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billyO

PID controlled forge build

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Posted (edited)

Hello all.  I'm ready to rebuild my forge and am going to make some upgrades this time.  Here's a sketch of my original set-up:

20191231_103241.jpg

 

Here's a schematic of what my current plan is:  

Basic schematic.jpg

 

My initial upgrade idea was to install a NC valve right at the tank regulator connected to the blower wiring so that fuel is shut off when the blower isn't running but decided to go 'whole hog' and add the PID controller system.  I don't intend on using this as a HT forge, I just want to try to improve my efficiency with fuel use.  

 

This will probably be a WIP and I'm sure I'll have questions along the way.  And I'm appreciative of any thoughts/suggestions/input as appropriate.

 

In fact, here's a question:  Does it matter if I wire the NC solenoid in series or parallel with the blower?  

Thanks.

Edited by billyO

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You need a gate valve in the air supply .  You want to be able to adjust the fuel/air mixture just like in an oxy/fuel torch.

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Yes it certainly does matter. If both devices are line voltage, 120 V, they need to be in parallel.  Also the following :

  1. a diverting solenoid valve rated for propane may be expensive and hard to source. Just use another NC 2 way control valve on the high fire side of your gas train.
  2. make sure the quick connect is rated for gas service as well. Standard air quick connects won't work.
  3. not sure why you need 2 thermocouples. In any event use the thickest ones you can get and protect with wells so can be replaced as they break down.  Type K are unreliable at over 2100 Deg F and type R or S are expensive. 
  4. Use proper thermocouple wire.

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4 hours ago, Wayne Coe said:

You need a gate valve in the air supply .  You want to be able to adjust the fuel/air mixture just like in an oxy/fuel torch.

 

Hi Wayne, and thanks.  The air flow control is the dark grey circle on the fan (also shown in the sketch as the circle with the dot on the side) that I can spin around the screw to open or close the air intake on the blower.

 

3 hours ago, Dan Hertzson said:

Yes it certainly does matter. If both devices are line voltage, 120 V, they need to be in parallel.  Also the following :

  1. a diverting solenoid valve rated for propane may be expensive and hard to source. Just use another NC 2 way control valve on the high fire side of your gas train.
  2. make sure the quick connect is rated for gas service as well. Standard air quick connects won't work.
  3. not sure why you need 2 thermocouples. In any event use the thickest ones you can get and protect with wells so can be replaced as they break down.  Type K are unreliable at over 2100 Deg F and type R or S are expensive. 
  4. Use proper thermocouple wire.

'

Thanks Dan.  I think I have an affordable source for the valves and parts.  I'm planning on posting links to the parts that I use.  And yes, I'm going to make sure that all parts are rated for propane and as heavy duty as practical because this will mainly be used for damascus billets which usually start as ~ 1 1/2 - 2"x 4" x 8".  
 

I'm only going to use one thermocouple, just have 2 options for placement.  As currently planned, the bottom one is going to be used to read monitor temps while the forge is getting to the minimum temp, and will buried under the flux catching media.  (As you can see in the next pic, when I made this forge years ago originally, I WAY overbuilt with 2" of refractory, but the nice thing is that it's a great heat sink, so once I'm up to temp, I can put large chunks of steel in and the forge temp doesn't drop much.)  Then once I'm at the minimum temp, I'll move the thermocouple to the upper position that will monitor the max temp of the forge.

 

20200101_085151.jpg

  

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A potentially money saving thought - should I plan the system to have just one NC -way valve such as this one?

https://valvesandinstruments.com/browse-by-brand/asco-valve/solenoid-valves/asco-8320g184-120-60ac-3-way-brass-1-4-in-solenoid-valve-normally-closed-general-service.html

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You need finer control than a baffle will provide.  You would not want to use a baffle to control oxy on an oxy/fuel torch.  With a gate valve ;you can make very specific adjustments.  Just like you need needle valves on the fuel rather than a ball valve.

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14 hours ago, Wayne Coe said:

You need finer control than a baffle will provide. 

Need or want?  (I'm not being snarky, here, Wayne) 

The reason for my question is that I've been running my forge using the baffle as my airflow control for over 10 years now, and it seems to work fine.  

 

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I'm getting ready to order my parts, but still have a couple of thing I'd like help thinking out:

 

I've been told that I could use a 25A SSR but would probably need a heat sink for it, but if I went with a 40A SSR, then I wouldn't need a heat sink.  Any thoughts?

 

Also,  would I be wasting money by having a NC solenoid at the tank regulator and another 3-way NC solenoid at the propane high/low flow junction?  Part of me wants to say the extra redundancy is good...but all I'm doing is shutting off the gas further down the line without it.  WWYD?

Thanks

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Hello all.  I'm not seeing that this community has much interest in this thread, so unless I hear otherwise, I will stop posting updates here and focus my time and efforts elsewhere.

 

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Oh, I'm interested, you've just gone beyond my ability to offer meaningful advice!  I don't know enough about electronics and solenoids and so on, I count on threads like this and the one Joel did on using a PID to control his toaster oven to let me know what's possible.  

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Cool, thanks Alan....I was beginning to think nobody liked me.

 

I'll post the final product with parts list and video of it in operation.  Hopefully sooner than later.

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billyO, I've been watching.  Don't know enough to even keep my PID working right on my lead post for casting, so been quiet here.  I'd like to do the same to my forge.................just not smart enough to figure it out.  So keep posting.........we like ya!!!!! :lol:

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Thanks Chris!  (I was worried because of my failure to have a completed entry to the last KITH...:().

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Yup, ya gotta be real careful...............lot's of serious haters here on the forum. ;):D:P:lol:  Surely don't want to tick any of us off.  No tellin' what might come of it. image.gif

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Forgive me if I have not read this correctly...looking at your colorful diagram I see the need for the green colored NC solenoid valve as a safety decice. You will have to create a switch that will not open that valve after a power outage.  I would put the controlling valve on the line having the lower propane flow to the burner. The larger flow would be just capable of achieving a temperature   almost at the set point . With both gas valves  ( larger needle and the smaller needle/solenoid). open your set point can be reached. The blower stays on and when controlling your only disadvantage is a slightly oxidizing flame for a very short time.. 

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Posted (edited)
1 hour ago, Jan Ysselstein said:

Forgive me if I have not read this correctly...looking at your colorful diagram I see the need for the green colored NC solenoid valve as a safety device. You will have to create a switch that will not open that valve after a power outage.  I would put the controlling valve on the line having the lower propane flow to the burner. The larger flow would be just capable of achieving a temperature   almost at the set point . With both gas valves  ( larger needle and the smaller needle/solenoid). open your set point can be reached. The blower stays on and when controlling your only disadvantage is a slightly oxidizing flame for a very short time.. 

Hi Jan.  No worries.

The green NC solenoid is the safety.  The NC means Normally Closed, which means that it is closed unless there is power keeping it open.

I've also changed my plan slightly, and here's a re-drawn schematic:

Basic schematic2.jpg

 

I plan on having a manual on/off switch connected to the (blue) PID controlled NC solenoid.  With this off, I will be able to fire up the forge and get it to my Min set temp, then switch on the PID which will open the 2nd line and supply more propane to the forge, increasing the temp and then the PID will take over once the Max temp is set.  

 

That's the plan, anyway....  Parts are ordered.  I'll keep you posted.

 

Edited by billyO

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I think what Jan was thinking, and me as well once I figured out it was a normally closed solenoid, is for short power outages, the momentary blips from 1 to 30 seconds.  The NC solenoid will indeed cut the gas during the blip, but when the power comes back on it will open again.  The forge will still be hot enough to ignite it, so you could conceivably get a healthly little "kaboom" that would do no damage to anything but your underwear.  But the big thing would be a longer outage IF you don't turn off the tank valve, and an hour later the power comes back, and the gas comes on, does not ignite, and so on...

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14 minutes ago, Dan Hertzson said:

Typically the green NC solenoid valve is wired to require a manual reset.

 

I was thinking about doing this, too.  Just not sure how yet.

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Posted (edited)

Both of your diagrams have the propane-entering at 90 degrees to the direction of air flow.....if the  gas is coming in parallel and in the same direction as the air flow your set up may keep running if the power goes out .

 

Edited by Jan Ysselstein

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13 hours ago, Dan Hertzson said:

Typically the green NC solenoid valve is wired to require a manual reset.

 

See, that's the sort of thing that's good to know, and I didn't!  Keep it up and this thread may get a pin!

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17 hours ago, billyO said:

I was thinking about doing this, too.  Just not sure how yet.

 

Well you can buy a manual reset valve configured to be initially manually opened then default to the closed position on loss of power.  This may be an expensive option. 

 

Or you can go old school and wire it up with a relay and pushbutton switch.  Been a while since I did one of those, so I'd have to recreate my wiring diagram, but it is pretty straightforward logic if I recall correctly.  You use a NC valve that when energized opens.  Then in addition to the on/off control system switch and fuse (you are going to include those right?), you include a momentary push-button switch that energizes both the relay and and a holding contact.  The NC valve is also powered through one of the relay's NO contacts so that when  the power is on it both holds the relay closed and the valve open, but when the power fails, or at startup, you need to manually push the button.  See the attached image for details (sorry for the image size, new computer at work and don't have image processing software).

Manual restart gas valve.jpg

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2 hours ago, Dan Hertzson said:

Or you can go old school and wire it up with a relay and pushbutton switch.

 

Thanks, Dan.  Yes, having a manual re-set switch Normally Open(?) to energize the safety NC solenoid to start/re-start the forge after power loss was my thought.  

2 hours ago, Dan Hertzson said:

Then in addition to the on/off control system switch and fuse (you are going to include those right?),

 On/off control (what I would call a Master Switch) is planned, and I was going to add either a fuse or circuit breaker, but when I called tech support at Auberins this morning to ask for a recommendation on fuse size to add to my order, she said that (a) because this is running off a standard house circuit with a 15A breaker, (b) because I'm using an SSR rated for 80 amps, and  (c) the PID has it's own internal fuse/circuit breaker, adding a second fuse is unnecessary.  I'm still thinking about adding one anyway.  I'm not sure you can have too many back-ups (unless cost concerns override safety concerns, that is).

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Hello all.  I hope the winter (for those of you North of the Equator)/ summer (for those in the Southern Hemisphere) is treating you all well.

 

After a bit of research and numerous drafts, here's my final wiring schematic:Wiringschem1.jpg

 

I'm now waiting for all the part to arrive so I can start plumbing this in and hopefully will be able to fire it up next week.

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Good evening, all.  Here's the progress from this week.  I've got everything plumbed in (except the propane tank), wired up and just now plugged it in and flipped the power switch on.  No sparks!  The main NC valve clicked open, the blower started, and when I turned the high flow switch to 'ON', that valve clicked open, and clicked shut when turned back to off.  Nothing happened when I turned it to 'AUTO', but I'm not sure if that's something I need to worry about yet because I haven't done anything to program the PID.

 

20200124_181600.jpg

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