Study the physics, do the math, and a 40-gallon compressed air tank pressurized to 100 psi has the explosive power of a stick of dynamite. Depending on circumstances, that’s enough to blow all four walls out of a two-car garage. There are hundreds of documented cases where buildings were destroyed and people were maimed or killed when compressed air tanks exploded.
Air compressors heat atmospheric air as it is compressed. Moisture/humidity in the heated air condenses when it contacts the relatively cooler walls of the air storage tank, and collects at the lowest point in the tank.
Left alone, that condensed water corrodes and thins the wall of the tank. When the wall thins enough for the compressed air to rupture a pinhole, it can create an instantaneous chain reaction failure of the container wall that results in an explosion. That’s why air compressor tanks have drain petcocks on their bottoms—to regularly drain condensed water to prevent corrosion from thinning the tank’s walls.
According to air tank manufacturers, “regularly” means daily. At large factories that use high volumes of compressed air on assembly lines, draining air systems is part of daily procedures of maintenance workers.
Many “experts” on internet forums pooh-pooh concerns about compressed air tanks exploding. They relate tales of innocuous hissing pin holes in the air tank they inherited from their grandpa, that they patched with a sheet metal screw and rubber washer, or welded a patch over.
Maybe so. But there are just as many tales of apparently “solid” air tanks, or patched tanks, exploding without warning, destroying a workshop and killing people.
In short, when it comes to compressed air storage tanks: regularly drain moisture. NEVER patch a leaky tank with a sheet metal screw. Any welding on an air tank should be done only by a certified welder. Someone’s life could hang in the balance.
