Ben,
We used to order them sans the anti-seize on special order. The lead time
wasn’t worth it so we just passivated them as we would anyway, then tested with
30% and checked for bubbles. IIIRC, Stennis had an incident on a concentrator
because of something along these lines but I got that second hand.
I concur regarding the swaging die.
Anthony J. Cesaroni
President/CEO
Cesaroni Technology/Cesaroni Aerospace
http://www.cesaronitech.com/
(941) 360-3100 x101 Sarasota
(905) 887-2370 x222 Toronto
-----Original Message-----
From: arocket-bounce@xxxxxxxxxxxxx <arocket-bounce@xxxxxxxxxxxxx> On Behalf Of
Ben Brockert
Sent: Friday, March 27, 2020 11:55 PM
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: Swagelok and LOX
I kinda hate Swagelok fittings over 3/4". They just suck to get leak tight.
1/4" and 1/8" swagelok fittings are great, they are perfectly suited to the
task. Work fine with LOX. Follow the assembly instructions! Buy a preswaging
die if you use them a lot. 1/4"
swagelok fittings are the easiest way to build weird assemblies like
temperature/pressure ports in pipes or coaxial heat exchangers. And work well
for things like gauge boxes, test benches, etc. They're also called
"instrumentation fittings" and that is a good description of what they are good
for.
They are not great with vibe. Well suited to ground equipment, less so to
flight.
If you use them with peroxide the nuts should be processed in acid first. There
is silver plating on the threads to act as antiseize, if you have a peroxide
leak through a silver fitting then the fitting ends up getting hot and the leak
escalates itself to asking to speak to the manager. Once you strip the silver
antiseize off, then you need to replace it with something else on assembly,
like krytox.
Any use of any swage fitting over 3000 psi is a mistake. Go straight from AN to
cone and thread. Do not believe the marketing around medium pressure swage
fittings. When a 5000 psi fitting decides to dissociate next to you, the best
case is a startling.
Ben
On Fri, Mar 27, 2020 at 5:05 PM Rick Wills <willsrw@xxxxxxxxx> wrote:
Hi
Has anyone on the list used Swagelok compression fittings in service with LOX
(3/4 or 1 in)? I’ve used AN (37 deg flare) and NPT fittings successfully for
LOX. NPT fittings are wrapped with PTFE tape. My entire LOX side on my test
stand is all AN expect for the NPT adapters used on the main LOX valve and
LOX load valve. Any LOX experience with any other brand of compression
fittings (Parker, etc). I’m looking at changing the stand plumbing and am
considering Swagelok. Check out our Facebook page
https://www.facebook.com/midwestpropulsiongroup to see the stand in action.
The Army missile spec forbids NPT fittings. Most likely reason is they could
vibrate loose. I’ve seem amateur liquid systems using NPT fittings
successfully. Any advice would be appreciated. On my first test stand, I
welded the NPT fittings together. It worked but looked pretty bad. An A&P I
know suggested safety wiring the NPTs so they would come loose. That is a
lot of work.
I’m lucky. My outbuilding is also my rocket workshop. When I want to escape
I run out back for a few hours. Thanks and everyone take care.
Be Safe,
Rick Wills
Huber Heights, Ohio