ASTM D3370-2008 Standard Practices for Sampling Water from Closed Conduits《从关闭水管中的抽取水样的标准实施规程》.pdf

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1、Designation: D 3370 08Standard Practices forSampling Water from Closed Conduits1This standard is issued under the fixed designation D 3370; 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 pare

2、ntheses 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 fr

3、om 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 17Prac

4、tice BComposite Samples 18 to 23Practice CContinual 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 This standard does not purport to add

5、ress 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 determine the applica-bility of regulatory limitations prior to use. For specific hazardsstatements, see 8.3 and 13.4.2. Ref

6、erenced Documents2.1 ASTM Standards:2A 106/A 106M Specification for Seamless Carbon SteelPipe for High-Temperature ServiceA 179/A 179M Specification for Seamless Cold-DrawnLow-Carbon Steel Heat-Exchanger and Condenser TubesA 269 Specification for Seamless and Welded AusteniticStainless Steel Tubing

7、for General ServiceA 335/A 335M Specification for Seamless Ferritic Alloy-Steel Pipe for High-Temperature ServiceD 1066 Practice for Sampling SteamD 1129 Terminology Relating to WaterD 1193 Specification for Reagent WaterD 3648 Practices for the Measurement of RadioactivityD 3694 Practices for Prepa

8、ration of Sample Containers andfor Preservation of Organic ConstituentsD 3856 Guide for Good Laboratory Practices in Laborato-ries Engaged in Sampling and Analysis of WaterD 4453 Practice for Handling of Ultra-Pure Water SamplesD 4840 Guide for Sample Chain-of-Custody ProceduresD 4841 Practice for E

9、stimation of Holding Time for WaterSamples Containing Organic and Inorganic ConstituentsD 5540 Practice for Flow Control and Temperature Controlfor On-Line Water Sampling and Analysis3. Terminology3.1 DefinitionsFor definitions used in these practices,refer to Terminology D 1129.3.2 Definitions of T

10、erms Specific to This Standard:3.2.1 back pressure regulatora device designed to main-tain a constant pressure upstream of itself (variable or fixedback pressure regulators are available) to maintain constantflow in analyzers in continual sampling.3.2.2 composite samplea series of grab samples inte-

11、grated into a single sample or a sample collected at specifictime intervals and integrated into a single sample. The goal ofa composite sample is to characterize a process weightedaverage in proportion to process parameters.3.2.3 grab samplea single sample from a process stream(flowing) or from a so

12、urce of confined geometry (stagnant)withdrawn at a specific time. The goal of withdrawing a grabsample is to obtain a small portion of the process stream orconfined geometry source in order to characterize the entiresystem.NOTE 1Contemporary designs of back pressure regulators provideexcellent sensi

13、tivity to pressure change and have eliminated the need forhead cups and the concurrent space and maintenance problems as well assample contamination potential.1These practices are under the jurisdiction of ASTM Committee D19 on Waterand are the direct responsibility of Subcommittee D19.03 on Samplin

14、g Water andWater-Formed Deposits, Analysis of Water for Power Generation and Process Use,On-Line Water Analysis, and Surveillance of WaterCurrent edition approved Oct. 1, 2008. Published October 2008. Originallyapproved in 1974. Last previous edition approved in 2007 as D 3370 07.2For referenced AST

15、M 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshoho

16、cken, PA 19428-2959, United States.3.2.4 pressure reducera device designed to reduce pres-sure, and therefore control flow, of sample to a pressure levelwhere it can be regulated easily. This device shall be locateddownstream of the cooled sample where cooling is required.3.2.5 sample coolera small

17、heat exchanger designed toprovide primary or secondary cooling, or both, of small processsampling streams of water or steam.3.2.6 time responsethe time required for the system toreach 63.2 % of the total change between the state of initialequilibrium in response to a step change introduced at the in

18、putto the system.3.2.7 variable rod in tube orificea type of pressure re-ducer for high pressure samples that uses a retractable taperedrod inside a reamed tube to provide a variable orifice forpressure reduction that is parallel with the sample flow. Thiseliminates wear of the orifice and provides

19、variable pressurereduction 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

20、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 collected atvaried time intervals. Alternatively, the composite may consistof portions collected at various sites or a combinatio

21、n 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 grab samples from a continuouslyflowing sample stream.5. Significance and Use5.1 The goal of sampling is to obtain for analys

22、is 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, time of sampling,frequency of sampling, and proper procedures to maintain theintegrity of the sample prior to analysis.5.2 H

23、omogeneity 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 may bepractical to determine and understand interrelationships so thatresults obtained at a minimum number of points may be u

24、sedto 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 representativeness of samples cannot be aprerequisite to the selection of a sampling point. The degree ofrepresentativeness of th

25、e 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 from tests on the sample.5.4 The samples shall be of sufficient volume and shall betaken frequently enough to permit reproducibil

26、ity 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 compliance with Guide D 3856.6. Interferences6.1 If chemicals are injected or other streams are introducedinto the medium to be samp

27、led, 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 4000), locating the samplecollection point an equivalent length of 25 diameters down-stream of the chemical injection point i

28、s considered acceptable.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 contac

29、t with air. Additional require-ments are given in Practice D 4453.7. 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, m

30、inimize conditioning requirements, 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. S

31、mall 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 emptied with changesin flow conditions and may result in sample contamination.Sample tubing shall be shaped so that sharp bends, d

32、ips, andlow points are 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 prot

33、ectsample lines from exposure to extreme temperatures.NOTE 2Studies (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 equilibr

34、ium. 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 these factors, but,other velocities can provide acceptable results. Sample velocity should beconsidered as a key design issue along with

35、 type of sample, lag time,pressure 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 from which the sample linesare made shall conform to the requirements of the appli

36、cablespecifications as follows:3The boldface numbers in parentheses refer to the list of references at the end ofthis standard.D3370082ASTM DesignationPipe (seamless carbon steel for high-temperatureservice)Specification A 106Pipe (seamless ferritic alloy-steel for high-temperatureservice)Specificat

37、ion A 335Tubing (seamless carbon-steel for high-temperatureservice)Specification A 179Tubing (seamless or welded alloy-steel for high-temperature service)Specification A 269Tubing, Plastic (polyethylene), or equivalentnon-leaching inert materialsCarbon steel pipe or tubing may be satisfactory for sa

38、mplinglines 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 austeni

39、ticstainless steels are commonly used (6).NOTE 3Plastic 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

40、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 selected based on thespecific service of the valve/f

41、itting.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 co

42、oler 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 flow at the ratesrequired to give the most rep

43、resentative sample (see Note 2).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 arerecommend

44、ed 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 pressure reductions because of suscep-tibili

45、ty 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 sensitive, the flowrate in the branch circuits s

46、hall 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 D 5540 for additionalinformation. Because of the relationship of pressure and flow,a zone of constant pressure w

47、ill 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

48、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 isnot recommended. A forepressure regulator alone will notprovide a constant s

49、ample line 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 establis