“So how much air in a NitroAir Cartridge?” That’s a question I have wondered about for some time. So my plan was to find a theoretical answer by calculation, then check the results by practical testing. Simple, right?
Although this may not be immediately obvious, this post is the second part of my review of the Umarex NitroAir Fill Station. Part One can be found here.
How Much Air In A NitroAir Cartridge? – Basic Data
Unfortunately, Umarex doesn’t tell us the answer to this question. However they do give us enough information to calculate an answer…
A NitroAir cartridge contains 32 Grams of Nitrogen gas (N2), at a pressure of 3,600 PSI. It says that right on the bottle. By simple conversion, we can establish that 32 Grams is approximately 1.13 Ounces.
Then there’s something called the Ideal Gas Law. It has a formula which many of us will recognize. It’s: PV = nRT
In this formula, “P” is Pressure, “V” is Volume, “T” is Temperature, “R” is a fixed gas constant and “n” is the number of “moles”, that’s a value inherent in the mass of the gas. In this case we are using the value of 1.142.
Fortunately for my feeble brain, there’s an online calculator to do the heavy lifting here. So I used that to make my calculations.
How Much Air In A NitroAir Cartridge? – First Calculations
First I used the online calculator to establish the volume of N2 that should be in the NitroAir cartridge. Using the 32 Grams and 3,600 PSI product claims, we can calculate the volume of gas in a NitroAir cartridge.
While the pressure of Nitrogen gas is reasonably constant at different temperatures, I also calculated the expected pressures for a range of temperatures. We can see the results in the chart below.
So the calculations confirm Umarex claims of 3,600 PSI for the pressure inside a NitroAir cartridge. In fact, the calculation gives 3,590 PSI at 75 degrees F. That’s very reasonable.
My calculations suggest that each NitroAir cartridge should contain around 114 cc of Nitrogen gas at about 3,520 PSI in the relatively-constant 65 degrees F temperature of my basement range.
For confirmation, I set up a test including a pressure gauge connected to the Fill Station.
Then I fitted a “dead head” plug and opened the valve.
The result shows 3,250 PSI.
Why the difference between 3,520 and 3,250 PSI? Well, there’s a number of possibilities depending on the accuracy of the gauge (the spec is +/- 1.5%), the actual – as opposed to specified – amount of N2 in the cartridge and the exact temperature.
Also there’s some gas volume “lost” in each test through the volume of that gauge and connectors between the NitroAir cartridge and the gun. This calculated to approximately 1.5% of our 114 cc of Nitrogen cartridge, too. So, my test results likely very from the calculated results due to multiple factors.
That difference between actual and calculated values is around 8%. I would say that’s pretty close for a simple experiment and the known variabilities.
How Much Air In A NitroAir Cartridge? – Testing A Notos G1
Having decided to use an Umarex Notos G1 as the test gun, I first de-gassed it. That gave me a “zero base” to start from, matching the calculations – well actually that should probably be about 14 PSI, as the gun’s HPA tube now contained ambient air at atmospheric pressure.
Next, I connected the Notos to the Fill Station with the pressure gauge in place. To my initial surprise, the gauge read just 1,700 PSI.
Why not 3,600 PSI?
Some thought led to the conclusion that – on opening the Fill Station Valve – N2 fed into the gun, initially at 3,600 PSI pressure. However, as the amount of N2 in the gun increased, the pressure in the N2 cartridge fell significantly and rapidly.
At some point – which will depend on the HPA capacity of the gun being filled – the increasing pressure (of existing air plus N2) in the gun “balanced” with the remaining pressure in the N2 cartridge. That’s why my fill stopped at 1,700 PSI with that pressure in both the gun and N2 cartridge.
This result is due to the small volume of pressurized gas in the NitroAir cartridge.
By comparison, even a relatively small HPA tank has a volume of 90 cubic Inches. That’s about 1,475cc. So, filling a 66cc capacity Notos G1 uses less than 5% of its volume. This means that the 3,600 PSI tank pressure falls very little during a fill.
The same 66 cc Notos tube would use a significant portion – likely exceeding 50% – of the 114 cc of N2 in the NitroAir cartridge. That’s why the cartridge pressure fell down to 1,700 PSI.
Next, I repeated the exercise with a second NitroAir cartridge, starting from the 1,700 PSI fill pressure produced by the first fill. Now the pressure balanced-out at 2,500 PSI.
I could have repeated the process again, to further increase the pressure in the gun. However it may well have taken a total of four NitroAir cartridges to completely fill the small HPA tube of the Notos G1.
However, remember that the second N2 cartridge provided a significant boost in pressure over the 1,700 PSI fill of the first cartridge.
As the Notos regulator usually is set at between 1,500 and 1,800 PSI by the factory, the NitroAir Fill Station IS a viable way to increase pressure back above the regulator set point and achieve additional full power shots.
How Much Air In A NitroAir Cartridge? – Conclusions
1. We found out that Umarex NitroAir cartridges contain around 114 cc of 99.999% pure Nitrogen gas. That means that there’s guaranteed to be no “wet air” when using them to fill your PCP airgun.
So if you shoot an Umarex Komplete using N2 cartridges, your gun is pretty-well guaranteed to be immune from corrosion issues caused by water vapor in High Pressure Air. That – in itself – is a HUGE long-term benefit for NitroAir and the Komplete platform that I have not seen highlighted before.
2. Using the NitroAir Fill Station with an N2 cartridge can be a very viable way to give a PCP air rifle that’s running short on air a rapid pressure boost in the field. However it’s likely to work best with guns having a relatively limited HPA capacity, like the Notos, due to the limited volume of N2 in the cartridge.
For guns with larger HPA capacities, it may be necessary to boost using two cartridges in succession. But IT DOES WORK!
3. Yes, you can use it to fill a PCP air rifle from empty. But it’s not at all efficient in doing so. Using three, four or more NitroAir cartridges is unlikely to be a cost-effective solution for most owners. Plus, there’s that 3,600 PSI maximum pressure limitation.
Filling completely from empty does work, but I can’t recommend it for cost reasons.
4. Overall, I feel that there is some confusion about how the Fill Station is positioned from a marketing perspective. It’s not really a “Fill Station”. It’s actually a “Top Off Station”. Seen in that light, the product has a good benefit profile.
5. So yes, the Umarex N2 Fill Station actually can deliver an endless supply for dry air for your PCP airgun.
True, lower-priced NitroAir cartridges would make it more attractive. But – for the right gun and owner – it can be a viable solution that bears comparison with the other (also expensive) methods of protecting your PCP air rifle.
There’s no free lunch when it comes to preventing internal corrosion in PCPs. The Umarex approach at least allows you to begin with by far the lowest up-front cost. For some owners, that could be a deciding factor.
BUY FROM PYRAMYD
Umarex N2 Fill Station
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