sponsoredLevel and Pressure Measurement Level and Pressure Sensors Monitor Highly Efficient Plastics Processes

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VEGA Grieshaber KG

Whether for the sealing of dams or as a decorative upholstery material for furniture: Plastic films as well as other plastic products from Renolit stand for maximum functionality. To ensure that this remains true in the future, the company continuously optimises its production processes. And it does this by utilising Vega sensors for level, flow and pressure.

Some companies have efficiency as part of their DNA, and that’s the case at Renolit. The manufacturer of plastic films and other plastic products is making enormous efforts to improve the efficiency and effectiveness of its production systems. This enables it to create products that are guaranteed to last longer, use fewer resources and support a closed-loop economy.

It’s worth noting that the foundation for these futuristic-sounding goals was laid back in 1946, when resources were scarcer than ever. The first person to set standards here was Jakob Müller. When he founded Renolit post-war in the town of Worms, Germany, which was plagued by shortages of all kinds, the previously successful leather goods manufacturer was forced to look for alternative materials to replace leather. His contemporaries attested to his “foresight and profound knowledge” because he not only found a practical substitute in PVC, but also used the material to penetrate other new markets. That was the birth of the first floor coverings and films “made by Renolit”.

A lot has happened since then, but the search for efficiency runs like a common thread through the company’s history. Not because the raw materials are scarce, but because there is no alternative to sustainability. The Operational Excellence (OpEx) department, which is committed to the process of continuous improvement, is a key area of the company in charting the path towards this goal. At the Worms site, Andreas Böhm is responsible for recording process and energy data, among other things. He works to maximize plant availability and sees his work as a logical consequence of the same spirit of efficiency that drove founder Jakob Müller. “If we scrutinise our processes thoroughly and go into great detail, we always come across worthwhile savings ideas,” he says.

Custom-Made Plastics

Manufactured for special applications in many cases, plastic film is a product of almost unimaginable variety. Its properties can be configured exactly according to customer requirements through the use of additives and development under carefully controlled synthesis conditions. “In this sense, we’re a manufacturer of the much-vaunted ‘batch size 1’,” explains Böhm, highlighting the flexibility of Renolit’s production processes. Renolit products are almost never purchased “off the shelf” because they are always manufactured according to what best meets the customer’s needs. Some of the end products feature pleasantly tactile embossing, some are especially hygienic, and some are so finely homogeneous that no moss can stick to them, even when used outdoors for a long time.

Because production requires highly precise dosing of the base materials, such as polymers, additives or colourants, under constant process and environmental conditions, Vega radar sensors are utilised: for example, on IBC containers, that hold the raw materials to be processed. Thanks to radar technology, precise level monitoring of such containers is made from the outside, without the plastic tank body being opened or modified.

Experienced in measurement and control technology, Andreas Böhm was actively involved in his employer’s selection of a partner for industrial measurement technology. “When I started working here in Worms 16 years ago, I already knew Vega from my previous job,” he recalls. “In my very first week here, I won a bet because I managed to get a process measurement that was always inaccurate to work reliably with a Vega radar sensor.”

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One Level Sensor for All Container Types

In Böhm’s opinion, radar level sensors are the solution of choice for many applications in this industry, as they help to deliver a perfect finished plastic product. Böhm is delighted that the Vegapuls 6X is a universal sensor that can monitor a wide variety of measuring points. In the preparation area, on the second floor of the production building, it is precisely this sensor model that immediately catches the eye, as it monitors the filling of paste. Andreas Böhm points to the mobile, 1000-litre plastic containers, which are almost one quarter full of amber-coloured liquid. Vegapuls 6X sensors are mounted near the inlet. As the containers are filled with the paste-like mass, the radar sensor transmits and receives back microwave pulses to measure the distance to the level by their transit times. By comparing the distance measurement with the calibration values, the exact level is determined. This ensures that the correct amounts are measured and filled into the vessels all times.

Procurement Has Become Much Easier

“It’s a big advantage for us,” says Böhm, “that the sensor measures both liquids in the small IBCs and bulk solids in tall bulk containers outdoors with millimeter precision.” He’s referring to 12 slender outdoor silos, each with a capacity of 200 cubic meters, which are located directly in front of the doors of Plant A. “We use the same sensors on these silos as we do on the small process tanks in the production lines,” he notes. These metal cylinders, which can be up to 23 meters high, store powdered bulk solid materials that are fed into the production process to produce plastic film using calendering machines. “Since we started using the Vegapuls 6X universally for our inventory monitoring, procurement has become much easier for us,” says Böhm, summarising the improved processes. Although the configuration and the materials in the silos vary depending on the specific product requirements, it is always important that the materials used are optimally stocked so that production runs efficiently and without interruption.

Saving Energy With Flow Measurement

But it’s not just the optimal stocking of raw materials that offers a savings potential that’s noticeable on the bottom line. “Energy metering is becoming increasingly important to us,” says Andreas Böhm, describing one of the goals of the OpEx department. He’s referring to the more than 300 meters in the PVC film production area that record all the electrical energy currently being consumed. The savings potential here is enormous: “The plastics industry is energy-intensive and we have every intention of achieving CO₂-neutral production by 2045.” With its “One Renolit 2025” strategy, the company is part of the Circular Plastics Alliance (CPA) and has committed itself to the closed-loop economy.

To save energy, they use three differential pressure transmitter Vegadif 85 pressure sensors to measure the differential pressure in the temperature control units of the calender rollers. The flow of the heating water is closely monitored to ensure the required product quality. “We use water at a maximum temperature of 200 °C to keep the process at the right temperature,” explains Böhm. This means that the process runs under optimal conditions — and the measurement also results in significant energy savings: “The precise flow measurement with Vegadif 85 guarantees that our thermal energy consumption is precisely adapted to demand.”

Sensor Replacement During the Ongoing Process

In his daily work, Andreas Böhm is also highly satisfied with the “gate valve solution” that he found together with the Vega field representative. Since the measuring instruments are each mounted with a gate valve, they can be serviced or replaced at any time without having to interrupt the process.

The special double-chamber electronics of the differential pressure measuring system offers further savings potential. With one Vegadif 85 sensor, the static pressure and the differential pressure process values can be measured simultaneously. This is a real user benefit as monitoring the static pressure is also important for optimal process flow in the calender. Thanks to the this dual output feature of Vegadif, an additional sensor is not required.

The Improvement Detectives

“This part of the plant consumes a huge amount of energy” says Andreas Böhm, “so the better we measure and regulate here, the greater our savings.” Just the addition of new software modules alone, which optimize the standby mode of all electrical devices, has reduced energy loss by 60 %. To reduce consumption even further, he leaves no stone unturned when it comes to optimizing the remaining ‘energy guzzlers’ such as cooling and heating processes. He’s convinced that “you can only achieve quality by implementing quality”. That’s why he plans to continue relying on high-quality measurement technology in the future. A technology that delivers exact, reliable measured values that show where and when the production took place, and at what temperatures and speeds, is what ultimately makes end products traceable.

“Considering all this, we can say that well-monitored processes are, above all, one thing,” says Böhm emphatically: “Customer friendly”. Traceability and reproducibility are key factors for users of Renolit products. And the fact that the manufacturing processes are also low-emission and often even plastic-neutral is, of course, a highly welcome side benefit.

Meet the Vega experts at Achema 2024 in Frankfurt a. Main (10.-14.6.): Hall 11.1, Booth C63.

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