Lune Valley twin tube boiler firebox/grate question.

A special section just for steam engines and boilers, as without these you may as well fit a sail.
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ianrichards
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Lune Valley twin tube boiler firebox/grate question.

Post by ianrichards » Sat Dec 09, 2017 9:13 pm

I’m in the final throws of deciding what to do about the grate, but need to know the following.
How far back does the grate need to go?
Obviously beneath the copper tubes, but does the lower one of the twin tubes also need to be completely above the grate?
I ask the question because I can source cast iron bars that are 12” long and these would reach to half way under the lower tube.
Apologies for not remembering the name of the lower tube, perhaps someone can remind me.
Thanks
Ian
Mike Cole
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Re: Lune Valley twin tube boiler firebox/grate question.

Post by Mike Cole » Sun Dec 10, 2017 9:51 am

Hi Ian
its the steam drum and the mud drum for the tube names.
On mine the grate is only under the copper steam pipes and stops at the mud drum. You get very little extra heating area by extending it under the drum.
I buldt a fire brick wall around all 4 sides of the grate. I did not want the coals to be touching the steel drum.
Mike Cole
ianrichards
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Re: Lune Valley twin tube boiler firebox/grate question.

Post by ianrichards » Sun Dec 10, 2017 10:01 am

Thanks Mike.
With that knowledge I think I’m there now.
I’ll build as per your design and that means that I can use the shorter cast iron replaceable bars.
They cost £38 for a pack of 8 including the postage, which is a massive saving compared to 316.
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Re: Lune Valley twin tube boiler firebox/grate question.

Post by RGSP » Sun Dec 10, 2017 12:22 pm

ianrichards wrote:Thanks Mike.
With that knowledge I think I’m there now.
I’ll build as per your design and that means that I can use the shorter cast iron replaceable bars.
They cost £38 for a pack of 8 including the postage, which is a massive saving compared to 316.
They MAY last better as well. I have a multi-fuel stove which has been in daily winter use since 1982, and still has most of its original cast iron fire bars. A few of them started to bend upwards seriously some years ago, and later developed big cracks. I was working in a Materials Science and Metallurgy department at the time, and asking the experts suggested the problem may well have been phosphorus contamination of the cast iron via burning bones in the stove. In any case, replacement bars were available for a few pounds each, and have been fine
ianrichards
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Re: Lune Valley twin tube boiler firebox/grate question.

Post by ianrichards » Sun Dec 10, 2017 3:39 pm

Thanks guys
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Re: Lune Valley twin tube boiler firebox/grate question.

Post by Mike Rometer » Sun Dec 10, 2017 4:44 pm

If burning wood I suggest that you may have fewer problems with firebars anyway. It seems that clinker from poor coal is the biggest killer, it glues to the bars and causes localised overheating.
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ianrichards
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Re: Lune Valley twin tube boiler firebox/grate question.

Post by ianrichards » Mon Dec 11, 2017 6:03 pm

I’d better do the same, but why?
Being a novice I didn’t realise that coal touching the steel drum would have been a problem.
Also, I’ve lined the whole unit with ceramic board, but someone mentioned that I should fill the voids above and behind the drum with a ceramic fibre.
Your thoughts/advice greatly appreciated ... as always.
Ian
Mike Cole wrote:Hi Ian
its the steam drum and the mud drum for the tube names.
On mine the grate is only under the copper steam pipes and stops at the mud drum. You get very little extra heating area by extending it under the drum.
I buldt a fire brick wall around all 4 sides of the grate. I did not want the coals to be touching the steel drum.
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