Pig (pipeline pig, scraper)

A pig is a flexible “plug” that moves through a pipe and pushes the product ahead of it.

A pig has a diameter slightly larger than that of the pipe. Thanks to its flexibility, it adapts to the inside of the pipe and fits tightly against the walls, scraping the product off them as it moves. The pig gives its name to the whole technology, pigging. It is also known as a pipeline pig or a scraper.

Pigs are made from materials approved for food contact or resistant to chemicals, such as food-grade silicone, EPDM, FKM or polyurethane. Most have a magnet inside, which allows sensors on the pipe to detect where the pig is. There are two main types:

• single-piece pigs, which are more hygienic, easier to clean and less likely to break apart,
• pigs with replaceable seals, more commonly used in the chemical and fuel industries.

Example: In a shampoo production plant, a silicone pig moves through a stainless steel pipe. Its edges press against the pipe walls and collect the layer of shampoo, just as a rubber squeegee wipes water off a window.