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Joel OF

Heavy scale

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Hello folks, I'm hoping someone might be able to give me some clues as to why my little gas forge is producing heavy stubborn scale on my work. FAR MORE scale than my coke forge.

I got this little forge from a farrier a couple years ago, I don't use it very often so can't remember if it has always produced such a thick stubborn scale. I am embarrassingly naive when it comes to gas forges.

Please find some pics attached. The orange sticker on top of the regulator says "MAX INLENT 20 BAR" and "3.5 PROPANE". The needle on the regulator is hitting 4 bar.

If memory serves me correctly, in an attempt to get it to run as hot as possible a while ago I opened the regulator all the way to let as much propane flow as possible.
There's a brass dial at the end of the hose to increase/choke off the flow. It seems to be opened fully at around 1/4 turn. Turning it beyond 1/4 turn doesn't make the burners run hotter.
The internal lining is worn.

My logic for opening the regulator all the way was to get as rich a propane mix as possible to reduce the amount of air required to make it run hot. Is that logic wrong?

From doing a little reading I understand that gas forges, (when setup correctly), are meant to produce less scale than a coke forge. I'd quite like to get a larger gas forge, but my experiences with the scale produced from this one is putting me off.

Thanks in advance for any advice.

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Regulator pressure is given in positive pressure above atmospheric pressure. Each bar equals one positive atmosphere, which is about 15 PSI, so your regulator is set for about 30 PSI; it should be set no more than 20 PSI maximum. Many burners tend to run rich at low PSI, and lean at high PSI, so I would look into that for a start, because a lean running flame produces too much oxygen for the fuel, a primary reason for scale formation. Next, make sure your flame isn't touching the work, the second most common reason for scale formation.

It would be helpfull to see the forge running, so we can juge the flame it is putting out.

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46 minutes ago, Mikey98118 said:

make sure your flame isn't touching the work, the second most common reason for scale formation.

Thanks Mikey, I think you might have nailed it in one.

I haven't used it for a couple weeks now but from memory the flame does touch the base of the forge, so would definitely be hitting my work.

There is also smaller red writing giving the PSI on the regulator face. The needle is resting at around 60 PSI, which works exactly with your maths that 1 bar = 15 PSI, however I'm not sure how you've reached the figure of 30 PSI.

Many thanks for the prompt helpful info.

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Also note that gauges are easily to get out of calibration and so are only an indication of actual pressure---unless you have them calibrated on a regular schedule which is ridiculously expensive.

I don't see a choke on that burner to adjust the air intake---which is how I regulate the atmosphere in my forge. (and farriers often work with the forge set running full blast to cut down on time for heating.)

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A friend of mine, Metalmangler in fact, has one of those or one so much like it as to make no difference. It doesn't produce scale in the fire unless he has it turned WAY up. Any induction device, linear like these or jet ejectors like a Mikey or a T all induce intake air on a curve the higher the jet psi the more air they induce by comparison and leaner they run.

The induction curve is the source of the . . . I hate to call it a myth but it is what it is, Myth of a lean gas fire burning hotter. What's actually occurring is more fuel and air is being blown into the forge per second so of course it's hotter, there is more fire in the forge.

Anyway, back off your regulator and forget what the gauge says for now. If wont stop running lean you might need a new reg.

They're pretty cheap, $35.00 at Petrolane in Wasilla Ak. with OUR shipping a new gauge is a good idea too, dirt cheap for a functional piece of equipment.

Frosty The Lucky.

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Yes; four bar is 60 PSI. for some reason I invented your saying that the needle was set on 2 bars, and the regulator could go to 4 bars; obviously a lack of coffee there. Or, perhaps I had a brain fart; yes it smells pretty smelly all right.

On the other hand, if your regulator has been running at 60 PSI, I would expect most burner designs to be running quite lean; try backing the pressure off to 1 bar, and see how it runs, and how much shorter it becomes. Me thinks, you're gettinghit with a double whammy. 

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4 hours ago, Mikey98118 said:

On the other hand, if your regulator has been running at 60 PSI, I would expect most burner designs to be running quite lean; try backing the pressure off to 1 bar, and see how it runs, and how much shorter it becomes. Me thinks, you're gettinghit with a double whammy. 

Cheers muchly. I need to do some real research into this. I'm painfully naive when it comes to this stuff and what's obvious and basic to some ppl goes right over my head.

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Don't confuse yourself with research. Remember the reason you made the thing, to use it. At this point just turning the regulator down will tell you what you NEED to know. Once you've determined a cause is when learning the hows and whys of comes into play. What Mike and I believe to be the problem may not be the case in this instance but there's no way to tell if you don't do the simple test.

There's nothing wrong or naive about not seeing what other folk THINK they see. Some of us have been messing with these thing for decades some experimenting and some lucked into literature about them. Good thing they're talkative folk eh? :)

Frosty The Lucky.

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I heated up some bits of 1/2" bar at various reg settings & took pics which I'll upload when I get home.

What sort of colour would you expect a gas forge like mine to get bit of 1/2" bar up to after 4 mins heat time at sensible reg settings?

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Another thing I think worth mentioning is gas forges do get buildup of waxy by products and dirt in their hoses and fittings from time to time which can mess up fuel flow.

Aside from that using gas your work will scale up more anyway regardless. I've always wondered if coal burned cleaner or if it just knocked a lot of scale off by rubbing against to coal when pulled in and out?

George

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2 minutes ago, Joel OF said:

I heated up some bits of 1/2" bar at various reg settings & took pics which I'll upload when I get home.

What sort of colour would you expect a gas forge like mine to get bit of 1/2" bar up to after 4 mins heat time at sensible reg settings?

Is that 4 minutes from start up? Some forges take a while to get going - I had the floor of mine lined with insulating fire brick for a while and it got hot really quickly but the brick breaks down too easily. It now has a kiln tile which is more robust but not insulating so can be slow to get going.

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The Fine Arts Metals classes at a local college finally built a forge; after several years of my dragging all my stuff up there to teach an intro to smithing class. (I still do as I like to have my forge and a max of 2 students per anvil, my tools etc. I did sell the instructor a 5" heavy duty Postvise that is bolted to a support beam under the covered area we forge at and sees heavy (ab)use.)

Anyway the next time I went up for a class, they people who had "passed" the intro class and were supposed to be working on their own projects at the College's forge were asking me to use mine. I asked why and they said their forge had excessive dragon's breath. I asked about their regulator setting and they showed where there was a permanent marker line drawn from the setting dial to the body to mark the "correct" setting.  So I asked them to turn it on and light it and WHOOOM we had a jet of fire coming several feet out of the forge.  So I went over and turned the dial down 3 complete turns till the lines again were lined up and the forge was running like it should.   The moral of the story is that More is not always Better. Some engineering student thought they could just increase the propane pressure and get better results not knowing what kind of results they should be getting.

I am not a propane burner savant; I don't mess with plans and orifices and think I know more than the designer does. If I build one I pick a known good plan and follow it exactly. I do know when one is working appropriately in a forge and when it's time to "seek technical assistance" (my favorite phrase as that was me when I was doing international field support for Lucent Bell Labs). I don't feel I should tie up the time of experts to troubleshoot something I have come up with on my own---if I knew enough to do my own design I should know enough to troubleshoot it!

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As the "savant" they are both describing, I can only agree with Thomas and Frosty; they are saying "keep your eye on the ball." That is always golden advice, at any age, and for any goal.

Savant was a term popular in the sixties; today we are called geeks. I like that better. Eek, eek, I'm a geek!

3 hours ago, George Geist said:

I've always wondered if coal burned cleaner or if it just knocked a lot of scale off by rubbing against to coal when pulled in and out?

I believe it could be described as a carburizing flame, in the same sense that an acetylene flame (even a 'nuetral' one) is carburzing; that is, it produces excess carbon, along with carbon by products into the immediate environment of the work. Carbon fumes, carbon dioxide, and carbon monoxide. Carbon fumes and carbon monoxide around the area of the work, should both do a pretty fair job of soaking up loose oxygen faster than it can cause much oxydation in the heated steel. And the coal/charcoal the work is surrounded by would keep this local "atmosphere" close, all of the time the steel is heating. That's my take on it, but I could be wrong.

Let the debate begin; its the geeky thing to do :)

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There lays a BIG difference between acetylene C2H2 and Propane C3H8. It's easy to get a carburizing call it reducing flame with acet but much harder with propane, all that hydrogen makes for a mixture that likes iron better. Iron bonds with oxy more easily than hydrogen.

However you certainly can make a reducing flame with a air propane burner and believe it or not it doesn't produce nearly as much CO as a similar air acet flame will. My first few T burners didn't scale, one would actually reduce scale to iron or steel it ran so rich. 

Excess C2 gas, and CO is how a puddling furnace works. The iron is kept separate from the fire and incoming air by a barrier while the flame and exhaust from the fire is passed over a water bath resulting in excess carbon in the super heated atmosphere. The excess carbon scavenges the oxy from the iron ore leaving iron/steel.

Don't be quoting me about puddling iron I'm accessing my dented memory files.

A lot of old timers believe you can't weld in a gas forge and all gas forges make scale. Neither is correct a poorly built or out of tune anything won't work like it's supposed to. 

The incident with the college forge Thomas refers to sounds like a gun burner (blown). Turning up JUST the gas has to produce a rich flame, the combustion air is mechanically supplied and not coupled to the fuel. It'd be like throwing bucket fulls of coal on your forge and wondering why it smoked.

Of course I geek, I'm pretty nerdy about geekery.

Frosty The Lucky.

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2 hours ago, Mikey98118 said:

I believe it could be described as a carburizing flame, in the same sense that an acetylene flame (even a 'nuetral' one) is carburzing; that is, it produces excess carbon, along with carbon by products into the immediate environment of the work. Carbon fumes, carbon dioxide, and carbon monoxide. Carbon fumes and carbon monoxide around the area of the work, should both do a pretty fair job of soaking up loose oxygen faster than it can cause much oxydation in the heated steel. And the coal/charcoal the work is surrounded by would keep this local "atmosphere" close, all of the time the steel is heating. That's my take on it, but I could be wrong.

Let the debate begin; its the geeky thing to do :)

 

Well yeah, but let's not forget that coal also has carburizing oxidizing and neutral flames. The more oxidizing the less smoke. New fire with green coal smokes a lot till it cokes up. Hard to say if it has a bearing on scale formation because we're always fine tuning and fussing with the fire to keep it burning right. Gas we don't do that. What we got is what we got.

George

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Hi folks, I took some pictures yesterday with the regulator dialed down a bit.

The first picture is of the flame soon after lighting the forge with the regulator down to 1 bar as Mikey suggested. I later turned it up to 2 bar to see the difference. Turning it down from 4 bar as it was originally set made a huge difference to the flame colour and size.

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The second picture is of the forge up to temp and 2 bars of 1/2" heating up.

Gas-forge-2.thumb.jpg.38ea0adce6051659adc3d8d2e9bb990b.jpg

The 3rd pic is of another two 1/2" bars out of the forge when it was set to 2 bar. The max heat they'd reach was only bright orange, on small bar like this I'd hope for yellow.

Gas-forge-3.thumb.jpg.dd5d6d300dfa6d077d83a786aebbb91c.jpg

The 4th pic shows the bars' surface texture after brushing with a proper big butchers block brush at a red head. The two bars on the left are the 1 bar regulator settings heat and the two bars on the right are the 2 bar regulator setting heat. My coke forge doesn't leave a textured surface like this. The scale and surface finish was a little better at 1 bar, though it would only get up to a mid orange. At 2 bar it got a little hotter up to bright orange which is okay-ish, but still doesn't give you much working time.

Gas-forge-4.thumb.jpg.8f6ec5f4dedd85f51668253d0a72184c.jpg

Any thoughts on how I can get it to run hotter without cranking it up so I'm back to the insanely heavy scale situation?

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Yes; actually the lower pressure flame in the first photo where quite how, and boarder line oxydizing, so it is not surprising that they would become very oxydizing at thigher gas pressure. So, you problem is to retain more heat; not produce more. How to do this? To begin with...that there's a forge; not a fireplace. Put a baffle wall in front of that wide open reat distroing wall!!! AFTER

YOU DO THAT, we can dicuss heat reflection coatings, etc.

Lets try that again. Yes; actually the lower pressure flame in the first photo is quite hot, and boarder line oxidizing, so it is not surprising that they would become very oxidizing at higher gas pressures. So, your problem is to retain more heat; not produce more. How to do this? To begin with...that there's a forge; not a fireplace. Put a baffle wall in front of that wide open heat destroing opening!!! AFTER YOU DO THAT, we can discuss heat reflection coatings, etc.

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2 hours ago, Mikey98118 said:

Put a baffle wall in front of that wide open heat destroing opening!!!

A couple of insulating firebricks should be sufficient for testing at least -if you weld an angle rail on to support them they can be slid open/closed as desired.

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If that was my forge I would buy a couple of insulating firebrick and cut them to fit inside that opening and place them on either end of the opening and trim them to leave about 1/3 the length open.  With a set of hot brick tongs I could remove one or both if I needed the wide access and with them in place your forge should get much hotter!

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Both are good and acceptable methods, costing very little effort or money. When you find out first hand, how much good this does, then you can take the time to fine tune your efforts, to avoid possible problems in inherent in any change of physical structures under thermal stress; by then it will be a labor of love, instead of an additional burden.

Again, I must stress that you need less of that flame; not more. In fact, I would not have believed such a burner design could produce those hard flames, if you hadn't shown me! This is what I most love about this group; regular draw dropping surprises.

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54 minutes ago, Mikey98118 said:

Again, I must stress that you need less of that flame; not more. In fact, I would not have believed such a burner design could produce those hard flames, if you hadn't shown me! This is what I most love about this group; regular draw dropping surprises.

The flame being produced is typical of a burner with the mixing tube tapered full length. The current burners are poor cousins by comparison of performance but they're easier to make so that's what we're getting. 

The tapered nozzle is the result of a misunderstanding but it made a simple linear burner functional and it's easy to make so now it's the "norm."

Were that my forge I'd pull the jets and make sure they aren't gummed up. Metalmangler's welds with one burner lit and it doesn't scale in the fire. It runs a little too rich if anything till you really have it cranked up.

Frosty The Lucky.

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Frosty,

This is a little off topic in this thread, but have you considered coating the burners hot face on your NARB with your kiln wash, to extend the perioud you can run it on super low gas pressure? Just a thought...

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Ayup, washed them right after testing before putting them in the forge.  About 1/2" of the block's flame face has a pretty high % zircopax in the refractory. I think these blocks just need enough fuel air flowing to keep them cool.

I've thought of a couple different schemes that might work but they're much harder to cast. Still thinking about how to cast them without spending days at it.

Frosty The Lucky.

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