Eagle
2009-06-19 11:24:31 UTC
hasn't posted since the end of March. If he went, god bless him. In
July of 2008 he finally found a way to construct a "flow control
regulator" for the party balloon helium tank variety. With parts you
could buy mainly at home depot and some other places. If the helium
tube tent method turns out to have problems with it, I will consider
constructing his flow control regulator and use it with an exit
plastic bag. I will test it out first with one tank. Then do it with
another when I was sure it worked. I haven't exactly read through all
the parts you have to assemble and haven't figured out if it's really
that easy to build, but it looks much easier than the one that doctor
builds in the Peaceful Pill Handbook. Here is the post he made:
On Thu, 24 Jul 2008 20:04:10 -0700 (PDT), Carbon <***@black72.com>
wrote:
I could hardly be happier right now---I've just built and tested a
simple, inexpensive flow restrictor for those "balloon kit" helium
tanks, and it works! Best of all, I was able to get all the parts I
needed (save for one tool) at Home Depot---no need to dodge questions
at the local industrial-supply store.
I'm so psyched. I basically have my method now, and am just a couple
of trial runs away from finally being free of this useless existence.
Anyone who's interested in the details, keep reading.
--------
Bob Boling designed the flow restrictor as part of a homebrew oxygen
meter for SCUBA divers and described it on his webpage (see section C,
"Flow Restrictor"):
http://members.cox.net/bee2/
Conceptually it's very similar to the flow restrictor described in
"The Peaceful Pill Handbook", but uses parts that are easy to find in
North America.
Here's what I used:
- A 1/4" hose-barb to 1/4" female NPT connector
- A 1/4" male NPT industrial quick-disconnect plug
- A 1/4" female NPT industrial quick-disconnect coupler
- A 8-32 x 1/2" brass machine screw
These four parts came from Home Depot; the first three were in their
air-tools section. Note that I already had a length of 1/4" clear
vinyl tubing and 1/4" hose clamp, both of which were also bought at
Home Depot, plus a 1/4" SAE flare-to-1/4" male NPT adapter that I had
to buy at the industrial-supply store.
Here's how I put it together:
- I attached the quick-disconnect coupler to the SAE flare adapter,
which I then attached to the tank (after removing the balloon-inflater
nozzle). I used white Teflon tape on both connections. Home Depot
sells these couplers in three different kinds: industrial, automotive,
and universal. I originally tried the universal one but found that
under pressure, the plug would pop out on its own. The industrial one
seems to "grip" the plug much more tightly and I haven't had the same
problem. Note that with this coupler the sleeve *must* be pulled back
to allow the plug to be inserted---this appears to be by design, but
it's the first one I've seen like this.
- I bought a tap-and-die set at the local Canadian Tire (a Canadian
chain of big-box stores that are a cross between a hardware and a
department store; Wal-Mart is probably the closest U.S. equivalent)
and used the 8-32 tap to cut a screw thread on the inside of the hose-
barb nozzle. This was the right size for the Husky-brand pack of 2
hose barbs that I bought, but I noticed that the equivalent hose barbs
sold at Canadian Tire had a larger opening and probably would have
required a different tap size and thus a different screw. I guess
every hose barb is a bit different.
I'd never used a tap before but it was super simple: Put the tap
itself in the tap handle, line the tap up with the inside opening of
the nozzle, and start turning. It didn't take a lot of effort either.
- I took the machine screw and screwed it into the nozzle. The same
screw is available with either a flat or a rounded head; I bought the
flat-head variety as it looked like it would fit more snugly, but I
don't know if it's important.
- I wrapped the threads of the NPT end of the quick-disconnect plug
with Teflon tape, then screwed it into the nozzle. This gave me the
finished "regulator", with a 1/4" hose barb on one end, a 1/4" quick-
disconnect plug on the other end, and a screw in the middle blocking
most of the airflow through it.
- I placed the hose over the regulator's nozzle and secured it with
the hose clamp.
- Finally, I plugged the regulator into the quick-disconnect coupler
attached to the tank.
Now, on to the testing. I did just as Bob described on his page,
using an emptied two-litre pop bottle and a plastic oil-change pan I
picked up a while back at an auto store. I found that:
- To block the flow of helium adequately, the screw inside the
regulator has to be screwed all the way into the nozzle, fairly
snugly; and
- Despite what Bob says on the webpage, I had to use Teflon tape on
the two parts of the regulator to keep the helium from leaking out
from the joint, even just for testing.
For the testing itself, I placed everything except the helium tank in
my bathtub, filled the bottle and the pan with water, placed the hose
inside the bottle, then quickly positioned the bottle upside-down in
the pan. I'd already placed my watch on the edge of the tub. When
the watch's second hand hit one of the 15-second marks, I'd quickly
open the valve on the helium tank all the way, then watch as the
bottle emptied and make a note of the time when the first bubbles came
out from the bottom of the bottle.
When I started, the pressure in the helium tank was at 140 PSI (I'd
already used some of the helium testing the regulator as I assembled
it). I did three trials and got results of 11 seconds, 12 seconds,
and 11 seconds for an average time of 11.7 seconds to displace two
litres of water. To convert this to a flow rate in litres per minute,
I:
- Divided 2 by 11.7, to get the number of litres displaced in one
second; then
- Multipled that value by 60, to get the number of litres displaced in
one minute.
This worked out to a flow rate of about 10.3 litres per minute, which
is a bit low compared to the usually-stated target of 15 litres per
minute. But I think this will be fine, because:
- The tank was already partially depleted (the pressure was down from
260 PSI when it was bought);
- I expect to use a larger, "50 balloon" tank for my exit, which I
believe is rated at a higher pressure and thus will have a higher
"natural" flow rate;
- Recommendations on the flow rate to use vary widely, down to as low
as 6 litres per minute, which suggests to me there is no real need for
precision here; and
- The regulator is tricky to adjust anyway, since just slightly
turning the screw can cause a significant increase in the flow rate.
Carbon