US cylinders,sizes,pressures?

String · Jun 16, 2005

Just after some clarification here.
Im off to florida this month and hope to get a few days diving in. Im in the process of making notes/laminates to give a quick imperial<>metric conversion and other things.

What is a common size backgas cylinder used in the USA (in particular the keys)? Are these steel or aluminium ? What is the "standard" full pressure of these? Also, What is the usual "be back on the boat with xxxx psi" pressure operators tend to use ?

All my gauges are in metric, computer is staying set to metric, tables in metric etc so i need this sort of thing to work out what im breathing from and what guides to follow.

Rick Murchison · Jun 16, 2005

String:
Just after some clarification here.
Im off to florida this month and hope to get a few days diving in. Im in the process of making notes/laminates to give a quick imperial<>metric conversion and other things.

What is a common size backgas cylinder used in the USA (in particular the keys)? Are these steel or aluminium ? What is the "standard" full pressure of these? Also, What is the usual "be back on the boat with xxxx psi" pressure operators tend to use ?

All my gauges are in metric, computer is staying set to metric, tables in metric etc so i need this sort of thing to work out what im breathing from and what guides to follow.

Well... we measure things differently here, and it can be a bit confusing. For example, we have the same 16L tank rated at 104CF and 130CF depending on whether it's a LP or a new "E-series" tank.
Our system rates the tank size at how much room temperature 1ATA air you can stuff into the tank at its rated service pressure (+ 10% for LP steels).
Our "AL80" (the most common rental tank over here) for example, holds 77.4 CF at 3000 psi - it's interior volume is a hair under 0.4CF, or about 11 L.
Clear enough?

Rick

Kim · Jun 16, 2005

I started a thread about this quite recently - there is a lot of information in it:
http://www.scubaboard.com/showthread.php?t=99322

Rick Murchison · Jun 16, 2005

The "standard" tank here for rental in the recreational Scuba industry is the AL 80. The "standard" is to be back on board with 500 psi, which is about 35 bar. Normal fill is 3000 psi or about 204 bar.
Rick

String · Jun 16, 2005

OK 80-cu ft at 3000psi is about an 11.1l tank underfilled to 206.8 bar. Standard here are 12.2/232bar or 15l/232 bar (steel)

So im going to be diving on smaller tanks than normal. Out of interest why is aluminium used so commonly ?

Found lots of people saying that "be back on the boat with 500psi" is common - thats about 35 bar. We tend to use 50 bar (725psi) so thats something else to get used to.

As all my gauges/computer are in the system i know then it was only the tank size i needed to adjust to so should be fine.

Kim: useful thread, not quite sure how i missed that on a search.

Rick Murchison · Jun 16, 2005

String:
Out of interest why is aluminium used so commonly ?

$$$ of course. An AL80 is about half the cost of a Steel 85.
Rick

String · Jun 16, 2005

Aha as simple as that

Was expecting some other technical reason.

Don Burke · Jun 16, 2005

String:
Out of interest why is aluminium used so commonly ?

They are fairly cheap and maintenance is easy.

Aluminum tanks also often put the diver in a better situation regarding ditchable weight, which can be very handy when dealing with students or new divers.

String · Jun 16, 2005

Tend to work the opposite way here with thick exposure protection - Any positive buoyancy in a cylinder means yet more lead is needed to be carried somewhere to sink the thing.

Rick Murchison · Jun 16, 2005

Next question for you String. Are all your regs DIN? If so, since most all rental tanks here are yoke "K" valves, you'll need a DIN-to-yoke converter.
Rick

US cylinders,sizes,pressures?

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