So lets be honest, whether you're using a Yong Heng, a DAVV, an Air Venturi, (etc) to fill your CF dive tank, they all by and large operate the same way, and are susceptible to the same issues. Those little compressors operate under a tremendous load. And the harder you push them, the more likely a failure. Some of the compressors say they are designed to fill up to 4500 psi, but in the same sentence they will say 300 BAR. Which is actually 4351 psi, not 4500 psi. Some compressors will say 310 BAR, which is a true 4500 psi. However, to push pressure beyond that is a risky endeavor. Can the compressor do it.... Yes. But for how long? In pushing mine to extreme pressures (beyond manufacturer recommendations), I've had failures. And there's nothing more frustrating waiting 3-4 weeks for parts from China to arrive in order to fix it. So the following is my personal experimentation on how to achieve max pressure in your CF tank without pushing your compressor to it's limits. The less strain you can put on the compressor, the longer it will last. I have no problem pushing my compressor to 4500 psi. It's a DAVV 2 stage compressor. But I don't like to push it beyond 4500. But there are guys on here who may not like to push their compressors beyond 4100 or 4200 psi. What is I told you there's a way to get 4500 psi in your CF tank only pushing your compressor to 4100 or 4200 psi? Let me explain.
The air in that CF tank is under tremendous pressure. Have you ever noticed that if you store the tank in a cold environment, the pressure gauge will drop? This is because the cold air increases on the exterior of the tank increases the density of the air inside the tank as it cools. This is the 2nd Law of Thermodynamics as it pertains to equilibrium. As the air heats up, it expands. As it cools, it becomes more dense and contracts. So this is what I do. I've attached pictures for you to see. I'm confident I can push my compressor to 4500 psi, but if you don't want to push yours that high, then that's perfectly fine. It's entirely up to you.
The first picture is the starting pressure on the tank. The angle is weird, but it's 4500 psi on the dot. This was after filling the tank to 4500 psi in a 60-70 degree environment, letting it settle, and topping it off to ensure it was locked in at 4500 psi. It's very important this step be done in a room temperature environment for consistent fill pressure:
Next picture is how to get the air to become more dense before adding more air. I stuck my tank in a small trashcan, filled it with ice, added water to make a slushy slurry, and left it sitting for 20-25 minutes:
After 20-25 minutes, the pressure in the tank dropped from 4500 psi to about 4150 psi. This is confirmed on the gauge on the tank itself as well as the pressure gauge on the pump when it regulated with the pressure in the tank as I started to refill it. Leave your CF tank in the ice water the entire time your filling it back up. :
After topping back off to 4500 psi, I removed the CF tank from the ice bath, and set it in my normal storage spot in my garage at home. I live in San Diego, so my garage typically hovers between the low 60's and the low 70's. After the temperature of the air in the bottle equalized with the ambient temperature of the air in my garage, this is what the pressure gauge on the CF bottle read:
Now to all the naysayers out there that are going to focus in on safety, the bottle is hydro-tested at 2x's the suggested storage pressure, and the burst disk on the valve assembly of the bottle is 6000 psi. I'm thinking the pressure is hovering at 4900-5000 psi after doing this. Easily within safe storage pressure. But if you pushed your compressor to 4200 psi, stuck the CF bottle in the ice bath for 30 minutes, dropped the pressure to 3800, then topped it back off to 4200 psi, when the air temp in the bottle equalized with the ambient air temp of your garage or house, the pressure would creep up to 4500-4600 psi. And you never pushed your compressor to the upper limits of it's capabilities.
It's just something I do to maximize the pressure in my bottle (i.e. I got 10 more top-off's on my air rifle by doing it this way). But if you think this is something you might like to try, I've shared it with the world.
My disclaimer is this however..... I'm not liable if you push your bottle too far. I recommend going no higher than 4500 psi on your compressor- EVER!
The air in that CF tank is under tremendous pressure. Have you ever noticed that if you store the tank in a cold environment, the pressure gauge will drop? This is because the cold air increases on the exterior of the tank increases the density of the air inside the tank as it cools. This is the 2nd Law of Thermodynamics as it pertains to equilibrium. As the air heats up, it expands. As it cools, it becomes more dense and contracts. So this is what I do. I've attached pictures for you to see. I'm confident I can push my compressor to 4500 psi, but if you don't want to push yours that high, then that's perfectly fine. It's entirely up to you.
The first picture is the starting pressure on the tank. The angle is weird, but it's 4500 psi on the dot. This was after filling the tank to 4500 psi in a 60-70 degree environment, letting it settle, and topping it off to ensure it was locked in at 4500 psi. It's very important this step be done in a room temperature environment for consistent fill pressure:
Next picture is how to get the air to become more dense before adding more air. I stuck my tank in a small trashcan, filled it with ice, added water to make a slushy slurry, and left it sitting for 20-25 minutes:
After 20-25 minutes, the pressure in the tank dropped from 4500 psi to about 4150 psi. This is confirmed on the gauge on the tank itself as well as the pressure gauge on the pump when it regulated with the pressure in the tank as I started to refill it. Leave your CF tank in the ice water the entire time your filling it back up. :
After topping back off to 4500 psi, I removed the CF tank from the ice bath, and set it in my normal storage spot in my garage at home. I live in San Diego, so my garage typically hovers between the low 60's and the low 70's. After the temperature of the air in the bottle equalized with the ambient temperature of the air in my garage, this is what the pressure gauge on the CF bottle read:
Now to all the naysayers out there that are going to focus in on safety, the bottle is hydro-tested at 2x's the suggested storage pressure, and the burst disk on the valve assembly of the bottle is 6000 psi. I'm thinking the pressure is hovering at 4900-5000 psi after doing this. Easily within safe storage pressure. But if you pushed your compressor to 4200 psi, stuck the CF bottle in the ice bath for 30 minutes, dropped the pressure to 3800, then topped it back off to 4200 psi, when the air temp in the bottle equalized with the ambient air temp of your garage or house, the pressure would creep up to 4500-4600 psi. And you never pushed your compressor to the upper limits of it's capabilities.
It's just something I do to maximize the pressure in my bottle (i.e. I got 10 more top-off's on my air rifle by doing it this way). But if you think this is something you might like to try, I've shared it with the world.
My disclaimer is this however..... I'm not liable if you push your bottle too far. I recommend going no higher than 4500 psi on your compressor- EVER!
