Purchased tank to make into vacuum kiln

[boardwalker]

Den

What should the air temperature inside the kiln be? If I'm running 180 degree water through my heat exchanger will the air temp. get to high before the wood gets up to it temp setpoint?

Can you pull to many cfm of air by using to big a pump?  I have a lead on a nash or elmo/ 2bv2 070 or L200 that can pull up to 60 cfm but as far as I can tell pulls about 35cfm at 50 torr. It uses a 4.5 hp motor but it will take a long time to equal the cost savings in electicity that a smaller 3 hp would give me.

Thank you
Craig

[Den Socling]

Will,
I know nothing of milk storage tanks. Jason?

Craig,
Safe temperature depends on humidity. Hot dry air will damage your wood if the wood is wet. Hot humid air will not damage the wood unless it has already seen some damage. I'm guessing that you would want humidity high with air temperature around 115-120 while there is free water in the wood. However, in steaming experiments, I have heated green wood like cherry and walnut to 140+ with high humidity and then pulled almost all free water out with one vacuum cycle in a few hours. This put a few small end checks in 8/4 but the process seems very forgiving if you are working with a porous species.

The vac pump can't be too big. It will turn on and off with wood temperature. The bigger the pump, the less time it will be running.
Den

[boardwalker]

Den

How do you keep the humidity high if you are sucking the moisture and air out of the chamber with each cycle? Do we need to include so sort of humidity sensor in the control circuit, or can the vacuum pump not remove all the humidity before the temperature of the wood drops back below the set point?

Thank you
Craig

[Den Socling]

When you are heating with no vac, humidity will rise in the closed container. When you pull vac, the atmosphere will remain humid, though less, from water boiling out of the wood.

[Jason_WI]

Wiam,

Bulk tanks normally don't see the vacuum of the milk system. This is uaually isolated at the pump that transfers the milk from the receiver to the tank. I am pretty sure if you pulled 28-29 "Hg that the tank would suck flat and shrinkwrap your load of  lumber in stainless steel.

Jason

[wiam]

Jason there was no reciever.  The vacum line connected to the tank through a moisture trap and the milk line went into the tank.  No transfer pump.  I realize that the tank has only had about 15" on it but I was just thinking.

Will

[Den Socling]

What happened to this thread? I thought we were going to carry through this time. I've built two vac kilns since it was started.  ;)

[serg]

Den hi!
This string good. Should will be filled with new technologies of vacuum drying.
Have started the vacuum drying chamber of 30 m3.
Has checked up Vacuumterm look result under the reference.
Sergey.

http: // trans.voila.fr%20www.vacuums.ru%2Findex .php%3Fid%3D7|child_id%3D29

[serg]

To look this reference.
Sergey.

http: // www.vacuums.ru/index.php? id=0*nid=11*child_id=18

www.newkilns.com

[boardwalker]

Den,

I have been working 10 to 15 hours a day 6 days a week  so I haven't had time to think about this project for the last month. I thought I had some vacuum pumps purchased, but when the guy went to ship them he found that the pumps were cracked. I haven't been able to locate another used pump for a decent price so I may be back to buying one from you. After the first of december things should slow down so I can get back on the kiln.

Craig

[boardwalker]

Den,

What is a Sihi LOHY2704 vacuum pump? It's being advertised as a liquid ring vacuum pump, but I cann't find any information on Sihi's web site.

Craig

[TexasTimbers]

What happened to this thread? I thought we were going to carry through this time. I've built two vac kilns since it was started. ;)

I can't build one right now too many irons in still, but I can ask stupid questions. I have four 250 gallon propane tanks I could weld end to end making a chamber (rough guess) 36" x 18 feet long.

It would not make for many BF but it would be good for high value specialty stuff below the 8/4 range wouldn't it?

[Den Socling]

Craig,

I searched with Google and found this.
Pas de photo disponible
Inventarnummer :    97145
Kapazität :    26 
Kategorie :    Pump / Vacuum
Beschreibung :
26 cfm @ 25"Hg, Sihi 316SS vac pump. SN 3160407, Mdl #LOHY2704. Packing gland. Direct driven by 3 HP, 3/60/230/460 volt, 1735 rpm motor, UL label. 1 1/2" inlet x 1 1/2" outlet. Base mtd.

[Hier klicken oder mehr Informationen anfordern]

It looks like a nice little pump.

kevjay and all,

Lets see how Craig's system works and what kind of snags might be encountered by someone new to building vac kilns. And there is nothing wrong with joining tanks to make a longer chamber.

Den

[boardwalker]

Den

Will this pump pull low enough vacuum and enough cfm's? The specs are quite abit lower than the pump you were talking about originally.

Craig

[Den Socling]

Craig,
If it is 2-stage, it has the vacuum capacity. Little pumps don't have the cross-over pipe between stages and are difficult to distinguish from single stage. I can't verify from the pictures that it is two stage. As far as CFM is concerned, if the pump is low in pumping capacity, it will take you longer to use the heat that built up during the heating stage. Drying will take longer but the wood won't suffer. Also, SS pumps usually have lower ratings than the same pump in another construction.

I'm going to be drying 18" x 18" Doug fir next week so I will be experimenting with control ideas that I will give to you.
Den

[boardwalker]

Den

I got the pump and a motor. I fust need to buy a flex coupling to put it together. The pump is a new punp that has been sitting  on the shelf for how knows how long. Sihi no longer makes this model. I did manage to get some specs but the fax was so bad I could hardly read it. Will have to have them send it again. From what I could make out the pump will pull around 20 cfm at 50 torr. The pump appears to have some loose rust flakes on the inside from being stored for so long. Is this something I should be worried about or can I just rinse it out good and start it up.

I also have a circulator pump and loop controlers purchased. Have a couple of used water heaters that I think I can make work. If not I will have to buy one. Need to purchase my valves, fans, and  radiant heat tubes. Then I just need some time to start putting everything together which will hopefully happen soon.

Craig

[Den Socling]

Craig,

Common construction for vacuum pumps uses cast iron cases with bronze or stainless steel impellers. A little rust doesn't hurt anything. It is often necessary to break them loose before start-up. Then, if they are ever left unused, dump some antifreeze into the case.

Can you program the loop controllers for discontinuous vacuum drying? I was working with 18" thick Douglas fir last week and discovered that you can get the core of porous wood under 28% pretty quick but I then I screwed up the process!

Den

[Dave Shepard]

I am very intrigued by vac drying, even if I don't build one, although I will try, I would love to understand them better. I went to your website (Den), and noticed the kiln chambers were square. Is it simply a matter of putting the ribs on the outside to strengthen the chamber? If so, I could build a small chamber easily. I have a contact at an excellent machine shop that can bend up any size or shape rib I would need. It appears that the chamber is built similiar to a dump truck body, only it would work in reverse. I will be rereading old threads to try and figure out what parts make up a vac kiln. So far I know we need heat and vacuum.  :D If I want to go automated, what do I need to control the kiln, a PLC? Just thinking about vacuum, the ski area I used to work at has seven 1200CFM Fuller rotary vane compressors, which can also be used to make vacuum. That would dry a lot of wood. :D Can you run 2100HP of electric motors off of a phase converter? ;)


Dave

[boardwalker]

Den,

I have not tried to program the controllers yet but we use similar ones at work for controlling heating cycles in our ovens.

What happened to your doug fir that you were drying? That is some really thick wood.

Craig

[Den Socling]

I like rectangular chambers for a number of reasons but cylinders are easier to find. A carbon steel support frame over a stainless steel chamber is the design.

PLC's used to be finicky and I preferred loop controllers. Now, however, PLC's are dummy-friendly and we get along.  :D

The Doug fir turned into a very interesting experiment. It verified some of what I guessed and some new ideas developed. It appears that 18" squares can be dried very quickly and easily but I can't say anything about the details at this point. The report is being reviewed by the patent guys. The basics are as I always said about discontinuous vac. Monitor the core temperature of the wood and use that temperature to control chamber pressure.

[Den Socling]

 I thought I knew the exact settings to get those 18" squares dry and so I expected some 12" squares of Douglas fir to be easy. The experiment failed miserably!  :( Back to the drawing board. But I still think discontinuous vac should work well with most species cut to lumber.

[boardwalker]

Den

If I run a condenser on the vacuum intake could the seal water be used for watering cattle or would there be to many contaminates from the drying process?

[Den Socling]

Craig,

Only a CSI lab could say for sure. But why not cool the water and use it for seal water again?

Den

[boardwalker]

Den

I guess I am having a hard time finding a cooling tower that doesn't cost alot.

[boardwalker]

Den

Would one like this work? http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=290067823991&fromMakeTrack=true

Can you bring the water temperature back down to 60 degrees with a cooling tower?