1、Designation: D3370 18Standard Practices forSampling Water from Flowing Process Streams1This standard is issued under the fixed designation D3370; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number i
2、n parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 These practices cover the equipment and methods forsampli
3、ng water from closed conduits such as process streams atpower stations for chemical, physical, microbiological, andradiological analyses. It does not cover specialized equipmentrequired for and unique to a specific test or method of analysis.The following are included:SectionsPractice AGrab Samples
4、917Practice BComposite Samples 1823Practice COn-Line Sampling 24291.2 For information on specialized sampling equipment,tests or methods of analysis, reference should be made toVolumes 11.01 and 11.02 of the Annual Book of ASTMStandards, relating to water.1.3 The values stated in SI units are to be
5、regarded asstandard. The values given in parentheses are mathematicalconversions to inch-pound units that are provided for informa-tion only and are not considered standard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibili
6、ty of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.For specific hazards statements, see 8.3 and 13.4.1.5 This international standard was developed in accor-dance with internatio
7、nally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2A106/A106M
8、 Specification for Seamless Carbon Steel Pipefor High-Temperature ServiceA179/A179M Specification for Seamless Cold-Drawn Low-Carbon Steel Heat-Exchanger and Condenser TubesA269 Specification for Seamless and Welded AusteniticStainless Steel Tubing for General ServiceA335/A335M Specification for Sea
9、mless Ferritic Alloy-Steel Pipe for High-Temperature ServiceD1066 Practice for Sampling SteamD1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD3648 Practices for the Measurement of RadioactivityD3694 Practices for Preparation of Sample Containers andfor Preservation of Organic
10、 ConstituentsD3856 Guide for Management Systems in LaboratoriesEngaged in Analysis of WaterD4453 Practice for Handling of High Purity Water SamplesD4840 Guide for Sample Chain-of-Custody ProceduresD4841 Practice for Estimation of Holding Time for WaterSamples Containing Organic and Inorganic Constit
11、uentsD5540 Practice for Flow Control and Temperature Controlfor On-Line Water Sampling and Analysis3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this standard, refer toTerminology D1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 back-pressure regulator, na device
12、 designed tomaintain a constant pressure upstream of itself (variable orfixed back pressure regulators are available) to maintainconstant flow in analyzers in on-line sampling.3.2.1.1 DiscussionContemporary designs of back-pressure regulators provide excellent sensitivity to pressure1These practices
13、 are under the jurisdiction of ASTM Committee D19 on Waterand are the direct responsibility 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 Dec. 15, 201
14、8. Published January 2019. Originallyapproved in 1974. Last previous edition approved in 2010 as D3370 10. DOI:10.1520/D3370-18.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume informatio
15、n, 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 StatesThis international standard was developed in accordance with internationally recognized principles on standardization es
16、tablished in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1variations. They require less space, have fewer maintenanceproblems, and reduce sample-contamination p
17、otential.3.2.2 composite sample, na series of grab samples inte-grated into a single sample or a sample collected at specifictime intervals and integrated into a single sample.3.2.2.1 DiscussionThe goal of a composite sample is tocharacterize a process-weighted average in proportion to pro-cess para
18、meters.3.2.3 grab sample, na single sample from a processstream (flowing) or from a source of confined-geometry(stagnant) withdrawn at a specific time.3.2.3.1 DiscussionThe goal of withdrawing a grab sampleis to obtain a small portion of the process stream or confinedgeometry source in order to char
19、acterize the entire system.3.2.4 pressure reducer, na device designed to reducepressure, and therefore control flow, of sample to a pressurelevel where regulation is easily achieved.3.2.4.1 DiscussionThis device shall be located down-stream of the cooled sample where cooling is required.3.2.5 sample
20、 cooler, na small heat exchanger designed toprovide primary or secondary cooling, or both, of samplingstreams of water or steam.3.2.6 variable rod in tube orifice, nfor high pressuresamples, a type of pressure reducer that uses a retractabletapered rod inside a reamed tube to provide a variable orif
21、icefor pressure reduction. The rods are parallel with the sampleflow. This design eliminates wear of the orifice and providesvariable pressure-reduction and flow.4. Summary of Practices4.1 These practices include three procedures for samplecollection. The first is for the collection of a grab sample
22、 ofwater at a specific site representing conditions only at the timeof sampling. Grab sampling is the only procedure suitable forbacteriological analysis and some radiological test procedures.4.2 The second practice is for collection of a compositesample at a specific site, portions of which are col
23、lected atvaried time intervals. Alternatively, the composite may consistof portions collected at various sites or a combination of bothsite and time variables.4.3 The third practice provides a continuously flowingsample from one or more sampling sites, suitable for on-lineanalyzers or for collecting
24、 grab samples from a continuouslyflowing sample stream.5. Significance and Use5.1 The goal of sampling is to obtain for analysis a portionof the main body of water that is representative. The mostcritical factors necessary to achieve this are points of sampling,and materials selection, system design
25、, time of sampling,frequency of sampling, and proper procedures to maintain theintegrity of the sample prior to analysis.5.2 Homogeneity of the process to be sampled is frequentlylacking, necessitating multiple-point sampling. If it is imprac-tical to utilize a most-representative sampling point, it
26、 may bepractical to determine and understand interrelationships so thatresults obtained at a minimum number of points may be usedto characterize the system.5.3 Samples collected from a single point in a system arealways recognized as being non-representative to some degree.For this reason, total rep
27、resentativeness of samples cannot be aprerequisite to the selection of a sampling point. The degree ofrepresentativeness of the sample shall be assessed and theassessment made a part of the permanent record. This willprevent an artificial degree of accuracy from being assigned tothe data derived fro
28、m tests on the sample.5.4 The samples shall be of sufficient volume and shall betaken frequently enough to permit reproducibility of testingrequisite for the desired objective, as required by the method ofanalysis to be used.5.5 Laboratories or facilities conducting water samplingshould be in compli
29、ance with Guide D3856.6. Interferences6.1 If chemicals are injected or other streams are introducedinto the medium to be sampled, the sample collection pointshould be placed far enough downstream to ensure a com-pletely mixed sample.Assuming turbulent flow (for example, aReynolds number of at least
30、4000), locating the samplecollection point an equivalent length of 25 diameters down-stream of the chemical injection point is considered acceptable.An equivalent length of 50 diameters is recommended forlaminar flow.6.2 The sampling of high-purity water requires specialconsideration. Contact with a
31、ny material other than the originalcontainer subjects the sample to possible contamination oralteration. This includes contact with air. Additional require-ments are given in Practice D4453.7. Materials and Apparatus7.1 Sample Lines:7.1.1 GeneralSample lines should be designed so that thesample is r
32、epresentative of the source. They shall be as short asfeasible and of the smallest practicable bore to facilitateflushing, minimize conditioning requirements, reduce lag timeand changes in sample composition, and provide adequatevelocity and turbulence. The lines shall have sufficient strengthto pre
33、vent structural failure. The designer is responsible forensuring that applicable structural integrity requirements aremet. Small tubing is vulnerable to mechanical damage andshould be protected.7.1.1.1 Traps and pockets in which solids might settle shallbe avoided, since they may be partially emptie
34、d with changesin flow conditions and may result in sample contamination.Sample tubing shall be shaped so that sharp bends, dips, andlow points are avoided, thus preventing particulates fromcollecting. Expansion loops or other means shall be provided toprevent undue buckling and bending when large te
35、mperaturechanges occur. Such buckling and bending may damage thelines and allied equipment. Routing shall be planned to protectsample lines from exposure to extreme temperatures.D3370 182NOTE 1Studies (1-5)3on particle transport in sampling lines haveindicated that sample velocity rate and stability
36、 are important factors indetermining deposition and erosion rates on sample tube walls and timerequired to reach and maintain equilibrium. Although limited, other workhas also noted effects of sorption of dissolved species within tube walldeposits. Velocities near 1.8 m/s (6 f/s) seem to optimize th
37、ese factors, but,other velocities can provide acceptable results. Sample velocity should beconsidered as a key design issue along with type of sample, lag time,pressure drop, new or existing sample lines, etc. when determining sampleflow rates. Maintaining the selected velocity is necessary to achie
38、vesample representivity.7.1.2 MaterialsThe material from which the sample linesare made shall conform to the requirements of the applicablespecifications as follows:ASTM DesignationPipe (seamless carbon steel for high-temperatureservice)Specification A106/A106MPipe (seamless ferritic alloy-steel for
39、 high-temperature service)Specification A335/A335MTubing (seamless carbon-steel for high-temperature service)Specification A179/A179MTubing (seamless or welded alloy-steel for high-temperature service)Specification A269Tubing, Plastic (polyethylene), or equivalent non-leaching inert materialsCarbon
40、steel pipe or tubing may be satisfactory for samplinglines where levels of contaminants in the sample are high, orsample constituents require it. For sampling high-purity watersor corrosive waters, the sampling lines shall be made ofstainless steel that is at least as corrosion resistant as 18 %chro
41、mium, 8 % nickel steel (AISI 304 or 316 austeniticstainless steels are commonly used (6).NOTE 2Plastic tubing should be avoided where low values ofdissolved oxygen are to be measured since atmospheric gases may diffusethrough the tubing and cause an analytical bias. The selection of thesample line m
42、aterial should be based on the parameters of interest.7.2 Valves and Fittings:7.2.1 MaterialsValve and fitting materials should be com-patible with the sample and the sample line material selected.AISI 316 austenitic stainless steel is commonly used. Pressureand temperature ratings should be selecte
43、d based on thespecific service of the valve/fitting.7.2.2 Isolation ValvesAt least one shut off valve (com-monly referred to as a root valve) shall be placed immediatelyafter the point from which the sample is withdrawn so that thesample line may be isolated when desired. For safety purposes,an isol
44、ation valve should be placed at the sample cooler inlet (ifused) and be rated in accordance with the pressure andtemperature of the sample source.7.2.3 Pressure ReducersThe pressure reducer, in combi-nation with properly sized sample lines, is the primary com-ponent necessary to control the sample f
45、low at the ratesrequired to give the most representative sample (see Note 1).Flow control is accomplished at the same time sample pressureis reduced.7.2.3.1 For samples equal to or greater than 500 psig (3447kPa), the pressure reducer shall be a rod-in-tube type orifice orcapillary (variable or fixe
46、d). Variable rod-in-tube devices arerecommended since they offer two advantages: (a) they arecapable of varying the pressure drop and, therefore, the flow;and (b) they are cleanable in place (exercising the position ofthe tapered rod in the tube). Forepressure regulators are notrecommended for large
47、 pressure reductions because of suscep-tibility to erosion, plugging, and wire drawing of the stem orseat.7.2.3.2 For samples less than 500 psig (3447 kPa), thepressure reducer shall be a needle valve.7.2.4 Pressure RegulatorsSince most on-line analyzersare flow sensitive, as well as temperature sen
48、sitive, the flowrate in the branch circuits shall also be controlled to ensurerepeatable analytical results. This is achieved by establishing aconstant pressure zone where the sample line feeds theanalyzer branch lines. See Practice D5540 for additionalinformation. Because of the relationship of pre
49、ssure and flow,a zone of constant pressure will ensure that each analyzer fedfrom this zone gets a constant flow rate independent of actionstaken in the other branch lines while maintaining constant flowin the main sample line. Maintaining constant flow is alsoessential in regularly monitored grab samples. Two methodsare available to achieve this constant pressure zone in conjunc-tion with the upstream pressure reducer: (1) back pressureregulator (fixed or variable) or (2) head cup. Using a forepres-sure regulator without a back pressure regulator or head cup
