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Capacitance Level Measurement in Tomato Paste Production

Measuring sensors working with the capacitive principle are the all-rounders among limit switches because they have the highest application performance in the basic version.

They can be found in overfill protection as well as demand and empty indicators in process or storage vessels as well as in leakage monitoring and interface detection and can be used in all tank types and shapes, regardless of whether the vessels are metallic or non-metallic. Due to their high sensitivity, their compactness and the variety of booms, they are particularly suitable for the different process requirements of the nutrition industry. A well-known manufacturer of different foods within the Latin American markets implemented the capacitance level indicator Capanivo® from UWT GmbH for his tomato paste container at the Lima location.

For full detection the CN 7000 series was applied, which has process connection made of stainless steel and PPS probe (Polyphenylene Sulfide), a hygienic plastic, chemically compatible with aggressive applications for the cleaning process. The probe is only 98mm long, so it is suitable for installation in very small spaces. In addition, the IP68 housing is made of polyester and polycarbonate, thus environmentally resistant and properly sealed. An important highlight is that this sensor works with two wire electronics and has “Tip sensitivity” technology providing high accuracy in the detection adjustment, even with the very sticky tomato paste the solution could manage to provide the right signal output.

Precise media detection with two wire electronics and “Tip sensitivity”

Tomatoes first had to find their way to us across the ocean as they originally come from South and Central America. Especially the well-known wild forms that are from the South American Andes, today includes parts of Peru, Bolivia and Ecuador. Peru’s tomato exports rose by around 60% within the past year. The total production of Peru, which amounts to around 100,000 mT, is mainly grown in the desert valley of Ica, 250 km south of Lima. The agricultural conditions are among the most demanding in the region due to difficult weather conditions. One of the leading Peruvian food companies with more than 40 years of experience providing different food products was looking after a smart way to modernize the level measurement technology of his production facilities at his headquarter in Lima. Since its inception, it has been involved in the production of tomato based products such as pastes, sauces and passatas as well as flour and pasta. Further product categories are candies such as toffee, gummy bears, waffles, cookies and chocolates. Especially for a compatible level measurement solution of the slurry similar tomato paste the sensor technology needs to ensure reliable media detection with short reaction time.

Engineers from UWT GmbH organized together with local partner SIERRA Servicios Industriales SAC. some tests to configure the suitable device. They decided for the latest capacitance sensor series of Capanivo® CN 7000 which is specially designed for applications in different liquid measurement. With the pasty and adhering medium, the capacitive probe proved to be the optimal solution for the user due to the exact surface detection and integrated tip sensitivity technology. The devices are equipped with potted electronics and work with the innovative Inverse Frequency Shift” technology. They have a robust, certified design and through the variation of versions with cable, rope as well as rod and tube extensions, the sensors can be easily adjusted to the respective vessel conditions. The food company needed to measure tomato paste at a temperature of 100ºC (212°F). After the material became paste and has lost almost all of the liquid it reaches a very low dielectric value (1.6 – 2.0), however very sticky. Another concern is the chemical resistance to the high temperature of the CIP (Clean-in-place) process with about 90ºC (194°F), together with the Food Grade compatibility. The solution should be highly reliable with a compact probe design because of space-limited tank dimensions and a measuring range of 1.5 meters (4.92 feet).

The Capanivo® CN 7000 level limit sensor has been installed quickly into the process hopper of the tomato manufacturing operation side. When touched by a medium, the sensor reacts to the change in capacitance on the probe arm, whereby a signal output is then switched. The universally applicable two-wire switch is particularly suitable for limited space conditions due to its unique compact design. Besides the version with connection cable, a housing version and a complete plastic version are also available. With its reliable media detection and short reaction time, it helps to ensure the smooth process flow and lasting quality of the end product. The CN 7000 guarantees a safe flow of media despite vibrations and the fact that some of the liquids are viscous and adherent, which is compensated by the integrated tip sensitivity.

Functionality, easy handling and long product life in accordance with the high requirements and standards of the food industry have to be considered for smooth plant operation. International certified technologies combined with extensive industry knowledge allow UWT to provide tailor-made measuring technology and compatible solutions for filling level and limit level detection, successfully implementable in process containers of nutrition plants worldwide.

Experts in Level Measurement

Based in the Allgäu for more than the past 40 years, UWT is the leading manufacturer of level measurement technology on the world market. The company is principally focused on the field of bulk solids and liquids. Its head office, development and production facilities are located in the Allgäu. With an additional production facility in Malta and its own sales subsidiaries in the United States, United Kingdom, Russia and in the growth regions of China, India and Brazil, the company can meet the needs of the world market with the greatest flexibility that customers expect. The company is certified ISO 9001:2015 and constantly expands its portfolio of product certifications (ATEX, FM, CSA), particularly with regard to the international markets. The products feature easy handling, high reliability and long service life under the motto of the company “Brilliantly simple level measurement in bulk solids.”

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Level measurement technology at the highest level LEVEL. UP TO THE MAX. UWT GmbH in Betzigau is the expert in level measurement technology and a reliable, world leading solution provider for the safe and accurate...

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