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Watertube boiler casing lining

Posted: Fri Jul 27, 2018 1:12 am
by marinesteam
Been taking a rough pass on CAD for the design of the casing for my two drum water tube boiler. Searching through the forum and Google it appears that the majority of the casing that actually show enough detail to make a determination that the casings are lined with steel sheet with the insulation sandwiched between the inner sheet and outer material of the casing.

Is the consensus of the forum to have an inner liner protecting the ceramic insulation?

Also, how much should one worry about the heat transferring from the inner liner to the outer sheeting though fasteners and support tabs? Is it a non issue or do I need to go through extraordinary effort to build a casing that keeps the inner and outer from having any structure between them that may transfer heat?

Thanks

Ken

Re: Watertube boiler casing lining

Posted: Fri Jul 27, 2018 1:43 am
by barts
I used stainless sheet (thin - 22 gauge or so) for the inner sheet. The firebox itself gets insulated w/ something serious like castable refractory if has fire hitting it directly. I used an inner and outer frame to fasten the inner and outer casings; no real problem w/ heat transfer. Again, if the flames hit the inner casing, you'll have problems w/ heat.

The silica fiber stuff is pretty fragile after some heat cycles - I think it should be covered to last.

- Bart

Re: Watertube boiler casing lining

Posted: Fri Jul 27, 2018 5:46 pm
by Mike Cole
I am used a stainless steel mesh rather than a solid sheet, it is holding up well , at a guess around 3 to 4 mm hole size. Do not worry about heat transfer via fixings. and I have used fire bricks for the lower part where the coal bed is.

Re: Watertube boiler casing lining

Posted: Fri Jul 27, 2018 9:35 pm
by TriangleTom
What are you using as insulation?

Re: Watertube boiler casing lining

Posted: Fri Jul 27, 2018 10:24 pm
by barts
I used 1" thick FiberFrax blanket. Fiberglas would also work where it doesn't get too hot. Firebox is made from castable refractory on the inside, plus Fiberfrax.

Some pictures pre-castable refractory here: http://www.smaalders.net/bart/boiler.html

- Bart

Re: Watertube boiler casing lining

Posted: Fri Jul 27, 2018 11:45 pm
by marinesteam
Thanks for the feedback guys.

I was thinking of using Superwool HT board or similar http://www.morganthermalceramics.com/me ... boards.pdf

Ken

Re: Watertube boiler casing lining

Posted: Mon Jul 30, 2018 4:21 am
by barts
This will prob. work just fine. Keep in mind that for trailerable boats, the most difficult environment may well be traveling over rutted roads rather than steaming around. I once tried lightweight firebrick - great insulator, but could not deal with shock loads from our admittedly rough roads. Otter was traveling 3000+ miles a year on a trailer, and we were steaming perhaps 40...

- Bart

Re: Watertube boiler casing lining

Posted: Mon Jul 30, 2018 4:06 pm
by marinesteam
Bart,

That's a good point, one I hadn't thought about. I'll look into the durability of the board, but will consider blanket now as well.

Thanks

Ken

Re: Watertube boiler casing lining

Posted: Tue Jul 31, 2018 4:39 pm
by malcolmd
I used a 1 inch ceramic fibre board from vitcas.

https://shop.vitcas.com/ceramic-fibre-b ... board.html

You can cut it with wood working tools or serrated knife. No inner steel liner.

See blog for more details on insulation and casing

https://sy-befur.co.uk/2017/07/04/boile ... nd-funnel/

Re: Watertube boiler casing lining

Posted: Tue Jul 31, 2018 6:13 pm
by marinesteam
Malcom,

IIRC your firing with oil. I am leaning toward solid fuel. Do you think the insulation would hold up in the "firebox" area? I suppose I could line only the box area with firebrick or steel.

Thanks

Ken