Debris gel strength Ob/gal)
The gellypig trains designed for the two phases of this service were very
similar, with the only major design difference being the quantity of debris gel
used, for the respective lengths of the pipeline. Based on the above calcula-
tions, approximately 36,400 and 18,200galls of debris removal gel (GP3100)

Table 2. Volume of degreaser vs contact time.

Contact VOLUME OF DEGREASER (gal)
Time @ train velocity (ft/sec) of
(hrs) 3 2 1

8 507,168 338,112 169,056
6 380,376 253,584 126,792
4 253,584 169,056 84,528

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