Another consideration with ball valves handling cryogenic/saturated liquid.
I've seen people using regular ball valve (with compatible material - often
SS and PTFE seals, and with a longer stem) and simply drilling a hole on
one side of the ball itself. This allow any LOx that might have gotten
trapped in the valve body upon actuation to be relieved on one side or the
other instead of pressurizing the valve's internal upon warming up.
Cheers,
Miguel
On Sun, Aug 26, 2018, 6:43 AM Lars Osborne <lars.osborne@xxxxxxxxx> wrote:
Henry,
Thank you for pointing that out. I had forgotten to mention the caveat
that the materials themselves must be cryo compatible!
Thanks,
Lars Osborne
On Sat, Aug 25, 2018 at 11:01 AM Henry Spencer <hspencer@xxxxxxxxxxxxx>
wrote:
On Sat, 25 Aug 2018, Lars Osborne wrote:
I'm surprised no one else has pointed this out, but any valve can be a
cryo valve if you have enough torque...
Well, no, there are issues that aren't solved that easily. Most
especially, any valve with parts made of ordinary steel is *NOT SAFE* for
cryo use, because the steel will go brittle at cryo temperatures. That
alone will take an awful lot of non-cryo valves out of consideration for
cryo applications.
Seals can naturally have similar issues, and differences in thermal
contraction between different materials can cause trouble even if the
materials are individually okay.
Henry