PADI open water max depth

[Darnold9999]

John:

That's pretty much the longer version of the conversation. But without the discussion of that might be why the tanks are designed to that size.

I do wish I had kept my old steel tank, but it sat in multiple closets for 15 years and I never used it so I tossed it about 5 years ago. When I tossed it still had pressure in it from the last dive so I suspect it was a perfectly good tank. (I vented the air before tossing it.) Thought I would never dive cold again.

 

[John C. Ratliff]

John:

That's pretty much the longer version of the conversation. But without the discussion of that might be why the tanks are designed to that size...

Darnold999,

I knew you knew the reason for the tank size, but I wanted to go through the calculation so others could see it. Concerning the real reason for standardizing on the 71.2 cubic foot cylinder, this is from Let's Go Diving by Bill Barada, 1962:

...The standard, single cylinder is termed the "single 70" because it contains 71.2 cu. ft. of air. The reason for this standard capacity is discussed iin the chapter under Medical Aspects of Diving, in the section on "The Bends."...

6. Cylinders and Decompression
Standard, single, 71.2 cu. ft. cylinders are calibrated to give the average diver a supply of air within the limits of "no decompression" dives. Calibrations are based on a breathing rate of 3/4 cu. ft. per minute. At this rate, the standard cylinder will be out of air before decompression times are reached. However, the rate of breathing varies greatly between individuals, and the cylinder capacity is never a guage. Extreme care should be exercised when using double or triple cylinders, with a total capacity of more than 80 cu. ft. With these units, a diver must be constantly alert to the depth and time he is submerged, because the capacity permits dives of durations requiring decompression.

That is one of the more definative sources in the industry.

SeaRat

 

[Darnold9999]

Sorry John, I actually didn't know that. I suspected it, and your answer and subsequent post confirms it. Was thanking you. This writing stuff is hard, conversation is much easier, I can tell when what I say is misunderstood in person when I write the bandwith is too narrow - can't wave my arms about draw pictures etc.

I think it is worth going through the math and even understanding it:11doh: , not sure it is done anymore in basic courses.

 

[shelbyj]

I know this thread is old, but I have some new experiences to attach to the line- the card matters to indoor dive pools in Europe! There is a famous 30-meter deep indoor dive pool in Brussels that has dive police! The water is an attractive, balmy 30 degrees that entices me to visit often in the winter months, but I can never go deeper than 18 meters. My card says "PADI Open Water Diver," and, to the dive pool, that spells out the letter of the law. I suppose there is a reason for this- log books are not standards, so it is my card that counts.

 

[kaerius]

Easy fix, take some con ed, even a single deep adventure dive gets you a certification depth limit of 30 meters.