However, to follow up with Ben:
Medium, high pressure and UHP fittings are PHENOMENAL. If you do them right
(cone-and-thread fittings), they never, ever leak. And they are very
repeatable. Not good for vibe, but for test stands, they are great!
Maximator makes the best tools for them. Peter Duffy at High Pressure
Technologies is about the best sales guy you will ever talk to, and he will
sell you anything you need for 10k+ work. Tubes, fittings, valves,
anything.
I agree with Ben on not using bite type fittings EVER for above 10k work.
Cone on thread is the best!
On Fri, Mar 27, 2020 at 8:55 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:
with LOX (3/4 or 1 in)? I’ve used AN (37 deg flare) and NPT fittings
Hi
Has anyone on the list used Swagelok compression fittings in service
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.
could vibrate loose. I’ve seem amateur liquid systems using NPT
The Army missile spec forbids NPT fittings. Most likely reason is they
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.
escape I run out back for a few hours. Thanks and everyone take care.
I’m lucky. My outbuilding is also my rocket workshop. When I want to
Be Safe,
Rick Wills
Huber Heights, Ohio