Pressure/Vacuum Casting

Signed-In Members Don't See This Ad
Status
Not open for further replies.

SuperDave

Member
Joined
Jun 15, 2007
Messages
682
Location
Sherwood, Oregon - 97140, USA.
Well, I bit the bullet and bought a Pressure pot so I can do pressure/vacuum casting.

For the vacuum chamber, I welded up some .25 CRS plate into a four sectioned vacuum chamber that has a 1" thick acrylic top. Each chamber can contain separate loads of dye, stabilizer, resin, etc and be shut off if not loaded.

The Pressure tank came from EFD and is rated for 100 PSI (see picture.)

My question is: How to configure the connections on the pressure pot.

There is the orange pressure relief valve, no issue there.

I installed the vacuum line with a check valve that will run off my vacuum pump used for my veneer press. That way I can also run vacuum to the pressure pot as well as my vacuum chamber.

Then there is the pressure gauge that has a fitting on the top and a black plastic, threaded "something-or-other" screwed into the top. What is it? The plastic doohickey is closed off at the bottom, so there is no pass-thru...

Where do I connect the incoming line from my compressor? Should I connect a T fitting to the center fitting and add flow control (or two) that I can switch between outgoing (vacuum cycle) and incoming (pressure cycle)?

Should I remove the black plastic mystery piece or leave it be... Hummm... Any suggestions would be much appreciated!

Thanks!

Image Insert:
2007615182815_Pressure%20Pot.jpg
 
Signed-In Members Don't See This Ad

skiprat

Passed Away Mar 22, 2022
In Memoriam
Joined
Oct 19, 2006
Messages
7,812
Location
In a Skip in Wales
Hi Dave, welcome to IAP. This place rocks!!!

I may be wrong, but I would connect my vacuum pump to the middle point like you said and remove the brass nut holding the black bit when doing pressurising. The regulator will control the input pressure. The brass / black piece could then be used to blank of the vacuum port.
There are loads of guys here doing what you are, so I'm sure someone will set you right.
Have fun
 
Joined
Jan 2, 2005
Messages
1,199
Location
Atlantic Beach, Florida.
The pressure tank/pot/vessel had no "literature" accomanying it?..

Well the dohicky with the gauge attached to it looks pretty much like a air pressure regulator. The black plastic thingy, is probably just a plug. But then I could be mistaken, without really looking at it. There should be an arrow on the back or bottom of the regulator body to denote the direction of airflow. If you are going to use this for both vacuum and pressure you will need a shutoff valve between the air regulator and the pressure/vacuum vessel.
 

SuperDave

Member
Joined
Jun 15, 2007
Messages
682
Location
Sherwood, Oregon - 97140, USA.
Originally posted by gketell
<br />And another valve between the pressure relief valve and the tank. The PRV may not hold against vacuum.

GK

Greg,

Good point about the PRV. A ball valve closing off the PRV is in order just in case.

I have removed the black plastic ("plug???) from the pressure gauge housing and installed a fitting and ball valve to close off the path when under vacuum. I will connect a quick-connect to the ball valve for the air line from the compressor.

I have installed a ball valve on the brass pipe in the center and branched off a vacuum line with a one-way check valve on the other end of the ball valve. The vacuum pump circuit has an adjustable sensor that will keep the vacuum at a consistent level.

I will run a vacuum test to see if the PRV will seat effectively under vacuum or if I need to install another ball valve between the tank and the PRV. I would never have thought of that and spent forever looking for the source of the vacuum leak.

Just talked with my son who is a Submariner on a Trident class sub and he confirmed a lot of my suspicions, though they have triple redundancies in most of their lines...

Thanks!
 

its_virgil

Member
Joined
Jan 1, 2004
Messages
8,102
Location
Wichita Falls, TX, USA.
SuperDave,
I use the paint tank for both vacuum and pressure. I have a gauge that will measure both. I use a quick connect on both the vacuum and pressure supply and have a valve in the vacuum line to shut off the vacuum when I stop the pump. I use the pressure regulator on the compressor to regulate the pressure and leave the compressor hose attached during the pressure part of the casting. I've included a picture of my paint tank lid.
Do a good turn daily!
Don


200761613445_PP%20whole.jpg
 

SuperDave

Member
Joined
Jun 15, 2007
Messages
682
Location
Sherwood, Oregon - 97140, USA.
Don,

We are on the same page!

My vacuum gauge is on my vacuum press where I have two additional vacuum resevoirs to minimize the recycling of the vacuum pump and where the adjustable sensor is to monitor a drop in vacuum and start the vacuum pump.

I plan on setting the compressor pressure regulator to 95 PSI and then set the pressure regulator on the pressure pot to something less that 95 PSI. This will give me a redundant regulator setup as that concerns me more than the vacuum.

Here is the new picture showing the two ball valves (Blue is incoming from compressor)- (Red is outgoing from vacuum pump... with inline check valve) installed so I can close one or the other depending on the use of pressure or vacuum.

If, as mentioned previously, the PRV (Orange) becomes a source of vacuum loss, then another ball valve will go between the PRV and the tank.

Tomorrow is a disassembly, joint tape and reassembly test day! It's been nearly a year getting the time and materials to pull the trigger on this project! Thanks to lurking on the IAP site, this is the end result... nest stop, "Castaway"!!

Dave

200761634028_Pressure%20Pot%20II.jpg
<br />
 

SuperDave

Member
Joined
Jun 15, 2007
Messages
682
Location
Sherwood, Oregon - 97140, USA.
Okay... two days of leak-down testing revealed only minor leaks in the obvious places. Re-taped a few joints, replaced tape in a couple of joints I assumed were OK and weren't and went to the Borg to get a couple of new fittings and #9 O-rings.

First and most obvious weakness was the 1/4" brass pipe in the center of the lid. It was locked down from under the lid with a fitting and an o-ring but still too much lateral play in the shaft created a leak. I thought I could get another 4" x 1/4" pipe with 1" of thread instead of the 1/2"... think again. This necessitated some Aisle Engineering. I took a 1/4 x 1" nipple and coupler and made an "extension" for the original brass pipe. O-rings, on both sides of the lid sealed the connection... no leaks.

The remaining leaks are isolated to the o-ring seal on the lid itself, which seem to be the most active, and a smaller leak in the regulator just under the pressure adjustment dial. The regulator is an easy replacement and not too costly. I am going to double check the lid o-ring for any compromised areas, as well as checking the mating surfaces for any flaws, etc.

I have had the pot under 70# pressure and, even with the remaining leaks, it took 20-30 minutes for the compressor to cycle back on. If I can resolve the lid leaks, it will most likely take a much longer time to cycle. If I can't improve the lid seal, I can still live with the current pressure performance.

Next up: A vacuum Leak Test... and this one will be a bigger challenge, I am afraid.

Dave has left the room...

20076183344_PP%20Leak%20Test%202.jpg
<br />
 
Status
Not open for further replies.
Top Bottom