SurfLung wrote:Compressor Fill Rate and Pressure
- Before re-ringing my RIX SA-3E compressor, I had thought it was filling tanks at around 2.5 cf/min. Then AFTER installing new rings, I tested it by filling my twin 38s from zero to 2000 psi. That's 84 cf and it filled them in 29 minutes. That's 2.9 cf/min.
- Then last weekend I filled 3 AL80s to 3000 psi, 1 steel HP80 to 3000 (65 cf), and 1 steel 72 to 2500 psi. My calculations figured the fill rate at 2.4 cf/min. 377 cf filled in 2:36... 156 min. 3 of the tanks were at or near empty.
- So here are my questions:
1. Does the fill rate slow down at higher pressures?
2. Or, does the fill rate go slower when tanks are nearly empty?
1. it would not be unusual to lose a little volume at higher pressures, especially before the new rings have fully broken in... but not necessarily just during that period. Also it is entirely possible that the motor speed is dropping a little at the higher pressure load. If you have or can borrow a mechanical tachometer that pushes against the center of the motor shaft you can detect that.
Without a tach, you could shoot video of the pulley or fan as it progresses from low pressure to highest, and the stroboscopic effect of the "shutter" will show a change in speed. That won't tell you how much, but it might give you a hint that the speed is changing.
2. I can't think of any reason for the blowby to increase at lower pressures. Blowby can actually increase with lower
speeds, but that shouldn't be happening during low pressure operation. Do keep in mind that if your beginning separator and filter pressures are lower than your starting cylinder pressure it will take more time to fill all that up to final pressure. (See #4)
3. Here is a question that I am not sure of the answer, but should also be considered. Are the 38's rated that at the 10% overfill to 1980 psi, as were most steel cylinders. If that is the case, you would only have about 76 cubic ft at your 2000 psi fill instead of your calculated 84. Try running your calculations for that cyl volume.
While on that subject, most aluminum 80's are really only about 77 at 3K.
4. Also to consider when filling is air volume in the filters. To take that factor out of the calculations, I start with filters and separators filled to the desired ending cylinder pressure, but keeping the compressor running. Only then opening the valve to let air flow to cylinders as I simultaneously start my timer. Time then runs from full separators and filter towers to full everything, giving closer approximation of your fill rate.
There may be other factors that I have failed to consider, and welcome some input on varying voltages and atmospheric density, etc. from day to day, and the potential effect on how discharge volumes may vary.... but probably not very much. (Also how many adult beverages have been consumed prior to operation of the equipment and timer)