Old 12-29-2009, 12:25 PM
Join Date: Jun 2008
Location: Melbourne Australia
Posts: 399
Default Re: High duty fire bricks

If they "claimed" no asbestos , your widow will be able to sue them.lol
Reply With Quote
Old 12-29-2009, 06:42 PM
altamont's Avatar
Join Date: Mar 2009
Location: Altamont, NY
Posts: 43
Default Re: High duty fire bricks

Hate to admit it, but I spent almost 15 years with AP Green. As the USA stopped manufacturing this and making that, demand dropped. And fast. The remainders of APG and Harbison-Walker and Kaiser basically ended up consolidating into one. And that one is much smaller now than any one of the originals were. And I personally have concerns about the health aspects too - I crawled in and out of thousands of furnaces over those years.

Back to the original train of thoughts in this thread though:

For our WFO's we all will see just a little difference in the heat retention (and rate of heat-up) between low heat duty, medium heat duty and super duty bricks.

If the information is available, compare the density (weight per unit volume). For our purposes we can assume a greater density will store more heat. On the other hand that means a little more fuel being burned to supply those calories. Then, to get even more rententive, we could start considering the thermal conductivity - a VERY rough generality is the denser material will conduct heat a little bit faster which could imply a slightly higher heat loss.
Concentrate on following the great plans provided here, and INSULATE - bottom, sides and top - any place a firebrick is located: insulate. If in doubt and can afford it, add more insulation.

Last edited by altamont; 12-29-2009 at 06:45 PM.
Reply With Quote
Old 03-25-2010, 09:52 AM
gsp gsp is offline
Join Date: Mar 2010
Location: Washington
Posts: 1
Default Re: High duty fire bricks

Looking for a good source for high duty firebrick in WA. Any leads would help me get my oven built!
Reply With Quote
Old 04-02-2010, 10:43 AM
Join Date: Apr 2010
Location: UK
Posts: 3
Default Re: High duty fire bricks

High Duty, when the alumina content is high it makes the bricks more resistant to very high temperatures and erosion/hot corrosion. The reason is that the other constituent in them is silica. On the net you can find the alumino-silicate phase diagram, essentially at the high alumina end the brick's melting point is extremely high 1828C, whereas once the silica content is above 30% this drop down to a mere 1587C (and stays there unless fluxed lower by other contaminating oxides, e.g. calcia).

So that is the duty side of things clarified, a non-starter for cooking ovens, but what about when in direct contact with the fire, what is the max. temp?

Heat retention is a completely different matter, here we are talking about thermal mass and thermal conductivity. If you want the brick to store a lot of heat you want it to have a high thermal mass (and not lose it by conducting it away to cooler regions), in simple physics terms you want it to have a high specific heat capacity, i.e. the heat/energy required to raise a unit mass, Kg by 1 degree, now here is where densification comes in. If the product is quite dense it will have a higher thermal mass per unit volume than a less dense version. Now replacing alumina by silica or vice versa will [B]not[B] necessarily improve or reduce the thermal mass, it depends on their relative specific heat capacities (& how dense the brick is made when you consider this on a volumetric rather than a weight basis, as noted above). My guess is that their specific heat capacities are probably quite similar, so probably a non-issue?

From tables, an engineering brick has a specific heat capacity of about 1.0 kJ/KgK, whereas a firebrick has a specific heat capacity of about 1.05 kJ/KgK.

So unless you plan to melt steel the high duty firebrick could be a bit of an overkill, or is it?

I have updated another post on this type of topic with info on typical thermal conductivities of firebricks, engineering bricks and a couple of red /buff common bricks (not concrete common bricks). Not an issue if you choose the right brick.

I hope this is helpful and helps clears up the various issues involved (but I don't know the max duty temps.)
Reply With Quote

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Oven (Floor - Wall - Dome) Fire Bricks Thickness?! southpaw Pompeii Oven Construction 11 03-12-2011 10:54 AM
Firebrick - Low duty, High duty thecac Pompeii Oven Construction 9 02-12-2009 10:22 PM
New Fire Bricks with Cracks staestc Getting Started 8 11-03-2008 04:37 AM
Has anyone used high duty fire bricks? gecko Getting Started 11 07-27-2008 01:07 AM
fire bricks boccu Getting Started 8 12-10-2006 11:38 AM

All times are GMT -7. The time now is 05:54 AM.

Powered by vBulletin® Copyright ©2000 - 2015, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO 3.6.0
2006/10 Forno Bravo, LLC