Den:
I've been trying to decipher all the different posts on the constrution of a vac kiln and put together a pictorial of what I thought the components would look like grouped together. I'd like you to look it over and see what additions(or deletions) and the rights and wrongs of it. I just trying to get it composed so I can see what all parts will be needed.
(https://forestryforum.com/images/04_01_03/vac%20kiln.jpg)
Could you explain the operation of the controller.
DanG. I was half way through a lengthy post and my computer lost it. I will do this in short 'burst'.
I suggested discontinuous vac drying because it is the only technology within reach of even the best back yard mechanic. You have the basics in your diagram. The details that will make the system work better will be discussed in future post.
The controller that could make it automated could look like this. A controller will look at wood temperature with an RTD. The operator will compare different samples and decide which will be used for control. The controller will look for low temperature. When it is low enough, the vac will be switched off. A solenoid valve will bleed air into the chamber. A solenoid valve will open to let water into the heat exchanger. A contacter will start a fan. A heat control system will control the temperature of the water. A ball valve will open to let water out of the chamber.
When the wood is warm enough to build the necessary vapor pressure, the heating circuit shuts off. The vacuum pump starts with a contacter. The seal water to the pump starts with a solenoid valve. The pump pulls open a ball type check valve. Evaporation from the wood begins. As the chamber pressure decreases, evaporation occurs from within the wood, not just off the surface. This is what makes vac kilns capable of drying thick stock rapidly.
After a while, the pump has pulled as low as it will go. The wood has cooled because of the decrease in the boiling point of water. The controller shuts off the vacuum pump and switches back to the heating cycle.
The vacuum kiln looks very interesting and I will be anxious to see the rest of the information. In the mean time, how much vacuum is required? Why intermittent?
:P Pat :P
Patrick, without Den having to repeat all the info, check back to the thread "A kiln for bowl drying", or something close, in this Drying Forum.
This latest info is a diagram that will co-incide with that thread. This is GOOOOOOD info, Den
Biggest problem I have is finding a place to set this sucker up. ::) ::)
You need cooling water for the vacuum pump. This could be a partial recovery system. The water from the pump goes into a tank. When the water in the tank gets too warm, fresh water is added as warm water is dumped. This could be done with a temperature controller and a float valve. I use little cooling towers. When the water gets too warm, it's pumped to the top of an evaporative cooler. When too much water has evaporated, a float valve lets fresh water in.
If you are hot rodding the process with condensers, the same water is used. A cooling water pump runs constantly to circulate water through the system.
Fla._Deadheader,
I have 230 acres up here with at least half of it open if you want to set it up here on shares. I can even give you a chance to try freeze drying for half the year. :D :D ;D
That's an offer that's hard to refuse, but, naaahhh. With Gasoline going to $3.00 a gallon, I can't afford the hauling ::) ::)
Den: What makes up the brain of the controller? In other words what is telling the contactors and solenoids to operate?
Can there or should there be more than one RTD? By RTD are we talking a thermocouple or a gas filled bulb and capillary tube?
In one of your earlier post you described the condenser. If I understand your description the vapor being pulled from the wood and chamber will condense into a liquid and run back into the chamber to later be exhausted through the drain. Is that correct?
Could the drain also be a solenoid valve connected to the controller?
I would say that the 'brain' of a controller is a module called a 'loop controller'. The devices have a keypad, display, input buffers, built in software and everything needed to survive the real world. Jason (where is he?) would say to use a PLC and build your own circuit and software. Loop controllers cost between $250 and $350 so I don't mess around with PLC's.
I would have more than one RTD. RTD's are neither thermocouples nor capillary devices. They are precise resisters which change with temperature. Most all controllers can read an RTD. RTD's don't need special wire like thermocouples.
The drain could be a solenoid valve but actuated ball valves work better in this application. With our commercial vac kilns, a PLC watches water level in a tank that collects water from the chamber and condenser. I use a PLC here because it can do math calculations. When the tank is full, the PLC bleeds air into it. A ball-type check valve closes off the chamber. A little pump removes the condensate. The PLC calculates and displays the approximate MC and drying rate.
QuotePatrick, without Den having to repeat all the info, check back to the thread "A kiln for bowl drying", or something close, in this Drying Forum.
I read the bowl drying thread. I didn't see the part where it told how much vacuum.
:P Pat :P
Instead of thinking vacuum, think reduced pressure. The atmosphere over your head is heavy enough to push a column of mercury 760 mm high. Vacuum reduces pressure.
When there is 760 mm of pressure on water, it has to be heated to about 212'F to make it boil.
If you reduce pressure to 50 mm, water will boil around 115'F.
'Millimeters of mercury' is a mouthful so the term 'Torr' is used. One Torr is one millimeter of mercury.
A two-stage, liquid ring vac pump with cold seal water can reach to around 28 Torr. If you pulled this low, you would be boiling water around 82'F. If you can pull 50, you're still safe with most wood.
If I've said it once, I've said it a thousand times. :D
Den: How hard is it to setup or program the loop controller?
I found a site on PLC's that is very helpful with the understanding of how they work. Plan to spend a little more time trying to figure out what it would take to get one of them to operate correctly.
http://www.plcs.net/
Loop controllers are very easy. You set the hardware so it knows what the inputs and outputs will be. Then tell it if control is direct (response to an increasing process value) or reverse (response to a decreasing process value). There's a whole bunch of possible parameters but most can be ignored.
With our hypothetical controller, we could tell it to look for an RTD input and respond to a decreasing temperature. A setting that is often called hysteresis sets the deadband. We might set the hysteresis to energize a double throw relay at, say, 105'F. The relay could energize the actuators needed to run the heating cycle. When the controller sees the other end of the deadband, maybe 115'F if our setpoint is 110'F, the relay output de-energizes and starts the vac cycle.
I think that Garrett has links to Partlow's 1160 and Future Designs' 9300 from our website. They are two very good, low cost loop controllers.
Den,
Would a vane type vacuum pump work from a old milk machine system. Our 7 HP vac pump for our milk system can pull 28-29 inches of mercury and has a 100 cfm capacity. It uses an oil drip lubrication system and a reclaimer to recycle the oil. They seem to run forever as long as the oil is flowing.....
These can be had at farm auctions for about 200 bux because they are too small for the corporate farms.
Jason
Hi Jason,
I've been wondering where you were.
That vac pump you mention sure sounds like it would work but 7 HP is a lot to burn for a little kiln charge. You should be able to dry 1000 bf with about 2 HP.
Den
Den, I looked up the partlow controller and printed out the operators manual for it. I'm part way through the manual and was wondering if it would require more than one of these to operate the different devices on the kiln? The price on the web site was $162.35.
You might use one Partlow to switch back and forth from heating to vacuum. A second Partlow would be useful in holding the heating water temperature where it belonged.
A third Partlow wouldn't be needed for the vac cycle but a third Partlow with a pressure transducer could tell you where the pressure was.
I'm not sure where that price came from but it sounds a little low.
The Partlow's output would set off a chain of events. They could all be done with relays. Some relays would be time delay relays (TDR's). This is where a PLC could look better but you would need to write the ladder logic that would set the relay output. A PLC is a programmable bank of relays.
QuoteJason (where is he?) would say to use a PLC and build your own circuit and software.
Not a PLC but a PIC microcontroller.
Jason
Not defined as a 'PLC'?
Just an itbity one?
Den, I got that price from TTI, Inc.
http://partlow.ttistore.com/
What is the price range of the PLC that would be reqired to operate this kiln?
Jason how much trouble would it be to come up with a working PLC for this application?
A PIC 16F877 is 8 bux and can do anythin you program it to do. It has 10 bit A/D converter, 30+ I/O pins, and 8 k of program space.
You will need contactor's, signal conditioners for the RTD or thermalcouples, pressure transducer, pumps, and solnoid valves that will be the major cost here.
To control temperature with a band gap or dead band is fairly easy in BASIC, which is what I use to program PIC's with. Here is an example for a PIC:
Upper_limit VAR word
Lower_limit VAR word
Upper_limit = 1020 '102 degrees in 1/10ths
Lower_limit = 1010 '101 degrees in 1/10ths
Control:
IF Temp > Upper_limit THEN OFF ' Over upper limit then Heat OFF
IF Temp < Lower_limit THEN ON ' Under lower limit then Heat ON
RETURN ' return leaving heat in last state
OFF:
Out8 = 0 ' Heater Off
MMFlag = 1
RETURN
ON: ' Heater On
Out8 = 1
RETURN
This is what the output would look like:
(https://forestryforum.com/images/04_01_03/bandgap.jpg)
This has been simplified greatly but as you can see it is fairly straight forward.
The output would have a 2N3904 transistor to drive a 12 volt relay or can directly drive a solid state relay with a series current limiting resistor of 220 to 330 ohm.
Jason
Jason, would one PIC be capable of running the different selnoid valves, pumps vac & water, fans and monitor the RTD and pressure transducer?
What would it cost to build the unit and program it?
Shopteacher,
I checked TTI. The base list price of the 1160 is $191. This is with one SPDT relay. However, you ususally find more jobs for the Partlow and need to add outputs. Additional relays cost $27 each and linear (current) outputs cost $48 each. Another option is the RS485 interface board for $64. This allows the Partlow to be connected to a computer.
Den
Looked at TTI again and noticed something else. The new 1160's are called 1160 plus. Output one is removable so they can be sold with no output. Their price doesn't include any output.
Glad you looked into it Den. I'm not very knowledgeable when it comes to electronics and sure do appreciate your input on this.
How would connecting it to the computer help? Old computers are a dime a dozen nowdays. I've seen dozens go to the dumpster. Would be nice if there was a way to make use of an outdated computer to control the kiln.
Teacher...
It sure can be done...years ago I worked in a control room using a 200 pentium processor to run and control an entire processing plant includind a wide variety of sensors solenoids motors ....you name it! the soft ware for commercial applications could probably be had free if I knew who still cared or had it!
shopteacher
I think using a PC would be a great idea. If we could find some PC card that would have the right interfaces you might be able to do it fairly reasonable. If I get a chance I will look around tonight on ebay and other sites to see if I can find some used cards. New cards may be to expense.
I would even consider writing the program that would run the kiln. Writing software for the credit card industry so I do have a lot of realtime software development.
One thing that would need to be address if using a PC is the enviroment that you would have it in. It would need to be somewhere were it does not get to hot.
Ron
Buzz Sawyer : Any and all help is welcomed and appreciated. I come in contact with some industrial boards and computer main frame hardware through a salvage company I'm friends with, but have no idea what the boards are or their use. if you can tell what to look for I'll keep an eye out for it.
ronwood: Your skills as a program could come in mighty handy if we ever get this thing to that point and agian all help welcomed, desired and much appreciated.
8) 8)Boy, Oh Boy I think were on our way. 8) 8)
Teacher
It was pure simplicity...a common desktop computer with a 200 processor...in other words the computers you saw in the dumpster....
on the screen we viewed a shematic of the plant cylinders , motors shakers , temp. control....on screen were virtual slide adjusters and type in variables.
So there was plenty of computing power for this application....the signals were sent to the components of the system (say a on off solenoid) so via electronic messages sent by the computer the elements are run from a booth....VERY simple and compatible with what we are looking at here...the programs are very simple and I know someone who wrote one for home power generation controls....I have always though this would be a good approach
And then your PC crashes and your heating relay is stuck on because if the crash...........
Better have plan B or a fire extinguisher.
Jason
I think you should consider the way we do computer interface. Most loop controllers can have an RS485 interface connection. RS232 can be converted to RS485. Your computer already has RS232. That's the serial port.
If you use a loop controller with a computer interface, the computer can do data logging, historical graphs, etc. It will also give you remote access with pcAnywhere. I can connect to kilns on the other side of the Earth. But, if the computer goes down, nothing happens. The loop controllers keep going.
Man-machine-interface software can be mighty expensive. We can pay $600 to $5000 depending on how many addresses. We use WonderWare.
New loop controllers come with their own MMI software and it is free. But it's not as sophisticated as WonderWare.
Well guys, I'm game for what ever will work and be reliable. As I said earlier, electronics is not my bag so the simpler and easier to understand the better.
Can someone sketch out a schematic? Looking at the different components and their wiring would help me get a better idea of what the electrical system would look like and how it would operate.
I hope we can get a working example of one of these kilns. I think a lot of us small mill operators would really benefit from having this equipment available.
Den, believe me when I say I wish I could just give you a call and tell you to deliver one of your kilns tomorrow. Up to present the mill has just been for my own use and pleasure and doesn't bring in any revenue. As I get better situated and closer to retirement I would like to turn it into a subsidy for the pension.
Shopteacher,
I understand. It's just too bad that I have to make my experience available to our competitors. When too many outsiders were reading the information at our forum, we decided to make people register. Jeff can't limit members so I'll just bite the bullet.
Den
A few years back I worked for a company called Kreuter Engineering Inc. They designed a Digital Control System for HVAC. They had big boards with 32 inputs and 32 outputs, smaller board with 8 inputs and 8 outputs and a small 4 X 4. I had 3 of the 8 X 8's hooked into my house when I lived in Indiana. I could sit at my computer and check temps in 7 or 8 locations (attic, bedroom, shop, basement, return vent,outside air, etc. It controlled the home furnace and A/C. Controlled the attic fans, shop furnace, shop lights, etc. It also recorded a ton of data. I could tell you how many times the furnace kicked on over a given time. How many hours the fan had run this month, this week, this year. What the high and low temps were for each day for the last year, etc. I never touched the thermostats in the house or shop. All three units talked to each other, so I could do the programming and checking from one location. They were powered from 24V transformers, and you could get a little circuit that would power them off of 24 V DC. They were very easy to program.
Kreuter had a number of dealers in the U.S. and Canada. Check with some of the larger HVAC people in your area. The name of the system was KMD. That was for Kreuter Manufacturing Digital.
VA-Sawyer
I've read through all these posting and find it interesting, but too much like work! Where I work we have many large freeze dryers to dry pharmacuticals. I work on the RTD, PLc,t/c, and loop controllers every day. I have thought about bringing in some wood and sneaking it into a dryer ;D
One comment I'd like to make is 1torr=1000milimeters of Mercury not 1mm as stated. Also you can do alot of the controls with relay logic (like the old days) this would be cheaper and easier than a PLC.
Oakie
Oakie,
One Torr equals one millimeter of mercury. One Torr equals 1000 microns of mercury.
Den
To support Va-Sawyer.
I have been wondering the same thing. Most all these questions can answered by a local heat and air conditioning guy. Most of the parts and controls can aquired the same way.The Kreuter Engineering Co is one of the lower end companys that make digital controls. Like VA-Sawyer I have my place loaded with digital controls the ground is full of 24 volt wiring. In previous post we talked about this. From my perspective it dosen't matter what you want to control or how you want to happen you can take a PLC and start your car, turn on you house lights, turn off your shop heat, start the coffee pot or load logs on the mill all while at your computer.
And do all of these at any variable, sequence, time or condition.
Yea Yea I'm a digital control guy.
In fact on my web site before I took it down that was part of my advertisement To Control Almost Anything, From Almost Anywhere, To Do Almost Anything.
(https://forestryforum.com/images/04_01_03/boilerscreen3.jpg)
This is the control screen for a boiler control at a woodworking plant about 100 miles from. We built the controller and the modules have RS485 interfaces.
The 'analog' meter show the output to a freq drive that controls the speed of an auger that feeds dust, chips and shavings. The image below that represents the Partlow at the plant. It shows the setpoint and steam pressure. The up and down arrows let me change the setpoint from here. Below that is a list of program tune parameters. I periodically check their boiler. When the weather changes or the species in the silo changes, I sometimes need to tweak the parameters. To the left is a historical log. I can look at any period from seconds to weeks. I can look at this year or last year or the year before. The graph shows firebox temperature, stack temperature and steam pressure. I can zero in on any of the three for more detail.
This is what is possible with WonderWare. The free MMI software can do similar stuff.
It seems some folk feel that I'm asking a lot of questions that could be answered elsewhere and the information is so common sense anybody should be able to do it. If that's true I'm sorry for taking up valuable server space. The fact that I don't know the answers to the question lead me to ask more questions. Those who are so priviliaged to be familiar and competent in the electronics field, I applaud you. I find it rather difficult to understand the inner working of controllers, plc and PIC's and how to setup and run them.
I had the impression the concept behind this forum was to exchange ideas and knowledge.
The discussion is currently trying to determine the best way for the laymen to develop a custom control system. My opinion is that you should use loop controllers that already have the electronic stuff done. You should extend the range of the loop controllers with relay logic. You could add a computer interface. If you want to do the computer interface, look at Future Designs' FDC9300. It comes with free man-machine-interface software.
Teacher..
for my part I enjoy this thread and appreciate the questions and answers...
It is interesting and a multiple view and input is the key to True inovation, variation and implementation of new or existing technology....so let the info flow!!
(all this post is soley the opinion of buzz sawyer...country hick and mad inventor)
This has been a great thread, I sure appreciate Den helping out with his knowledge. Industrial control is one level of electronics I have no experience in. To simplify it for me has been great. This is more along the line of engineering design than fixing my furnace. It is not simple. Keep asking questions Teach, I'm learning too.
Den
You are right. I was thinking of microns.
Oakie
I can build near anything, but, the electronics part is beyond me.
Let the info flow, and, if someone actually gets one working, I will buy the second one ;) ;D :) :) Might even consider buildingYOUR chamber in exchange ;D ;D ;D
FD
How much money you got?
The control part is the easy part.
sezz you
I wouldn't kid ya :D
All we have to do is heat wood and watch the temp with an RTD. When the wood is warm, turn off water with a solenoid, turn off a fan with a contacter, close a bleed valve with a solenoid, close a drain valve with a ball valve, start a vac pump with a contacter, start seal water with a solenoid valve. ??? hmmm, we'll get what I forgot when we smoke test this bugger.
I do it all the time.
Or you could do it all by hand in your spare time and add automation later.
Den,
That part I understand and won't have any problem installing or hardwiring those components. The part that I get lost is connecting that stuff to the controller and setting it to do the things you just mentioned.
A loop controller might have one input and one output. The input might be an RTD. This is an international industry standard measurement of temperature from resistance. You tell the controller that it is going to measure an RTD and the only question it will ask is degrees C or F.
If the controller has one relay output, that relay will close when the temperature drops past the setpoint. The relay is a switch. You put 120 VAC on one side of the relay and, when it switches, 120 goes to all the places you want. If you want something to start one minute after everything else, you put a time delay relay (delay on) in series with that device. If you want some to turn off one minute after everything else, a TDR again. And you can set those TRD's for any time period you want. Easy?
Den,
You make it sound easy enough and I think I'm getting a pretty good picture of it in my mind (the picture ain't to big though, fits my brain).
How do you set the controller to react when the RTD signals a drop to a certain temp? Do these controllers come with more than one output? Say a NO and a NC so when say the water stops flowing the vac pump starts? Or could that be done with the time delay relay you mentioned?
Thats something I was thinking about the other day; these hot and cold water systems will needs pumps for circulation, right? I was thinking like B&G circulators from boilers.
Got a price on a 20 cfm sihi liq. ring pump $3600.00 new, kind of pricey.
When you order a loop controller, the supplier should ask what you want for inputs and outputs. When you get it, you might be ready to power it up and set some program parameters. If it isn't set up, you might need to enter a model code. Or you may need to set some DIP switches. They are all different but none are too difficult. I may use a couple different brands and models in the same day and I can't always remember what's what. You either pick up the manual or poke, poke and poke the buttons until it does what you want. ;D These things are very forgiving.
The smallest loop controllers usually have at least two or three outputs. They can be double-throw relays with one N.O and one N.C. contact.
Circulator pumps can be small. I usually use Crane/Deming centrifugal pumps.
Somebody wants to make some money off that SIHI. Was it a LPH 25007? Mine cost $1324 but I had to buy a single phase motor for $261 and coupling for 17. Still a long way from $3600.
From the HVAC industry, I'm using some actuators from Belimo. They are designed to operate dampers but I mounted them to ball valves. They are really cheap compared to the stuff I normally use. I have a couple set for open/close control and one is used to control steam proportionately. That one gets bumped one way or the other to give very good control.
Well, I think I've run out of questions for the time being. My search is now on for a suitable chamber. I'm thinking in the area of 5' to 6' dia. X 12' or better long. Would prefer stainless steel, but will make due with carbon steel or Aluminum if necessary. Any body know of anything that might fit the bill. I've been looking on ebay and doing some searches on the net, but find the prices a little high. Any and all help appreciated.
I think that we need to take a close look at that heating cycle. The wood must be heated evenly and yet, quickly. If you are planning to dry lumber, air flow has to go in and out the sides. Last summer, when I was considering end to end (of the chamber), we were looking at drying round billets for baseball bats. If you are planning a small chamber for carving blocks, furniture parts or anything else small, you might want to consider end to end. What you need to avoid is small areas of high velocity surrounded by areas that aren't getting heated. Baffles will help but the job might be easier if the fan(s) isn't too close to the wood.
I been thinkin about one of them 6' culvert pipes??? Them are galvanized ??? ;D
(https://forestryforum.com/images/04_01_03/kilnduct.jpg)
I drew up a little rendition of a round chamber with grating for the floor and duct work run above and below the stack. The duct needs to be sized and reduced at each opening to maintain the cfm and volume of air through out it length. There could be two runs each, top and bottom, to skirt close to the edge of the stack. Small fans could also be above and below to help with circulation. What do ya think?
deadheader,
Interesting idea but don't forget the end caps. You can't have any flat surface or it will cave in.
And I'm no expert but I think that welding galvanized metal releases toxic fumes.
Everyplace I go, I notice compressed air storage tanks.
Don'T weld the galv. That's where injunearin comes in. ;D
Wouldn't be all that difficult. ;) About the cheapest stuff available and has protection, too.
How big are them compressed air tanks??? ??? Seems they would be awful heavy???
shopteacher,
I like that but, if blowing air through lumber, go in and out the sides for better air flow.
If you put a freq drive on that fan, you could adjust the speed and reverse it every couple hours. I like it! 8)
deadheader,
I'm used to heavy chambers. The rectangular chambers I use take a lot of heavy framework. The little 1000 bf vac kiln weighs 4000 lbs.
den
Den, I made a revision so as to have return air be drawn off the top of the chamber. That way the heat would have to be drawm through the stack to get back to the fan for recirculation.
(https://forestryforum.com/images/04_01_03/kilnductR.jpg)
watch out! Butch is standin' on top of the load. :D
FDH, I was just thinking of using 24 ga. furnace duct. If the duct is below the grating it doesn't have to be that heavy or strong. You can get the duct made out of stainless and I would consider that once everything was up and running to satisfaction. Same with the overhead return, just Strong enough to carry the air back to the fan. There could be multiple runs top and bottom to better distribute the flow to and from the fan.
I was thinking of using a condenser from a roof top air conditioner for the heat exchanger. There plentiful and designed to maximize heat transfer. I just seen two that had 3/4" tubing going into the coil and appeared to be about 3' X 3'
depending on the tank size they could be ganged up if ones not putting out enough heat. The unit has a nice squirrel cage blower behind each coil also. You can pressurize the duct with a blower for better circulation and the newer furnaces built for air have 3 speed blowers in them. A simple switch setup could allow you to change air speed for better heat transfer out of the coil.
FDH; I mistook you foot mark for inch. I see now you were talking of making the chanber out of culvert pipe. I'm still searching for a tank and a vacuum pump.
Den; Butch figured we're building a smoke house, he seen all the wood in there and figured he'd be first in line when the meat was done.
I never really understood the use of Blankets in a Vacuum Kiln. I know that they provide heat, but, so would ambiant heat in the kiln along with stickers to allow it to penetrate. What's the deal here?
Tom,
Have you been spending too much time in those political threads? You'll just get irritated reading them. ;)
The deal here is this. Using blankets or heating plates can make vacuum drying very fast but they make the hardware expensive. An Italian had a good idea of heating with no vacuum with warm air, pulling vacuum and removing water and then repeating the cycle. Trouble was that the idea was commercialized with timers running the kiln. We have an idea for a major improvement here. It won't be as fast as 'continuous' vac but the hardware might be built by a few good men. Can I say that? (A few good 'people'.) And it could be affordable.
Affordable would be ground breaking. :D
Wasn't the Wood MIzer Kiln you were consulting and working on, one with blanket heaters? Is that project still one you are involved with? What kinds of sizes and dollars figures do you think this "new" kiln technology you are developing will be? What kinds of time frames are involved?
These could be affordable because these guys are willing to look for used parts and because they are willing to do a lot of the labor themselves.
The WoodMizer VK is a dead project. Electric blankets are not a good method of heating in a vacuum.
With some of the ideas that we are kicking around, I think a 1000 bf kiln could be built for, maybe, $10,000. Automated. By the way, I'm getting some private email from members. Lets lay it all out on the table.
I know a discontinuous VacuTherm that can dry 3.5" Red Oak in about 6 weeks. That is slow compared to our kilns that can do it in 2 weeks but how long would 3.5" take in a conventional kiln - 50 or so weeks? I think a modern design using wood temperature instead of timers might do most lumber in a week. Maybe more for Red Oak lumber. Maybe less for maples and cherry.
Well I'm a rookie at this drying stuff so bear with me a question. Is there any downside to drying wood this quickly. With 8/4 white oak I get a fair amount of degrade and it takes a long time to do it. Ties up my dh kiln.
Doing thick stuff is where it really peaks my interest, 10/4 walnut is something I get quite a few requests for but I'm worried that with the way I dry wood I'm not getting the center down in moisture. Plus custom orders done in a short time would help me out too. People don't want to wait.
Thanks for all the help here Den, I have really enjoyed reading this thread.
Nice drawings Glenn, I can read something forever and not get it through my thick head. One picture and I go "oh yeah".
8/4 white oak is not going to dry like most other species. In fact, we will need to work on a special drying schedule. I'm sure that elevated RH will be necessary.
10/4 walnut is another story. Just a rough guess from experience would say that three weeks might be about right. It all depends on how well these guys get the circulation through the kiln charge. When they get the wood warm, the vacuum is the easy half of the job. If you pull low enough, water is going to evaporate rapidly not only from the surface but also from below the surface. This means rapid drying with minimal degrade. This means thick stock can be dried quickly.
This just keeps gettin better and better. The stuff we get will be "special Circumstance", but, If I can talk the right guy into a spot, I may get started on a chamber real soon ;D
Y'all other guys will have to get yer technical stuff so's I can de-cipher it ;D This just MIGHT work ;) :D
Still playing around with different ways the ducting might be setup. This idea is for a perforated 6 or 8" duct to run through the center of the stack. The pipe would be laid into the stack as it was constructed. The end protruding would plug into a receiver in front of the fan assembly. The far end would be capped. The air would come out in the center of the stack and be forced toward the sides. The ducting underneath would also provide heat to the stack. The overhead duct would funnel air back to the fan. Second dwg is an end view.
(https://forestryforum.com/images/04_01_03/KCduct.gif)
(https://forestryforum.com/images/04_01_03/kiln%20Center.jpg)
Thanks Den, I have more trouble with white oak than any other wood. We let white oak air dry until it's under 20% before drying it in the kiln.
Walnut is easy in comparison. The thick stuff just takes so long. I would like to use a vac kiln for short (less than 6') thick pieces like crotchwood and fireplace mantles. I'm always worried that a mantle is not dry in the center because it's so thick and then stick above a heat source and you'll have more drying and degrade.
On the chamber design I wonder if three small fans along the side would move air better than one big one in the end. Not sure they would fit as well as Glenn's design but the air would move through the stack easier. Just a thought.
Den, are we or should we be thinking about RH sensors and incorporating them into the controller program?
No. RH sensors are a lot of trouble and you won't need RH control for most drying situations. Green white oak and heavy red oak might be a couple exceptions. I'll think of a way around it.
I'm going to be doing installations 'down south' for the rest of the week. I'll be leaving in the morning and will return Friday or Saturday. So don't be alarmed by my disappearance. :D
Have a good trip Den and don't go getting use to that sunshine and warm weather. It's only Feb. ya know.
Anyone think of useing an airconditioner compressor to draw the vaccum. I've used them before to draw a vaccum in smaller containers, they move a lot of gas and draw a good vaccum. They can be found for free quite often on old systems that don't work anylonger due to coil leaks.
I use compressors to test controllers. They are fine in dry systems but we would be pulling water vapor into the compressor.
I'm back and I sure did not see any warm temperatures. In fact, North Carolina looked like Alaska!
Well, I guess your in for a treat. Suppose to hit 60 here this weekend. Heard form a friend in Charlet, NC that they had 8" and looking for a lot more.
Still looking for a tank. Haven't been able to come up with anything suitable yet.
Den, am I right that the tank can't have flat end, but needs to be domed or dished out?
Yes for the rounded ends. You don't want any flat surfaces unless the tank was designed for vacuum. If you look at chambers at our website, you see lots of flat surfaces but there is a lot of framework on the outside to keep those flat surfaces from getting crumbled.
I think it was closer to 18" of snow down there. Glad to get back up here! :D
I got back into this one a little late, but please let me ask a few questions. As I understand it, the plan is to circulate heated air around the wood at normal air pressure, then after it is hot, turn on the vac pumps and pull the moisture out. The cycle keeps repeating till the wood is dry. Do I have it right ?
The fans are useless during the vac phase because there isn't any air to push around. They are only used while the pressure is high. Isn't this true ?
Having been through the Altitude chamber at Wright Patt AFB, I can tell you from first hand experience, the temp will drop dramaticaly with a drop in air pressure. Won't that reduce the benefit gained from heating the wood ?
Would one of those large Propane tanks ( say, maybe 1000 gal or larger) work for the vac chamber ? I think most of them are rated for 150 psi or more of pressure. I would think they could stand 10% of that in vac. Just saw off one end and hinge it to make a door. Make sure it is empty, purged, and filled with inert gas before doing any work on it.
I know that convection isn't worth squat a low pressures. You have to use conduction or radiation to move heat under such conditions. How about using heat lamps to supplement the heating during the vac phase?
Shopteacher,
When you want to send an email, you call up your favorite email program, tell it who you want the message to go to, what you want the message to say and press send. It does the rest for you. Good software for digital control units works on a similar level. You don't have to worry about the behind the scenes stuff too much. I know when I started with the KMD system, I spent way too much time worring about how I was going to make it work. I learned the hard part was figuring out what it actually needed to do step by step and under each possible condition. Once I had the flowchart logic done, the software made writing the program pretty easy.
VA-Sawyer
VA-Sawyer,
You have it correct. Heat and then pump out the water. And, yes, the fans are useless in a vacuum.
The drop in temperature when you pull the vacuum is the result of water evaporating. The energy that you put in during the heating cycle is used during the vacuum cycle.
I'm still a fan of the propane tank idea. You could build a little dryer for carving blocks or a big kiln for lumber. After you cut the end off, weld a pipe flange on the pieces. Then put some strips on the flanges to support a neoprene extrusion for a door seal.
I think heat lamps would be too localized unless we put the wood on a rotisserie. :D
VA Sawyer: Thanks for the analogy. I get a little hyper when it comes to electronics and programing. I don't have anybody thats proficient in that field and will have to depend on the good people and knowledge here on the forum.
I also like the propane tank, just haven't been able to locate one large enough as of yet.
Den, I've seen large tanks listed on the net that appear to be made out of some pretty heavy material (3/16 SS) but have a very low psi associated with them. Is there any way to tell if a certain volume tank with a certain wall thickness will withstand the vacuum without collapsing?
We would need a Mechanical Engineer to calculate the minimum wall thickness. All I can say is from experience. Pressure vessels always have thicker walls than vacuum chambers. I've seen stainless down to 1/4" and carbon steel down to 5/16".
That Cigomak at our website (the one 'destroyed' in a fire) was 5/16".
DanG! :D A company that had been talking about buying one of our kilns called this morning. I thought they were ready to order but no. >:( They have been building this discontinuous vac kiln! and reading this thread! :o OK Steve & Henry. Are you going to join in the discussion?
Hey, that ain't playin fair ::) ;D ;D :D :D
Hope them boys share their info with the rest of us. This Forum stuff is great and the problems one has, as he gets his unit working, will benefit the rest. C'mon guys, WHERE'S THE PICS ;D :D :D :D
Yes I'm one of the 1038 peeps trying to absorb all this information ;D I personally wanted to purchase a new system but my Father/business partner LOVES to build things. So far we have built a rectangular chamber out of carbon steel instead of stainless. Stainless would be far superior for this application but it's alot more expensive.
The information posted in this thread is priceless! I would like to thank Dennis for his time and for sharing all of his ideas. I'm sure he spent countless hours researching.
I'm going by the shop today and take a couple of pictures. There are still alot of details that we haven't worked out but I'm hoping to fill in the missing pieces from the info posted here.
Best Regards,
Steve
Steve,
After I talked to your Dad, I'm thinking that you guys should pull a vacuum before spending any more time or money. Go to a refrigeration repair shop and ask for an old compressor that runs. Connect the suction side to the chamber. Put a cheap $10 vacuum gauge on it. And a bleed valve just in case you do pull vac and nothing breaks. ;D See if you can pull any vac. My guess is that you'll never get a 16' door sealed. If you do, pull as low as you can. You need to get to 28". A mechanical gauge might read anywhere from 25 to 30+. Watch very carefully for deflection. If any welds break, you're going to jump out of your skin from the noise. :o
Den
PS Put a ball valve between the compressor and the chamber. If you pull vac, see how long you can hold it.
Steve,
How thick of metal did you use for the wall of the chamber?
Playing with a little math here... Did I read it correct ..a 16 ft wide door ? If you are pulling a vac of approx 26 " hg this translates to about 13 psi differential pressure. I don't know how tall the door is, so will work out the load for 6,8 and 10 ft high doors.
6 High by 16 Wide is 96 sq. ft.
8 High by 16 Wide is 128 sq. ft.
10 High by 16 Wide is 160 sq. ft.
There are 144 square inches in a square foot.
96 X 144 = 13,824 sq.in. times 13 psi pressure diff = 179,712 lbs total pressure on the door. About 90 Tons !
128 X 144 = 18,432 sq.in. times 13 psi = 239,616 lbs total pressure on the door. That's 120 Tons
The 10 ft high door will have almost a 150 ton load applied each and every time you pull vac. That is like having a B-747 roll on and back off your door every pressure cycle.
Metal fatigue from flexing can lead to rapid failure of the structure. You will have to design it for around a 300% safety factor compared to the normal 150% for static structures. Now you are talking about a door able to support 450 tons. That is almost a million pounds !
I wish I had some pictures of the altitude chamber at Wright-Patt AFB to post. It is the only flat sided multi cycle pressure vessel I have seen up close. Built like a "brick s*** house" and then some.
VA-Sawyer
My partner in AR came up with a great idea.
Although it may be to small of a chamber for large loads of wood it would work fine for smaller loads.
In the Military we shipped Jet Engines in Sealed steal containers that looked like a mini submarine. Once the engines were installed we pulled a vacume on them and closed the valve. The have a top half and a duplicate bottom half. The check vavles are already installed on them on each end.
They are readily available at most DRMO facilitys on Military bases. DRMO deals with getting rid of old military goods.
I cant imagine why those containers couldnt be configured into a vac Kiln.
When you guys get this stuff worked up let me know. I want one! Unfortunatly my brain is to small to understand all the details your throwing out there.
Hey Kirk. Got a pic or a website that shows them things???
Kirk,
Pretty good idea. I had forgot about those things. They cost Uncle Sam a lot to buy, but they might be affordable now. I'll try to check around and see what they are selling for on the "surplus" market.
VA-Sawyer
I dont have a picture of one but I will try to get one.
My buddy is just outside Little Rock and he should be able to go to the engine shop and get a picture of one. I will touch base with him and see what he can do.
Allison has them in massie quantities as they are the OEM for the Allison T56 engines for the C-130s. If I recall there was a Allison jet engine plant in Indy years ago but I dont know if they are still there.
If you guys are using carbon steel for a chamber to vac dry RO you will rot the chamber in a matter of months.
When we started drying in our cabon steel kilns we saw rust in weeks and holes in two months.We sand blasted the kilns and painted them with the stuff they use inside tank cars that haul fuel.Im not sure but I think within a year we were shutting the kilns off one at a time and welding stainless steel inside of them.This was about 8 or 9 years ago and we have not had any trouble.There is a reason that Den preaches the use of SS.
Hi old3dogg. Welcome to the forum.
Are ya talkin about yer own kilns or do ya work for "the man" ??? Tell us more, specially since ya got sperense ;D ;D Got pics ??? We LUVS pics ;) :D :D :D :D
I work for the man.17.5 years! 13 have been involved with vac drying.I will get some pics and post them soon.Looks like I am almost done working for the man.
Welcome aboard old3dogg and good to have another with knowledge on kilning.
I work for the woman ( wife ) but she's in Mexico City and I can sit back and do nothing now.
Does that title mean you got 3 old dogs? If so you'll have to introduce them to old Butch.
I had 3 old dogs and was a huge Dale Earnhardt fan.
One of the dogs passed on and sadly,so did Dale.
The name just stuck.
Mike,
I got the idea from your thread at WoodWeb that BWP was going to dry lumber in their vac kilns. No go?
Den
I had too much fun last night when a lot friends showed up for my wife's birthday party ::) but I'm trying to think a little about a control system.
I'm going to assume that water temperature is under separate control. Again, when the wood is wet, we don't want to get it too warm. As the load comes dry, we will need to raise the temperature. It would be nice to have a loop controller here but a thermostat on a water heater would probably be close enough.
I said before that we would want multiple temperature probes (RTD's) and I would have multiple RTD's in a commercial setup but here, to keep things simple and low cost, we'll use one. One RTD (carefully placed in the kiln charge) connects to one loop controller with one double throw relay output. The output toggles between a Heat Cycle Relay (HCR) and a Vac Cycle Relay (VCR). VCR has a two minute delay-on.
One N.O. contact in HCR energizes an actuated hot water valve which is N.C.
Another N.O. contact in HCR energizes an actuated air bleed valve which is N.C.
Another N.O. contact in HCR energizes an actuated drain valve which is N.C.
Another N.O. contact in HCR energizes the fan starter(s).
All valves are ball valves. Belimo actuators on Worcester valves with motor mount kits are one possibility. Fuses should be on everything. The fan motors are going to take a beatin'. VacuTherm stuck the motors outside and ran the shafts through the chamber wall. Fans in conventional kilns take a beatin' and survive.
When the wood is up to the setpoint, the loop controller switches to VCR. While VCR times out, the actuators close the valves.
One N.O. contact in VCR energizes the vac pump starter.
Another N.O. contact in VCR energizes the seal water solenoid valve. And that's it.
Den, this is starting to make sense to me. Yer doing a fine job explaining the controls. I got my eye on a BIG heavy duty tank. Need to find a place to put it. Thanks for having the patience to stay with this. Your input is greatly appreciated.
FDH, I got a place for you to put that tank, it's 30 mile SW of Pittsburgh. ;D
I'll deliver the tank to your place: you deliver my lumber to me. ;) :) :)
Ok, I may have a solution to one of the problems. Surprised I ain't thought of it before. Why not spray the inside of the chamber with the spray-on bed liner stuff, like "Rhino-Liner?" Come to think of it, you could use it inside any kind of kiln, to eliminate the rust problem, thereby making a kiln cheaper to build. :)
DanG, I was thinking along the same line. Here's a link to a site that looks to have some very promising material. I think I'm going to get some and try on my concrete driveway this summer. They say it has a life time guarantee.
www.sanitred.com
On a vac kiln, once the wood is dry, do ya still need to raise the temp to 160° for 12 hrs. to kill the bugs and aigs???
Will that spray on stuff be stable at the high temp???
Sounds like a good idea. ;D ;D
Why not build the chamber out of wood? I think if you used 2x6 or even 2x8 studs glued to 3/4 plywood,with the interior glassed with epoxy(high heat type),it would be rugged enough.They build boats like that, and they get thrashed real good. my $0.02 cents worth
I'm pretty sure it would be ok at that temp. 160 is really pretty chilly.
BTW, Mr. Hootie has some tanks that may, or may not be interesting. He has an old-time propane trailer with twin tanks. They are about 3 1/2 ft diameter, and 35 ft long. Didn't ask him what he wanted for them, though. He also has an old railroad tanker that would be PERFECT! I told him I'd have to rent space from him, though. :D :D He also has an evermore stack of aluminum heat exchangers...all brand new. There are no tanks on them, but they look mega-super for kiln operations. If a body could weld aluminum, they would be ideal. Found a whole stack of aluminum sandwich panels, with 2" of foam. They were parts for roll-up doors on reefer trucks. He's asking $5 each, but said he'd work with me on it. ;D His son-in-law, the guy that helped load the HootieMobile, is a refrigeration guy. He's beginning to take an interest in this kiln drying thing. Could be a real help to me. :)
Or if that isn't high tech enough you could cold mold any shape you want.With a half or third mold you lay up veneers in epoxy, like plywood formed to the shape of the mold. the separate layers are 90 degrees to each other, and they can be stapled temporarily to the mold.This technique makes very strong boats. The two thirds would glue together and the final third could be the door? more$0.02 worth
All sprayed coatings have one problem. Any volatile material in or under the coating will lift the coating when you pull vacuum. Coal tar epoxy is used in many tanks. It is suppose to be self-healing.
140 at the core will kill bugs. From what I've seen, just the vacuum will stop mold and fungus.
I think that an epoxy/cloth lay-up would crack pretty quick. One time, I gave a bunch of rusted, carbon steel, rectangular vacuum chambers a new lease on life by lining them with 10ga stainless steel. Sometimes, after weeks of sandblasting, grinding, plug welding, welding continuous seems and capping with SS, we would start the vac pump for the big test. Sometimes, there would be a loud noise and we would open up to find a 24' sheet of SS bent like rubber and laying on the floor. One time, we had done a really good job of making a SS envelope. Old3dogg was routinely pulling vacuum on a green load. The SS broke free of the carbon steel and was wrapped around the load as if the wood had been vacuum sealed. They never did get the cart out.
This chamber may very well implode when we pull a vacuum. The pressure would be no more on a door than a chamber wall. We planned on using removable jacks to support the top next to the door. We also doubled the support beam next to the door. I'm sure that we didn't "triple safety factor" the door since we wasn't planning on entering it in the state fair and we're not interested in selling them. We really just wanted to build one these super-heated steam vac kilns just to see if the concept worked for us. If it does, then I'm certain we will either construct another one (hopefully better) or just purchase one.
On another note.. If it does cave in, it will make for some good pictures and examples of what "NOT" to do. I tried to upload a picture but tells me there is a 15000 byte limit and my picture is over 40000 bytes. My camera is set to normal image quality and the picture size is 640 x 480. Anyone have any ideas on how to reduce the file size?
How much do those motorized ball valves cost???? They sound expencive :o
At what temperatures does the controller react on? I assume this is dependent on species and initial MC.
I see a PIC16F877, 2x24 character LCD, Keypad, multiple thermalcouple to digital convertors(more is better), Time delay relay, handfull of contactors or solid state relays, a few expencive ball valve actuators to be a fairly straight forward controller. Data logging through RS232 could be implemented very easily.
Jason
Steve,
I don't think it will implode. Getting it sealed will be harder than you think, I think. If it can't take the force, it will tear a weld and air will leak in. The danger is this. Suppose you are standing beside it while it's under vac and somebody bumps into it with a forktruck. Then, there could be a major inrush and you could be dead. That's why you need the triple safety factor.
Major correction: we are not building a super-heated steam vac here.
Jason,
A 1.5" ball valve with motor mount is around $250. But slow-closing solenoid valves aren't cheap either. A Worcester actuator for a Worcester valve can run another $600. But these Belimo's that I'm putting on Worcester valves cost less than $100. I've got one controlling the steam that heats my vac kiln. When I got back from an installation a few minutes ago, I checked it. SP = 80.0 and PV = 80.1. 8) perfect proportional control for under $100.
Yes, the heating SP will vary with species and thickness.
I see a guy pushing his complete controller (I/O, processor, buffers, firmware, keypad and display) into it's socket with one hand while he holds a beer in the other. ;D
Den
Steve,
You need to go to the patent office website and review patent # 4,893,415.
I repeat to all, WE ARE NOT BUILDING A SUPERHEATED STEAM VAC.
Den
Dennis,
I did a patent search and read over the patent information. It mentioned "discontinuous vacuum" as one of the directives (claim 12). I seriously doubt I'm comprimising there patent anymore than anyone else on this board.
This does lead me to another question: If it's possible to control water vapor temperature and tranfer heat within the chamber (using heated water vapor) and maintain a continuous vacuum, then what's the advantage of a discontinuous vac kiln?
Perhaps you could enlighten us on the differences between the heavily patented superheated vacuum kiln and the vac kiln we're talking about here.
It's always been my understanding of patents that an individual can build anything for them self and not violate any law as long as its not for sale or profit. Anybody know for sure?
Steve,
The patent for discontinuous vac kilns is expired. Superheated steam is current.
The advantage of discontinuous is it's simplicity. Superheated is not simple.
Water vapor PRESSURE control is possible with heating plates but plates put the cost too high for small guys. Just as the controls for superheated steam vacs. And there is a company trying to make a go of superheated steam. I won't touch it.
Den
confused innocent bystander http://www.micropat.com/og/ogn20020319/patexpi.html
Actually, the whole patent scene is kind of dumb. I read at 'News of the Weird' about some clown who got a patent for swinging sideways - on a child's swing. :-/ It had a link to the patent office website. I checked it out and it was very stupid but true. The article was joking (I hope) that you would have to pay royalties if you wanted to ride a swing sideways.
I was swinging sideways Saturday night!Do you think I copied someones patent?
We are going to dry lumber I guess but I'm not sure when that will be.The big concern with lumber in a vac kiln is stress.I have a test load of 4/4,2comm.RO running now.I should know the stress factor on Monday.By my stress factor I can tell that I will swinging sideways again this saturday night as well.
Shop Teacher.
Where about "Da Burgh" are you located?I'm down that way a couple of times a year.Concerts,football,etc.
Sorry I have been gone for a few days.Crabby internet service.
Mike,
I have Red Oak lumber in my kiln at the moment. If you have a stress problem, maybe I can help you out.
Den
Den.
I started out at a very low temp.35/34.
Im so used to drying squares where stress isnt a factor and the faster the better.
I cut some stress sambles that I can look at through the window and so far they havent moved.Im into the 4th day.
Im at 45/43 now and running at 60torr.I have made about 470 gallons of water so far.The Oak is about 8500 BFT.
Sound like Im on the right track so far?
I have been given 10 days to get it dry and stress free.I know that 10 days is way slow for 4/4 RO but.........
Thanks.
Mike.
Mike,
35'C is about what I normally start. It works with our extrusion but it's hard to believe that your extrusion was warm enough. Were you getting water out at 35?
If I'm really going slow, I might shoot for 6 to 8 days. On the fourth day I would be around 47'C. I would be ramping the heat at 0.2'/hour. So you're about right.
Den
Den.
At 35/34 I made about 40 gallons of water in 15 hours.
I calibrated the heat,pressure and wet bulb at the start of the charge and then around 20 hours into it.The temps and what not were close.
I got a vac schedule for 5/5 RO from a guy who drys nothing but flat RO and the schedule I came up with was close.I wanted to start with 40/39.
I should add that at 35/34 the CP was at 45 torr.
Thanks.
Mike.
Hey Den.
Well it was all for nothing.Got a call this morning at 3am that 16 had a leak.At 3:30 half the load of 4/4 was under water.
Two more weeks of this BS and Im on a loooong vacation.
Mike.
What a bummer. Was it the heating or cooling system? Aren't the high water alarms working?
For those considering the discontinous vac, consider a water level switch in the chamber. Mike's had some high tech capacitance probes that were always screwed up with gunk. A float switch would be more reliable. Then the float switch needs to be able to shut off make-up water and circulation pumps. OR, you need an automated dumping system that can keep up with a leak.
Den.
The high level switch had a small pile of goop in it when we pulled it out.
The leak was a heat hose.from what I can tell from the history on the computer the hose blew at 1:30AM.
Can you believe a half of a 33 foot kiln of water in 2 hours.
Im trying to save what I can of the RO.
Wel the old frustration meter is starting to climb. Haven't had any luck finding a suitable chamber for the vac kiln. Now I'm starting to think about the possibility of building my own or have one built. Den, can you give me a rough idea of material cost for a box 5' X 12'. Are the outer structural support CS and the inside SS? How thick of plate does the box need made of? Do you think an Aluminum dump truck body with a lid welded on top would work?
The following information should help you manage the frustration. :D
The little kiln that I built for R&D is 48" x 48" x 120". It's 1/4" SS with carbon steel channel supporting the SS. Penetrations are SS nipples. The tracks for the cart are SS. The door seal is neoprene. The door is aluminum. The widows are lexan. The outside of the chamber is painted. My cost was $7153. :o Not including my time. There's gotta be tanks out there.
I did a real quick Google search for 'used tanks' and there was a lot of possibilities. I quickly eliminated those overseas and found a really interesting company but they are on the west coast. I didn't spend any more time searching but there has to be suppliers on the east coast.
The 'kids' will have a whole bunch of pictures of the R&D kiln at our website later today. We'll put up enough details that you can copy parts of the heating, cooling and vacuum systems, if you want. But you need to start with a cheap chamber.
One time, believe it or not, I built some vac kilns from government surplus vacuum chambers. They had been used in WWII to fumigate uniforms being brought back from Europe. I found them laying in a field in NY. 8)
I have been following this string trying to understand what is going on. I think I have a small grasp on the technical concept. With that said I think I have something to offer. If this does not make any sense please excuse my exuberance as I am new to drying lumber.
Enough rambling, drawing on my days in the Navy, I searched the web for decompression chambers; for those not familiar with chambers they are used to treat divers that have over stayed their bottom time or as a part of the planned dive schedule the in warter decompression time is too great for in warter decompresion they are scheduled for a surface decompression in the chamber.
There are used military decompression chambers for sale. These things are made from either steel of aluminum with thickness from one inch to one and one half inches depending on the material of construction. These chambers are designed to with stand internal pressure that is equivalent to 165', which is roughly 5 or 6 atmospheres. If I remember correctly an atmosphere is roughly 32/33 PSI.
Based on what I have read here a chamber would work for what is being discussed.
Check out the web link below for a picture of one of the chambers for sale.
http://web.govliquidation.com/auction/view?id=344358
That's pretty cool. 8) Looks like it has a separate control room/office. :D
The outter lock is to send in medical folks and supplies. Some of the decompression schedules wold have you at depth for days.
Gotta have pizza. :D
I just talked with on old Navy buddy. There are some chambers made of stainless. 8)
Hey Ga_Boy,
That would be great and I was already to place a bid until I saw the PR. Anybody got a pair of water wings for a F 350?
I've been looking at the government liquidations, but searching under tanks, found a few good Sherman's but would find it hard to get the wood down that little hatch. :D :D
I've come across some SS tanks in NJ but didn't know what they would weigh so haven't persuaded that avenue. They other thing would be cutting the end off and trying to fit a flange around a 6' opening. SS is some pretty tough stuff to cut. Also don't know the thickness of the wall.
Den, you got some really nice chambers on your site, but as you say rather pricey.
Guess I'll keep looking and searching. I'm sure something will turn up. Just getting a little anxious to get started.
I'm thinking of building a prototype to try out the concept we've discussed and the methods of control. I'm a little hesitant of putting 10,000. into something were not quite sure of. What do you guys think?
Shopteacher,
Ya don't have to stick the wood down the hatch of the tank.
That is what that long thing sticking out the fornt is for. :D :D :D
Shopteacher,
I almost for got.
If ya had enough sense to buy a chevy would wouldn't need water wings. On a chevy you push the secret button and springs come out the bottom and you jump across that little mud puddle.
8) 8) 8)
Den.
I shut down the kiln charge of 4/4 RO today.The half that wasnt under water turned out great!It dried at 53 degress C with no stress and very little degrade.This is #2 comm. lumber so some degrade is going to happen.
Im shutting down the vac kilns in about 2 weeks and taking a much needed break.I guess in 3 months they want to start the kilns back up and dry lumber.I may be back I dont know.
The lumber that was under water is still at 60%MC.We are going to send it to the DH kilns to get it dry.
To the folks who want to build a vac kiln.
A few years ago I helped a guy build a very small vac kiln.We used a home propane tank for the chamber.They are built for pressure.We could only dry a few hundred feet at a time but it worked well.I have to add that we used heating plates.I had a few at the shop that were scrap and we cut them down to fit in the "propane" kiln.
Maybe a propane tank would work for a small vac kiln?
Mike.
Finally, the kids got a bunch of pictures of my R&D kiln at our website.
http://www.pcspecialties.com/index4HC.html
You can see here how some of your heating and vacuum components might look.
Hey Den,
Just went through your revised web site and thought it's looking pretty good. Liked all the kiln pictures, except makes me want one more than I did before looking.
Couldn't find the picture of the one for $99.99 though. :D
How many of those heating plates does it take to fill the smallest kiln with 4/4 wood?
Do you take S&H Green Stamps?
$99.99? You must mean the 300 easy payments of $99.99. :D
For 4/4, I'd put two layers of wood down and then one plate on top. You would need 8 plates.
There's not too many Green Stamp stores around. I'll have to pass. ;D
All,
Where I work they are tossing a AB SLC500 PLC system. It has a HHT, CPU, Input, output modules. If any of you want it, I can grab it now before the scavangers get a chance at it.
I have no Idea if it works.
You pay for actual ground shipping.
First to IM me gets it.
Jason
Jason,
You got any idea if it is any good at all?
I'm in West Michigan, near Kalamazoo. What would it cost from where you are at?
If you can get me a weight, I can check it out. I am interested if it is fairly good shape.
hawby
It powers up but the FLT light is on. Could be as simple as clearing the memory or it could be the cmos battery is dead.
I guess it weighs about 10 lbs in all.
Jason
Jason, find a nice 5' X 12' SS tank and try that offer again. ;D
Fault code 0056h according to the HHT under diag menu.
Jason
QuoteJason, find a nice 5' X 12' SS tank and try that offer again.
How about round milk bulk tanks. They are SS and are dished on the ends. You would have to cut the outside shell off and strip the cooling guts out of it. Then shore up the shell with stainless angle iron around the outside. Dunno hou thick they are though ??? You may end up with SS shrinkwrapped lumber :o
These can be had for a few hundred bux at farm auctions.
Jason
Waaaaaaaaaaayyyyyyyyyyy too thin ::) ::) ;D
re heat exchanger go to a place that parts out wrecked simi tractors get a turbocharger intercooler they usally have a 3-5 inch tube for airflow
The perfect size Vacuum Kiln Chamber drove past the house on Sat. It was on the back of a 2 ton truck, and was haulin PROPANE. ;D ;D
Y'all gotta start hittin them truck salvage yards. There's GOTTA be one available, somewhere. ;D ;D
I could convert the one end to seal in a couple of days. The rest would be up to Den ;) ;) ;D ;D
Fla.-Deadheader.
So whata think?Will one of those ole propane thanks work for a vac chamber?
I have been asking a lot of questions about then lately.
My only concern so far is crossion from inside the chamber while drying Red Oak.
From the sounds of things they can take a lot of pressure.
Dogg.
The BIG ones are about ¼" thick. I do know that to make liquified Propane you have to compress it to 250 pounds pressure and that keeps it liquified, I think. When you release the LP, it turns into a gas with pressure behind it.
There is NO WAY a vacuum would collapse a big propane tank, like folks have in their yards.
In Ar. we used them to make rollers for mashin the rocks back into the wet ground in the springtime. I have cut open probably 8-10. We used them for furnaces, also.
Den,
I have a question? If you pull a 30 torr vacuum on a charge of lumber, but do not add any heat will the wood still dry slowly or would the temperature of the lumber have to to be above the water vapor boiling point of 84 degrees F?
Also is there a reason for starting the drying process at a lower vaccum? Is this so that you do not remove to much of the free water to fast?
Am I reading what Serg is saying right? Since he leaves the humidity in the chamber and removes it as condensate at a set rate per cycle the lumber cannot dry to fast because the surface is allways damp from the humidity in the chamber?
Just trying to wrap my mind around all the information I have been reading and trying to pack into my brain.
Craig
Craig,
If you pulled to 30 Torr and didn't add heat, water would evaporate and the vapor would carry heat away from the wood. The wood would be cooled by evaporation until the vapor pressure of the water in the wood would be below 30 Torr. Then, evaporation would stop.
I start new loads at low pressure for a number of reasons. Low pressure means low boiling point which results in low wood temperature. Also, the first hours of drying are not the fastest so the pump doesn't need to move the maximum amount of vapor. Vac pump capacity diminishes as you reach the low end of the pump curve.
Sergey's kiln works like a superheated steam vac but without the fans. To get convection he has to have air and/or vapor in the chamber. To create circulation, he has to condense vapor at the top/center of the chamber.
Den
Den,
Any recent updates on this project? I've been lurking in the shadows till now. My brother-in law is an Electronics Engineer. I think he could do the electronics for me. ??? :P Tom