big size rubber hose 2

[sekassir3]

Hi everybody!

At our plant we are going to produce a kevlar reinforced EPDM hose 159 x 150 and 200 x 190 mm with continuous vulcanization (2 steps: 1 - precuring with microwaves, 2 - complete curing in hot air oven).
Extrusion and precuring - in vertical mode.
While producing the hose may be under air pressure up to 2-6 bars (there would be a seal at the end of the hose).
Line speed - up to 1 m/min.

What bother me now is the extrusion heads.
I can't find anybody, who would make such extrusion heads for us.
Tell me please, can somebody deliver to us such big heads?

Regards,
Serge Kassirov
Saint Petersburg
Russia

 

[GrahamBennett]

Such large diameter hoses are normally produced manually on a 30m or 40m long mandrel before being cured in an autoclave. I have never heard of them being extruded.

I suppose you could talk to the design engineers at Farrell Corp or the like to see if they can help.

 

[sekassir3]

Thanks, Graham,
you are right about big size hose and mandrel things.
But if 120 mm extrusion die exsits - see

http://www.colmec.it/uk/product-04_eng.html

-
why not 159?

Serge

 

[GrahamBennett]

The outside diameter of your hose is determined by the cover die diameter that will determine the thickness of the outer cover. The die head of this second extruder will have to be a T-head. This can be made quite easily but it will need support as it will be very heavy.

The extruder screw diameters are a different matter. These are sized according to the output required in weight terms. A 120mm diameter screw will push out approximately 250 - 650kg/hr depending on the viscosity of the compound, back pressure and screw speed.

Talk to an extruder manufacturer that has experience with hose making (e.g. Farrell Corp, NFM Iddon, etc).

 

[sekassir3]

Thanks, again, Graham.I have just posted to Farrel and NFM.
Anyway, want to be clear. Aside big weight problems, let's concentrate on the inner layer of a hose only (+ reinforcement, of course). What would you say about hose extrusion with hose OD 159 or 200 mm? Or 300 mm? (no cover for a while, only braid).
Where is the limit of such production mode resulting in looking for a mandrel? Is "very heavy" a dominating cause for mandrel using?

(I understand that there is such a thing as vulcanization, of course, in this case a hose may be under inner pressure, for example)

Hope I clear.
Regards, Serge

 

[GrahamBennett]

Serge,

I have only ever seen industrial-strength hoses over about 75mm ID as being hand built on a mandrel of up to 30 or 40m in length. Over about 125mm ID and the madrel will have a hollow core to reduce the weight of the mandrel. Over about 200mm ID and the length of the mandrel is reduced to no more than about 10m because of the weights involved.

None of these hoses are braided as such - they will be reinforced by using strips of rubberised textile applied on a bias angle (~54°). This angle is such that the hose will not change in length or diameter once pressurised in service.

Once a hose is fully built, several layers of wet, tightly-woven, linen strips are very tightly wrapped over the surface of the hose. The completed assembly is then transfered to a steam autoclave for curing. (The linen strips provide a compressive force to consolidate the layers in the hose.) When the hose has cured and removed from the autoclave it is allowed to cool down naturally before being blown off the mandrel using a compressed air gun.

 

[sekassir3]

Thanks, Graham!
Just have received a post from NFM Iddon - they have extrusion heads up to 180 mm bore! No mandrel, as they make curved hoses.
It seems OK for us!

Regards, Serge

 

[GrahamBennett]

Thanks for letting me know Serge. Good luck with your project.

Graham.