TEMPERATURE CONTROL | TECHNOLOGY
limiting. The company says that the Tempro Basic C120, specially developed for large-scale consum- ers, is equipped with radial impeller pumps, which provide high volumetric flow rates for various pressure ranges. This temperature controller offers a high degree of operating comfort and an extensive range of equipment options for every specific application. It is available with different heating and pump capacities — the large version offers up to 46 kW heating capacity and 3.5 kW pump output, as well as a maximum flow capacity of up to 280 l/min. Directly cooled Wittmann TCUs can operate with
temperatures of up to 120°C and are used wher- ever high cooling capacities are required. In order to achieve high cooling capacities, the cooling water is not supplied indirectly via a cooling coil, as is normal practice, but the water inlet is connected directly to the heat exchanger instead. Consequent- ly, the appliance’s maximum operating temperature is indirectly dependent on the water inlet pressure. Previously, the minimum inlet pressure – 2 bar for
the steam pressure curve illustrated in Figure 1 – and the maximum permissible temperature of 120°C were linked to each other in TCUs with direct cooling laid out for 120°C. The consequence was that such appliances could not be operated with low water inlet pressures. In such cases, the pressure setting had to be adjusted manually to the actual operating conditions via the appliance’s display. According to Wittmann, with the new software installed in Tempro Basic C120 controllers, the system pressure (water inlet pressure) is measured continuously, the set temperature value is calcu- lated on the basis of the actual inlet pressure, and a corresponding temperature set-point limit is subsequently set automatically. This set value can then no longer be exceeded. If an operator tries to move the calculated maximum temperature set-point upwards, the LED set value display will flash and issue a warning signal. This indicates that raising the temperature set-point is not possible
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for safety reasons, since the water inlet pressure is too low. A minimum pressure of 1 bar has been fixed as the lower limit to prevent cavitation in the pump housing. Wittmann has also developed the Tempro Plus D temperature controller with SpeedDrive option. The company says that energy input must be analysed at every conceivable point in order to achieve optimal power consumption. Mould tempering in injection moulding can play a vital role. This led to the development of temperature controllers, which are now able to use the waste heat of a cogeneration unit for mould heating, and which can reduce the power consumption to the minimum required for the process by using a pump with variable rotational speed. The utilisation of waste heat became possible
through the Eco-Heating option brought to market in 2014, with which the Tempro Plus D90 controller was equipped. With this option, the built-in electric heating element is activated only when the waste heat of the cogeneration unit is not sufficient to maintain the process. The new SpeedDrive option makes it possible to set one of four process parameters (rotational speed, pump pressure, differential temperature or flow) as an additional control variable to achieve energy-optimised operation without jeopardising the process. The company adds that an inspection of
the entire temperature control circuit reveals several different areas where energy can be saved. Better insulation of the moulds and tubes can reduce power consumption, particularly with higher processing tempera- tures (>100°C). Energy savings in the pump can be achieved by using more efficient
Left: Precise temperature control using Easytherm from Aquatech, which is part of Piovan
Below: Wittmann’s Tempro Plus D160 tempera- ture controller, now with SpeedDrive
Above: The Tempro Basic C120 directly cooled single-circuit temperature controller from Wittmann is also available with an optional touch screen; large version of the appliance on the right
June 2018 | INJECTION WORLD 49
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