Just as a follow up:
1) I bought a grease gun as suggested and will be hydro testing this vessel to 1.5x working pressure, as well as testing some smaller similar vessels to failure to see what the 'real' safety margin is... Hoop stress calculations for this 'vessel' indicate that at 125psi the safety factor is over 40x so overall I'm not super worried about the pipe, as others have stated I'm sure the end caps would be the first failure point at higher pressures.
The reason I want to hydro test some smaller 'scale replica' vessels to failure is because there has been such a huge variety of feedback on the safety of this system that I want to get some real-world results to see how they stack up to the feedback and to the specs on the pipe and fittings. I will make a video for my YouTube channel and will post it here when it's finished!
2) I have been using the vessel at lower pressure while enclosed in the steel base cabinet for my lathe, figured that was a good safety measure in the short term. No issues at all so far, though reliably sealing the threaded end cap is a total pain and I will be replacing it with a flanged adapter and cap as suggested to make opening/closing the vessel easier.
3) PRESSURE CASTING WORKS GREAT!!!
Pressure casting is a pretty well proven process which is why I went this route... Everyone who has said you 'need vacuum' is off base here. If I was to use vacuum degassing I'd have to babysit the resin to make sure it doesn't overflow, then be extremely careful while pouring it to make sure I don't entrap any air-bubbles, and agitating the mixture to make sure the powder stays suspended in the resin would obviously cause huge problems with creating new bubbles...
With pressure casting I have been mixing the powder and epoxy mixture by hand with no care not to create bubbles, pouring it directly into the mold and then curing it in the pressure pot. The reason bubbles are potentially such a huge issue for me is because I am cutting into the casting and so I would expose any bubbles inside. I have cast and machined several blocks of material so far using the pressure method with ZERO issues, and no voids or bubbles found.
This is what the material looks like when cured at ambient pressure, full of bubbles and voids:
This is what it looks like when cured at 60psi, the texture makes the details a bit hard to see but there are ZERO bubbles:
The final result:
This is Strontium Aluminate glow in the dark powder mixed with casting epoxy at basically 100% fill along with pigments to get the daytime color correct, then cast in place inside the G10 composite handle scales for my knives. It's then machined so the glow powder shows up as a liner next to the opaque black G10.
It's been a pain to work this process out, lots of failed attempts precede the move to pressure casting, but it seems to be working great now! This stuff is BRIGHT, easily visible in a dark room after 10 hours.
I will report back once I have the hydro test results for the various vessels.
-Aaron