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What keeps a fill probe from bursting out of fill hole?

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cj_86

cj_86

Member
Jul 3, 2015
311
40
Illinois, United States
 Foster fittings have that outer collar that locks around a male foster fitting with a satisfying click/snap that lets you know its lock into place. Fill probe I'm using just slides in the fill hole...so whats keeping that sucker from blowing out that hole when I'm filling to 220 bar? Hand pumping a 400ish cc air reservoir takes a while so I do a lot of thinking haha.
 
All of the pressure is isolated between the 2 o rings on the probe and perpendicular or 90 degrees to the probe. Therefore, all of the applied pressure and force is evenly distributed sideways and around the probe pushing against the sides of the fill hole instead of the top and out. Pretty sure if the top o ring failed, the probe would blow out of the fill hole as pressure and force would be parallel and pushing on the top of the probe.
 
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"AJ3"All of the pressure is isolated between the 2 o rings on the probe and perpendicular or 90 degrees to the probe. Therefore, all of the applied pressure and force is evenly distributed sideways and around the probe pushing against the sides of the fill hole instead of the top and out. Pretty sure if the top o ring failed, the probe would blow out of the fill hole as pressure and force would be parallel and pushing on the top of the probe.
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And what happens when you pull out the fill probe with 220 bar worth of pressure on it?
 
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And how hard would you need to pull? (Don't try this at home, kids.)

I don't know what area the o-rings act on, it is small, let's say 1/10th of a square inch.

220 bar *15 = 3300 psi so 330lbs holding it in.

I may be wrong by a factor of 5 or so, but it looks like it will be pretty firmly wedged there, not that I will try it. It would wreck the rings for a start.

To expand on AJ3's answer, I think it is the distortion of the o-rings, due to the pressure which locks the probe in place.
 
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"FukoChan"
"AJ3"All of the pressure is isolated between the 2 o rings on the probe and perpendicular or 90 degrees to the probe. Therefore, all of the applied pressure and force is evenly distributed sideways and around the probe pushing against the sides of the fill hole instead of the top and out. Pretty sure if the top o ring failed, the probe would blow out of the fill hole as pressure and force would be parallel and pushing on the top of the probe.
Click to expand...
And what happens when you pull out the fill probe with 220 bar worth of pressure on it?



Click to expand...
This will happen:

Or perhaps this:
 
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"MarkUK"And how hard would you need to pull? (Don't try this at home, kids.)

I don't know what area the o-rings act on, it is small, let's say 1/10th of a square inch.

220 bar *15 = 3300 psi so 330lbs holding it in.

I may be wrong by a factor of 5 or so, but it looks like it will be pretty firmly wedged there, not that I will try it. It would wreck the rings for a start.

To expand on AJ3's answer, I think it is the distortion of the o-rings, due to the pressure which locks the probe in place.
Click to expand...
I agree, in my mind, the only force holding the probe in the fill port under pressure would be the friction of the o rings due to the huge pressure differential across them during filling...atmospheric pressure on one side and fill pressure of at least 2900 psi on the other. Otherwise pressure should be acting uniformly on the circumference of the probe and fill port not causing any differential forces applied to hold it in place. Not sure how to exactly calculate these frictional forces. Based on a rough estimate of the area of the o ring that pressure would be acting on, I come up with 0.04 sqin so about 100 lbs of force acting or pushing on each o ring at 2900 psi. From there, how much frictional force does this result in? Think it would be pretty difficult to pull out under pressure.
 
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I agree I had a foster fitting that you couldn't feel or hear a click sound for connection so I would hook it up a try to pull it apart to verify and one day it came apart during filling and I almost crapped my pants. It blew the internal o ring out over the top of the male end end so I checked my drawers and tossed it in the trash. Now when I fill I have my face turned away from the quick connect and one hand at the base of the probe
 
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