Calibrating Pressure Pot Fluid and Air Settings

Advice for a beginner on dialing in air and fluid pressures for a new pressure pot setup. July 25, 2010

Question
Any advice for someone new to working with pressure pots? Never used them before and I just got my hands on two used ones - one for dyes and stains, the other for clears. I'm having trouble getting good output from the 2.5ga pot for the clears; I'm struggling with the settings trying to get rid of little pinholes as I spray. What do you guys do for your setup and adjustment procedure?

Forum Responses
(Finishing Forum)
From contributor A:
You need to reduce your product or turn up the pot pressure until the stream (fluid only, no air) looks like a "beer piss." The pressure should be between 10-20 psi for typical products and 20-30psi for things like primer/undercoater or house paint.

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From contributor J:
Exact settings will vary depending on the gun, tip size and fluid viscosity. Try this: Fluid pressure 8-10 lbs. Air pressure 30-50 lbs. Consider these ballpark starting point settings.

Once you get about an 8 stream with fluid only, slowly turn up the air until you get good atomization. More air than necessary will produce excessive overspray; too little and it will orange peel. Note your settings at the point you are happy with the results.

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From contributor A:
The method I was taught for reducing products has always worked well. Take a paint stick and after a stir, hold the wet stick at a 45 degree angle. It will start dripping. It is a decent viscosity if it stops in less than 20 drips. House paint is tough because you can only reduce it so far before you screw up the chemistry or design of the finish.

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From the original questioner:
I'm using 25' of hose. Do I need to slowly lift the gun and the hose above the pot with the trigger open to drain the material back or does the pressure release do most of that? I don't spray everyday - how long can you leave nitro lacquer and pre-cat before you need to mix or clean?

I've never seen anyone go through the motions of setup/cleanup/maintenance with a setup like this so I'm trying to figure it out as I go. Thanks.

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From contributor D:
Here's a way to precisely measure flow rate. Get a plastic beaker or container graduated by ounces, and a stopwatch. Start off with a fluid pressure setting of 8 lbs. Turn atomizing air pressure off or to zero. Pull the gun trigger and stopwatch simultaneously - let the material flow into the graduated container. Stop at 30 seconds. Whatever the amount of material in your container X 2 is your material flow rate per minute measured in ounces at that particular fluid air setting.

The optimum material flow rate is going to vary depending on the material and your equipment. The only answer is to work the variables until you find the flow rate that works best. Once you find it, measure it, and then you have a precise benchmark for that material.

The problem of relying on your gauge to set your fluid pressure is the regulators most finishers are using on pressure pots are not sensitive enough to regulate in such small increments.