Desiccant Air Drying Systems
Though desiccant drying systems are more often used in professional production shops, they are also lifesavers for hardcore hobbyists or those with severe moisture problems. Here, we'll try and explain a bit about these systems on the off chance you might like to equip your home shop with one.
As we've said earlier, when air is compressed and its temperature increases, so does its capacity to hold moisture. As the hot, moist air travels through the air lines, it cools, allowing the moisture to condense. Filters, drain traps, and drain legs are effective for removing liquid. But for removing residual water vapor and aerosols, you'll need a desiccant drying system.
Some desiccant dryers use silica gel beads to absorb moisture. As the wet compressed air flows through the inlet of the dryer and down into the bed of desiccant, the silica gel beads soak up nearly every bit of humidity or moisture in the air. In fact, the air humidity can be reduced to a 40-degree dew point with the use of silica gel.
After the moisture has been removed, the dry air passes through a sintered bronze filter and out the outlet port. As long as the desiccant is replaced when it reaches its saturation point, the unit will continue to supply you with clean, dry, moisture-free air. As the desiccant becomes saturated with moisture, the dew point begins to rise. This is usually evident when the silica gel desiccant begins to change color. It's at this time that the desiccant will need to be changed. Some types of desiccants are designed to be regenerated by baking it in an oven to dry it out, though most are designed to be discarded and replaced.
Another type of desiccant material is called Activated Alumina, and it's a byproduct of the manufacture of aluminum. This product is used for the removal of water vapor, and can lower the dew point to 100 degrees below zero. It has a high crush-strength and is a low dusting material. The capacity of this material to hold water is slightly lower than silica gel, but it can be regenerated by baking and has been determined to work well in paint shops.
Hopefully, this information will help you to design and fabricate an air supply system for your home shop that'll rival that of a professional production shop. Just keep in mind, whether you plan on doing any type of auto body refinishing or not, a clean, dry supply of compressed air will add years to the life of any sort of air-operated equipment.
Well, that's about all I can't in this installment, so it looks like I'll have to continue in the next issue. I really hope this information is useful for ya. And again, please keep in mind that the most important aspects of this attempt at information sharing is that all of us can really accomplish a heck of a lot more than we give ourselves credit.