Seli conductivity at Gropper dairy

As a private label specialist, Molkerei Gropper GmbH & Co. KG produces milk products, not-from-concentrate juices and smoothies for trading companies throughout Europe. Founded in 1929 as a regional dairy, today Gropper is a medium-sized company in the food industry with quality and innovation.

With a total turnover of 719 million euros and over 1400 employees at three locations, Gropper stands for constant growth and continuous expansion.

The Gropper company combines its economic and ecological goals and thus shows a high degree of responsible entrepreneurial action. In addition to sustainable products, the focus is also on the use of low-emission raw materials and packaging. In production, the main concern is the protection of resources, raw materials, the environment and climate, energy management and the efficient use of energy. In order to better achieve these goals, Gropper relies, among other things, on the use of analytical measurement technology from Seli in various areas of production.

TIGHT AND DURABLE
The new conductivity sensor SLI03 convinces - as successful installations in the Gropper dairy shows - with its compact construction, high level of robustness, hygienic design, modular process connections and the easy-to-use operating concept. The special double-seal concept makes the SLI03 a hermetically sealed measuring system with exceptional availability and service life.

The SLI03 is an inductive conductivity measuring system that takes into account the special practical requirements in dairies, breweries and other food processing and beverage bottling plants, especially in connection with cleaning in place processes (CIP). Many features underline the consistent design for the longest possible, trouble-free service life in the harsh operating environment, e.g. the selection of materials, the hygienic design of the sensor, the modular process connection technology, special design measures and test methods for the best possible tightness and protection classes up to IP69K.

Operating environment has special requirements
Conductivity measuring systems are used to measure different phases – e.g. B. water, alkalis or acids - to be reliably detected and separated via their different electrical conductivity / concentration. With the help of phase separation, the plant operators want to optimize production processes and the effectiveness of the cleaning medium in cleaning cycles, reduce product losses and waste water pollution, increase plant productivity and achieve maximum operational reliability and reliability. In practice, conductivity measuring systems - like other process sensors - are usually exposed to special conditions, e.g. B. high pressures, changing temperatures and different chemical medium properties. So far, this has repeatedly led to performance problems.

Users report "leaking sensors in which moisture forms", "heavy loads on the housing and sealing materials", "numerous failures at high or strongly fluctuating process or ambient temperatures" and the need to "remove the sensors frequently to have to exchange". If the actual sensor replacement is already detrimental to the availability of the systems, many users also complain about the "often complicated operation and setting" of the devices. When developing the SLI03, Seli took these factors into account and developed a sensor solution that eliminates these disadvantages - and fulfills the desire for perfect performance in the applications. Due to the very fast response behavior of the devices, product losses and the time for the correct process statement are optimized. This gives enormous potential for savings.

Inductive conductivity measurement: Ideal - because media-independent - operating principle
The SLI03 uses the inductive operating principle to measure the conductivity or the concentration of liquid media and mixtures. The sensor works in situ, i. H. directly in the process channel (inline). It has two coils – an oscillator (transmitter) and a receiver coil, whose primary windings in the sensor head are both surrounded by the medium to be measured.

An alternating current flows in the oscillator and generates a magnetic field in its environment that induces the flow of current into the measuring medium that is necessary for the measurement. The current flowing or the ions it contains generate an electric current in the receiver coil that differs from the original excitation current in terms of strength and voltage. This deviation is used electronically in the SLI03 transmitter to determine the conductivity of the medium, i. H. the sensor measures the conductivity in siemens per centimeter or the concentration in percent. In contrast to conductive measuring systems, the induction coils do not come into direct contact with the medium - which means that the SLI03 can also be used to measure in concentrated acids or alkalis. A total of 14 possible basic measuring ranges for conductivity measurement can be called up via the display of the SLI03. The optional SELISOFT parameterization software also offers the option of freely setting additional measuring ranges. The reproducibility of the conductivity measurement is < 1% of the measured value, the long-term stability is +/-5% of the full scale value. The measured values are output as 4...20 mA analogue signals.

Built-in fastest temperature compensation ensures accurate Messwerte
Since the conductivity of a medium depends very much on its temperature, Seli has integrated extremely fast and reliable temperature compensation into the SLI03. The sensor for aqueous media is set at the factory with a reference temperature of 25 °C. This can be adjusted accordingly by the user if required. Since many media show an almost linear temperature behavior over a large temperature range, the linear temperature coefficient automatically calculated by the sensor as a measure of the percentage change in conductivity per Kelvin is sufficient for normalizing the conductivity to the respective reference temperature. If required, non-linear temperature compensation, e.g. B. as a 4th order polynomial. For the temperature, too, the SLI03 offers the option of choosing between seven different basic measuring ranges or setting other measuring ranges freely with the help of SELISOFT.

The resolution of the temperature measurement is 0.1 °C; the repeatability is specified as 0.2% of the full scale value.

Compact, robust and hygienic design
The SLI03 offers a compact, space-saving and user-friendly design - and is currently probably the smallest device of its kind on the market. The mechanical structure is very stable in view of the demanding operating conditions. At the same time, the modularity of the housing, process connection and sensor element enables the technically and economically efficient configuration of the sensor for a wide range of application solutions. The choice of materials is based on the desire for maximum durability and hygiene. The sensor housing as well as the pressure screw and the process connection are made of stainless steel 1.4305, which meets the increased requirements for corrosion resistance. The housing is also consistently hygienic: it has no dead spaces or gaps in which bacteria or microorganisms could nest.

When cleaning or disinfecting a system, the smooth, rounded edges and the easy-to-clean geometry of the sensor ensure that cleaning and disinfecting agents run off optimally after they have had an effect and that no pockets of residue can form. The sensor tip consists of PEEK (for: polyetheretherketone) and extremely resistant stainless steel 1.4404 / AISI 316L. The high-temperature-resistant PEEK is resistant to almost all organic and inorganic chemicals - acids, alkalis, oils and alcohols - and also impresses with its excellent mechanical strength. The low-carbon stainless steel 1.4404 / AISI 316L has excellent resistance to media containing chlorine, e.g. B. Hypochlorite-based disinfectants or chlorinated alkaline cleaners whose oxidative components have a greater effect on materials.

Overall, both the sensor design and the choice of materials are consistently designed for the environment of hygienic production in accordance with the rules of the EHEDG (European Hygienic Engineering & Design Group). Certification is in preparation – the SLI03 complies with Regulation (EC) No. 1935/2004 on materials and objects intended to come into contact with food.

Tightness means durability
Based on the experience of numerous users, Seli placed particular value on the tightness feature when developing the new SLI03 conductivity measuring system. On the one hand, this is expressed by the minimized volume of the sensor housing, which reduces the potential condensation surface. In addition, the integrated, miniaturized electronics of the sensor are completely encapsulated - which protects against moisture and mechanical damage in equal measure. Finally, Seli has developed a special double-seal concept that is suitable for use in the wet area of food, beverage and pharmaceutical production and that is subject to constant test cycles with changing loads, e.g. B. temperature fluctuations, different pressure conditions, cold shocks, artificial aging and mechanical shock and vibration is continuously improved.

Hermetically sealed - confirmed by helium tests
How successful the sealing concept is is proven both in the test field and in practice. In order to check the SLI03, but also the process fittings and turbidity sensors in the product range, for leaks and tightness, Seli uses high-precision helium leak test devices to check for leaks. By detecting the test gas helium, which is applied to the sensor from the outside or inside, depending on the measurement process, even the finest holes and pores in walls and housing materials can be detected and quantitative statements can be made about leaks or leaks. In contrast to hydrostatic methods - keyword "water hose method" - the helium test is much more precise: If an air bubble forms on the test object every 30 seconds during the water test, this corresponds to a leak rate of 10-4 mbar l/s. In comparison, Seli achieves dramatically better tightness values: The standard test criterion is specified for a leak rate of 10-8 mbar l/s - i. H. theoretically, an air bubble only forms every 83 (!) hours.

Positive statement from the Gropper dairy
This exceptional tightness was confirmed in field tests as well as in actual system installations. Mr. Bernd Oefele from the Gropper dairy uses the SLI03 sensors in the cleaning systems and to monitor the cooling tower water. He reports "reliable, failure-free operation" - and that he has included these conductivity measuring systems as a standard in the equipment regulations.

Commissioning was very easy, and thanks to the modular process connections, the sensors could be integrated into the system within a few minutes. A robust and compact design, a bright, easy-to-read display and simple operation without a manual helps the entire team when commissioning the devices and saves time.

Particularly noteworthy is the conductor loop set, with which the hardware of the devices can be checked and documented using the free seli software (selisoft). Furthermore, the simple, integrated TC value determination and calculation enables quick commissioning and the most accurate measuring method without deviation.

Modularity, operation, tightness, hygienic design - the conductivity measuring system SLI03 is breaking new ground in many respects. And it sets new standards when it comes to saving resources and raw materials, the environment and climate, energy management and the efficient use of energy!

These very innovative ideas have meanwhile been integrated and implemented in all newly developed Seli systems. The positive operating experiences of users in the food and beverage industry suggest that this path could develop into a fast lane...