Dear Mr. Peter,
Thanks for your reply. Well I don't know "eraser" and I asked my manager if he is "eraser" and he said no. Maybe he came from different company.
Well anyway, i just want to clarify something. We are using single extrusion only and not CV line when running OHL. Our screw is Extruder NMC 150-24D.So the answers that you gave me are also applicable to single extrusion? because on answer #2 you mentioned there CV tube, so maybe you think that we are using CV in using XLPE CB. Thanks for your reply.

Joseff

Hello again jprs_ie,

OK now I understand what is going on.

You just added on to an existing thread which by the way related to moisture curing. Moreover you didn't tell us what kind of extrusion equipment you have, the process you were using and the product you were manufacturing.

While this may all clear in your mind, the rest of us are blindly going on thinking that the thread is referring to "eraser's" problem.

This is the first time we have ever had this type of mix up. Talk about confusing the moderator!!!!! Please do not do such a thing again.

We will respond to your case below.

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

Hello again jprs_ie,

First of all stop using acronyms as typing short cuts. We may not understand what you mean. Here are some questions?

1) What do you mean by XLPE CB?
2) What do you mean by OHL?
3) Is this a moisture cure process as follows;

Process "a" - The purchase or manufacture of a very clean LDPE or LLPE which has been compounded (pre-grafted) with vinyl silane. This first step is done in a mixing extruder and includes accurate mixing with a peroxide initiator and an antioxidant before pelletizing. We will call this Compound "A".

Process "b" - The purchase or manufacture of a catalyst masterbatch produced by the accurate mixing a very clean LDPE or LLPE compounded with an organo tin catalyst such as di-butyl tin laureate and then pelletizing. We will call this Compound "B".

Process "c" - The accurate mixing of compound "A" with the catalyst masterbatch (Compound "B") and a color masterbatch by gravimetrics at a regular PE extrusion line.

Process "d" - The wire or cable insulation is cross linked in a steam room, in boiling water or just by leaving it in a normal plant environment for some period of time.

4) Do you purchase or make your own Compound "A"?
5) Do you purchase or make your own Compound "B"
6) What do you mean by an "auxiliary extruder"?


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

Hello jprs_ie

What do you mean by "Our screw is Extruder NMC 150-24D." as stated above? Does that mean you have a Maillefer NMC 150 mm extruder with a 24:1 length to diameter ratio and a standard Maillefer XLPE barrier screw? Please, please take the time to compose your questions and descriptions carefully. We cannot see what you see!

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

Dear Mr. Peter,
First of all I would like to ask for an apology for confusing you and the readers. I am sorry for not being that detailed. I will try to be detailed as possible next time.
Below are my answers:
1. XLPE CB - the CB means carbon black
2. OHL - Overhead Lines
3. Since it is a overhead line cable, in our company we dont cure (steam) it because as per our technical it will be cure sometime.
4. Now, we are producing our own PE.
5. We are also producing our own catalyst but during the time we are experiencing this problem we are using other company's catalyst.
6. Auxiliary extruder means it is the small extruder connected to the main extruder.
7. Yes Mr. Peter, we are using maillefer extruder.
Thanks and Sorry again.

Hello jprs_ie,

OK now that the WAI website has been restored following the damage inflicted by hurricane Irene, and now that we know something about your situation, your questions were:
1. Why is it that when we are using XLPE CB (Carbon Black), it burns easily when the machine stops for a minimum of 20 seconds.
2. Can we use the auxiliary extruder for overhead lines? (The machine must have an auxiliary extruder because it is much smaller. The present extruder is a 150 mm 24:1 L:D)
3. Can we use tube tooling rather than pressure tooling? It tube tooling we can bleed while setting up the pay-off drum but in pressure we don't bleed because the plastic might get inside the tooling.
Here are my thoughts re your questions as follows:
1) We are unsure of how you are getting the carbon black to mix with your Compound "A" (Pellets? Powder?) but we assume that you are using a gravimetric mixer at the extruder hopper to add a color concentrate and the catalyst masterbatch, compound "B". The first thing to do is to make sure the correct proportions are being mixed.

(i) Recalibrate your mixer by direct measurement.
(ii) Make sure the laboratory recipe is correct and that there is not too much catalyst masterbatch (Compound "B") being used or too much peroxide initiator in Compound "A".
(iii) Make sure that your color masterbatch and Compound "A" has been dried to a -40 dew point just before entering the gravimetric mixer mounted over the extruder hopper.
(iv) Always slowly bleed the extruder when there is plastic in it.
(v) As I recall, Compound "A" generally has a shelf life of about one month. That would mean you have to stop manufacturing very large batches of this compound. Make sure the stored compound plastic bag is well heat sealed away from the atmosphere, out of the sunlight and in a cool, dry place.
(vi) Practice good logistics to manage your perishable inventory.

(2) If the 150 mm extruder is far too large for the rest of the line, then you need a smaller extruder to properly mix the melt and extrude it on the wire. However if indeed the 150 mm extruder is the correct size, a smaller extruder may reduce the line speed and thus compromise productivity.

(3) Stay with pressure tooling to guarantee proper wall thickness. Leave the conductor in the tip and slowly bleed. If your tooling angles allow, move the tip forward so it looks more like a tubing set-up when you want to bleed. Be very careful you do not damage the tooling or crosshead. Best to first simulate it in AutoCAD
Regards,
Peter Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com