A castable Barrel Oven with Refractory or Homebrew mix

[stonecutter]

Re: A castable Barrel Oven with Refractory or Homebrew mix

In the case of the polypropylene fibres, as they are not added for strength this point is immaterial. In fact they melt at 160 C anyway. The stainless fibres do the strengthening instead and should be added to the mix at 2% min. by weight.

You're off on this one.

What it is saying makes sense....the fiber adds strength to the castable during the early drying stage, when there is more water present in the material, and not all poly fiber has the same melting point. Agreed, the SS fiber provides the lasting mechanical strength, but the early firing reinforcement of the poly can't be dismissed as immaterial.

[david s]

Re: A castable Barrel Oven with Refractory or Homebrew mix

Each manufacturer designs a number of castables for a range of different applications. There are a number of different fibres used. The product I use contains polypropylene fibres, which melt at 160 C (i know because I've tested them) some others use polyameric fibres and natural fibres. In the case of the polypropylene they are purely designed to reduce explosive spalling.


"Polymeric fibers are an efficient way to enhance castable resistance to spalling upon drying, because they allow more severe heating schedules under a controlled risk. Two mechanisms are responsible for the benefits conferred by these fibers: an increase in permeability caused by fiber melting, thermal degradation or shrinkage,1 as in the case of polypropylene (PP) fibers; and mechanical reinforcement, which results especially from the increased energy dissipated during crack propagation,2 as when polyaramid (PAr) fibers are used."


http://americanceramicsociety.org/bu...iles/Peret.pdf

[stonecutter]

Re: A castable Barrel Oven with Refractory or Homebrew mix

Each manufacturer designs a number of castables for a range of different applications. There are a number of different fibres used. The product I use contains polypropylene fibres, which melt at 160 C (i know because I've tested them) some others use polyameric fibres and natural fibres. In the case of the polypropylene they are purely designed to reduce explosive spalling.


"Polymeric fibers are an efficient way to enhance castable resistance to spalling upon drying, because they allow more severe heating schedules under a controlled risk. Two mechanisms are responsible for the benefits conferred by these fibers: an increase in permeability caused by fiber melting, thermal degradation or shrinkage,1 as in the case of polypropylene (PP) fibers; and mechanical reinforcement, which results especially from the increased energy dissipated during crack propagation,2 as when polyaramid (PAr) fibers are used."


http://americanceramicsociety.org/bu...iles/Peret.pdf

That was one paper I read last night, it had some good info.

160 C is within the temp range of the later quote I posted about early strength benefits of poly fiber, so I'm not sure if you are disagreeing or what.

Here's another interesting tidbit from this paper...http://americanceramicsociety.org/bu...iles/Peret.pdf

Drying Behavior
Explosive spalling occurred in all the steel-fiber-containing castables tested at 20?C/min
(Fig. 8). On the other hand, the material containing PAr fibers survived heating at that rate, attesting to the greater efficiency of these fibers in enhancing refractory resistance to drying and explosion. The thermogravimetric analysis revealed no significant differences among the mass loss rate profiles of the materials. Indeed, the structure of the permeable channels through which the water vapor flows was not greatly modified by the presence of the fibers studied. Neither melting of PAr and steel fibers nor degradation of PAr fiber occurred below the critical temperature range involved in the drying process. This is the key part : The greater resistance to damage on drying displayed by the PAr-fiber-containing material indicates that a more severe heating rate can be applied to the material, thereby lessening the overall time needed for the completion of heat-up.

To summarize, I think the last part sums up everything. The overall quality or performance of the casting is not impaired, but greatly enhanced by adding polyfiber and is beneficial to the whole drying process and speeds it up without the same risk of damage as castable without the fiber.( notice I didn't say cure )

This has been enlightening.

[Saovicente]

Re: A castable Barrel Oven with Refractory or Homebrew mix

Gentlemen,

Great discussion!!!
I thoroughly enjoyed the reads. Now to the point of which size fibers to purchase and any recommendations for a site to purchase it from.

Thanks,

Sandro

[Saovicente]

Re: A castable Barrel Oven with Refractory or Homebrew mix

Here you go, Greater Boston area, they carry Minute Man Lime....I used it many times when I lived in CT.

TLC Supply Cement

Stonecutter,

Thank you for the info. The place is closed today. I will reach out to them on Monday for a quote and find others around for a price comparison.

Any thoughts on the Whitacre Greer fireclay.


Thanks,

Sandro

[Saovicente]

Re: A castable Barrel Oven with Refractory or Homebrew mix

"here are a couple of reasons my oven does not have lots of smoke staining on the front, in spite of the extremely shallow entry (the flue gallery is only 4" deep) 1. and 2. a funnel like entry to the flue pipe."

David,

Great thoughts,

1) "(the flue gallery is only 4" deep)"
This where the left/right brain collide . If you can, walk me through this one.

I am trying to picture the "funnel line entry" so I borrowed an image of the web.
2) In a mold, are you molding it upwards from a smaller diameter to larger or vice versa.

2) "adequate flue pipe diameter"
My thoughts were on an 8" flue, but I want to square it off, to keep everything symmetric.
I will create a mold for the flue (using the homebrew mix)

PS: Do you have pizza parties and sell pizza or do you put that baby on a trailer and take it elsewhere.

[stonecutter]

Re: A castable Barrel Oven with Refractory or Homebrew mix

Any thoughts on the Whitacre Greer fireclay.

They make some of the best firebricks around, I see no reason why their Fireclay is any different.

[david s]

Re: A castable Barrel Oven with Refractory or Homebrew mix

The greater resistance to damage on drying displayed by the PAr-fiber-containing material indicates that a more severe heating rate can be applied to the material, thereby lessening the overall time needed for the completion of heat-up.[/B]

PAr refers to the polyamarid fibres not polypropylene (PP) , which melt at a lower temperature.

"Two mechanisms are responsible for the benefits conferred by these fibers: an increase in permeability caused by fiber melting, thermal degradation or shrinkage, as in the case of polypropylene (PP) fibers; and mechanical reinforcement, which results especially from the increased energy dissipated during crack propagation, as when polyaramid (PAr) fibers are used." paper suggests that the performance is improved if the PAr fibres are used instead of pp fibres."

Look we're splitting hairs (fibres) here. The bottom line is that the addition of fibres can improve strength and drying. Different fibres work in different ways.

Yes it is interesting, thanks for the discussion.

[david s]

Re: A castable Barrel Oven with Refractory or Homebrew mix

"here are a couple of reasons my oven does not have lots of smoke staining on the front, in spite of the extremely shallow entry (the flue gallery is only 4" deep) 1. and 2. a funnel like entry to the flue pipe."

David,

Great thoughts,

1) "(the flue gallery is only 4" deep)"
This where the left/right brain collide . If you can, walk me through this one.

I am trying to picture the "funnel line entry" so I borrowed an image of the web.
2) In a mold, are you molding it upwards from a smaller diameter to larger or vice versa.

2) "adequate flue pipe diameter"
My thoughts were on an 8" flue, but I want to square it off, to keep everything symmetric.
I will create a mold for the flue (using the homebrew mix)

PS: Do you have pizza parties and sell pizza or do you put that baby on a trailer and take it elsewhere.

Sandro,

pics attached explain what I meant. It is quite simple to make, once you've cast your oven, then you build a sand form (this mix should contain 10% water by volume and throw in a little powdered clay to help bind it) in front of the entry and trowel the mix over it.

My oven is only 21" but has a 5" flue diam. Obviously a larger oven needs a larger diam flue pipe, but this depends on the size oven you choose. From around 28" -36" you'd need a 6" flue and 42"+ an 8" (I'm talking round ovens here so work out similar chamber volume for other shapes)

I have a mobile oven on a trailer which I hire out for people to use and I also cater for the occasional party with it myself. I have the same sized oven installed permanently at home as well for our own private use.

[Saovicente]

Re: A castable Barrel Oven with Refractory or Homebrew mix

Once again David, I thank you.

You have been great from the start in sharing your wealth of information.

I will have a few more questions as I move forward in making the pizza oven as soon as the fire dept. gives the green light.

Once that happens, I will start a new thread detailing my journey as others like yourself have done before me .


Thank you,

Sandro

[Saovicente]

Re: A castable Barrel Oven with Refractory or Homebrew mix

Gentlemen,

I have found a supplier which will provide me with most of the items needed to get started (fireclay, & bricks (Whitacre), Lime,sand, peastone and more goodies. I have setup an account to get a contractor's price and I am on my way.

I am still looking for a supplier for the polypropylene fibres. The needles have been located on Ebay (found the info on this Forum )

I have added two *.pdf on the bricks for your thoughts One for red, the other for buff (both are low-duty). It is other area in which I have read conflicting opinions on (Low duty VS Medium Duty). I will be using the bricks for the hearth pad. I will be casting the dome.

Let me know what you think,

Best Regards,

Sandro

[stonecutter]

Re: A castable Barrel Oven with Refractory or Homebrew mix

You can get poly fiber here....

Fishstone - Fishstone - Concrete Countertop Supplies

[Saovicente]

Re: A castable Barrel Oven with Refractory or Homebrew mix

Thanks Stonecutter...You simplified a matter I had taken all over the place. You pointed me to AR Glass Fiber, which I had thought could not be the same product.

All this this, I had previously done research on AR without a thought of it having a separate naming (tunnel vision syndrome)

Well, I will save a few dollars since I have two bags of AR Fiber (3/4) in my shed. I use it in my back coats for GFRC mixes.

At times one tends to over think things....


Thanks again

PS: I have dealt with Fishstone and I can vouch for their great customer service and cost.

[Saovicente]

Re: A castable Barrel Oven with Refractory or Homebrew mix

Gentlemen,

I have read much of the success of the 3:1:1:1 and also the need for a dense, denser mix for the dome and I had a thought.

Your thoughts on adding 10% of VF-774 to the mix to tighten the bond between the Portland and sand, therefore creating a denser, cohesive mix.

With the add-ons of the AR fiber, needles and VF-774, it would make for one tight , harder baby. (unless there is an adverse affect from the lime and fireclay...hmmmmm (maybe not)

Thank you,

Sandro

[stonecutter]

Re: A castable Barrel Oven with Refractory or Homebrew mix

Gentlemen,

I have read much of the success of the 3:1:1:1 and also the need for a dense, denser mix for the dome and I had a thought.

Your thoughts on adding 10% of VF-774 to the mix to tighten the bond between the Portland and sand, therefore creating a denser, cohesive mix.

With the add-ons of the AR fiber, needles and VF-774, it would make for one tight , harder baby. (unless there is an adverse affect from the lime and fireclay...hmmmmm (maybe not)

Thank you,

Sandro

I didn't see any TDS for VF-774, but I'm going to have to assume that it will only benefit the curing process. I am pretty sure that the polymer does not have refractory qualities and it will burn out of the casting during the dry out schedule ( not the cure of the material)

I would save the Vf for concrete counters or other castings that are not subjected to heat above 200*