What pigging is and how it works

To ‘pig’ a system, HPS pigs are propelled through the pipe by pressurizing the pipe work behind it. There are different ways to propel pigs, but usually compressed air, carbon dioxide (CO2), nitrogen, clean water or even the next product (depending on the application) provide the pressure. Instead of being flushed to drain, waste treatment or collection areas, the liquid residue in the pipe is recovered: pushed by the pig and forced to the destination filler or tank to continue processing along with the rest of the product.

What many people don’t realise is that pigging is an extremely quick process. The precise speed at which a pig travels depends on a number of factors; however, the process is nearly always a lot quicker than many people think. This is great because it saves time and labour with reduced CIP and speeds up changeovers. Here’s a video which shows how fast a pig travels through a pipeline or tube. See how there’s no product left on the clear tube after pigging and how fast the pig travels; it’s all done in an instant!

A pigging system is made up of a variety of different parts and components. These include pig launchers, receivers, detectors, storage, housings, propellant sources, PLCs, HMI’s, control software, and various valves, supports and fittings.

Pigging system components are often fitted on existing process equipment or can be built into new designs. However, the most important component is the pig itself. The operational efficiency, effectiveness and ultimately the success of a pigging project depends on a reliable, high-performance, well designed, good quality pig.

Learn more about the key components of a pigging system

There’s a massive range of liquid products and processes that use pigging. Examples of these include food and beverages (which use hygienic or sanitary pigs and hygienic or sanitary tubing), as well as household, personal care, cosmetics, paints and pet food production.

While pigging is used in a wide variety of different industries and sectors to achieve different results and goals, the main purpose of pigging usually centres on product recovery, product transfer, environmental sustainability and operational efficiency.

Read our pigging case studies

While many industrial process applications use pigging, it’s also used in utility industries, such as oil, gas and water. However, while the principles are similar, there are big differences between industrial process pigging and utility pigging.

Most HPS pigging systems are either partly or fully automated. Pigging systems with fully automated pigging process control have a wide range of benefits. This includes increasing process speed, productivity, and efficiency. Automation also enhances safety and decreases the chances of human error.

Here’s a typical example of why many industrial processes use pigging.

Imagine a paint manufacturer that needs to switch between different paint types or colours several times a day using the same pipeline. After each transfer, traces of the previous product can remain in the pipework, clinging to the pipe walls or sitting in sections of the line.

This residual product must be removed before the next batch to reduce the risk of contamination. However, much of it may still be perfectly usable. If it is flushed away, it becomes waste rather than being processed, packaged or sold.

Without pigging, the pipeline would typically be flushed using water or cleaning fluids. This takes time, uses resources and sends valuable product to waste. Pigging helps recover this product in usable form, with HPS pigging systems able to recover up to 99.5% of product from full pipelines.

Although this example uses paint, the same principle applies to many liquid products and processing applications across food, beverage, personal care, homecare, chemicals, coatings and other sectors.