HPA Fittings Warning

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If brass is a no-no on fittings, why is the threaded connector on high pressure gauges made of brass? That includes the gauges sold by AoA, Airtanksplus, Pyramyd Air, and others. IMHO, it's not brass that is the culprit, it's the lack of quality control and testing from certain manufacturers that is the cause of parts failures. The DIN300 connectors on most of our SCBA tanks and the valves on most tanks are made of brass with a nickel coating.
 
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Brass is used in a lot of high pressure applications. The pressure capability depends a lot on the part geometry and quality, not just the material. Look at the massive wall thickness of that pressure gauge fitting. This thread is mainly about the more fragile quick disconnect fittings and the lack of standards. You buy a Foster fitting and get a cheap knockoff from China (not all product from China lacks quality) that hasn't been pressure tested and truthfully rated and who knows ? Not being sure of the quality, I would rather error on the side of caution knowing that stainless steel is stronger and more forgiving.

The QD fittings made by Foster have been tested and the brass is rated at a lower pressure than stainless. 
 
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I have a couple of these Saber Tactical extended QD’s. I can’t find any PSI rating on their site. I just emailed them and asked where these are manufactured and what there rated for.
I can’t recall seeing any failures of these but not clearly stating there rating seems a little concerning. If you look them up at 910 Airguns they say 5000 PSI.
E92A3CBF-5B98-4FA8-9458-E33E203A1ED0.1638297241.jpeg

 
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Kind of a pita and takes a few seconds to do, but a short tether on the end of your fill whip is cheep insurance. Saves you from being whipped if you do have a blow-off. Doesn’t do squat about scaring the crap out of you when it does blow!
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although I found some kevlar kite string (200lb strength) that may be a better option as it is soft and won't scratch surfaces. OR a braided kevlar line as the string is pretty thin looking. 



Allen
 
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If brass is a no-no on fittings, why is the threaded connector on high pressure gauges made of brass? That includes the gauges sold by AoA, Airtanksplus, Pyramyd Air, and others. IMHO, it's not brass that is the culprit, it's the lack of quality control and testing from certain manufacturers that is the cause of parts failures. The DIN300 connectors on most of our SCBA tanks and the valves on most tanks are made of brass with a nickel coating.
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That is a good point about brass. I use a 10000 psi all brass regulator at work. So the right machined brass alloy can be used. But where is the control and regulation?
 
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If brass is a no-no on fittings, why is the threaded connector on high pressure gauges made of brass? That includes the gauges sold by AoA, Airtanksplus, Pyramyd Air, and others.
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Wondered the same last time I installed a gauge.

This may have something to do with the gauge fitting being male and not having a hoop stress component. I know I've read male threaded PVC fitting threaded into a female copper/steel fitting is OK, but the reverse is not.

With valves/etc. they are pretty thick so hoop stress probably negligible there also, unlike a small foster fitting. I guess it just comes down to the brass threads being strong enough?
 
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Mensor/Wika has been around since 1969. They produce HPA testing equipment, gauges, etc. The Mensor website has a knowledge base. One of their engineers wrote a blog about HPA standards, that is easy to understand-

https://blog.mensor.com/blog/navigating-the-world-of-pressure-fitting-standards


At the end of the day it is up to each of us to set our own standard. This is done by choosing a reliable company to purchase your fittings, hoses, etc. from. (I use only Best Fittings.) inspect your equipment regularly, and discard damaged items immediately. That cheap fitting is not so cheap when it causes a catastrophic loss and damages your gun, or injures someone.
 
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I noticed the male foster fittings on both of my tanks exhibit similar, but less severe looking wear from ball bearing contact that is shown in the beginning of this thread. They are both foster branded. The thing is, I have only used them for 6 months or less. I would say they got used for fills an average of 2 times a week. That's not very many cycles, and I'm sure it has been there for a few months before I noticed, which would make the cycle count even less! I wonder if this is the sort of thing where the balls have to wear/bed into the male fitting and end up work hardening the engagement surface a little in the process. Ball bearings are round and extremely hard. The engagement surface is flat and unlikely to be as hard even on a quality fitting. It seems to reasonable to me that the small contact are between balls and a brand new fitting would lead to the balls bedding into the fitting slightly, which would increase contact area and then wear would not progress further.

Swapping out quality fittings every 10-30 uses doesn't sound practical or sustainable. I'll keep an eye on this and also pay close attention to how soon the wear shows up on any brand new fittings (I bet it will be as soon as the first use).
 
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