ASTM_D_6326_-_08_2014.pdf

Designation:D632608(Reapproved 2014)Standard Practice forThe Selection of Maximum Transit-Rate Ratios and Depthsfor the U.S.Series of Isokinetic Suspended-SedimentSamplers1This standard is issued under the fixed designation D6326;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 parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This practice covers the maximum transit-rate ratios anddepths for selected suspended-sediment sampler-nozzle-container configurations.1.2 This practice explains the reasons for limiting thetransit-rate ratio and depths that suspended-sediment samplerscan be correctly used.1.3 This practice give maximum transit-rate ratios anddepths for selected isokinetic suspended-sediment sampler/nozzle/container size for samplers developed by the FederalInteragency Sedimentation Project.1.4 Throughout this practice,a samplers lowering rate isassumed to be equal to its raising rate.1.5 The values stated in inch-pound units are to be regardedas standard.The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.6 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 determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD4410 Terminology for Fluvial SedimentD4411 Guide for Sampling Fluvial Sediment in Motion3.Terminology3.1 DefinitionsFor definitions of terms used in thispractice,refer to Terminology D1129 and Terminology D4410.3.2 Definitions of Terms Specific to This Standard:3.2.1 approach anglethe angle between the velocity vec-tor of the approaching flow and the centerline of the nozzle.3.2.2 approaching flowflow immediately upstream of anozzles entrance.3.2.3 bag samplera suspended-sediment sampler that usesa flexible collapsible bag as a sample container.3.2.4 compression ratethe rate at which the air is com-pressed in the sample container and is a function of the speedat which the sampler is lowered in the sampling vertical.3.2.5 isokineticthe conditions under which the directionand speed of the flowing water/sediment mixture are un-changed upon entering the nozzle of a suspended-sedimentsampler.3.2.6 maximum transit ratethe maximum speed at whichthe sampler can be lowered and raised in the sampling verticaland still have the sample collected isokinetically.3.2.7 transit ratethe speed at which the suspended sedi-ment sampler is lowered and raised in the sampling vertical.3.2.8 transit-rate ratiothe ratio computed by dividing thetransit rate by the mean stream velocity in the vertical beingsampled.4.Summary of Practice4.1 This practice describes the maximum transit-rate ratiosand depths that can be used for selected isokinetic suspended-sediment sampler/nozzle/container configurations to ensureisokinetic sampling.(Manufacturing differences in the produc-tion of sediment samplers may result in some samplers notcollecting a sample isokinetically.It is the users responsibilityto ensure through calibration that the sampler does collect asample isokinetically.Guide D4411 describes a process forchecking calibration of suspended-sediment samplers.)1This practice is under the jurisdiction of ASTM Committee D19 on Water andthe direct responsibility of Subcommittee D19.07 on Sediments,Geomorphology,and Open-Channel Flow.Current edition approved Jan.1,2014.Published March 2014.Originallyapproved in 1998.Last previous edition approved in 2008 as D6326 08.DOI:10.1520/D6326-08R14.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.Significance and Use5.1 This practice describes the maximum transit-rate ratiosand depths that can be used for selected isokinetic suspended-sediment sampler/nozzle/container configurations in order toinsure isokinetic sampling.5.2 This practice is designed to be used by field personnelcollecting whole-water samples from open channel flow.6.Background6.1 The distribution of velocity and sediment concentrationin a sampling vertical is very complex.The velocity of the flowwill generally decrease with depth while the suspended-sediment concentration will normally increase with depth in avertical.For a sediment sampler to collect a representativevolume,the water-sediment mixture must enter the nozzlewithout undergoing a change in direction or speed.Ideally,thewater must