Water is a valuable and limited resource. With increasing periods of drought and controversies over water rights, this fact has only become clearer. The freshwater consumption of industrial companies is under constant scrutiny. Pigging of product-carrying pipelines, a well-established method, supports water savings during pipe cleaning and minimizes product loss in liquid processes, enabling companies to achieve more sustainable production and more consistently.

Every drop counts

Research institutes and environmental associations have sounded the alarm for years: fresh water is becoming compromised and more difficult to access at a rate that nature, including humans, are finding difficult to cope with. In 2018 the United Nations proclaimed the “UN Water Action Decade” to shed light on the importance of protecting freshwater systems from overuse and the effects of environmental and climate changes. Today, the mantra: “Every drop counts” is heard along Asia’s Mekong River, where low water threatens vital natural and economic cycles, all the way to central Germany, where the effects of drought are more visible each year.

Fresh water, including the volumes required by industrial manufacturers, is obtained directly from groundwater sources or via water suppliers. Depending on the geological conditions, fresh water takes years, even centuries, to accumulate. Water is also drawn from river systems, which unfortunately, are fed less and less consistently by rain and glaciers. As a result, many companies are taking steps to conserve water, which has become an increasingly important issue for customers and society in general.

Reducing the water required for cleaning in liquid processing applications

Where liquids are processed - recover the value – reduce the waste

In many industries, liquids are processed in large quantities, for example in milk processing or the production of cosmetics. Already a proven technology across several applications, product recovery or pigging systems have become an important tool in helping companies conserve water by ensuring that raw materials are processed with minimal waste and by optimizing water consumption in demanding pipe cleaning processes. This also reduces resource-usage for wastewater treatment.

It’s all about the pig

The integral component in any product recovery system is the pig or scraper – a movable plug that was developed and first used in the oil and gas industry to monitor pipelines. Equipped with sensors, the pig takes controlled measurements as it moves through the section of pipeline being examined.

As liquid processing technology became more advanced, this solution was gradually adopted for batch processing systems. During the processing of dairy products, beverages, liquid foods and personal care products, a hygienic pig or plug is often used to push valuable product residue out before pipe cleaning takes place. As a result, more valuable product remains in the process instead of being lost with the wastewater.

The pig is propelled through the respective pipe section by either air, water, carbon dioxide or nitrogen and then back to its waiting position before the initial flushing of the pipe. Made of plastic, the pig creates a tight seal between itself and the pipe interior. This step considerably reduces the amount of rinsing water required, which therefore leads to significant savings in freshwater withdrawals when you consider how much water is required in making hygienic products like yogurt, smoothies or skincare creams. In most cases, the product media flows through a piped system that is virtually free of dead space, is closed off from the ambient and is subjected to regular cleaning-in-place or sterilization-in-place cycles, cleaning, and where necessary, sterilizing, all surfaces without leaving behind any residue before the next product batch. However, prior to this, the bulk of any remaining product residue is expelled or rinsed out first.

GEA VARICOVER® components

Water consumption varies tremendously from plant to plant. While the potential of product recovery technology is far from exhausted, the ability to make ecological improvements depends greatly on the product and plant design. “The more viscous the product, like yoghurt, for example, the longer the piggable pipe section and the more recovery potential you have. This translates into less water consumption,” explains Christian Blecken, Head of System and Application Support at GEA’s Competence Center for Hygienic Product Recovery Systems in Büchen, Germany. “Likewise, the frequency of batch changes for which the pig can be used also plays a role,” he adds.

The more viscous the product and the longer the piggable pipe section, the more recovery and greater the savings in water consumption.”- Christian Blecken, Head of System and Application Support for Hygienic Product Recovery Systems, GEA

Investing in pigging technology can pay off in the construction of new plants as well as when retrofitting existing plants; he latter accounts for roughly 20 percent of the installations executed by GEA. “The only important prerequisite,” Blecken explains, “is the pipe section, which must have a constant diameter and smooth interior surface, so the pig does not get stuck or lose its seal.” Standard pipe bends and T-connections are no problem for the pig, including the one-piece double-sphere shape which is preferred by GEA: “This smart shape has a clear advantage given the pig does not have to flex at the bend,” says Blecken.

While many companies pig their pipelines in all process stages – from the receipt of raw materials to transport to process and storage tanks to filling – there is an important guiding principle for maximizing optimization: “The closer to the filling process, the greater the purity of the product recovered,” explains Pascal Baer, GEA Product Manager for Aseptic Components. Aseptic components are necessary when processing flow media in the more contamination-sensitive hygiene classes (e.g., “UltraClean” and Aseptic”), for example, in the production of UHT milk products. And in aseptic pigging systems, all built-in valve rods are additionally sealed against the atmosphere.

Pigging systems are also available in explosion-proof versions, required for use with alcoholic products, for example. In fact, pigging technology can be used for almost any type of liquid product, giving manufacturers a lot of scope to improve the efficiency and ecological footprint of their plants.

Advanced pigging systems

The pigging process, including product processing and pipe cleaning, should take place without interfering with the closed piping system. Modern product recovery systems are equipped with an automatically operating pigging station at the beginning of each pipe section. The station holds the pig while the product, rinsing water or cleaning media flow through the pipe. In GEA pigging systems, the station housing has a wide diameter with specialized grippers and springs. These define the pig’s range of motion and ensure it remains hygienically clean as the media continuously flow around it. When the pig is in use, a pig catching station awaits it at the end of the pipe section and sends it back to its waiting position. Two valves control the necessary inflow and outflow of the propellant.

GEA VARICOVER® Product Recovery System in an international dairy processing plant

Digital technology with a future

The ongoing digitalization of process technologies means there is continual potential for improving the sustainability of plants and plant operations. Like most valve systems, today’s pigging technologies are more-or-less already integrated in automatic process sequences via centrally connected control heads. Next-generation electronic control heads enable simple, error-free setup and subsequent operation of the systems, as well as extended process control and monitoring functions. GEA VARICOVER® product recovery systems provide real-time monitoring of the pig position via magnetic sensors, with the mechanical and electronic components forming a coordinated unit based on GEA’s modular and service-friendly system, GEA VARIVENT®.

These systems enable consistent automation, simplifying the setup for processes that can be fully validated and which allow for integration in Industry 4.0 environments thanks to a modern IO-Link system control feature. Further possibilities extend to networking with the producer's ERP system for further optimizing the use of resources.

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