1、Designation: D 6504 07Standard Practice forOn-Line Determination of Cation Conductivity in High PurityWater1This standard is issued under the fixed designation D 6504; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of las
2、t revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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 electrolyticconductivi
3、ty. 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 D 5391.1
4、.3 This practice does not provide for separate determina-tion of dissolved carbon dioxide. Refer to Test MethodsD 2186 and D 4519.1.4 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 establis
5、h appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1066 Practice for Sampling SteamD 1125 Test Methods for Electrical Conductivity and Re-sistivity of WaterD 1129 Terminology Relating to Wate
6、rD 1193 Specification for Reagent WaterD 2186 Test Methods for Deposit-Forming Impurities inSteamD 3370 Practices for Sampling Water from Closed ConduitsD 3864 Guide for Continual On-Line Monitoring Systemsfor Water AnalysisD 4519 Test Method for On-Line Determination of Anionsand Carbon Dioxide in
7、High Purity Water by CationExchange and Degassed Cation Conductivity3D 5391 Test Method for Electrical Conductivity and Resis-tivity of a Flowing High Purity Water SampleD 5540 Practice for Flow Control and Temperature Controlfor On-Line Water Sampling and Analysis3. Terminology3.1 DefinitionsFor de
8、finitions of terms used in this prac-tice, refer to Test Methods D 1125, Terminology D 1129, andPractice D 3864.3.2 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
9、 column 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
10、 a smallcation 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/transmitt
11、er.4.3 Temperature conditioning of the sample and specializedcompensation of the measurement are used 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
12、 of Subcommittee D19.03 on Sampling Water andWater-Formed Deposits, Analysis of Water for Power Generation and Process Use,On-Line Water Analysis, and Surveillance of WaterCurrent edition approved June 15, 2007. Published June 2007. Originallyapproved in 1999. Last previous edition approved in 2000
13、as D 6504 00.2For referenced ASTM standards, visit the ASTM website, www.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 Ba
14、rr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.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 the most sen
15、sitiveand 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 chemical(s), for e
16、xample, 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 ASME (5,6).5.
17、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 negativeerrors in the me
18、asurement 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 consistentresults.6.3
19、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, tubingand flo
20、w 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 highpurity temp
21、erature 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-perature com
22、pensation 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 bydifferent mean
23、s. Where it is commonly present it may bedesirable to obtain a cation conductivity measurement withcarbon dioxide removed (see Test Methods D 2186 andD 4519.6.5 Carbon dioxide may also be aspirated as a component ofair, into the sample line through loose fittings in the exchangecolumn, flowmeter, va
24、lves, 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 rinsed is reco
25、mmended.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 conductivity
26、 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, refer to Test M
27、ethod D 5391.7. 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 todistribute flow a
28、cross 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 preventfluidizing and chan
29、neling. 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 polypropylene.
30、 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 styrene-divinylb
31、enzenewith 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 column.7.1.3 T
32、he 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 water and sh
33、all 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.D6504072desc
34、ribed in 6.3 and in Test Method D 5391. 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 D 5391. It also may includealarm relays
35、 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 American Che
36、mical 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 water shall
37、be understood to mean reagent water as definedby Type III of Specification D 1193.8.3 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 D 1066, D 3370, andD 5540, as well as Test Method D 5391. Cation cond
38、uctivity 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 D 1125 andD 5391.11. Procedu
39、re11.1 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 and
40、therecommended sample flow through the column. See 7.1.1,X1.1 and manufacturers instructions.11.3 Measure conductivity continuously, referring to TestMethod D 5391.11.4 Monitor for resin exhaustion. With indicating resin,note color change and replace the column when 75 % of thecolumn length has been
41、 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-lin
42、e;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 R
43、inse 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 interruptio
44、n. 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, DC.
45、 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 Conduc
46、tivity Apparatus (Flow direction through thecolumn may also be downward. See 7.1.1.)D6504073FIG. X1.1 Sample Flowrate Versus Column Inside DiameterFIG. X1.2 Column 1 is exchanging cations and Column 2 isrinsingD6504074REFERENCES(1) Scheerer, C. C., Cluzel, J., and Lane, R. W., “Monitoring Condensate
47、Polisher Operation Using Conductivity (Specific, Cation, and De-gassed Cation) and SodiumAnalysis,” International Water ConferenceProceedings, Engineers Society of Western Pennsylvania, Pittsburgh,1989, pp. 321334.(2) “Interim Consensus Guidelines on Fossil Plant Cycle Chemistry,”Report CS4629, Elec
48、tric 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).D6504076
