Complex sentence: Pigging in the maintenance of pipelines refers to the practice of using pipeline inspection gauges or'pigs' to perform various operations on a pipeline without stopping the flow of the product in the pipeline.
Split into simpler sentences: Pigging in the context of pipelines refers to the practice of using pipeline inspection gauges or'pigs' to perform various maintenance operations on a pipeline. This is done without stopping the flow of the product in the pipeline.