Knowing the exact inventory of stored materials is crucial to remain competitive in today’s food and beverage markets. Too much safety stock drives inventory costs up, whereas too little can lead to production delays. Level measurements provide precise information about the existing quantities of things like syrup, grain and flour in order to reduce costs through optimised storage.
Regardless of whether it is silos or hoppers containing solids or tanks full of liquid, a suitable measuring technology solution quickly provides clear information about the amount of product currently available. To provide this information, the level must be continuously monitored, something that cannot be done with simple limit switches. That is why radar technology has become increasingly important over the past years. Two technologies have prevailed in this area: guided measurement according to the time domain reflectometry principle (TDR) and the frequency modulated continuous wave (FMCW).
With TDR, a discontinuous electromagnetic impulse is transmitted down a guide at the speed of light, reflected off the product surface and received by the signal converter again. As the speed of light is constant, TDR measuring devices do not require calibration. In addition, there are no moving parts, making the devices maintenance-free. With TDR technology, product changes do not affect measurement accuracy.
Using the FMCW principle, a radar signal is emitted via the antenna, reflected off of the product surface and received again following a delay. Unlike the ‘guided’ measurement of the TDR principle, FMCW measurement is non-contact. Depending on hygienic requirements this can be a deciding factor when selecting a suitable measuring device.
It is worth noting that the properties of the products being measured can present challenges, even for modern radar measuring equipment. Solids such as grain or flour produce a considerable amount of dust and liquids like beer, for example, can foam up. The formation of condensate and the presence of layers can also be problematic when it comes to the level measurement of liquid products.
Reliable inventory measurement
Krohne has been involved in the food industry for decades and offers a range of solutions to these problems. The Optiflex 1300 measures according to the TDR principle and is suitable for solids and liquids alike. It is also able to detect and measure separation layers in liquids. Even the formation of foam on the surface does not affect measurement. Another advantage, compared to earlier radar devices, is its higher signal dynamic. This means sharper impulses, which make it possible to measure thinner interfaces.
Outstanding silo management
An application at Carl Kühne, an internationally active company in the field of specialty foods and one of the most successful premium brands on the German food market, is used to demonstrate this in practice. In addition to the production of vinegar, deli foods and fine pickled goods, Kühne is one of Germany’s leading producers of mustard. The different types of mustard seed are mixed, ground and stored in different silos. The company was looking for a reliable silo management system for the 24 silos as well as reproducible tank monitoring in order to optimise storage costs. The company decided to install Optiflex devices to measure the level of the mustard seeds reliably.
To monitor barley and malt levels, König Brewery also decided on the Optiflex continuous level sensor. Its hops and malt supplies are stored in cement silos 22 m high with a capacity of 100 tons. The brewery was convinced that the level measuring devices provided several benefits in one compact unit. For example, the measured value is not affected by built-in components in the silo such as entrance aids and catwalks. With the guided radar from Krohne the brewery can plan its orders of raw materials better, helping to reduce costs. The end result is no uncertainty about availability and no need for partial refills, enabling optimum use of the available storage capacity.
Non-contact measurement for demanding applications
Once a user has decided on non-contact level measurement, Optiwave 7300 operates on the FMCW principle and was designed for liquid products. Its counterpart for solids is the Optiwave 6300, which features a drop antenna immune to deposits and provides continuous measurement of level and volume, even in dusty environments.
Optiwave 6300 provides continuous, non-contact measurement for the levels and volumes of solids such as flour, sugar, rice and malt, whether in powder or granulated form. This new, non-contact FMCW radar level measuring device features a special drop antenna made of plastic, making a washing system superfluous. Its dynamics guarantee superior measuring accuracy and no special equipment is needed to adjust the antenna. Installation is easy and measurements can be made even during filling for reliable level monitoring at all times. In addition to the drop antenna, a stainless steel horn is also available for use at higher temperatures.
Superior performance under difficult measuring conditions
Krohne developed the Optiwave 7300 to measure the distance, level and volume of liquids and pastes in tanks. It too is a noncontact FMCW radar level measuring device, which gives a more stable measurement than pulse radar and is well suited to agitated process conditions. The hygienic antenna is particularly suited to the food industry as all of the parts are made of special plastic for continuous monitoring in storage tanks for fruit juice concentrate. Precise level measurement guarantees exact data for optimum inventory taking.
Solution reliability
In light of the narrow margins in the food industry, optimal management of raw materials is vital and for these applications, Krohne offers an entire series of level measuring devices. One reason for the high quality of the level measurements, the basis for precise inventory data, is calibration. Krohne operates plants that boast high accuracy, reliability and efficiency for both radar and TDR measuring devices. The calibration process is to a large extent automated and is performed on calibration lines over 30 metres long in some cases. In addition, all devices, whether in the Optiflex or Optiwave series, feature superior application safety and an innovative operating philosophy.
For more information contact John Alexander, Krohne SA, +27 (0)11 314 1391, [email protected], www.krohne.com
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