Understanding Pump Ratings for Air-Assisted Airless Equipment
The ratio is simply the multiplier to find the fluid pressure at a given air pressure. For example if you have a 14:1 pump, and feed it with 40psi of air, you will have 14*40=560psi of fluid pressure.
If you look on the TDS of many of the products you spray, they will recommend a fluid pressure when spraying the product with an AAA.
From the original questioner:
Thanks for clearing that up. So when you buy a pump like that, the fluid psi is dictated by how you set the air pressure. How do you know witch ratio pump you need? At this time I don't do a whole lot of spraying. Maybe if I get more jobs I will look into it.
From contributor J:
For the typical fluids we cabinetmakers spray, a 10 or 14:1 is fine. You need larger pumps if you plan on spraying extremely thick materials, or want to run more than 1 gun at a time off a single pump.
Refer to the TDS of the materials you plan to spray. Most will recommend a fluid pressure of around 600psi give or take. So with a 10:1, you feed the pump with 60psi of air, and a 14:1 you feed the pump with ~40psi. Most air tools have a max pressure rating of around 100psi, meaning that you can get a max fluid pressure of 1000psi from a 10:1 and 1400psi from a 14:1.
Any of the typical units from Binks, Kremlin, CAT, Graco, will all be suitable. I would base your decision more on the availability of parts and support from your dealer than the actual brand. They are all capable of laying down a quality finish. The Kremlin is by far the most popular. I use a CAT bobcat, and have nothing but great things to say about it.
From contributor N:
The third thing to look at (as well as ratio and availability of parts) is volume - how much material the unit can pump. If you'll just running one gun, .3 to .5 gpm is more than adequate and will use a lot less solvent when cleaning up.
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