Clean, Dry Air... How? Drains, Traps and filters

If you read my previous article then you know by now that moisture is simply an unavoidable by product of compressing air for shop use, and depending on what part of the country and the time of year, some will tend to have more water than others. This will consist of a mixture of water, oil and rust and depending on the age of your compressor and the humidity in your area you’ll have more or less of one of those substances.

So how do we control these and stop them from ruining our tools and contaminating paint jobs, well let’s start at the main source the compressor. Somewhere on the bottom of every receiver tank is a manual valve which is placed there so you can occasionally drain the tank of the water build up. Not all, but in most shops we unfortunately do not have remembering to drain the compressor as a number one priority on the to do list. Well the good news is there are options to remedy this.

Here is one of those rare scenarios where spending more money might not be the better way, let me explain. You can install an electric timed drain valve system that will open at certain intervals and drain the tank. Down side is you have to supply power to it and it’s on a timer that has no correlation to compressor use. That equates to the compressor being drained whether you’re using it or not and that equates to unnecessary dollars spent. A less expensive alternative is a float and valve system which basically opens only when there’s water at the bottom of the tank.

Moving on away from the compressor to our traps, but before I do here’s a quick tip "compressors vibrate a lot!" and because of this always remember to use a flexible connection from the compressor to the lines or over time you will have a line failure due to vibration. See example below.  

Traps, a simple trick to eliminate a lot of the water in your lines and all it takes is a little plumbing skill. Whatever extra cost of piping and time it takes will pay for itself many times over in longer tool life and desiccant filter replacements.

Below you’ll see a drawing (Sharpe spray equipment) put out in the market decades ago that does a pretty good job of explaining traps. There are 5 key points I want to address here, first unless you’re going all out and buying a refrigerated air dryer then do not place any outlet or air filter anywhere near the compressor outlet. The reason for this is that you still have warm air coming directly out of the compressor receiver and you need to give the air some distance to cool or any filter you install nearby will be ineffective.

Next, notice they are suggesting a slight sloop in the main line, you don’t want any water hanging out up there vacationing, you need those lines to naturally drain and stay dry. Following the main line you’ll find that the first outlet faces up not down, let gravity do it’s job and keep the water on the pipe and not filtering down your outlet pipe. All this takes is two extra elbows to accomplish. Following that same first outlet downward notice that the filters are not installed directly under the pipe, there has been tees installed along the down pipe, it’s a lot harder for water to go sideways then downward, again gravity working for you.

Lastly, if you want the best driest air for your paint spraying lines then install your expensive desiccant filters the farthest from your compressor this will give you a better chance at having the driest air and getting longer life out of your desiccant filters.

The only other thing I would add to this configuration would be to close these lines in a closed loop system so you have a balanced airflow and you don’t lose significant pressure if a worker starts using a high cfm tool along the line while you're in the middle of a paint job.