The determination of sodium in low concentrations in the water-steam cycle is of great importance in power plants. On the one hand, this is due to the fact that the signifi cance of sodium in corrosion processes has become more and more recognized over the last few years. On the other hand, this measurement procedure enables a fast monitoring of a leakage for instance in the condenser or the aperture in a cation fi lter or a mixed bed fi lter. Not least for that reason, the sodium measurement has become increasingly important with revising the VGB-guidelines (S-006 / S-010).

The Digox 602 sodium is an analyser for the continuous measurement of dissolved sodium, even at the level of trace elements, and ideally suited for the operation in the water-steam cycle of power plants, for the control of full demineralisation units, desalination of sea water as well as in the semiconductor industry and electronics industry. In order to enable a measurement without the infl uence of hydronium ions, the sample is conditioned to a value of pH 11 +/- 0.02 pH. The measurement is potentiometrically carried out by means of a special measuring sequence with an Na-sensitive electrode in combination with an Ag/AgCl-reference electrode:

Ag/AgCl(S) – buffer – Na+-sensitive glass membrane - alkalised measuring solution - diaphragm - KCl-electrolyte gel - AgCl(S)/Ag.

Technical features:

•Very low consumption of conditioning materials: a maximum of 0.5 l DIPA/month at pH 7
•Automatic three-point calibration, adjustable time interval
•Individually selectable sequence and measuring duration in the multi-channel device
•Control and monitoring of the adjustable pH value
•Usable in the range (unbuffered) of pH 4-11
•Automatic temperature compensation
•Galvanically separated signal outputs
•Pressure regulator and easy-to-clean prefilter per channel
•Built-in sequencer for up to 6 sample channels
•Additional connection for the measurement of a laboratory sample