I've tried several different setups (an understatement) for drying out my air. I do quite a bit of DA sanding and painting from my garage at home and have always battled moisture and oil problems.
The tank is an old propane tank. Black iron couplings were cut in half and used as weld-in bungs. Tank was back-purged with argon and mig welded with my little miller 140.
1.25" bungs on top and bottom for easy empty and refill.
takes almost three large bags of fresh step crystals cat litter (95% Silica gel) -- much cheaper than buying bulk silica
Sink drain Screen brazed to inside of exit nipple to keep the desiccant in the tank and out of my regulator.
I have ZERO moisture for about a month of continuous use and gained a little more volume (which helps my 60 gal IR keep up!)
Feel free to comment, copy, whatever.