Yeah, I learned the hard way about moisture in LOX lines on my test
stand. The first time I tried a cold test with LN2, I didn't bother to
completely dry out the ball valves after water testing. The ball valves
were fine but the water clogged up the injector.
Here's a picture of LN2 that was supposed to be full flow:
http://www.watzlavick.com/robert/rocket/uncooledChamber/tests/p1240017m.jpg
Same test condition after drying out the valves and lines:
http://www.watzlavick.com/robert/rocket/uncooledChamber/tests/p1250008m.jpg
On a different occasion, I was testing with LN2 on a rainy day in the
garage. It quickly uncovered a bunch of other problems such as "it's
hard to put a cap back on a fill fitting when it's covered with a
quarter inch of ice". I use a QD fitting on my test stand for LOX
filling but it's big and heavy so I plan to use an AN fitting for LOX
loading on the vehicle. If I can get a cap back on it afterwards,
that's a bonus but there is a manually operated ball valve for filling
just on the other side of it.
My burst discs are domed so pulling vacuum might not work. Running a few
passes of dry gas through the system should help - it's worked on the
test stand so far.
-Bob
On 11/09/2015 12:02 AM, Monroe L. King Jr. wrote:
Just FYI I would put a vacuum on the system before I loaded propellant
to ensure the least amount of moisture in the system.
Think about on launch day say a LOX fill valve freezes. Here's something
that happened to me. I put a quick disconnect on the wrong side of the
valve and the quick connect froze and I could not get it free.
