PID forge, in an unusual manner, need help

E

El Mucho Hombre

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Apr 16, 2013
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Please read it all and understand what I'm asking before responding.

I'm in the planning phase of building a new forge. I want to use it to heat treat, and for general forging. It's going to be a double ribbon burner with Venturi burners. All of that is figured out and taken care of.

What I need help with, from someone way more technologically gifted than myself, is how to wire a PID into 2 separate solenoid valves, to make the burners fire one at a time, independent of each other. So, both would fire at the same time when ramping up to programmed heat, or when just left wide open, but when at programmed heat, both would either reduce to minimal flame, or cut off, then fire separately. Left, off, right, off, ad nauseum.

There's a method to this madness, but I need help with the wiring and programming. My skills and experience are nearly entirely within the realm of fabrication.

From what I've gathered, not counting the burners and all that good stuff, I need a good PID, 2 thermocouples, 2 solenoid valves, a solid state rectifier, and 2 igniters.

Wiring it to work regularly isn't really complicated, but that's also not what I want to do, neither is using a blower. I want to do Venturi, and I want the pair of ribbon burners to fire one at a time.

Any thoughts or help?
 
You probably need to do a bit more research: the "2 thermocouples" and "Solid State Rectifier" are not things that I'd be looking to incorporate and I'm not sure where the thinking has originated.

I'd be using a fairly basic PID with 2 relay outputs: one for control and one for an alarm.

I'd use AC solenoid valves and an AC Alternating Relay fed by the control output to deal with the alternating of the burners. It's worth Googling for these: I am in the UK and don't know what is readily available to you.

I'd use the Alarm relay, probably configured as a low deviation alarm, to switch a (minimum) 2-pole bypass relay that would bypass the alternating relay and feed both solenoid valves together when the temperature was more than, say, 50 degrees below setpoint.

You don't actually need a particularly "good" (or at least not a particularly expensive) PID, but you do need it to have a good manual and a decent autotune. Good telephone support is very desirable if you are planning to do your stuff during normal working hours. Less so if you are limited to weekends.

Either way, download the manual for whatever you are considering before you buy and save the link. Ensure you understand it. If you run into problems down the line and have to ask for help on a forum, posting the link to the manual will increase your chances of getting that help by several orders of magnitude.

Never, ever buy a PID controller that does not have a readily-accessible online manual.

I would also advise against buying one where you are required to provide login details to access the online manual, though that's mainly because I won't do it.
 
What your wanting to do could be done but it would require some tricky business. A pid is a simple device, it reads the temp and if it needs heat it outputs a "on" signal to the SSR. When the temp reaches the set temp it cuts off the "on" signal. You could cobble togather a timed relay that took the "on" signal from the pid and flip floped it back and forth between the 2 solenoids. The big problem I had with my pid controlled forge especaly during heat treating is the "poooooof" when the gas ignites. This can be solved by running a blown forge and cutting the gas and air down to a minimum when the pid is in the off position. But this has to be independently adjusted to make sure the temp during idle does not over shoot your set temp. I got the best results adjusting the idle temp to just under my set temp. This reduced the cycle to a minimum and evened out the temp much better then it constantly cycling. If your heart is set on a ventury burner you might see some issues with the low idle cycle. I have run my forges off a pid and a ventury burner but not to the extent you are wanting to. But honestly a blown burner is much easier to tune and get to run how you want.
 
On my venturi burner forge for HT the lowest I can get it to run stable is 1500. I need to play with the jetting or something, or I make convert it to a blown forge. You may look into using an arduino vs a typical PID. You could probably get it programmed to do what you want instead of adding outside elements to get the results you're after. I know there is already code available for using it as a PID, getting involved in an adruino forum and you could probably get someone to help you modify the code to handle the flip flopping of burners. It would probably be very simple code to modify to flip flop 2 out puts of a programmable device.

Edit: there are tons of posts on here of people who have used an arduino. use the custom search in the stickies.
 
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I wasn't aware that a venturi could run a ribbon burner, The air and gas are mixed and flow through the burner, where they ignite.

The setup used by others I have seen is a manifold fed by a blower.The gas is injected before the expansion up to the ribbon plate. The burner is controlled and balanced by the a gas needle valve ( or PID control), and a gate valve on the blower.

If the forge dome is built right, I can't see any reason for two ribbon burners ... nles it is a HUGE forge.

Once the forge is up to heat, it does not need an igniter to re-light it. It is a nice feature to add for the initial ignition, but not necessary. A simple Peizo lighter from a BBQ is fine.

The PID can control as many solenoids as you wish, but they will all come on and off at the same time without building a computer controller to switch them. The simplest way to control multiple burners is to have multiple gas valves where you can shut them off as desired. That way you can run one burner for HT and two or three for forging of doing damascus.
I highly recommend using my two-stage burner control system. It is in the stickys. It cycles the burner form a pre-set high to a pre-set low and never shuts off. This eliminates the swing in temps in the forge, and the WHOOF as the gas re-ignites that you will get with single stane PID control..

You only need one TC to go to the PID. IF you have dual PIDs, then each would need its own TC. Best placement for the TC in a dome forge is laying on the floor next to the blade.

Other than the shape and the ribbon burner, building a dome forge is pretty much the same as building a regular forge. The PID control is identical.
 
Thanks for the detailed replies folks, I'm reading and re reading them and trying to absorb the information.

I am not opposed to a blown burner, I just have no firsthand experience with them. My Venturi setup on my basic forge runs well at 1psi given there aren't any hurricane force winds, but if a blown setup is going to make it easier than that is the direction I will go.

I had planned on setting both burners up with igniters as well. I'm doing 2 burners mainly because it is a large forge, but secondly because it seems like fun and I'm retired with nothing else other than fly fishing to occupy my time. I am making it large enough to do bearded axes and power hammer tooling, since I am getting a 100lb strap hammer in a few months.

I will look into the arduino idea, I hadn't heard of it before so I will see what they're all about.

Thanks folks! Any more such replies are absolutely welcome, learning and fabricating are about the only things I'm good at.
 
My standard explanation is this:

A venturi burner uses the velocity of the gas stream to pull the oxygen (air) into the burner tube ( Venturi principle). The velocity is gained by pushing the gas through a small orifice ( usually .030"). The positioning, velocity, and quantity of the gas in the stream has to be fairly exact or the burner will not run right. This requires a pressure of 5 to 30 PSI. (I have never seen a venturi that would run on 1PSI). If the pressure falls too low, it can't draw in oxygen and the flame sputters out, or back-flashes into the mixing area. Venturi burners rarely are small enough to run a forge below 1700-1800F. A few good ones can be dialed down to the brink of back-flame and hold at the high side of HT temps. While you can run a venturi burner on a PID control, it has problems keeping the burner running at lower temps. They have a sweet spot where they run most efficiently. They are great for forging, but not as good on the high or low end. They have to be built with smaller or larger orifices to run at lower or higher temps.

A blown burner delivers the oxygen to the burner from a blower, and the gas from an open input port. Both are controlled by a valve. A simple gate valve on the output manifold from the blower, or a shutter on the blower air intake will regulate the volume of the air flow quite easily. The blower should have enough static pressure to assure flow, but that can be a large range with no appreciable change in performance for our purposes. The gas is controlled by a needle valve, and usually delivered into the air manifold through a Tee. The standard gas input is a 1/4" pipe nipple, as there is no orifice used. Since both the air supply and the gas supply are independent of each other, all you need to do to control the burner is control how much air and how much gas you deliver. Gas pressure is usually between one and three PSI. They can be set to a very low temp, and can hold that temp with good reliability. PID control can be very accurate. Because the oxygen/fuel mix is completely controllable, they are efficient over the full range, and generally can be pushed to higher temps than a venturi burner.

To eliminate the WHOOFF! that happens with straight PID control on either type burner, I invented a two-stage burner control that keeps extremely close temperature regulation. It runs best on a blown burner, but will control a venturi. All the plans and info are free to anyone and can be found in the stickys and in many threads about PID control. I am fairly sure I didn't invent something new, but haven't found this type control use applied to a knifemaking type forge anywhere else. Used along with a thick walled muffle pipe in a gas forge you can give HT control to equal an electric HT oven.
 
El Mucho Hombre said:
Stacy,

Here is some associated reading regarding Venturi/naturally aspirated ribbon burners. It's been a thing for a long time.

https://www.iforgeiron.com/topic/48001-naturally-aspirated-ribbon-burner-photo-heavy/

http://www.joppaglass.com/new_ideas/forge/sm_forge_const.html

They are finicky with regards to port number and size, but it is possible and has been done.

I also acquired a good handful of boiler blowers, and some much larger blowers as well. 5 smaller ones and 4 large ones.
Click to expand...
May I suggest going with a blower system instead of a venturi? I have used Frosty's forge (the iforgeiron link) and it runs beautifully for the first few hours, but after a while, the ribbon gets hot enough to combust the gas on the wrong side causing it to backfire. It gets your attention rather quickly, but is relatively harmless, however you have to shut down the forge to cool to remedy it. A blower should eliminate the entire problem by cooling the intake side of the ribbon block better than the venturi will. I'm also pretty sure that a blower would use less gas than a venturi. One of your boiler blowers should work great (I use one on my waste oil forge) just realize that those squirrel cage blowers don't like airflow restriction much.
 
I'm doing a blown setup, I decided on that awhile ago. I just felt that I should share the info on NARB's that I dug up in case someone is reading this thread and gets curious. While possible, I don't believe it to be ideal.

The only part of this entire build that I'm struggling with is wiring the burners to fire one at a time, left then right. The rest of it is all very basic.
 
Apologies if that came of as short, had a family emergency and hit the post button on accident.

To expound further, the burner construction, solenoid, igniter, etc is all pretty basic fabrication, where I'm hung up is the wiring. A PID is also pretty basic stuff, but I'm real hung up on the arduino concept to make it work how I want it to.

I'm building 2 separate forges, a long and narrow single burner one that's already figured out and much simpler. The double burner one is for doing stuff like axes, hammers, power hammer tooling, etc, and for heat treating those parts as well. That's the one that's giving me fits. I could easily make them fire at the same time, but I don't like the fluid dynamics that'll produce with 2 burners essentially colliding. My only other thought would be positioning them one top and one bottom, on tangent to fire simultaneously and not fight each other. Keeping a very large space evenly heated is my main concern.

Thanks for the replies! Again, apologies if I came off as short. Not my intent.
 
Maybe I'm missing something in your build description, but having two or three burners parallel in a forge runs just fine. Cycling them seems like a nightmare with big problems, to me.

Angle them all the same ( close to the chamber tangent and 15-20 degrees off perpendicular to the long axis) and space them about 6-8" apart. If you are worried about the additive heat value as the hot gases flow down the chamber, adjust the flames on the burners to be sequentially lower to compensate for this ( 1 2 3). It wouldn't hurt to install three TCs as read-only aids for balancing the chamber. If there is a problem keeping the chamber evenly heated., then use the three TCs to run three PIDs and control each burner independently, but I can't see the need for this in a normal forge.

I have found heavier refractory does more good than most fancy burner control plans. It takes a while to get soaked, but a 1" cast liner ( Kast-o-lite 30) with 2" of Ins-wool around it will make a heck of a HT forge. The more the thermal mass, the more even the heating of the chamber.

Ardino boards came along well after I left the electronic world, so I am not really familiar with them. I know the DIY guys like them. But, a simple PID is all you need for running a forge or oven. You don't need proportional control or any fancy stuff. My two-stage burner design does that just as well. A PID, a few switches and lights, a solenoid ( you only need one), and a by-pass line will run 1, 2, 3, 4, or 5 burners simultaneously.

A few years ago, Charles at Atlas put me onto something I never thought of in the past .... angling the burners from the front toward the back. In a single burner, place it at the front. On multiple, place them parallel and aiming rearward. This exhausts that hot gas away from you. Up to then I think everyone placed them forward. Many still do, but it sure is nice with the dragon's breath not in your face.
 
Stacy I quickly figured out on my first forge build that had the angled burner facing forward that if I just turn the forge around It is much nicer to use. It has the same size opening for both front and back so it was easy to just turn the forge around.
 
Stacy,

All of the burners are not inline on one side, there are rows of ribbon burners on each side of the forge opening.

Problematic or not, when I get an idea in my head, I'm gonna figure out a way to do it or hurt myself trying.
 
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