outofofficebrb
HARRO HUNNAYYY
When in transport I leave the doors to the housing and strobes open with the o-ring attached.
do I need to remove strobe O-rings and arm O-rings for flights?
- Thread starter M DeM
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do you leave your flash battery compartment unlocked?
Chris Ross
Contributor
I generally remove o-rings, mainly over concerns of having them develop a set but as far as them holding a vacuum inside I believe the risk is minimal. For example my INON strobes and torches were shipped to me by air with o-rings in place. The only way I see this occurring is if the housing back is in place but not clamped, that way higher pressure air could lift the back and escape but can't reverse flow when air pressure increases, probably more likely if the back of the housing is flat and the o-ring is in a surface groove. Apart from this situation an O-ring in most cases should deal in both directions, so developing a vacuum should not be possible.
I would service and check the o-rings when I reached the final destination regardless so whether it's in the groove or in a ziplock makes little difference. The way I pack the housing and ports are separate and the housing front cap doesn't seal so it's never going to hold a vacuum. If you are going to leave O-rings in place clamp the door shut as you would when in water.
If you're using paper or something else to prevent the housing sealing you might as well pull the o-rings as I think I would like to check that o-ring for contamination from the paper or whatever was used to break the seal before getting it wet. Same for leaving the housing open with an o-ring in place, that's just inviting hairs and lint to get all over you nice clean o-ring and you have to pull it for inspection. Better to just put your clean o-ring in a ziplock.
Of course if you have a vacuum valve (can't imagine working without one) then do what you like equalizing is easy.
Another thing to note, the hold is the same pressure as the cabin on all planes, there's only a thin flat floor between the two which would not withstand any sort of pressure differential, the only difference is the hold is not always heated. So the same rules apply regardless of where you have your housings.
I would service and check the o-rings when I reached the final destination regardless so whether it's in the groove or in a ziplock makes little difference. The way I pack the housing and ports are separate and the housing front cap doesn't seal so it's never going to hold a vacuum. If you are going to leave O-rings in place clamp the door shut as you would when in water.
If you're using paper or something else to prevent the housing sealing you might as well pull the o-rings as I think I would like to check that o-ring for contamination from the paper or whatever was used to break the seal before getting it wet. Same for leaving the housing open with an o-ring in place, that's just inviting hairs and lint to get all over you nice clean o-ring and you have to pull it for inspection. Better to just put your clean o-ring in a ziplock.
Of course if you have a vacuum valve (can't imagine working without one) then do what you like equalizing is easy.
Another thing to note, the hold is the same pressure as the cabin on all planes, there's only a thin flat floor between the two which would not withstand any sort of pressure differential, the only difference is the hold is not always heated. So the same rules apply regardless of where you have your housings.
Mike1967
Contributor
I don't have any fancy camera gear but do I have to worry about any of this for a GoPro? Or anything that's got an O-ring in it for that matter (Perdix, torches etc).
Do the math. The cabin and cargo compartments of commercial aircraft are usually maintained to a pressure of not less than about 8,000'/2,438M, That equals about 10.9 PSI or 0.768 kg/cm². Calculating the surface area the O-ring seal multiplied times the pressure differential will tell you how much force is acting to blow it open, or hold it shut if air leaks out at altitude.
Generally speaking, housings for underwater use are designed to resist external pressure. A piston sealed O-ring like on some computers and flashlights are far less likely to leak with internal overpressure PROVIDING that the mechanical closures on the "door" can withstand the internal pressure/forces. Flat-faced O-ring seals on doors held with spring loaded closures will flex and allow air to leak out while a threaded closure won't.
The Perdix battery compartment is sealed with 3 piston sealed O-rings and a threaded connection -- no problem. The rest of the housing is sealed from the battery compartment so must be able to withstand the internal pressure at altitude or reports of failure after flights would be common. Hopefully all this will help you decide which pieces of gear to be concerned over. Leave it open or take the O-ring out when it doubt. It's a bummer to land at an expensive vacation destination and deal with equipment failures before your first dive.
Mike1967
Contributor
Wow. That was fun. Thanks.
Chris Ross
Contributor
The second half of that equation is that if the door can lift and let air out, it can't do that in reverse when ambient pressure increases. It's a one way street leading to a pressure locked housing.
My argument is if you have equipment like this you may as well remove the o-ring rather than trying to prop the door open or leave a piece of paper in as most luggage will have lint and grit in which will find it's way to the o-ring and you are going to need to check it when you get to the location anyway so you might as well keep it in a clean zip lock. Torches and strobes with screw closures are better equipped to withstand the internal pressure, so I generally leave my torches alone and just pack them. If it's a press in closure, removing the o-ring is probably safest.
Agreed. The nomenclature used in the industry is a "pressure seating O-ring", which is a little misleading. All O-rings are pressure seating because they are designed to move in the groove under pressure. The illustrations under Post 2: How do O-Rings Work?' illustrates the progression:
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