1、Designation: D6504 11 (Reapproved 2016)1Standard Practice forOn-Line Determination of Cation Conductivity in High PurityWater1This standard is issued under the fixed designation D6504; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision
2、, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTEEditorial corrections were made throughout in February 2016.1. Scope1.1 This practice describes continuous samp
3、le conditioningby hydrogen ion exchange and measurement by electrolyticconductivity. It is commonly known as cation conductivitymeasurement in the power industry although it is actually anindication of anion contamination in high purity water samples.Measurements are typically in a range less than 1
4、 S/cm.1.2 The actual conductivity measurements are made usingTest Method D5391.1.3 This practice does not provide for separate determina-tion of dissolved carbon dioxide. Refer to Test Method D4519.1.4 The values stated in SI units are to be regarded asstandard. The values given in parentheses are m
5、athematicalconversions to inch-pound units that are provided for informa-tion only and are not considered standard.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate
6、safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1066 Practice for Sampling SteamD1125 Test Methods for Electrical Conductivity and Resis-tivity of WaterD1129 Terminology Relating to WaterD1193 Specificati
7、on for Reagent WaterD3370 Practices for Sampling Water from Closed ConduitsD3864 Guide for On-Line Monitoring Systems for WaterAnalysisD4519 Test Method for On-Line Determination of Anionsand Carbon Dioxide in High Purity Water by CationExchange and Degassed Cation ConductivityD5391 Test Method for
8、Electrical Conductivity and Resis-tivity of a Flowing High Purity Water SampleD5540 Practice for Flow Control and Temperature Controlfor On-Line Water Sampling and Analysis3. Terminology3.1 DefinitionsFor definitions of terms used in thispractice, refer to Test Methods D1125, Terminology D1129,and G
9、uide D3864.3.2 Definitions of Terms Specific to This Standard:3.2.1 cation conductivity, nthe parameter obtained byconditioning a sample by passing it through a hydrogen formcation ion exchange resin column and then measuring itselectrolytic conductivity, on-line.3.2.2 specific conductivity, ndirect
10、 electrolytic conductiv-ity measurement of a power plant sample, usually dominatedby treatment chemicals, such as ammonia or amines.4. Summary of Practice4.1 The sample is passed continuously through a smallcation exchange column in the hydrogen form, which ex-changes all cations for H+. In this pro
11、cess, pH adjustingtreatment chemicals, such as ammonia and amines are re-moved.4.2 Measurement is made continuously on the conditionedsample with a process high purity conductivity analyzer/transmitter.4.3 Temperature conditioning of the sample and specializedcompensation of the measurement are used
12、 to minimizetemperature effects on the performance of the ion exchangeresin and the measurement.1This practice is under the jurisdiction of ASTM Committee D19 on Water andis the direct responsibility of Subcommittee D19.03 on Sampling Water andWater-Formed Deposits, Analysis of Water for Power Gener
13、ation and Process Use,On-Line Water Analysis, and Surveillance of Water.Current edition approved Feb. 15, 2016. Published March 2016. Originallyapproved in 1999. Last previous edition approved in 2011 as D6504 11. DOI:10.1520/D6504-11R16E01.2For referenced ASTM standards, visit the ASTM website, www
14、.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14.4 Fe
15、w studies have been published on the performance ofcation conductivity measurement but one collaborative effortprovides some background (1).35. Significance and Use5.1 Cation conductivity provides one of the most sensitiveand dependable on-line means of detecting anionic contamina-tion in the boiler
16、/steam cycle, such as chlorides, sulfates,nitrates, bicarbonates, and organic acids, such as formic andacetic.5.2 High sensitivity is provided by intentionally eliminatingthe pH adjusting treatment chemical(s), for example, ammoniaand amines, from the sample and converting remaining saltcontaminants
17、 into their acid forms which are approximatelythree times as conductive.5.3 Guidelines on cation conductivity limits for variouscycle chemistry and boiler types have been established byEPRI (2-4) and by ASME (5 and 6).5.4 The sample effluent from the cation exchange columnalso may be used, and in so
18、me cases is preferred, for ionchromatography or other anion measurements.6. Interferences6.1 Some weakly ionized cations may not be completelyexchanged by the resin. This will produce positive or negativeerrors in the measurement depending on the sample composi-tion. These errors can reduce sensitiv
19、ity to corrosive contami-nants.6.2 Temperature effects on the cation resin may alter itsequilibrium properties. Control sample temperature within theresin manufacturers temperature limits to obtain consistentresults.6.3 The large temperature effects of high purity conductivitymeasurement must be min
20、imized by sample conditioning andtemperature compensation. Although sample temperature maybe controlled closely, it may be significantly influenced by theambient temperature as it passes through the column, tubingand flow chamber. The temperature coefficient of pure water isnear 5 % of measurement p
21、er C at 25C, which can contributesubstantial errors if not compensated properly. Temperaturecompensation must be appropriate for the unique acidic com-position of cation conductivity samples. Conventional highpurity temperature compensation for neutral mineral contami-nants is not suitable for this
22、application (7 and 8). The user iscautioned that the accuracy of algorithms for cation conduc-tivity compensation may vary widely. The user should deter-mine the applicability and accuracy of the instruments tem-perature compensation in the anticipated temperature range.6.4 Carbon dioxide may be in
23、a sample and will beconverted to carbonic acid and raise cation conductivity. Thisis not strictly an interference; however, carbon dioxide gener-ally is not as corrosive as mineral salts and enters the cycle bydifferent means. Where it is commonly present it may bedesirable to obtain a cation conduc
24、tivity measurement withcarbon dioxide removed (see Test Method D4519.)6.5 Carbon dioxide may also be aspirated as a component ofair, into the sample line through loose fittings in the exchangecolumn, flowmeter, valves, etc. This is not representative of theactual sampling point and produces positive
25、 errors.6.6 Incompletely regenerated or inadequately rinsed resinwill release trace ionic impurities that produce positive errors.The use of fresh resin completely in the hydrogen form andthoroughly rinsed is recommended.An exhausted resin columnwill have the same effect but with more rapidly increa
26、singerrors.6.7 Fouled resin can leach conductive components evenwith an absolutely pure influent sample. Fresh resin is recom-mended.6.8 Some cation resins contain leachables which can raisebackground conductivity and reduce sensitivity to sampleimpurities. Extensive rinsing usually is required. A c
27、ontinuousrinsing scheme is given in Section X1.2. Some success also hasbeen achieved with a hydrochloric acid (1 + 4) pre-rinse.6.9 For interferences with basic high purity conductivitymeasurements, refer to Test Method D5391.7. Apparatus7.1 Cation Exchange Column:7.1.1 The cation exchange column sh
28、all have an insidediameter of less than 60 mm (2.4 in.) and produce a flowvelocity greater than 300 mm/min (1 ft/min) at the sample flowrate (see Appendix X1). The column shall have end screens todistribute flow across the cross-section of the column and toprevent resin beads and fines from escaping
29、. The column maybe piped for upward or downward flow. Upward flow providesautomatic purging of air at startup which is helpful in cyclingplants. However, the resin must be packed full to preventfluidizing and channeling. Downward flow eliminates thepossibility of fluidizing but requires the means to
30、 vent air fromthe column at startup. Care must be exercised to eliminate allair pockets which could cause channeling. The column shouldbe constructed of nonleaching material, such as polycarbonateor polypropylene. Materials, such as polyvinylchloride, mayleach chlorides and are not recommended. Flex
31、ible tubing usedto make connections to the column should have minimal lengthand diameter to minimize the amount of leaching and air(carbon dioxide) permeation.7.1.2 The resin shall be a sulfonated styrene-divinylbenzenewith at least 8 % cross-linkage, strong acid gel cation exchangeresin in the hydr
32、ogen form, filling the column. An indicatingresin which changes color as its hydrogen ions are displaced isstrongly preferred for convenient monitoring of the progress ofresin exhaustion through the column.7.1.3 The resin must be rinsed to remove leachables beforefull sensitivity can be reached. A c
33、onvenient arrangement ofmultiple resin columns to provide the rinse and for easychange-out is described in Section X1.2.7.2 Process SensorThe conductivity cell shall be suitablefor measurement of high purity water and shall include an3The boldface numbers given in parentheses refer to a list of refe
34、rences at theend of this standard.D6504 11 (2016)12integral temperature sensor for simultaneous temperature mea-surement within the cell volume. The temperature measure-ment shall be used for compensation in the instrument asdescribed in 6.3 and in Test Method D5391. The cell shall behoused in a sma
35、ll volume flow chamber to provide fastresponse.7.3 Process InstrumentThe instrument shall providemeasurement, indication and temperature compensation asdescribed in 6.3 and Test Method D5391. It also may includealarm relays and analog or digital output signals as required bythe application.8. Reagen
36、ts8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society wheresuch specifications are available.4Other grades may be use
37、d,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.8.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water as definedby Type III of Specification D1
38、193.8.3 Hydrochloric Acid (1 + 4)Mix one volume of concen-trated HCl (sp gr 1.19) with 4 volumes of water.9. Sampling9.1 For sampling refer to Practices D1066, D3370, andD5540, as well as Test Method D5391. Cation conductivity isone of the highest purity, lowest conductivity measurements ina power p
39、lant, and therefore, is vulnerable to trace contamina-tion. Care should be exercised in closely following propersampling techniques.10. Calibration10.1 For calibration refer to Test Methods D1125 andD5391.11. Procedure11.1 Connect the apparatus as shown in Fig. 1 or SectionX1.2, for continuous sampl
40、ing and measurement. Follow thecolumn manufacturers instructions for purging air from thecation exchange column.11.2 Set sample and bypass flowrates as needed to providesufficient sample velocity in the main sample line and therecommended sample flow through the column. See 7.1.1,Section X1.1, and m
41、anufacturers instructions.11.3 Measure conductivity continuously, referring to TestMethod D5391.11.4 Monitor for resin exhaustion. With indicating resin,note color change and replace the column when 75 % of thecolumn length has been exhausted. With conventional resin,keep a record of the total time,
42、 flow, and specific conductivityvalues of the sample during the exchange life of the resin. Usethis for scheduling future resin replacement well before ex-haustion.12. Keywords12.1 boiler cycle chemistry; cation conductivity; on-line;process measurementAPPENDIX(Nonmandatory Information)X1. CATION EX
43、CHANGE COLUMNX1.1 Column DiameterX1.1.1 The flowrate and column inside diameter shouldprovide a flow velocity of at least 300 mm/min to minimizeleaching from the resin. Fig. X1.1 illustrates this relationship.X1.2 Continuous Resin Rinse SchemeX1.2.1 Lead and trail cation resin columns allow continuo
44、usrinsing of the trailing column while the lead column is“working.” When the lead column is exhausted the trailingcolumn is rinsed fully, air has been purged and it can be valvedeasily into the lead position with minimal interruption. Theexhausted column is replaced and valved in for rinsing. Figs.X
45、1.2-X1.4 illustrate the three modes of operation with heavylines and shaded valve ports indicating the sample flowdirection (9).4Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the America
46、n Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd, Poole, Dorset, U.K., and the United States Pharmacopeia andNational Formulary, U.S. Pharmaceutical Convention Inc. (USPC), Rockville, MD. FIG. 1 Cation Conductivity Apparatus (Flow Direction Throughthe Column May Also Be Down
47、ward, See 7.1.1)D6504 11 (2016)13FIG. X1.1 Sample Flowrate Versus Column Inside DiameterFIG. X1.2 Column 1 Is Exchanging Cations and Column 2 Is Rins-ingD6504 11 (2016)14REFERENCES(1) Scheerer, C. C., Cluzel, J., and Lane, R. W., “Monitoring CondensatePolisher Operation Using Conductivity (Specific,
48、 Cation, and De-gassed Cation) and Sodium Analysis,” International Water Confer-ence Proceedings, Engineers Society of Western Pennsylvania,Pittsburgh, 1989, pp. 321334.(2) “Interim Consensus Guidelines on Fossil Plant Cycle Chemistry,”Report CS4629, Electric Power Research Institute, Palo Alto, CA,
49、1986.(3) “Cycle Chemistry Guidelines for Fossil Plants: All-VolatileTreatment,” (Report TR-105041); “Cycle Chemistry Guidelines forFossil Plants: Oxygenated Treatment,” (Report TR-102285); “CycleChemistry Guidelines for Fossil Plants: Phosphate Treatment forDrum Units,” (Report TR-103665), “Guideline Manual on Instru-ments or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ 11
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