More Compressed Air Treatment

This is page two of information about how plumbing can improve the quality of the compressed air supply to your shop, factory, or workshop. Page one is here.

We've touched on the use of additional receivers to help in the natural cooling and de-watering of your compressed air, let us now give some consideration to the overall plumbing in your plant and how following some fundamental rules will help in your compressed air treatment.

Overall Plumbing

We know that compressed air cools as it travels, and as it cools it often reaches the dew point, where water vapor condenses into free water in your air lines.

And we all know that gravity works, right?


Why not plumb your plant so that gravity works for you?

When water condenses in your compressed air lines, (it is inevitable that it will) it can be removed from your air lines through sensible plumbing, rather than flowing into your end applications and causing all sorts of problems. Get the water out before it gets to your air tools, your air valves and your cylinder / actuators, and there's no more problem.

We recommended earlier that as the air exits the receiver, it should flow through an appropriately sized air filter straight up to the ceiling in the plant. Instead of having an elbow from the horizontal line from the receiver to direct the piping upwards, consider installing a 'T'.

Install the 'T' so that the two in-line ports in the 'T' fitting are vertical. Plumb your air line from the top port up to the ceiling, and plumb a line from the bottom port to either an electric or float type auto drain.

Plumbed this way, as the compressed air climbs up to the ceiling in the plant, it will start to cool, and, as it does, water will condense. The water will flow back down - gravity works :- ) - to a 'catchment' at the bottom of the vertical line. And you guessed it, at the bottom of that drop leg should be a float type or electronic auto-drain.

Compressed Air Drop Leg Drain

When the main air line that runs all around your plant at the ceiling is installed, ensure that all lines have a gentle slope to one end of the plant. As air flows around the plant it will cool further and free water will form. This will happen unless the ambient temperature at the ceiling is higher than the dew point of the compressed air in the mains. Having the entire ceiling line on a gentle slope to one location will allow all the water that condenses there to travel to one location, and drop down one drop leg to an automatic or float type drop leg drain at the floor level.

But what about all the other drop lines? Won't the free water in the mains run down all of them?

Not if you take your drop lines off the top of the air mains as shown in the next graphic. Rather than any free water that collects running down the drop leg to the application, water that collects in the mains will only run to the one location at the lowest point in your plant that you want it to, then down that drop leg to be drained regularly by your auto-drain or drop-leg float drain at the bottom.

Compressed Air Drop Leg Drains

Yes, it is extra work and cost to plumb your drop lines as shown in the drawing.

The upside is a reduction in ongoing maintenance at the application and a reduction in machine down-time to perform that maintenance. Over the longer haul, plumbing properly will save money.

Remember that the main air lines at your plant ceiling, if at all possible, should be in a ring, so that any particular drop line can pull air from two directions, hopefully avoiding air starvation at that application.

Each step of your air preparation that we've covered so far has been towards systematically removing free water from your air lines that's there through a natural cooling process. The air in your receiver and air mains has been reaching it's dew point, and more and more of the air vapour in your compressed air has been condensed into free water which can be removed as noted.

Here's more information about removing water with aftercoolers and refrigerant dryers.