Issues with water tables:
In my shop in NH....which is a hobby shop and is not heated when I am not in it....the water will easily freeze in winter. my shop temperature has been as low as -10 F! I suppose you could put a rather large stock tanke heater (as used for cattle feeders in cold climates)....although that would likely consume a fair amount of power to keep the water above freezing.
Other issues...if the plate being cut is in contact with the water (which provides the best of fume control) the cut edge will have a higher propensity for dross.....as the molten metal resolidifies more quickly. Further....plasma cut edges that have water in contact with them during the cut will have a rougher edge finish due to the breakdown of water into oxygen and hydrogen (disassociation and electrolysis processes from the heat and the electrical action)....the hydrogen creates small explosions (you can actually hear little popping sounds from plasma when cutting in water) and these pops actually push the arc a bit, creating striations or pronounced lag lines in the cut face.
Also be aware....most entry level air plasma systems are not recomended for submerged cutting...although they will work. Modern air plasma torches use moving parts inside the torch to create a short circuit spark for starting the ionization process....over time, dirty water from a water table can cause the moving parts to stick and or short...which will cause damage to the torch head. Industrial high frequency start torches are better suited to water table applications as they use a gas preflow that blows any water out of the torch before firing...and they do not have moving parts.
The good things about water tables:
- best way to minimize fumes without wasting building heat (by blowing fumes outside)
-submerged cutting on stainless...using nitrogen...will provide an oxide-free cut face as ambient air is not present.
-Water table sludge is relatively easy to clean out as compared to dry tables...can be shoveled or scooped...as opposed to chipped.
Jim Colt Hypertherm  |