Page 253 - Pipeline Pigging Technology

Pipeline Pigging Technology

Fig. 5. Batch between pigs.

inefficient pig is one of the more common and costly mistakes made in
pipeline maintenance. Liquids and deposits can be left in the pipeline,
although frequent pigging is performed. It is also possible to lose costly
chemicals when batching, due to excess by-pass around worn sealing parts.

SUMMARY AND RECOMMENDATIONS

Both chemical treatment and mechanical pigging offer solutions to various
pipeline operating problems; however, neither method alone is likely to
provide the benefit of a combination programme. Chemicals are most
effective and efficient when used primarily to treat problems at the pipe
surface, such as the formation of wax deposits, bacteria colonies and corro-
sion. Pigs are best used to prepare the pipe surface for the application of
chemicals, to help distribute the chemicals evenly throughout the pipeline,
and to minimize the volume of chemicals needed by removing bulk deposits
and entrapped fluids. If chemical treatment and pigging are combined in a
well-developed preventive-maintenance programme, it is possible to keep
corrosion damage to a minimum, maximize the operating efficiency of the
pipeline, and reduce chemical treatment costs.
The following recommendations should be followed when developing a
chemical treatment and pigging programme:

(1) conduct a thorough analysis of the pipeline's operating conditions,
identifying all possible flow, deposition or corrosion problems;

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