air tank vs air compressor. help pls.....

I don't know. If it were me I would not feel safe pressurizing a tank rated for 40-50 psi to twice that rated pressure. It might hold it, it might not. I would not want to be in the vicinity if it decided not to.

I would second MusicCity's opinion but in stronger terms. Since you don't have actual knowledge that your copmressor's tank is rated for 80-100 PSI, you really should stick with what the compressor was orignally putting out. It is true, that your tank, even if rated to only 50 PSI, is probably over designed, but why take the chance?

roni1112: Are you saying that you want to hook up an air tank to an existing compressor that doesn't already have one? If that's the case, it's no problem. You need a pressure gauge on the compressor (you likely already have one - if not you must add one.) You will also need a second one on the tank you add, plus an indicator of what the presssure in the tank is. Simply connect the output from your compressor to the inlet on the tank. Connect your airbrush hose to the outlet on the tank and Voila! You have created your own source of air to use. Lots of modellers have a setup like that.
Just turn on your compressor, crank it up to max. PSI and watch the indicator on the tank. When it gets to 50-55 PSI, shut the compressor off.
Set the second regulator for 15 PSI, or whatever you want to spray at and away you go. Non-pulsating air that will likely last your whole session.

Rich