Minor Rant about DIN 1st Stage Dust Cap

[fmerkel]

I will defer to your experience......but, do you really think a few inches to a couple feet creates a realistic probability of a flood when the exact same rig is fine down to recreational depths? I simply do not buy it.

IMO, we have our rigs delivered to us for 2 reasons: 1. It's a LOT easier. 2. They are large, heavy, expensive, awkward floppy messes that have the possibility of being damaged or causing injury with the impact of jumping in (see #1).

 

[Bigbella]

I will defer to your experience......but, do you really think a few inches to a couple feet creates a realistic probability of a flood when the exact same rig is fine down to recreational depths? I simply do not buy it.

IMO, we have our rigs delivered to us for 2 reasons: 1. It's a LOT easier. 2. They are large, heavy, expensive, awkward floppy messes that have the possibility of being damaged or causing injury with the impact of jumping in (see #1).

You don't have to "buy" anything. A seal at the surface is simply weaker than a seal under pressure, say, at recreational depth; and the primary rationale of a hand-off, back in the Nikonos days, was the risk of a flood while jumping off a boat. The old SB strobes and Nikonos V were notorious for flooding, generally in the shallows; so too older housings with screw-on ports. The distributors for Subal and Hugyfot both advised having the housing handed to the diver, to lessen the risk of flooding -- not simply because the rigs could be awkward; or on the larger side . . .

 

[PfcAJ]

You don't have to "buy" anything. A seal at the surface is simply weaker than a seal under pressure, say, at recreational depth; and the primary rationale, back in the Nikonos days, was the risk of a flood while jumping off the boat. The old SB strobes and Nikonos V were notorious for flooding, generally in the shallows; so too older housings with screw-on ports. The distributors for Subal and Hugyfot both advised having the housing handed to the diver, to lessen the risk of flooding -- not simply because the rigs could be awkward; or on the larger side . . .

Agreed.

I’ve seen scooters gulp a bit of water in the shallows but seal up fine when a bit deeper. Heck, you can even pop the latches on a canister light at depth and nothing bad will happen. Try that when shallow and your wallet is in for a hurtin’.

 

[wetb4igetinthewater]

I’ve seen scooters gulp a bit of water in the shallows but seal up fine when a bit deeper. Heck, you can even pop the latches on a canister light at depth and nothing bad will happen. Try that when shallow and your wallet is in for a hurtin’.

Is that due to a relative vacuum?

 

[JohnnyC]

Vacuum would indicate an absence of pressure. There’s still pressure in the canister, 1 atmosphere, it’s simply that the pressure at depth is much greater. So significant in fact that it would be nearly impossible to open at depth..

Storage tubes for delivering things to deco habitats and stuff have pressure relief screws on them so you can actually open them up.

 

[wetb4igetinthewater]

Vacuum would indicate an absence of pressure. There’s still pressure in the canister, 1 atmosphere, it’s simply that the pressure at depth is much greater. So significant in fact that it would be nearly impossible to open at depth..

Storage tubes for delivering things to deco habitats and stuff have pressure relief screws on them so you can actually open them up.

Yup. That's why I used "relative vacuum" to indicate a significant difference in pressure.

 

[davehicks]

I will defer to your experience......but, do you really think a few inches to a couple feet creates a realistic probability of a flood when the exact same rig is fine down to recreational depths? I simply do not buy it.

IMO, we have our rigs delivered to us for 2 reasons: 1. It's a LOT easier. 2. They are large, heavy, expensive, awkward floppy messes that have the possibility of being damaged or causing injury with the impact of jumping in (see #1).

Argh! It's just math, no need to take anything of faith.

For each 1 Foot below the surface the Pounds per square inch increases by .443 PSI. If you have a Camera Housing Back that is 8 inches X 4 inches at a depth of only FIVE FEET below the surface you have the equivalent of 69 Pounds of pressure holding that housing securely closed and a whopping 443 Pounds at 32 feet. At 6-12 Inches in a dunk tank you have only 13 Pounds squeezing it together.

So 13 vs 443 is a pretty big difference, don't you think? Kind of like the difference between a House Cat sitting on your chest versus an Adult Lion!

 

[fmerkel]

Yes, but....as stated [The old SB strobes and Nikonos V were notorious for flooding, generally in the shallows; so too older housings with screw-on ports].
Old gear, no longer designed that way, at least that I know of and I've seen a fair share of photo gear on photo based trips.

I do my own regs as do a number of folks here. I have first hand knowledge of what goes on inside. The only time I get water inside is when I forget to put the dust cap on (argh!). Plus there is value to a long soak vs a dunk or spray rinse in soaking salt out of the threads and tight crevices. I've got no problem throwing unmounted regs in a tub of water overnight, and have never had a problem with it. A well designed dust cap, properly attached makes a pretty tight seal.

Note: some regs designed to open up the 1st and/or 2nd stages to take pressure off the seats are another matter. Follow directions there. My stuff is >10 years old and I have no issue with that.

 

[Fathom044]

I would strongly advise against any metal (esp. aluminum) DIN caps. The metal to metal contact is an extremely bad idea. With a little bit of moisture, it will form a bond with the DIN threads that is virtually impossible to break. On a recent trip, someone bought an aluminum one from a local dive shop and it had to be cut off!

 

[Bigbella]

I would strongly advise against any metal (esp. aluminum) DIN caps. The metal to metal contact is an extremely bad idea. With a little bit of moisture, it will form a bond with the DIN threads that is virtually impossible to break. On a recent trip, someone bought an aluminum one from a local dive shop and it had to be cut o

Yeah, I learned that one the hard way, some years ago, before I switched to Delrin plugs. I had an aluminum male plug in a high pressure tank, in storage, and had to resort to channellocks and no small amount of profanity and elbow grease to remove. Thankfully, there was no real damage to the valve . . .