ASTM D6504-00
(Practice)Standard Practice for On-Line Determination of Cation Conductivity in High Purity Water
Standard Practice for On-Line Determination of Cation Conductivity in High Purity Water
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.
1.4 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.
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Please
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Designation:D6504–00
Standard Practice for
On-Line Determination of Cation Conductivity in High Purity
Water
This standard is issued under the fixed designation D 6504; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope tivity of a Flowing High Purity Water Sample
D 5540 Practice for Flow Control and Temperature Control
1.1 This practice describes continuous sample conditioning
for On-Line Water Sampling and Analysis
by hydrogen ion exchange and measurement by electrolytic
conductivity. It is commonly known as cation conductivity
3. Terminology
measurement in the power industry although it is actually an
3.1 Definitions— For definitions of terms used in this
indicationofanioncontaminationinhighpuritywatersamples.
practice, refer to Test Methods D 1125, Terminology D 1129,
Measurements are typically in a range less than 1 µS/cm.
and Practice D 3864.
1.2 The actual conductivity measurements are made using
3.2 Definitions of Terms Specific to This Standard:
Test Method D 5391.
3.2.1 cation conductivity, n—the parameter obtained by
1.3 This practice does not provide for separate determina-
conditioning a sample by passing it through a hydrogen form
tion of dissolved carbon dioxide. Refer to Test Methods
cation ion exchange resin column and then measuring its
D 2186 and D 4519.
electrolytic conductivity, on-line.
1.4 This standard does not purport to address all of the
3.2.2 specific conductivity, n—direct electrolytic conductiv-
safety concerns, if any, associated with its use. It is the
ity measurement of a power plant sample, usually dominated
responsibility of the user of this standard to establish appro-
by treatment chemicals, such as ammonia or amines.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
4. Summary of Practice
2. Referenced Documents 4.1 The sample is passed continuously through a small
2 cation exchange column in the hydrogen form, which ex-
2.1 ASTM Standards:
+
changes all cations for H . In this process, pH adjusting
D 1066 Practice for Sampling Steam
treatment chemicals, such as ammonia and amines are re-
D 1125 Test Methods for Electrical Conductivity and Re-
moved.
sistivity of Water
4.2 Measurement is made continuously on the conditioned
D 1129 Terminology Relating to Water
sample with a process high purity conductivity analyzer/
D 1193 Specification for Reagent Water
transmitter.
D 2186 Test Methods for Deposit-Forming Impurities in
4.3 Temperature conditioning of the sample and specialized
Steam
compensation of the measurement are used to minimize
D 3370 PracticesforSamplingWaterfromClosedConduits
temperature effects on the performance of the ion exchange
D 3864 Guide for Continual On-Line Monitoring Systems
resin and the measurement.
for Water Analysis
4.4 Few studies have been published on the performance of
D 4519 Test Method for On-Line Determination of Anions
cation conductivity measurement but one collaborative effort
and Carbon Dioxide in High Purity Water by Cation
provides some background (1).
Exchange and Degassed Cation Conductivity
D 5391 Test Method for Electrical Conductivity and Resis-
5. Significance and Use
5.1 Cation conductivity provides one of the most sensitive
and dependable on-line means of detecting anionic contamina-
This practice is under the jurisdiction ofASTM Committee D-19 on Water and
tion in the boiler/steam cycle, such as chlorides, sulfates,
is the direct responsibility of Subcommittee D19.03 on Sampling Water and
Water-Formed Deposits, Analysis of Water for Power Generation and Process Use, nitrates, bicarbonates, and organic acids, such as formic and
On-Line Water Analysis, and Surveillance of Water.
acetic.
Current edition approved June 10, 2000. Published September 2000.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on The boldface numbers given in parentheses refer to a list of references at the
the ASTM website. end of this standard.
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Please
contact ASTM International (www.astm.org) for the latest information.
D6504–00
5.2 High sensitivity is provided by intentionally eliminating 6.8 Some cation resins contain leachables which can raise
the pH adjusting treatment chemical(s), for example, ammonia background conductivity and reduce sensitivity to sample
and amines, from the sample and converting remaining salt impurities. Extensive rinsing usually is required.Acontinuous
contaminants into their acid forms which are approximately rinsing scheme is given in Appendix X1.2. Some success also
three times as conductive. has been achieved with a hydrochloric acid (1+4) pre-rinse.
5.3 Guidelines on cation conductivity limits for various 6.9 For interferences with basic high purity conductivity
cycle chemistry and boiler types have been established by measurements, refer to Test Method D 5391.
EPRI (2-4) and by ASME (5,6).
5.4 The sample effluent from the cation exchange column
7. Apparatus
also may be used, and in some cases is preferred, for ion
7.1 Cation Exchange Column:
chromatography or other anion measurements.
7.1.1 The cation exchange column shall have an inside
diameter of less than 60 mm (2.4 in.) and produce a flow
6. Interferences
velocity greater than 300 mm/min (1 ft/min) at the sample flow
6.1 Some weakly ionized cations may not be completely
rate (seeAppendix X1). The column shall have end screens to
exchanged by the resin. This will produce positive or negative
distribute flow across the cross-section of the column and to
errors in the measurement depending on the sample composi-
prevent resin beads and fines from escaping. The column may
tion. These errors can reduce sensitivity to corrosive contami-
be piped for upward or downward flow. Upward flow provides
nants.
automatic purging of air at startup which is helpful in cycling
6.2 Temperature effects on the cation resin may alter its
plants. However, the resin must be packed full to prevent
equilibrium properties. Control sample temperature within the
fluidizing and channeling. Downward flow eliminates the
resin manufacturers’ temperature limits to obtain consistent
possibility of fluidizing but requires the means to vent air from
results.
the column at startup. Care must be exercised to eliminate all
6.3 Thelargetemperatureeffectsofhighpurityconductivity
air pockets which could cause channeling. The column should
measurement must be minimized by sample conditioning and
be constructed of nonleaching material, such as polycarbonate
temperature compensation. Although sample temperature may
or polypropylene. Materials, such as polyvinylchloride, may
be controlled closely, it may be significantly influenced by the
leachchloridesandarenotrecommended.Flexibletubingused
ambient temperature as it passes through the column, tubing
tomakeconnectionstothecolumnshouldhaveminimallength
and flow chamber. The temperature coefficient of pure water is
and diameter to minimize the amount of leaching and air
near 5 % of measurement per °C at 25°C, which can contribute
(carbon dioxide) permeation.
substantial errors if not compensated properly. Temperature
7.1.2 The resin shall be a sulfonated styrene-divinylbenzene
compensation must be appropriate for the unique acidic com-
withatleast8 %cross-linkage,strongacidgelcationexchange
position of cation conductivity samples. Conventional high
resin in the hydrogen form, filling the column. An indicating
purity temperature compensation for neutral mineral contami-
resin which changes color as its hydrogen ions are displaced is
nants is not suitable for this application (7,8). The user is
strongly preferred for convenient monitoring of the progress of
cautioned that the accuracy of algorithms for cation conduc-
resin exhaustion through the column.
tivity compensation may vary widely. The user should deter-
7.1.3 The resin must be rinsed to remove leachables before
mine the applicability and accuracy of the instrument’s tem-
full sensitivity can be reached. A convenient arrangement of
perature compensation in the anticipated temperature range.
multiple resin columns to provide the rinse and for easy
6.4 Carbon dioxide may be in a sample and will be
change-out is described in X1.2.
converted to carbonic acid and raise cation conductivity. This
7.2 Process Sensor—The conductivity cell shall be suitable
is not strictly an interference; however, carbon dioxide gener-
for measurement of high purity water and sh
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