How bad is flash filling for HPA tanks?

[WalkingTarget]

My local scuba shop stopped filling Paintball tanks after their tech went to play at a field in Toronto and witnessed tanks being flash-filled.

in his words "i'll fill my own tanks, but i refuse to fill a tank that has been flash-filled"

true to his words, the last time he filled my HPA before i sold it, he did it at 700PSI/minute, only because he couldn't set their booster to do such a small tank any slower.

[OneUp]

i suppose it is up to the consumers then.

tell everyone fast fills lose pressure when cooled down, that they wasted their $. They'd care unless it's all day air.

[Shane-O-Mac]

D.O.T regs require that if a cylinder gets over a certain temp it is to be destroyed. That temp is around 130F IIRC. At the last Chicago open I went to, I used a temp gun and was reading temps of the tank itself over 140F right after filling. The tanks at many times was too hot to handle. Also, heating up your tank by flash filling is harder on the tank and outside of its design boundaries. If you consistently heat up your tank with flash fills you are risking not passing hydro, and weakening the tank. Just because the tanks works fine with flash fills, doesnt mean it IS fine. If the tank that failed due to oil being put in the fill nipple, had been filled slowly, they proabably wouldnt have failed the way they did. The HEAT was a big factor in those incidences. The motor in your car operates the same way, except it use spark plugs, instead if heat to ignite. It is actually the way a diesel engine works. My point is that if the heat wasn't present, it wouldn't have happened....................

If you are faced with having to fill with a self serve station, fill it in slow bursts. Like a 1000psi at a time and let it cool for 30 seconds. Or hit the button for 30 seconds then wait 20 seconds or so.

[Chaos_Theory!]

If you are faced with having to fill with a self serve station, fill it in slow bursts. Like a 1000psi at a time and let it cool for 30 seconds. Or hit the button for 30 seconds then wait 20 seconds or so.

Thats not very realistic unless your the only person around who needs a fill. I havnt been to a field yet where it takes more than like 10 seconds to fill to 4500psi. Also, i have not gotten a really warm tank any of those times.

[OneUp]

Thats not very realistic unless your the only person around who needs a fill. I havnt been to a field yet where it takes more than like 10 seconds to fill to 4500psi. Also, i have not gotten a really warm tank any of those times.

I get warm tanks all the time.

i remember when i was using a steely they were indeed too hot to handle after a fill.

so i suppose asking them to fill my 45 4500 only to 3000 is a good thing since it doesn't put that much pressure and heat into it? cuz I've been doing that.

[fullofpaint]

slightly off topic here. Does anyone els have a CP tank? Everyone I know who has a cp tank, when they fill it (regardless of the fill station) the tank fills extremly slowly. Anyone know what causes this?

[Hilltop Customs]

ehh my field has one and it takes about 5 seconds, the tank doesnt get any warmer than it does when filling off a scuba tank, as a matter of fact, it doesnt get as warm, well compared to my other filling place. i really dont know anything about filling tanks, i just know that push button is easy and my tank works fine with it

I can guarantee the air inside the tank gets much much hotter when you flash fill. When you flash fill the outside of the tank doesnt have time to heat evenly with the inside air in the tank. So you have a cool outer surface and a really hot gas inside....this temp differential is what can causes microscopic stress cracks to form in the tank.(if you want I can explain that in more depth) I think everyone has to agree cracks in a tank are bad no matter how small they are. The sad thing is flash filling has been accepted by the mass majority of fields. (this isnt a knock on you, sorry if it sounds that way, i just cant think of a nicer way to put it)

slightly off topic here. Does anyone els have a CP tank? Everyone I know who has a cp tank, when they fill it (regardless of the fill station) the tank fills extremly slowly. Anyone know what causes this?

Probably a really restrictive fill nipple, or passage from the fill nipple to the inside the tank. That could be a good or bad thing depending if its accounted for in the design of the tank.

IMO tank companies could have taken care of this problem in production....a restrictive fill port would slow filling to an acceptable level. Considering the young age group that plays paintball, that is a saftey precatuion that SHOULD have been implemented. Another saftey precatution would have been a fill nipple that couldnt be oiled......but then again what do I know.

[pyrodragon]

500 psi per minute is 9 minutes for a full fill at 4500psi, or 6 minutes for 3000psi. Imagine being at a tournament of 25 teams of five guys. 125x 6 = 750 minutes for one fill total or over 2 hours with one fill station, 4 hours with three, 2 hours with 6 , then yu have to account for multiple games ending quickly and other factors including everyone will want a fill before their first games. Huge events like NPPL, PSP and IAO would come to a grinding halt as getting air would be the new comperative sport.

don't know where u get ur 500psi per minute, because 100psi/second = 6000psi/minute. that means 4.5kpsi bottles would only take 45 seconds and a 3k psi bottle only 30 seconds. i agree that it's fast. i run scuba tanks and fill from them at our games. i'm the one that usually fills everyone's tanks and i run them very slow. safety is the number one thing at our games. if done right u can get plenty of tanks filled in time for big tounries. plus don't these tourny guys have pod monkeys filling their pods in between games? and don't they carry more than one tank to a tourny? so ur point about waiting in line? full multiple tanks at first then switch when one tank is empty. while tourny player is playing, pod monkey goes and has empty tank filled. i've never played tourny but like they say it's part of the game. be prepare for the unexpected. if it was me and i played tourny, i would show up with more than i needed. if i'm worry i wouldn't have enough air, i would make sure i had a backup plan. kids nowadays. better to be safe than sorry later.

[Shane-O-Mac]

Thats not very realistic unless your the only person around who needs a fill. I havnt been to a field yet where it takes more than like 10 seconds to fill to 4500psi. Also, i have not gotten a really warm tank any of those times.

Realistic huh?

Well, how do you want it, SLOW or DANGEROUS?

If a field owner staffed his fill station with a properly trained employee, it wouldn't take that long. My time suggestion was maybe a bit on the long side, but the point is still the same. If the air station flash fills without you being able to slow it down, then some steps are necessary for safety. And I am sorry but your tank isn't immune to physics. If you keep your tank cover on, your not gonna feel much warmth. Not sure if thats the case with yours, but a possibility. Filling a 68/4500psi tank in 10 seconds is very bad, and will heat up a tank.

Heres part of the reason for filling slow. When you fill your HPA tank, it expands slightly, when filled properly, it expands less and doesnt get expanded beyond design parameters. When flash filled the tank expands quickly and beyond design parameters, which leads to weakening of the inner liner. The inner liner is a thin aluminum shell, that is then wrapped in carbonfiber or fiberglass.

Like I said before, just because it doesn't appear to hurt your tank, it is hurting it.

[Beemer]

Realistic huh?

Well, how do you want it, SLOW or DANGEROUS?

Like I said before, just because it doesn't appear to hurt your tank, it is hurting it.

LOL thats classic, SLOw or.......

So without a real Governing Body and manufacturers not telling us and ASTM standards that arent followed what is the safe fill rate for 4500psi???? I looked around and came up with the same thing. 500psi per min. Not to mention most of the fills we get are probably real DIRTY. I want some of that Hpac air in my fills. Breathing QUALITY. A slow fill will be a FULL fill every time first time.

Hey tell the folks on the governing body we need to talk, hmm what? We dont have no stinking governing body. Really? Thats pretty stupid.

Paintball must be stupid because that is all I ever hear. Show the scuba guys and the real fire arms folks how we do stuff and you will hear........Thats pretty stupid.

Even our employees at the CPSC and some laywers and others say the same thing about not following ASTM standards or not having any at all and no REAL governing body.

Three tanks in a year. Any one want a stako tank? Whats up with that?

http://www.p8ntballer-forums.com/vb/showthread.php?t=96946

http://www.mcarterbrown.com/forums/p...ows-up-uk.html

[cpt]

We call them "hot fills" in the fire service. You lose about 500 psi once the tanks cool down and we started noticing we were losing seals a lot more. The tanks always passed inspection but we have quit doing it unless we are in emergency mode.

[jenarelJAM]

Some fields actually limit fill speed. My home field, Davis Paintball, fills at about 100 psi/second. This is all self-serve. They've got a table, you just go up to it and hook in, and press the lever. Now, that may be faster than said "recommended" fill speeds, but it gets the tank filled in under a minute still, and it merely warm at the end. Generally, you lose ~200 psi when it cools down.

[Corvad]

After reading this thread I got concerned about the safe fill rates for an HPA tank although the suggested maximum rates didn't quite feel right to me so I attempted to figure out the physics behind it. While I'm no engineer or physicist I have come to a satisfactory conclusion for myself and I'll attempt to share it here.

What made me pause what the large size difference in the tanks, I have an 88cui HPA tank, while an average scuba tank holds 80cf of air, its inner volume is about 678cui according to luxfer cylinders. While my tank is a 4500 I'm just going to use a basis of 3000psi as that is the pressure of a general 80cf scuba tank for comparison, still this a difference of 8 times the volume of air, and I feel this is a very important fact.

The maximum suggested fill rate for a scuba tank is about 500psi per minute and applying this directly to a tank that is 8 times smaller can't be right, so down to some wordy math now. Since this isn't really my area of expertise I may be in need of correction.

The heat generated in the tank is due to the friction of the gas moving through the fill nipple and hoses, not because of any pressure changes. The heat does increase the pressure in the tank, but once it cools back down to room temperature the pressure will go down accordingly which has been observed. It is the friction that is the problem, and with a scuba tank being 678cui you have approximately 8 times the amount of air rubbing through the fill fixtures creating heat, so in that minute of fill, I approximated about 23,000 cubic inches of air flowing into the scuba tank. (this is assuming that it takes 46cui of air to increase the pressure by 1 psi) Now compare that with an HPA tank of 88cui, at 500psi/minute its only about 2,685 cubic inches of air(assuming its approximate 5cui of air per psi in the 88cui tank), that translates into a whole lot less friction and heat generated. So this means we should be able to fill about 6-7 times faster than a scuba tank, unless I missed an important fact in there, again, I'm not engineer or physicist. This is also assuming that the smaller filling fixtures on the HPA tank generate more friction ans more of the air is in contact with a surface its moving past.

Important note, as I wrote this I found a few flaws in my math and have attempted to fix them before posting.

Now this is assuming the fixtures are the same diameter and sizes, but I know they aren't and this is where my math ends at the flow rate section.

Still, to me this means yes, we should be able to fill faster on our smaller HPA tanks, but still nowhere near the 3 second fills bragged about. Personally this means I'll shoot for about 90 - 120 second fills for my 88/4500 tank.

And yes, I did just register to post wordy math...

Notes on how I figured the amount of air per psi in each tank.
Since a scuba holds 80cubic feet of air at 3000 psi in a 678 cui tank.
And 1 cubic foot is equal to 1728 cubic inches.
80 * 1728 = 138240 cubic inches of air at 3000psi, so for 1 psi
138240 / 3000 = 46.08cubic inches per psi
similarly for an 88cubic inch HPA tank holding 14cubic feet of air at 4500 psi according to luxfer.