Vacuum Chamber

[fstedy]

 ??? : ???  I am considering building a Vaccuum Kiln. A concrete drainage pipe with an ID. of 48" and 20' long with 4" wall thickness is available to me. the walls appear to be very dense and the ends are smooth and could be fitted with doors. does this seem like a viable option in building a vaccuum kiln?

[serg]

fstedy, hi! I can lead(carry out) calculations of durability. I have received diameter of 20 centimeters of one meter, length of 6 meters, thickness of a wall of 10 centimeters is very thick walls of the tanker ???? Sergey

[fstedy]

Sergy
Your dimensions are correct the wall thickness is about 10cm. The concrete seems to be a type we call precast and is  dense in its construction.

[serg]

My computer translation has made ferro-concrete ???? Or metal of 10 centimeters? If it is metal safety factor very big 8)!!

[rerednaw]

i want to advance a small remark for all vac kiln builders :P Before build a vac kiln think where you get drying conditions for this chamber.  it seems to be what whithout payment you can get conditions with drying time like in NYLE DH kiln ...

[Ga_Boy]

Rerednaw,

Please correct me if I am missunderstanding your coimment.  But as I understand your comment you are caliming that a Nyle DH unit can/will produce the same drying times as a vacuum kiln.

As I unerstand the operations of a DH unit it requires 20 to 30 weeks to dry 8/4 plus thickness material. 

Now if I have understood the posts made here about a discontinous vacuum kiln the same material can be dried in about 6 weeks.

Please provide more background on your claims as I am very interested and would like to understand.




Mark

[serg]

Hello! Den, days for drying 12 М3 a pine thickness of 52 mm, width of 500-600 mm, length 6000мм how many is required to time. Initial humidity of 70 % up to residual 6 % in your vacuum chamber? ??? How many it is required to time to your vacuum drying chamber to dry an oak thickness of 52 mm width of 500-700 mm length of 3000 mm from initial humidity of 60 % up to 4 %? ??? Sergey

[rerednaw]

i just want to say what in all of this DYI vac kiln (especially with convectional principle) drying time depend from many factors, like: in which manner you put boards in the stack,  wich temperature and vacum will be in chamber, how could water in the condensor. And all of this factors can to profound effec on the drying time and quality of dryed boards. If somebody think what he can fling board to chamber, and temperature of could water to be of no concern, or it is enoght to pull vacuum so low what water start boiling - is it a big mistake. So if you dont care about factors like i describe bellow - you easy can get drying time and quality like in DH kiln and if somebody like Den or Serg don't help you with all of this stuff you can spend you life combining all these factors in million of experiments And how good help (for free or for money) you get depends ONLY from our guru.

[Den Socling]

How would you make penetrations for vacuum, heating water, cooling water and sensors through concrete?

I think rerednaw is warning that vacuum kilns don't work if they aren't built right. Pulling a vacuum on a piece of wood does not work. My design is much to complicated and expensive for hobbyist. Sergey's design might be doable for the back yard mechanic. My design can dry stuff that would be mighty tough for Sergey's 'convectional principle' but Sergey's design can probably dry what most of you want.

So here we are to help as much as we can.

[Tom_Averwater]

Den,
      Help us .Please keep helping us. :P

[serg]

Hi, Den! WDE, VANICEK, OPEL and your vacuum dryer for what term dry boards  12 М3 a pine thickness of 52 mm, width of 500-600 mm, length 6000мм how many is required to time. Initial humidity of 70 % up to residual 6 % in your vacuum chamber? How many it is required to time to your vacuum drying chamber to dry an oak thickness of 52 mm width of 500-700 mm length of 3000 mm from initial humidity of 60 % up to 4 %? Excuse me for persistence but I 365 days search for the answer to this question! The answer do not give. I want to compare and count economy. If this question is combined, or is not correct once again excuse me. Sergey

[Den Socling]

Hi Sergey,

I've never dried 52mm pine but pine is so easy that the drying rate is limited only by the vacuum system. A quick look at the amount of water that needs to be moved indicates 36 to 48 hours. This is for a system that is designed to dry oak at 0.5% per hour (but I have seen oak drying at 1.5% per hour in these systems).

Those are wide pieces of oak that you specify. They are bound to include knots and such. To prevent drying defects around wood defects, I'd start with 8 or 9 days.

Den

[serg]

Thank Den! I think that drying of an oak of such thickness and humidity for 19-20 days perfectly! All boards dry without a marriage(spoilage)! But what for to me to hasten after hours of drying as many write about it. I wrote on Russian forum about realization of test dryings and to look as the oak of such thickness dries, offers has not acted(arrived).
And now I can tell on economy. One firm has named the price on 12 М3, a vacuum dryer 320 000 .00 $, another 250 000. 00 $ But as the oak will be dried was the answer only from 30 % of initial humidity! When I have asked and where I shall dry from 80 % up to 30 % to me have told buy one more air the chamber for 160 000.00 $ on 60 meters of loading. Only 480 000.00 $. Then I have put the purpose to make a drying complex. I have constructed 3 drying complexes. For such sum 480 000.00 $ in Russia I shall construct 80 vacuum of drying chambers! To dry it is possible 960 meters cubic an oak. I carry the information, that vacuum drying can be cheap but very effective! To apply railway tankers, old. In America money can count. Many write to me letters and speak about that that there are tankers. I give refusal. To carry from Russia it is expensive, and can and is not present. I in Russia to begin this work in other countries, but how? It is necessary for me to know laws to pay taxes, to have the assistant. On these questions I search for the answer. Sergey.

[rerednaw]

I warning about this: Even if you build you vac kiln  right, without drying diagrams it is only pile (heap) of iron  ;)

[fstedy]

Den
I had considered using one of the ends that would be stationary to pipe thru and the other a hinged door. The ends caps would be secured to the concrete pipe with anchors and threaded studs this should be adequate as it will be pulling vacuum.

[GaS]

rerednaw is on the right track.

even if a system is engineered correctly, you still need to know the best techniques to apply with your given system.  once you figure out what technique your equipment can handle, then you need schedules with which your equipment can produce repeatable results.  When working with so many unknowns, you can, as rerednaw said ' spend you life combining all these factors in million of experiments'.

and since everyone who makes a DIY vacuum drying system is going to have different amounts of pretty much any variable you can care to imagine...

'your milage may vary'

A DH kiln is a little easier to engineer and write schedules for, that is for sure.

Rerednaw cut loose the inner pessimist in me...sorry about that.

That all said, a DIY vacuum kiln isn't an impossible undertaking. 

[old3dogg]

I would have to disagree with GaS.
A DIY vac kiln can be possible if you do it right.
Ive help build 2.
Both were made from propane tanks.
A friend and I are working on a vac kiln for the little guy that wont cost more than your house to buy.
I will let you know how things are going as we proceed.
Mike.

[GaS]

I would have to disagree with GaS.
A DIY vac kiln can be possible if you do it right.
Ive help build 2.
Both were made from propane tanks.
A friend and I are working on a vac kiln for the little guy that wont cost more than your house to buy.
I will let you know how things are going as we proceed.
Mike.

I wasn't saying it was impossible.  Just a lot of work ;)

[old3dogg]

You are right.
It is a lot of work but the rewards are well worth it. ;D