In an O2 fill desert

[Still Kicking]

Inevitably, tech diving increases hassle factors such as gas fills, trip logistics etc. You can mitigate some of these issues by investing in your own infrastructure (boosters, compressors, storage bottles etc.) If you are not prepared to jump through a lot of hoops and/or spend large quantities of cash, tech diving may not be the game for you. When I looked at the costs/risk/reward equation, I decided it wasn't for me.

 

[Celt]

Alas, as ever, 100%'s off the menu unless the source cylinder's full or you've a $$$ booster

Top up with air for nitrox, decant with a bank for 100% you don’t need 220 bar for deco

 

[Wibble]

Inevitably, tech diving increases hassle factors such as gas fills, trip logistics etc. You can mitigate some of these issues by investing in your own infrastructure (boosters, compressors, storage bottles etc.) If you are not prepared to jump through a lot of hoops and/or spend large quantities of cash, tech diving may not be the game for you. When I looked at the costs/risk/reward equation, I decided it wasn't for me.

In my 6ish years of tech diving, I've not found it to be that bad. But you are tied to where you get the gas. As has been said ad-nausium, high pressure oxygen is the difficult one to get as few places have a booster. Tweaking your decompression gas makes life much easier, such as using 80% rather than 100% and topping off with air, so adapting your profiles (e.g. 70% when an 80% fill's topped off).

When I moved to a rebreather I ended up re-purposing my three twinsets as gas banks to decant into the 3-litre rebreather cylinders. I keep these twinsets filled with 100%, air and 10/75 trimix (very rich trimix; can decant and mix for a much lower helium content for 40m to 50m dives). These banks last quite a few dives before needing refilling, at which point I'll drag them over to my "gas dealer" for filling. It also helps to have a couple of sets of rebreather cylinders so you've a weekend's worth of gas to hand.

Doing a bailout's a pain though as the cylinder will need to be oxygen cleaned and put back into test!


Anyway, open circuit's not too bad, but you do tend to collect cylinders. Depending on who fills them sets the cost. My local dive shop also tests cylinders, needless to say they're very strict on checking the test dates...

At some point it'll become more viable to look at my own booster and compressor, simply to stop the testing fees.

 

[tbone1004]

Drive gas…. Best to use a cheap garage compressor? Will they work OK?

had a couple threads recently on this, but basically you can't practically put a compressor in your house that will run a full size Haskel at rated rates *they can consume over 70cfm at close to 150psi if you keep them cycling at 1cycle/second which would take a ~20hp compressors which is a monstrous beast*. You can get away with standard shop compressors, they just run slow and need adequate filtration best served by an active chiller.

Compressors like the Kobalt Quiet Tech, California Air Tools, etc. anything that's labeled "ultra quiet" will require less filtration, but you still want a refrigerated air drier if you're going to use it regularly. All in all budget about $1500 to get a quality compressor, air drier, filters, and misc fittings for the drive side.
If you own your own compressor, the LP drive is about a tenth of the cost to run/maintain than running it off of a scuba compressor so it is well worth it. If nothing else, the scuba compressors are about 1:1 in terms of HP:CFM where a LP compressor is about 1:4, then add in the oil/filter changes and it makes a lot more sense to run it off of the LP compressors. Where people get stuck though is that these are designed to run from huge industrial compressors that all have chilled water drying and heavy duty filters to make sure that they are fed clean and dry gas and very few home compressors have those fitted.

 

[Marie13]

Inevitably, tech diving increases hassle factors such as gas fills, trip logistics etc. You can mitigate some of these issues by investing in your own infrastructure (boosters, compressors, storage bottles etc.) If you are not prepared to jump through a lot of hoops and/or spend large quantities of cash, tech diving may not be the game for you. When I looked at the costs/risk/reward equation, I decided it wasn't for me.

One would think in an area of this size there would be more O2 sources. Luckily the shop where I get helium just got a booster latest summer.

You folks seem to think that getting one’s own compressor is the solution to all diving evils. I live in a small one bedroom rented condo. No garage. I don’t have the mechanical skills to mess around with a compressor if it breaks - see some recent threads on that.

 

[Wibble]

had a couple threads recently on this, but basically you can't practically put a compressor in your house that will run a full size Haskel at rated rates *they can consume over 70cfm at close to 150psi if you keep them cycling at 1cycle/second which would take a ~20hp compressors which is a monstrous beast*. You can get away with standard shop compressors, they just run slow and need adequate filtration best served by an active chiller.

Compressors like the Kobalt Quiet Tech, California Air Tools, etc. anything that's labeled "ultra quiet" will require less filtration, but you still want a refrigerated air drier if you're going to use it regularly. All in all budget about $1500 to get a quality compressor, air drier, filters, and misc fittings for the drive side.
If you own your own compressor, the LP drive is about a tenth of the cost to run/maintain than running it off of a scuba compressor so it is well worth it. If nothing else, the scuba compressors are about 1:1 in terms of HP:CFM where a LP compressor is about 1:4, then add in the oil/filter changes and it makes a lot more sense to run it off of the LP compressors. Where people get stuck though is that these are designed to run from huge industrial compressors that all have chilled water drying and heavy duty filters to make sure that they are fed clean and dry gas and very few home compressors have those fitted.

For a single diver, it kind of makes it easier to stick with the status quo; keep banking cylinders topped off with periodic trips to the gas dealer. One forgets how complex a booster is and its thirst for drive gas. Definitely not the cheap option.

One thought... That daft automatic buoyancy device thing discussed in another thread. If only it were possible to get "liners" for dive cylinders and pump in high pressure water to increase the pressure of the remaining gas. Imagine a 12 litre cylinder down at 150 bar; pump in the HP water to halve the capacity to 6 litres and instantly there's 300 bar available.

Somewhat better than the stupid "auto" buoyancy device. Kind of implies that the pump will be small enough to run on a small battery (you should tell that's cynicism with a dose of sarcasm).

Challenge for them. Can you do me a pressure booster and throw away the wing crap so I can boost up my 3 litre rebreather cylinders from a half-empty bank.

 

[broncobowsher]

had a couple threads recently on this, but basically you can't practically put a compressor in your house that will run a full size Haskel at rated rates *they can consume over 70cfm at close to 150psi if you keep them cycling at 1cycle/second which would take a ~20hp compressors which is a monstrous beast*. You can get away with standard shop compressors, they just run slow and need adequate filtration best served by an active chiller.

Compressors like the Kobalt Quiet Tech, California Air Tools, etc. anything that's labeled "ultra quiet" will require less filtration, but you still want a refrigerated air drier if you're going to use it regularly. All in all budget about $1500 to get a quality compressor, air drier, filters, and misc fittings for the drive side.
If you own your own compressor, the LP drive is about a tenth of the cost to run/maintain than running it off of a scuba compressor so it is well worth it. If nothing else, the scuba compressors are about 1:1 in terms of HP:CFM where a LP compressor is about 1:4, then add in the oil/filter changes and it makes a lot more sense to run it off of the LP compressors. Where people get stuck though is that these are designed to run from huge industrial compressors that all have chilled water drying and heavy duty filters to make sure that they are fed clean and dry gas and very few home compressors have those fitted.

Doesn't need to be that big of a compressor. My 5HP IR 2-stage is no where near maxed out. Never timed it, but it feels to be a little less than 50% duty cycle. But I also have the Haskel running slow. About half speed, 1 cycle every 2 seconds. Trying to keep the heat down in the little rebreather bottles.

But it does need to be a fairly large compressor with a really good duty cycle rating. A little $100 pancake compressor might work for a framer or a roofer but it will never keep up with a booster.

 

[Tracy]

One would think in an area of this size there would be more O2 sources. Luckily the shop where I get helium just got a booster latest summer.

You are moving into a tiny subset of a tiny hobby. Catering to technical diving doesn't make financial sense if you are going to dabble. There can be money made, but you have to be in that vein for it to be profitable.

 

[tbone1004]

Doesn't need to be that big of a compressor. My 5HP IR 2-stage is no where near maxed out. Never timed it, but it feels to be a little less than 50% duty cycle. But I also have the Haskel running slow. About half speed, 1 cycle every 2 seconds. Trying to keep the heat down in the little rebreather bottles.

But it does need to be a fairly large compressor with a really good duty cycle rating. A little $100 pancake compressor might work for a framer or a roofer but it will never keep up with a booster.

that's why I prefaced with "if you run it at rated speed", any compressor that is rated for continuous duty can run the boosters, but it needs to be rated for continuous duty and the high rpm oil-less compressors are certainly not. Speed is really only an issue with filling big deco bottles and/or when the supply bottle gets low.

@Tracy is right about technical divers though, we are not profitable unless you are in a heavy area for technical diving. A dive shop running a haskel is almost guaranteed to be losing money on O2 fills given the high purchase cost, high maintenance cost, and high running cost. Most don't run their shops like a real business so they don't do the ROI calculations and buy a Masterline for $12k which is a much better investment, but even then the ROI is probably a decade for anything but the high volume shops or ones that want one for their personal diving.

 

[kensuf]

Copper wire was invented by two technical divers fighting over a penny. Everyone wants a deal, in a small market with a bunch of people looking for that deal, catering to tech divers may be more hassle than it would be worth. Add the litigious nature of American society, and yeah all that.