Aw, you flatterer.
I googled "preswaging die" and the thing I was talking about doesn't
come up, so here's a direct link:
https://www.swagelok.com/en/catalog/Product/Detail?part=MS-ST-400
I think it's unnecessary at 1/4, but useful at larger sizes. It's a
fitting made of harder material, so that you can get the ferrules to
clamp onto the tube before the final install. You stick it in a vice
and wrench the nut and tube down onto it, then unscrew it and install
it on the fitting.
Regardless of your opinion on the fitting system, by all accounts
Swagelok makes the finest handheld tube benders on the market. Even if
you're all AN, you should have a -8, -6, and -4 Swagelok tube benders.
And then understand what the markings mean.
On Fri, Mar 27, 2020 at 9:08 PM Jonathan Goff <jongoff@xxxxxxxxx> wrote:
Thanks Ben! That's the kind of on-topic and super-useful post that makes me
glad I'm still subscribed to aRocket.
~Jon
On Fri, Mar 27, 2020 at 9:55 PM Ben Brockert <wikkit@xxxxxxxxx> wrote:
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