Chilling PCP air cylinder before/during fill

[needmoretoys]

The air cylinder on my AA S400 MPR is relatively small, at least compared to my Marauder. However, it is removed to charge. When I charge it from my Air Venturi tank it heats up, as expected. I want to charge from 110 BAR to 170 BAR. If I charge to 190 BAR the cylinder gets pretty warm and then the pressure drops to about 160 BAR after it cools in my currently cool 62 deg basement. I see the same thing when the paintball dealer fills my AV tank. He fills it to 4500 PSI and it then drops to 4000 PSI as it cools and he then tops it off.

I'm thinking of pre-cooling the AA cylinder by wrapping it in an ice wrap and keeping it there while I fill. Does anyone pre-cool their cylinders before filling or is there a better way of getting a complete fill. I guess I could just let it set connected for 30 minutes and then top up again. I don't want to disconnect and then reconnect because of the air loss in the line and adapters.

[Bradmond]

My local scuba shop takes a couple days to fill my cylinders so they can cool and get topped off.  I have heard that some other shops put the cylinders in cold water while filling to keep them cool. Maybe try that, you can add some ice too.

[Motorhead]

Fill SLOWER .... pre-chilling will in all likelihood create condensation / sweating because of rapid thermal changes.

[needmoretoys]

I fill as slowly as I can. I very slowly open the valve until it just starts to release air. Where am I going to get condensation? If on the outside of the cylinder then I'll just dry it off. I shouldn't get condensation on the inside as the air should be dry. If inside condensation is a problem by pre-chilling then no one should shoot a PCP outdoors in the winter.

[Motorhead]

Ever seen a glass filled with ice sweat ... Inside a window ... Metal surfaces too
Rapid & extreme changes in temperature exacerbate the issue.

Jmo ...

* Pre-Chilling Co2 vessels to be filled, that's entirely different and had good reason behind doing so. 

[wimpanzee]

I've got a slo-flo valve from Joe Brancato on my tank, and I cannot tell a temperature difference on my synrod reservoir after filling it.

Paintball shop, too, knows to fill it slow. Give it a good 1-2 minute fill, and no apparent temp change.

The only time I have seen a significant pressure drop from cooling is when I filled my tank from empty in December (about 10F outside), and walked out to the car with it. It was pinging and popping...and lost several hundred PSI. It was quite warm to the touch before cooling off. After that, I talked to the paintball guys, and they are happy to fill it a little slower.

[Mukilteo]

My local scuba shop takes a couple days to fill my cylinders so they can cool and get topped off.  I have heard that some other shops put the cylinders in cold water while filling to keep them cool. Maybe try that, you can add some ice too.

Back in 1972 New England Divers had a store in the Top Hat area south of Burien on 1st Ave So. Harvie's was in the basement (they made wet suits)
Anyway, the dive shop had a water tank to cool the tanks.

[needmoretoys]

Ice on the inside of a window in the winter is a totally different situation. That's because the air in the house has a moisture content that causes it to be over 100% relative humidity on the cold window glass. If the house air were dried then there would be no condensation. Same for a glass. Again, if chilling the cylinder to say 10 to 20 degrees is a problem then taking a PCP rifle outdoors when the temperature is say zero would be an even greater problem. If the air in the tank is not dry then having the rifle in any cold environment will cause condensation in the cylinder.

[needmoretoys]

I've got a slo-flo valve from Joe Brancato on my tank, and I cannot tell a temperature difference on my synrod reservoir after filling it.

Paintball shop, too, knows to fill it slow. Give it a good 1-2 minute fill, and no apparent temp change.

The only time I have seen a significant pressure drop from cooling is when I filled my tank from empty in December (about 10F outside), and walked out to the car with it. It was pinging and popping...and lost several hundred PSI. It was quite warm to the touch before cooling off. After that, I talked to the paintball guys, and they are happy to fill it a little slower.

The slo-flo valve is likely the best solution, but I have 2 AV 90 ci tanks. I'd have to check if the slo-flo valves fit, but in any case they are $229, so it would cost me $458 for both tanks. My Marauder has much less of a temperature change and pressure drop than the S400 cylinder does, but the Marauder cylinder is over double the volume of the S400. That means that it takes over 2X the time to fill.

[William]

Do not cool it down, fools and there AG shall soon part! No reason to do it, it can and will cause problems as mentioned above. Just fill slowly, if it is getting that hot you need to slow down. Always fill at room temp to the Manufactures recommended pressure.  As for filling tanks, use the same caution.

Filling any tank that is cooled down can cause accidental over filling, fill slowly and follow the manufactures recommendations. Once a tank is overfilled it can cause fatigue on the metal or material it is made of and the more times it happens the more likely the fatigue will get worse.
The only reason I can think of for filling a Scuba tank in water is due to it may prevent metal parts from flying to far if it ruptures! Just like what happens when a bullet hits water and loses all its energy within a couple feet of less!

I fill my tanks and Guns all the time and have never had them get to hot to worry about, I fill slowly.

William

[LDP]

Fill SLOWER .... pre-chilling will in all likelihood create condensation / sweating because of rapid thermal changes.

+1 if you are heating up such a small cylinder you are filling way to fast. I fill my AA S510, Mrod and BSA S10 without heating them up and I can fill the AF bottles without getting them warm.

[n2omike]

I put the mustang's nitrous oxide bottles in the freezer overnight before filling them.  A pump is used for the transfer, but they still get warm during filling.  Chilling makes the filling easier.  It's much like CO2, though...  and is transferred from the 'mother' bottle to the one used in the car via a pneumatic pump.  If the bottle and it's remaining contents are hot, it can be hard to get them all the way full sometimes...  as they get pretty warm as they are filled.  Pressure increases, and it's harder to get the full weight of nitrous in them. 

I don't think you have ANYTHING to worry about when chilling air bottles.  The ONLY way there could be any danger, is if the FINISHED bottle would STILL be FAR below room temperature...  then it could warm up to a higher psi...  but that is NOT going to happen, as it will still warm up as it's being filled...  and even if it was a bit below room temp when done, it wouldn't be significant. 

REALLY like the Shoebox for filling.  Zero moisture, as the air moves slowly through the large desiccant filters that have been added, giving them plenty of contact time to do their jobs...  and once the bottle is pumped up to 4500psi, it STAYS at 4500 psi.  No cooling off to a lower pressure! 

Good Luck!

ps...  Misread your post...  Just skimmed it, and focused on "chilling and filling".  lol  Was thinking more along the lines of filling a LARGE sized bottle using a fast pump.  Here, freezing the bottle overnight might keep it from dropping as much after it cools from being pressurized so fast.

[needmoretoys]

I put the mustang's nitrous oxide bottles in the freezer overnight before filling them.  A pump is used for the transfer, but they still get warm during filling.  Chilling makes the filling easier.  It's much like CO2, though...  and is transferred from the 'mother' bottle to the one used in the car via a pneumatic pump.  If the bottle and it's remaining contents are hot, it can be hard to get them all the way full sometimes...  as they get pretty warm as they are filled.  Pressure increases, and it's harder to get the full weight of nitrous in them. 

I don't think you have ANYTHING to worry about when chilling air bottles.  The ONLY way there could be any danger, is if the FINISHED bottle would STILL be FAR below room temperature...  then it could warm up to a higher psi...  but that is NOT going to happen, as it will still warm up as it's being filled...  and even if it was a bit below room temp when done, it wouldn't be significant. 

REALLY like the Shoebox for filling.  Zero moisture, as the air moves slowly through the large desiccant filters that have been added, giving them plenty of contact time to do their jobs...  and once the bottle is pumped up to 4500psi, it STAYS at 4500 psi.  No cooling off to a lower pressure! 

Good Luck!

ps...  Misread your post...  Just skimmed it, and focused on "chilling and filling".  lol  Was thinking more along the lines of filling a LARGE sized bottle using a fast pump.  Here, freezing the bottle overnight might keep it from dropping as much after it cools from being pressurized so fast.

Getting the 90 ci bottle filled to 4500 psi is the paintball dealer's problem. When I bought the new one from him, it got pretty warm (not hot) when filling from zero to 4500 psi. It then immediately started to drop in pressure, so he gave it a bath in cold water for a few minutes. He then topped it off to 4500 and it was only down to 4400 when I got it home. If he fills from a remaining 2500 psi or so then he just has to let it sit for a while before topping.

I have no concerns of overfilling by chilling. The fill pressure is 200 BAR, but I only want it at 170 BAR to start. I can fill to 200 BAR and then it will be at 170 BAR or slightly lower when cool again. However, if I chill and only have to fill it to 170 BAR to have it at 170 BAR when at room temperature then I can get more fills from the 90 ci bottle. Even if the pressure rises a bit, it is not going to rise from 170 BAR to over 200 BAR; not even close.

If I'm very careful to open the valve very slowly only until I get the smallest airflow I can get, it still only takes about 10 seconds to reach 190 BAR in the cylinder. I need to find a metal disk and drill a pinhole in it and install it somewhere in one of the mating adapters (AA DIN adapter to DIN to 1/8 BSPP adapter to 1/8 BAPP to male Foster).

[Mod90]

chilling a vessel prior to filling it is not something I'd recommend. Besides the condensation issue, the cold vessel will cool the incoming air, and you will get a lower reading on the tank's gauge. when that tank thaws & gets warmer the pressure inside is going to increase as well and may surpass the MSWP the manufacturer indicated. So it's possible there could be a valve lock offurence or worst case scenario an eventual rupture.

Fill the gun's reservoir slowly, always better to be safe than sorry

[n2omike]

chilling a vessel prior to filling it is not something I'd recommend. Besides the condensation issue, the cold vessel will cool the incoming air, and you will get a lower reading on the tank's gauge. when that tank thaws & gets warmer the pressure inside is going to increase as well and may surpass the MSWP the manufacturer indicated. So it's possible there could be a valve lock offurence or worst case scenario an eventual rupture.

Fill the gun's reservoir slowly, always better to be safe than sorry

During a fill, the temperature WILL rise above ambient...  even if the bottle is cooled.  The ONLY way there could be any kind of problem, is if the air was super cold AFTER it hit 4500 psi...  and that's not going to happen. 

Compression of the air creates heat.  Freezing the bottle will only keep it from getting as hot as it would have without being frozen...  minimizing pressure drop at the end as it cools back down to ambient. 

[MicErs]

I'm thinking of pre-cooling the AA cylinder by wrapping it in an ice wrap and keeping it there while I fill. Does anyone pre-cool their cylinders before filling or is there a better way of getting a complete fill. I guess I could just let it set connected for 30 minutes and then top up again. I don't want to disconnect and then reconnect because of the air loss in the line and adapters.

I would not do that.  Surely the engineers who designed the system were not expecting you to do something like that.  For that reason I wouldn't.  Other posters suggested filling, allowing it to cool, and filling again.  That seems safer to me.

[needmoretoys]

So if me chilling the cylinder to say 20 deg F is a bad idea then I assume that no one has ever filled their rifle out doors in the winter when the temperature was 20 deg F or less. As far as telling me to fill more slowly, I don't know how many times I have said that I'm filling as slowly as the AV valve allows. I do appreciate the comments, but I still don't see how chilling to 20 deg F is such a bad idea.

I have never seen anyone say that it is not good to use or fill a PCP outdoors in the winter. If you have a high powered rifle like some of the .357 to .50 rifles that only get 7 to 10 shots per fill then the cylinder will surely cool at least a few degrees below ambient while shooting (rapid expansion in cylinder). So if it is 20F outside then the cylinder will likely be at 10F or 15F. Is then filling the cylinder not allowed until warming the rifle up to room temperature? There is no difference between that and chilling the cylinder in the house before filling. The air in the bottle will be the same air. It does not automatically have a higher moisture content just because the bottle is in the house.

I can fill to 170 BAR, leave it connected for 20 or so minutes and then open the valve again, assuming I don't have a really slow leak that isn't evident during a normal minute fill. Even if I do that, pre-chilling will speed things up some.

[MicErs]

So if me chilling the cylinder to say 20 deg F is a bad idea then I assume that no one has ever filled their rifle out doors in the winter when the temperature was 20 deg F or less. As far as telling me to fill more slowly, I don't know how many times I have said that I'm filling as slowly as the AV valve allows. I do appreciate the comments, but I still don't see how chilling to 20 deg F is such a bad idea.

Well you should feel comfortable ignoring my advice as I am not qualified to speak to the mechanical engineering aspects of pressure changes with respect to temperature at fill.  There are people here who can speak to that and maybe they will chime in.  Motorhead is pretty smart about these things.  He seems to think condensation could be an issue.  On that I agree because when I pump up my Lonestar too quickly I get condensation in the pump.  I think condensation inside the gun is probably undesirable.  Frankly I don't know if cooling the tube would make that issue worse or better.

[Motorhead]

Gotta say ... It appears YOU ALREADY HAD YOUR MIND MADE UP on what you are justifying in doing with every rebuttal comment made by the membership here.

It appears by comments or a lack of ... NO ONE ELSE is pre-chilling there HPA bottles before filling.
So by the nature of the original posts inquire met with a justified argument serves no purpose other to entertain yourself of how wrong we are ...... We know what that practice is called if this is the case 

[needmoretoys]

Gotta say ... It appears YOU ALREADY HAD YOUR MIND MADE UP on what you are justifying in doing with every rebuttal comment made by the membership here.

It appears by comments or a lack of ... NO ONE ELSE is pre-chilling there HPA bottles before filling.
So by the nature of the original posts inquire met with a justified argument serves no purpose other to entertain yourself of how wrong we are ...... We know what that practice is called if this is the case 

Do you have actual evidence/experience that condensation will occur inside the cylinder or are you just guessing that it will. If you have actual evidence then please present it to me and I will then have reason to agree with you. I'm looking at it from my mechanical engineering background, but I might be missing something, or perhaps not.