Author Topic: Cleaning boiler tubes.  (Read 3345 times)

Online Gas_mantle

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Re: Cleaning boiler tubes.
« Reply #30 on: January 17, 2018, 08:50:10 AM »
It was originally designed as a coal fired boiler - I have got some notes and plans I can email if you were interested.

I have bought some materials to mount the boiler to a base, my intention is to fabricate a 'box' about 1.5" high for it to attach to and to make an opening with a door at the front. The door will regulate airflow and allow access to the firegrate for cleaning etc.

I didn't want to create a full blown build log here but I did think of taking a few photos to show how the idea develops including adding a water tank etc.

Online Gas_mantle

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Re: Cleaning boiler tubes.
« Reply #31 on: January 19, 2018, 09:43:58 PM »
One other thing you mentioned the other day was that you are going to raise the bottom of the whole boiler, how will you control the much increased amount of air getting in as that will make a coal fire burn even faster?

Now that I have the materials to make a base I've been thinking a bit more about this.

My boiler dia is 5" so the surface area of my fire grate is 20sq" approx (assuming the fire hole door is closed all the air needed for combustion passes through this 20sq"). At the moment using my boiler as I have been using it without a base the only air intake (apart from the fire hole) is a cut away slot on the botton of the boiler front - I estimate this to be about 3sq".  (Looking at my earlier photo may help)

The idea is to blank off the front cut away slot and have all the air needed to enter a 'box' that the boiler will sit on with a 5" dia hole under the grate -  in other words instead of having a 3sq" of air intake going to a 20sq" grate I can substantially increase that but control it via a 'air door'

I'm really not sure how much air a boiler of this size and design needs so I'm kind of guessing here but I dont think it would be difficult to get nearly 20sq" of air holes in the 'box'.

I guess what I'm kind of getting at is does it sound right to have the same amount of air intake surface area in the base as the fire grate area of 20sq" ?

In practice the area of the grate exposed to air is probably closer to 15sq" than 20sq" allowing for fire bars but you see what I'm getting at.

Anyone got any thoughts before I start cutting and soldering ?

Thanks
Peter.

Offline Jasonb

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Re: Cleaning boiler tubes.
« Reply #32 on: January 20, 2018, 07:18:46 AM »
You don't need anywhere near the area of the grate as an air supply, will post a bit more later as off out.

Online Gas_mantle

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Re: Cleaning boiler tubes.
« Reply #33 on: January 20, 2018, 01:51:19 PM »
Part of the reason for wanting to raise the boiler and have it sitting on a box is to enable me remove the grate while leaving the boiler fixed, at the moment the air intake isn't large enough but it isn't practical to widen to the size needed.



I thought by soldering a copper ring onto some brass sheet with a 5" dia hole cut out and making a door at the front I could get increased air flow and allow removal of the grate.



To be honest my method of allowing access to the grate isn't ideal, I can see it being fiddly to slide in then up into the fire box but I can't really think of another solution that is fairly easy to make.


Offline Stuart

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Re: Cleaning boiler tubes.
« Reply #34 on: January 20, 2018, 03:10:02 PM »
One point I forgot to mention is make sure you sieve / riddle your fuel you do not want to stoke with dust it will get up the tubes abut there


Stuart
My aim is for a accurate part with a good finish

Online Gas_mantle

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Re: Cleaning boiler tubes.
« Reply #35 on: January 20, 2018, 03:50:57 PM »
One point I forgot to mention is make sure you sieve / riddle your fuel you do not want to stoke with dust it will get up the tubes abut there


Stuart

Thanks Stuart, I'll bear that in mind :-)

My gut feeling is that the existing air intake slot is a tad small (but that's just a guess), even if it isn't too small I think it will be better to have the air entering from a full 360o rather than just at the front as it is now. 

I now have an electric blower meaning I'm not relying on burning a lot of wood to get it started so I'm hoping that with better airflow as well I can reduce soot and generally get better combustion :-)

Offline Jasonb

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Re: Cleaning boiler tubes.
« Reply #36 on: January 20, 2018, 05:08:48 PM »
Right just a couple of examples of grate to damper (air inlet) size to show that you really don't need much more if any.

2" Fowler has a 5" boiler, grate area of 16sq in and the damper when fully open will give about 3 sq in. This is an engine design that can do real work and will happily pull two adults about on coal.

2" Superba has a 6" dia boiler, grate area of 25sq in and the damper when open would give about 5sq in area. Again an powerful engine capable of real work.


Also you should not be opening the fire door to get more air into the boiler as that has little effect on the fire, the air needs to come from below to feed the fuel with oxygen, not just waft over the top of the coals and then up the chimney.

Your best bet to regulate the air would be to add a second slot at the rear of the boiler and then make two slots in that ring you have but allow the ring to rotate which will allow you to control how much of the two boiler slots are open to air.

Online Gas_mantle

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Re: Cleaning boiler tubes.
« Reply #37 on: January 20, 2018, 05:19:44 PM »
Thanks Jason, it sounds like my grate and air intake are comparable to the 2" Fowler.

I was planning on having the copper ring soldered to the brass plate as a firm support for the boiler to sit in, I had considered drilling a few holes around the circumference to allow air to enter more evenly. I do have a ceramic burner that is a good fit so although I intend to use it on coal I want to make a hole in the ring so that a gas feed can pass through.

I'll try and make a start tomorrow and hopefully do a bit more to the Muncaster  :)


Online Gas_mantle

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Re: Cleaning boiler tubes.
« Reply #38 on: January 22, 2018, 02:03:10 PM »
I guess this thread has now drifted off the original topic and I maybe should start a mini build log.

Anyway, I've made a start on the base ring, it was about 6mm over size so to get a close fit I've needed to saw out a piece and solder it back together. I really struggled with a small Mapp gas torch getting enough heat in and now have my doubts as to wether I'll be able to solder it to 3mm thick brass plate  :(

It did eventually work and although the solder didn't fully run at the top it was about as good as could I expect.



It is a reasonably good fit on the boiler but neither the ring nor the boiler itself are 100% circular so it does fit better in certain orientations.



Next thrilling instalment - soldering the ring to the plate and cutting a 5" dia hole  :pinkelephant:



« Last Edit: January 22, 2018, 02:14:14 PM by Gas_mantle »