Air Pressure
Okay, I bought a HPA tank recently and was pretty happy about the deal. It's 68/4500 which I thought would give me alot more playing time than my 47/3000.
Anyways, I got it and had it aired up at the local pb shop to make sure there were no problems with it. I trust the guy I bought it from, just wanted to make sure because I know he switched the regs on it before selling it to me (it used to have a LP reg and he put a HP adjustable reg on it).
Anyways, they aired it up and it read about 4250psi as I brought it out to my car. Today, 2 days later...it sits in it's padded case in the garage and the pressure reading is just under 3500psi.
Now, here's where we get back into our freshman chemistry...the temperature it was at when it read 4250psi was slightly above room temperature (it had just been filled and was a little warm to the touch). In my garage, it's a brisk 29 degrees F.
Seeing that the pressure was lower made me first say, "oh crap! It's leaking!" This made me very anxious because it's the most expensive piece of paintball equipment I own...and I just got it and was all happy. I'm also anxious because if it is leaking I either have to try and resolve the problem with the seller or see if I can get it repaired (is that possible...if a tank has a small leak to have it repaired at a pb shop or something???)
But then I remembered my ideal gas equation from 15 years ago, freshman chemistry. Essentially, with the temperature decreasing, and everythig else remaining constant...the pressure should also decrease. But in order to figure out exactly what pressure drop I "should" see...I would need to know the value "n" (which I believe is the weight of the gas that was added to the bottle)...which I don't know.
Any experience with this. Is this normal that the pressure would drop like that just due to the cold weather? Is a faint leak repairable? How much am I looking at ($$$)?
I will try and bring it in the house overnight and see if the pressure increases due to the temperature change. I can also leave it in the garage and see if it empties to zero...which would be evident of a leak.
Thanks for the help...I'm panicing over this!!
Anyways, I got it and had it aired up at the local pb shop to make sure there were no problems with it. I trust the guy I bought it from, just wanted to make sure because I know he switched the regs on it before selling it to me (it used to have a LP reg and he put a HP adjustable reg on it).
Anyways, they aired it up and it read about 4250psi as I brought it out to my car. Today, 2 days later...it sits in it's padded case in the garage and the pressure reading is just under 3500psi.
Now, here's where we get back into our freshman chemistry...the temperature it was at when it read 4250psi was slightly above room temperature (it had just been filled and was a little warm to the touch). In my garage, it's a brisk 29 degrees F.
Seeing that the pressure was lower made me first say, "oh crap! It's leaking!" This made me very anxious because it's the most expensive piece of paintball equipment I own...and I just got it and was all happy. I'm also anxious because if it is leaking I either have to try and resolve the problem with the seller or see if I can get it repaired (is that possible...if a tank has a small leak to have it repaired at a pb shop or something???)
But then I remembered my ideal gas equation from 15 years ago, freshman chemistry. Essentially, with the temperature decreasing, and everythig else remaining constant...the pressure should also decrease. But in order to figure out exactly what pressure drop I "should" see...I would need to know the value "n" (which I believe is the weight of the gas that was added to the bottle)...which I don't know.
Any experience with this. Is this normal that the pressure would drop like that just due to the cold weather? Is a faint leak repairable? How much am I looking at ($$$)?
I will try and bring it in the house overnight and see if the pressure increases due to the temperature change. I can also leave it in the garage and see if it empties to zero...which would be evident of a leak.
Thanks for the help...I'm panicing over this!!
I'll check it again in the morning then put it back out in the garage in it's case. If it's at or above 4000 by tommorrow morning...I'm going to assume it's not a leak and just the result of temperature. If that's the case, maybe this post will be useful (if anyone uses the search feature!) to people in the future regarding the effects of temperature on a tank's pressure. I never would have guessed the pressure drop would be so great based on temperature alone...interesting... 
This is also the reason you never fill a CO2 to max. Because, the pressure will increase as the bottle reaches room temp. Leave it in your car during the summer and youll blow the burst disc.
Comment