I need blown burner pro help please.

Overmountain

Overmountain

Joined
May 2, 2013
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Ok, I have read and read, even some of Stacy's stuff on hypefree. I am building a blown/ribbon burner forge... I am fairly good with venturi setups, they are basically one barrel of a carburator... Blown is giving me fits.
I am wanting PID control. I understand relays and solonoid valves and how they work... My questions start with proportioning of the two. I wound up looking at the ASM HTS conference notes of all things looking at their proportioning controls. Are most of you guys running just on/off within the values of the PID control or using any kind of progressive control using proportioning valves? I was reading about the use of bleed screws to change up the air/fuel ratio with these sorts of systems and whatnot but that all seems way way way overly complicated.
Should I (or rather do you and does this work) just use blower inlet restriction and needle valve to manually control the mix, and just have the PID turn it on/off?
 
I run the gas at low pressure and use a 1/4 inch ball valve, the blower has a flapper over the intake that I can adjust air volume with on most of them, my big welding forge uses an old Kirby vac for a blower and I use a variac to control the RPMs of the blower

-Page
 
I get the impression that the OP wants to maintain the air/fuel ratio (and thereby the flame temperature) but have high-fire/low-fire controlled by a PID controller, so needs something more complicated than a set-and-forget valve setup.

I should point out that I'm not even a decent smith, nor am I a burner expert, though I do mess with gas burners a little in my day job. Caveat given, my initial thoughts are:

I really would not want to run ribbon burners on a cyclic on/off control system.

The simplest method would seem to be to hi/low the air supply and use a proportional regulator to match the gas pressure to the air pressure:

https://www.dungs.com/fileadmin/media/Downloads/DBs_BMAs/219570.pdf?1337782532

Page 6 of the link gives the general idea.

There are lots of ways to do it. Easiest/cheapest is probably to switch fan speeds in a single-phase fan controller. This might give a slow enough pressure change that the A:F ratio can keep up with the transitions. Using a 3-phase fan and VFD would probably be better, but more spendy.

Another way would be with a solenoid valve on the air feed: plenty of options, but it looks like a significant amount of faffing about, whichever way you do it.

I'd be interested to know what your proposed setup will look like and why you want to PID control a blown burner. I'm a geek who enjoys doing stuff like that and even I would regard it as more trouble than it's worth under almost any circumstances I can think of.

I'd be more inclined to use a short-choke atmospheric injector with a ribbon burner; that way the mixture ratio is set on the injector and the high/low can be done with a solenoid valve in the gas feed. It seems a lot simpler and I'd be prepared to bet that a commercial injector would be cheaper than a proportional regulator. I use Amal LV injectors occasionally, but have not played with ribbon burners and SC injectors since about 1991, so it's all a bit hazy now.

http://amalcarb.co.uk/downloadfiles/amal/amal_gas_injectors.pdf

I'm pretty sure there will be something very similar made in the US, but don't know any names.
 
The plans in the Sticky's are for my two-stage PID controlled Blown Burner control. If you use a controllable motor, you can control all aspects of the air/gas mix. The two-stage PID control switches the burner from a pre-set HI to a pre-set LOW. This is far better than switching from full blast to no flame. The 2SP control can give you +/- 1-2°F.

Quite a few of the folks have built this system and it works very well. Fred Rowe has made several, IIRC.

For a ribbon burner, you need the forge built accordingly. Eric Fleming and Salem have built them well.
http://www.bladeforums.com/forums/showthread.php/934512-Table-Forge-with-Ribbon-Burner
Somewhere there are photos in a tutorial on how to cast the burners. I'll look for them later.

You might want to check iforgeiron for some build tutorials, too.
 
Thanks guys. Yeah, I may have been a bit fuzzy. I wound up looking at the HTS stuff because I wanted an adjustable burner that could run at different levels and didn't know if it was a common thing, or even necessary. If everyone here running PID control is just using high/low instead of a progressive setup, I will do that. The HTS stuff made it sound like to be efficient I HAD TO have this setup using a proportional set of valves that are driven simultaneously and the air/fuel mix controlled throughout that curve.
I haven't seen anything like that, and as far as I know high/low like Stacy is mentioining is plent of control. I don't need the amount of control they are exploring. If I can find it again I will post a link. It would be cool to do but sounds like it is over my head...
Edit:
Here's the link. Page 71-74ish discusses burner efficiency and progressive setups. http://books.google.com/books?id=io...q=burner+proportioning+valve&output=html_text
 
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You can make the setup Stacy is speaking of, as simple or as complicated as practical. I have rheostat's connected, in line, to the fan on both the high and low sides. Theres a needle valve inline for the high side gas and one on the [idle] low side as well. The solenoid operated by the pid operates the high side gas [injection].
I suggest making your on/off gas flow set up to operate only when the fan is on. I have needle valves in the gas feed lines where they enter each burner, this is really helpful when tuning the forge.
I built one of the 3 inch circular ribbon burners for my welding forge; I'm getting ready to take it out and go with another three burner system. They take a long time to heat up and I found them to be very picky when it came to tuning.
My 12 inch by 24 inch blown forge will hold set temperature in the +/- 3degree range. These builds are really worthwhile. Being able to change working temps at the push of a button is wonderful.

minihammerin+020.jpg
 
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Fully variable control of a gas burner and blower would be a complex build. It would require a variably controllable gas valve, which is very expensive, not to mention the electronics to control it. Forges don't need that degree of control, anyway.

For a good while, everyone did one of two things.
They used the PID as a read-only device to see what the temp was, and adjusted a needle valve manually to get the forge where they wanted. This worked, OK, but had to be constantly adjusted.
The second choice was PID control of a solenoid used to turn the gas on and off. The main drawback of this is the flame can go "woooof" when the gas turns back on again, and the blower is still running when the gas is off. The other drawback is that the forge is either heating up at full throttle, or cooling off....and the PID is trying to keep it somewhere in the middle.

The 2-Stage burner system makes that much more regulated, switching between a flame that runs 100F above the target to one that runs 100F below the target. Obviously, this gives a much smoother control, with no re-ignition. It also regulates the blower to match the gas, thus maintaining the forge atmosphere.
It is quite affordable to build from readily available parts, and with the "Learning Ability" of the PID, is as good as variable control. Each time the PID turns on or off, it "learns" how long it took to heat up and cool down. It learns to anticipate the rise/fall rate and will dial in on just enough HI time to maintain an exact temperature.
 
Thank you both. Exactly the answer I was looking for. I was struggling with the picture of the burner either being on full bore or off... Not ideal in my mind... That led to these duty cycle adjusted units which was seemingly overkill. I will do what you and Fred are describing and have a set low side (idle) and let the PID control the high side. With both set with needle valves on the gas side for control I will be fine atmospherically speaking.
The ribbon burner I am building uses a round plenum that feeds a rectangular burner face. I don't know if this is different than what you are describing Fred but if it is gonna be inefficient I don't want it... I was thinking ribbon would be very efficient based on the design I was following (sort of) it uses a plenum with a baffle for mixing, then a large rectangular burner face...
 
Its very apparent how important this is when you forge for an hour. When you pull a billet from the forge and work it and then place it back in the forge, the forge moves to high input gas/air in order to compensate for the cold steel. Without the pid control the forge takes much longer to get back to working heat. My blown forge will run in the mid 1400's at its low end.
Last but not least; these builds are fun.

Fred
 
The round one I built chipped around the edges and had cracks running into the burner tubes. It does take a while for the thermal mass of the burner to heat up; they don't run efficiently until they are at temperature. I like to be able to adjust the position of the burner in the forge body. There is a sweet spot where the run best. I weld collars to the forge body with set screws to hold the burner in place. If it needs fixed or replaced just turn the set screw and take it out.
Best of luck with your build, enjoy yourself. A note;it took me the better part of 6 months, of and on, to build the Vulcan's Chariot.

Fred
 
Thanks. I think I may go that same route Fred. This one is about a month in, and I figure it will probably take me that long to finish... I did have concern with the large mass that the burner face presents as added mass in the forge, and I was concerned about cracks from unequal size change between the sections of the burner. I also wondered if sticking the cold steel back in the forge would make it react and go full on, and it sounds like it will. I liked the idea of even heat from the ribbon, but it sounds like it is too sweet spot sensitive to run at two levels like Stacy said 100f below and 100f above (low/high.) Is the one with the removeable face the six month build you were talking about Fred? I want to do something similar for easy removal of the floor, but sunshadows drain thing sounds promising too... Of course when its burned up its burned up and will still need to be replaced I reckon.
 
LucyCustomKnives said:
Thanks. I think I may go that same route Fred. This one is about a month in, and I figure it will probably take me that long to finish... I did have concern with the large mass that the burner face presents as added mass in the forge, and I was concerned about cracks from unequal size change between the sections of the burner. I also wondered if sticking the cold steel back in the forge would make it react and go full on, and it sounds like it will. I liked the idea of even heat from the ribbon, but it sounds like it is too sweet spot sensitive to run at two levels like Stacy said 100f below and 100f above (low/high.) Is the one with the removeable face the six month build you were talking about Fred? I want to do something similar for easy removal of the floor, but sunshadows drain thing sounds promising too... Of course when its burned up its burned up and will still need to be replaced I reckon.
Click to expand...

I took all my Borax to the wash room and use hydrocarbon exclusively. It has no effect on the forge lining. It is the one with the removable face. It makes relining easy. Keep us posted on your project.

Fred
 
Sorry to give this dead horse a spur again, but... After reading the posts on the ABS forum I am gonna have to go that route too. I had tried to do laminate stainless/carbon using the WD-40, welded up packet thing. My forge will only get it spottily hot enough now, but with a friend's blown forge could get a good initial weld. Used a layer of nickel in between as well... Need lotsa practice though, start drawing it out and delam city. (Burt tells me its a whole different ballgame than anything else I have piddled with... he ain't kidding...)
I think I will be keeping some kerosene handy from now on though. Anybody use diesel much? I have diesel on hand 24/7 from draining the separator on my F-250 (affectionately named 'Murphy' as it is a dag gum 6.0 powerstroke). Some guys dump this back in their tank minus the last few drops which usually have the water and crap mixed in. I won't cause I don't trust it... So I have a 5 gallon bucket that gets dumped on the annual brush fire... Wondered if its ok to use...

And Fred, aside from inspiring me with the rust knife deal, your forge is one of the coolest steampunky crazy cool looking forges I have seen. I like the manifold and descending octopus (quintopus??) of lines and associated needle valve injectors. Looks more like peeking under the hood of a pre-war 16 cyl Cadillac.... I am gonna have to break out the high temp paint and airbrush!!
 
All kinds of cool info here. Fred very good looking forges.

Wanted to ride on Lucy's thread with a quick question that may be beneficial to the topic. Have you guys tried routing the outlet air line to run in front and above the outlet to the forge so that it acts like a heater for the incoming air? I have read that most of the inefficiency of these forges or a large part anyways comes from the large amount of btu's that it takes to heat up the incoming air. Heating the air prior to the inlet of the forge gives a increase in efficiency from what I understand. Is this a good idea or not.
 
I personally have never seen it routed that way, possibly these guys have. Usually cooler denser oxygen rich air is most beneficial for combustion. Look what happens on a car when the exhaust gas recirculation system (which is for emissions sake to burn unburned hydrocarbons as well as some other small benefits) is removed from the car... instant horsepower gain. I would tend to lean on the air coming from the forge to be oxygen starved from both the combustion already occurring in the forge eating up most of the oxygen and the intense heat causing the air to be very thin. Generally, any time I want to burn something and want it hot, the cooler and denser air I can feed the fire the better.
Now in my wilder days I played with nitrous oxide a bit... that could be cool but not very efficient monitarily speaking :)
 
actually your big issue with preheating your fuel-air charge is burn back, where you already have your fuel and air mixture carbureted, which is why most blown designs introduce the gas 6-18 inches upstream and have at least one turbulence inducing feature (typically a 90 degree elbow) to ensure even mixing, bring the charge up to combustion temperatures in the burner tube and you get forge temperature burning in the combustion tube. You want your incoming charge at below combustion temperatures so your flame front is just in front of your burner tube to keep your combustion in the forge where it belongs not out in the room with you (all a supercharger sneeze is in racing is the flamefront moving back up into the fan, same idea, higher pressures)

-Page
 
I watched a guy a while back, local smith, who had built a blown ribbon forge with air preheat. He'd fabbed a nautilus shaped intake plenum that wrapped around the entire forge shell. It was a nice forge, he said it helped quite a bit and got hotter for sure. I was just talking about that forge last night with a couple other smiths at band practice, they were saying they knew several people who'd done similar rigs to get better efficiency and higher heat. Said the important thing was not to blow up your fan, which must have to do with what Page is discussing above...
 
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