Purchased tank to make into vacuum kiln

boardwalker · October 15, 2006, 07:10:28 PM

I am hoping that Den will help us get this dis- continuous vacuum kiln topic going so that I can try drying some wood in this tank. Den I was here when this topic got started and tried to participate in the discussions, but could not try building one back then. Back then I was bowl blanks and more, but I losted my password and had to sign up again. I printed and reread all the posts that I could find. I understand the concept and would appreciate any help you could give me. The straight sides on the tank are 11' 6" and the inside dia. is 40". I have been having a hard time finding a 2 hp 2 stage liquid ring pump. I can find lots of larger pumps and smaller single stage pumps.

beenthere · October 15, 2006, 07:20:41 PM

boardwalker
Is that the same technique use by Den and his company? If so, seems it would be tough for a guy building and selling vacuum kilns to help someone build their own. Maybe this isn't the case, but seems it might be a problem.
Doesn't stop others from filling in the blanks, but there are'nt too many experts in the area, me thinks.

Don't get me wrong, as I 'd like to see you build one and test it out. May or may not be less expensive than buying one. :

boardwalker · October 15, 2006, 07:32:01 PM

photos hopefully

boardwalker · October 15, 2006, 07:38:53 PM

beenthere

This is a different concept than what Den uses. Den uses continuous vacuum. Den was trying to help us get a dis-continuous vacuum kiln built awhile back and I am hoping that he is still interested in the project.

beenthere · October 15, 2006, 07:53:21 PM

Gotcha. Thanks for the clarification.
That cylinder looks like a good start.

Den Socling · October 16, 2006, 10:32:52 AM

Surely I will be glad to help. I haven't had much free time lately but this design can be reasonably simple. Remember Tyler? the guy who dried a table top for Jerry Seinfeld in a vac kiln made with a plastic bag? He wants to build a discontinuous vac also. But I just got done unloading a couple mbf of 12/4 table tops to dry for him. He's behind schedule in building his kiln. :D

Your chamber does look like a good start. Got a welder to add a couple nipples? When you are done with welding, you may want to coat the inside will coal tar epoxy.

boardwalker · October 16, 2006, 05:46:09 PM

Den

How many cords do I need to run through the tank wall? I have a 2" threaded coupling on the back end cap and 3 more across the top plus 4 or 5 1/2" to 3/4" on the front end cap. I could just put reducers in these and save having to weld on the tank any more. I do have a welder and can add anything that you think I need . I work in maintance at a large plant and do this type of stuff daily. I just don't know much about vacuum and drying other than what I have been able to gather from you.

Would it be possible to buy a vaccum pump through you or do you know of a source where I can get a used one. I have a 2 hp motor so all I would need is the pump. From what I have read I think that you were saying I need to use a 2 stage pump to pull enough vacuum.

Where would you get the coal tar epoxy?

Thanks
Craig

Den Socling · October 16, 2006, 07:21:46 PM

You will need to get heating water in and out. For a chamber that size, 1-1/4" would do. You need to get power for circulating fan(s) in. You need to get some tiny wires for RTD's into the wood. The idea is to heat with no vacuum by circulating warm air. Circulating evenly is the hard part. Heat until the wood is sufficiently warm and then pull vac until you have used the heat. Then repeat the process.

The little 1-1/2HP 2-stage pumps from WoodMizers would work. We sell SIHI's but I have new ones, only.

Coal tar epoxy is available at many suppliers, like Grainger.

Furby · October 16, 2006, 08:50:43 PM

Coal tar epoxy
What is it and what is it's use?

Den Socling · October 16, 2006, 09:21:15 PM

I'm not a chemist but a fab shop told me they use it in liquid storage tanks. I've tried it in a couple carbon steel chambers it it seems to work well. Not as well as stainless but, if you have a carbon steel chamber, I recommend it.

boardwalker · October 16, 2006, 09:49:15 PM

Den

What size hole do I need for the vacuum pump, and do I need a whole in the bottom of the tank to drain condensation or is all the moisture taken out through the condenser between tank and the vacuum pump? Also, does it matter where the hole for the vacuum is located?

What would a new pump from you cost? Do you know where to locate any of the Wood-mizer pumps?

I was also wondering if I should insulate the outside of my tank to keep condensation from forming on the walls and rusting it out? Just remembering that Serg's system used insulation and didn't have rust problems.

I was thinking of using a fan at each end with baffles and the heat exchanger down one side of the kiln like Vacutherm used. Is this a good idea?

Thanks
Craig

Tom · October 16, 2006, 11:35:58 PM

I wonder what that "paint on" pickup bed insert stuff would do inside of a kiln?

Den Socling · October 17, 2006, 10:12:21 AM

Craig,

A 1-1/4" NPT nipple would be a good size for a vacuum connection. You will need a nipple about the same size in the floor because water will always be condensing on the chamber, even with insulation. I don't think the location of the vacuum port would make any difference. The floor drain can double as air-bleed back into the chamber.

A little SIHI vacuum pump in bronze mounted with a motor cost around $1500. The size of the vacuum pump isn't as critical with discontinuous as with continuous vacuum drying.

Sergey's chambers don't rust because he has heating water pipes on the chamber. Condensation occurs at a condenser at the ceiling.

That air circulation could work but a lot of attempts have been made over the years to get perfectly even circulation. It is apparently difficult.

From what I'm told, coal tar epoxy is 'self healing'. If a tank flexes, it does not crack and break lose. I bet the truck bed stuff works the same way.

Den

woodhick · October 18, 2006, 03:21:36 PM

boardwalker, I am watching this thread close as I may want to build one myself. What was your tank used for in its previous life? It looks to have some serious corrosion or rust pitting on the side. Do you think it will hold up under vacum? Good luck and I hope to be right behind you with a kiln of my own.

boardwalker · October 18, 2006, 07:11:46 PM

Den,

How big is the vacuum pump that you quoted the price on? I was wandering because in the future if this works I was thinking of possibly running 2 kilns side by side or possibly a larger one.

I thinking that I need to get a pump purchased so that after I get finished welding the rest of the fittings on the tank I can run a vacuum test to see if I have any small pin holes that need to be patched before I paint the inside of the tank.

I was thinking the other night about the air circulation system and I thought that another way would be to use a fan wall similar to a dehumidification kiln using a row of tangential blowers right in the top of the cylinder with aluminum finned tubes all along the front for the heat exchanger. These fans are low cost from the surplus center and I think that by having them spread all the way across the top and the bottom of the kiln charge blocked off so that the air would have to go through the stack your air flow would be spread about as evenly as possible.

How many cfm do you think it would take to move enough air through the stack. The fans are 7" to 10" long by 3" to 4" square. I figured about one per foot for a total of ten or eleven. Surplus Center has these from 29 cfm to 90 cfm $8 to $20 each. The largest only pulls .56 amps/110 volts the small ones pull .10amps/110volts.

boardwalker · October 18, 2006, 07:20:01 PM

Woodhick

I think it was a anhydrous tank like they use to apply ammonia in the gound behind a planter. I think they removed the wheels and letf it on the ground for awhile before they decided to make it into a vacuum chamber or whatever they had in mind. I bought it for $25 at an auction. The tank sides look to be at least 5/16" so I don't thinkthe rust will be a problem.

Den Socling · October 20, 2006, 08:21:24 AM

Craig,

That SIHI is 3HP, 30CFM at 49 Torr.

One of Maspel's (VacuTherm) designs used a wall of fans but, incredibly, mounted the motors outside to avoid the harsh environment.

I wouldn't think that high velocity is needed. The air isn't carrying away water. It's delivering heat.

$25!! That tank would be worth more than that as scrap metal.

Den

Jason_WI · October 20, 2006, 11:41:46 PM

A vane vac pump from a milking system would work. Universal dairy systems uses this kind of pump. Dont use a figure 8 vac pump(boumatic) as these will lock up with water vapor. My dad bought a 7.5 hp pump for 200 bux. It draws 100 cfm ad can pull to at least 29 " mercury unregulated.

The only thing bad with these pumps it that they require a oil drip for the bearings. If you can look for one with a oil reclaimer system.

With 10 dollar milk these pumps shouldn't be hard to find.

Jason

boardwalker · October 23, 2006, 01:28:10 PM

Den

How many btu water heater do I need to heat with? Would a 50 or 60 gallon propane water heater keep up with the demand?

I guess I'm trying to decide between 10 29 cfm fans or 10 50 cfm fans that I could possibly regulate with a ceiling fan speed control.

What series Worcester valves were you using with the Belimo actuators?

Is it nesessary to use a check valve on the vacuum line if this is a dis-continuous system?

Den Socling · October 25, 2006, 08:18:46 AM

Craig,

Sorry that I don't answer more quickly but I have been busy. I'm here now because a shipping container is late.

Depending on species, wood can have 3 to 5 gallons of water per 1% per 1000 board feet. It takes about 8114 BTU's to vaporize a gallon. So, estimate the amount of wood you will have in the kiln and you will be able to estimate total BTU's.

Belimo supplies actuators on valves so there is no messing around with mounting and coupling.

No check valve is required. I suggest that you operate manually until we see what kind of bugs are in the system. If it dries as planned, everything can be automated.

Den

boardwalker · October 25, 2006, 09:39:46 AM

Can someone check me on my math?

My kiln will hold about 468 bdft so I am going to use 500 bdft to figure how many btu's of heat I need.

Say we need to remove 60% moisture.

I'm figuring this for 2" thick lumber so say that it takes 14 days to remove the 60%.

60% / 14 days = 4.28% per day

Assuming that we are heating for 12 hrs and vacumming for the other 12 that leaves us 12 hrs to vaporize 4.28% moisture.

4.28% / 12 hrs = .35% moisture per hr of heating

Assuming on the high side 2.5 gal water per 500 bdft per 1% moisture

.35% x 2.5 gal = .9 gal of water per hr

Den says it takes 8114 btu's to vaporize 1 gal

8114 x .9 = 7303 btu's per hr

So if I calculated everything right a 30,000 btu water heater will be more than enough.

Thank you
Craig

Den Socling · October 25, 2006, 06:25:35 PM

more than enough, as you say. Even when you add losses. Unless your chamber is sitting in Alaska. :D

boardwalker · October 25, 2006, 06:41:18 PM

Den

Is my figure of 14 days for 8/4" within range of this kiln?

Den Socling · October 25, 2006, 07:15:02 PM

most species yes, some no

wiam · October 25, 2006, 08:52:59 PM

I am wondering if I could do this on a smaller scale. I have an old Zero brand milk bulk tank. It is 350 gallon capacity. It is a vacum tank. Meaning that the tank was under vacum when milking the cows. My question; would running hot water through the freon lines work for the heat?

Will