Pigging – What Pigging Is and How It Works

Pigging – An Overview of Product Recovery in Liquid Processing

Pigging technology has been around in different forms since the early part of the twentieth century. Today, a wide variety of sectors, industries and applications that process liquids use pigging (more accurately described as ‘Liquid Product Recovery’) to reclaim liquids from pipelines and tubing, reduce waste and improve the efficiency of their manufacturing and production processes.

Despite it being in common use in factories and production facilities throughout the world, we’re often asked to give an explanation of what pigging is and describe what it does.

So, here’s an overview of pigging: what it is, why it’s used, the pigging process and how it works.

So What is Pigging?

In the process industries, pigging refers to technology that uses specialist projectiles to recover, rather than waste, residual liquid in pipelines or industrial tubing. It has progressed from basic equipment used to clean oil pipes, to advanced, fully automated industrial product recovery and liquid transfer technology used today.

So, if you drink wine, beer, spirits, fruit juices, cola or other types of soft drinks; if you eat chocolate, sweets, candy, yoghurt, soup, honey, sauces, ready meals or dips; or if you use paint, varnish, shampoo, shaving gel, cosmetics, toothpaste, washing up liquid or other household product, then the chances are you’ve drunk, eaten or used something that’s been “pigged”. In other words, pigging has been used at some point during its processing or production.

Why Do Companies Use Pigging?

Pigging has many benefits, but its basic purpose is to remove or recover residual liquid that remains in a pipeline or tubing after liquid has been transferred from one location to another. The main reasons organisations in process industries use it is to recover product, which increases yields and reduces waste. Process industries also use pigging to clean the inside of pipes and tubing, transfer liquids, reduce the use of cleaning fluids, use less water, save time, improve process efficiency and ultimately increase profits. In addition, because pigging saves resources, product and time, it also helps towards sustainability.

Pigging in Industrial Processes

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 (here’s a blog article which explains these differences).

Here’s a typical example to illustrate why many industrial processes use pigging. pigging system components

A company that manufactures say paint needs to change the type or colour of paint it processes several times a day (while using the same pipeline). When changing from one type of paint to another, there will always be paint remaining in the pipeline or tubing from the previous run. This is because some of the paint will cling to the walls or remain in other areas of the pipe. It is important that all this previous product is removed prior to changeover. It has to be removed to prevent contamination of the next product. More importantly, it’s perfectly usable product, so if it’s flushed away, it’s wasted rather than being processed, packaged or sold. Flushing good product away is bad for sustainability and the environment, expensive, and incurs disposal costs.

Without a pigging process, the pipe or tube would typically be flushed through using water or other cleaning fluid (and some cleaning fluids are highly toxic). Not only does this take time, labour and uses a lot of water and cleaning fluid, it results in the fluid that stayed in the pipe being flushed to waste. Pigging saves this product in useable form. HPS pigs typically recover up to 99.5% of product!

We’ve used paint here just as an example. However, it’s by no means limited to paint – 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 and pet food production.

While pigging is used in a wide variety of different industries and sectors to achieve different results and goals, they mainly centre on product recovery, product transfer, sustainability and operational efficiency. For further examples, please take a look at our pigging system case studies.

How Pigging Works

In its simplest form, a pigging system consists of a solid projectile or plug (the ‘pig’) with a diameter slightly larger than the pipeline or tubing that is transporting the liquid. The pigging process introduces this pig into the pipeline and pushes it through the pipe. Sometimes it is introduced manually but more commonly automatically. Pigs are introduced, housed and returned using pig launchers and pig receivers. After pigging, liquid is then collected or continues being processed.

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. To see a video of how fast a pig travels through a pipeline or tube, please click the image opposite (this opens a new window). Note 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!

Parts and Components of Pigging Systems

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 in to 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.

Further Information

Pigs are dense objects working in pressurised systems that travel through pipes at high speed.  So, pigging system safety must be given the highest priority to mitigate and minimise risks. There are many physical, electronic and procedural safety measures you can put in place to do this. The most important is to use an experienced provider like HPS . Our systems have exceptionally high levels of safety and an excellent track record.

Although the principles of pigging are fairly straightforward, it takes many years of experience and high levels of expertise to successfully design, implement and commission an effective pigging system. That’s why, if you’re considering a pigging solution for your company, you should always work with a specialist company such as HPS Product Recovery Solutions.

To Find Out More About Pigging:

You may also be interested in some other definitions of pigging.

Got a Question? Please Ask!

Contact our friendly, knowledgeable team today!

E: info@hps-pigging.com T: +44 (0) 115 925 4700

Case Studies

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Soft Drinks Manufacturer Central America
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Croda Singapore
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Log House Foods United States
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pigging confectionery production Confectionery Manufacturer UK