Originally Posted by
jimcolt
This is a "canned" response from my files.....as questions pertaining to cutting aluminum with plasma over a water table are asked quite frequently"
Jim
In regards to cutting aluminum over a water table, there generally is no concern of the possibility of hydrogen production and the ensuing explosion hazard. Aluminum cutting produces a by product of aluminum oxide, which sinks in the water and absorbs oxygen. When oxygen is removed from water (H20) it leaves hydrogen, which you will see rising to the surface (after cutting aluminum) as small bubbles.
Since the quantity is very small, and hydrogen is lighter than air, the small amount of hydrogen will dissipate in the ambient air.
Many water tables have a submerged chamber that is used (with compressed air) to rapidly raise and lower the water level in the table for small parts removal, cleaning, etc. If aluminum oxide is allowed to get into a closed chamber, hydrogen could be trapped and over time could form a large pocket, and with the event of a spark and some oxygen there could be an explosion.
Most of the stories about aluminum and water tables causing explosions have no basis, although there have been a couple of issues over the 32 years I have been working for Hypertherm that involved minor explosions on large industrial machines. The ones that I am aware of were solved with aerators (no pump needed) that simply involved a couple of pipes with holes drilled in them in them...submerged in the water table. Low pressure compressed air was fed into the pipes to aerate the water, diluting the hydrogen.
Cut all the aluminum you want on small water tables!
Jim Colt Hypertherm