Page 191 - Pipeline Pigging Technology

Pipeline Pigging Technology

mechanical pigs, and degreaser were then launched (injected) into the
pipeline, in the appropriate sequence (see Fig.3).
The pig train was driven with compressed air at a target velocity of
approximately 2ft/sec, which is considered to be the optimum speed for
debris removal with the gellypig. On the average, gellypig trains are generally
driven between l-3ft/sec, dependent upon the parameters of the specific
situation. Missouri Pipeline personnel (or its contractors), monitored the
progress of the trains. The velocities of both trains were very good, with Phase
2 being relatively low, due to intentionally stopping the train at times, for
various reasons. The maximum pressure required to push the gellypig trains
was approximately 220-230psig, with the pressures generally ranging from
180-200psig.
When the pig train arrived at the end of each section, the mechanical pigs
were retrieved, and the gellypigs and degreaser diverted into frac. tanks. The
separator gel is a cross-linked polymer, which creates a very viscous three-
dimensional gel. As the separator gellypig was directed towards the frac.
tanks, a "breaker" was added to the gel, to "break" the cross-linked chemical
bonds, thereby reducing the viscosity of the gel. Samples of the gel and
degreaser were taken from the various sections of the pig train for laboratory
analysis.
All gellypigs, degreaser, and material removed from the pipeline, were
stored in 21,000gall holding tanks (frac. tanks), at Chantilly and Curryville. DS
arranged for disposal, and assisted in characterizing the waste. Missouri
Pipeline provided an EPA generator number and manifested the waste.
Samples of the waste were obtained from each tank, and the waste character-
ized. A reputable, licensed disposal firm was then contracted to dispose of the
material in accordance with any and all applicable local, state, and federal
rules and regulations. The gellypigs are non-regulated, non-hazardous, biode-
gradable materials, and present no environmental problems in disposal.
However, due to the changing composition of the gel as it passes through the
pipeline, precautions must be taken to properly dispose of the used gels and
materials.
The pipeline was successfully hydrotested after the gellypig service.
Drying of the pipeline was accomplished by Missouri Pipeline using metha-
nol, mechanical (cup) pigs, and many foam swab pigs.
Overall, the execution of the job went very well and according to plan,
although there were some minor complications, primarily caused by the
extremely cold weather. Temperatures plunged to below 0°F, and around
-50°F wind chill factor, during some portions of the job. This presented some
minor freezing problems when mixing the gels, storing the waste materials
until they could be transported, cleaning the frac. tanks, and some mechani-

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