As product recovery becomes more efficient, the volume of waste effluent will be reduced. One proven method to accomplish this goal is with a product recovery system that uses a device called a "pig". A pig can be best described as a cylindrical device propelled through a piece of pipe by differential pressure. The pig is slightly larger than the internal diameter of the pipe, exerting force against the pipe's surface to create a sealing, wiping effect.
Running a pig in a line can be compared to the system that carries checks and money from your car to the teller at a drive-thru bank. Pigging has been used in the oil and gas pipeline industry for nearly 100 years. Though not new to process plants, the interest in industrial pigging systems has increased as plants struggle to produce more sellable product while reducing the costs associated with treatment of waste effluent. Pigging systems have been used by plants manufacturing numerous products, from adhesives, sealants, paints, and ink to lube oils and food-grade products.