Wax deposition in crude oil pipeline is common throughout the oil & gas industry, especially in long cross country pipelines. Solid wax particles get precipitated and are retained in the pipeline interiors. The interior diameter of the pipe is thus reduced. This reduces throughput, escalates the pumping costs due to reduced pipe diameters and boosts pipe wall friction.
A cost effective solution to remove debris such as wax is using foam pigs. Recently a crude pipeline showed severe pressure build-up due to such wax deposits. Solvent slugs between foam pigs were used to clean the affected line. A candle was removed from the pipeline without any pressure build-up during the pigging operation.

Image:

1. Foam pig being removed from the pipeline
2. & 3. Wax debris removed from the pipeline
3. Foam pig with wax remains on the surface post cleaning
4. Entire bore of pipe filled with wax