Significance and Use
Cation conductivity provides one of the most sensitive and dependable on-line means of detecting anionic contamination in the boiler/steam cycle, such as chlorides, sulfates, nitrates, bicarbonates, and organic acids, such as formic and acetic.
High sensitivity is provided by intentionally eliminating the pH adjusting treatment chemical(s), for example, ammonia and amines, from the sample and converting remaining salt contaminants into their acid forms which are approximately three times as conductive.
Guidelines on cation conductivity limits for various cycle chemistry and boiler types have been established by EPRI (2-4) and by ASME (5,6).
The sample effluent from the cation exchange column also may be used, and in some cases is preferred, for ion chromatography or other anion measurements.
1. Scope
1.1 This practice describes continuous sample conditioning by hydrogen ion exchange and measurement by electrolytic conductivity. It is commonly known as cation conductivity measurement in the power industry although it is actually an indication of anion contamination in high purity water samples. Measurements are typically in a range less than 1 S/cm.
1.2 The actual conductivity measurements are made using Test Method D 5391.
1.3 This practice does not provide for separate determination of dissolved carbon dioxide. Refer to Test Methods D 2186 and D 4519.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
2. Referenced Documents
D1066 Practice for Sampling Steam
D1125 Test Methods for Electrical Conductivity and Resistivity of Water
D1129 Terminology Relating to Water
D1193 Specification for Reagent Water
D2186 Test Methods for Deposit-Forming Impurities in Steam
D3370 Practices for Sampling Water from Closed Conduits
D3864 Guide for Continual On-Line Monitoring Systems for Water Analysis
D4519 Test Method for On-Line Determination of Anions and Carbon Dioxide in High Purity Water by Cation Exchange and Degassed Cation Conductivity
D5391 Test Method for Electrical Conductivity and Resistivity of a Flowing High Purity Water Sample
D5540 Practice for Flow Control and Temperature Control for On-Line Water Sampling and Analysis
Index Terms
boiler cycle chemistry; cation conductivity; on-line; process measurement; ICS Number Code 13.060.60
Citing ASTM Standards
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