Dive Hookah Regulator Question

[skipmac]

Originally Posted by Dsanduril

In principle I think we are pretty much in agreement.

I agree that we seem to be in agreement.

Originally Posted by Dsanduril

The IP of a SCUBA second stage is somewhere in the mid 100 pound range,

Except, I think you mean IP of the first stage?

Originally Posted by Dsanduril

and there is a fair amount of latitude in the adjustment of that IP.

Yep. I think I tested one of my first stages just to see how far it go and think I measured IP out from 85 to 160 psi.

Originally Posted by Dsanduril

However, most regulators make this adjustment by increasing or decreasing pressure on a spring by use of a threaded assembly.

I think one of my regs, maybe the Oceanic, used shims instead of a spring but it's been a while.

Originally Posted by Dsanduril

However, most regulators make this adjustment by increasing or decreasing pressure on a spring by use of a threaded assembly. At some point you run out of thread, and that is the lowest tension you can get. IME that is somewhere north of 100 pounds, but is depends on the regulator. Once you get to that point you have to put in a lighter spring, then you can adjust the regulator to lower pressures. A lot of hookah rigs work in the sub-100 range, you can get more air with less power from a cheaper compressor if you do. The downside is you need a larger diameter hose to move the same volume. Not uncommon however. As Keene says, theirs run at 30-50 pounds, and many others I have seen run 60-80. Most standard SCUBA springs just don't have enough adjustment to go that low.

Well never worked on a hookah and only used one once so no experience on the typical pressure output. The one time I used a hookah with two divers it was very obvious when both were inhaling at the same time, especially at the max depth. Work of breathing got noticeably more difficult.

[daddle]

Yes. As said above the hose holds several breaths if air. So running out of air is a slow process. Plenty of warning in a 50 foot hose.

[skipmac]

By the way, it might be good to mention to anyone thinking of building or buying a hookah that you are breathing compressed air under water.

Hookah diving is not the same as snorkeling.

Even if you are not going "very deep" at just 32', well within the range of most hookahs, you will be at double surface pressure.

If you aren't aware of the risks of rapid accent, holding your breath and the potential barotrauma it would be a good idea to take some basic diving classes.

[fstbttms]

Originally Posted by Dsanduril

The mod is a replacement of the spring in the second-stage that balances against the inlet pressure. Keene sells an awful lot of hookah equipment (Intro to Hooka!), this is what they have to say:



It's really not that hard, you don't need a professional dive shop, but you do need the proper spring.

It's not written in stone that you have to have a modified regulator. I know plenty of hull cleaners using standard, off-the-shelf 2nd stage regs with their hookahs.

[Dsanduril]

Originally Posted by skipmac

Except, I think you mean IP of the first stage?

IP out of the first stage is IP into the second stage, so tomato/tomato?

I think one of my regs, maybe the Oceanic, used shims instead of a spring but it's been a while.

This may be where we are talking to cross purposes, you can adjust the IP at the first stage, sometimes springs, sometimes shims, sometimes both. You also adjust the second stage balance to match the IP from the first stage, and that is what I was speaking of. Most of the second stage adjustments are some kind of screw, but I have seen shims there as well. In a full regulator tune-up you adjust both the IP at the first stage, and the balance against that IP at the second stage. There are a few (more expensive) regulators out there with self-balancing second stages, don't usually find those in hookah work.

[Nicholson58]

Originally Posted by resilientg

thanks for the posts so far, but no one seems to have touched on the question that was actually asked.

Matthew

Most of the Hookah type systems compress to a blow-off (releif valve) setting. A sophisticated system would charge a storage tank and unload the the compressor or shut it off once the tank was charged. With a gass engine compressor, shut-off is not as practical as an unloader valve. The reality is that they noramally run the system full out and let excess air bleed off over a relief valve. The single control device keeps the system simple even though you might save fuel using a more complex control system.

BTW - if you Google the topic of home-made or DIY dive systems you will find a lot of help on this topic.

[daddle]

The requirements for hull cleaning are easily met. 3 meters max. The rig I ordered was to work to 15 meters and for that they sold me some kind of boosted pressure setup. Looks the same. Same prices. I wanted to do anchor and mooring dives.

[skipmac]

Originally Posted by Dsanduril

IP out of the first stage is IP into the second stage, so tomato/tomato?

Exactly. Just once again my nit picking nature. Since the IP is set at and produced by the first stage I would refer to it as a first stage characteristic.

Originally Posted by Dsanduril

This may be where we are talking to cross purposes, you can adjust the IP at the first stage, sometimes springs, sometimes shims, sometimes both. You also adjust the second stage balance to match the IP from the first stage, and that is what I was speaking of. Most of the second stage adjustments are some kind of screw, but I have seen shims there as well. In a full regulator tune-up you adjust both the IP at the first stage, and the balance against that IP at the second stage. There are a few (more expensive) regulators out there with self-balancing second stages, don't usually find those in hookah work.

Don't think we are at cross purposes at all. I'm in complete agreement with all the above. The only comment I may add, since I have about 15 first and second stages that I used to interchange as needed I adjusted each independently but to the same specs. Most of my second stages do have a screw for fine tuning the cracking pressure so allows some leeway in the settings.

[hellosailor]

g-
"As the pump works at up to 150 psi and the regulator is around 60 psi, what happens with the extra pressure?"
Unless there are other arrangments, i.e. as Nicholson mentions, the extra pressure remains in the hose, stressing it, and in the compressor itself, which then wastes energy and produces excess heat. Unlikely to stall it out since the compressor is rated for that pressure and excess should "blow off" or blow past the seals. It is hard to guess without knowing just what the equipment is designed to do, but having a relief valve that allows excess pressure to blow off safely is probably the best and simplest solution.

Skipmac mentions barotrauma. In layman's terms...the human lung is not really intended to be a pressure vessel. And some lungs have weak spots in them, that are never a problem because they are never really dealing with pressure differentials. (Which is why your mother may have told you never to hold your nose trying to resist a sneeze.) All you need to do, when breathing compressed air, is take a really deep breath, hold it, and now rotate from a horizontal position to a vertical one. If your point of rotation was your feet (rather than your chest) you may raise your lungs vertically about four feet--and if you held your breath, that's enough to blow out a lung. Pop it like a cheap balloon.
So even with a hooka, SCUBA training may be in order, or at least, some familiarity with the concept of how to blow out a lung, or not.

Since the air in your lungs expands as you surface, even a partial lungful should be quite enough to get you from under a boat back to the surface, if your hooka quits. "Reserve" equiment of any kind is more likely to be a hinderance than a practical aid of any kind. But if you stay in any kind of water for 1/2 hour, odds are you are going to become cold and get banged around unless you're also wearing some kind of wetsuit, which adds a problem of added bouyancy, which means you may also need a weight belt. Take a deep breath and you get more bouyant, bobbing up and down, so there's also a learning curve about trying to maintain your bouyancy by not breathing too deeply. Again, SCUBA class might pay off.

[Dsanduril]

Originally Posted by hellosailor

g-
"As the pump works at up to 150 psi and the regulator is around 60 psi, what happens with the extra pressure?"
Unless there are other arrangments, i.e. as Nicholson mentions, the extra pressure remains in the hose, stressing it, and in the compressor itself, which then wastes energy and produces excess heat.

Actually, the regulator will free flow and just not work if it is designed for 60 pounds and you feed it 150 pounds. See the typical picture below:



Air comes down the hose and meets the red seal that sits against the orange/pink seat. If the area of that seat is 1/8 of a square inch and the regulator is designed for 60 psi then the force on the seat pushing to the left is about 7.5 pounds. To counteract this there is a spring (shown about the middle, around the yellow poppet) that counteracts this force. For discussion say this spring provides a force of 7.6 pounds. It then takes 0.1 pounds of force to open the seal. This force is supplied by the diver inhaling, pulling on the diaphragm, which in turn pushes on the grey lever that is connected to the poppet.

If you now connect this regulator to 150 psi source the force on the seat will be about 18.75 pounds. That means the spring now needs to provide about 19 pounds of counter force to keep the seat closed. If you only have spring that will provide 7.6 pounds then the seat will open all by itself and bleed air.

This regulator shows a thumb screw on the far left, the user can adjust the spring force by moving the head in/out, thereby shortening/lengthening the spring and adjusting the spring force. There is a limit to the amount of adjustment. If you have a 150 psi rated spring in the regulator and you supply 60 psi the diver will never be able to provide enough force to open the seal by breathing (but you could with the purge button). On the inverse, if you have a 60 psi rated spring you won't ever be able to get the seal to seat, because there is more force than the spring can overcome.

Some regulators have the external spring adjustment, some have internal. There are also other designs, but this spring/poppet/lever/diaphragm is the most common.

[skipmac]

Originally Posted by resilientg

As the pump works at up to 150 psi and the regulator is around 60 psi, what happens with the extra pressure?

Well I'm no expert on tool type compressors but the few I've used had a built in pressure switch that is adjustable. So when the compressor reaches the set psi it turns off. So set the pressure switch to a little over 60 psi and you're good to go.

[hellosailor]

"Actually, the regulator will free flow and just not work if it is designed for 60 pounds [maximum supply] and you feed it 150 pounds."

You're construing his question to mean the regulator can't take a supply greateer than 60 pounds. I'm reading the question as what happens if the regulator is set to deliver 60 pounds.

Only the OP knows which one he meant.

[chala]

Originally Posted by Blue Stocking

I would REALLY like to hear Fastbottoms (sp) on this. Serious.
I refuse to participate in marina work when divers are changing zincs.

Sorry to interrupt.
If you can oblige.

[fstbttms]

Originally Posted by chala

Originally Posted by Blue Stocking
I would REALLY like to hear Fastbottoms (sp) on this. Serious.
I refuse to participate in marina work when divers are changing zincs.


Sorry to interrupt.
If you can oblige.

Upon what am I supposed to offer up an opinion? I can find no posts by Blue Stocking in this thread.

[Nicholson58]

[QUOTE=hellosailor;1126342]g-
"As the pump works at up to 150 psi and the regulator is around 60 psi, what happens with the extra pressure?"
Unless there are other arrangments, i.e. as Nicholson mentions, the extra pressure remains in the hose, stressing it, and in the compressor itself, which then wastes energy and produces excess heat. Unlikely to stall it out since the compressor is rated for that pressure and excess should "blow off" or blow past the seals. It is hard to guess without knowing just what the equipment is designed to do, but having a relief valve that allows excess pressure to blow off safely is probably the best and simplest solution.


Sorry, I should have been more clear. The excess blows off at the compressor relief. It is not a problem to the hoses or regulator. If one is really concerned, it results only in excess fuel consumption. If you want to reduce this waste, the contorl circuit you need to add is:
unloader valve so excess capacity is vented at no pressure increase AND the motor throtle is reduced; check valve after the unloader to prevent back flow; storage tank to level out the pressure variations; pressure switch to toggle between unload and compress.

This is both, more complex (expensive) and prone to error and medling. Probably for these reasons the typical Hookah system is ON at full capacity no matter what the demand.