Brent,
Failure modes are different for internal pressure vice external
pressure. In the case of a PSUB, buckling of the hull cylinder is the most
prevalent mode of failure. Pressure tests to destruction on the K-series
of subs found that the viewport was the first to go.
What point are you attempting to make here with this example?
R/Jay
Respectfully,
Jay K. Jeffries
Andros Is., Bahamas
A skimmer afloat is but a submarine, so poorly built it will not
plunge.
From:
owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Brent
Hartwig
Sent: Monday, August 06, 2007 4:39 PM
To: PSUBSorg
Subject: [PSUBS-MAILIST] Stainless Steel Pressure Tanks 100% MIG Welded
I just
spent a couple of days with a guy that a local welding fabrication
guy considers to be a pressure vessel tank god. Lou is a good friend
of mine, and we talked at length about allot of welding and fabrication issues.
www.solartanks.com
His tank
head and tube seams are MIG welded with a special custom built automated
machine. He doesn't need to back gas his welds when he uses this machine, and
says the weld bead cools just as it gets to the other side of the seam. We
looked at the inside of the weld seam of one of his larger 30" OD
tank heads. They looked great. He said there is a paste of sorts, that you can
put on the backside of a seam to protect the bead from oxidation when off hand
welding stick, MIG, or TIG.
With
regards to this said shielding paste, I have another professional welding
friend that said he used to mix diatomaceous earth with water to make a past,
and then put that onto the back side of a seam, let it dry, and then weld.
The coating insulated the weld bead from oxidation, is what he said.
Here is a
pic of the type of weld bead Lou get's on his tank heads with his automated MIG
machine.
http://www.frappr.com/?a=viewphoto&id=4001713&pid=7350506
For his
smaller through hull penetrations, they just MIG weld them off hand.
Lou did a
destruction test on one of his smaller 316 stainless steel, thinner gage,
compressor tanks, that are only supposed to be rated for a general use of 150
PSI. To do this he filled the tank with water and then hooked it up to a
hydraulic pump able to go to 1200 PSI. He took it up the 1200 PSI and nothing
happened except the heads (which were pretty flat to begin with) belled out
some more. He couldn't destroy the tank with 1200 PSI internal pressure, so he
just turned the pump off.