2010 Volume 59 Issue 11 Pages 436-439
In the repair construction work etc. of the buildings the wet fire piping and the wet sprinkler piping are cut by fusion or grinding. In that case, the ignition phenomena at the cutting part are often reported. It is pointed out that the hydrogen generated in piping is the cause of the ignition. To verify these phenomena, we have done two reproduction experiments. In one case, after tap water had been filled to the galvanic couple piping where the galvanized steel pipe was connected with the stainless flexible tube joint , it was sealed up. In the other case, after tap water had been filled to the reactive container where the galvanic couple of stainless steel plate/zinc plate was immersed, it was sealed up. Each device was left sitting for a long duration at the room temperature. The confirmation of gas generation, the componential analysis of the generated gas, the measurement of galvanic current and the pressure change in the reactive container, and the analysis of the water after test were carried out. Those results were theoretically discussed. It is suggested that hydrogen can be generated in the fresh water (tap water) without oxygen by the electrochemical reaction (corrosion reaction) composed of the reduction reaction of hydrogen ion (cathodic reaction) and the oxidation reaction of zinc (anodic reaction).