Tutorial: Scuba Power for Lindsay Airgraver

[brandvik]

Steve asked me to put up this “how to” for anyone who would like to power their Lindsay Airgraver by a scuba tank. I use this power supply because I live in the sticks, off the power grid. I have a good solar power system, but try not to tap into it too deeply. Running an air compressor to engrave is just not a viable option for me. So until Steve builds a solar powered Airgraver…

On the grid or off, there are several reasons you may want to add this mode of power as an additional option.

1. It can be a highly portable system.
2. No power is required which is great if you travel to shows or if your power goes out for an extended time.
3. A standard scuba tank is 80 cubic feet which will run your Airgraver for a long time. It only costs about $5 to fill a scuba tank.
4. It is very easy and inexpensive to accomplish.

Here is a photo of my system. This system has two 100 cubic foot tanks which will keep me engraving for several weeks at a time. It would work the same regardless of the size of the scuba tank you choose to employ.


Basically all you need is;
1. 1 scuba tank
2. 1 diver’s 1st stage regulator
3. A little plumbing

This system should work with any Lindsay Airgraver whether you have the foot pedal or the palm control.

As you can see, I have rigged this system up to my standard Lindsay air regulator.

The plumbing components are shown below all together laid out in the order they go. Sorry for the poor photo, but the detail photos are better.

1. Two hose clamps (shown only in detail photo)
2. One barbed fitting from the end of the hose which ships with the Airgraver.
3. One ½ inch pneumatic quick connect nipple (female)
4. One ½ inch pneumatic quick connect receiver (female)
5. One ½ inch scuba quick connect nipple (male)
This is a quick connect adapter for scuba. It fits into a It is a very common accessory in diving and any dive shop should have them. Divers screw these into an air chuck so they can use their scuba tank to fill a flat tire or whatever else one uses an air chuck for.
6. One quick connect scuba BCD hose.
This is another item every dive shop should have. It is the hose which goes from the regulator 1st stage regulator to the diver’s buoyancy control jacket.
7. One scuba 1st stage regulator.
Most dive shops have a bone yard with several of these. There are two types; piston and diaphragm. Either will work fine. I have tested both types to be sure. These regulators reduce the tank pressure down to a usable pressure of 150 to 200 psi.







Please note that the 150 to 200 psi coming off the 1st stage regulator is considerably higher pressure than your compressor is probably pushing. I have tried two types of 1st stages. One was pushing 180 psi and the other was pushing 200 psi. Both worked fine, but I did have to install hose clamps at both ends of the small hose feeding the Airgraver regulator because the hose popped off the barbed fittings after a while.

Most scuba tanks are designed for a working pressure of 3,000 psi but some are rated at 2,400 psi. For this application though, the important measure of a tank is its cubic foot storage capacity. 80 cubic foot is the most common but there are pony bottles like the black one in the photo below which are as small as 20 cubic foot. (one of these “pony” bottles is just visible in the first photo. It is the smaller black tank)

A 20oz (51 cubic inch) paintball CO2 bottle will last me about 6 hours at the bench, so my 200 cubic foot scuba system should give me 280 hours of bench time. That 280 hours of engraving for $10 worth of air.

Safety Note: 3,000 psi is a lot of kinetic energy, so handle these tanks with care. Never expose them to too much heat (above 130f). They should have a burst disk on the valve which is rated at five thirds the working pressure. So if you did forget and leave a full tank in the truck of your black car in August it won’t blow the lid off, but it will make an awful loud noise when the burst disk blows.

Store these tanks where they are unlikely to get knocked over or beat up. I once saw a high pressure cylinder go right through a wall when it got knocked over hard enough to break the valve neck.

I am searching for the proper high pressure adapters to rig the CO2 regulator for scuba power which will improve the portability of the system. I will post that in the future when I find the right adapter.

Until then, I am using this device to fill my little CO2 bottles from my scuba tank. (Much Cheaper!) http://www.scubamart.com/detail.aspx?ID=338
Safety Note: If you choose to do this also, make sure you monitor the pressure gauge on the fill adapter carefully. Most paintball tank have a working pressure of only 1800 psi.

BTW this "engraving bench" is actually on my front porch. I'm a building a shop but am a ways off from finishing it. The weather is great right now so its nice being outside anyway.

I hope some of you find this useful. Comments and questions are welcome.

[KurtB]

Excellent writeup, Jim, thank you for sharing with us. It really is amazing just how much air a scuba tank holds, and given the low air consumption of Steve's tools, this is a really viable way of foregoing a compressor, and creating some portability to boot.

Do you know offhand what the female thread is on the scuba first stage? On my own system there are multiple female thread ports, some high pressure, some low, and IIRC the industry standardized these threads some time ago, so you can swap mouthpieces + hoses, buoyancy compensating devices, and other air powered goodies, between systems. I'll take a look and see.

Neat setup!

[brandvik]

Originally Posted by KurtB

Do you know offhand what the female thread is on the scuba first stage? On my own system there are multiple female thread ports, some high pressure, some low,

Kurt, no I don't but the only port which is different (which is a larger diameter the others) is the high pressure port which is used for the pressure gauge. This port will probably almost certainly be marked with "HP" to indicate High Pressure (actual tank pressure). This is the whole reason the ports are sized different - to prevent someone from accidentaly running high pressure to a second stage or to a BCD. All the other ports expel what the dive industry refers to as "intermediate pressure" which is the 150 to 200 psi mentioned. Then the diver's second stage regulator delivers his air at whatever the ambient pressure is for the given depth. In our case the second stage is the engraver's adjustable regulator.

[Danny C]

What is an educated guess at the cost of this setup? That is for us that don't have anything at all and have to go buy 100%?

[brandvik]

Danny, I just went to Leasure Pro to check prices since I have been out of the business for almost a decade now. I used to hate these guys when I was competing with them. They are about the cheapest around. I found the following were the cheapest they had. I shopped their site as if I were going to be buying for myself from scatch.

Here's what I came up with.
80 CF tank. $149.95
The larger tanks like mine are expensive and as heavy as the dickens. I wouldn't go any smaller than 80 since most dive shops charge the same to fill a tank no matter its size.

Regulator $124.95 This one comes with the second stage regulator as which you will remove. (Just need a cresent wrench.) and replace with the quick connect hose.

Quick connect hose $19.95

Quick connect nipple $19.95 I would check your local dive shop for this as this sounds high to me.

I would check with your local dive shop regardless as they may have old stuff in their rental fleet that they would sell cheap. Plus you will need to make contact with them anyway since they will be the folks who will fill your tank(s).

The only cost I had for my setup was about $6 for the pneumatic quick connectors (Home Depot) and the hose clamps $2.00 (Napa Autoparts).

So the grand total if you were to buy everything brand new would be. $323.80.

Hope this helps. just let me know if anything is unclear.

[Danny C]

Thanks for the detail breakdown. That's about the same as a decent compressor and 1/3 the cost of a silentair. It would be a lot easier to fill than a full size Oxy tank (or equivalent) filled with nitrogen (that sucker should last about a month! Plus you have to have a place to put it.)

[Steve Lindsay]

Jim, Thank you so much for posting this info! Steve

[mckeenh]

Excellent info guys. I think this would be ideal for a show as there would be no noise to deal with. I also saw the tank mounted on a small hand truck in another post which would make it super simple to take any size tank to a show.

Neil

[airamp]

HI,

A Scuba tank is a very nice setup.

I am setting up a welding tank 80cf or 120cf tank. It is filled with compressed air or Nitrogen (your choice).
(DO NOT FILL TANKS WITH OXYGEN BIG BANG FACTOR).

I use one of these filled with compressed air for a breathing system when working with epoxy construction (airplane).

Note: To Filling scuba tanks at a dive shop you have to be certified to dive or they will not fill them up.
Scuba fills have moisture in the air so you do not dry out, can really mess up tools but better than compressors without a dryer system. (you still need a trap in the line). (round bottoms)

Welding tanks for a breathing system (compressed air) no problem if you tell them you need it for a compressed air system or what you are doing. (flat bottoms)

Nitrogen is no problem at all and no questions BEST CHOICE (for your health compared to CO2 and filling ease) since it in the highest percentage of the air on earth.

(you do not change the air around you when working, can make your lines go off)

Air Composition


The sea-level composition of air (in percent by volume at the temperature of 15°C and the pressure of 101325 Pa) is given below.


Name Symbol Percent by Volume
Nitrogen N2 78.084 %

Oxygen O2 20.9476 %

Argon Ar 0.934 %

Carbon Dioxide CO2 0.0314 %

Neon Ne 0.001818 %

Methane CH4 0.0002 %

Helium He 0.000524 %

Krypton Kr 0.000114 %

Hydrogen H2 0.00005 %

Xenon Xe 0.0000087 %




Note:The gas from a welding shop is MUCH DRYER than the scuba tanks filled at a dive shop so no trap and better for tools.

I have a welding regulator on it (they are 2 stage) to get the pressure to whatever you need for the airgraver manifold. (welding Oxygen regulator works great).

Gas has different fittings but these regulator fitting's can be changed.

The difference is cost. You can find tanks (40-240cu ft) at the welding supply house used for moderate prices or go on your local craigs list and pick them up for 50-100. and regulators (oxygen) (if you don't have spare welding equiptment).

All standard welding fittings.

Here is the link for the greatest buy sell link you will ever need and it is local in your area. Listing is free, yes free and they call and pick up the stuff you have for sale local.... You can get anything also CHEAP including scuba gear.

http://geo.craigslist.org/iso/us

YOU WILL BE AMAZED... WHAT YOU WILL FIND..

Remember to chain your tanks to a bench or wall. even small co2 tanks have 600 psi and the big boys (scuba and welding are at 2800psi) yes they do go though walls, cars, or anything that gets in there way if you hit the valve VERY HARD (very rare). Welding tanks have screw on steel caps to protect the valve use them when transporting tanks.

regards,
Dr. Mike

[Sam]

Airamp, you have it backwards about the moisture in scuba air. Moisture is removed from scuba air for a couple of reasons. The main reason is because when a normal air compressor is in use the high pressure air coming out the end has a oil and water mixed in. It doesn't become breathing air until it goes through the filtering system which removes the oil/water. A oil and water mixture doesn't work too well in your lungs. Too much oil/water can also make your regulators freeze up in cold water and corrode your tanks. if your getting that much moisture the dive store isn't changing his filters on a regular basis. the only dive shops that wouldn't remove a large amount of moisture would be one the runs a rix oilless compressor in a warmer climate.