I'm about to go on my first trip to Indonesia. In response to my request for a "63" tank, the dive shop has offered a 10 litre. My efforts to convert the two measures have left me breathless. Are these tanks comparable? What else should I ask them? Thank you.
Tank sizes in Indonesian
- Thread starter johnsonju
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bleeb
Contributor
Did they mention working pressure? Maybe you already knew this, but in parts of the world that dive in metric, tanks are rated by their empty internal volume. Depending on exact make, an LP 10 L (approximate) tank filled to 2400 psi holds about 65 cu.ft., while an HP and/or aluminum tank at 3000 psi holds about 72 cu.ft. Are these steel or aluminum, not that that affects the amount of gas?
If you're renting equipment from them, another question might be whether their pressure and depth gauges are imperial or metric.
Getting off the topic, you may also want to ask about what safety equipment they have on their boats and the training of their personnel. And based on some of the other discussions going around these days, you may also want to ask them how often they test their air, or whether they monitor the CO content of every fill.
If you're renting equipment from them, another question might be whether their pressure and depth gauges are imperial or metric.
Getting off the topic, you may also want to ask about what safety equipment they have on their boats and the training of their personnel. And based on some of the other discussions going around these days, you may also want to ask them how often they test their air, or whether they monitor the CO content of every fill.
The tank sizes we (in the US) are accustomed to using are referenced to the volume of gas contained in the cylinder at the working pressure (e.g. 2400psi, or 3000psi, or 3442psi). Much of the rest of the world uses tank sizes referenced to the volume of gas contained in the cylinder at ambient pressure (e.g. 1 atmosphere, or 14.7psi). To determine the volume of gas available in the tank you are being offered for diving in Indonesia, convert 10 liters to an equivalent volume in cubic feet, at ambient pressure, which turns out to be ~0.353 cf. Then, multiply that volume by the number of atmospheres of pressure to which it will subjected at the working pressure of the particular tank (e.g. multiply it by the working pressure, divided by 14.7psi), and you get an idea of the volume of gas you will have when filled. So, a 10 litre cylinder, filled to 2640psi, would provide ~63 cf. Some additional conversions are shown below:
10 litre tank = 0.353146 cf
2250psi = 54cf; 2400psi = 58cf; 2640psi = 63cf
3000psi = 72cf; 3300psi = 78cf; 3442psi = 83cf
Very good point!bleeb:
Aluminum 80's, and 63's are pretty much the standards everywhere I have dived over there. Most of the gauges are metric. Usually a full tank is filled to 200 Bar (pretty darn close to 3000 PSI). I did not see any steel tanks in Thailand, or Indonesia.
Thank you all for the very helpful information --in particular, I'm grateful for the "heads up" on other questions to ask and the examples of how to use the conversion formula. (It really helps to see it used.) I now feel better prepared to send an email to the dive shop I'm using, asking some more questions. I've also picked some "key numbers" to memorize, such as my maximum depth in meters, and "turn around" and "need to ascend" times in "bars!"
JJ
JJ
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