Issue with my refilling from my 6.8l 4500psi CF tank

[Milf Dots]

The other day I was out shooting my rifle. Which was the FX impact M3 and when my pressure got low, I hooked up my CF tank to refill the pressure at 190 bar and I slowly opened the valve to repressurize the bottle on the gun, but it would only pressurize to about 260 bar with the valve completely open it wouldn't go all the way to 300 bar. This happened twice to Me. The temperature outside was about 45degrees Fahrenheit, so it was quite cold. But I'm quite new to ant issues and resolving them with a CF tank. Has this happened to anyone else? Could it be the temperature outside was affecting airflow? Maybe the valve I have ? Which is the IORMAN one off of amazon with the red valve handle. Any help would be awesome!

 

[Ezana4CE]

What was the fill pressure in your SCBA tank? Were you on a fresh top off? Have you ever had issues with your SCBA tank gauge readings? How about the gauge on your M3? Temps shouldn't drop the pressure that much.

 

[Milf Dots]

4500

 

[Milf Dots]

Everything is brand new, and have never had issues before

 

[qball]

If it is cold and if you have some moisture in the tank then it could clog but should be rare.

BUT keep in mind that FX manual says fill up to 250 bars even though the bottle can go up to 300 bar. Personally I rarely fill above 230 bars.

 

[Milf Dots]

I have the 300 bar bottle, the Airmarksman one

 

[Ezana4CE]

I'm puzzled, but interested in learning what may be the cause of this problem. I hope it's an easy fix.

 

[Milf Dots]

I'm puzzled, but interested in learning what may be the cause of this problem. I hope it's an easy fix.

yea me too

 

[WorriedMan]

I have the 300 bar bottle, the Airmarksman one

Did you upgrade to 300 BAR valve to go with upgraded bottle? Could be way off but seem to recall you need both for 300 BAR fill.

 

[bigHUN]

Regardless that you have a 300 or 400 or 500 bar bottle, but the gun was designed with tolerances on seals (orings) not to exceed 250 bar. Imagine in hot or cold how the tolerances can seal the same. Car turbos not perform the same in different climate or altitude, Florida or Canada, sea level or high lands.
We need to be reasonable what to expect and how to handle.

 

[nervoustrig]

The only thing I can think of is the check valve isn't opening very far, and when filling slowly, a sufficient differential pressure isn't being maintained and the check valve is closing. There is a good opportunity for it to occur if the check has an assist spring.

To better explain the dynamics at play here...if at any point during the fill, the check valve closes, it will require a pretty substantial pressure differential to open. For example I grabbed a Foster fitting from my parts box and its integral check has a 0.130" dia pin and an O-ring with a sealing diameter of approximately 0.150". So in a hypothetical initial state where the gun is pressurized at 260 bar, hitting it with 4500psi (310 bar) is insufficient to push it open. That's because there's about 67lbs of force holding the valve closed versus only about 60lbs of force trying to push it open.

 

[Milf Dots]

Regardless that you have a 300 or 400 or 500 bar bottle, but the gun was designed with tolerances on seals (orings) not to exceed 250 bar. Imagine in hot or cold how the tolerances can seal the same. Car turbos not perform the same in different climate or altitude, Florida or Canada, sea level or high lands.
We need to be reasonable what to expect and how to handle.

That's not true, the impact m3 was designed for the use of 300 bar bottles. It just comes stock with a 250bar bottle This is directly from the mouths of FX technicians.

 

[Blejda]

Tank heated so much if it was filled from empty that when it cooled down the prresure inside droped. I fill my tank at the fire station from 200-300 bar.When it cooles down the prresure inside is only around 270-280 bar.
If i would fill it from 0-300 bar the difference in pressure drop would be bigger because of extra heat and expansion of air.

 

[Humdinger]

Here's my .02 cents. I think there isn't an issue other than the two gauges don't have the same accuracy. Unless you had digital gauges on both your tank and your air gun there is typically a difference in the pressure reading on the gauges. I've had lots of times when a tank is reading higher than a PCP gauge when both are wide open. For instance, the tank will read that it has 3800 psi remaining and the rifle gauge stops when it reaches 3600 psi. Temperature only is a factor if the tank and rifle at two widely different temperatures during a fill. For instance, the rifle was in a cold car trunk but the tank was in a warm house. The 28mm analog gauges on most air rifles are often less precise than the large output gauge on air tanks.

 

[starlingassn]

same as above.
my tank pressure gauges never coincide with any other gauges.

i have one tank that will show 3k+ but will only fill to 2500psi or so.

 

[Gerry52]

Normal to have a 200-300psi difference from "filled" temp to cooled off temp of tank. If your gun currently has a 250 bar bottle DON'T go above that. The gauges used on our tanks, bottles & guns are notoriously inaccurate, close but inaccurate. I wouldn’t sweat about it too much.

 

[Milf Dots]

So I believe I found out what the issue was, the valve that I purchased only has an 800psi output, thus (from everything thing that I've read) meaning it's only capable of pressurizing up to 250bar not 300.

 

[jarmstrong]

show us the valve, link please

 

[starlingassn]

show us the valve, link please

yes,show the valve.

that doesnt make sense to me.

 

[bchannell]

Ok, it sure sounds like a cool cylinder issue. If it was filled to 4500psi and the bottle got to lets say 120F after the fill. Then you cooled it to 45F, the pressure in the cylinder would now be in the 3800psi range or......guess what 260BAR. Perfectly normal.