Process measurement devices:
Precision right down to the smallest detail
Flow rate - a classic process parameter
Even today, tasting is still among the monitoring methods used in the manufacture of foodstuffs - and that not only in small businesses. But it goes without saying that laboratory apparatus is also used to assist the process of finally approving beverages for bottling or packaging. Producers are well advised to ensure that every step in production, right down to this last one, is continuously monitored - from the raw material all the way to the bottled or packaged product ready for dispatch to the shops. Subjects such as quality, optimum use of resources and effective production processes, not to mention error avoidance and the like, are constant issues in a modern production facility today - and that is true not only of the beverage industry.
If samples are taken for analysis in the laboratory, it is only ever possible to obtain a momentary snapshot of the process concerned, and always with a time lag; process measurement devices, on the other hand, offer a continuous flow of information in “real time”. It is thus possible to react immediately to changing circumstances.
Among the classic process management parameters in beverage manufacturing are the measurement of pressure and temperature. Over the last 40 years, a further important parameter, flow metering, has become indispensable.
The following procedures are used for metering the flow of liquids, each of them having its own advantages and disadvantages:
- Mechanical meters (the rotary piston, oval disc and turbine principles)
- Differential pressure meters (the orifice principle)
- Ultrasound meters (in-line or clamp-on systems)
- Vortex meters (“Von Karman’s vortex street”)
- Electromagnetic meters (Faraday principle)
- Mass flow meters (Coriolis principle)
By their nature very nature, all these procedures involve pure process measurement devices installed directly in or on the product pipe. The great variety of possibilities offered by metering technology has led to a rapid increase in the number of measuring points at a whole variety of different process stages in plants.
In the beverage industry, a particular position among the different types of flow metering technology is occupied by the electromagnetic flow meter (EFM). The measuring principle is outstandingly suitable for use in this industry, and is characterised particularly by the following technical advantages:
- freedom from maintenance and wear, since no internals and no moving parts are required
- a completely hygienic design, unrestrictedly suitable for CIP and SIP
- a simple smooth tube that causes hardly any additional pressure loss
- a high degree of metering dynamism and accuracy
- a high level of reliability
- an outstanding cost-benefit ratio
GEA Diessel has been producing these EFM meters for more than 20 years, and has continuously pursued the further development of its IZM series devices to meet the particular requirements of the foodstuffs industry.
Simple flow metering with an integrated control function
One of the performance parameters in the process of manufacturing beverages is the “throughput” of the product, as measured (for instance) in litres, hectolitres or cubic metres per hour. For EFM devices, such a metering task is of course a piece of cake. Among the typical applications are the monitoring of filtration processes or CIP circuits, and of course also use in continuous blending equipment.
Thanks to the various diameters and the broad range of amplification available, flows of between 1l/h and 2,000 m³/h can be measured. Sophisticated functions such as empty pipe detection to prevent inaccurate metering when the measurement pipe is not full or the automatic switchover between measurement ranges afford the user simple and reliable metering.
It is often the case that within a single process stage (e.g. short-time heating) the flow velocity must be kept constant. As an option, the 4-20 mA output port of the device can control the regulating valve directly or actuate a frequency converter - a practical and also economical solution.
In the production of seasonal “fashion drinks”, modern beverage facilities must be able to react flexibly to market requirements. A second meter and a regulating valve allow simple proportional regulation to be realised. If all the devices and equipment are mounted on a mobile frame, the blending point can be set up wherever it is required within the facility.
Official volumetric metering
The electromagnetic metering principle is fundamentally a measurement of flow. By using integration to total the individual flow values over time, measurements of volume can also be obtained. By contrast, the mechanical rotary piston meter (for example) is a primary volumetric metering device (“litres per revolution”), the flow signal having to be generated afterwards. In the early days of this type of technology, such conversions were quite difficult. But thanks to the introduction of high-performance electronics and in particular of the microprocessor, modern devices can carry out such conversions without any loss of accuracy.
In the beverage industry, official volumetric metering is required in various areas; in the spirituous liquors field, for example, Customs and Excise require volumes to be officially registered, as does the Inland Revenue in the brewing area. For accounting purposes, e.g. when milk is collected by tankers or beer is discharged from beer tankers to the storage tanks of pubs, there is a legal requirement for the entire metering unit to be approved by the weights and measures authorities.
Metering devices with a high level of accuracy have been a trademark of GEA Diessel for more than 40 years. Right from the initial design phase of each individual unit and as far as the installation of the complete plant, care is taken to comply with the regulations of the German national metrology institute the Physikalisch-Technische Bundesanstalt (PTB) in Brunswick. The company’s many years of experience in this sensitive field of application are documented by its possession of official approval certificates for the widest variety of liquids and processes.
As an expert in these important special applications, GEA Diessel not only manufactures the metering devices itself, but also produces a multiplicity of additional equipment such as displays, gas separators or official printers at its own factory.
Volumetric metering with integrated preselection of quantities and filling function
The integration of quantity preselection allows a variety of process steps within beverage production to be partially or even fully automated using only a single device. The addition of an easy-to-read operator terminal and an illuminated multi-line display allow (for example) internal circulating procedures to be realised simply. The metering device itself switches the pump on and off via a relay output, so that no valuable manpower is tied up in monitoring the entire process.
Mobile metering unit with integrated quantity preselection
In addition to all this, the precise filling of cups, bottles, bags etc. requires very sophisticated technology. Although precise flow and volumetric metering is an important basis for this, it is not in itself enough to ensure optimum filling. Especially when filling times are short, the speed of the signal processing and precise quantity delimitation are particularly important. Valves that close consistently and rapidly, a defined dripping behaviour etc. also play a not insubstantial role in reinforcing the benefits of precise metering and switch-off technology. These functions are fulfilled by GEA Diessel’s IZM filling meter.
Internal monitoring functions and the use of modern mathematical methods to determine the afterrun correction keep operations reliable, even if there should be slight changes in the hydraulic conditions.
Continuous or batchwise dosing
When only small quantities of other ingredients are to be mixed into the main product, this is called “dosing”. In the beverage industry, colourings and flavourings are typical products that require dosing. GEA Diessel with its many years of experience is the specialist in the field of in-line mixing techniques. Complex in-line blending equipment from GEA Diessel which in some cases is able to handle more than ten components is to be found in operation in the most modern beverage production facilities throughout the world. The high degree of precision of the individual metering devices provides the basis for achieving the required accuracy of dosing. Compact dosing units make it possible to achieve total flexibility in selecting the beverage, practically directly before the filler. In the case of “stop & go” procedures, it is absolutely essential that the metering and actuating equipment should be capable of rapid reaction. Intelligent calculation and regulating processes can enable even extreme formula tolerances to be complied with.
Lemon, lime or cherry flavourings in yellow, green or red - these are the flexible responses to quickly changing consumer behaviour. An IZM device can also of course be used to realise classic dosing in the batch procedure, in which the quantity to be added is set at the device itself and the dosing process started by an electrical starting signal. When the desired recipe quantity has been reached, the IZM stops the dosing precisely to the millilitre.
Summary
The metering, control and regulation of flows and volumes are among GEA Diessel’s core competences. State-of-the art-technology coupled with many years of experience in the field of quantity determination are offered by electromagnetic flow meters, whose variety and flexibility makes them suitable to perform a wide variety of applications within the beverage industry. On the basis of this metering technology GEA Diessel supplies complete units, pre-assembled and tested, so that installation and commissioning make only minimum demands on the operator. For the customer, this means being able to plan time and costs reliably. Typical units from the production programme are
The author:
Hermann Hartmann. Dipl.Phys., responsible for measurement and data technology at GEA Diessel
Published in: drink! Technology & Marketing 6/2006
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