Electricity + Control

Today nearly every liquid sold in stores is pasteurised to prevent the growth of bacteria and the potential for illness due to these unwanted microorganisms. Milk is one of the most susceptible liquids to this and only pasteurised milk is considered safe by the FDA. Pasteurisation of milk results in at least 95 - 99% of the bacteria and micro-organisms present (pathogenic germs) being destroyed.

Hot topic in beverage productionRaw milk is passed from the accumulation tank into the pre-settling tank. To maintain constant pressure on the suction side of the pump, the milk is kept above a minimum level in the pre-settling tank. By means of level switches and valves, the fill level is maintained as to prevent any air intake. The Liquipoint FTW33 uses a new sensor technology offering the advantages of reliability and automatic build-up compensation, even in the presence of foam or bubbles. No onsite calibration is required and the unit is installed without the need for any special tools.

If, during heat treatment, the product flow needs to be recycled (where heating is made inadequate or if contamination is present in the heat exchanger), the milk is often fed into the pre-settling tank, forcing the product to flow in a closed circuit until the error is rectified. From the pre-settling tank, the milk is passed into the pasteuriser. In heat exchanger 1, the raw milk is pre-heated to approximately 55°C. It is then fed to the separator and homogeniser, and then proceeds into heat exchanger 3, where it is heated to the pasteurisation temperature (>72°C). In the heat retaining section, the milk is kept hot at the corresponding temperature for the required time, forcing it to flow at a constant rate through a given pipe length. Heat treatment time is determined by flow velocity and the pipe length.

An electromagnetic flow meter is well suited to precisely measure the flow rate of the milk. The Promag H is a multivariable measurement for flow, measuring volume flow, temperature, conductivity, mass flow, corrected volume flow and corrected conductivity. The innovative Heartbeat Technology also allows online verifications to be done on demand as often as needed. The Pt100 temperature sensor (T1) and valve 1, control the heat exchanger temperature. The Pt 100 sensor (T2) at the outlet of the heat exchanging section also monitors the temperature in order to ensure that the required temperature prevails in the entire the heating section.

If the heat exchanger temperature falls below the required temperature, then safety valve 3 switches and directs the incorrectly treated milk into a circuit or back into the pre-settling tank. The temperature measurement and control is of extreme importance and has a direct impact on the taste and quality of the milk. A lower temperature can result in the risk of microbiological contamination and therefore a risk to the consumers’ health. Specially designed for use in hygienic applications within the Food & Beverage industry, the iTHERM QuickSens is the fastest temperature sensor in the world, with the quickest response times (t90s: 1,5 s).

Once the milk has been pasteurised, it is passed to the heat exchangers 1 and 2, where it is cooled down to 4°C.

An electronic differential pressure transmitter can be used to calculate the differential pressure. The Deltabar FMD72, eliminates the typical problems of conventional differential pressure systems. The problems most frequently associated with oil-filled capillaries are; unreliable measured values due to temperature changes, leaks or condensate. The FMD72 provides precise measurement and also facilitates reliable and safe process control.

The differential pressure, with the temperatures and flow rates, can be recorded on a data acquisition system. The advanced Memograph M is a flexible and powerful system for organising process values and allows perfect monitoring and registration of all the process parameters in a glance. The measured process values are clearly presented on the display and logged safely, monitored against limit values, and analysed.

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Title: Editor
Name: Wendy Izgorsek
Email: ec@crown.co.za
Phone: +27 11 622-4770
Fax: +27 11 615-6108

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Name: Helen Couvaras
Email: helencou@crown.co.za
Phone: +27 11 622-4770
Fax: +27 11 615-6108

Title: Advertising Manager
Name: Heidi Jandrell
Email: heidij@crown.co.za
Phone: +27 11 622-4770
Fax: +27 11 615-6108

 
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