Reasons for increased Conductivity in Pure Steam

The quality of pure steam is assessed based on its condensate, which must meet the requirements for Water for Injection (WFI). Since pure steam is generated via phase transition, it is generally of very high purity. However, elevated values for conductivity or TOC (Total Organic Carbon) may occasionally be observed. Several factors may be responsible:

1. Technical Defects

• Defective heat exchanger: A failure in the heat exchanger of the pure steam generator may allow heating steam to leak into the pure side.
• Leak in the sample cooler: A crack or leak may lead to cooling water entering the condensate.
• Countermeasure: Eliminate the technical defect.

2. Chemical Influences from Feed Water

• Volatile organic substances (e.g. humic acids) present in the feed water may decompose at high temperatures, forming low-molecular, conductive compounds.
• Countermeasure: Optimize feed water treatment or apply thermal degassing of the feed water.

3. Vacuum Formation in the System

• If the system is shut down, for example over the weekend, a vacuum may form. In this case, gaseous or liquid contaminants can be drawn into the system via condensate or drain lines. Upon restart, it may take days or even weeks to fully flush out residues that have adhered to internal surfaces.
• Solution: Prevent vacuum formation-for example, by actively ventilating the cooling system with filtered, oil-free compressed air.

4. Influence of the Test Method

When conductivity and TOC are measured online, at-line, and in the laboratory, significant differences in results are to be expected. The values can vary substantially depending on the measurement setup. For example:

• Online: 0.2 µS/cm
• At-line: approx. 0.4 µS/cm
• Laboratory: up to 0.8 µS/cm

Reason: Exposure to air during sampling allows CO? uptake, which leads to the formation of carbonic acid and hydrogen carbonates, both of which are conductive.