Definition - What does Non-piggable Pipeline mean?
A non-piggable pipeline is an entire pipeline or section of pipeline that is unable to accommodate a pig device. A non-piggable pipeline is more difficult to inspect and clean because it cannot have a pig sent through it. A pipeline may be non-piggable because of extreme bends or changes in diameter.
Corrosionpedia explains Non-piggable Pipeline
A non-piggable pipeline can be a concern for several reasons. One such reason is the difficulty conducting inspections. Smart pigs are often sent through pipelines to do routine checks on the rate of corrosion. Smart pigs are also used to determine if there are cracks, dents or other mechanical defects within the internal diameter of the pipeline. Another reason is because pigs are often used to clean pipelines. Without another means to clean a non-piggable pipeline, the risk of clogging or localized corrosion is greater.
The risks associated with not being able to send a pig through a pipeline can be mitigated by a variety of alternatives. Cleaning can be performed by various flushing techniques. A substitute for a smart pig inspection is a device that is smaller than but similar to a smart pig. These miniature pigs use ultrasonic waves to determine the integrity of a pipeline without actually being in constant contact with the inside wall of the pipeline.