Strip force variability on a XLPE extrusion proces

Hello everyone

Hope everyone is fine, I´m using this forum to share with you a big issue we are facing with strip force variation.

Here is a brief description of the process:

a) XLPE process, steam cure
b) Currently using oil over strand to control strip force
c) Water content %: as an average 35%

Issues we are facing:

a) High variability of strip force after some hours of the extrusion, when product comes out we are getting measurements on the range of 20-30Newtons, after several hours it goes up to 80-85Newtons
b) Sometimes strip force remain low with minor changes causing overmilking during jacket extrusion.

A couple of questions:

a) There is by procedure an aging period of 5-7 days in order to stabilize strip force but I´m wondering if aging period can potentially cause overmilking condition?
b) Is someone else using such aging period for strip force stabilization? Would lack of aging cause an overmilking condition at jacket extrusion?

We did some brainstorming analysis and thinking, viscosity of oil, aging, line speed, oil type/conditions, water content, extrusion tooling would be potential causes.

Friends any thoughts or ideas?
Am I providing enough info for you to support?

Thanks in advance for your help

Ed Reynoso
Regards

Hello Ed,

1) I have never heard of spraying oil on a solid or stranded conductor prior to CCV extrusion. Which types of conductors are you using? - Sizes, constructions and metals.

2) Please confirm that this is all single layer insulation rated below 5,000 Volts.

3) How uniform is the outer layer of your strand? Any gaps in this outer layer that could result in "fall ins"

4) What do you precisely mean by milking and overmilking? This is very strange language for us. Has this something to do with the movement of the oil inside and along the cable? What is this oil? Silicone? What about environmental stress cracking?

5) Was this oil recommended by an XLPE manufacturer such as Dow or Borealis? Have you discussed your technical issue with the XLPE compound manufacturer?

6) You talk about "jacket extrusion", To me this seems to be a final thermoplastic, pressure extrusion process over the XLPE insulated cable. Is that correct?

Thank you.

Regards
Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com
519 641- 3212