[Stoves] black sheet corrosion retort kiln bottom plate

Fri Sep 20 07:43:13 CDT 2019

Hi Crispin,

Thats very interesting - what type of stainless steel would you recommend
for KCJ style jikos with lots of small bends?

Best,

Teddy

Teddy Kinyanjui
Sustainability Director

             <https://www.facebook.com/CookswellJikos>
<https://www.instagram.com/cookswelljikos>
<https://twitter.com/cookswelljikos?lang=en>

On Fri, Sep 20, 2019 at 12:29 AM Crispin Pemberton-Pigott <
crispinpigott at outlook.com> wrote:

> Dear Chris
>
>
>
> I suggest you consider trying SS 409 which is typically about 1.5 times
> the price of mild steel. It can be thinner so if 3mm MS was working in
> terms of strength, 2mm SS 409 will work as well. It is much stronger.  The
> patent has expired so it is available from multiple sources.
>
>
>
> Being an SS, the heat transfer rate will be lower, something close to ½
> that of MS. Being thinner will compensate for some of that. Assume you will
> lose 1/3 of the heat transferred from the fire under the end of the
> chamber, so it will take a larger external fire to get the same pyrolysing
> effect in side.   It has an operating temperature of more than 700 C which
> really suits your application.   It will go brown when heated, unlike high
> chrome stainless steel.  I suggest getting hot-rolled sheets, not
> cold-rolled because of the albedo of the CR.
>
>
>
> This material (also known as 3CR12) is difficult to cut with an angle
> grinder and cutting disk, when thick. I suggest you have it guillotined
> instead. It is very abrasion resistant. If you are forced to cut it with a
> grinder, don’t let it get red hot. Cut by moving the disk contact point
> back and forth on the cut-line.  Using a thinner disk will help (a bit).
> If it gets red hot it will harden considerably and it is already abrasion
> resistant.
>
>
>
> It cuts quite well with a saw but make sure there is adequate pressure to
> get the teeth well into the material.  In general stainless has to have a
> deep tool penetration or the surface hardens.
>
>
>
> If you are not sure what the material offered is, look for a small % of
> titanium, about 1/3 to 1/2 of a %.  It is a low chrome (12%),
> titanium-stabilised stainless steel.
>
>
>
> It can be bend in a press brake but it will not bend back.  The elongation
> is about 16% (only) so plan for a larger than normal radius such as 2T or
> 2.5T instead of 1.5. You can weld it with any stainless steel arc rod, all
> of which are made from better material.  The area around the weld will
> harden considerably.  It spot-welds very well.
>
>
>
> If you punch holes it will need close to 75% of the depth sheared, higher
> than a standard MS of 33%.  This provides a very smooth hole wall but at
> the expense of a much higher than normal pressure requirement per mm2 cut
>  Increasing the die hole clearance from 1/10thT to 1/6th or 1/5thT will
> probably reduce the punching force needed, if you don’t mind the bottom
> burr.
>
>
>
> It will laser cut well, but is a bit messy plasma cutting.  The edge will
> need to be cleaned with a grinder, and the cut edge will be hard.  Nigel PP
> warns that above some temperature the chrome atoms will let go of the
> oxidation sites and condense into droplets within the material. After that
> there is going to be some irreversible corrosion, though I think you will
> be so happy you won’t care.
>
>
>
> This material is available down to 0.3mm which is used in a double layer
> for catalytic converter housings.
>
>
>
> You can buy hot-rolled sections like angle iron made of the same material.
>
>
>
> Good luck with the demonstration.  You might want to use it in another
> thickness on top as well.
>
>
>
> Regards
>
> Crispin
>
> *From:* Stoves <stoves-bounces at lists.bioenergylists.org> *On Behalf Of *
> dr.adam
> *Sent:* Wednesday, September 18, 2019 2:53 AM
> *To:* Discussion of biomass cooking stoves <
> stoves at lists.bioenergylists.org>
> *Subject:* Re: [Stoves] black sheet corrosion retort kiln bottom plate
>
>
>
> Dear Teddy
>
> HELP !
>
> You might be familiar with metal sheet dealers in Nairobi?
>
> Near Mombasa/ Kilifi  the company komaza.com (new face of forestry) built
> one of my retort-kilns.
>
> I guess they used poor quality black sheet 8"x4", 3mm for the bottom plate
> and they complained that already after 4 batches operation they had these
> horrible holes near the fire chamber.
>
>
>
> You have any idea which kind of more heat resistant metal plates (boiler
> sheet?) might be available in Kenya, any name of a dealer? Kenya with its
> tea producing industry and use of steam boilers, should have such sheets
> available?
>
> Thanks in advance.
>
> We might see us on 5th Nov. in Nairobi Conference  :-)
>
> Chris ADAM
>
>
>
> [image: Inline image]
>
> I have even doubt they used a 3mm sheet (they paid 7500KSH for it)?
>
>
>
>
>
> On Monday, 16 September 2019, 13:03:33 CEST, Cookswell Jikos <
> cookswelljikos at gmail.com> wrote:
>
>
>
>
>
> A very interesting short video on a very clever company that's started up
> in Kenya
>
>
>
> https://www.youtube.com/watch?v=EaJNe0im-eM
> <https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DEaJNe0im-eM&data=02%7C01%7C%7C2fcaf5b88820466dca5408d73c051dd5%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637043864984174515&sdata=%2FwJ4Ta7ItgWQCIKDbITy%2F7AGr1xrkiSLZJ1B6eZjyfE%3D&reserved=0>
>
>
>
>
>
>
> Any suggestions for better sawdust burning stoves sub 10$ that could be
> locally made?
>
>
>
> Best,
>
>
> Teddy
>
>
>
>
> _______________________________________________
> Stoves mailing list
>
> to Send a Message to the list, use the email address
> stoves at lists.bioenergylists.org
>
> to UNSUBSCRIBE or Change your List Settings use the web page
>
> http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org
>
> for more Biomass Cooking Stoves,  News and Information see our web site:
> http://stoves.bioenergylists.org/
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20190920/b641f4b9/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image001.jpg
Type: image/jpeg
Size: 140289 bytes
Desc: not available
URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20190920/b641f4b9/attachment.jpg>