trouble getting my tank filled to 4500psi

[Guest]

Hey guys. Im new to the world of pcp airguns and i recently received my fx wildcat .25 , hawke sidewinder, tank, bipod etc .So I've taken my tank to both the paintball store and the scuba shop. Both said they could fill my 75 cu.ft. carbon fiber omega tank to 4500psi , but both places could only fill it to 4200psi. Why? Shouldn't a 4500psi compressor do its job? Another thing is the air tank calculator. I put in my info , even the worst case scenario, and even with my tank filled to only 4200psi, it calculated I should get at least 20 fills . I only got 10 full fills! Is this normal? Like I said, I'm new to this and would like to hear your take on this .Thanks

 

[cally88]

well this is an interesting question that can require a minor science lesson. Long story short is that their compressor probably did fill up to 4500 psi, but here is the science part:

when jamming a bottle full of air the compression process heats up the air (feel the bottle when filling from compressor or even when filling your PCP from CF tank) warm air takes up more volume so when they finished the fill at 4500 it was with hot air. Then as the hot air cools in the tank you get to see the pressure slowly decrease.  

In order to get a full 4,500 psi fill my retailer requests me to leave my tank over night so they can fill and chill the tank then top off a chilled tank. they consistently fill me up to 4,400, but it takes quite a while.

Hope this helps.
Cally

 

[Guest]

Thank you Cally

 

[NMshooter]

I have been having the paintball center fill to about 4800-5000 psi. By the time I get home, I am about 4300-4400 psi. It depends on the center if they will do that or not but prior to that I was getting the same as you.

 

[cally88]

"FastEddie"Thank you Cally

NP

 

[pulps]

The paintball shop I used to go only turns on their compressor a few times a day to fill a large reservoir. Tanks are filled from that reservoir so depending on time of day, there can be more or less than 4500 PSI available. I've never been able to get a full 4500 PSI fill from any paintball shop. They also filled my tank incredibly fast. Fast enough to make me worry.

 

[bdb12586]

I also never had my tank filled to 4500 by the Time I'm home ion lucky of it's at 4k...im saving for a compressor. ..that mrod Compressor looks like a good deal

 

[NMshooter]

I just went to the paintball center and he filled it to 5000 psi. Checked it when I got home and it was exactly 4500 psi. Sometimes I have to wait 10-20 minutes for their compressor to reach that high if alot of shooters are there. You might want to ask what the pressure is at in their tanks.

 

[Odie]

I use diveshop near me, they fill customers tanks quite slowly to prevent heating up. My wife used the same shop to fill her scubatank and it has always been exactly what it should be, I guess divers don't take any BS when it's their life at stake....

 

[gorgata]

I get my tanked filled at the fire station and I asked them they said basics the same thing the warm air volume affects the psi gage so as it colls theres a slight decrese but its all good 1 loss on a fil is still better then 15 fill with a pump lol

 

[iride]

Your own compressor stops all the hassles,

Jim Sheldon is a good place to start.
If your really in the sport , Its money well spent.
Even for a cheap ass like me.
Mike 

 

[Tominco]

Try the firehouse. (Bring cookies!) There may be a chance that you'll need an adaptor for them to fill it. But, those guys should be able to take care of you the right way. If they give you any issues just tell them that you need a "trained professionals" help to show you how this gets done right because you do not believe you are getting safe or effective service at XYZ shop. 
Trained Professional = pat on back ("Qualified Professional" would work too)
help = that's their job and passion, helping people.
done right = challenge 
Safe or effective service = challenges them to show you the right way
XYZ shop = Might trigger them to stop by and see how they're operating. 

Filling these CF bottles too fast is not healthy for the bottles. It's called "Flash filling". Here's an article I just pulled up - http://www.psicylinders.com/inspectors/library/29-fast-fill-slow-fill-does-it-make-a-difference In the beginning it makes it sound just fine to flash fill but, read on...

Regardless, we're dealing with extremely high energy that can kill. This is one part of the process that you want to respect and take your time with. I've also see guys fill their rifles so fast it made me want to duck! Slow it down a bit. If a filling event goes bad, it's going to go bad big time! 

Fast Eddie - Are you using a microbore hose? If not, get one! They make a big difference. 1 FOOT of microbore hose holds the same air as 1 INCH of the standard industrial 1/4" hose. That makes a noticeable difference when you bleed out the line. 
Happy shooting!
Tom

 

[Dan25]

I agree with Tom on going to the Fire Dept. I have a friend there and get free fills. Even with the slow fill adapter on my tank it gets warm on a fill and I loose several hundred psi on the cool down. But Im not looking the gift horse in the mouth. R&L sells a nicely made one piece stainless firehouse adapter for a good price.

 

[linsfreak]

hate to cut in, but truly no need to fill all the way.

 

[iride]

All the fire Dept around my area will not fill for insurance reasons,,,
I even know some of the firemen , But it was of know help...
Mike

 

[Vealboss]

Being a firefighter, I can tell you with 100% assurance that the city I work for would not allow us to fill any outside bottles. That being said, if I knew someone that had a bottle with a current hydro I would bring it to work and fill it for them on the down low. We fill bottles all the time, cause we have to only compressor in town at my station. I have tried to see how slow I could fill a bottle and monitor the heat. Even with the compressor feeding in 20-30 psi a min the bottles heat up. If you want a full 4500 psi in the bottle they are going to have to over fill it, or take the time to let it cool back down before topping it off. Now if I can just figure out how to get one of those bottles to use on my days off
jeff

 

[30cal]

Funny but I don't have that problem with my "slow" Shoebox Max compressor. ;-) When it says 4500 on the gauge I stop and it stays there. Some think they are to slow but there is at least two positives to it. The first of course being the low cost. Plus I like being in control of the whole process.

 

[linsfreak]

Agreed! Same with my shoebox!

 

[ajshoots]

I set my Shelden compressor for around 4700psi. Tanks end up right at 4500psi. Just topped off both my tiger shark and guppy last night from around 3200psi to 4700 and they cooled right at 4500. Exactly 10 minutes from start to finish. My tanks get warm but not hot. When I had our volunteer fire dept filling my tanks, they filled from a bulk system. Tank was full in about a minute or so. Tanks definitely got hot and they would only fill to exactly 4500. When cooled off, I normally had 4100.

Do the Omega style compressors fill slow enough to maintain what ever you fill to, or do they also build alittle heat in the tanks resulting in a slight drop in final pressure?

 

[Rubicon_Joey]

The "science" behind it can be explained by the Ideal gas law (PV=nRT). However, at the pressures we use in the PCP world; the "law" starts to break down and more factors need to be taken into account (Van der Waals equation).