Temperature controller for extrusion of soft expanded plastic materials
In 2015 an Italian company producing

plastic sheet in soft expanded polyethylene and polypropylene

contacted us to inform about his needs and troubles.

The application was the control of temperature on the extruder barrel of a special machine dedicated to the production of sheets in soft expanded polyethylene and polypropylene, including the initial start of the system that was causing many problems.
The critical factor was the temperature at the process start, especially for polypropylene and switching from electrical heating (extruder’s heaters) to the external temperature controller to reach the production parameters.

Temperature controllers used in the past and at that time were not reliable and efficient and caused a lot of problems.

Thermal oil units had been abandoned long time before and were not to take into consideration for various reasons :

– risk of cracking of thermal oil
– difficulties in controlling temperatures properly
– insufficient oil flow rate of such units
– presence in the factory of butane gas used for the expansion of plastic materials, with related problems of safety.

The client advised :

– continuous failures of the mechanical seals of the water pump, thus needing to stop the extrusion line to replace the pump sealing every 10 – 15 days
steam returns when switching from heating through the extruder heaters to the temperature controller fluid
– water relief from the safety valve with the necessity of re-filling the circuit
– very unstable process features
– activation of the temperature controller heaters even when not necessary due to wide temperature fluctuations
– high cooling load on the central cooling circuit (higher than reasonable) with water returning up to 70°C
– long start times
production interruption
– excessive power consume (the existing temperature controller was equipped with 60 kW heaters).

Green Box analysed the existing situation and:

– introduced important modifications of the hydraulic circuit of the temperature control unit

– checked every single component in relation to the operating conditions and specified working parameters

– analysed all the possible risks

– selected the suitable components already tested on similar heavy applications

– developed a special unit including a PLC control (with internally developed software) to manage the peculiarities of the production cycle and unit features at the best.

Increase of operating features were immediately clear:

– no failure of mechanical sealing after 6 months of continuous operation

– process cycle start-up much easier

– no maintenance

– no production interruption

– faster process set-up due to the perfect temperature control during operating switching

– no risk of mistakes of workers during start-up (sets of operating parameters stored on the PLC)

– reduced power consumption and electrical power installed (18 kW heating power compared to the previous 60 kW).

The client has declared a dramatically improved start-up phase of the extrusion plant, with greatly reduced starting times and much less unforeseen problems.

Pump sealing failures have been completely eliminated.

Energy demand has been dramatically reduced thanks to the much better temperature control.

At the end our product has completely met the client’s needs and expectations.

Some optimisations have been carried out on the working plant to perfectly meet the operating needs with expanded polyethylene at lower temperatures.

The client has planned to use this solution on all his production lines and replace the units presently installed.

The extrusion plant manufacturer has declared his interest for this unit that should completely resolve the same starting problems on his systems delivered worldwide.

tg extrusion temperature controller

Reduced electrical power installed

60

Old temperature control unit

18

Green Box temperature control unit