Author Topic: Building Fill Adapters  (Read 360 times)

Briar Patch

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Building Fill Adapters
« on: April 07, 2018, 11:18:50 AM »
Bob,
On another thread you had mentioned that you purchased a CGA-347 fitting, and that you were building your own SCBA fill adapter.
Would you mind sharing your design and specs, etc.?

I thought I'd build my own, but after doing a bit of research I probably have more questions that I had to start off with.
I figured I'd build one using stainless steel components.  Some of my questions ..
How much does pressure rating matter with ss components?  Is #150 enough, or do I need #3000?  Does it matter that fluids aren't compressible and air is?
Hydraulic fittings seem a more economical way to go in many cases.  What kind of fittings are necessary?  ORB, JIC, just NPT? 
Are brass fittings strong enough?  Would you use any dope or teflon tape on the brass? Dowdy seals?

Typical supplies seem to be
CGA-347 fitting,
1/4" cross FNPT
Pressure gauge
Bleed valve
1/4 to 1/8 bushing
1/8 microbore hose with appropriate fittings
foster fill adapter

Would you put in a needle valve - as the SCBA valve may be stiff - tougher to control flow?
What kind of gauge would you use - regarding accuracy what is acceptable  +/- ?

Now, buying all the highest quality stuff is of course going to give the most peace of mind - but what is actually necessary?
Several of the well known & reputable folks who sell preassembled units do use stainless steel components, but some of them also use some other materials.

I know I could put together a very nice one for $200, I could also put together a nice one for around half that.  Several sites have them for sale somewhere in between there. Then there are the ones on ebay and aliexpress for $40-$50.  Those have to be decent or there would be a firestorm on all of the airgun forums regarding them.

The gist - I'm sure whatever you put together has been well thought out, and I would like to ride your coattails to the land of quality adapters.
I am reasonably certain that I am not the only one in this boat.  I suspect a sticky with some guidelines for building assembling adapters would get a bit of use.
Might generate more traffic on this forum as well.  The searches I've done have had less than outstanding results.
 
I want something safe.  Accidents with anything high pressure are bad news.

Anything you, or others, offer is appreciated.



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rsterne

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Re: Building Fill Adapters
« Reply #1 on: April 07, 2018, 03:53:35 PM »
I use hydraulic fittings, which are typically rated at 5,000 psi.... The valve on my SCBA tank has quite a fine control, but they may not all be like that.... In addition, I cut off the dip tube on the valve (that prevents water entering the valve if the tank is inverted) and tapped it for a setscrew which I drilled out to 1/32" as a flow restrictor.... probably doesn't do any good, but it can't hurt....

Use the best gauge you can afford, but in reality a 5% is safe enough for our purposes....

Bob
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Briar Patch

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Re: Building Fill Adapters
« Reply #2 on: April 07, 2018, 04:40:36 PM »
Sounds good. Thank you Bob.

I probably overthink where I don't need to, and tend not to think when I should.   ;D
  • Payson, UT