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Pros and Cons of Moisture Traps

Blast Pot Moisture: Your Last Line Of Defense

 

We all know moist air mixing with your abrasive is a production killer.  To avoid this, it’s common throughout the industry to attach a Moisture Trap to the inlet of your blast pot.

Let’s first emphasize that no moisture separator ever replaces or is a substitute for an Air Dryer. Air Dryers are the most effective means of removing moisture. Period.  But even an air dryer can’t protect you in the following common scenario. Let’s say you’re running 30m/100ft of hose from the air dryer to the pot.  When you shut things off at the end of the day, the air trapped inside that hose will cool overnight, regain moisture, and then infect your pot when you start up again the next day.  Placing a moisture separator between the air dryer and the pot, helps correct for this problem.  A moisture separator is the very last line of defense before your abrasive is compromised – and we highly recommend using one.

No problem, you say – I’ve got one. Well there is a problem if that moisture trap uses a filter. These items do eliminate moisture – but at an asymmetrical cost to your productivity.

Typically, these traps have a 5-micron fine filter which results in an insane pressure loss. How insane? Generally 1 bar or 14 psi pressure drop to the airflow. Remember, as a rule of thumb, for each 1psi drop below 100psi, you’ll lose 1.5% of your productivity.  So reducing your pressure 14psi – from 100psi to 86psi results in a 20% decrease in productivity. Basically you are losing one day of potential productivity for every 5 days of 14psi loss. You’d probably fare better not using this trap and simply deal with the moist abrasive.  These inlet filters are great for smaller mechanical hand-tool scenarios but are devastating to industrial sandblasting. Additionally, these filters typically get clogged with high volumes of not-so-clean air – which reduces pressure even further.

So what style of moisture separator should we use?  We recommend, two options.

  1. A centrifugal moisture separator mounted at the inlet.  Instead of using a filter to remove moisture, these traps cause the incoming air to cyclone about, impinging against the inner steel and forcing the heavier moisture to attach to the inner walls and drain through a lower valve.  There is minimal to no pressure loss in this process.
  2. Option 2 is a stand-alone moisture separator that uses air expansion as well as a stainless steel coalescent element. The expanding air “shakes” out the moisture while maintaining the valuable pressure while the steel element provides surface tension, further coalescing moisture from the air.

Both systems pay for themselves in productivity in as little as one week.