To the basement, or to the scrapyard? My attempt to resurrect a Tarm Excel 2200 Wood Gasification boiler

[aczlan]

I picked up a Tarm Excel 2200 Gasification Wood Boiler this week, from the tag it appears to have been made in 2001:

It is a Wood/Oil (or Wood Propane) boiler, on the wood side it heats the wood till it smoulders, then burns the gas/smoke at around 2000F below the firebox:

Picture from: Tarm Furnace | Excel 2000/2200 | Wood and Coal Furnace Parts

A demonstration video of the next size down (the Excel 2000):




The previous owner was using it and it sprung a pinhole leak in the back of the firebox, they ran it (with the pinhole) for about a month on oil until they could get someone in to replace it (they put in a wall mount condensing gas boiler to replace it).
Not sure how often it got cleaned out as it had a lot of ash buildup/creosote buildup inside, here is a picture shortly after I started:

And where I stopped for the night. Can someone confirm that the corners (circled in red) should be square? It looks like they should be, but I don't want to break something if they are supposed to be angled. It appears that there is a bunch of creosote or ash built up there which is a solid lump:

IIRC, the leak is somewhere around where the yellow circle is, if not its a few inches below that:

I pulled out about 10 gallons of ashes out and that was just the easy to get stuff:

The flame tunnel from somewhere in the clean out process:

And how I left it for the night, 200w fan heater in there to warm things up and hopefully dry things out (sitting on a metal plate to keep it dry), not sure if the refractory absorbed any water (or if it can), but I figure that if everything is dry, it will be easier to work with than if its wet:

The plan is to get it cleaned out, then tape my needle scaler to a stick and pound the back wall until its clean.
Once its clean, I will look for pitting, pressurize the "tank" and spray soapy water on the back wall to see if there are any other leaks.
If there are not, it will get welded up and installed in the basement this spring/summer.
If there are, it will get sent to the scrapyard.

Aaron Z

 

[aczlan]

Made a little progress the next night, adapted my needle scaler to get the back wall (while keeping my face out of the firebox and thus breathing clean air):

After doing a test patch:

Where I ran out of time and stopped:

The nastyness on the scaler from what was still damp:

Liking what I see so far of the top 2/3 of the back wall, the creosote just about fell off when I took the scaler to it.
Lower 1/3 (where the hot wet ash has sat against the steel for the past month) is more like what I was expecting to find.
Aaron Z

 

[aczlan]

A few pictures from Friday night:
Air hammer with a chisel blade made short work of the clumps of creosote at the bottom of the walls, they looked like lumps of coal:

Some chunks in a pan, 1/2" diameter pin for scale:

Cleaned out firebox (for now, will probably clean more once it's all dry):

Dug a lot of sludge out from under the vertical tubes in the back, no pictures, but there was ash almost to the bottoms of the tubes.
One more night with the heater in the firebox and then it gets moved below to try to dry out the lower section.
Next up is to shorten the wooden "handle" on the needle scaler so it fits completly inside the firebox and I can get at the lower section straight on instead of at an angle.
Aaron Z

 

[aczlan]

Someone on Hearth asked about using a angle grinder vs a needle scaler.
I thought about using an angle grinder with a wire wheel, but controlling it that far out when it "grabs" would be difficult and it would throw a lot of dust around.
The scaler and air hammer throw little or no dust that makes it out of the firebox and are easier to control.


Aaron Z

 

[aczlan]

Nothing much happening today, replaced some seals in my pallet jack so I can move this beast around the shop easier than with my forklift (its at the edge of what I should be picking up from the end with my little walk behind forklift due to how long it is).
The pallet jack seals were bad enough that I could not pump the handle fast enough to lift the boiler up when I was trying to bring it home.


Aaron Z

 

[aczlan]

Took the top cover off of the exhaust area, 1-2" of fine silty ash went right into the vacuum cleaner:

Oil side was a little better:

All nice and clean (still need to clean inside the tubes):

Will need to figure out why this damper sits open a little and replace the lid gasket as it's shot:

Need to get the lower section rinsed out and finish vacuuming out the firebox, but I haven't found any showstoppers yet.


Aaron Z

 

[aczlan]

Took it outside and rinsed it out with a hose, got enough out for now to work on it without getting covered in ash, will pressure wash things later.
Inside the firebox:

More to the front of the firebox:

Down below:

Where I washed out out:

I now have a box fan sitting on the cleanout opening pushing air through to push the "loose water" out.
Before I go to bed, I will put the heater in the bottom and hopefully finally start to dry everything out.

Aaron Z

 

[CarterKraft]

Not a clue what your doing here, could be cleaning out the grease trap at KFC for all I know, but I'm in fr the adventure.

 

[aczlan]

Not a clue what your doing here, could be cleaning out the grease trap at KFC for all I know, but I'm in fr the adventure.

It should be an adventure, complete with welding on a pressure vessel and possibly casting my own refractory cement pieces

At this point, I am trying to:
1. Get it cleaned out enough to pinpoint the leak
2. See if there are more leaks
3. (hopefully) Get it working so I can get more of the BTUs from the wood that I am burning moved into the hot water heating system in my house.

This is what the firebricks on the bottom of the firebox should look like:

Aaron Z

 

[aczlan]

Had a conversation with my neighbor (who has run/maintained steam boilers for years at work) and he suggested when I'm ready to fully dry it out and/or to finish curing any new refractory cement to stick a salamander heater in the opening where you would load wood and let that run for an hour or so, let it cool off and repeat.

That should get it up to a couple hundred degrees, let me get the first couple of stages of curing the refractory cement taken care of in a controllable fashion (without having to fill it with water and try and run it slowly without having it hooked up to the house).

That should also let me finish drying out whatever water has been absorbed into the fire bricks in a controlled fashion.


Aaron Z

 

[aczlan]

Got the back wall cleaned off tonight:

Surface rust, but it doesn't look bad. No significant pitting or erosion that I could find.


Started cleaning off the door (so it doesn't put creosote on my arm all the time) and it is the rusty mess that I was expecting the back wall to be:

Going to have to replace the insulation and the round vent adjuster as it is rusted through.

Snapped off my first bolt (lower left on the door), will weld a nut to it and see if it comes out.
If not, I will center punch, drill and try not to snap off an extractor in it.


Aaron Z

 

[aczlan]

Pressure tested it today, found 4 leaks in the back wall.
Top right is the one that was leaking when I saw it, the others are pinholes:

I am going to bet that the gasification part did NOT work properly after they replaced the firebricks, the nozzle brick was installed backwards so they had no flow through the nozzles.
This end was towards the door:

Instead of this one (they're supposed to be one unit, but it broke in the middle and now there's two halves):

The backside of one of the nozzle bricks:

The outer bricks look ok:

Some closer pictures of the back wall after taking a wire wheel to the leak points:

Aaron Z

 

[Chkn]

No idea what’s happening but I hope you can salvage it. 😂

 

[aczlan]

No idea what’s happening but I hope you can salvage it. 😂

Me too, I am guessing that they pressed the "ribs" into the back wall and that created stress points as well as thinner metal there from stretching it because the only leaks seem to be at the ends of the ribs.
Thinking the best fix may be to cut them out and weld a patch plate either over each one, or over the whole back wall.

Aaron Z

 

[aczlan]

Curiosity got the better of me, so I went out and drilled out the worst of the leak points with a 3/16" drill bit.


It looks like I was incorrect in my assumption, I was thinking that these were dimples stamped into flat plate, in actuality it was a flat plate that had slots cut into it and these are reinforcing slats or stays that are welded from one wall to the other to keep the walls from spreading apart.
Thanks dougtrr2 on TBN and Peakbagger on Hearth for pointing that out.

If my HF micrometer is accurate, the metal has not eroded, it is still 1/4" thick.

The leak is a crack at the point where the stay is welded into the wall plate.

A couple of pictures:

Also found a couple more leaking stays on the sides, one on each side.
Right side:

Left side:

So I guess the question is, do I weld these up with the stick (and if so which rod), or with a MIG...
dougtrr2 on TBN had the same issue with one and and said that the guy he had work on it had better luck with a stick than with a MIG and I may end up chasing my tail with leaks on this.
I am thinking that if I can get it to weld up that I may want to hit all the stays in the firebox as a precautionary measure, but that could also mess with the HAZ and make more cracks occur.
Decisions, decisions , decisions...


Aaron Z

 

[TrailTamer]

I am thinking that if I can get it to weld up that I may want to hit all the stays in the firebox as a precautionary measure, but that could also mess with the HAZ and make more cracks occur.
Decisions, decisions , decisions...

How hot that area will be when running full heat?

Hot enough to ‘anneal’ HAZ out?

 

[aczlan]

How hot that area will be when running full heat?

Hot enough to ‘anneal’ HAZ out?

Inside the boiler will probably be under 250F
In the firebox may be more, but that part should be relatively cool (500ish max?).
The way it works is to have the fire in the bottom of the firebox and keep the top of the firebox at a lower oxygen level so it pulls the smoke from the smouldering fire down, adds air (the firebricks with holes in them from the other day) and it is supposed to light the smoke on fire and burn it at around 2000F.


Aaron Z

 

[aczlan]

Pulled out the DHW (Domestic Hot Water) coil to look at the inside of the vessel last night, this is looking across above the top of the firebox, the two cylinders on the far side are thermowells:

Looking down the sidewall of the firebox from the DHW opening:

Looking over and toward the back/chimney from the DHW opening

The DHW coil

All in all, it looks pretty clean inside, I think the leaks are just from the welds cracking.


Aaron Z

 

[ThePanzerFuhrer]

In my experience when the steel starts cracking inside the fire box of a boiler it’s time to scrap it. Any fixes are temporary and will fail in short order. That is unless you replace all the steel inside of the boiler.

The thermal cycling has fatigued the steel and no matter how you weld it, it will crack in a short order.

 

[aczlan]

In my experience when the steel starts cracking inside the fire box of a boiler it’s time to scrap it. Any fixes are temporary and will fail in short order. That is unless you replace all the steel inside of the boiler.

The thermal cycling has fatigued the steel and no matter how you weld it, it will crack in a short order.

Is that the case when the cracks are in the weld vs the steel? All the cracks I have found so far have been in the welds, not in the steel.

Aaron Z

 

[ThePanzerFuhrer]

Is that the case when the cracks are in the weld vs the steel? All the cracks I have found so far have been in the welds, not in the steel.

Aaron Z

I’m my experience with the wood boilers yes. You can weld up the cracks but in about a year or so it will crack and start leaking in the haz again. Maybe if you oxy fuel weld them they may last longer.

Imo the secret to getting the shit to last is nice steady state running. No extreme temp swings to cycle the steel. I have a neighbor who seems to go through wood boilers every 10 years. I’m pretty sure it’s because he burns boxes in it from his motorsports shop. The boxes quickly raise the fire box temps cycling the steel.

 

[aczlan]

I’m my experience with the wood boilers yes. You can weld up the cracks but in about a year or so it will crack and start leaking in the haz again. Maybe if you oxy fuel weld them they may last longer.

Looking at this picture and discussing the boiler with the "old timers" at work:

We are thinking that the root cause of the cracks is stress risers coming off of the corners of the square holes punched in the walls that the stays go through.
My plan is to clean up all the points where the risers are welded in, drill all 4 corners with a 3/16" drill bit and weld around each one.
If it works, great. If not, it will either get migrated to the scrapyard, or make a trip to MI (if the guy up there still wants it)

Imo the secret to getting the shit to last is nice steady state running. No extreme temp swings to cycle the steel. I have a neighbor who seems to go through wood boilers every 10 years. I’m pretty sure it’s because he burns boxes in it from his motorsports shop. The boxes quickly raise the fire box temps cycling the steel.

Related, these are all in the bottom half of the firebox where it would change temperature more when the boiler cycles on and off as the "flame" goes down to get to the exhaust.

Aaron Z

 

[Chkn]

Updates?

 

[aczlan]

Updates?

Nothing much, tried welding one spot and made it worse.
Need to grind my mess out, then get someone better than me in to weld it up and it's been lower on the list than many other priorities.

Aaron Z