Hookah's first stage, what is different in it?

[Texasguy]

Can one buy this one-way valve separately, one that helps avoid vacuum injury?

 

[Bob DBF]

Interesting that you now need proof of certification in order to buy a hookah system.

Might just be a store policy as I can by all manner of scuba gear without proof of certification.

 

[Ghost95]

Why would a separate one way valve be needed? Doesn't the regulator act like a one way valve anyway? It seems like the seat would be pressed tighter to the orfice as the pressure in the hose decreases at depth. Am I wrong in my thinking?

 

[Bob DBF]

Why would a separate one way valve be needed? Doesn't the regulator act like a one way valve anyway? It seems like the seat would be pressed tighter to the orfice as the pressure in the hose decreases at depth. Am I wrong in my thinking?

It should, however it is not designed to be a check valve, so it might not work as well as you would want. Your choice.

I don't know how much negative pressure it would take to dislodge the seat, or cause some other failure in a second.

 

[halocline]

Why would a separate one way valve be needed? Doesn't the regulator act like a one way valve anyway? It seems like the seat would be pressed tighter to the orfice as the pressure in the hose decreases at depth. Am I wrong in my thinking?

That's an interesting point, it would work, I guess, right up until you tried to inhale. At that point you would collapse the the diaphragm which would mechanically push the lever and open the valve, and assuming the hose rupture was above the surface, the pressure in the hose would be ambient surface pressure, about 1 bar lower than what is in your breathing canal. So there would be suction, I just don't know how much or how dangerous. If the rupture was below the surface, then you'd be taking a nice little drink. Either way it doesn't sound very appealing. I guess the key here is that you only have a 25 ft hose, meaning it's not a huge pressure change and hopefully you are fit enough to get to the surface easily.

 

[Ghost95]

I was just thinking that the seat normally holds back the IP of 110 to maybe 150 psi. I doesn't seem like the 14 to 20 psi would present that much of a problem. Even if you inhaled and moved the seat the suction that has been mentioned would immediately close the second stage when you stopped. I never really thought about it before but I have used home built scuba hookahs before and none had a separate one way valve.

 

[Texasguy]

Is there an equation that would allow to calculate how deep down a regular 1st stage can supply pressure from the surface where it still be breathable at depth?

 

[iain/hsm]

Is there an equation that would allow to calculate how deep down a regular 1st stage can supply pressure from the surface where it still be breathable at depth?

Yes there is but before I tell you at this point you need to tell us what exactly your wanting to do and specifically what kit you intend using and the work involved. Swiming around 10 foot underwater slowly in clean clear water looking at fish or sandbagging an underwater pipeline 100 foot down for scour protection in zero viz at night are two very different proposals.

The photo below is a job going out next week with 32 metre umbilical.
The extra 2 metres is so your diver is not standing on his tip toes in a 30 more water column.
and gives a bit of extra length for snaking it around the deck before it goes over the side.

Next week were sending out a couple of 120 metre long 3 core umbilicals each with a 3/8 gas line, a 4 core comms line and a 1/4" pneumofathometer line for depth monitoring in a single 3 core twisted construction so I should be able if we have time to photo them both together.

 

[iain/hsm]

I was just thinking that the seat normally holds back the IP of 110 to maybe 150 psi. I doesn't seem like the 14 to 20 psi would present that much of a problem. Even if you inhaled and moved the seat the suction that has been mentioned would immediately close the second stage when you stopped. I never really thought about it before but I have used home built scuba hookahs before and none had a separate one way valve.

Yes standing on the deck your quite right if the line fails or someone opens a drain valve or a pressure fitting fails, then yes the umbilical releases the pressure and the diver if still on deck take a seat while the problem is fixed.

Now the same diver in 30 metres of water say wearing the popular Cressi full face mask with second stage fitted to the mask when the self same rapid leak happens now had one eye ball stuck to the right side glass of the mask glass while the other eyeball is stuck solid to the left hand side of the mask glass, with the rubber skirt of the mask sucked up so tight against his face a fleeting memory of how that guy died in the Alien film rapidly comes to mind before the panic sets it.

Yep now while his lungs straining not to collapse under the vacuum "pull" due to the pressure vacuum load wondering now what is going to happen when he eventually relaxes his lungs as the vaccum forces a very massive pneumothorax on his now collapsing lung and wondering why all those small parts of his lung alveoli tissue are rapidly being squished between his teeth.
What added with the stomach acid and all mixed with that crab he had for lunch before the dive.

No doubt wondering now if he has indeed enough time left on the planet before he is standing before his creator and giving an account of his life and that dive, wondering if his DAN insurance is going to cover the bill for all this mess or if he shoud have used a non return valve into the umbilical at the diver diver end. I dont know you call it.

Heck I hope that wasnt too grapic for the forum NSFW warning and all.

 

[Texasguy]

I am just researching for the hell of it, as a curiosity. No use is intended what so ever.