1、Designation: D3370 10Standard Practices forSampling Water from Closed Conduits1This 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 in parent
2、heses 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 Department of Defense.1. Scope1.1 These practices cover the equipment and methods forsampling water from
3、 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 9 to 17Practi
4、ce BComposite Samples 18 to 23Practice COn-Line Sampling 24 to 291.2 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 r
5、egarded asstandard. The values listed in parenthesis are for informationonly.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 establish appro-priate safety and health practices and determ
6、ine the applica-bility of regulatory limitations prior to use. For specific hazardsstatements, see 8.3 and 13.4.2. Referenced Documents2.1 ASTM Standards:2A106/A106M Specification for Seamless Carbon Steel Pipefor High-Temperature ServiceA179/A179M Specification for Seamless Cold-DrawnLow-Carbon Ste
7、el Heat-Exchanger and Condenser TubesA269 Specification for Seamless and Welded AusteniticStainless Steel Tubing for General ServiceA335/A335M Specification for Seamless Ferritic Alloy-Steel Pipe for High-Temperature ServiceD1066 Practice for Sampling SteamD1129 Terminology Relating to WaterD1193 Sp
8、ecification for Reagent WaterD3648 Practices for the Measurement of RadioactivityD3694 Practices for Preparation of Sample Containers andfor Preservation of Organic ConstituentsD3856 Guide for Good Laboratory Practices in Laborato-ries Engaged in Sampling and Analysis of WaterD4453 Practice for Hand
9、ling of Ultra-Pure Water SamplesD4840 Guide for Sample Chain-of-Custody ProceduresD4841 Practice for Estimation of Holding Time for WaterSamples Containing Organic and Inorganic ConstituentsD5540 Practice for Flow Control and Temperature Controlfor On-Line Water Sampling and Analysis3. Terminology3.
10、1 DefinitionsFor definitions used in these practices,refer to Terminology D1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 back-pressure regulator, na device designed tomaintain a constant pressure upstream of itself (variable orfixed back pressure regulators are available) to maintain
11、constant flow in analyzers in on-line sampling.3.2.1.1 DiscussionContemporary designs of back-pressure regulators provide excellent sensitivity to pressurevaiations. They require less space, have fewer maintenanceproblems, and reduce sample-contamination potential.3.2.2 composite sample, na series o
12、f grab samples inte-grated into a single sample or a sample collected at specifictime intervals and integrated into a single sample.1These practices are under the jurisdiction of ASTM Committee D19 on Waterand are the direct responsibility of Subcommittee D19.03 on Sampling Water andWater-Formed Dep
13、osits, Analysis of Water for Power Generation and Process Use,On-Line Water Analysis, and Surveillance of WaterCurrent edition approved Dec. 1, 2010. Published December 2010. Originallyapproved in 1974. Last previous edition approved in 2009 as D3370 09. DOI:10.1520/D3370-10.2For referenced ASTM sta
14、ndards, 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken,
15、 PA 19428-2959, United States.3.2.2.1 DiscussionThe goal of a composite sample is tocharacterize a process-weighted average in proportion to pro-cess parameters.3.2.3 grab sample, na single sample from a processstream (flowing) or from a source of confined-geometry(stagnant) withdrawn at a specific
16、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 characterize the entire system.3.2.4 pressure reducer, na device designed to reducepressure, and therefore control flow, of sample to a pressurelevel
17、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 cooler, na small heat exchanger designed toprovide primary or secondary cooling, or both, of samplingstreams of water or steam.3.2.6 variable rod
18、 in tube orifice, nfor high pressuresamples, a type of pressure reducer that uses a retractabletapered rod inside a reamed tube to provide a variable orificefor pressure reduction. The rods are parallel with the sampleflow. This design eliminates wear of the orifice and providesvariable pressure-red
19、uction and flow.4. Summary of Practices4.1 These practices include three procedures for samplecollection. The first is for the collection of a grab sample ofwater at a specific site representing conditions only at the timeof sampling. Grab sampling is the only procedure suitable forbacteriological a
20、nalysis and some radiological test procedures.4.2 The second practice is for collection of a compositesample at a specific site, portions of which are collected atvaried time intervals. Alternatively, the composite may consistof portions collected at various sites or a combination of bothsite and ti
21、me variables.4.3 The third practice provides a continuously flowingsample from one or more sampling sites, suitable for on-lineanalyzers or for collecting grab samples from a continuouslyflowing sample stream.5. Significance and Use5.1 The goal of sampling is to obtain for analysis a portionof the m
22、ain body of water that is representative. The mostcritical factors necessary to achieve this are points of sampling,and materials selection, system design, time of sampling,frequency of sampling, and proper procedures to maintain theintegrity of the sample prior to analysis.5.2 Homogeneity of the pr
23、ocess to be sampled is frequentlylacking, necessitating multiple-point sampling. If it is imprac-tical to utilize a most-representative sampling point, it may bepractical to determine and understand interrelationships so thatresults obtained at a minimum number of points may be usedto characterize t
24、he 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 representativeness of samples cannot be aprerequisite to the selection of a sampling point. The degree ofrepresentativeness of the sample shall be as
25、sessed and theassessment made a part of the permanent record. This willprevent an artificial degree of accuracy from being assigned tothe data derived from tests on the sample.5.4 The samples shall be of sufficient volume and shall betaken frequently enough to permit reproducibility of testingrequis
26、ite for the desired objective, as required by the method ofanalysis to be used.5.5 Laboratories or facilities conducting water samplingshould be in compliance with Guide D3856.6. Interferences6.1 If chemicals are injected or other streams are introducedinto the medium to be sampled, the sample colle
27、ction pointshould be placed far enough downstream to ensure a com-pletely mixed sample.Assuming turbulent flow (for example, aReynolds number of at least 4000), locating the samplecollection point an equivalent length of 25 diameters down-stream of the chemical injection point is considered acceptab
28、le.An equivalent length of 50 diameters is recommended forlaminar flow.6.2 The sampling of high-purity water requires specialconsideration. Contact with any material other than the originalcontainer subjects the sample to possible contamination oralteration. This includes contact with air. Additiona
29、l 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 representative of the source. They shall be as short asfeasible and of the smallest practicable bore to facilitateflushing, minimize conditioning r
30、equirements, reduce lag timeand changes in sample composition, and provide adequatevelocity and turbulence. The lines shall have sufficient strengthto prevent structural failure. The designer is responsible forensuring that applicable structural integrity requirements aremet. Small tubing is vulnera
31、ble 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 emptied with changesin flow conditions and may result in sample contamination.Sample tubing shall be shaped so that sharp bends, dips, andlow points are
32、 avoided, thus preventing particulates fromcollecting. Expansion loops or other means shall be provided toprevent undue buckling and bending when large temperaturechanges occur. Such buckling and bending may damage thelines and allied equipment. Routing shall be planned to protectsample lines from e
33、xposure to extreme temperatures.NOTE 1Studies (15)3on particle transport in sampling lines haveindicated that sample velocity rate and stability are important factors indetermining deposition and erosion rates on sample tube walls and timerequired to reach and maintain equilibrium. Although limited,
34、 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 these factors, but,other velocities can provide acceptable results. Sample velocity should beconsidered as a key design issue along with type of sample, lag t
35、ime,3The boldface numbers in parentheses refer to the list of references at the end ofthis standard.D3370 102pressure drop, new or existing sample lines, etc. when determining sampleflow rates. Maintaining the selected velocity is necessary to achievesample representivity.7.1.2 MaterialsThe material
36、 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 high-temperatureservice)Specification A335/A335MTu
37、bing (seamless carbon-steel for high-temperatureservice)Specification A179/A179MTubing (seamless or welded alloy-steel for high-temperature service)Specification A269Tubing, Plastic (polyethylene), or equivalentnon-leaching inert materialsCarbon steel pipe or tubing may be satisfactory for samplingl
38、ines 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 %chromium, 8 % nickel steel (AISI 304 or 316 austeniticstai
39、nless steels are commonly used (6).NOTE 2Plastic tubing should be avoided where low values of dis-solved oxygen are to be measured since atmospheric gases may diffusethrough the tubing and cause an analytical bias. The selection of thesample line material should be based on the parameters of interes
40、t.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 selected based on thespecific service of the valve/fitting.
41、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 isolation valve should be placed at the sample cooler in
42、let (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 flow at the ratesrequired to give the most representa
43、tive 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 fixed). Variable rod-in-tube devices arerecommended sinc
44、e 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 pressure reductions because of suscep-tibility to e
45、rosion, 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 sensitive, the flowrate in the branch circuits shall al
46、so 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 pressure and flow,a zone of constant pressure will ensu
47、re 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 con
48、stant 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 isnot recommended. A forepressure regulator alone will notprovide a constant sample li
49、ne flow. Flow changes in thebranch lines below the regulator result in the forepressureregulator closing or opening to maintain the analyzer inletpressure thereby changing the main sample line flow anddisrupting the representivity of the sample from its source.7.2.4.1 Use of a back pressure regulator is the preferredmethod to achieve the constant pressure zone. Total sampleflow is established using the primary pressure reducer with allflow going through the back pressure regulating valve to drain,recovery, or for grab sample. The regulating valve establishesa
