Autoclaves

General Composites Discussions Composites Talk
#1

I was talking with a guy today about making us an autoclave.
Size will be 2.5ft X 7ft vessel dimensions. Inside dimensions around 2ft x 5ft useable area.

If anyone is interested in purchasing one of these or wants to know more and keep updated… pm me.

I will have to sell at least one so we can cover the cost of building mine. Price range i’m thinking around $30K - $60K.

More than likely it won’t come with computer/ controlls or software… just the thermocouple connectors, and as many vacuum ports as you need/want. More of a manuall set up.

I am still working on a heat source and fan to circulate the air. Thermocouples will hook up to your tooling

We are still researching although we have a ASTM nuclear certified welder lined up for the job, and we have the pressure vessells.

#2

check powder coat oven type

#3

Somebody is going to build you an autoclave? Please let us know how it turns out, and good luck getting it approved.

There are always plenty for sale, just buy a proper one. I just don’t see this happening.

#4

it would be a pity to drop all this money trying to rig your own autoclave just have it shut down forever and who knows what other fines you can get from doing this.

#5

I don’t mean to discourage you or anything but please be safe and for the first few runs put the autoclave behind a brick wall or three. Good luck though and please post results as you get them!

#6

It won’t be an issue :slight_smile: The pressure vessell is already rated at 3000psi. The professional welding guy is ASTM certified to weld oil and gas lines, and nuclear power plants. The clave will operate at 100psi. The door will have a lock ring and the door itself will be turning-locking like you see on all industrial claves.

Also we are looking for an inert gas substitue for nitrogen because nitrogen he says requires special storage area. Is it seen to run argon in a clave?

#7

To follow that question is helium be used as well and why isn’t regular compressed air used?

#8

because things can burn in a high temperature oxygen rich environment

#9

compressed air can be used but there is a high risk of a fire especially with systems 350+. A 250 cure can be safetly done this way aslong as the sytem is a low exotherm.

#10

Unless you are running a really high temp resin system you won’t be heating over 130C and there shouldn’t be anything going into your autoclave that is that flammable. The most flammable thing we put in is wood which has a ign temp of over 200C. And with good process control exotherming shouldn’t happen.

We have looked into inert gases for our autoclave and it just costs way too much (we need 120m3 of gas per cook), so we invested in good heaters and fans that won’t spark or flame in anyway. As far as I know no one in NZ uses anything but air, some did use N2 but moved away due to cost.

We are currently getting a new autoclave (1.5dia x 12m), which is being made/mod’ed locally by certified welders at a certified company. Once it is done it will be inspected and pressure tested by the NZ regulatory agency. They will use water for the test as it is much safer if there is a leak or flaw. I imagine it would similar in the US, after all someone needs to cert the new one from places like Bondtech. It just won’t be cheap or easy.

#11

In the end, yes, if you get it built by someone else it might not be the best idea, but that normal air compressor tank is holding 120-150psi all the time you work with. Pressure vessels are easy to make, and make safe.
Just check with your local laws on pressure boilers, and go through the steps. If it involves mid-build watching, or just a final pass, don’t see it being a problem. If they don’t like it, they will tell you want they want, they won’t shut it down and say that you can’t do anything with it ever again. They might have guidelines you can follow as you build.

As for the gas…yes, low temp can use air. High temp needs inert, either N2 tanks, or LN2…expensive, but think about it…why would ANYONE use something more expensive without a bloody good reason!

Maintain your equipment, and do checks ALL the time if you go off norm. Seals, gaskets, molds, lines, heater coils, etc…anything wrong, fix it!

#12

Nitrogen doesn’t require a special storage area. You can buy it at any welding supply or compressed gas supplier in small to large tanks. You shouldn’t transport it in a car and have to use a transport collar (or cap), but no worries about having it around.

#13

Maybe not exactly a special storage area, but try finding a good way to store enough nitrogen for several autoclave runs.
I’ll try to get pics next time the nitrogen tanker truck comes by to refill.

And all this talk about pressure vessels seems to be overlooking a simple fact. They don’t normally have a whole side that opens up! Try sealing that at 100+ psi. Inspectors will not be pleased with a homebuilt unit.

#14

@Romoman
Your posts won’t be automatically moderated anymore. The system checks by join date and a few other factors, not on particular user but you’re cleared.

@Tet
First time I’ve seen it happen but your post was moderated automatically since you quoted an already moderated post. Normally moderated posts aren’t visible so it wouldn’t be possible but since you’re an admin you could see it as well as quote it.

Anyhow that’s all from me carry on :slight_smile:

#15

True, a large volume is more of a problem, but a standard tank has a couple thousand PSI in it. Over a 5x3 tank, it should have enough to do a few runs.

From the photos I’ve seen, your autoclaves are a different story.

And making your own autoclave at home sounds crazy to me.

#16

I have been staying out of this one so far, but hey here goes…

I can see the attraction of making your own kit, hell I have in the past made a lot of bits of kit for my shop, and I plan on making some more kit real soon. If you plan well and get it all worked out before you start then you can make excellent quality stuff that will fit your needs better than much of the equipment that is on the market, planning ahead is the key and not rushing the building.

However I do think that building an autoclave maybe a little out of reach for most if not all of us on here, very good luck to you fastrr if you do go ahead, but please be careful, do your sums with regard the pressures on the components and get someone else (a suitably qualified engineer) to check your calculations also.
The toughest part of the build will be working out the door opening and sealing as that will be a lot of pressure acting on a part that is designed to move, will have force trying to make it move, whilst at the same time you dont want it to move!

Remember that whilst your planned autoclave autoclave may ‘only’ be opperating at something like 10 bar (149psi), that is a peasurement of force on a very small area, what is the surface area of the door on your planned clave? something like 2 and a half foot isnt it? so how many square inches in 2 and a half square foot?
If it were a square door that would be 900 square inches. Now multiply that by you 149PSI.
900 x 149 =134,100 pounds of pressure acting on that door!
Written another way that is 53,640 pounds per square foot (PSF)

Not being negitive fastrr just trying to be subjective. Please keep posting on this I would be very interested to see any results.

#17

Be sure to proof load your autoclave the first time to both strengthen it and verify it’s integrity.

#18

Pressure pots for paint, a good one can do 100psi, and the entire one side is only clamped. OBVIOUSLY not meant for high temps, but replace the seal for whatever temp…and…well, you have a certified pressure vessel.

#19

Whatever you do, be careful, follow the rules, and follow your common sense.

As for nitrogen: Would a N2 generator be a possibility? These can be run from a compressor. I have no personal experience with it, but we think about buying one for filling up the empty space above our products (polyester, gelcoat, acrylic resin). Not 100% N2, but getting close.

Getting a 2nd hand autoclave can be a very viable option. Periferal machinery can be crap, but replacing or repairing that is easy compared to the working vessel.
Also keep in mind that very probably a blow-off valve is needed, and you do not want the exhaust in your shop.

One of my customers converted an autoclave to work at 400 degrees C (not F !!!) and 20 bars. An excersize which cost him a lot of money and effort.

About pressure pots: Be careful, with lots of heat metal gets weaker. keep things well within limits.

#20

Pressure pots are much smaller though meaning there’s way less stress. Double the diameter of the lid and you quadruple the force and triple the volume which means more energy if that autoclave lets loose.

What is the size of the autoclave you’re trying to make?