GX CS4 fill times

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Humdinger

Humdinger

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Jun 3, 2015
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Charlotte, NC, United States
GX factory literature rates the GX4 and GX4-1 air output rating at 11 liters per minute at 1 bar. That equates to 22 liters per hour @ 4500 psi or 310 bar.

Most owners fill their SCBA tanks to 310 bar. That means a 6.8 liter tank X 310 bar holds 2108 liters of air @ 4500 psi. It takes 3 hours 12 minutes to fill a 6.8 liter tank from 0 to 4500 psi using the factory advertised fill rate.

A 9 liter tank holds 2790 liters of air at 310 bar or 4500 psi. That means using the factory rated output of 11 liters per minute it takes 4 hours and 13 minutes to fill a 9 liter tank from 0 to 4500 psi using a GX CS4.

A 500cc cylinder holds 125 liters at 250 bar. Filling a 500cc PCP air cylinder to 250 bar takes 11 minutes 22 seconds from empty.

Output air filters and other variables may affect these fill times slightly but this gives a general idea of the fill rates for this compressor.
 
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Humdinger said:
GX factory literature rates the GX4 and GX4-1 air output rating at 11 liters per minute at 1 bar. That equates to 22 liters per hour @ 4500 psi or 310 bar.

Most owners fill their SCBA tanks to 310 bar. That means a 6.8 liter tank X 310 bar holds 2108 liters of air @ 4500 psi. It takes 3 hours 12 minutes to fill a 6.8 liter tank from 0 to 4500 psi using the factory advertised fill rate.

A 9 liter tank holds 2790 liters of air at 310 bar or 4500 psi. That means using the factory rated output of 11 liters per minute it takes 4 hours and 13 minutes to fill a 9 liter tank from 0 to 4500 psi using a GX CS4.

A 500cc cylinder holds 125 liters at 250 bar. Filling a 500cc PCP air cylinder to 250 bar takes 11 minutes 22 seconds from empty.

Output air filters and other variables may affect these fill times slightly but this gives a general idea of the fill rates for this compressor.
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How long would it take to fill a 88 cubic ft. SCBA tank, from 0 to 4500 psi?
Im confused!
 
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Airgun Al said:
How long would it take to fill a 88 cubic ft. SCBA tank, from 0 to 4500 psi?
Im confused!
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That's because you are using the wrong term (no fault of yours, terms are bandied about that aren't quite as accurate, but they get the point across); there is technically no such thing as an 88 cu ft SCBA tank, nor a 97 cu ft, though those terms are commonly used (and confusing for people, old pros and newcomers alike. Some also refer to SCBA tanks by their breathing time (which makes zero sense for us, since we aren't firefighters, and time is irrelevant, since it all comes down to one's lung capacity and level of exertion.

Four common sizes of SCBA tanks (yes, there are several more, depending on whom makes the tank) are below. The first two values are actual WATER VOLUME measurements, and are actually the best way to compare sizes, since water isn't compressible, and air is. The other two are kind of thrown about with less precision by various groups:

114 cu in (1.9L) <20 cu ft> <15 minutes?>
285 cu in (4.7L) <45 cu ft> <30 minutes> Actually holds 1,457 L (51 ft^3) of air @310 bar.
410 (6.7L) < 60/73 cu ft> <45 minutes> Actually holds 2,077 L ( of air @ 310 bar; 1,675 L (59 ft^3) of air @250 bar.
550 cu in (9L) <88/95/97 cu ft> <60 minutes> Actually holds 2,790 L (98.6ft^3) of air @310 bar, 2,700 L (95.3 ft^3) of air @300 bar (you get the idea).

The reason for the various cu ft numbers is because air is compressible, so depending on pressure, one can have more or less of an air volume. Post #1 properly identifies tanks by their water volume, therefore his maffs is sound.

HTH

(His math on the fill times I cannot agree with, because as the pressures get higher, the compressor output will diminish by an unknown amount. Also, as things heat up, less air will fit into the tank, which results in a lower volume & pressure once it cools down to ambient once again. This can be overcome by step-filling.)
 
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Humdinger said:
GX factory literature rates the GX4 and GX4-1 air output rating at 11 liters per minute at 1 bar. That equates to 22 liters per hour @ 4500 psi or 310 bar.

Most owners fill their SCBA tanks to 310 bar. That means a 6.8 liter tank X 310 bar holds 2108 liters of air @ 4500 psi. It takes 3 hours 12 minutes to fill a 6.8 liter tank from 0 to 4500 psi using the factory advertised fill rate.

A 9 liter tank holds 2790 liters of air at 310 bar or 4500 psi. That means using the factory rated output of 11 liters per minute it takes 4 hours and 13 minutes to fill a 9 liter tank from 0 to 4500 psi using a GX CS4.

A 500cc cylinder holds 125 liters at 250 bar. Filling a 500cc PCP air cylinder to 250 bar takes 11 minutes 22 seconds from empty.

Output air filters and other variables may affect these fill times slightly but this gives a general idea of the fill rates for this compressor.
Click to expand...
Steve, had these been available when I bought my Alkin, I likely would have gone this route. That said, the CS4 is pretty young yet, so longevity is still unknown. The portability and low power requirements are fantastic attributes, and the slow fill speed should help keep bottle temp down. If I had my druthers, I’d have one as well as the Alkin. I top off my 2-45 minute, and 1-60 minute bottles in under a 1/2 hour, but that speed and volume are not necessary for me at all. I have zero regrets with my Alkin, and I don’t worry about it failing, which is why I bit the bullet in the first place. I wish all the GX users the best of luck, so far they are very promising indeed!
 
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Scotty1 said:
Steve, had these been available when I bought my Alkin, I likely would have gone this route. That said, the CS4 is pretty young yet, so longevity is still unknown. The portability and low power requirements are fantastic attributes, and the slow fill speed should help keep bottle temp down. If I had my druthers, I’d have one as well as the Alkin. I top off my 2-45 minute, and 1-60 minute bottles in under a 1/2 hour, but that speed and volume are not necessary for me at all. I have zero regrets with my Alkin, and I don’t worry about it failing, which is why I bit the bullet in the first place. I wish all the GX users the best of luck, so far they are very promising indeed!
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Well said. For me, price wasn't the issue, size and portability were. Once I get the space I need, I will likely own a nice Alkin or Bauer, but for now, the CS4-I is doing exactly what I need it to do. Fits in the house, the truck, the boat, etc.
 
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F6Hawk said:
Well said. For me, price wasn't the issue, size and portability were. Once I get the space I need, I will likely own a nice Alkin or Bauer, but for now, the CS4-I is doing exactly what I need it to do. Fits in the house, the truck, the boat, etc.
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They are great indeed. Hope it will stand the test of time.Grass
 
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@F6Hawk, I agree with your post in this thread about fill times. However, my fill times are as close as potential buyers need to know in order to get a realistic idea of what the GX- CS4 can do. I am fully aware of the VanDerWaal effect on compressible gases. It's the reason that certain retailers overstate the actual capacity of their tanks. Manufacturers like Scott and Luxfer do take the fact that air compression isn't linear into their specifications. Most air gun retailers do not. The one that does is Airhog.

For instance, just using volume x pressure suggests that a 9 liter tank at 310 bar holds 97.4 cubic ft. of air, but because air compresses less as the pressure increases means a 9 liter tank actually holds 88 cubic feet of air at 310 bar. If you do the math on my fill times in the original post, you will see that while it isn't exact, it's extremely close. If you go back and see my post about various tank sizes and capacity you will see that I did take the VanDerWaal calculation into account in expressing the capacity for each tank size.
 
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Humdinger said:
@F6Hawk, I with your post in this thread about fill times. However, my fill times are as close as potential buyers need to know in order to get a realistic idea of what the GX- CS4 can do. I am fully aware of the VanDerWaal effect on compressible gases. It's the reason that certain retailers overstate the actual capacity of their tanks. Manufacturers like Scott and Luxfer do take the fact that air compression isn't linear into their specifications. Most air gun retailers do not. The one that does is Airhog.

For instance, just using volume x pressure suggests that a 9 liter tank at 310 bar holds 97.4 cubic ft. of air, but because air compresses less as the pressure increases means a 9 liter tank actually holds 88 cubic feet of air at 310 bar. If you do the math on my fill times in the original post, you will see that while it isn't exact, it's extremely close. If you go back and see my post about various tank sizes and capacity you will see that I did take the VanDerWaal calculation into account in expressing the capacity for each tank size.
Click to expand...

Buddy, no need to explain it to me, I think your post is probably one of the most accurate ones on here about air and tank sizes. And it's great that you took time to post it, it is most appreciated. I only added what I did due to the fellow who was confused about his tank size.
 
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Been having an issue with the bleed valve on my CS4 leaking. I've used teflon plumbers tape to keep the air from bleeding past the bleed screw, but this needs regular replacement. Can someone check to see if there is a nylon, rubber or some other sort of material at the tip of the bleed screw?
My Hill has one, my tank bleed screws do also - just wondering why this darn thing leaks.

thanks.
 
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SDstephan said:
Been having an issue with the bleed valve on my CS4 leaking. I've used teflon plumbers tape to keep the air from bleeding past the bleed screw, but this needs regular replacement. Can someone check to see if there is a nylon, rubber or some other sort of material at the tip of the bleed screw?
My Hill has one, my tank bleed screws do also - just wondering why this darn thing leaks.

thanks.
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You need a new bleed valve then. The newer ones don't have a seal on the tip any longer. Contact GXO or the seller from whom you bought the machine. It's likely a warranty item.
 
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MACTEN said:
I had to re-fill the new 9L tank from 0 to 4500. It took 5.3 hours. This was with my older CS4 not the CS-4 I (using the internal model for rifle fills only so far) I have 35 hours on the CS4.
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Same compressor, as far as filling is concerned.

Did you do all 5.3 hours at once, or stage it? Did you bleed water every so often during those 5.3 hours?
 
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F6Hawk said:
Same compressor, as far as filling is concerned.

Did you do all 5.3 hours at once, or stage it? Did you bleed water every so often during those 5.3 hours?
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I bled the air at the half way point when the gauge showed about 155 bar. Made sure the coolant was still pumping and resumed. Same as the other times. I've filled a 6.8L and this same 9L the same way before.
 
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