Fill hose air loss

[JonnyReb]

  Hey guys
  Just wondering in anyone has come up with a solution to this issue. When i fill with my 3000psi scuba tank, i fill to the 3 bar mark. When i bleed the hose before disconnecting, my rifle pressure drops to 2750 or so. I now see why long fill hoses are not considered a good thing. Sure seems like a lot of air wasted.  Any good way around this?     J

[PeakChick]

Jonny, is the fill hose you are using a micro bore hose? They use, and waste a lot less air than standard diameter steel braided nylon hose.

[JonnyReb]

 Excellent,  that would help a lot i'm sure. The hose i'm using is probably the one marketed by air ventura, it came with the kingman fill station valve. It is a cheap hose and appears to have swelled in external diameter to apprx 7/16th with an internal diameter of 3/16th or so. A tiny inner diameter, shorter hose and a stronger hose would make a huge difference.  Thanks for the info, i never considered that..  thanks PC

  Thats another good tip, thanks SS, i'm bleeding very slow so i don't scare the cats to bad    they do crazy things when they freak out.. guess they'll have to deal with it.. i'll speed up my bleed time.. J

[Filnez]

You can slip a piece of weedeater line inside the hose to take up air volume to cut down on the wasted air.  Find a diameter just smaller than the inside diameter of the hose, cut it to the length you need, and put it in the hose after unscrewing it from the fill adaptor. 

"Bleeding" is simply letting off the air pressure in the line between the inlet valve on the rifle and the supply tank shutoff valve.  It should make zero difference whether you let off the pressure fast or slow.  Aside from scaring the cats, they HATE it when you zip open the bleeder screw and the loud HISS comes out, they run like heck!  If the rifle's indicated gauge pressure drops when you let the air out of the fill adaptor hose, something is wrong.  No air should be escaping the rifle's fill valve on the air reservoir.

When a hand pump is used, you should open the pumps pressure bleed screw quickly, so the blast of fast escaping air will take out moisture trapped in the pump with it. 

I've never tried it, but I'd bet that if you jerked the hose off the rifle while the hose is still fully pressurized that it could knock the tar out of you. I've let go of regular shop pressure air hoses at just 120 psi and been whacked pretty hard.   

[JonnyReb]

 Yeah i read about "hose whip" and decided i didn't want none of that.  That is a fantastic idea about the weedeater line, thank you for sharing it, all these tips have helped me tremendously,  thanks all.   J

[Rodents Rapture]

 That's a very simple fix. Install a slide-check valve at the fill end of the line. It'll clear the air in the fitting allowing you to disconnect. The line will hold the air within preventing any loss. You'll have to change the urethane o-rings for high pressure but that's very simply. I have several replacement o-rings that work perfect for my app to 3000psi.

[JonnyReb]

  Just tried a fill with as quick a release on the bleeder valve as i could manage. I only lost about 50psi, what a huge difference in itself. With the other mods, i could see losing almost none, thanks guys.. J

[Filnez]

[quote author=Filnez l

"Bleeding" is simply letting off the air pressure in the line between the inlet valve on the rifle and the supply tank shutoff valve.  It should make zero difference whether you let off the pressure fast or slow.  "

 That is NOT correct (on most airguns).
No "most' airguns (Career, Sumatra, Discovery, others) if you just barely open the bleed valve you can dump ALL the air in the rifle. This is a good way to remove air if it wont fire and you need to empty it. On these and other airguns it is only the air pressure inside which closes the check valve on the fill unit.
 So, bleeding VERY slowly will entirely empty the airgun. Bleeding somewhat slowly will casue it to loose some air. Dont believe me just give it a try and or look at some fill valve diagrams.
 Bleed AS FAST as you can.

 John

What would explain why something like this could happen?  The instant you let any pressure at all out of the hose, the pressure in the gun's reservoir would now be higher than the pressure in the hose, and the guns "fill valve" check valve should allow no air whatsoever to exit the reservoir?  I don't have a host of examples to test this out on, just one rifle, my Evanix Renegade, and fast or slow bleeding the fill hose has never made any difference whatsoever in the pressure showing on the gun's gauge. 

[JonnyReb]

 Hi  filnez,  must be that the check valve in the gun needs a fast drop in pressure on one side to quickly activate the valve to close. A slow drop/bleed isn't enough variable in pressure to allow the valve to "snap" closed. No doubt though, it makes a huge difference..  Jeff

[Pete]

Hi..
The gun should not drop preassure when yer bleed down..
line/hose size has nothing to do with it...the non re-turn valve
in the gun is slow to close....chance is there is dirt in it and while the
preassure is at a simular psi each side the valve will not seat..
Its only when the psi in the fill line drops that the pressure in the
gun can seat the valve...but by this time some air has exscaped
from the gun.....Or maybe a weak spring in the valve...
When the pressure is the same on each side of the guns valve
the spring in the valve shoud seat it...it only opens when the
 pressure in the fill line/tank is higher than whats in the gun..
Once they have equalised " your fill psi" the valve closes...bleed down
and NO air can exscape from the gun as the spring has already closed the
valve....This is NOT happening in your gun...

So dump the air FAST....

Pete

[JonnyReb]

   Will do Pete.. i've got it down to a sub-second release and it seems to work fine that way.  If it get worse(ie. weak spring, dirty etc) i'll get another valve. I appreciate everyones responses.   Jeff

[only1harry]

Another (very strong) possibility is that you are filling the gun too fast from the Scuba tank.  You must fill the gun's tank very slowly to get an accurate reading of the real pressure in the gun.  If you fill fast, you heat up the air in the gun, the tank gets hot, and then the pressure in the gun drops later to what it really is, what you are reading - 2,750psi. 

Also most Scuba shops do this with your 3k psi tank.  They fill them too fast, sometimes to 3,100-3,200psi (because they know it will drop hours later) get them hot, and later in the day or the next day the actual pressure in the Scuba is 2,800psi when the air in the tank cools down.  Also be aware that you cannot get multiple 3k psi fills with a 3k Scuba tank.  Even if the Scuba has 3k psi in it, you will only fill your gun with 1-2 fills at that pressure.  The pressure in the Scuba will start dropping gradually every time you fill the gun. 

So basically a 3k psi tank alone is not the best choice for big bore Korean guns that require 3k psi to get the proper power out of them.  You should have a pump to top off the gun's tank to 3k psi, or get a 4,500psi tank.  3k Scuba tanks are good for the Disco (2k psi max.), Marauder - which most people fill to 2,500psi, and Talon/Condor which get a lot of power from just 2200-2600psi.