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Chris D

Rebuilding a 28-inch Olympic Torchbearer gas kiln

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Chris D    0

Hi folks,

 

Brand new to the site and forum, which looked like the best place for a question like this.

 

We are working on rebuilding an Olympic Torchbearer gas kiln that was purchased a couple of years ago in non-working condition. It's much like Olympic's current 28-inch offering, the Model 2831 G. One key item the kiln lacks is a floor. It fell out in pieces when the kiln was purchased. We've done enough homework to know what sort of brick, mortar, and techniques are required to remanufacture the kiln floor and have ordered an appropriate stainless steel floor/lid band from Olympic.

 

The kiln came with a six-burner setup that looks like it is probably not even original to this kiln:

 

7931808948_5e72fe11be_z_d.jpg

 

 

You can see that there would be no way to position the holes in the kiln floor for the burners so that the burners weren't right at the edge of the floor. Olympic doesn't make any six-burner torchbearers anymore. We're planning to just cap two of the burners and reposition the remaining four to be closer to the center of the floor, more like this;

 

7931808698_36a52d73c2_m_d.jpg

 

 

...only with four instead of two burners, of course.

 

My first question is this: Would there be any advantage to maintaining the six-burner setup? I don't know enough about it to have an opinion, but once we decide on a certain number of burners, we're kind of stuck with that configuration after we cut the holes in the floor, and I would like to get it right the first time.

 

We have a pyrometer that works (needs to be calibrated) and a Model K Kiln Sitter that needs some parts but should function just fine after minor repairs. The valves and gauges on the gas line are in pretty dubious condition and will have to be replaced. The kiln will eventually be connected to a home natural gas line. We've seen a dizzying array of valves, electronic wall-mounted controllers, and thermocouple devices that one can add between the cutoff gas cock on the kiln and the house line to regulate the gas flow to the kiln.

 

Building codes will dictate part of what we include, but I'd like to hear people's opinions on what a minimal setup would include between the house line and the kiln. We're not looking to automate any processes that we don't need to.

 

Thanks in advance for your help!

 

Chris

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Mark C.    1,798

I have been around a few of these kilns and 4 burners is the usual layout-The burners do need to be next to side walls as in your floor photo with two burners. That way the flame is not under the shelve but next to it as it licks up the side walls-Looks like you can modify what you have-I think 6 is overkill but more makes for more even firing.. that said that kiln size wise to me merits 4 burners.

I would not put them near center. look up where most come thru floor and follow that set up

My studio helper has the 4 burner torch bearer. The 4 burners are right near the inner walls.

She NEVER fires it as firing is free for her here in the big kilns-past 20 years.

 

The floor should be a easy build. set the burners up right and drill the holes to fit the plumbing right next to side walls.

Mark

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neilestrick    1,381

You'll need to find out how many BTU's those burners put out to know if they'll work with just 4 instead of all six. My gut says they will, since it's not that big of a kiln, but my gut has been wrong before.

 

At the very least, your burner system should have a baso valve connected to a ring pilot that feeds all the burners. Building codes, should you choose to follow them, could get MUCH more complicated, with digital controllers and electronic flame sensors ($$$).

 

Sitters aren't made for gas kilns. A digital high temp shutoff connected to a solenoid gas valve would be the way to go there.

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Chris D    0

I can't tell you much about the Torch bearer but using a home gas line, you'll need to be as close to the meter as you can be.

Marcia

 

Thanks Marcia,

 

Do you say that because home gas line pressure is generally low? The people at Olympic told us that you don't need a pressure regulator on a home gas line since it's already generally at the correct pressure for the kiln. Perhaps it's a volume issue?

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JBaymore    1,432

You are correct about the laws governing the installation. Contact the gas company / building inspector for the town to see what will be required for flame safety when connecting such a unit to natural gas. In most locales that I have dealt with putting in gas kilns, natural gas supplies can often pose some serious "standards" upon such installations.

 

In many cases you don't HAVE options to decide upon from that "dizzying array"....... the town / gas company will tell you what you need to do. They won't hook it up if the flame safety system is not there.

 

Absolute minimum in most locations is what is known as continuous pilots on each burner that are each indivdually monitored for positive ooperation. Ring burner type pilots usually will not gtet approved for natural gas installations.

 

You might ultimately be better off setting that thing up on a portable propane cylinder array and keep it off the natural supply. Price out both options.

 

best,

 

..................john

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Chris D    0

I think 6 is overkill but more makes for more even firing.. that said that kiln size wise to me merits 4 burners.

I would not put them near center.

....

The floor should be a easy build. set the burners up right and drill the holes to fit the plumbing right next to side walls.

Mark

 

Thanks Mark. That's what I was thinking. Perhaps more even, but maybe overkill. I'm figuring on the floor being pretty simple, and thanks for pointing out the merits of locating the burners near the outside. My plan was actually to just extrapolate the measurements from photos of other kiln floors. :)

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Chris D    0

You'll need to find out how many BTU's those burners put out to know if they'll work with just 4 instead of all six. My gut says they will, since it's not that big of a kiln, but my gut has been wrong before.

 

At the very least, your burner system should have a baso valve connected to a ring pilot that feeds all the burners. Building codes, should you choose to follow them, could get MUCH more complicated, with digital controllers and electronic flame sensors ($$).

 

Sitters aren't made for gas kilns. A digital high temp shutoff connected to a solenoid gas valve would be the way to go there.

 

Hey Neil,

 

Thanks for the feedback. Solid gold. The previous owner had the kiln on natural gas, so I assume that they're the proper jets for the setup we're putting together. That said, do you know off-hand if BTUs can be estimated based on the diameter of the jet orifice? That would probably be too simple...

 

I'm curious about sitters not being for gas kilns...is that because of the convective heat of an open flame, as opposed to the radiant heat of an electric kiln? Not sure if I have the right words there, but my idea is that the gas heat is much more intense around the outside of the kiln from the very start...so a reading from the spot where the sitter's cone is would be much higher than the rest of the kiln? I'm not the ceramicist on the team, so many of these concepts are new to me. I wonder why the original owner outfitted the kiln with a sitter if they're not for gas kilns? Hmm...

 

Thanks for the tip on the high-temp shutoff. I was also thinking about replacing our old pyrometer with a homebrewed system of parts from these guys...maybe even multiple sensors at different locations in the kiln?

 

Thanks again!

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Chris D    0

 

You might ultimately be better off setting that thing up on a portable propane cylinder array and keep it off the natural supply. Price out both options.

 

 

John,

 

Thanks much for this heads-up. I've learned not to talk too much about skirting codes in forums, since it tends to get people heated up. No pun intended. :) That said, the propane option is one we hadn't really thought of. This would add an element of portability, too.

 

Makes me wonder where it's okay to install the "stock" kilns that don't even have pilots and have to be lit with fire sticks! Ha!

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neilestrick    1,381

That said, do you know off-hand if BTUs can be estimated based on the diameter of the jet orifice? That would probably be too simple...

 

I'm curious about sitters not being for gas kilns...is that because of the convective heat of an open flame, as opposed to the radiant heat of an electric kiln? Not sure if I have the right words there, but my idea is that the gas heat is much more intense around the outside of the kiln from the very start...so a reading from the spot where the sitter's cone is would be much higher than the rest of the kiln? I'm not the ceramicist on the team, so many of these concepts are new to me. I wonder why the original owner outfitted the kiln with a sitter if they're not for gas kilns? Hmm...

 

Thanks for the tip on the high-temp shutoff. I was also thinking about replacing our old pyrometer with a homebrewed system of parts from these guys...maybe even multiple sensors at different locations in the kiln?

 

Thanks again!

 

Yep, the Omega stuff would be a good way to go. As for the sitter, the metal parts will degrade quickly if you're planning on firing in reduction, just like elements would. You could use it, but you'll probably be replacing parts fairly often.If you're going to have a digital shutoff anyway, it's really not necessary. I even went as far putting a simple timer on my burner control system.

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Chris D    0

 

Yep, the Omega stuff would be a good way to go. As for the sitter, the metal parts will degrade quickly if you're planning on firing in reduction, just like elements would. You could use it, but you'll probably be replacing parts fairly often.If you're going to have a digital shutoff anyway, it's really not necessary. I even went as far putting a simple timer on my burner control system.

 

Nice. Thanks again. This is what I was hoping to hear, and what you say about the sitter makes sense (and explains the destroyed state of the kiln end of the sitter we have).

 

Firing in reduction was the main reason a gas kiln was acquired instead of electric, so we'll be leaving the sitter out of the final equation.

 

I need to do some homework, but I hope you don't mind if come back fishing for specifics on your burner control system eventually. We're pretty much "babes in the woods" on this front.

 

 

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neilestrick    1,381

 

Absolute minimum in most locations is what is known as continuous pilots on each burner that are each indivdually monitored for positive ooperation. Ring burner type pilots usually will not gtet approved for natural gas installations.

 

 

I set up a Laguna gas kiln a couple of years ago, and it had the ring type pilot system. There was a spark ignitor and flame sensor at one end, but that was it. The pilot flame could have gone out at any point beyond the first and the system would not have known it. Geil kilns used to have a ring pilot as well, just a long pipe full of holes boing around the entire bottom of the kiln. Are you telling me that Geil and Laguna or any other brand of venturi burner-based system is putting in ignitor and sensor at every burner now? That would get incredibly pricey, as each burner would have to have its own control module, too. This is doable in a power burner system like Bailey or Alpine because you only have two burners. A Fireye module (retail) is $700 or more, plus $150 for a UV scanner. Take that times 8 or more burners and you've got some mighty expensive burner systems. I just don't see how they could be putting a $6000 burner system on a $12,000 kiln.

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Mark C.    1,798

I have never seen any sort of setter on a gas kiln like the one in photo-that one looks to be for an electric kiln.Reduction will kill that thing.

Mark

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atanzey    6

My Torchbearer has a kiln sitter that look just like that. It sits right in the line of fire, and I rarely use it anymore because it trips too soon. We're in the process of reconfiguring the kiln, and moving that out of line of the burner is one of the things I hope to acheive. Not that it's too important, because I've learned to fire without it! We got a double display pyrometer and two thermocouples - really cool after trying to move one thermocouple from top to bottom....

 

We changed out the burners, and are in the process of putting individual pilots and thermocouples on. Mine is only an 18" two burner, so this isn't highly expensive. So far, we're having issues with the force of the flame 'sucking' the fire off the thermocouple.

 

Alice

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Chris D    0

We got a new floor band from Olympic, a couple dozen K-23 bricks from Laguna Clay, then swung by Aardvark for some supplies, including a bag of Sairbond heat-set mortar. This is the stuff that was universally recommended for putting the kiln floor together. Now that it's time to actually assemble, cut, and drill the floor, I'll be damned if I can find the first scrap of information online about how to use this Sairbond! Ha!

 

We're going to build the kiln floor on a well-braced 4'X4' piece of extruded steel so it doesn't have to be moved between assembly and heat-setting (plan to just slide the burners under it and heat the whole thing at once, and evenly). It seems before we start into this, we should know:

 

 

  • How do you mix the Sairbond?
  • What prep work needs to be done on the bricks before mortaring? Do they need to be soaked in water so they don't draw moisture from the mortar?
  • What temperature do you need to get the mortar to to make it set?
  • Does the mortar have any "green" strength at all?

 

 

I'm amazed at the dearth of information on the internet about this. Even the mortar manufacturer's website doesn't have anything more than the MSDS for Sairbond. Great.

 

Anyone have any experience using this stuff or general guidance to offer? I have some pretty good guesses about what we should do, but would welcome any advice from someone who's been there.

 

I'll post some photos if we have any success!

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Mark C.    1,798

We got a new floor band from Olympic, a couple dozen K-23 bricks from Laguna Clay, then swung by Aardvark for some supplies, including a bag of Sairbond heat-set mortar. This is the stuff that was universally recommended for putting the kiln floor together. Now that it's time to actually assemble, cut, and drill the floor, I'll be damned if I can find the first scrap of information online about how to use this Sairbond! Ha!

 

We're going to build the kiln floor on a well-braced 4'X4' piece of extruded steel so it doesn't have to be moved between assembly and heat-setting (plan to just slide the burners under it and heat the whole thing at once, and evenly). It seems before we start into this, we should know:

 

 

  • How do you mix the Sairbond?
  • What prep work needs to be done on the bricks before mortaring? Do they need to be soaked in water so they don't draw moisture from the mortar?
  • What temperature do you need to get the mortar to to make it set?
  • Does the mortar have any "green" strength at all?

 

 

I'm amazed at the dearth of information on the internet about this. Even the mortar manufacturer's website doesn't have anything more than the MSDS for Sairbond. Great.

 

Anyone have any experience using this stuff or general guidance to offer? I have some pretty good guesses about what we should do, but would welcome any advice from someone who's been there.

 

I'll post some photos if we have any success!

 

 

Its been 30 years since I have used that brand of mortar .

The super 32 stuff I use now is ready to go from the bucket and air sets it off-thats what I recall on sairset as well?

As far as green strength some but its heat that makes it go off hard

I would brush or vacuum the bricks and spray them with a water sprayer 1st before applying the mortar.do not soak them in water

What to heat them to is per manufacture instructions -call ardvark

If it was me Id dry fit the whole mess 1st then clean all the bricks and spray the edges and add mortar (which will take up more space) then band.

let dry then build the kiln on the floor and fire the whole kiln load.

I have been putting steel under my electrics for years and I would do this on this trash can gas kiln as well for support on floor. !/4 inch plate.

Mark

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Chris D    0

Its been 30 years since I have used that brand of mortar .

The super 32 stuff I use now is ready to go from the bucket and air sets it off-thats what I recall on sairset as well?

As far as green strength some but its heat that makes it go off hard

I would brush or vacuum the bricks and spray them with a water sprayer 1st before applying the mortar.do not soak them in water

What to heat them to is per manufacture instructions -call ardvark

If it was me Id dry fit the whole mess 1st then clean all the bricks and spray the edges and add mortar (which will take up more space) then band.

let dry then build the kiln on the floor and fire the whole kiln load.

I have been putting steel under my electrics for years and I would do this on this trash can gas kiln as well for support on floor. !/4 inch plate.

Mark

 

 

Thanks Mark. All good advice (especially calling Aardvark. Not sure why I didn't think of that!).

 

We planned to dry-fit everything then mortar it together, cook the heck out of it, then cut the floor to shape. Thinking about it again, it'd probably be better to cut the bricks before mortaring. That way the band can hold the whole mess together while it cooks.

 

Spraying the blocks with a bit of water sounds better than soaking, too.

 

Chris

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Mark C.    1,798

You most diffidently want the squeeze of the bands before firing and while the mortar sets off.

also consider a 1/4 plate steel support floor with larger burner holes cut into it for support.even 1/4 diamond aluminum plate works, it must be flat . I have one under my electric. Both in steel on one kiln and aluminum on another.

Most stands really do not support the wall loads as they cantilever the floor out and the wall sits in that-really a poor design -but thats just my 2 cents and electric folks never seem to fully grasp this. There has been lots of floor cracking talk and this cures all of it.Yes it is an extra expense and step.

Mark

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Chris D    0

You most diffidently want the squeeze of the bands before firing and while the mortar sets off.

also consider a 1/4 plate steel support floor with larger burner holes cut into it for support.even 1/4 diamond aluminum plate works, it must be flat . I have one under my electric. Both in steel on one kiln and aluminum on another.

Most stands really do not support the wall loads as they cantilever the floor out and the wall sits in that-really a poor design -but thats just my 2 cents and electric folks never seem to fully grasp this. There has been lots of floor cracking talk and this cures all of it.Yes it is an extra expense and step.

Mark

 

 

Well...We did some more research in the meantime, and learned that for Sairbond to actually "set" it needs to be fired to cone 10! At least that's what the folks at Aardvark told us. Of course, they told us we should have just bought a floor from Olympic, but whatever. The guy at Aardvark told us we should have gotten Sairset, which is a pre-mixed mortar that air-sets. I spoke with people at Harbison Walker, too, and they sent me some information about using both products (pretty useless) and told me that Sairset has good strength after air-setting, but really gets it's full strength after it reaches a temperature around 850 degrees F. That sounds a lot easier to achieve. Without another kiln that can accommodate this 34-inch diameter floor, there's little chance of us heating it to cone 10...ever, probably! Ha!

 

We pre-cut two boxes of K-23 IFB for the floor, went back to Aardvark and got a few pints of Sairset and are ready to put the pre-cut pieces of the floor together:

 

8129345315_424992c3c6_b_d.jpg

 

On my way out to the studio to do that now... Will report back on success/failure.

 

I'm with you on the whole "added support" for the floor. The Olympic-supplied metal stand is a flimsy, sad affair that I really can't believe was sold with the kiln originally, but looking around, I see that I probably was. I'm amazed at how incredibly soft the K-23 bricks are. That this floor could support a loaded kiln is an amazing concept to me. I can crush these things with my hands! Short-term, I plan to bolster the floor with some spare square-steel tubing I have laying around. Long term, I plan to fab up a support structure similar to what Peter at Summit Kilns uses for his GV-27 burner system. That guy knows what he's doing!

 

Chris

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Marcia Selsor    1,301

I can't tell you much about the Torch bearer but using a home gas line, you'll need to be as close to the meter as you can be.

Marcia

 

 

Thanks Marcia,

 

Do you say that because home gas line pressure is generally low? The people at Olympic told us that you don't need a pressure regulator on a home gas line since it's already generally at the correct pressure for the kiln. Perhaps it's a volume issue?

 

I moved my meter back near my kiln since I could not put the kiln near the meter.

Marcia

 

 

 

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Chris D    0

 

I moved my meter back near my kiln since I could not put the kiln near the meter.

Marcia

 

 

 

 

 

Interesting! We have a gauge that measures inches of water to put in between the valve and the burners so we can keep track of the gas going to the burners. Hopefully this will help us figure out too if we have inadequate gas at the kiln. There's quite a bit of 3/4 inch line between the kiln and the street, so we'll have to see.

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Chris D    0

Got everything mortared up, and strapped the band on it:

 

8131829633_41b0cff723_b_d.jpg

 

Scraped off most of the excess mortar and then plan to sand off the rest once the mortar has had time to set/dry. At it's thickest, the mortar is maybe 1/16 inch, and I buttered both sides of each joint before mating the brick surfaces. Everything seemed to stick pretty well together, though with such thin joints, it was a challenge to firmly assemble new bricks to the already-built floor. Had to be careful and forceful at the same time. A few notes:

 

 

  • I wouldn't try this if I had no previous experience with other sorts of mortar. This is sort of a tricky application, and wouldn't be great for a true beginner.
  • you need to work pretty fast. The mortar sets quickly with contact with air, but takes a good while to set in the center of the joint (we tested this overnight on some scrap)
  • A 28-inch "round" kiln's floor actually has a 34-inch diameter floor. 2 boxes of a dozen K-23 bricks are *just* enough, but you're using scraps from bricks you cut to complete it, so you have to plan very well, or buy a couple of extra bricks.
  • 2 pints of Sairset mortar are *just* enough. We had less just a few tablespoons of mortar left. YMMV.
  • Don't count on the band to "pull everything together" when you're done. The band can be tightened pretty tight, but doesn't come anywhere near tight enough to squeeze the bricks together any tighter than they were when you put them together initially.

 

Really hoping this works. If it does, we'll have saved some good coin. The floor from Olympic was a couple hundred bucks, and was going to be more than $100 to ship because of its weight, size, and fragility. All told, the bricks cost $66, the mortar cost $7, and the band from Olympic was $30. $100 for a new floor. Not pretending it'll be as good as one put together by pros, but it should be "good enough!"

 

If it doesn't work, it was only a $100 mistake. I've certainly made worse mistakes! Ha!

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Ron B    0

I moved my meter back near my kiln since I could not put the kiln near the meter.

Marcia

 

 

 

 

 

Interesting! We have a gauge that measures inches of water to put in between the valve and the burners so we can keep track of the gas going to the burners. Hopefully this will help us figure out too if we have inadequate gas at the kiln. There's quite a bit of 3/4 inch line between the kiln and the street, so we'll have to see.

 

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Ron B    0

Make sure that you have a gas meter, and pressure regulator, that is able to provide you with the amount of gas that the kiln needs. Take a look at the regulator and it should give you the orifice size and the spring color. If you have that information, and the manufacture of the regulator, you can call a company that deals with that brand and find out how many BTUs the regulator will provide. You will also need to know what BTUs the burners can provide. If the pressure regulator in its present configuration will not provide you with enough gas the orifices and springs can be changed to what you need to make things work.

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Chris D    0

Well, the floor (so far) was a success. We reamed out the burner orifaces to #28 for gas (turns out they were propane orifaces) and set everything up and gave it a whirl. Worked pretty well! I think we have the fuel/air mix off a good bit, but we were still able to get the kiln to 1,900 degrees in just a couple of hours. Some photos:

 

The floor, in place, with burner ports cut:

 

8155621487_13728f7789_z_d.jpg

 

 

Detail of burner head and port:

 

8155592907_bb4fd6e69d_z_d.jpg

 

 

Low flames on the first firing:

 

8157868835_9686f43153_z_d.jpg

 

 

At full burn, just before we shut it down:

 

8157910648_229c65377b_z_d.jpg

 

 

After cutting off the gas:

 

8157918654_1747cb6275_z_d.jpg

 

 

The goal is to get the thing to cone 10. We have a long way to go, and I can tell that the 4-500 degrees above 1,900 we need to get are going to be hard-earned. But I think we can do it. There's certainly no shortage of gas...we got it to 1,900 degrees with the valve barely cracked. Soot around the lid in places where there were heat/flame leaks tells me that the mix was probably starved of air, but that's just a guess.

 

Very excited at the success so far, but not sure if we need to increase primary air (with the burner venturi shutters), secondary air (with larger burner ports...we cut them pretty small) or both! Time and experimentation will tell.

 

Looks like the next project for this thing will be to rebuild the lid. After the first firing (probably in a decade) the part of the lid near the hinge was crumbly and falling apart. I can see the whole thing crashing down through the kiln and crushing the floor, so maybe we should replace it sooner rather than later. I really dislike the hinge system that olympic devised for this kiln. Seems built to fail. The lid is pretty heavy, and all that supports it when it's open are a couple of brackets that are attached to thin sheet metal that gets all of it's structural integrity from the K-23 firebrick that it's squeezing. Bad design. Was thinking that it might be good to weld up a frame to go around the kiln and create a "bridge" over the lid with a pulley system so the lid can be lifted with a little winch, kind of like how some raku kilns are designed, but only lifting the lid. Anyone ever see something like that?

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