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How to push your CF tank pressure to 4500 psi w/o pushing your compressor to it

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Think steam for a short while.

Water at room temperature but at 100degC~212degF steam, it's at 1bar~14.3psi but at 270degC~520degF the pressure is 46bar~667psi.

https://www.valvesonline.com.au/references/steam-tables/

All we have done is raise temeprature, no pixie dust!



Air is a liquid at -196degC~321degF and the rest is uphill from there. What you have "invented" is simply to lover your temp and pressure for the time being, but what if you tote that CF bottle will a good cold 4500psi to a shooting with the bottle resting in the nice Texan sun? Now look at your previous 4500psi.

Theres no such thing as a free lunch!


 
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I never professed to "invent" anything. I'm simply sharing a technique to get more air into the tank thank without pushing your pump beyond it's capacity (or people's comfort level). That's all. I realize it's basic physics. But most of the guys on here feel totally comfortable putting 4500 psi in their CF tanks. But not all of those guys feel comfortable pushing their compressors to that level. So they settle for a lower pressure and miss out on the extra shot count and refills on their air rifle bottles. I provided them a technique to achieve a 4500 psi fill by pushing their pump to 4100 or 4200 psi (which seems to be the sweet spot for their comfort level).

I do remember the rock salt technique from the old school ice cream makers. And I've heard that frozen seawater is significantly colder than frozen fresh water. But in order to get to -6F, the salt water would have to be saturated to where it couldn't hold any more salt. Also, you would have to either start with frozen saltwater that was already at -6F, or you would have to expose the salt water to a cold source that could bring it down to that temperature. But you cannot achieve -6F by adding a saturating level of salt to an ice water slurry. You will bring the temp down somewhat, but certainly not to -6F.
 
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This is not an uncommon thing. I've seen it at most dragstrips I've been to when staff is topping off nitrous tanks using booster pumps. They ice the tanks so that the booster pump doesn't have to work as hard. Same thing at work in a CF tank but I'm not sure how much you are gaining in compressor longevity. Possibly a noticeable amount but not sure. If you feel better doing it then no reason not to.
Click to expand...

Yes sir I agree! We used to place our nitrous tanks in the freezer prior to filling them for the same reason. We didn't have a Nitrous filling station but just used a master bottle and the pressure within the tank to fill our smaller 10 pound bottles. 
 
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I have a small chest style venison freezer in the basement, I’m going to drill a small hole in it and just put my CF cylinder in there and fill. Should save on a bit of ice and making ice. 

I used to have one of those Air Venturi football sized CF cylinders for my Marauder, I used to toss it in the freezer before I took it to the paintball shop before I had a compressor. They liked to fill it in two nanoseconds so if I didn’t chill it I always had a short fill. 

I used to work part time in a dive shop, I always filled at a rate that did not see a pressure drop an hour later. If the customer wasin a hurry, he was informed there would be a pressure drop of one or two hundred psi. 
 
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It's been a while since I posted this thread- but I still stand by what I said. The temperature of the water will have zero impact on the durability and integrity of the CF bottle. It's impossible for the water to get below 30 degrees F (that's if you decided to use salt water), and many of you guys live in areas of the country where you're shooting and filling in temperatures below that during the winter time.

If you're afraid that your bottle will rupture, think again. Those bottles are hydro-tested at over 7000 psi. So going to 5000 is nothing for them. However, if this still gives you the heebie-geebies, then fill your bottle to 4200 psi in the normal ambient air temperature. Give the bottle 30 minutes to settle in, and throw it into the ice bath or the freezer. Give it 30-45 minutes in the cooler environment. The pressure will drop from 4200 psi to about 3750 psi. Then while the bottle is still in the ice bath or in the freezer, fill it back up to 4200 psi. When you hit 4200 psi, close the valves and pull it out. Over the course of the next 30 minutes, as the air in the bottle equalizes with the ambient temperature of the air outside, you will see the pressure climb to 4500-4600 psi. That equates to 4 or 5 extra top off's.
 
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