1、Designation: D6326 08 (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 ye
2、ar 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 a
3、nddepths 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 isokin
4、etic 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 v
5、alues 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 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:2D1129 Terminology Relating to WaterD4410 Terminology for Fluvial SedimentD4411 Guide for Sampling Fluvial Sediment in Motion3. Terminol
7、ogy3.1 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 f
8、lowflow 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 lower
9、ed 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
10、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 b
11、eingsampled.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
12、 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 ju
13、risdiction 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/D63
14、26-08R14.2For 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,
15、 PO Box C700, West Conshohocken, PA 19428-2959. United States15. 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 Thi
16、s 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-sed
17、iment 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 enter the nozzle at the same velocity as theapproach
18、ing flow. When the velocity is unchanged uponentering the nozzle, the condition is termed isokinetic. Depth-and point-integrating samplers sample isokinetically only iftheir nozzles point directly into the flow and the samplers areused within certain ranges of depths. Depth-integrating sam-plers als
19、o operate isokinetically only when their vertical transitrate is within a given range.6.2 If the velocity of the water-sediment mixture enteringthe nozzle exceeds that of the approach velocity, the samplesediment concentration is smaller than the concentration of theapproaching flow. Decreasing the
20、velocity in the nozzle com-pared to the approach velocity will cause the sample sedimentconcentration to be greater than that of the approaching flow.The magnitude of the difference between nozzle and approachvelocity is related to the degree of increase or decrease inconcentration. The concentratio
21、n shift is also related to thesizes of the grains in suspension. The larger the grain size, thelarger the potential shift in concentrations will be.6.3 The sampler will not operate properly if the transit rateis too fast, the sampling depth is too great, or both. See GuideD4411 for more details on p
22、roper use of depth integratingsuspended sediment samplers.6.4 Two factors control the maximum transit rate for asampler: approach angle and the compression rate.6.4.1 At a given sample vertical, as the transit rate increases,the approach angle increases. If the transit-rate exceeds 0.4times the mean
23、 flow velocity in the vertical, the intake velocityundergoes a significant acceleration due to changes in flowdirection. The maximum vertical transit rate for a depth-integrating sampler or point-integrating sampler used for depthintegrating, should not exceed 0.4 times the mean streamvelocity of th
24、e section.6.4.2 The compression rate, which is related to the compres-sion limit, may restrict the vertical transit rate to less than 0.4times the mean stream velocity when a rigid sample containeris used. As the sampler is lowered through the water, theincreasing water pressure compresses the air i
25、n the samplercontainer. If the sampler is lowered slowly, the volume of theincoming water exceeds the volume lost, the displaced air exitsthrough the samplers exhaust vent. If the sampler is loweredrapidly, the volume of the incoming water is less than thevolume lost to compression. Pressure inside
26、the samplercontainer is less than the hydrostatic pressure outside thesampler. The self regulating properties of the sampler losecontrol. The intake velocity increases above the stream veloc-ity. In severe cases, water enters the sampler through theair-exhaust vent. If the sampler is raised too rapi
27、dly, the airinside the bottle expands and, if not relieved by venting, willnot escape fast enough through the air-exhaust vent. Thepressure unbalance causes the intake velocity to be less thanthe approach velocity. The compression-rate limit is a functionof the diameter of the nozzle, volume of the
28、sample container,and altitude. For large bottles with small nozzles it can limit thevertical transit rate to less than 3 % of the mean streamvelocity. Table 1 lists the maximum transit-rates ratios forcommonly used combinations of sampler nozzle and containersizes.6.4.3 Because no air is contained i
29、nside of the bag, thecompression rate limit does not apply to bag samplers.6.5 Edwards and Glysson3discuss the proper use of thesamplers and transit-rate ratios for some of the more commoncombinations used by the US Geological Survey (USGS).Because of difficulties in maintaining a slow transit rate,
30、 theUSGS does not recommend using the USD-77 sampler.6.6 Based on compression, isokinetic inflow rates, andlimits on sample volumes to prevent overfilling,4the maximumdepth that any rigid container can be lowered to is about 15 ft(4.572 m) (FISP).5If the sampler is lowered below themaximum depth lim
31、it, the bottle overfills.As shown in Table 1,the maximum depth depend on sampler, nozzle, and containersize. Depending on the maximum percentage of useful volume,depth limit also varies with sample container size and volumeof the pressure compensating chamber for point-integratingsamplers. The value
32、s given in Table 1 are for sea levelconditions. The maximum depth decreases about 1 ft (0.3048m) for every 1000-ft (304.8-m) increase in elevation.6.6.1 The maximum depth that a bag sampler may collect asample isokineticly is limited by the nozzle and bag size. SeeTable 1.6.7 For additional informat
33、ion about isokinetic suspended-sediment samplers, see Footnote 6.67. Procedure7.1 Table 1 lists the most commonly use suspended-sediment samplers in he United States. A “D” in the nameindicates that it is a depth-integrating sampler, a “P” indicatesthat it is a point-integrating sampler.3Edwards, T.
34、K., and Glysson, G.D., “Field Methods for Measurement of FluvialSediment,” U.S. Geological Survey, Techniques of Water Resource Investigations,Book 3, Chapter C2, 1998.4Maximum sample volume to prevent over filling is assumed to be approxi-mately23 the sample container volume.5FISP, Federal Interage
35、ncy Sediment Project Report No. 6, 1952, The Design ofImproved Types of Suspended-Sediment Samplers.6Contact the Project Chief, Federal Interagency Sedimentation Project, Water-ways Experiment Station, 3909 Halls Ferry Road, Vicksburg, MS 39180-6199.D6326 08 (2014)27.2 To determine the maximum depth
36、 for a sampler, find thenozzle size and container size and then read across to themaximum depth.7.3 To determine the maximum transit-rate, find thesampler/nozzle/container to be used and read across to themaximum ratio (Rt/Vm). Then multiply this ratio by the meanstream velocity in the vertical to b
37、e sampled.7.3.1 The maximum transit rate determined in 7.3 should beused as a practice, the actual transit rate can be and in mostcases should be less than the maximum rate computed.8. Precision and Bias8.1 The transit-rate ratios given in this practice and deter-mined graphically and rounded to one
38、 significant figure.8.2 The precision of the collected sample is a function of theconditions encountered and the measurement techniques usedfor each measurement.9. Keywords9.1 sampling; sediment; surface-water; isokinetic samplingTABLE 1 Maximum Transit-Rate Ratios and Depths for Sampler/Container/N
39、ozzle ConfigurationsSamplerUSNozzleSize, in. (mm)NozzleColorContainerSizeMaximumDepth, ft (m)Max ratioRt/VmADH-4814 (6.35) Yellow Pint 9 (2.74) 0.4DH-48316 (4.76) Yellow Pint 15 (4.57) 0.4DH-75P316 (4.76) White Pint 15 (4.57) 0.4DH-75Q316 (4.76) White Quart 15 (4.57) 0.2DH-75H316 (4.76) White 2 L 15
40、 (4.57) 0.1DH-5918 (3.17) Red Pint 15 (4.57) 0.2DH-59316 (4.76) Red Pint 15 (4.57) 0.4DH-5914 (6.35) Red Pint 9 (2.74) 0.4DH-7618 (3.17) Red Quart 15 (4.57) 0.1DH-76316 (4.76) Red Quart 15 (4.57) 0.2DH-7614 (6.35) Red Quart 15 (4.57) 0.4DH-8118 (3.17) White Pint 15 (4.57) 0.2DH-81316 (4.76) White Pi
41、nt 15 (4.57) 0.4DH-8114 (6.35) White Pint 9 (2.74) 0.4DH-81516 (7.93) White Pint 6 (1.83) 0.4DH-8118 (3.17) White Quart 15 (4.57) 0.1DH-81316 (4.76) White Quart 15 (4.57) 0.2DH-8114 (6.35) White Quart 15 (4.57) 0.4DH-81516 (7.93) White Quart 10 (3.05) 0.4D-49/D-7418 (3.17) Green Pint 15 (4.57) 0.2D-
42、49/D-74316 (4.76) Green Pint 15 (4.57) 0.4D-49/D-7414 (6.35) Green Pint 9 (2.74) 0.4D-7418 (3.17) Green Quart 15 (4.57) 0.1D-74316 (4.76) Green Quart 15 (4.57) 0.2D-7414 (6.35) Green Quart 15 (4.57) 0.4DH-95316 (4.76) White 1 L 15 (4.57) 0.2DH-9514 (6.35) White 1 L 15 (4.57) 0.3DH-95516 (7.93) White
43、 1 L 13 (3.96) 0.4D-95316 (4.76) White 1 L 15 (4.57) 0.2D-9514 (6.35) White 1 L 15 (4.57) 0.3D-95516 (7.93) White 1 L 13 (3.96) 0.4D-96/D-96Al316 (4.76) White 3L - bag 110 (33.4) 0.4D-96/D-96Al14 (6.35) White 3L - bag 60 (18.3) 0.4D-96/D-96Al516 (7.93) White 3L - bag 39 (11.9) 0.4D-99316 (4.76) Whit
44、e 3L - bag 110 (33.4) 0.4D-9914 (6.35) White 3L - bag 60 (18.3) 0.4D-99516 (7.93) White 3L - bag 39 (11.9) 0.4D-99316 (4.76) White 6L - bag 220 (67.0) 0.4D-9914 (6.35) White 6L - bag 120 (36.6) 0.4D-99516 (7.93) White 6L - bag 78 (23.8) 0.4DH-2316 (4.76) White 1 L - bag 35 (11.0) 0.4DH-214 (6.35) Wh
45、ite 1 L - bag 20 (6.09) 0.4DH-2516 (7.93) White 1 L - bag 13 (3.96) 0.4ARt = transit rate; Vm = mean stream velocity in the vertical being sampled.BTo sample the full depth, samples must be collected in increments of no morethen 30 ft (9.144 m). See Footnote 3 for more details.3D6326 08 (2014)3ASTM
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