In industrial food production, temperature is one of the most frequently measured process parameters. It plays a central role in many processes and has a major influence on the quality of the final product. Thus, measuring instruments providing the decisive measured value become the focal point for the quality analysis of production processes. Currently, three central requirements are placed on the measuring instruments: high measuring accuracy, optimum hygienic design and cost effectiveness in quality management. To meet the sum of these demands, WIKA has developed a special product programme for temperature measurement in the food industry.
For temperature measuring instruments, the hygienic design requirements can be implemented by means of thermowells that prevent any contact between the sensor and the food product. By means of a replaceable measuring insert, the instruments can be calibrated without opening the process. This is especially advantageous for aseptic production and enables the plant manager to carry out a calibration according to the HACCP concept without having to clean and sterilise the plant afterwards.
In order to guarantee that the accuracy of the measurements remains constant, instruments must be calibrated at regular intervals. How often an instrument is calibrated depends on the extent to which the measurement affects the quality and safety of the production process. Calibration intervals can be up to two years, but for critical processes they can be considerably shorter. In severe cases the measuring instrument is checked after each batch.
Therefore, the electrical thermometers developed by WIKA are all designed in such a way that they can be easily calibrated on site. The thermowell stays in the process and keeps the process closed. The connection head is pulled out of the thermowell together with the measuring insert and calibrated directly on site at the measuring point by means of an appropriately designed WIKA dry well calibrator. This makes it possible to calibrate the resistance thermometer together with the whole measuring chain, ie, without having to disconnect the electrical connections. A precondition for this is a suitable control system, which enables an on-site calibration. If such a control system is available, the measuring instruments can be calibrated quickly and without much effort directly in the plant. This maximises the availability of the plant and at the same time minimises the costs and the deployment of personnel.
For the integration of the temperature sensors into pipelines, a special thermowell is available that meets all requirements applicable for sanitary applications. The integration is carried out by means of orbital welding and can thus be effected quickly and cost-effectively with a defined and clean weld seam. No extra sealing is necessary for the integration of the measuring instrument into the pipeline. Looking at the costs for high-value sealings, and the time and effort for replacing them regularly, the plant manager saves annually per measuring point.
By means of the thermowell, the sensor can be installed in the middle of the pipe or of the medium which is flowing. Looking at the flow in a pipe and thus at the temperature distribution in the product, even in case of turbulent flow, it can be observed that the temperature is considerably higher in the core of the flow than at the pipe walls.
Depending on the flow conditions and the temperature difference between to ambient, temperature deviations can reach more than 5°C. Therefore, the registration of the temperature in the core of the flow is extremely important for an accurate measurement. Only a precise registration of the process data allows optimum use of heat to minimise the energy consumption.
In addition to components that are in contact with the products, plant components that are not in contact with the food are also cleaned at regular intervals. This requires thermometers that allow easy cleaning of the housing components as well. Therefore, a good hygienic design of the housing is required in addition to a high IP protection. With the new thermometers developed by WIKA, cleaning agents run off the housings equally well in all mounting positions. This prevents cleaning agents or water from accumulating on housing parts, thus avoiding the formation of a breeding ground for bacteria and microbes. The combination of these measuring instruments and other plant and machine components with optimum hygienic design provides the plant manager with the benefits of optimal cleaning of his plant parts and, above all, effective protection against harmful contamination of the product.
With regard to the food compliant design of a temperature measuring point, attention should be paid to the timely integration of a suitable supplier of temperature measuring instruments during the planning phase of a machine or plant. Only then will it be possible to plan the measuring points to state-of-the-art and to using optimum measurement technology and hygienic design for cost-effective and safe operation.
For more information contact WIKA Instruments, +27 (0)11 621 0000, [email protected], www.wika.co.za
| Tel: | +27 11 621 0000 |
| Email: | [email protected] |
| www: | www.wika.co.za |
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