[TECH] How many PSI does it take to activate a Schrader valve ?

[99guspuppet]

If one is applying pressurized gas to the input side of the valve…. how much pressure is required to move the valve into the open state ( even a little bit open ).

Gus in Denver

[Denny Esterline]

No clue. Back of an envelope math suggests 100+ psi.

Assumption - sealing surface 0.10" diameter
Pi * r^2 = 0.00785 in^2 area
Assumption - spring force = 1 lb force.

Pressure = force /area
1/0.00785 = 127 psi
Keep in mind that's plus whatever pressure is on the other side of the
valve - which is further complicated because the area the seal contacts
contributes to the closing force area, but does not contribute to the
opening force area.

-Denny

[Denny Esterline]

Sorry if I offend with the thread necromancy.
Yesterday I had the "opportunity" to stand around an auto repair shop for a
while with nothing better to do. Littering the ground were an ample supply
of valve cores and I collected a representative sample.
I already had a small weight scale and a caliper on my desk, so....
Of the eleven I measured, the force to open ranged from 6.5oz to 17.2 oz.
with most of them clustering around 13-14oz
The sealed opening seems to all be about the same size, 0.093" ID x 0.114"
OD
Some may have been 0.095" ID, but I'd say that's probably within the
tolerance considering these have been laying in the parking lot being
driven over for who knows how long.

So re-doing the math puts the range of pressures at about 65 to 170 PSI
(plus the pressure on the other side of the valve)

Call it another win for back of the envelope math. :-)

-Denny

BTW, I know there are other types of commercial Schrader valves, fuel
injection pressure test ports and air conditioning systems come to mind,
and I suspect those are likely completely different in both size and spring
force.

[Kerry]

How many PSI does it take to blow up a volleyball?

We were having a company picnic at a local state park. The boss was
bringing sporting equipment, including a volleyball. It was soft, so he
stopped at a gas station to fill it. The ball said "7-9 PSI", so he set
the pump to 79 and inserted the needle. That was enough to blow it up,
all right!

Post by Denny Esterline
Sorry if I offend with the thread necromancy.
Yesterday I had the "opportunity" to stand around an auto repair shop for a
while with nothing better to do. Littering the ground were an ample supply
of valve cores and I collected a representative sample.
I already had a small weight scale and a caliper on my desk, so....
Of the eleven I measured, the force to open ranged from 6.5oz to 17.2 oz.
with most of them clustering around 13-14oz
The sealed opening seems to all be about the same size, 0.093" ID x 0.114"
OD
Some may have been 0.095" ID, but I'd say that's probably within the
tolerance considering these have been laying in the parking lot being
driven over for who knows how long.
So re-doing the math puts the range of pressures at about 65 to 170 PSI
(plus the pressure on the other side of the valve)
Call it another win for back of the envelope math. :-)
-Denny
BTW, I know there are other types of commercial Schrader valves, fuel
injection pressure test ports and air conditioning systems come to mind,
and I suspect those are likely completely different in both size and spring
force.

[Justin Richards]

Post by Kerry
stopped at a gas station to fill it. The ball said "7-9 PSI", so he set
the pump to 79 and inserted the needle. That was enough to blow it up,
all right!
Did he mention that it was loud and scary with a half time uniform change

or did he take it in his stride.

I brace myself when inflating within spec.

Justin

[Kerry]

He was quite embarrassed by it, and since he was my boss I didn't press
him for details. Judging from the tattered remains of the ball, I
concluded that it was rather exciting.

Post by Justin Richards

Post by Kerry
stopped at a gas station to fill it. The ball said "7-9 PSI", so he set
the pump to 79 and inserted the needle. That was enough to blow it up,
all right!
Did he mention that it was loud and scary with a half time uniform change

or did he take it in his stride.
I brace myself when inflating within spec.
Justin

[RussellMc]

Post by Kerry
He was quite embarrassed by it, and since he was my boss I didn't press
him for details. Judging from the tattered remains of the ball, I
concluded that it was rather exciting.

​I just know I shouldn't mention 1.5l PET bottles at about 200 psi.
So I won't :-)
(Very exciting).

R​

[David VanHorn]

I just had occasion to test a schrader valve with vacuum on the back side.
I got down to 1 torr and the valve didn't open.
I'm using it to pressurize my vac manifold to find pinhole leaks.

Post by RussellMc

Post by Kerry
He was quite embarrassed by it, and since he was my boss I didn't press
him for details. Judging from the tattered remains of the ball, I
concluded that it was rather exciting.

​I just know I shouldn't mention 1.5l PET bottles at about 200 psi.
So I won't :-)
(Very exciting).
R​
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[Justin Richards]

Back in the day I found the tubeless valves that littered the tire shops
useful as bicycle tube adapters that were similar to presta.

Great work by the way.

Justin

Post by Denny Esterline
Sorry if I offend with the thread necromancy.
Yesterday I had the "opportunity" to stand around an auto repair shop for a
while with nothing better to do. Littering the ground were an ample supply
of valve cores and I collected a representative sample.
I already had a small weight scale and a caliper on my desk, so....
Of the eleven I measured, the force to open ranged from 6.5oz to 17.2 oz.
with most of them clustering around 13-14oz
The sealed opening seems to all be about the same size, 0.093" ID x 0.114"
OD
Some may have been 0.095" ID, but I'd say that's probably within the
tolerance considering these have been laying in the parking lot being
driven over for who knows how long.
So re-doing the math puts the range of pressures at about 65 to 170 PSI
(plus the pressure on the other side of the valve)
Call it another win for back of the envelope math. :-)
-Denny
BTW, I know there are other types of commercial Schrader valves, fuel
injection pressure test ports and air conditioning systems come to mind,
and I suspect those are likely completely different in both size and spring
force.
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[Roger, in Bangkok]

A Schrader valve is opened simply by screwing the on the air hose
connector. Unscrewing it then allows the spring-loaded valve to reseat
itself closed.
ᐧ

Post by 99guspuppet
If one is applying pressurized gas to the input side of the valve…. how
much pressure is required to move the valve into the open state ( even a
little bit open ).
Gus in Denver
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[Justin Richards]

The little nipple that operates the valve snapped off my tube inflater and
I could not push any air into the valve at appox 100psi the max air
compressor pressure

justin.

Post by 99guspuppet
If one is applying pressurized gas to the input side of the valve…. how
much pressure is required to move the valve into the open state ( even a
little bit open ).
Gus in Denver
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[RussellMc]

Post by Justin Richards
The little nipple that operates the valve snapped off my tube inflater and
I could not push any air into the valve at appox 100psi the max air
compressor pressure

​Lending credibility to Denny's BOTE estimate.


Russell
​

[Justin Richards]

BOTE estimates, I like it

Post by RussellMc

Post by Justin Richards
The little nipple that operates the valve snapped off my tube inflater

and

Post by Justin Richards
I could not push any air into the valve at appox 100psi the max air
compressor pressure

​Lending credibility to Denny's BOTE estimate.
Russell
​
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[Roger, in Bangkok]

1) Stick a BB, or something more appropriately sized, on the hose connector
where it broke off. Let gravity help you keep it there by turning the tire
valve to 12:00 position :-)

2) When you buy a replacement connector/hose, buy 2 so you can lose the
spare one... works for me every time ;-)
ᐧ

Post by Justin Richards
The little nipple that operates the valve snapped off my tube inflater and
I could not push any air into the valve at appox 100psi the max air
compressor pressure
justin.

Post by 99guspuppet
If one is applying pressurized gas to the input side of the valve…. how
much pressure is required to move the valve into the open state ( even a
little bit open ).
Gus in Denver
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[Neil]

Yes, the valve is not pressure operated, though considering the design,
it may get pushed in at some thousands of PSI.

1) Yep -- BB etc will work. In a pinch, I've successfully stuck a small
stone in one to get it pushed open.

2) Odds are you may lose the primary one though, and then have to use
the spare one. ;)

Cheers,
-Neil.

Post by Roger, in Bangkok
1) Stick a BB, or something more appropriately sized, on the hose connector
where it broke off. Let gravity help you keep it there by turning the tire
valve to 12:00 position :-)
2) When you buy a replacement connector/hose, buy 2 so you can lose the
spare one... works for me every time ;-)
ᐧ

Post by Justin Richards
The little nipple that operates the valve snapped off my tube inflater and
I could not push any air into the valve at appox 100psi the max air
compressor pressure
justin.

Post by 99guspuppet
If one is applying pressurized gas to the input side of the valve…. how
much pressure is required to move the valve into the open state ( even a
little bit open ).
Gus in Denver
--
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View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

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