1、Designation: D6504 11Standard 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, the year of last
2、revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice describes continuous sample conditioningby hydrogen ion exchange and measurement by electrolyticconductivity.
3、 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 S/cm.1.2 The actual conductivity measurements are made usingTest Method D5391.1.3 T
4、his practice does not provide for separate determina-tion of dissolved carbon dioxide. Refer to Test Methods D2186and D4519.1.4 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system may not be exact equivalents; therefore,
5、eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the 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 e
6、stablish appro-priate 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
7、WaterD1193 Specification for Reagent WaterD2186 Test Methods for Deposit-Forming Impurities inSteamD3370 Practices for Sampling Water from Closed ConduitsD3864 Guide for Continual On-Line Monitoring Systemsfor Water Analysis3D4519 Test Method for On-Line Determination of Anionsand Carbon Dioxide in
8、High Purity Water by CationExchange and Degassed Cation ConductivityD5391 Test Method for 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 defin
9、itions of terms used in this prac-tice, refer to Test Methods D1125, Terminology D1129, andPractice 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 colum
10、n and then measuring itselectrolytic conductivity, on-line.3.2.2 specific conductivity, ndirect 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 sma
11、llcation exchange column in the hydrogen form, which ex-changes all cations for H+. In this process, 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
12、 Temperature conditioning of the sample and specializedcompensation of the measurement are used to minimize1This 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
13、Power Generation and Process Use,On-Line Water Analysis, and Surveillance of Water.Current edition approved May 1, 2011. Published May 2011. Originallyapproved in 1999. Last previous edition approved in 2007 as D6504 07. DOI:10.1520/D6504-11.2For referenced ASTM standards, visit the ASTM website, ww
14、w.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.3Withdrawn.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United
15、States.temperature effects on the performance of the ion exchangeresin and the measurement.4.4 Few studies have been published on the performance ofcation conductivity measurement but one collaborative effortprovides some background (1).45. Significance and Use5.1 Cation conductivity provides one of
16、 the most sensitiveand dependable on-line means of detecting anionic contamina-tion in the boiler/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 chemi
17、cal(s), for example, ammoniaand amines, from the sample and converting remaining saltcontaminants 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
18、ASME (5,6).5.4 The sample effluent from the cation exchange columnalso may be used, and in some 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 negativeerr
19、ors in the measurement depending on the sample composi-tion. These errors can reduce sensitivity 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 consisten
20、tresults.6.3 The large temperature effects of high purity conductivitymeasurement must be minimized 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,
21、tubingand flow chamber. The temperature coefficient of pure water isnear 5 % of measurement per 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 hi
22、ghpurity temperature compensation for neutral mineral contami-nants is not suitable for this application (7,8). 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
23、-perature compensation in the anticipated temperature range.6.4 Carbon dioxide may be in 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 byd
24、ifferent means. Where it is commonly present it may bedesirable to obtain a cation conductivity measurement withcarbon dioxide removed (see Test Methods D2186 and D4519.6.5 Carbon dioxide may also be aspirated as a component ofair, into the sample line through loose fittings in the exchangecolumn, f
25、lowmeter, valves, etc. This is not representative of theactual sampling point and produces positive 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 ri
26、nsed is recommended.An exhausted resin columnwill have the same effect but with more rapidly increasingerrors.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
27、conductivity and reduce sensitivity to sampleimpurities. Extensive rinsing usually is required. A continuousrinsing scheme is given in Appendix X1.2. Some success alsohas been achieved with a hydrochloric acid (1+4) pre-rinse.6.9 For interferences with basic high purity conductivitymeasurements, ref
28、er to Test Method D5391.7. Apparatus7.1 Cation Exchange Column:7.1.1 The cation exchange column shall 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 todistri
29、bute flow across the cross-section of the column and toprevent resin beads and fines from escaping. 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 preventfluidizi
30、ng and channeling. Downward flow eliminates thepossibility of fluidizing but requires the means to 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 pol
31、ypropylene. Materials, such as polyvinylchloride, mayleach chlorides and are not recommended. Flexible 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 styre
32、ne-divinylbenzenewith at least 8 % cross-linkage, strong acid gel cation exchangeresin in the hydrogen 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 col
33、umn.7.1.3 The resin must be rinsed to remove leachables beforefull sensitivity can be reached. A convenient arrangement ofmultiple resin columns to provide the rinse and for easychange-out is described in X1.2.7.2 Process Sensor The conductivity cell shall be suitablefor measurement of high purity w
34、ater and shall include anintegral temperature sensor for simultaneous temperature mea-surement within the cell volume. The temperature measure-ment shall be used for compensation in the instrument as4The boldface numbers given in parentheses refer to a list of references at theend of this standard.D
35、6504 112described in 6.3 and in Test Method D5391. The cell shall behoused in a small volume flow chamber to provide fastresponse.7.3 Process InstrumentThe instrument shall provide mea-surement, indication and temperature compensation as de-scribed in 6.3 and Test Method D5391. It also may includeal
36、arm relays and analog or digital output signals as required bythe application.8. Reagents8.1 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 Am
37、erican Chemical Society wheresuch specifications are available.5Other grades may be used,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 wa
38、ter shall be understood to mean reagent water as definedby Type III of Specification D1193.8.3 Hydrochloric Acid (1 + 4)Mix one volume of con-centrated 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
39、 conductivity isone of the highest purity, lowest conductivity measurements ina power plant, 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. Proc
40、edure11.1 Connect the apparatus as shown in Fig. 1 or X1.2, forcontinuous sampling and measurement. Follow the columnmanufacturers instructions for purging air from the cationexchange column.11.2 Set sample and bypass flowrates as needed to providesufficient sample velocity in the main sample line a
41、nd therecommended sample flow through the column. See 7.1.1,X1.1 and manufacturers 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 be
42、en exhausted. With conventional resin,keep a record of the total time, 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-l
43、ine;process measurementAPPENDIX(Nonmandatory Information)X1. CATION EXCHANGE 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
44、 Rinse SchemeX1.2.1 Lead and trail cation resin columns allow continuousrinsing 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 interrupt
45、ion. Theexhausted column is replaced and valved in for rinsing. Figs.X1.2-X1.4 illustrate the three modes of operation with heavylines and shaded valve ports indicating the sample flowdirection (9).5Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Washington, D
46、C. For suggestions on the testing of reagents notlisted by the American 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 Cond
47、uctivity Apparatus (Flow direction through thecolumn may also be downward. See 7.1.1.)D6504 113FIG. X1.1 Sample Flowrate Versus Column Inside DiameterFIG. X1.2 Column 1 is exchanging cations and Column 2 isrinsingD6504 114REFERENCES(1) Scheerer, C. C., Cluzel, J., and Lane, R. W., “Monitoring Conden
48、satePolisher Operation Using Conductivity (Specific, Cation, and De-gassed Cation) and Sodium Analysis,” International Water Confer-ence Proceedings, Engineers Society of Western Pennsylvania, Pitts-burgh, 1989, pp. 321334.(2) “Interim Consensus Guidelines on Fossil Plant Cycle Chemistry,”Report CS4
49、629, Electric Power Research Institute, Palo Alto, CA,1986.(3) “Cycle Chemistry Guidelines for Fossil Plants: All-Volatile Treat-ment,” (Report TR-105041); “Cycle Chemistry Guidelines for FossilPlants: Oxygenated Treatment,” (Report TR-102285); “Cycle Chem-istry Guidelines for Fossil Plants: Phosphate Treatment for DrumUnits,” (Report TR-103665), “Guideline Manual on Instruments or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).D6504 116
