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The Pasteurisation Process - Milk

Press DISPLAY button (DISP) to reveal set point (SP). This is the process temperature required (pasteurising temperature) and can be adjusted to the disired value using the ^ or V buttons

These buttons are used by simply pressing the "up" button continuously to increase and the "down" button to decrease. Whichever button is being pressed, the other button can be used to move along the figures in the display

Press ^ or V to obtain required pasteurising temperature such as 71.7ºC i.e. SP 72

To set up Diverter Valve

The diverter valve on the processing unit is used to divert the flow of product back to raw material storage if under processed i.e. processing temperature not up to the required set point value

This is achieved using an ALARM set point on the controller.

The alarm value is set by pressing SET UP button to reveal ALARMS on the display
Now press FUNCTION once to reveal AISIVA which is the alarm switch value
Adjust to required value using ^ or V buttons. The diverter valve setting is usually set value to 1ºC less than the pasteurising temperature setting i.e. in this example 71ºC
Press DISPLAY to return to display mode

Plate Heat Exchanger

The heat exchanger has been initially set up to enable the pasteurisation process to be carried out as a correct operation procedure. However there are an infinite number of ways that the plates and gaskets con be orientated in the laboratory for experimentation.
For example, the regeneration section can be omitted completely so that an experiment can be carried out to determine the saving in energy in using this facility. When rearranging the plates and gaskets in the various sections it is important to understand the basic concept of plate heat exchangers before experimentation is undertaken

Temperature Sensing

There are nine points at which special fittings are provided so that relevant temperatures can be recorded. As the chart recorder has only six plotting pens, it is important that the temperature sensors are located in the six positions required for the particular experiment
Sensor No.1 must always be fitted in the position between the holding tube and the diverter valve, as this sensor provides the input signal to the electronic controller in the console

Process Flow Rates

The flow rates of the chilled water used for cooling and hot water used for heating can be read directly from the flow meters. These are calibrated in cms³ per minute
The flow rate of the process fluid is determined by calibrating the peristaltic type of feed pump before operation so that the flow rate is known for any position of the variable speed drive control on the control console

Hot Water Circulating System

This system consists of the following components

Hot water tank
Heating element
Thermostat
High and low level switches
Top up solenoid valve
Circulating pump

The level switches in the tank are used for top-up and heating element protection. When the water supply is first connected, the tank will fill to the upper level switch when the solenoid valve will close. After this, every time the level falls far enough to activate the upper level switch, water will be admitted to replenish the supply. If for any reason the level falls to the level of the lower level switch, the heating element will switch off and will not be restored until the level switch is again covered by water
The thermostat has been set to switch off the heating element if the water temperature rises above 97ºC
The circulating pump is a magnetically coupled centrifugal type and as such will operate against a closed valve. When the heating circuit is in operation, the pump will run continuously so the flow requirement will be governed by the needle valve of the flow meter

Cooling Water Circulating System

The cooling side of the heat exchanger can be fed from a mains water cold water supply, however the cooling process is more efficient if cooling water is supplied via a chiller unit

Process Fluid Feed Pump

This is a peristaltic type pump which uses food grade silicone tubing to pump the process fluid. The pump is driven by a DC motor which is controlled from the control console by a variable speed drive. Before any experimental work can be carried out, this pump must be calibrated

Holding Tubes

The processing unit can be fitted with two differing types of holding tube, a 15 second holding tube and a 45 second holding tube. These holding times are based on a nominal throughput of 20 litres per hour. By varying the throughput, these holding times can be changed as required
The 15 second tube has a volume of 75.8 cu. cms
The 45 second tube has a volume of 240.0 cu. cms