How many car tires can an Al 80 with 3,000 PSI fill?

[Zeagle Eagle]

I am trying to figure out whether to take my scuba tank Aluminum 80 (3,000 psi) to top off 12 RV tires or an air compressor with an 8 gallon tank near 150 psi.

Thoughts, advice?

 

[flyboy08]

Well, if you start with 3000psi and each tire needs 50psi....50x12 is 600.....you'll have plenty left over using the tank

 

[grf88]

The scuba tank holds almost 8 times as much.

 

[guruboy]

Well, if you start with 3000psi and each tire needs 50psi....50x12 is 600.....you'll have plenty left over using the tank

You forgot about volume.

 

[yle]

Depends on how big the car tires are. If we use a tire that is... 205/60-15 which is a normal size passenger car tire, the volume of this tire is about 1.5 cubic feet. If you need to inflate this to 30 psi then you can do a simple comparison of volume and pressure:

number of car tires x 1.5 cu ft per tire x 45 psi = 80 cu ft x 15 psi

(Note: your AL 80 has the same amount of air as 80 cu ft at standard pressure of 15 psi; the car tires have to be inflated to 30 psi above the outside air pressure... total of 45 psi.)

number of car tires = approx 18

Of course the calculation varies by the size of the tire and the pressure you want in them.

This to inflate the tires from dead flat... if you're just "topping them off", i.e. from say 25 to 30 psi, you could do 50 to 100 of them. Make sure you have a first stage reg between the tank and the tires though! We used to do this to inflate bike tires at the shop I used to work at... one scuba tank would last a week or so.

 

[GreggS]

The tank should fill the tires quicker than the compressor, also.

 

[yle]

The tank should fill the tires quicker than the compressor, also.

Depends... if the compressor banks at 150 psi and the first stage on the scuba tank has an IP of 140 psi, the fill rate into the tire would be about the same. Which is good: you don't want to fill anything with compressed air too fast.

 

[Zeagle Eagle]

I knew you smart guys would figure this out for me. There is still air in the tires, probably around 20-25 psi. I just need to top them off and I didn't think an 8 gallon tank with 150 psi would do the trick.

 

[RainPilot]

I used to use a 10 litre steel tank for shore diving in South Africa. After the dive I would have around 50 bar in the tank and use it to to reinflate the Land Rover tyres. They were BIG tyres and I had them down to around one bar for sand, put them back to the 3 bar for road use and really couldn’t see any real drop in the SPG. Always amazed me how much gas is actually in these tanks.

 

[yle]

I knew you smart guys would figure this out for me. There is still air in the tires, probably around 20-25 psi. I just need to top them off and I didn't think an 8 gallon tank with 150 psi would do the trick.

8 gallons is about 1 cubic foot... so using the same calc as above, your air compressor could fill

number of tires x 1.5 cu ft per tire x 45 psi = 1 cu ft x 150 psi

number of tires = about 2

It could fill two normal size tires from completely flat... so it could probably just be enough to top off your four tires.