Extrusion Screw Cooling System

We bought two screws for our CV line last year; one of them for XLPE (6”-L/D:24/1-CR:2.50 square pitch single flight Maddock mixer) and the other screw (6”-L/D:24/1-CR:1.2 barrier). Both screws have a core for cooling system. We need a recommended cooling unit for these types of screws (a cooling unit that can be used for both of them).
Please make us a recommendation for: brand of the unit, capacity (GPM), type (water/oil) etc.

Thanks in advance for your cooperation and best regards

Hello again bighead,

Both oil and water are OK but personally I prefer water because it is far less messy.

If you can obtain a constant input temperature of water, you can build your own system by using a proportional valve on the input and temperature sensing on the output water.

Another way is to contact your extruder and heat control panel manufacturer and see if you can buy an add-on control system for the screw. Hopefully there is an empty position for the controller in your existing heating control panel.

There are many other equipment manufacturers supporting the plastics industry with two of the more popular being Sterlco www.sterlco.com/ and Mokon www.mokon.com/ but you will have to contact them and evaluate them for yourself. I have used them both but not for screw cooling.

All equipment manufacturers will provide you with the details of their equipment including recommended flow rates and so on for both your screws. Armed with all this information, you can make your decision as to what you want to do.

See your screw manufacturer for the cooling assembly connected to your screws if you do not already have this. Ask them questions about the length of the cooling supply tube inside the screw in reference to the highest shearing point along the screw because both screws are quite different. See what they recommend for each screw.

Regards,
Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com

Here is another source: www.completeplastics.com/Central_Chiller_Systems-2283.html

Thank you very much again for the information.
By the way I would like to ask you something else:
When you use cooling in the screw, how far the temperature of the cooling fluid must be from the melt temperature of the material that is being processed?

Hello again,

It has been a very long time since I set these type of processes up and thus my memory might be faulty. I think however that this could be one way of doing it:

A constant input water temperature set somewhere between 70 and 80 degrees C and a constant output temperature set say between 90 and 100 degrees C.

Talk with your extruder and screw manufacturer and with your polymer manufacturer for their recommendations.

Regards,
Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com

Thanks again for the information