Is Your Company “Pigging”?

Product recovery, often referred to as “pigging”, is widely used in the beverage industry. It’s one of the most effective ways to increase yields, reduce waste, save water and cleaning agents and reduce processing time. And its use is increasing.

Pigging is used during the manufacture, processing, packaging and bottling of a wide range of beverages. It’s used with ingredients such as pulps and sugar syrups, right through to products at their final stages of processing, including wines, spirits, soft drinks, juices and so on.

Put simply, pigging uses a special projectile to recover the liquid product that’s left in pipelines during changeovers. It delivers a broad variety of benefits and gives high return on investment. A new pigging solution will also pay for itself quickly. In most cases, payback is less than a year.

Beverage manufacturers use pigging for a variety of reasons. The most common reason is to recover residual liquid from the inside of process pipelines.

Instead of disposing of it as would be expected of conventional procedure, pigging allows the recovered product to continue to be processed, bottled, canned or stored. This increases yields significantly, and this is one of the main reasons why pigging systems deliver a high return on investment.

In general, the longer the pipework, the more frequent the changeovers or the more valuable the product, and the more there is for beverage processors to gain from pigging.

As well as increasing yields and reducing flush waste, beverage manufacturers use pigging because it lowers the use of cleaning agents, chemicals and water. Because of this, they save on the direct cost of these products, as well as their associated transportation and disposal costs.

At the same time, because it provides a big reduction in overall waste, pigging improves the environmental sustainability of companies using it.

There are other reasons beverage companies use pigging. For example, some liquids tend to foam; others instead must not come in to contact with air—such as wine.

In cases like these, beverage manufacturers will often use specialist ‘double-pig’ systems. Double-pig systems prevent aeration, foaming, dissolved oxygen and contamination.

In beverage manufacture, pigging works by sending a specially designed projectile through a pipeline. The projectile, called a ‘pig’, is an interference fit. As the pig travels through the pipeline, very little liquid can get past it. So, the pig safely transfers the liquid to its destination.

Using hygienic (often called sanitary) pigs made of food-grade materials prevents contamination or tainting of the product. This means the liquid, which could be the end beverage or one of its ingredients, remains in pristine condition. It can therefore continue to be processed in the same way as the main bulk of the product.

Pigging systems are usually permanent installations and an integral part of the operating plant. Pigs are propelled by filtered air, nitrogen or carbon dioxide, or sometimes water or other liquid.

Today, most pigging systems are automated, which improves efficiency and reduces the chances of human error.

While it’s common to deploy a pigging system when a new facility is being built, it’s also common to retro fit pigging systems on to existing processing pipelines and equipment.

Because nearly every processing plant is different, so is nearly every pigging system. Each tends to be designed around the precise needs, aims and objectives of the individual beverage manufacturer.

Pigging technology has been around for some time. It was developed in the oil industry in the first half of the 20th century. There is some speculation about how the name ‘pigging’ came about. One of the common reasons quoted is that a group of pipeline engineers put a crude projectile down a pipeline to clean it. As the projectile travelled through the pipeline, it made a squealing noise; like a pig!

That’s a great story. But of course, modern pigs used in the beverage industry today don’t squeal. In fact, they hardly make any sound at all.

There are other suggestions about how pigging got its name. One is that PIG is an acronym for ‘pipeline inspection gauge’ or ‘pipeline inspection gadget’. In the beverage industry, most pigs don’t inspect anything. They are purely used to transfer liquid or recover product.

There are other names for pigs. Sometimes they’re called ‘moles’, cleaners or scrapers. But it’s ‘pig’ that’s the most popular. And just to confuse things further, the phrases ‘product recovery system’ and ‘pigging system’ are often used interchangeably!

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

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.

Pigs used in beverage processing come in a variety of shapes, sizes and materials. The key features to look for when choosing a pig are high product recovery rates (typically these should be over 99 percent), as well as reliability (they should come with a minimum usage guarantee) and of course safety. If used with beverages, pigs must be manufactured from food-grade, FDA compliant materials.

While the shape of some pigs may look simple, they are usually quite sophisticated devices. Their designs have been refined and developed over the years to become the highperformance products of today.

Modern pigs achieve extremely high product recovery rates. They are often bi-directional and usually controlled automatically. They can negotiate a variety of bends and curves, work with many different types and viscosity of liquid, and last for an extremely long time without need of replacement.

To enable automation and control, pigs need to be detectable. This is usually achieved using magnetism and associated detection devices. However, it’s important that pigs do not contain solid magnets. This is because solid magnets can shatter, which compromises the safety of people and equipment. It also risks product contamination.

The safest and most reliable pigs do not contain solid magnets. Instead, they have a silicon-based flexible magnetised core. In this design of pig, there’s none of the potentially dangerous solid magnetic material to shatter and cause problems.

Similarly, pigs should be of one-piece design and not made up of assembled parts. This is again to avoid potential safety issues. Assembled pigs are more likely to break apart during use.

Pigs need to be flexible. This is so they can maintain full contact when travelling around pipeline bends. This in turn means they will recover the maximum amount of product left in the pipeline.

To avoid product bypass, along with the increased likelihood of rips, tears or breakages, it’s best to avoid pigs that have fins or complex shapes. Usually, a cylindrical style shape gives the highest levels of performance. It also avoids the reliability, safety and performance problems associated with fins or the more intricate shapes of pig.

Because pigs travel through pipelines at speed, safety is of the utmost importance. As well as using the safest type of pig, a pigging systems specialist will also incorporate a variety of other safety features in their designs. These measures are to protect people, equipment and product.

While each pigging project is different, safety features will often include special guards, blocking mechanisms, electrical and mechanical interlocks and depressurisation sequences.

Although most serious pigging accidents have been confined to large scale equipment used in oil and gas pipelines, that’s no reason to be complacent. As well as including safety features within beverage pigging system designs, training, awareness and strong operational procedures are also important.

Safety must be the highest priority. One way of ensuring this is to use an experienced product recovery specialist to design, implement and commission your pigging system.

The principle of pigging, that is, sending a tight-fitting projectile through a pipeline to force out residual product, is straightforward. However, to design an effective pigging system for beverage processing needs extensive expertise and experience.

There’s a lot to take in to account. Length and diameter of pipeline, pipeline material, type of propellant, viscosity of the liquid or liquids, pumping pressures, temperatures, types of couplings, number of sources and destinations, whether the product needs protection from air, whether it tends to foam, the number and frequency of changeovers, types of valves used, and more.

If you’re deploying a pigging system on existing processing equipment, one of the most important factors is your pipeline infrastructure, which must be in good condition. In beverage production, pipework needs to be in good condition anyway, so this is not usually problematic.

Before installation, it’s important to check all welds are clean, sound, and do not intrude into the internal bore of the pipeline. Similarly, your pipeline should not have any dents, leaks or damage.

There are also different types of pigging systems for different applications. These include single-pig, double-pig, and multi-tank tank drop-off, for example. In addition, because most pigging systems are automated, there are programming and software considerations to take in to account as well.

A pigging system is an important investment. Get it right, and the benefits will be substantial. It will deliver rapid payback, high return on investment, a clear increase in profitability and improved sustainability. But, like any capital investment, you need to make sure you choose the right supplier.

There’s no such thing as an ‘off the shelf’ pigging system. Your chosen provider must be able to understand your processes and advise on the most appropriate solution tailored to your needs.

What’s more, a pigging system is more than just a selection of components. There’s design, implementation, software or coding, commissioning, training, ongoing support and customer care.

Choosing a pigging system from a specialist in product recovery and liquid transfer, with a long history and proven credentials, will go a long way to helping ensure the success of your project.