ASTM D6504-2011 4375 Standard Practice for On-Line Determination of Cation Conductivity in High Purity Water《高纯度水中阳离子导电性在线测定的标准操作规程》.pdf
《ASTM D6504-2011 4375 Standard Practice for On-Line Determination of Cation Conductivity in High Purity Water《高纯度水中阳离子导电性在线测定的标准操作规程》.pdf》由会员分享,可在线阅读,更多相关《ASTM D6504-2011 4375 Standard Practice for On-Line Determination of Cation Conductivity in High Purity Water《高纯度水中阳离子导电性在线测定的标准操作规程》.pdf(6页珍藏版)》请在麦多课文档分享上搜索。
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
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