GTA

All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: wahoowad on July 04, 2016, 01:47:32 PM

Title: 100 psi pressure drop at top of fill?
Post by: wahoowad on July 04, 2016, 01:47:32 PM
I charge my Marauder to 2700 psi but notice I actually have to fill to 2800 because it drops down about 75 to 100 psi right after reaching 2800. Its like it settles in to 2700 but then doesn't drop any further. Here's the actual steps:


I use this regulator but don't normally touch the adjustment knobs as it is set to only fill to 2800. I don't hear any air being lost, it's like it is just equalizing or something. There is no regulator inside the gun. Again, it just drops that 100 psi and stops. Then works normally as I shoot. I have the regulator on my tank as I often shoot tethered, and also use different pressures with different PCPs.

(http://i.imgur.com/ODC1n71.jpg)

Title: Re: 100 psi pressure drop at top of fill?
Post by: Geoff on July 04, 2016, 01:51:00 PM
taking a guess here


gets hot filling then cools down ?
Title: Re: 100 psi pressure drop at top of fill?
Post by: scrane on July 04, 2016, 02:10:45 PM
Good guess!
Title: Re: 100 psi pressure drop at top of fill?
Post by: PlanB on July 04, 2016, 02:30:23 PM
i think they all do it.
Title: Re: 100 psi pressure drop at top of fill?
Post by: screwwork on July 04, 2016, 02:54:11 PM
Nobody else said it so I will, nice tank & pressure reg setup :D
Title: Re: 100 psi pressure drop at top of fill?
Post by: Charles Outdoors on July 04, 2016, 02:58:20 PM
Sounds normal to me. I always have to go over a little to get it to settle to the PSI I want.
Title: Re: 100 psi pressure drop at top of fill?
Post by: rsterne on July 04, 2016, 04:01:14 PM
Yep, normal to lose about 100 psi on cooling....

Bob
Title: Re: 100 psi pressure drop at top of fill?
Post by: wahoowad on July 04, 2016, 04:09:35 PM
So this 'cooling' occurs immediately, like within a couple seconds and I drop 75 psi?
Title: Re: 100 psi pressure drop at top of fill?
Post by: Ribbonstone on July 04, 2016, 04:40:05 PM
Pretty fast  Air gets hot from compression, but it has a kind of large metal surface area (air tube) to conduct/transfer the heat.

Ball park number would be 5 PSI per degree of change (actually, it's something between 5 and 6psi, but we're just talking "do it in your head" type figuring rather than working through the gas laws).
Title: Re: 100 psi pressure drop at top of fill?
Post by: anuthabubba on July 04, 2016, 04:58:49 PM
On my first Daystate in '90, the 'experienced guys' instructed me to refill it slowly, over at least a minute and a half, to help reduce pressure loss (shot consistency) due to heating/cooling.

This comes to mind every time I read of guys being able to fill their SCBA tanks, with their compressors, in just a couple minutes.
Title: Re: 100 psi pressure drop at top of fill?
Post by: Ribbonstone on July 04, 2016, 06:50:09 PM
Few tank fillers seem to be willing to wait a whole minute for a fill...tanks breed impatience.
Think most just overshoot a bit and hope it cools down to what they wanted.
Title: Re: 100 psi pressure drop at top of fill?
Post by: marty2 on July 04, 2016, 09:38:17 PM
All my PCP rifles do it. I leave everything hooked up for a little until the pressure stabilizes then slowly bring up the pressure  to  the desired level.