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How Does A Gas Kiln Controller Work?

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I understand the basic concepts of the controller system for an electric kiln. But how does this work in a gas kiln?  

 

If I were to build a control system, I would build a manifold with multiple solenoid valves arranged in parallel. The first line in the manifold would always be open giving a base rate. The next 4 or 5 valves would be attached to a solenoid, each connected to the controller.  The controller would open or close as many solenoids as needed to achieve the desired BTU/hr.   

 

Is this correct?

If so, how many solenoids are in a typical manifold?

If my idea is off base Teach me how it is done.

 

If anyone has a file or diagram to share, I would love it. :D

 

 

Jed

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So much about working with clay is a hands on process. I personally resist the idea of centering devices, for example, because I need to feel in control and not rely on external equipment to do what I am fully capable of. For this same reason I want to be intimately involved in firing a gas kiln.

 

Perhaps a controller would balance the temperature throughout the kiln, adjust the atmosphere and maintain an appropriate heat rise better than I can but I am not willing to let go of my involvement in the firing. I need to be there, adjusting the flue, the air, the gas. Watching the flames and the color of them escaping from spy holes is too mesmerizing for me to hand it over to an electronic device.

 

It isn't that I am opposed to technological advancements. Hey, I love my iPad. I just enjoy ceramics for its most basic earth, air, fire and warer aspects.

 

You may be different, so good luck.

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Guest JBaymore

As a pro kiln builder..... YEARS ago (back in the early 80's) I did some work with automated stuff...... more like industry uses.  We used proportional valves and servo-like actuators for controlling air and gas valve positions for rate of climb and damper settings.  EXPENSIVE stuff.  Lots of maintenance.

 

Haven't touched "automated" since then for building kilns for myself or clients.  I'm a "hands on the kiln when you're firing" unless you ARE doing industrial type stuff kind of guy.

 

I think the Geils and Baileys are almost for sure using servomotors for damper control from what I've looked at.  You know...... I never paid attention to the way they are running the gas and air valves.  Bet it is servos.

 

Can't see some sort of digital-type "pulse" firing (on / off) to be the way to go with fuel.  But open to learn something.

 

best,

 

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

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There are two ways to do it. The simple system, like what is used on the old Alpine kilns, has a standard industrial temperature controller hooked up to a single solenoid on the main gas line. You set the gas, air and damper where it needs to be to reach temperature, and the controller opens and closes the solenoid as needed to increase temperature. The problem with this system is that every time  the gas shuts off, you lose the pressure in the kiln. That pressure is what keeps the firing even from top to bottom and throughout the kiln. For bisque firing it works fine, as some unevenness isn't such a big deal. For doing an actual reduction high fire, it doesn't work. There are too many adjustments to the gas, air and damper that must be made for a successful firing.

 

To overcome the problems of the simple system, you have to have a motorized gas valve that can adjust the flow of gas, rather than just turn it on and off. This helps a great deal, since the pressure in the kiln can be maintained. To do a truly automatic reduction firing, though, you would also need at least two thermocouples to check for evenness, an oxygen sensor, and a motorized damper. Sophisticated computer software would be required to makes all the systems work together. Geil has a system like that. Blaauw kilns seem to be all the rage at universities now, with fully automatic fast firings.

 

If you have the money, go for it. If not, either fire manually (which I think is one of the joys of firing with fuel), or save yourself $40,000 and buy an electric kiln.

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Guest JBaymore

 Blaauw kilns seem to be all the rage at universities now, with fully automatic fast firings.

 

 

yeah.... the Blaauw kilns are amazing.... basically industrial kilns but de-sized and de-tuned and de-priced for studio artists (almost). 

 

At the college we have certainly discussed them and met with them...... but shy away from such "high tech" stuff for deliberate reasons.  The main one is that we are preparing students for getting out of school and setting up studios and working.  It is hard enough for most to purchase an ELECTRIC kiln let alone site build a gas kiln.  The reason....... MONEY! 

 

Even a Bailey or a Geil commercial unit without automatic controls is a serious piece of change that is out of the picture for most folks for a long time.  Rearing students on stuff like a Blaauw kiln...and creating any level of expectation that they can realistically "go there" until they are very far along in a successful career is a dis-service to them.  $40 K for a kiln is a LOT of money to earn back.  Takes a while for the fuel savings and lower level of seconds and waters to pay for that.

 

So our students learn to use electric kilns and gas kilns and wood kilns.  They learn to design and build kilns.  They have site-built and commercial gas kilns to use.  They learn to use digital controllers on electric kilns.  They get info on costs to build/buy and operate.  They get to fire at high fire, mid-range and low fire.  They have "options" when they graduate.

 

Someday.... they might even decide to own a Blaauw (or the equiv.).

 

best,

 

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

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I understand the basic concepts of the controller system for an electric kiln. But how does this work in a gas kiln?  

 

If I were to build a control system, I would build a manifold with multiple solenoid valves arranged in parallel. The first line in the manifold would always be open giving a base rate. The next 4 or 5 valves would be attached to a solenoid, each connected to the controller.  The controller would open or close as many solenoids as needed to achieve the desired BTU/hr.   

 

Is this correct?

If so, how many solenoids are in a typical manifold?

If my idea is off base Teach me how it is done.

 

If anyone has a file or diagram to share, I would love it. :D

 

 

Jed

I automated my gas kiln which is a Bailey studio down draft 24 cuft and has two burners.  I used a modulating gas valve on the main gas line feeding both burners.  The valve is set so that it doesn't shut off tightly, so the standing pilot is always on, and so is the burner.  I also limited how far open it will go so a good air gas ratio is always maintained.  The auto part of the firing is only used up to body reduction when the kiln is then put on manual and the rest of the firing is done on manual.

David

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The last company I worked for did fire resistance tests. Just imagine a 3 meter wide, 1 meter deep, 4 meter kiln. A potter could make something huge! For the standardized fire test a specific curve and pressure must be followed. This test is what gives a fire door a 1-hour rating etc etc.

 

The company was switching from diesel firing to a fully automated gas firing. And all the work was being done locally. Thankfully I wasn't involved! This particular kiln had 9 zones and 32 burners. So. Many. Problems. Took more than a year (working at a NZ pace). But most of the problems are something a potter could understand.

 

The control software side will get messy. You care about temperature and O2 levels and have control over gas flow rate and air flow rates.

 

The design process would start with: how large is your kiln --> how many burners do you need.

After that I would just fire it by hand with digital monitoring of all the sensors. Record everything so that you can do dry runs to see if the control system behaves correctly at different times.

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Guest JBaymore

HERE is a purchase proposal I found on the 'net from the University of Washington for a Blaauw gas kiln with two cars. Total cost: $90,368.00

 

 

Think I'll get a couple.  ;)

 

 

PS:  Read down that proposal form.  It is screwed up.  It starts talking about camcorders not the Blaauw kiln!

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HERE is a purchase proposal I found on the 'net from the University of Washington for a Blaauw gas kiln with two cars. Total cost: $90,368.00

 

 

Think I'll get a couple.  ;)

 

 

PS:  Read down that proposal form.  It is screwed up.  It starts talking about camcorders not the Blaauw kiln!

 

 

I saw that, too! A little cut and paste error.

 

I can sell you 5 really nice front loading electric kilns for that price.

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HERE is a purchase proposal I found on the 'net from the University of Washington for a Blaauw gas kiln with two cars. Total cost: $90,368.00

 

 

Think I'll get a couple.  ;)

 

 

PS:  Read down that proposal form.  It is screwed up.  It starts talking about camcorders not the Blaauw kiln!

 

When you do, invite me over....

 

 

jed

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I understand the basic concepts of the controller system for an electric kiln. But how does this work in a gas kiln?  

 

If I were to build a control system, I would build a manifold with multiple solenoid valves arranged in parallel. The first line in the manifold would always be open giving a base rate. The next 4 or 5 valves would be attached to a solenoid, each connected to the controller.  The controller would open or close as many solenoids as needed to achieve the desired BTU/hr.   

 

Is this correct?

If so, how many solenoids are in a typical manifold?

If my idea is off base Teach me how it is done.

 

If anyone has a file or diagram to share, I would love it. :D

 

 

Jed

I automated my gas kiln which is a Bailey studio down draft 24 cuft and has two burners.  I used a modulating gas valve on the main gas line feeding both burners.  The valve is set so that it doesn't shut off tightly, so the standing pilot is always on,  I also limited how far open it will go so a good air gas ratio is always maintained.  The auto part of the firing is only used up to body reduction when the kiln is then put on manual and the rest of the firing is done on manual.

David

 

This is what I was wanting to achieve by using multiple two way on-off solenoids in parallel.  Once at reduction temp range the air flow and damper would all be manually controlled.  Do you remember the valve manufacturer and serial #?

 

 

Jed 

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If you're doing the damper and air manually anyway, what's the point of spending all that money on automating the gas flow?

  ..... Well, ....I couldn't sleep last night.  and in my restlessness I had a vision of the solenoid manifold.  (not quite as  exotic as the "flux capacitor")  I thought it might be a cheaper way to control gas flow.

 

Neil, you are very right.  Why automate only part of the kiln?   Perhaps a few more sleepness night will give me a cheap way to control the airflow and damper..........lol.

 

 

jed

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I understand the basic concepts of the controller system for an electric kiln. But how does this work in a gas kiln?  

 

If I were to build a control system, I would build a manifold with multiple solenoid valves arranged in parallel. The first line in the manifold would always be open giving a base rate. The next 4 or 5 valves would be attached to a solenoid, each connected to the controller.  The controller would open or close as many solenoids as needed to achieve the desired BTU/hr.   

 

Is this correct?

If so, how many solenoids are in a typical manifold?

If my idea is off base Teach me how it is done.

 

If anyone has a file or diagram to share, I would love it. :D

 

 

Jed

I automated my gas kiln which is a Bailey studio down draft 24 cuft and has two burners.  I used a modulating gas valve on the main gas line feeding both burners.  The valve is set so that it doesn't shut off tightly, so the standing pilot is always on,  I also limited how far open it will go so a good air gas ratio is always maintained.  The auto part of the firing is only used up to body reduction when the kiln is then put on manual and the rest of the firing is done on manual.

David

 

This is what I was wanting to achieve by using multiple two way on-off solenoids in parallel.  Once at reduction temp range the air flow and damper would all be manually controlled.  Do you remember the valve manufacturer and serial #?

 

 

Jed 

 

The valve is a Maxon butterfly valve, CV-BV series.  The actuator is a Belimo AF-24-SR and the controller is an industrial 4 to 20 MA output controller with a programable ramp rate, Auto/ manual control, type K thermocouple.  It is possible to find controllers as a surplus or used item.

David

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I have shown my naivete......I failed to recognize the gas kiln as "the ultimate tool of the true potter."  It sometimes is the effigy of the kiln gods and is therefore a bit sacred.  

 

I am so unfamiliar with the true culture of gas firing. I apologize for suggesting changes.  I realize I am like a new painter critiquing a master's creation. I'm just very new to this.

 

I have struggled firing my 3.5 cu ft conversion kiln and wanted to make my larger project kiln easier to master.  I have increased the gas when I should have lowered the gas.  

 

This thread reminds me I have so much to learn.

 

jed

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Guest JBaymore

 

I have struggled firing my 3.5 cu ft conversion kiln.........

 

Jed,

 

It is not a 'sacred cow', at least for me.  There is a reason industry does what it does as far as their kiln technology.  There is no question that automated controls using seriously precise technology and engineering can produce the level of consistency that manual control and lack of serious technical support cannot.  BUT.... and that is a big "but"....... all of that comes at a price.  The big question is, "Is that price worth the returns?"

 

USUALLY... for studio artists.... the answer is "no".  But not always.  Each case is an individual one.

 

Those Blauu kilns are fantastic.  They are also very expensive.  So one has to weigh the cost/benefit analysis.  Automated firing is easy and pretty darn cheap to add to electric kilns...... so the "Do I adopt that?" question gets a pretty fast "yes" answer.

 

Maybe part of the "issues" that are driving you to seek more "control" by heading down a technological route are rooted in your experiences with that type of kiln.  I've been around the block.... and NEVER have seen one of those little "convert an electric kiln to a gas kiln" or even the commercial small updraft "gas kilns that look like an electric kiln" to work very well.

 

If there are no other choices... they allow someone to do fuel firing in a situation / location that a more "formal" gas kiln is not possible.  In that case, the trade off is that they do not work all that well.  You tend to accept that potential as the "price of admission".

 

A decent gas kiln is NOT all that hard to learn to fire.  It is also not all that hard to manually control for pretty consistent results. Add in a quality pyrometer with multiple probes, and an oxy-probe to take the visual guesswork out of adjusting reduction conditions (the big issue in manual control) and you can do pretty well.

 

The time to decide if something like automation is appropriate for one's self is when you almost don't totally NEED to use it.   When you have a skill and experience base to evaluate the tools f rom a basis of knowledge, not from a position of lack of understanding. 

 

It is similar to my pet peeve with the Giffin Grip.  The time to think about getting one is after you don't NEED it to solve re-centering issues.  Then you can really evaluate the tool and its potential benefits and potential payback.  If adopted tooearly .... it stunts some skill development.

 

Do you have anyone that fires gas nearby, with a larger more "formal" kiln, that can teach you?  It is a hands-on process.  And it takes a bit of time to learn the skills.

 

best,

 

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

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I cannot wrap around any reason other than mass production to automate firing in a gas kiln.We as potters want to be involved in the process .

I use the controller to easily get to the body reduction temperature at any rate of rise I want with no risk of going too fast or slow or reducing instead of oxidizing.  From then on it is hands on control of the firing.

David

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David

My fiends with old Giels use them with that older Giel DD control to oxidize as well to body temp where it holds until they can dial it Manuel into a reduction. They also dial it so its a fail safe shut off from that body point upward in case they fall asleep.

I get all that but I thought the original poster here wanted all automated system.

Sounds like you have your kiln set up like that Giel DD controller now as well.

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