Is this unsafe?

[Tweeter]

I noticed that there are some marks on my air venturi male foster fitting.  I have this connected to the gold female fitting on the small filter and it is a little loose.  Not terribly loose but I think it is whats causing this?  I would just thread my microbore hose directly onto the blue filter but the threads are different and am not going to risk that. 

Are these marks normal or should I find another way to connect everything?  Hopefully the picture is good enough...

[Frank in Fairfield]

What marks?
Where the black paint is wearing off?
Normal

[gendoc]

probably done from normal use....mine is loose also, but the sealing of the
 probe is fine.

[StockClassDD68]

Are you referring to the small shiny dimples on the shoulder of the QD? Seems normal, but if it worries you perhaps get a now male end to put your mind at ease.

Just checked my two most commonly used male QD fittings both exhibit the same dimples, more so on my brass ataman fill probe, just seems to be caused by the extreme pressure and forces involved with our air guns.

[Tweeter]

Are you referring to the small shiny dimples on the shoulder of the QD? Seems normal, but if it worries you perhaps get a now male end to put your mind at ease.

Just checked my two most commonly used male QD fittings both exhibit the same dimples, more so on my brass ataman fill probe, just seems to be caused by the extreme pressure and forces involved with our air guns.

Yes the dimples on the shoulder.  I should have described it better, thanks!  Good idea, I'll order a new one.  A few bucks for peace of mind is worth it.  I already wear body armor when I fill my guns with this thing, I look like an EOD tech. haha. 

[Tweeter]

probably done from normal use....mine is loose also, but the sealing of the
 probe is fine.

Mine seals fine with the Air Venturi male foster but the foster on my fill probe fits so loose that it leaks.  Thanks for the response.

[Mole2017]

Those dimples are from the small balls in the locking mechanism of the foster fitting. I was a little shocked to see them on yours, but I just took a look at mine and it has them too!

Mine aren't so easy to see, though, being a little smaller and on a piece made out of brass with no paint. That size difference might be due to the hardness difference between brass and aluminum, and maybe the pressure. I pump mine to about 3300 PSI max. What pressure do you go to in your system.

[StockClassDD68]

Both of my fosters have been brought right to 300 bar between the leshiy and the AP16, many times and are approaching the depth/prominence of Tweeter's. Hope they don't become a routine wear item . . .

[Tweeter]

Those dimples are from the small balls in the locking mechanism of the foster fitting. I was a little shocked to see them on yours, but I just took a look at mine and it has them too!

Mine aren't so easy to see, though, being a little smaller and on a piece made out of brass with no paint. That size difference might be due to the hardness difference between brass and aluminum, and maybe the pressure. I pump mine to about 3300 PSI max. What pressure do you go to in your system.

I pump my gun to 250bar max about 3600psi.  I don't even dare take this compressor to 4500, let alone the fill hose...  When I noticed them I was a little worried but after looking at the fittings it would basically have to explode for it to come apart.  I will use it carefully until I get the replacement but I think it is okay and seems to be normal.

I think it is the slightly loose fit of the chinese part that is causing it to happen because I've never seen this on any of the male foster fittings on my fill probes.

[plinker81366]

chinese products are good, i think most of our fittings are made in china, what we get here is made in china but high quality,,qf in the pic is filter for my yh, its exposed to 4200psi everytime i top off my scba tank

[KnifeMaker]

There is already a thread on the brass versions failing. If steel dimples, brass hasn't a chance. My airventuri probe foster attachment is blackened steel. Not alu. as posted here.

[rsterne]

I have never seen such deep dimples in a male Foster.... That would make me very nervous.... Brass is NOT recommended for high pressures, it is intended for connecting paintball hoses running 850 psi.... Even the steel Foster brand name fittings come in two grades, and only the best one is rated for 4500-5000 psi....

Do you have any idea what material that male QD fitting is made from?....

Bob

[Wayne52]

I was thinking the same thing as Bob because I have a double male steel fitting that I get my tanks filled with when I have the adapter on the tank and it takes 4600psi every time I get it fill and there's hardly any markings on it.  Even the brass probe that I fill my SPA M16 with isn't near as bad looking as the one in the picture above.  I fill that to 3600psi every time.

[Mole2017]

I was thinking the same thing as Bob because I have a double male steel fitting that I get my tanks filled with when I have the adapter on the tank and it takes 4600psi every time I get it fill and there's hardly any markings on it.  Even the brass probe that I fill my SPA M16 with isn't near as bad looking as the one in the picture above.  I fill that to 3600psi every time.

Thanks for posting picture of a steel unit, Wayne. Looking at the picture, I can see the faintest of marks on that one too, but definitely nothing compared to Justin's unit. I suspect his to painted aluminum as they are somewhat deeper than what I can see on my brass unit.

Here is an assignment for some one: calculate (a) the force the on the Foster connection (just cross section surface area and pressure, I think), (b) the load per ball (which is compounded by the angles), and (c) the contact stress under said ball of whatever radius it is when against the fitting. That last one is essentially similar to contact stresses of ball bearings.

We can probably guess what that tells us. Will it fail? Probably not, as it has to get through a lot of metal to actually shear away. Issues might includes flakes of metal eventually coming loose, but I suspect that is more of a problem for rolling contact. However, maybe we should be asking what is happening to the other side of that fitting. If cheaply made it is taking just as many dings as the fitting. And the balls. If they are good steel bearings, then they too are taking a beating. Are the stresses enough that they might start breaking up? Again, certainly an issue for rolling applications, but I'm not sure about this case. I guess we need to see the load and stress calculations.

Solution: don't use small balls on essentially flat surfaces. Larger balls would help a lot. More balls. Maybe grind a little race for the balls to mate to? Actually any DIY type could try that one and get us a report Beyond that it gets kind of weird and expensive...like come up with a version that uses roller bearings or some sort of wedge, i.e. larger contact area. At lower pressure the ball bearings get us a fitting that can swivel. With dimples like that, I suspect that motion is not happening. If that is the case, then maybe we don't need it in the design in the first place.

[rsterne]

To be truthful, I would be more concerned of the brass female doing the same thing inside where you can't see it.... Eventually that could cause the balls to dislodge and then the male would depart at whatever pressure was behind it at the time.... 

When you see dents like that in anything under pressure, the load is exceeding the yield strength of the material under stress.... That is pushing that material immediately into the zone where fatigue is occurring.... It might never fail where the dents are, by the balls ripping through to the end.... instead it might develop a crack inwards from the dents (they are now stress risers).... and rip the whole end off the male fitting.... OR, the inside of the brass female could fail in several ways.... How long will it take to fail?.... A hundred cycles?.... A thousand cycles?.... 10 thousand cycles?.... I have NO idea, but IMO the clock is ticking....

Only use fittings rated for a maximum safe WORKING pressure that is above what you are using....

Bob

[Tweeter]

Thanks for posting Bob, and that totally makes sense.  I DO NOT want to be on the end of that hose/fitting if it decides to let go.  Looks like I need to find a fitting to convert the metric threads on my compressor to 1/8bsp and then I'll just use my Joe B hose which I trust is rated high enough. 

Anybody have ideas on what to get?

[Tweeter]

I just ordered a male M10 x male 1/8" BSP and a female 1/8" BSP coupling.  I'll screw my Joe B micro bore directly into that and do away with the brass foster.  Wonder how many are using these brass fosters to pump their guns and tanks up to 4500psi?

Thanks everyone, a little ashamed that I never thought about that fitting being brass

[Tweeter]

I have never seen such deep dimples in a male Foster.... That would make me very nervous.... Brass is NOT recommended for high pressures, it is intended for connecting paintball hoses running 850 psi.... Even the steel Foster brand name fittings come in two grades, and only the best one is rated for 4500-5000 psi....

Do you have any idea what material that male QD fitting is made from?....

Bob

I'm guessing brass, I checked and a magnet had no effect on it?

[Tweeter]

There is already a thread on the brass versions failing. If steel dimples, brass hasn't a chance. My airventuri probe foster attachment is blackened steel. Not alu. as posted here.

Hey Knife, do you have a link to where someone had a brass fitting fail?  Just would like to read it, thanks!

[rsterne]

Tweeter, although I have never seen one, I'm guessing that it is made of aluminum.... The colour of the ridges between the dents where the balls have compressed the male fitting are NOT brass colour, they are grey or dull silver in colour.... While it is true that there are some grades of Stainless Steel that are barely magnetic to non-magnetic (and others that are quite magnetic)…. I have never seen stainless that was so soft as to dent as severely as the one in your photo.... Besides, SS is usually a bright, shiny silver finish because it doesn't oxidize....

BTW, I have looked around a bit for the MSWP of brass female Foster fittings and have found two ratings.... 2,500 psi and 3,000 psi.... I also found some that were rated at only 300 psi, but obviously that was an error, at least I presume so.... In any case, I would NOT use that brass female Foster at 3600 psi, which is what you stated you are filling to.... and with the dents in that male Foster, I would definitely NOT continue to use that either....

Bob