[AR] Re: LOX Dewar
- From: Ben Brockert <wikkit@xxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Sat, 15 Sep 2018 22:31:08 -0700
Joseph LaGrave said:
There is a 450 liter Dewar available and it is typically bolted to a steel
pallet so handling requires pallet jack and/or forklift. Beyond that size
you are really talking about a fixed position supply vessel as they are
quite heavy to move about.
Great to hear from you Joseph. Congrats to you and the team on the
Exos launch at Spaceport America, it was great to see and hear you
guys out in the desert launching rockets again! It was nice you guys
had a webcast, I ended up watching on my cell phone because I couldn't
be near my computer at launch time. I didn't see it mentioned on list,
video is here:
https://youtu.be/vGM2H2T86pk?t=1200 and more related
stuff on the channel.
Regarding LOX dewars, for a test stand I was working on about a year
ago we ended up getting 1000 liter "microbulk" tanks. Chart makes them
up to 5500 liters. They are on steel forklift pallets, and Airgas was
able to provide them. The 1000 liter ones fit on a normal size pallet
footprint.
In addition to not needing to move so many LC230s around, it meant
that instead of them swapping dewars out twice a week they would just
show up with a small LOX truck and refill the dewars on site, same
kind of truck as used to show up at Armadillo. We put down some flat
gravel and then dropped a 20' x 20' steel roadplate deck; they'd fill
them then I'd move them with a pallet jack to the stand fill line. A
bit over a ton when full, so important that the roadplate was fairly
flat.
One of the dewars was a 700 liter "HP" rated to 500 psi. 700 liters of
LOX self-pressurized to 500 psi was one of the scarier bits of
hardware I've worked on. Perfectly safe, with relief valves and burst
disk like any dewar, but I still tried to keep it under 200. Because
of the proportionally smaller surface area of the larger tank, the LOX
was happy to sit in it for longer than in smaller dewars.
To me it was interesting that a 1000 liter dewar had exactly the same
hookups as a 130 liter dewar, if in different places. Same CGA
fittings, gas, liquid, and vent. The only problem I ever had with them
was Airgas being super flaky, saying they were going show up and then
not, and one dewar that needed to be re-vacuumed because it was
boiling off too quickly.
We moved up to a 70klb bulk system and away from Airgas.
Unsurprisingly it doesn't have CGA fittings. It takes a full semi
trailer load to refill.
To Brett Coles' original question, the only dewars I own are small
ones for benchtop cryo experiments (and liquid nitrogen ice cream),
and are filled off rented dewars.
Ben
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