As Charlie Poole used to say "the only difference between religion and
rockets is we don't kill each other over rockets" Though some words can be
pretty hurtful.
I hope anyone contributing to this forum does so from a solid experience
base and understands their own limitations as such. Alot of
misunderstandings even friendships have ended because of a misunderstanding
through a simple email.
We the sender know what we're trying to say but that message doesn't
necessarily translate exactly as intended.
Like tube fittings, I probably have more and longer experience with
tube/pipe fittings then 90% of the folks on this listings,>50 years. But no
matter what I say it will be met with confrontation instead of acceptance
OR a question or a request to elaborate. Because I may of omitted a certain
detail doesn't mean I didn't know about it. With my single digit and 5 WPM
I abbreviate frequently and will omit certain things in the interests of
getting to the primary point w/o a diatribe of words. That's why I'll
suggest taking the mater off listing. But that rarely happens, people like
to argue, not all but enough to be frustrating even detrimental.
Be Nice, we're all in this for fun not to pound our respective chests. The
ego is the/our enemy!
This is why I originally left this forum 15 years ago, petty bickering and
hair splitting, only recently rejoining aR. No body's perfect, we "all fall
short" in all our own human frail ways. My hats always are off to those
with more experience, the reverse where applicable. Mentors were
instrumental in teaching me critical lessons that were not possible in the
academic system. Even "Kerbal doesn't teach this". Two of of my mentors
have since passed on, Ray and Bob. Life's short, some shorter than others.
Lets make the most of it.
Exerciser caution with PhD's and "experts". A student of mind once told me
that an expert is "a Has-been and a Leak under pressure". There's that ego
again.
Early/mid 60's, once able to read, I began studying rockets by reading my
late fathers college chemistry,physics and rocket books along with building
and flying model rockets then by age 12 test fired my first liquid rocket.
Then high school which HAD an extensive machine shop, so I built rockets
for >4 years,solid and liquid. Try that now these days. Rocket have
fundamentally been a passion, which was the key to success, a burning
passion, a love of rocketry.which eventually led to a 6 figure income,and
at my 'hobby'! People have often asked me what was my recipe for success
was,what college what degree?. I always said, no school,formal education or
degree, only a burning passion, the rest just falls into place,the mentors,
tools, techniques, intuition,etc,etc. Not boosting here,we all have the
ability to excel in something, just find your gift, then share it to
everyone's benefit. I'm always available to anyone with questions about
rockets, practical systems, "Concept to Combustion", Liquids, Solids or
Hybrids.
Ken
On Mon, Mar 30, 2020 at 6:38 AM David Gregory <david.c.gregory@xxxxxxxxx>
wrote:
Fittings are a topic where everyone has their favorite and the cherry
picking data to suit individual preferences are rampant.
- Flare fittings absolutely blow off under high pressure if the flare is
not properly formed (undersized), no different than swagelok/yorlok. Flare
fittings are less tolerant of tube misalignment as well.
- Any fitting cleaned for oxygen service requires a lubricant to prevent
thread galling. Swagelok happen to have the lubricant built in.
- There are hundreds of manufacturers of cryogenic components with NPT
fittings.
- every single commercial Liquid oxygen system has both NPT and
swagelok/yorlok fittings on it.
Examples of old wives tales about fittings:
"xyz fitting is harder to clean" - they all have to be cleaned properly,
i've never seen a fitting that was any harder to clean than any other.
"NPT fittings cant be used above XYZ pressure" - NPT can be used up to
10,000 psi at least with the correct fittings and installation procedures
"Swagelok are likely to blowoff" - this is only true if the human
installing them didn't read the instructions or swaged them incorrectly.
Incorrect installation will cause failure of any fitting.
"XYZ fitting is more or less vibe tolerant" - its likely that not
fittings are equally vibe tolerant. But the idea that this matters
significantly is silly, an I've never seen a reference which actually
measured vibe tolerance of fittings. a 1/4" tube nut is the same
dimensions and thread for Swagelok and AN. I've seen both NPT and tube
fittings auto-rotate off in vibe environments.
"XYZ fitting can be damaged if over tightened" - again this is true of all
options, and isn't a valid argument for or against any one type.
"XYZ fitting isn't used in flight applications" - i'm confident all of
the options discussed here have flown on flight vehicles
For an amateur, on a limited budget, who is unlikely to see anything
higher pressure than a 2000 psi gas bottle, the choice is pretty clear -
use whatever you can get.
To answer the OP's question - Yes I've used 1" Swagelok in liquid oxygen
service.
On Mar 29, 2020, at 10:15 PM, roxanna Mason <rocketmaster.ken@xxxxxxxxx>
wrote:
For those just getting started or who have little/no Swage inventory just
forget Swageloks and base your plumbing on 37 degree flare fittings,i.e.
AN, (Army/Navy). Swage also have trapped areas that are hard to clean even
though not wetted they will be wetted when a leak occurs and if you try to
tighten it when leaking it could explode.
NPT can be used with LOx/cryo but special care has to be taken
especially stainless steel which will gaul with little/no effort.
Teflon tape with grease, LOx compatible like Krytox or Flurolube, an
absolute must. In certain cases pipe fittings are preferred over AN.
This is a complicated topic requiring much time to do justice so of list
discussion is highly recommended, hard to summarize a half century of
experience in a few paragraphs.
Ken
On Sat, Mar 28, 2020 at 8:35 PM Michael Clive <zeinin@xxxxxxxxx> wrote:
To continue on Ben's vibe:
Swagelok is the best brand for compression type fittings. Parker etc are
slightly worse in terms of quality control, from my experience. Surface
finishes are not as nice, plating is worse. Swagelok also is expensive but
very responsive and kind. Their sales reps will do *anything *for you,
if you buy enough. If not, Ebay will get you everything you need.
NEVER mix and match a parker fitting to a swage body, or a parker body to
a swage fitting. They claim they are interchangeable, but they can have
minor variations in geometry and thread form that can gall stuff up or
generally make your day worse.
McMaster compression fittings are Parkers. They are okay, but nothing
beats the real thing.
Swages above 3/4" become a huge pain in the ass and you need a hydraulic
preswaging tool and a second bank account for fittings at or above 1".
Swages are excellent, but you need to be really experienced with them.
There are no torque specs. *there are no torque specs. *You torque them
down until a certain displacement is met. You then always reseat them with
the tiniest bit more oomf. If you don't have a calibrated arm, you will
overswage if you ever reinstall, and it will leak, and you will have to
pull the tube and replace it. There is no spec for this, it's just a
feeling you develop after doing a few hundred of them.
Big super obvious one that bit me when I was green: Don't swage a brass
fitting on a stainless tube, or a stainless fitting on an inco tube. You
can swage stainless on brass or inco on stainless, but always move down the
strength chain. Why? The brass just won't bite the steel tube and it will
'splode. I had it happen on a 1/2" air line and it was loud and very
embarrassing.
And yeah, if you are a rocket person on this list and are working at
20ksi, good job on gettiing your phase 3 in-space propulsion contract from
$GOVBUCKS. Looking forward to your launch.
My post-apocalypse profession is going to be as a plumber.
On Sat, Mar 28, 2020 at 5:34 PM Ben Brockert <wikkit@xxxxxxxxx> wrote:
Ok, I'll backtrack to say that for 1/4" and smaller, higher pressures
are likely to be fine *if* you are swaging correctly and using normal
hardness tubing. The forces are not as crazy. But still, the advantage
of "cone and thread" and AN fittings is that if they are not tightened
they just leak, rather than having the tube go shooting out of the
fitting like an un- or under-swaged tube.
The Swagelok FK medium pressure system in half inch and larger with
thicker and harder tubing is trouble waiting to happen. I've seen it
go off twice, it's very violent and loud. Fortunately in neither case
was anyone injured.
And for folks new to this, "medium pressure" and "high pressure" are
terms of art for specific fitting systems, where medium is up to
20,000 psi and high is up to 60,000. Most rocketeers will never get
into medium pressure, and the highest you'll ever see is a 6000 psi
bottle that can be worked with using normal AN fittings.
And "Swagelok" is a company and a brand, but generally people use it
specifically to mean two ferrule compression fittings in the
Swagelok/Yor-Lok/A-lok line.
On Sat, Mar 28, 2020 at 2:55 PM Michael Clive <zeinin@xxxxxxxxx> wrote:
right (cone-and-thread fittings), they never, ever leak. And they are very
However, to follow up with Ben:
Medium, high pressure and UHP fittings are PHENOMENAL. If you do them
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 10kwork. Cone on thread is the best!
service with LOX (3/4 or 1 in)? I’ve used AN (37 deg flare) and NPT
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:
Hi
Has anyone on the list used Swagelok compression fittings in
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.
they could vibrate loose. I’ve seem amateur liquid systems using NPT
The Army missile spec forbids NPT fittings. Most likely reason is
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.
to 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
Be Safe,
Rick Wills
Huber Heights, Ohio