Percent Dissociation

Percent dissociation (%DA) is derived from the amount of hydrogen in the sample gas. Gas nitriding uses ammonia (NH3) gas as its source of nitrogen. When NH3 is dissociated, nitrogen and hydrogen gas are produced. The accurate calculation of %DA requires the flow rates of other gases that are being introduced into the process. These flow rates are measured in cfh (cubic feet per hour). Percent dissociation can only be calculated by entering the flow of nitrogen (N2), ammonia (NH3) and Dissociated Ammonia (DA). These values are entered at the bottom of the main screen when %DA is selected. If no gas flow values are entered (each flow shows 0 scfh), the system will assume 100% NH3 is flowing into the furnace. As soon as any of the gas values are changed to a value that is not 0, the calculations are based on those gas flows.