Water is a valuable and limited resource. In the age of climate change, with increasing periods of drought and controversies over water rights, this fact is becoming clearer and clearer. The freshwater consumption of industrial companies is constantly under scrutiny. A traditional method, the pigging of product-carrying pipelines, enables sustainable water savings during pipe cleaning and the minimization of product losses in liquid processes. In this way, companies are able to realize “green” production methods more consistently.
Every drop counts
Research institutes and environmental associations have been sounding the alarm for a long time: fresh water is becoming scarcer than nature and humans can cope with in the future. In 2018 the United Nations proclaimed the “UN Water Action Decade” for 2018 in order to protect freshwater systems from overuse and from the effects of environmental and climate change. The catchphrase “Every drop counts” is echoed today on the Mekong, where low water threatens important natural and economic cycles, as well as in central Germany, where drought damage is becoming more visible each year. Industrial companies inevitably need water. Fresh water is obtained directly or via water suppliers from the groundwater, which, depending on geological conditions, has to accumulate over years or even centuries, or from the river systems, which are fed more and more unevenly by rain and glaciers. Many companies are already committed to conserving water, and customers and the public are increasingly putting pressure on others.
Saving cleaning water in liquid processing
Where liquids are processed in large quantities, e.g. in the milk processing industry or in the manufacture of cosmetics, a proven technology – so-called product recovery systems or pigging systems – is gaining in importance for companies. These systems ensure that raw materials are processed with minimal waste, but they also optimize water consumption in demanding pipe cleaning processes, thus helping to relieve wastewater treatment and protect freshwater resources.
The trick with the plug
The star of the product recovery systems is the so-called pig or scraper, a movable plug that was originally developed to monitor oil and gas pipelines. Equipped with sensors for control measurements, the pig is moved through the pipeline section to be examined.
As liquid processing technology advanced, this principle gradually entered the field of batch processing systems. When processing dairy products, beverages, liquid food or care products, the pig is often used as a hygienically clean plug to push out valuable product residues before pipes are cleaned. As a result, more quality product remains in the process instead of being lost with the wastewater.
The pig is moved by a propellant – air, water, carbon dioxide or nitrogen – through the respective pipe section and back to its waiting position before the initial flushing of the pipe. It is made of several elastic plastics that seal the pipe well.
The fact that this additional step also considerably reduces the amount of rinsing water subsequently required is proving an important step forward for the ecologically sustainable use of fresh water. After all, a lot of water is needed to produce liquid products such as yogurt, smoothies or skin care cremes in the required hygienic quality. In most cases, the processing media flow through pipe systems that are completely closed to the outside, as free of dead space as possible and with regular CIP / SIP cycles (Cleaning In Place / Sterilization In Place) in order to clean and (where necessary) sterilize all product-wetted surfaces without leaving any residue before the next product batch. Prior to this, however, the major share of remaining product residues must be expelled or – less resource-friendly – rinsed out each time.
Depending on how advanced a plant is in performing these and other processes, there are great differences in water consumption from plant to plant. While the possibilities of product recovery technology are far from exhausted, the ecological improvement potentials vary depending on the product and plant design. “The more viscous the product, e.g. yogurt, and the longer the piggable pipe section, the more recovery and the greater the savings in water consumption,” is the formula put forward by Christian Blecken, responsible for System and Application Support at the GEA Competence Center for Hygienic Product Recovery Systems in Büchen. The frequency of batch changes for which the pig can be used also plays a role.
The more viscous the product and the longer the piggable pipe section, the more recovery and the greater the savings in water consumption.”- Christian Blecken, System and Application Support for Hygienic Product Recovery Systems
The investment in pigging technology can pay off in the construction of new plants, but also in the retrofitting of existing plants – the latter account for about 20 percent of the installations executed by GEA. Christian Blecken explains the prerequisites: “The only important thing is that the pipe section has a constant diameter and has no internals so that the pig does not get stuck or lose its sealing effect.” In contrast, ordinary pipe bends and T-connections are no problem for the pig, especially not in the one-piece double-sphere shape preferred by GEA: “This smart shape has the advantage that the pig does not even have to flex in the bend,” as Christian Blecken is pleased to say.
Quite a few companies pig their pipelines in all process stages, from the receipt of raw materials to transport to process and storage tanks to filling. Here too, there is a guiding principle for the optimization potential: “The closer to the filling process, the nobler the product to be recovered,” as Pascal Baer, the GEA product manager responsible for aseptic components in Kirchberg, Switzerland, explains. Aseptic components are necessary when processing flow media in the more contamination-sensitive hygiene classes UltraClean and Aseptic, e.g. UHT milk products. In aseptic pigging systems, for example, all built-in valve rods are additionally sealed against the atmosphere.
Pigging systems are also available in explosion-proof versions, as in alcoholic products. Thus, pigging technology can be used for almost any type of liquid product, setting no limits for companies and plants to improve ecological operation.
Advanced pigging systems
The pigging process, like the product processing and pipe cleaning processes, should take place without interfering with the closed piping system. To this end, modern product recovery systems are equipped with an automatically operating pigging station at the beginning of each pipe section. The station holds the pig during the time that product, rinsing water or cleaning media are flowing through the pipe. In GEA pigging systems, the station housing features a wider diameter and special grippers and springs. These give the pig a defined range of motion and keep it 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.
Digital technology with a future
Considerable additional optimization potential for sustainable plant technology lies in the advancing, ongoing digitalization of all process technologies. Like most valve systems, pigging technology today is already generally integrated into automatic process sequences via centrally connected control heads. Electronic control heads of the latest generation enable an increasingly simple, error-free setup and operation of the systems as well as extended process control and monitoring functions. The modern GEA VARICOVER® product recovery systems provide real-time monitoring of the pig position via magnetic sensors. Their mechanical and electronic components form a coordinated unit based on the combination- and service-friendly GEA VARIVENT® modular system.
Consistent automation, made possible with these systems, simplifies the setup for fully validatable processes and enables with a modern IO-Link system control the early integration into Industry 4.0 environments. The possibilities extend to networking with the company's ERP system for optimized use of resources.