Equalizing tanks

[elan]

what? that doesnt make sense.

if i was using my 40 cu tank, i could theoretically get 226cu ft out of my storage tank, 226 / 40 = 5.5 theoretical fills. But more likely 3 fills and a bit.

and thats the whole point of doing this, is so i dont have to have 10 extra bottles. If i have 2 or 3 main tanks, i could fill a 40cu 9 or 10 times without having to drive back or buy 9 more 40 cu's

(i obviously wont be filling them to 3000 psi, 2100 is fine though as i wont be more then 10 or 15 feet down and maximum bottom time isnt the goal. Dock repair is what it involves so ill be on the surface more often then not)

May be a hookah will serve you better for your dock repair?

 

[Ingolf]

What pressure will your vacuum pump pump to? You don't really want a traditional vacuum pump, we are dealing with input pressures of up to 2100psi (in this example) and output pressures from 3000-4000psi.

If you are asking questions like this then you probably are more than one weekend away from pulling it off safely. You need to grasp the relationship between pressure and volume, and how the gases equalize when connected.

Without a proper compressor or booster you won't get more than 2100 psi from the extra tank, with the amount falling a lot on subsequent dives.

The first dive, lets say you take the tank on your back to 100psi. You hook it up to the storage bottle you rented, and open all the valves on your whip, and two tanks. Gas moves back and forth until both bottles are at the same pressure. Lets say that pressure is 1900psi. You'll have taken about 60 cubic feet of gas out of the storage tank and put it in your scuba tank.

Next dive, you do the same thing, but now they equalize at 1600psi and you only put 45 cubic feet in your tank.

Third dive they are at 1200psi and you only put 30 cubic feet in your tank.

Of course those numbers are just wild guesses, but they illustrate the concept.

With a booster (a compressor which can accept an input pressure significantly higher than ambient and go all the way to 0) you can use the storage bottle at a lower pressure and fill the scuba tank to the proper fill. However, you will also need a third drive gas at a lower pressure but at a very high volume, to run the booster.

It might be cheaper to buy a small portable compressor, but then you have to educate yourself on not only the equalization stuff, but also filters and maintenance. For most "casual" divers it's simplest to buy a few extra scuba tanks. Also, consider the amount of space and weight that the fill setup will take up.

Remember, pressurized gases contain immense amounts of potential energy, and breathing gas impurities can be fatal. It's not rocket science, but it is very important to be careful, safe, and understand what you are doing.

Excellent, thank you. perfect response, thats pretty much what i wanted to know but im trying to figure out what equations i should be using to determine how much psi ill have for each continuous fill.

i understand i am not gonna get over 2100 psi.

---------- Post Merged at 06:52 PM ---------- Previous Post was at 06:50 PM ----------

May be a hookah will serve you better for your dock repair?

the one we had got stolen. were doing this setup temp until we can get a new 3,000$ unit.





10$ to rent a tank with 30$ fills is most economical right now

 

[redacted]

what? that doesnt make sense.

if i was using my 40 cu tank, i could theoretically get 226cu ft out of my storage tank, 226 / 40 = 5.5 theoretical fills. But more likely 3 fills and a bit.

and thats the whole point of doing this, is so i dont have to have 10 extra bottles. If i have 2 or 3 main tanks, i could fill a 40cu 9 or 10 times without having to drive back or buy 9 more 40 cu's

(i obviously wont be filling them to 3000 psi, 2100 is fine though as i wont be more then 10 or 15 feet down and maximum bottom time isnt the goal. Dock repair is what it involves so ill be on the surface more often then not)

You will not be filling them to 2100 either. The first Al40 equalization fill will give you about 1890 psi or 25 cu ft. The 2nd will get 1660 psi or 22 cu ft. The 3rd will be 1480 psi or 20 cu ft. So you will have gotten about 67 cu ft out of your 226 cu ft tank @ 2100 psi leaving about 150 cu ft in that tank at 1480 psi.

At such a shallow depth, you can probably get about 1.5 hours of dock repair work in. You could rent one full AL80 and do about the same thing.

 

[Scared Silly]

About as long as it takes for water to flow north in the Mississippi.

That would be about 200 years to be exact as 1812 that was the last time old man river flowed north. Do a search on New Madrid Fault Zone.


For the OP read up on Boyle's Law and learn about cascade systems.

 

[whaylonsmithers]

From a different angle, have you explored the possibility of putting a regulator on the storage tank and running a hookah line to where you're working? I have no idea if this is legal/possible/adviseable (thoughts anyone?) but it seems plausible from the comfort of my warm dry couch.

6.4 (cu meters) = 226.013867 cu feet

 

[Rich Keller]

From a different angle, have you explored the possibility of putting a regulator on the storage tank and running a hookah line to where you're working? I have no idea if this is legal/possible/adviseable (thoughts anyone?) but it seems plausible from the comfort of my warm dry couch.

This will work better than using a scuba tank. You are now breathing off a tank bigger than most sets of doubles available and you can dive without a tank on your back making it much easier to work. If you do use the cascade method of filling tanks you want to use them one at a time and always in the same order. This way the last tank in the cascade will always have the highest pressure for the longest amount of time.

 

[Doppler]

Try this

Cascade Air Bank Calculator for Scuba and paint ball

 

[Graeme Tolton]

From a different angle, have you explored the possibility of putting a regulator on the storage tank and running a hookah line to where you're working? I have no idea if this is legal/possible/adviseable (thoughts anyone?) but it seems plausible from the comfort of my warm dry couch.

Commercial divers do this every day. Would be best option providing all regulators and hoses are apropriate for breathing air. A medical regulator would probably be best bet. This way you can get most of the 226 cubic feet from the k bottle.

 

[Teknadv3x]

Unless your pump is rated for a few thousand psi, you're not going to get anything but injuries out of the deal. .

LOL

Dave