hps pig being put in housing

How Pigging Has Developed Over the Years

Pigging (also referred to as liquid product recovery) is a well-established technology. It was originally developed for cleaning large diameter pipelines in the oil and gas industry.


Over time, the technology has advanced from basic equipment used to clean oil pipes to advanced, fully automated pigging systems widely used today for recovering product from smaller scale pipelines.

Although pigging is still very much used in the oil and gas industry, the technology is now split into two branches: pigging systems for the process industries such as food, beverages, paint, cosmetics, personal care or household products, and those in the utility industries such as oil, water, waste and sometimes gas.

From honey, soft drinks, sauces, wines, and cosmetics to pet food, shampoo, paints, and household cleaners, the basic purpose of pigging used in process industries is to recover or remove residual liquid that remains in process system pipelines after liquid has been transferred from one location to another.

Although pigging is in wide use in the process industries (with its use increasing), there are still alternative technologies out there. This blog article looks at some of the alternative pipeline cleaning technology and product recovery systems to pigging in process and hygienic applications, including air pigging, ice pigging, washing flushing, air purging plus more. It also looks at how traditional hygienic pipeline pigging compares to the alternatives.

Pigging system food and beverage plant

Alternative Product Recovery ‘Pigging’ Technologies

Air Pigging

Air pigging (sometimes called vortex or whirlwind systems) refers to the method of using air to recover and clear the product remaining in the pipelines. It does not use a projectile, just air. So it must not be confused with the systems that push an actual pig with air,

Air pigging is a multi-stage process, usually consisting of four different phases.

The air pigging sequence begins with a laminar airflow circulating the pipelines. Following this, a whirlwind is produced that clears some of the remaining product from the pipes. The next stage typically involves cleaning agents or water being injected into the air vortex. At the end of the sequence, an air vortex removes the cleaning agents and water and at the same time dries and cleans the process piping system. In this way, air pigging can be used as an alternative to a clean in place (CIP) system.

Air pigging technology can be easily implemented into existing production plants. At the same time, the patented technology can reduce water consumption.

You might be surprised, but HPS does not supply air pigging systems.

Why? Because in comparison to traditional pipeline projectile pigging, recovery rates are low. Typically, air pigging recovers between 60-80% of the product. Depending on the application, this figure can sometimes be even less. At the same time, air pigging is not suited to products with certain viscosities, which makes its applications limited.

By contrast, HPS systems which push a projectile, whether they use air, another gas, water or other medium, have much higher product recovery rates usually over 99.5%.

HPS process pigs

Ice Pigging

Ice pigging refers to the method of using ice slurry, instead of using a solid projectile or plug (the ‘pig’) to clean the pipelines.

The technology works by pumping ice slurry into a pipe. This is then forced along inside in order to remove sediments and unwanted deposits. Ice pigging is particularly effective in large-scale utility applications such as those used by water and sewage companies. However, in hygienic and process pigging applications, its uses are limited.

First, ice pigging is much less effective at recovering product from process pipelines in comparison to projectile pigging. HPS pigging solutions recover up to 99.5% of product from pipes, leaving less than 1% remaining in the line. However, ice pigging leaves upwards of 10% of product in the pipe.

It’s also less efficient than traditional pigging, requiring a large machine to constantly freeze the ice, which makes it expensive to run. Also, ice pigging uses large amounts of water to create the ice, so the environmental impact is significant. This also makes it unsuitable for certain products such as chocolate, which cannot come into contact with water during the production process.

Another disadvantage of ice pigging is that the ice slurry is extremely difficult to detect, making automation/PLC control challenging. Product seeps into the ice slurry so there’s significant bypass, plus the ice melts in the line which can be problematic as it dilutes the processed product and water. That’s why after an early flurry of interest, it is rarely used in process applications.

Non-Pigging Methods of Removing Product from Pipelines

 Air Purge

Air purging is a technique which uses compressed air to purge out the product from the pipelines. This technique is most suited to small-bore piping which carries low-value products.

Although air purging can be easily implemented into production plants, its effectiveness is limited because of its low recovery rates.

As an example, HPS implemented a pigging system for a beverage manufacturer that was previously using air purging. Before the new HPS pigging system, the customer was only achieving 10% product recovery rates using air purge. As a comparison, HPS pigging systems typically recover up to 99.5% of product from full process pipelines.

Water Flushing

In hygiene critical industries such as food, beverage, dairy, and pharmaceutical, water flushing is frequently used to remove the product from the pipelines, as part of the CIP process. This process wastes significant amounts of product and water and can be extremely time-consuming, particularly older and existing CIP systems.

It can also result in a lot of wasted heat and energy and significant effluent discharge issues, making this method extremely costly and the environmental impact significant. The CIP operation also takes between 60-90 minutes, which means lost production and downtime.

However, combining CIP and projectile pigging offers significant benefits to process efficiency and productivity. Not only does pigging before CIP reduce water usage, but it also speeds up the CIP process, decreases flush waste, reduces the use of cleaning fluids and increases product yields.

Other Applications

HPS has been in business for more than two decades, so we’ve come across quite a lot of methods over the years for removing product from pipelines.

For example, we were recently approached by a chemical manufacturer to install a pigging system for their resin process line. They were previously throwing away the pipelines after using them! This was because the product was extremely sticky and if it dropped below a certain temperature, the product turned hard. This resulted in them having to dismantle the pipework and get rid of it, which was extremely costly.

They are now able to easily recover this product and clean the line at the same time with an HPS pigging system.

hps pig being put in housing

Why You Should Choose Traditional Hygienic Pipeline Pigging?

Although there are lots of ways to clear the pipeline at the end of a batch, they have differing degrees of effectiveness in process and hygienic applications.

One of the best ways to increase yields, reduce waste, prevent cross-contamination and improve efficiency and productivity in liquid processing is to use traditional hygienic pipeline pigging. And HPS are the world’s leading experts.

We’ve mentioned previously that traditional pigging achieves the highest product recovery rates. But, did you also know that pigging that uses solid pigs reduces water usage, speeds up changeovers, reduces CIP times, reduces effluent and chemical waste and has a positive impact on the environment?  In this way, pigging can deliver significant savings to your organisation, providing a rapid payback and high return on investment (ROI).

HPS pipeline pigs, in particular, are made from a flexible, hardwearing material and can easily travel around 1.5 D bends while maintaining full body contact. HPS pigs (and HPS pigging technology) are unmatched in performance, durability, efficiency, and reliability. Here’s a pigging system demonstration video, showing an HPS pigging system removing residual liquid from the pipeline.

So, if you are thinking of implementing a pigging system, then make sure you speak to process system experts such as HPS. Then, you can have peace of mind that you’ll get a practical, efficient and cost-effective solution – that works and delivers results!

Find Out More

Thanks for reading our blog about alternatives to traditional pipeline pigging. If you have any questions about hygienic pipeline pigging and product recovery systems, for a free consultation, a free pigging quotation or to find out more about how you can transform your processing operations, please contact HPS!

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