Pressure Pot Questions

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Notnate

Member
Joined
Apr 15, 2014
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85
Location
Sioux City, IA
Hi,

At the risk of asking a question again that I may have missed in my search. I have been considering buying the HF pressure pot and some additional supplies to use it as a vacuum tank as well. Here are the extra parts I am looking at:

ProVac Vacuum chamber lid assembly

3 CFM Single-stage Rotary Vane Vacuum Pump

So in order to know if this idea would work I was wondering if anyone had tried this setup before? Is the HF pot opening the right size (10") for the lid assembly? And is that vacuum going to be good enough for stabilization?

I did the math on the vacuum and according to their specs it should pull nearly 30 inches of mercury. The reviews on it are awful iffy though.

The lid I'm sure will work provided the opening on the pot is large enough and not so sharp as to cut the gasket material. I could even alter the lid some with thicker gasket even if it is, so long as the lid will fit.

Thanks in advance for any thoughts.
 
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I believe it will work, How ever if you are so inclined to build your lid you can come close to cutting the cost in half ?
 
The pump should be fine, I would think. It's probably better than the junky one that I've been using for years. I've never seen anything like that lid before. I kind of want one.
 
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HF gives the dimensions of their tank as 9.5" in diameter. I suspect that this is the internal size which would make that lid assembly about perfectly sized.
 
If you don't need to see in the pot when vacuuming then you can use the pot lid as in the instructions in the library.
Lin
 
That is quite a bit for a lid. I would save your money, use the lid supplied, or plexi, and invest in a better pump. Any pump costing $46 is bound to make me nervous....no matter what the spec's say.
 
Thanks for all the C&C!

I kinda want to see in the tank for when i am stabilizing so i can see when the bubbles stop.

I thought about using the build in the library, but costing that out it was almost as much in piping hardware as the lid i'm looking at. I could get plexi and cut it myself i suppose, it would require some jig making and the gasket material and i suppose it would be cheaper, but time consuming and i would have to buy the piping, hose, valve, and vacuum gauge, not to mention the tap for the threads.. i will have to think on that one.

as far as the pump is concerned, it is my understanding that once gotten down to the pressure i desire i can valve it off and wait for the bubble to recede? if that's the case i would only be running the pump once in a great while. would i really need a more expensive pump for that? if theres a better one out there can anyone suggest it please?
 
Edward, then i wouldn't have the pressure pot. The HF pot is on sale this month for 75 for inside track club members plus this lid and pump i could have a full set up for only $260ish.
 
You didn't miss the search...you didn't search at all. Pots are easy and simple...if you want to blow your face off...whatever. Come on...do the research like you would do for a car or a house; unless you feel it's not that important? Asking people what's already been asked?
 
30 more dollars and you have to separate systems

Seems like for a mere 30 more dollars you would get a pressure pot and a vacuum chamber, plus the lid would fit for sure on the chamber. You know you cannot use the lid on the pressure pot to pressurize right. IMHO you would be better off getting the two different vessels then you could do vac and pressure at the same time on different woods or PR or Alumilite.

Notnate said:
Edward, then i wouldn't have the pressure pot. The HF pot is on sale this month for 75 for inside track club members plus this lid and pump i could have a full set up for only $260ish.
Click to expand...
 
As much as I think that the lid itself is pretty cool, I agree with Edward. For not that much more money you get them both.
 
Jim Burr said:
You didn't miss the search...you didn't search at all. Pots are easy and simple...if you want to blow your face off...whatever. Come on...do the research like you would do for a car or a house; unless you feel it's not that important? Asking people what's already been asked?
Click to expand...

Two thoughts:
  1. I am pretty active in the forum and I can't remember any discussions about that lid. A conversation regarding whether that lid fits a specific seller's pot is pretty darn unlikely, I suspect. Therefore, I'm thinking that a search on that issue would not be very effective. Right off the top of my head, I'm not even sure what terms I would use to separate the wheat from the chaff.
  2. I've never heard of anyone blowing their face off with a vacuum vessel while making pen blanks.
 
Notnate said:
Thanks for all the C&C!
as far as the pump is concerned, it is my understanding that once gotten down to the pressure i desire i can valve it off and wait for the bubble to recede?
Click to expand...

Based on extensive testing, this is incorrect. As soon as you valve it off, the pull on the air stops and the pressures begin to equalize. Using a clear chamber you can really see this. I can pull a chamber down to full vac and isolate it. As as soon as I do, the bubbles will stop flowing in very short order. Then, as soon as I open the valve back up, it will start bubbling all over again. If it is bubbling, air is coming out of the wood. If it is not bubbling, air is NOT coming out of the wood. The objective with vacuum stabilizing is to get as much air out of the wood as possible, thus allowing resin back in.

My recommendation has always been to keep the pump running until the bubbles stop. You WILL get better results. I have testing data to back up this claim. Now, with that pump, I can not say how it would hold up to continuous run. However, oil filled rotary vane pumps are typically intended to be run continuously with no issues. Their intended purpose is to pull down HVAC and refrigeration systems. It is not uncommon for an HVAC tech to attach a vacuum pump to a large AC system and allow it to run 24-48 hours straight! Then again, an HVAC tech is not going to use a $46 vacuum pump.

I can say, however, that an inexpensive Robinair 15310 ($115 +/- on Amazon) will run like this. I have had one for a number of years now. I use it when I go to shows or do demonstrations. I also use mine for my CNC vacuum table system when I am cutting parts. I have allowed it to run 8+ hrs straight with no issues.
 
MesquiteMan said:
Notnate said:
Thanks for all the C&C!
as far as the pump is concerned, it is my understanding that once gotten down to the pressure i desire i can valve it off and wait for the bubble to recede?
Click to expand...

Based on extensive testing, this is incorrect. As soon as you valve it off, the pull on the air stops and the pressures begin to equalize. Using a clear chamber you can really see this. I can pull a chamber down to full vac and isolate it. As as soon as I do, the bubbles will stop flowing in very short order. Then, as soon as I open the valve back up, it will start bubbling all over again. If it is bubbling, air is coming out of the wood. If it is not bubbling, air is NOT coming out of the wood. The objective with vacuum stabilizing is to get as much air out of the wood as possible, thus allowing resin back in.

My recommendation has always been to keep the pump running until the bubbles stop. You WILL get better results. I have testing data to back up this claim. Now, with that pump, I can not say how it would hold up to continuous run. However, oil filled rotary vane pumps are typically intended to be run continuously with no issues. Their intended purpose is to pull down HVAC and refrigeration systems. It is not uncommon for an HVAC tech to attach a vacuum pump to a large AC system and allow it to run 24-48 hours straight! Then again, an HVAC tech is not going to use a $46 vacuum pump.

I can say, however, that an inexpensive Robinair 15310 ($115 +/- on Amazon) will run like this. I have had one for a number of years now. I use it when I go to shows or do demonstrations. I also use mine for my CNC vacuum table system when I am cutting parts. I have allowed it to run 8+ hrs straight with no issues.
Click to expand...

This is an interesting statement, Curtis.

When you reach "full vacuum" at 27 inches or so, as I understood your demo, you have achieved your goal. Continuing to run the pump will continue to move the atmosphere, I guess, but it will NOT change the vacuum, will it? So, the bubbles could be a result of movement around the chamber. They certainly do NOT indicate any additional pressure on the wood, so why would you conclude that there is a benefit?

Truly interested in learning, here. I don't pretend to know the answers, but I would like to understand the logic.
 
Been there!!!! No hurry!!

Actually, for posterity, it may be better to start a new thread.
 
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Ed, achieving full vacuum inside the chamber is different than achieving full vacuum inside the wood. The flow out of the wood is slower than the pump will remove the air from the chamber and it takes a good while to remove the air. If bubbles are coming out of the wood, you have not achieved the same level of vacuum inside the wood as you have in the surrounding chamber. If you close the valve and hold vac, you have stopped the movement of air out of the chamber. However, the movement of air from the blank continues for a short period of time until the pressure equalize, then the air stops. The vacuum level IS lower but you will not detect it on a normal inHg gauge. Hook up a micron gauge and it is not uncommon to see a 1,000 micron drop in vacuum which will really not move a typical gauge. This is especially true of the typical inexpensive vacuum gauges. Most of those have an accuracy of 3,2,3. This means it is +/- 3% on first third, 2% on middle third, and 3% on top third!

You can really see this in a clear vacuum chamber. Close the valve and hold vac and the bubbles coming from the wood quickly slow down and even stop. At that point, air has stopped moving from the blank. Oven the valve back up with full vacuum and it will start bubbling all over again, sometimes looking like it does in the beginning.

Remember, any air in the wood is reducing the amount of resin you can get back into the wood. Also remember that vacuum does NOT get much resin into the wood. Vacuum creates a lower pressure inside the wood and the chamber. When you release the vacuum, the lower pressure inside the wood tries to equalize but since it is submerged, it can only suck in resin.

Also, full vacuum varies based on elevation above sea level. At sea level it is 29.92" Hg. For every 1,000 ASL, is it approximately 1" less. Based on that, 27" as you mentioned would only be full vac at approximately 3,000' ASL.
 
Curtis, Thanks so much for your information! I was actually hoping you would be one who responded to this. I will definitely take all of that into consideration!

Edward and Steve, thanks for your input. I am tempted to say that a dual purpose tool in my tiny shop saves me much needed room, but I also see your point. I never intended to use the plexi lid for pressure though as you really get no benefit for being able to see while casting. That said, for that price i would rather have one of Curtis' vacuum chambers. Just how long is that waiting list now Curtis? lol

Thanks for all the input everyone. I will be sure to tell the wife it is all you guys' fault when i spend the extra money for better quality tools :D.

Oh and I am looking forward to an answer to Dicks question. That one is on sale this month for $150 and with the 20% off coupon that would be a nice deal too.
 
Nathan,

I'll probably take a beating again, but you can try this: http://www.penturners.org/forum/f43/my-$10-stabilizing-chamber-124861/

It is by far not the quality if Curtis's chambers, but might keep you happy until yours arrives!

Also, I have a set of micron gauges on my pump. Curtis is correct about a change in pressure being seen on these vs a cheap gauge. When I'm working to remove all of the bubbles, I still see quite a bit of drop on these gauges, even with very little bubbles remaining. I may try and you tube it the next time I stabilize...will keep you posted.
 
jeweler53 said:
Has anyone tested the HF type of pot as a vacuum chamber? I am thinking about doing just this, but don't want to destroy it (or anything else) in the process.
Click to expand...

Many people have used their HF pot as a vacuum chamber. In fact, the tutorial in the library shows you how to set one up for vacuum or pressure. The negative to using a paint pot for vacuum is basically that you can't see inside unless you use a clear lid.
 
sbell111 said:
jeweler53 said:
Has anyone tested the HF type of pot as a vacuum chamber? I am thinking about doing just this, but don't want to destroy it (or anything else) in the process.
Click to expand...

Many people have used their HF pot as a vacuum chamber. In fact, the tutorial in the library shows you how to set one up for vacuum or pressure. The negative to using a paint pot for vacuum is basically that you can't see inside unless you use a clear lid.
Click to expand...

Thanks! (great tutorial!_)
 
Oh! Dick was talking about the HF pot not the HF pump. Oops!

Anyway thanks for all of the great advice! I finally decided what I was going to do based on all of the great info provided.
Here is what I ended up with:
1 Gallon Glass Cracker Jar from Walmart
Rope Caulk
PVC (Polyvinyl Chloride) Sheet, Opaque White, Standard Tolerance, UL 94/ASTM D1784, 1/2" Thickness, 12" Width, 12" Length Should get 4 lids from this.
Winters PEM Series Steel Dual Scale Economy Pressure Gauge, 30"Hg Vacuum/kpa, 2" Dial Display, +/-3-2-3% Accuracy, 1/4" NPT Bottom Mount
Century Drill and Tool 95202 High Carbon Steel National Pipe Tap, 1/4-18 NPT
TEKTON 4720 Quick Connect Coupler Set, 5-Piece
1/4 in. Female x 1/4 in. Female x 1/4 in. Male Brass Tee Fitting
1/4 in. Full Port Ball Valve
1/4 in. x 1/4 in. Lead-free Brass Barb x MIP Adapter x2
5/16 in. OD x 3/16 in. ID x 20 ft. Clear PVC Tubing
2.5-oz. Clear Small Projects Silicone Adhesive
Single Stage 1/3HP 4CFM Rotary Vane Vacuum Pump HVAC Air Conditioner RefrigerantGot for $77 on auction today with free shipping!

then add in:
2-1/2 gal. Gallon Pressure Paint Tank with Insiders Club discount this month at $75

Grand total: Aprox. $240

Again, thanks for all of the C&C and good advice!
 
NotNate, I cant be much help with the vacuum, but I did just buy the HF pot to do pressure casting and have had no problems with it at all... I did NOT modify anything on it, but casting up to 40psi it has worked flawlessly.
 
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