Thoughts on filling ones own tanks

[pensacoladiver]

25 foot Wellcraft sportfisher.

[pensacoladiver]

Thanks again Richard. That info on oil and contaminats is exactly what I was seeking.

[CaptnJack]

Oh well,I suppose only the military can determine that a new compressor is unusable. Did it not survive a jump or something?

25 foot Wellcraft sportfisher.

Got good tank ranks? That should a have decent load capacity, enough to carry tanks for a weekend at least. Probably more efficient than standing around for a couple hours filling tanks and pissing off the marina or anchorage neighbors. The Junior 2 is loud!

[dsteding]

25 foot Wellcraft sportfisher.

Twin 225 Mercuries?

[pensacoladiver]

apparently it simply didnt survive the ride from Oak Harbor to Ft Lewis... haha guys were telling me it had 0 hours on it and was new.

There is also a "military use" stipulation on certain items and this one was coded for "military use", which means that if no gov't agencies want it, it gets destroyed without the public having a chance to obtain it.

I can not even begin to guess why a SCUBA compressor would be coded "for military use" ??? Stranger things have happened though...

I have tank racks, but I actually prefer a simple wooden pallet structure I made to lay the tanks flat in the back of my truck. It works great in the boat and I can stack tanks pretty high on it.

[dsteding]

Ah, that is a shame--I was all excited for you. How often do such opportunities come up?

[Raydar]

apparently it simply didnt survive the ride from Oak Harbor to Ft Lewis... haha guys were telling me it had 0 hours on it and was new.

There is also a "military use" stipulation on certain items and this one was coded for "military use", which means that if no gov't agencies want it, it gets destroyed without the public having a chance to obtain it.

I can not even begin to guess why a SCUBA compressor would be coded "for military use" ??? Stranger things have happened though...

What?!?!? You think that somehow because it was purchased using gov't money that you should somehow be allowed to make use of it?

Silly taxpayer!


I picked up a small compressor when I bought the house for a couple reasons: Shops that I wanted to deal with at the time weren't handy and the fills that I wanted weren't inexpensive. Hence the compressor and T-bottles of He and O2 in the garage. Probably not going to ever break even with the compressor (especially if I don't dive), but being that compressors and storage tanks tend to hold their value, I can get back most of what I've got into it.

[pensacoladiver]

25 foot Wellcraft sportfisher.

Twin 225 Mercuries?

Naaa, just a single Yamaha 250 Fuel Injected. I can run it at 40 knots on a calm day with the engine trimmed all the way up.. not that theres ever a need to do those kind of things.

[pensacoladiver]

Ah, that is a shame--I was all excited for you. How often do such opportunities come up?

No kidding. They are out there. I just had my head up my a$* a little too long and didn't act quickly enough. Is there an icon for that? Should be.

[pensacoladiver]

Well, 2 and a half years since starting this post and I am now filling my own tanks.

I have been looking at compressors for about a year now and finally settled on a lightly used Bauer Oceanus with circa 5 CFM.

Had my Nitrox stick built over 2 weeks prior to picking up the compressor (Thanks Vance Harlow!)

I mixed up two 130 tanks today, one at 32 and one at 40. I can't believe I waited so long to get this project started.

Next stop... add some bank bottles and throw helium into the mix.

[kdupreez]

Congrats and well done!! Its a "liberating" experience aint it

How abouts you post some picks of your fill station?

BTW - I used to have a Bauer Mariner and have all the service manuals en pretty much everything you;d need for that compressor..

Also, hit me up on PM if you need filters or any help setting anything up

[pensacoladiver]

I received a few PM's so I'll put some pics below. sorry about the pic quality, they were taken with my phone.

First, if you are thinking of putting together a system, BUY THE OXYHACKER HANDBOOK.

I started by building an Oxycheq El Cheapo analyzer. It was easier than I thought and works like a champ! It is the black box above. I used the optional 10 turn pot for better adjustment during calibration. I am currently putting together another one to check the final mix in the tank. However, I pieced together all the little parts from different vendors and actually came in at just over $100 for the unit, including the sensor I bought from Add Helium... currently the cheapest place I could find the Teledyne R-17.

The mixing stick was a straightforward biuld from the Oxyhacker book. I used PVC caps and aluminum pieces inserted into the caps to mix the gas. Started off putting innertube around the caps for a snug fit, but that was a royal PITA so I just ended up wrapping electrical tape around them.... worked out GREAT. Got the top filter from my dad who is a lawn mower repair service owner, pays to have friends in low places.

The clear hose you see running from the stick to the compressor intake was about 4 feet long. It started to kink, so I just cut it down and moved the compressor under the stick. Now the hose is only about 8 inches long and is a straight shot to the intake.

I still need a flow meter for the oxygen regulator. Even with a 5 CFM compressor, barely cracking the regulator sends the output mix skyrocketing. Looking for a cheap flow meter as I type this.

Its not in the pictures, but I also have a fan blowing directly onto the compressor. Probably overkill....

the compressor came with a CO monitor strip and a Bauer B timer, the white box on the filter stack. It keeps track of relative humidity and run time and suggests when to change the filter.

It is suprisingly quiet! I can have a conversation right next to the unit while it is running.

[mz53480]

nice build, thanks for the info.

MZ

[kdupreez]

VERY COOL!!

Very nice job on that Nitrox stick too!!

Did you use any kind of flow restriction orifice on the O2 lines? You should be able to get by without a flow meter..

I used a 0.038" Orifice Diameter flow restrictor and with that in place on the welding O2 reg and with my 12CFM compressor I can jack the O2 regulator up to about 45-50psi for nice and perfect 32%!

Go get a stainless steel flow restrictor from McMaster Carr and put that directly on your regulator output and hook a NTPT to barb up and connect to your vinyl surgical tubing. http://www.mcmaster.com/#catalog/117/483/=f71t87

you might need to calculate your flow requirement.. for a 5CFM compressor, you'd need about 0.55 CFM of Oxygen at the intake for 32%.. so I'm guessing a 0.028" orifice diameter should be good at 40psi supply of O2 through your welding reg.. Then just adjust the welding reg up or down for higher or lower flow (aka richer/leaner Nitrox mix)

You can do the exact same to pump Trimix by just using maybe a slightly bigger orifice diameter for the helium and using only a single O2 sensor in the stick The trick is to calculate the "Starting Nitrox" mix before you will be adding helium.. The formula is IntakeO2% = TargetO2% / (1 - ppHe).. So if you want 21/35 you will need to adjust your intake Nitrox mix for 21 / (1 - 0.35) = 32.3%.. So start adding O2 till you get 32.3%, then start adding helium till you get a targeted 21% reading again.. now you have 21/35 at the intake

I can pump a solid 21/35 Trimix at 12 CFM without any problems! (I do have a flow meter for helium though)

Also.. If you are looking for "Aqua Environment" parts like one way valves, regulators, filters, PMV's, bleeders, etc, etc.. just PM me for more info, I'll hook you up.. (http://www.aquaenvironmentinc.com)

Same goes for Lawrence Factor products like Synthetic compressor oil, LF air filter cartridges, filter media, fill whip parts, etc.(http://www.lawrence-factor.com) - I'll get you squared away..

And for American made Bauer Compressor parts, LF has a sister company called "new parts" and you can browse schematics for your compressor online and find the exact parts you need, these guys are AWESOME!! (Again, PM me if you need anything!) (http://www.compressor-parts.com)

Then, I would very strongly suggest you send you air in for air quality testing, I have mine sent in at least 4 times per year.. the last place you want to discover a hickup with air is at 200ft If you dont have any air testing done at the moment, I can recommend "Trace Analytics" out of Texas. They are super fast with turn around! They send you a full and free test kit with 4 test tubes for air samples, you mail it off and they email you a air quality certificate.. (http://www.airchecklab.com)

You will find it VERY rewarding to pump your own breathing gas!! Well done!

And always remember, take care of your compressor and it will take care of you.. but, the adverse is also true!

Koos

[kdupreez]

OH - another awesome little mod to add onto your system that I found to be super useful, especially if you have air banks is an "auto off" switch that will shutdown the compressor when your banks are full..

Aqua Environment sells 0-6000psi pressure activated switches that you can use to interrupt your magnetic starter with..

Then even cooler, you can also add a solenoid on the output of you O2 welding reg, so when you start the compressor, it automatically starts the O2 flow set for 32%. and when you shut-off the compressor, it automatically shuts down the O2 flow as well

(http://www.grainger.com/Grainger/INGERS ... ting-4HN48)


Now you can pump 32% Nitrox at the push of a button and all will auto shutdown when it reaches a preset "max" pressure!

[pensacoladiver]

Koos, THANKS for the info. The Trimix tip is awesome. I will keep in touch as I start to get deeper into refining my system.

I actually ran across an O2 flow meter yesterday and the price was absolutely right.... free. It pays to have friends in low places.

I was able to pump anywhere between 21 and 40 with precision accuracy. Although to get to 40, the meter was all the way up and beyond the 15 LPM maximum mark on the meter, but I had precise control over it and that is what I was looking for.

Now I am waiting on my parts from McMaster-Carr to build my O2 transfill whip so I can PP oxygen into my 40 pony and then top it with 40% from the compressor. I have not calculated the numbers yet but I think it sound get me close to 80 percent for deco gas. It ain't 100 percent. George Irvine is gonna call me a stroke

You are right. It is liberating to not have to worry about getting to the dive shop for fills.

One question. As far as the CO monitor attached to the output of the filter, it is a paper strip inside a peephole. Is there a shelf life on those once they go into the system or do you just use it until it indicates CO (hopefully never). I have some extras but don't want to change it out if its not necessary.

Thanks!

[nwbobber]

Congratulations on your fill station. It seems like a good investment if you are dealing with mixed gases. I also purchased a small compressor like the original one mentioned in this thread. The nearest dive shop to me is 55 miles in the wrong direction. I got a bauer utilus 10, but I have to admit I was a bit uneducated as to the cost of the rest of the setup, so I have not got it set up yet.

One question. Bauer says this is not a continuous duty compressor, don't use it with banks. Now this doesn't make sense to me. The compressor has a priority valve on it, it is designed to pump at high pressure, so the issue must be time running/heat generated, if I'm not missing some other issue. It would seem you could use a small bank, if you only ran the machine for a max of say 40 minutes or so, letting it cool in between uses. Does this seem like a fair assessment, or am I missing something?

Someone also suggested to me that you could extend running time on the machine if an electric fan were used to augment the cooling air. Opinions?

[pensacoladiver]

I am not sure about the utilus 10. The Bauer dealer here in Ft Lauderdale said the Oceanus is a continuous duty compressor and has no problems filling banks. I do use a cheap box fan to blow additional air over the compressor whenever I have it running.

I don't have the bank bottles yet, but when I find some cheap, I am going to bank some Nitrox. I doubt I will ever run the compressor more than about an hour at a time though. If I were running a membrane system, I would want to keep it running once I got the mix dialed in, but using an external 02 sourse from a bottle, it is just too easy to start it up and dial the mix right into what I want. So no need really to keep the compressor running too long.

If you are a member of the Deco Stop, OC diver there has a great post about filling banks and the ration of HP to LP bottles you should have. He basically says that lots of LP are the way to go.

[CaptnJack]

Keep as many fans as possible, directed on critical cooling components like interstage cooling coils and 3rd stage head. It seems that most installed fans don't blow on these areas very well and there's no such thing as "too cool" when it comes to compressors.


(Actually there is but its more due to overly viscous oil on start-up. Depending on the oil somewhere about 40-45F is the lowest start-up temp. After its going it will make enough heat to keep the oil at appropriate viscosity.)

[pensacoladiver]

You can do the exact same to pump Trimix by just using maybe a slightly bigger orifice diameter for the helium and using only a single O2 sensor in the stick The trick is to calculate the "Starting Nitrox" mix before you will be adding helium.. The formula is IntakeO2% = TargetO2% / (1 - ppHe).. So if you want 21/35 you will need to adjust your intake Nitrox mix for 21 / (1 - 0.35) = 32.3%.. So start adding O2 till you get 32.3%, then start adding helium till you get a targeted 21% reading again.. now you have 21/35 at the intake

I can pump a solid 21/35 Trimix at 12 CFM without any problems! (I do have a flow meter for helium though)

Alright Koos,

I am just about ready to plumb my helium line into the Nitrox stick and do some single stick mixing like you mention above.

When you did this, did you have access to a trimix analyzer for your first few runs to verify your results? I think I already know the answer, but DAMN those things are expensive.

Also,

I have also noticed when pumping Nitrox, say 32%. the mix will hold steady at low tank pressures, like less than 1000 psi. But when tank pressure starts to go above 1000, I notice I have to make small decreases from time to time on the O2 flow meter, or the output mix will start to creep up. Thats not a problem with just one gas, but with Trimix there are now 2 variables. Have you experienced that and if so, how did you deal with it.

I would think that as the Nitrox percentage never seems to decrease, only increase... if the output O2 goes up, I have an o2 creep and need to decrease 02 coming in. If O2 output goes down, I would assume I have helium creep and need to decrease helium? Does this sound right?

It's damn expensive stuff to be playing with and screwing it all up.

I thought about PP blending the helium, but after I picked up a tank of UHP yesterday for $149, I decided I would rather be able to run it damn near empty but continuous mixing... as I dont have a booster... yet.

[CaptnJack]

If you don't have a helium analyzer continous blending is iffy. As you have discovered as the pressure comes up the blowby increases (with nitrox) and you have to adjust the inputs. Blowby is worse with trimix.

The good news is you can do what I did. Take a wine cork, drill a hole in the middle and shove a 1/4" or so HPDE tube through it. 12" long will do. Cut the cork to fit your compressor inlet filter hole. Duct tape a vegetable bag onto the free end sticking out your inlet filter. Put your O2 reg on your helium bottle (they have QDs right?). Dump everything out of your filters. Turn on the helium a little to inflate the vegetable bag. Now start the compressor. Crank up the reg to keep the vegetable bag partly full. Helium is so "thin" 3x or more will go through the same size orifice as your O2.

Your compressor is now pumping 100% helium delivered at ambient pressure with no ambient gas at all.

Figure out the volume in CF of your filtration. Using the tank factor of the tanks you are filling, stop the helium when you are "short" that volume of helium. Remove the vegetable bag/wine cork. Put the O2 reg back on your O2 supply. Don't forget to turn it back to its O2 setting. Turn on the compressor and top your tanks with 32%.

Your compressor will be fine pumping 100% helium. (Just don't do this with a Rix)

[pensacoladiver]

If you don't have a helium analyzer continous blending is iffy. As you have discovered as the pressure comes up the blowby increases (with nitrox) and you have to adjust the inputs. Blowby is worse with trimix.

The good news is you can do what I did. Take a wine cork, drill a hole in the middle and shove a 1/4" or so HPDE tube through it. 12" long will do. Cut the cork to fit your compressor inlet filter hole. Duct tape a vegetable bag onto the free end sticking out your inlet filter. Put your O2 reg on your helium bottle (they have QDs right?). Dump everything out of your filters. Turn on the helium a little to inflate the vegetable bag. Now start the compressor. Crank up the reg to keep the vegetable bag partly full. Helium is so "thin" 3x or more will go through the same size orifice as your O2.

Your compressor is now pumping 100% helium delivered at ambient pressure with no ambient gas at all.

Figure out the volume in CF of your filtration. Using the tank factor of the tanks you are filling, stop the helium when you are "short" that volume of helium. Remove the vegetable bag/wine cork. Put the O2 reg back on your O2 supply. Don't forget to turn it back to its O2 setting. Turn on the compressor and top your tanks with 32%.

Your compressor will be fine pumping 100% helium. (Just don't do this with a Rix)

That is a stroke of genius!!

I assume you are figuring out the filtration capacity so as not to waste the helium in the lines by purging it before puming the 32?

I had not thought of pumping pure helium through the compressor.

Thanks!

[CaptnJack]

If you don't have a helium analyzer continous blending is iffy. As you have discovered as the pressure comes up the blowby increases (with nitrox) and you have to adjust the inputs. Blowby is worse with trimix.

The good news is you can do what I did. Take a wine cork, drill a hole in the middle and shove a 1/4" or so HPDE tube through it. 12" long will do. Cut the cork to fit your compressor inlet filter hole. Duct tape a vegetable bag onto the free end sticking out your inlet filter. Put your O2 reg on your helium bottle (they have QDs right?). Dump everything out of your filters. Turn on the helium a little to inflate the vegetable bag. Now start the compressor. Crank up the reg to keep the vegetable bag partly full. Helium is so "thin" 3x or more will go through the same size orifice as your O2.

Your compressor is now pumping 100% helium delivered at ambient pressure with no ambient gas at all.

Figure out the volume in CF of your filtration. Using the tank factor of the tanks you are filling, stop the helium when you are "short" that volume of helium. Remove the vegetable bag/wine cork. Put the O2 reg back on your O2 supply. Don't forget to turn it back to its O2 setting. Turn on the compressor and top your tanks with 32%.

Your compressor will be fine pumping 100% helium. (Just don't do this with a Rix)

That is a stroke of genius!!

I assume you are figuring out the filtration capacity so as not to waste the helium in the lines by purging it before puming the 32?

I had not thought of pumping pure helium through the compressor.

Thanks!

Yeah at ~$0.50cf don't dump any just switch to topping with nitrox. Oxyhacker calls this bag method a "trash bag booster". Can also be used to consolidate a few partial fills in one tank. You many need a different reg to deliver enough trimix though. You can buy an inexpensive o2 reg on ebay and drill out the orifice for that.

Another way to CB trimix is to built 2 sticks. A premixer where He and ambient air are mixed with an O2 analyzer on that output. Then feed that stick to a second stick where the O2 is mixed in with a second analyzer at that output. Oxyhacker has plans for this dual O2 analyzer approach too.

[pensacoladiver]

Richard, Give me a little guidance on figuring out my filtration capacity. I would think I just use the standard volume for a cylinder.... pi (r)squared times the height

But I am probably fing that all up as I would imagine I need to take pressure into account. Whats the formula? I have 2 filters on the system, a Bauer PO and an AC130 Gunship hydraulic accumlator courtesy of sheldon sporting goods.

Do you just "swag" the capacity of the lines? I have 3 in the system and they are all 4 foot long.

[CaptnJack]

What's the total volume of your filters in cubic cms? (or cubic inches) You don't want to be pumping 100% helium at high pressure anyway so just figure the volume at 2500psi or so. You can ignore the lines or round up by a cf or two. The actual volume delivered will vary a bit with temperature anyway. But the helium fraction of trimix is not a precise science anyway. In the normoxic range plus minus 5% is acceptable.

Formula:
cubic cms * 0.00003531467 = X cf at 1 ata
2500psi/14.7psi = 170 atas
X cf @ 1 ata *170 atas = volume of filters in cf at 2500psi.

ps it helps to fill multiple tanks at once so errors and rounding are spread across a larger volume.