Vacuume/Pressure pot set up complete!

[ElMostro]

OK folks, here is my set up. HF pressure pot with a robinair 6 CFM pump. Thanks to all on the casting forum, I got plenty of ideas and set-up examples from there. While putting this tigether I learned "Flair", NIP and MIP are and how the threads are different etc. [:I] Anyway, I tested it on vacuume and almost made it to 30" of vacuume (see pic) it held at the same vacuume for 24 hours so I guess it seals well. The pressure though, I tested it up to 80 PSI (the pressure pot max) and within 4 hours it went to 70 PSI and held for a while. At the 24 hour mark it was down to 60 PSI...so something is leaking. Overall I am pretty satisfied, now once I pay Gadgett for the molds and get them I am all set.[]

 

[gketell]

If it seals on vacuum and not on pressure I would check the lid seal and any gauges/fittings that are not on the vacuum side of the house.

Looks really good!

GK

 

[Nolan]

Level of seal between 80 psi pressure and 30" vacuum is not even close to same affect on seal. Basically 30.00" or true vacuum is only -14.70 psi. So your leak test really test your system almost 15 psi in one direction and then 80 psi in the other. I think I got that right []

 

[ElMostro]

Nolan, my head hurts [:I]
So you are saying that if I get down to 30" vac that is equal to 14.50 PSI? So if I am looking to stabalize blanks then it is better to use pressure instead of vac in order to acheive maximum penetration of stabalizing solution? I will be using the plexi-acetone mix to stabalize under pressure, do I still need to be concerned about the acetone vapors harming the pot gasket? Like I said; my head hurts and it's not the fumes...[?]

 

[Nolan]

Well my pressure pot is still sitting in pieces so I havent done any yet either. As far as pressure verses vacuum so of the other guys should chim in as I not expert in that (heck I dont know that I am an expert in anything[]) I know each has a different affect on the air and whats in it. IE water will boil at 170 in 29" of vacuum instead of 215 or whatever it is in standard atomospere. The same thing wont happen under pressure thats why you have a radiator cap- to raise the boiling point. I think peronally each medium is to be handled different. Like the stuff I was looking into recomends vacuum. I even think some guys were doing both - Like pressure for a while then pulling a vaccuum on it. Be carefull when pulling vacuum on your wood as any moisture in the wood will cause the solution to boil (not hot boil remember the boiling point of water in a vacuum.) Just looks like boiling as the water turns to vapor

 

[gketell]

The way I plan to do it is to pull a vacuum and release it, do that a few times to try to have the wood "pull" the solution in as far as possible on its own. Then I will apply pressure after to try to force the solution even further in. We'll see how well this works.

GK

 

[armyturner]

You are doing much better than I am. On my HF pot the pressure relief valve pops at 40 psi. I have "fixed it" to obtain more pressure, but the seal starts leaking at about 45 psi. The seal looks to be in good shape but I can't seen to make it hold. It leaks down completely in an hour or so.

 

[gketell]

Oh yah, to find the leak use the "gas company" test. Get a squirt bottle and fill it up with a soap and water mix then squirt all your joints when the system is under pressure. Any leakes will blow bubbles for you.

GK

 

[ElMostro]

Jeremy,
Mine would also do that and about 40 PSI so I decided to remove it. As a precaution I set the regulator on the pot not to exeed 75 PSI and also pay attention to my compressor's regulator not to exeed 80 PSI. If you decide to remove it have in mind that most of the fittings when installed in the factory were actually glued in place so it it a bit hard to remove the fitings but they do come off. I recommend you use the appropriate size wrench and not a pipe or adjustable wrench so that you do not round off the bolt. Good luck.

 

[Fred]

Many say their "solutions" boil. What in fact is happening is that the solvents are being removed most rapidly and thus the effect appears like boiling. All fluids have a boiling point - and that boiling point is rapidly reduced with a vaccum. Solvents such as MEK instantly are 'boiling' even with a mild vaccum introduced. I would also recommend that ALL of us pay v e r y close attention to the warning label of the manufacturer of any pressure pot. This posted WARNING is there for a purpose and that is to caution us about the explosion that can occur whenever the recommended pressure is exceeded. These things can - and will - explode in our faces if we push the envelope and exceed the pressure rating. A vacuum will 'implode' with possible devestating results as well ... so be careful with the pressures or lack thereof. []