Where to Buy Cylinders + Other Questions from Compressor Newbie

[realdiver7]

Trying to find a good place to buy one 300 cf O2 cylinder and one or two 300 cf storage cylinders for banking 32-36% Nitrox. Is it OK to use cylinders for Nitrox that were previously used to bank nitrogen or helium?

I will be filling Worthington steel 100s at 3500 psi, so will my cylinders need to be 4500 psi rated? I'm new to compressors and mixing, so any info would be greatly appreciated. I have already ordered the Oxygen Hacker's Companion book, but waiting on it to arrive.

Thanks!

 

[dannobee]

Trying to find a good place to buy one 300 cf O2 cylinder and one or two 300 cf storage cylinders for banking 32-36% Nitrox. Is it OK to use cylinders for Nitrox that were previously used to bank nitrogen or helium?

I will be filling Worthington steel 100s at 3500 psi, so will my cylinders need to be 4500 psi rated? I'm new to compressors and mixing, so any info would be greatly appreciated. I have already ordered the Oxygen Hacker's Companion book, but waiting on it to arrive.

Thanks!

Yes, it'd be ok to use those cylinders. Obviously slowly empty any remaining gas. Emptying helium would be sacreligious to some though.

If available for sale in your area, BUY the O2 cylinder(s) instead of renting them.

 

[cool_hardware52]

Trying to find a good place to buy one 300 cf O2 cylinder and one or two 300 cf storage cylinders for banking 32-36% Nitrox. Is it OK to use cylinders for Nitrox that were previously used to bank nitrogen or helium?

I will be filling Worthington steel 100s at 3500 psi, so will my cylinders need to be 4500 psi rated? I'm new to compressors and mixing, so any info would be greatly appreciated. I have already ordered the Oxygen Hacker's Companion book, but waiting on it to arrive.

Thanks!

I'd suggest a blending class first. There's many ways to set up a fill station, and many ways to produce nitrox. A good blending class will clue you into the possibilities.

Here's a hint, if you have one 300 cuft bank bottle of say 32% at 4500 psi, how many empty 100's can you fill to 3442?

Tobin

 

[realdiver7]

I appreciate the replies so far. I know I'll need 4500 psi Nitrox storage cylinders, but will 2400 or 3500 psi cylinders be OK for the single O2 cylinder I will be buying for blending? I have one quote on a steel 300 cf (8500 liter) cylinder with a CG540 O2 valve, rated at 2400 psi.

I know I'm getting ahead of myself right now because I am a newbie to compressors, but I'm definitely not a newbie to diving and I've researched a lot of things, but apparently not enough on cylinders.

Thanks!

 

[cool_hardware52]

I appreciate the replies so far. I know I'll need 4500 psi Nitrox storage cylinders, but will 2400 or 3500 psi cylinders be OK for the single O2 cylinder I will be buying for blending? I have one quote on a steel 300 cf (8500 liter) cylinder with a CG540 O2 valve, rated at 2400 psi.

The answer is maybe. I assume you intend to use the O2 Bottle as a supply bottle. Can you even buy O2 pumped to more than 2400 PSI? Talk to your supplier. Will they fill customer bottles?

If you are planing on CBing 2400 psi O2 is fine.

As far as bank bottles are concerned a lot depends on how you plan to make Nitrox. If you are planning on banking PP blended Nitrox and are willing to bank 40% and blend 32% in your scuba tank from some banked gas + an air top, you may not even need 4500 psi bank bottles, a few 2400's and 3600's could be a better approach.

If you are Cbing 32% and want to be able to fill a few 100's without running your compressor you should consider a few 2400's, and a few 3600's and one 4500 psi bank bottle.

Here's just a quick comparison of two approaches:

Continuous Blending

Pros: No need for OCA, and almost complete use of your Purchased O2

Cons: Can't do any PP blending without OCA, (no mixes greater than ~40%) and you risk damage to your compressor. You also need to meter the O2 to your compressor, mix it (Nitrox stick) and you need at least on O2 Analyzer and sampling reg.

PP blending

Pros: Any % O2 you might want, limited only by the pressure of the supply bottle

Cons: You need OCA, and without a O2 booster you won't recover all of the O2 you buy.

Either way I see little value in banking enough mix to fill ~ one tank.

I'd keep the check book closed until after you take a blending class.


Tobin

 

[pescador775]

Realdiver, as suggested above, oxygen/gas suppliers may flat out refuse to fill a customer owned oxygen cylinder. Normally, they lease cylinders rated 2265 psi or 2400 psi. If you owned some special type of oxygen cylinder which was new, unused and needed it filled the gas guy might agree provided that his company inspect the interior beforehand. Probably one week turnaround on the fill. If you go in there with some raggedy, old welding tank they will probably fill (exchange) it no questions asked (kidding).

 

[realdiver7]

OK, great replies, and I thank you again. I should have provided more info in the beginning....I will be using a Nitrox stick already built, and will be doing continuous blending with some limited guidance from an experienced technician in the beginning of this compressor project.

Based on the answers above, it looks like the 2400 psi O2 tank is the standard and will be fine for this. I have an option of getting a 4500 psi O2 tank as well that holds 330 cf, instead of 300 cf so I am told by a salesperson today, but it's a lot more expensive. I was also under the incorrect assumption that I needed a 4500 psi bank cylinder in order to pump 3500 psi into a scuba cylinder, so I may not be as concerned now about the psi rating, and may focus more on the cf capacity.

By the way, my local O2 supplier will fill a customer-owned O2 cylinder, but he ships it out to another fill station for a $16.25 (total) delivery charge. I plan to purchase new, or as new cylinders and use them to fill a few 100 cf scuba cylinders so I won't have to run the compressor all of the time. I will more than likely stick with a new O2 cylinder and a new bank cylinder. I do not plan to pump Nitrox or air for any divers other than myself and my wife, so my operation will be a small one. It will also be a very slow one at only 3.5 cfm, but speed is not my goal with only 2-4 cylinders to fill in one evening after diving.

Other comments would be appreciated.

Thanks!

 

[pescador775]

Realdiver, read "hardwares" first post. You will need two 4500 psi storage cylinders for NITROX, IMO. Say that a 4500 psi tank holds 444 cf. Filling one empty 100 cf Scuba cylinder to approx 3500 will leave a single storage bottle with about 3500 psi. That is not a comfortable zone so it will need back up.
Nitrox & Compressor Accessories - Storage Tanks & Tank Racks

 

[cool_hardware52]

OK, great replies, and I thank you again. I should have provided more info in the beginning....I will be using a Nitrox stick already built, and will be doing continuous blending with some limited guidance from an experienced technician in the beginning of this compressor project.

Based on the answers above, it looks like the 2400 psi O2 tank is the standard and will be fine for this. I have an option of getting a 4500 psi O2 tank as well that holds 330 cf, instead of 300 cf so I am told by a salesperson today, but it's a lot more expensive. I was also under the incorrect assumption that I needed a 4500 psi bank cylinder in order to pump 3500 psi into a scuba cylinder, so I may not be as concerned now about the psi rating, and may focus more on the cf capacity.

If you are continuous blending there is NO reason to buy HP O2. 2400 is fine.

Ted Green has written more than once about how to configure banks. To para phase, you want a "pryamid". i.e. lots of volume at 2400 psi, a bit less at 3600, and a just little at 4500 or above.

A lot of the volume that you put into a scuba tank is below 1800 psi, which is practical to get out of 2400 psi bottles, a bit more of the volume is 1800-2400, which is practical to get out of 3600's and just a little of the volume is above 2400.

Why run your pump at 4500 when most of the volume you need is at a much lower pressure?

A single 300 cuft 4500 psi bank bottle won't fill one 100 cuft tank to 3442.....

Tobin

 

[pescador775]

Tobin, "realdiver" is only filling Scuba cylinders for personal use. Running the compressor in the 2000-4400 psi range is not relevant as to wear on the machinery so long as it is rated for HP continuous service and in good condition. However, if he gets a good deal on storage cylinders and has plenty of room, and doesn't mind hydro testing a bunch of low pressure bottles now and then, I suppose a staggered, "pyramid" setup might be an option.