Review WIP Fluidized Sand Pot

[Tenebr0s]

FBF’s heat steel faster and more uniformly than gas or electric furnaces. Used with inert
gas they are very efficient.

Hoss

This. Fluidized sand beds provide much faster heating than kilns. Quoting one source I have (Fluidized Bed Heat Treating, Marc Glasser), pdf available online:
"Tests conducted showed that the heat transfer coefficient for fluidized beds is approximately double that of forced air convection, and half that of salt... In practical terms, heat treating times for fluidized bed processes should fall exactly halfway between those specified for salt baths and air furnaces."

So, although not as fast as salts, still fast, and much safer. I definitely want one.

 

[kuraki]

The diffuser was the big sticking point for me in making one of these. I wonder if the expansion issue could be alleviated by bringing the air inlet in from the side and drilling into the fire brick so it terminated inside the brick rather than below it.

The other thought I had is remove it from the high heat chamber entirely and leave 4-6" of the tube that contains the diffuser outside the heat chamber. It will still get hot obviously, but maybe at that point you could hold 1850-2000 on the tube inside the chamber and only be 14-1500 on the diffuser portion.

 

[anvlts]

I and a couple of friends are working on a prototype fluidized bath that will be capable of operating at temperatures up to 2000F. We are going to build it out of Inconel, including a diffuser. All-mettal, TIG welded. Will build both gas and electric versions.

Here is video of testing the diffuser. After the initial testing, we made some changes to the design for more even gas diffusion.

https://www.facebook.com/video.php?v=161997997837421

Marko

 

[12345678910]

I and a couple of friends are working on a prototype fluidized bath that will be capable of operating at temperatures up to 2000F. We are going to build it out of Inconel, including a diffuser. All-mettal, TIG welded. Will build both gas and electric versions.

Here is video of testing the diffuser. After the initial testing, we made some changes to the design for more even gas diffusion.

https://www.facebook.com/video.php?v=161997997837421

Marko

No see um

Privacy settings or something ?

 

[anvlts]

Not sure why you can't see. Will post video separately.

 

[Gting]

Good info to have about this build bro.

I'd still like to hear more about why you're not using shielding gas?

Also, did you consider a propane HT furnace build instead? I've used many, and done correctly, they're excellent, very economical, and mitigates some of the concerns I mentioned above. Either way, I'm following this build, and I hope you'll do us the favor of outlining the disadvantages you discover, along with the advantages, once it's done. Trust me when I say, we'll all respect you more for your honesty, regardless of how successful it turns out.

For sure. Thus far the only do side I have found has been in my air control. I think someone linked a better flow meter that may alleviate that. Ill be looking to purchasing that one or one similar. That has been my only reason for not using an inert gas. I'm just about out of gas for my welder so I may go in and get my bottle filled with Nitrogen and use it for a couple runs in the sand pot. I will get back to everyone on that. I have 12 knives to do tomorrow, lets see if I can make it happen. Thanks for the support.

I hadn't considered a propane HT furnace. It would have been an option before this I'm sure.

 

[Gting]

I and a couple of friends are working on a prototype fluidized bath that will be capable of operating at temperatures up to 2000F. We are going to build it out of Inconel, including a diffuser. All-mettal, TIG welded. Will build both gas and electric versions.

Here is video of testing the diffuser. After the initial testing, we made some changes to the design for more even gas diffusion.

https://www.facebook.com/video.php?v=161997997837421

Marko

That pricey?

 

[Gting]

This. Fluidized sand beds provide much faster heating than kilns. Quoting one source I have (Fluidized Bed Heat Treating, Marc Glasser), pdf available online:
"Tests conducted showed that the heat transfer coefficient for fluidized beds is approximately double that of forced air convection, and half that of salt... In practical terms, heat treating times for fluidized bed processes should fall exactly halfway between those specified for salt baths and air furnaces."

So, although not as fast as salts, still fast, and much safer. I definitely want one.

Safe and fast. The speed in which steel heats up blew my mind the first time i used it. Even running a forge at 2300 cant compare to a sand pot.

 

[Tenebr0s]

Have you considered using propane as a percentage of your fluidizing gas? I know industrial ones will do this. I imagine, if done right, it would produce a reducing atmosphere. I don't know what the safety considerations would be, though.

 

[JTknives]

It can be done but caution has to be used becaus of the flammability of the gas and it can have a tendency case harden the steel. At least according to the book I have. But it is common to directly heat and fluidise the sand with gas in large industrial setups.

 

[anvlts]

That pricey?

If I get 10000 firings out the Inconel tube, is it really pricey? If one goes through the hassle of designing and TIG welding the fluidized bath, it might as well be done right. 310 stainless can be used for high temperature fluidized bath, but it won't last on par with Inconel or other nickel alloys.

 

[Tenebr0s]

It can be done but caution has to be used becaus of the flammability of the gas and it can have a tendency case harden the steel. At least according to the book I have. But it is common to directly heat and fluidise the sand with gas in large industrial setups.

Is there any risk of explosion if the diffuser gets clogged?

 

[Gting]

If I get 10000 firings out the Inconel tube, is it really pricey? If one goes through the hassle of designing and TIG welding the fluidized bath, it might as well be done right. 310 stainless can be used for high temperature fluidized bath, but it won't last on par with Inconel or other nickel alloys.

You are correct. If its gonna last that's an investment worth having. What did that run you tube wise?

 

[Natlek]

The diffuser was the big sticking point for me in making one of these. I wonder if the expansion issue could be alleviated by bringing the air inlet in from the side and drilling into the fire brick so it terminated inside the brick rather than below it.

The other thought I had is remove it from the high heat chamber entirely and leave 4-6" of the tube that contains the diffuser outside the heat chamber. It will still get hot obviously, but maybe at that point you could hold 1850-2000 on the tube inside the chamber and only be 14-1500 on the diffuser portion.

Well kuraki ........last two years I try whatever not for diffuser .Soft fire brick are not good /for me at least/ they make ONE big bubble come up AND every time in same spot on surface ...and no mix sand good ,have no idea why that is case ? And they break on high temp .I try ceramic filter ....works excellent but at the end break too ..........Now I think that I found best solution for this problem ,at least I think so Carbon ! I will not write to much because of my english .I try this on cold and this kind of diffuser mix sand perfectly ....really perfectly , small bubble come out in many places and there is ZERO resistance when I put steel in sand . Carbon is some strange material when it comes to heat ........Look picture , I can hold for hours that carbon cloth on flame and next second I can hold it with hand ....not even warm ??? I can even put my finger on that thin carbon cloth while is steel under flame ,and there are only three layer cloth ??? For now I will try only with about inch thick carbon cloth layer between this two stainless plate .I m 100 % sure that temp under that two plate will be very, very LOW ! Tube is thin walled 3 inch dia. but it is seamless inconel .....once im my life I make some muffler for some bike That carbon cloth hold my 100 grit AO with only one layer and I think that should hold sand .....I will try this days how all would work with heat ....
carbon fiber diffuser

I try this even with big torch too.............no way I can heat all three layers.NOW I wonder if carbon is good for insulation HT oven ?????????

All this parts are stainless of course ... carbon cloth will be betwen this two round plate .....that three M6 stainless bolts are spacer for plate ,under that is air chamber ..

hole for argon or air..........

One picture will explain better than me with my english

I don t know , for now I can t find why this should not work on HIGH temp for stainless ...

PS. I forget that in this thread we have this short video ......THAT is what i get too with soft fire brick ...........And I have no answer WHY ?

 

[Daren McIntosh]

This is an excellent thread and a wealth of information. Gting, Natlek, any updates to share? How are your diffusers working out?

 

[Gting]

I have semi fixed the single bubble problem. Having the tube perfectly verticle makes all the different with the diffusion.

As for how it's all holding up. As of now the same soft fire brick has lasted me 8 months with no cracks. That is I don't get mine above 1700 ever. I HT carbon steel only and only normalize up to 1675 for a few steels.

For now it works perfectly for my intentions.

Well kuraki ........last two years I try whatever not for diffuser .Soft fire brick are not good /for me at least/ they make ONE big bubble come up AND every time in same spot on surface ...and no mix sand good ,have no idea why that is case ? And they break on high temp .I try ceramic filter ....works excellent but at the end break too ..........Now I think that I found best solution for this problem ,at least I think so Carbon ! I will not write to much because of my english .I try this on cold and this kind of diffuser mix sand perfectly ....really perfectly , small bubble come out in many places and there is ZERO resistance when I put steel in sand . Carbon is some strange material when it comes to heat ........Look picture , I can hold for hours that carbon cloth on flame and next second I can hold it with hand ....not even warm ??? I can even put my finger on that thin carbon cloth while is steel under flame ,and there are only three layer cloth ??? For now I will try only with about inch thick carbon cloth layer between this two stainless plate .I m 100 % sure that temp under that two plate will be very, very LOW ! Tube is thin walled 3 inch dia. but it is seamless inconel .....once im my life I make some muffler for some bike That carbon cloth hold my 100 grit AO with only one layer and I think that should hold sand .....I will try this days how all would work with heat ....
carbon fiber diffuser

I try this even with big torch too.............no way I can heat all three layers.NOW I wonder if carbon is good for insulation HT oven ?????????

All this parts are stainless of course ... carbon cloth will be betwen this two round plate .....that three M6 stainless bolts are spacer for plate ,under that is air chamber ..

hole for argon or air..........

One picture will explain better than me with my english

I don t know , for now I can t find why this should not work on HIGH temp for stainless ...

PS. I forget that in this thread we have this short video ......THAT is what i get too with soft fire brick ...........And I have no answer WHY ?

 

[Natlek]

I have semi fixed the single bubble problem. Having the tube perfectly verticle makes all the different with the diffusion.

Yes , I discovered that too..... There was another thread about sand pot , if you have not already found it ......... https://www.bladeforums.com/threads...alt-replacement.1417680/page-14#post-18593413

I will quote my self Ok , today on a lunch break I ate only one sandwich....... something came to my mind and I had to try You know WHY bubble on this live picture come only in one place/location ? Because tube is not exactly in the vertical position . Thats it ..... that's why I have same problem.........I did not pay attention to it at all Even with this new diffuser I managed today to get bubble only in one side , just little angle on tube and ONE BIG bubble come out to say hello you stupid Obviously the air even in tube will not go aside but right up So I think that tube MUST be in a perfectly vertical position to get maximum in mixing sand .....

PS . I have no access here to kaowool but I think that will work in this my solution for diffuser ?