CO2 Tanks for On-Board AIR (OBA)

[thecodemonk]

First, let's establish some basics...

 

What is a CO2 tank?

These are metal tanks resembling scuba tanks but contain mostly liquid carbon-dioxide (CO2) with some empty space at the top for it to expand into a gas. 

(WARNING: do NOT use a scuba tank for liquid CO2.  Use bottles certified for CO2, which can have an internal pressure of 860+ PSI.)

 

For an idea of general appearance and size...common tank sizes and dimensions are shown here: (stolen from google but hosted here so links don't break)

 

 

Is CO2 really that useful?

I think so and find it much more convenient than a traditional OBA pump setup.  CO2 can be used anywhere that I would use pressurized air.

 

Common examples include:

- Adding air to tires

- Running air-powered tools (such as an air-powered impact)

- Locking or unlocking air-powered lockers (such as ARB lockers)

- Blowing up my kid's inflatable pool

- Blowing dust off the ground with an air nozzle.

- Giving my hair a wind-swept look

 

 

Why use CO2?  Why not just use a tank filled with air?

Liquid CO2 is also very compact for how much gas/air you can get out of it.  An example of this is that 2lbs of liquid CO2 can expand to about 20 cubic feet of volume when converted to a gas (the natural state it wants to be almost anywhere on earth).  That's much more air than the tank would otherwise hold if it were only gas.

 

To put it into a more practical measurement, you can get an idea of how many tires you can fill up with different tank capacities using this chart: (each tank capacity is measured in lbs of CO2…so PT05 is 5 lbs, PT10 is 10 lbs, etc) 

Source: https://powertank.com/pages/tire-air-up-chart

 

 

Where can I even get CO2?

Liquid CO2 is much more common than many realize.  It's used in welding (usually in a two tank setup alongside another inert gas like argon) and is available at almost any welding supply store.  It's also used for some HVAC technician tools and for carbonating beverages.  Anyone participating in any of those kinds of activities will likely want CO2 and will have a way to get it.

 

It's also pretty cheap...the welding shop will swap or fill up my existing 10lbs bottle for $20.

 

 

How do I use CO2?

One of the most important thing to keep in mind is how much pressure you need.  Since CO2 tanks can put out over 800PSI (in 70 degree weather...a little less in colder climates), you'll need something to regulate that down in almost any situation (ARB lockers like between 100-150 PSI, air impact wrenches like between 90-100 PSI, etc).

 

Options for regulators are as varied as you'd imagine (with more features/convenience costing more). 

- Full kits, like the ones produced by PowerTank or Smittybilt, include regulators that have a gauge or two and some adjustment.  

- For DIY setups, you can go one of two ways...static regulators (cheaper and simpler) and adjustable regulators (more flexible and more money).

 

For many, a DIY regulator set to 150 PSI or so is perfect and is a very inexpensive way to go.  Attach it to the bottle with an air-chuck attached to the other end and you're good to go.  These are also usually available at those same welding shops (you can find them on amazon too but I trust my local shops to give me quality items and stand by them more than I trust amazon sellers).

 

You can spend some more money and get gauges and an adjustable regulator if you want to be able to visually tune the amount of pressure you're giving (as well as the pressure in the bottle). You can even go all out and setup a whole piping setup with different pressures going to different things...a bit more PSI your air chuck to fill up tires, less to your air lockers, etc.

 

I went with a dual gauge adjustable regulator setup...one gauge reads the bottle pressure, one reads the output pressure.  As a note, bottle pressure is largely useless until the bottle is almost completely empty.  I just like gauges.

Source: How much PSI do you have in a full CO2 tank? | Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum

 

Note: As you can see in the picture, it's kindof important for the bottle to be upright when you use it. You can store it in just about any orientation, but before you crack the valve, make sure it's upright.

 

 

Ok, but why would use a CO2 tank?

The short answer is: Speed and Flexibility.

 

Speed: CO2 tanks, as mentioned above, can put out a lot of continuous air and a lot of PSI.  That means I can run my tools longer than most OBA setups and fill much larger tires faster without having to wait for a pump to refill a tank.

 

Flexibility: My air source is not tied to my rig and is pretty easy to carry (especially my 5lbs and 10lbs bottles).  That means I can drag it to where the air is needed and I can mount or store the bottle anywhere on the rig (especially important to me since I don't have much room in my engine bay for a compressor).

 

Backyard inflatable pool?  Don't need to drag the shop compressor or jeep into the backyard.  Just a bottle of CO2 and the hose.

 

Fellow Jeeper a 30 feet away from my rig?  I don't have to drag a long line or move my jeep.  I don't even have to bring a pump and hook it up to their battery. I just bring the bottle to them.

 

Trailer tire or tow rig low?  I don't even have to start my jeep, just bring out the bottle.

 

Now that we have the basics covered, the next post will talk about the pros/cons of a CO2 tank vs other common OBA setups.

 

[thecodemonk]

How does it compare to a more traditional On-Board-Air (OBA) setup that uses a compressor pump?

Since a CO2 tank can be used in place of a traditional on-board air (OBA) setup, it seems fair to compare them as there are pros and cons to both setups.

 

For fairness, since there are two main setups for traditional OBA, I’ll list pros and cons for each separately.

• Pump only (sometimes has a TINY buffer tank)
• Pump and tank (big enough to be measured in gallons)

 

- Example of an electric compressor: (ARB Dual Compressor)

 

- Example of a mechanical compressor: (Jeep AC Compressor) 

- Example of an air tank: (2.5 Gallon ViAir tank) 

 

CO2 tank Vs Pump and tank:

• Pro: Requires no electrical wiring or power.
• Pro: Requires no real added plumbing to work.
• Pro: Quieter than any air pump since it has no moving parts.
• Pro: No duty cycle (no having to rest the pump every so often), regardless of how much PSI your regulator is set to.  It can just go and go and go until the tank is empty.
• Pro: Does not generate any heat (in fact the opposite, it gets cold as expanding gasses drop in temperature)
• Pro: Fills up tires FAST (only limited on how much flow your regulator and hoses will allow and how much CO2 you have in your tank). 
• Pro compared to hard-mounted pumps: Can easily be moved close to the work as it fully self contained. 
• Pro compared to a mechanical pump: more flexibility in mounting if you don’t have room in your engine bay or don’t want to give up your existing AC pump
• Con: Requires added monitoring to remember how much CO2 you have left before running out.
• Con: You CAN run out of CO2.  A pump is taking air from around you so you're VERY unlikely to run out of air (in which case, breathing might be more of a concern).
• Con: (Arguable) more maintenance…ongoing expense and time to fill up the tank (it’s about $20 to fill a 10# tank for me, which lasts about 4-5 runs on 37s)
  • arguable because I’ve had many inexpensive electric pumps burn out after a year or so even when I was on 33s…big tires is just too much for them to run continuously.  Pumps also need occasional addition of oil to keep those moving parts lubricated.
• Con: More expensive startup cost to buy the tank and regulators…either as a kit or DIY.
• Con: Depending on your regulator components and if run continuously for too long, the components can freeze up (Thanks Pete!)

 

 

CO2 tank Vs Pump Only

• All of the above applies with the addition of the following:
• Pro: Can run even higher powered air tools as it has plenty of consistent PSI and capacity (most pumps will struggle to maintain even 90 PSI continuously without a buffer tank)
• Con vs Electric Pump: Tanks are going to be heavier and larger than small standalone electric pumps.
• Con: The tank takes up more space than almost all pumps.

 

So...all of that listed out, an air compressor may be the right fit for you and it may be worth the extra work to never have to pay to fill up the tank or you may live in an area where you can give up your AC pump or have room to mount a second one.  But hopefully this writeup gives you the tools to decide if CO2 might be easier or at the very least, a useful backup. 

[thecodemonk]

<<Reserved in case I missed something>>

[fiatslug87]

Con: CO2 is a greenhouse gas and us Comanche owners are all about being green.

[Pete M]

con:  the valve likes to freeze up if run for too long. ("too long" varies depending on outside temps)  stupid physics!  

 

pro:  having 100psi with gobs and gobs of cfm is just awesome  

[thecodemonk]

@Pete M Ooh, it was on my mind to mention the freezing thing and I forgot by the end.  Thanks for the reminder!  Added!

 

@fiatslug87 Heck yeah!  Green paint counts right?