1、Designation: D7430 12Standard Practice forMechanical Sampling of Coal1This standard is issued under the fixed designation D7430; 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 ind
2、icates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONAnalysis data obtained from coal samples are used in establishing price, controlling mine andcleaning plant operations, allocating production costs, and determi
3、ning plant or component efficiency.The task of obtaining a sample of reasonable weight to represent an entire lot presents a number ofproblems and emphasizes the necessity for using standard sampling procedures.Coal is one of the most difficult of materials to sample, varying in composition from non
4、combus-tible particles to those which can be burned completely, with all gradations in between. The task isfurther complicated by the use of the analytical results, the sampling equipment available, the quantityto be represented by the sample, and the degree of precision required.This practice gives
5、 the overall requirements for the collection and within-system preparation of coalsamples through the use of mechanical sampling systems utilizing falling stream, cross belt and augerdesigns. This practice also gives the overall requirements for the bias testing and quality managementof mechanical c
6、oal sampling systems. The wide varieties of coal-handling facilities preclude thepublication of detailed procedures for every sampling situation. The proper collection of the sampleinvolves an understanding and consideration of the physical character of the coal, the number andweight of increments,
7、and the overall precision required.1. Scope1.1 This practice is divided into 4 parts. These 4 partsrepresent the previous standards D7256/D7256M, D4916,D4702, and D6518. These 4 standards are the 4 that govern themechanical sampling of coal and have been combined into onedocument for the ease of ref
8、erence of the users of thesestandards.Part A1.2 Part AMechanical Collection and Within-SystemPreparation of a Gross Sample of Coal from MovingStreamsCovers procedures for the mechanical collection of asample under Classification I-B-1 and I-B-2 (Practice D2234/D2234M) and the within-system preparati
9、on (reduction anddivision) of gross samples utilizing various components of themechanical sampling system.1.2.1 Part A describes mechanical sampling procedures forcoals (1) by size and condition of preparation (for example,mechanically cleaned coal or raw coal), and (2) by samplingcharacteristics.1.
10、2.2 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith
11、the standard.Part B1.3 Part BMechanical Auger SamplingDescribesprocedures for the collection of an increment, partial sample, orgross sample of material using mechanical augers. Reductionand division of the material by mechanical equipment at theauger is also covered. Further manual or mechanical re
12、ductionor division of the material elsewhere shall be performed inaccordance with Practice D2013.1.3.1 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1This practice is under the jurisdiction of ASTM Committee D05 on Coal andCok
13、e and is the direct responsibility of Subcommittee D05.23 on Sampling.Current edition approved May 15, 2012. Published July 2012. Originallyapproved in 2008. Last previous edition approved 2011 as D743011A1.DOI:10.1520/D7430-12.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West
14、Conshohocken, PA 19428-2959, United States.Part C1.4 Part CQuality Management of Mechanical Coal Sam-pling SystemsIs applicable to the quality management ofcross-belt, falling stream, and auger sampling systems.1.4.1 Spacing of increments pertains to the kind of intervalbetween increments. Intervals
15、 can be defined in quantitativeterms, such as units of time or mass, or in terms of positionover the lot.1.4.2 Spacing of Increments for Cross-Belt and FallingStream SamplersCross-belt and falling stream type mechani-cal sampling systems take increments based on time, either atfixed time intervals o
16、r at random times during a fixed timestrata. Some falling stream samplers can take increments basedon equal mass of coal sampled as determined by scales. Thesections of this practice that pertain to cross-belt and fallingstream samplers describe procedures for only time-basedsampling systems. This t
17、ime-based inspection guideline willsatisfy most criteria for mass-based or combination mass-basedand time-based sampling systems. If there are items that are notcovered, the inspector should refer to the manufacturersliterature.1.4.3 Spacing of Increments for Auger SamplingThespacing of increments c
18、ollected by auger sampling systems isdefined in terms of position over the lot.1.4.4 It is essential that the inspector have the documenta-tion listed in Section 2 of this practice when conducting aninspection.1.4.5 The values stated in SI units are to be regarded asstandard. No other units of measu
19、rement are included in thisstandard.Part D1.5 Part DBias Testing of a Mechanical Coal SamplingSystemPresents sample collection and statistical evaluationprocedures for testing mechanical sampling systems (includingauger systems), subsystems, and individual system compo-nents for bias. It is the resp
20、onsibility of the user of this practiceto select the appropriate procedure for a specific samplingsituation.1.5.1 Part D does not purport to define an absolute bias. Biasdefined by this practice is the difference between the popula-tion mean of the mechanical sampler test results and theaccepted ref
21、erence value.1.5.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.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
22、 establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For a specifichazard statement, see section 16.1.2. Referenced Documents2.1 ASTM Standards:2D121 Terminology of Coal and CokeD2013 Practice for Preparing Coal Samples for Anal
23、ysisD2234/D2234M Practice for Collection of a Gross Sampleof CoalD4621 Guide for Quality Management in an OrganizationThat Samples or Tests Coal and Coke3D4702 Practice for Quality Management of MechanicalCoal Sampling Systems3D4749 Test Method for Performing the Sieve Analysis ofCoal and Designatin
24、g Coal SizeD4916 Practice for Mechanical Auger Sampling3D6518 Practice for Bias Testing a Mechanical Coal Sam-pling System3D7256/D7256M Practice for Mechanical Collection andWithin-System Preparation of a Gross Sample of Coalfrom Moving Streams3E105 Practice for Probability Sampling of MaterialsE122
25、 Practice for Calculating Sample Size to Estimate,With Specified Precision, the Average for a Characteristicof a Lot or ProcessE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE456 Terminology Relating to Quality and StatisticsE691 Practice for Conducting an Interlaboratory S
26、tudy toDetermine the Precision of a Test Method3. Terminology3.1 DefinitionsDefinitions applicable to this practice arelisted in Terminology D121.3.2 Definitions of Terms Specific to This Standard:3.2.1 accuracy, n(1) generally, a term used to indicate thereliability of a sample, a measurement, or a
27、n observation; (2)specifically, a measure of closeness of agreement between anexperimental result and the true value. An example is theobserved and true sulfur content of a coal consignment. Thismeasurement is affected by chance errors as well as by bias.3.2.2 activation interval, nfor a falling-str
28、eam or cross-belt cutter, the time from the beginning of movement for takingan increment, to the beginning of movement for taking of thenext increment.3.2.3 auger increment, nthe retained portion of one ex-traction operation of the auger.3.2.4 auger sampler, na mechanical device that extracts acolum
29、nar sample of coal from a railcar, truck, barge orstockpile and any associated sub-system or within-systemcomponents.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
30、 the standards Document Summary page onthe ASTM website.3Withdrawn. The last approved version of this historical standard is referencedon www.astm.org.D7430 1223.2.5 bias, nthe difference between the population meanof the mechanical sampler test results and the acceptedreference value.3.2.6 confiden
31、ce interval, na numeric interval with alower limit and a higher limit within which the true parametervalue is estimated to fall. The confidence interval percentageindicates the percentage of time the true value will fall withinthe interval if the procedure is continuously repeated.3.2.7 consignment,
32、 na discrete amount of coal, such as ashipment, a car load, a unit train, or a days production. Aconsignment may include more than one lot of coal and maycorrespond to a specific period of time, such as a samplingperiod or a billing period.3.2.8 correlation, na measure of the linear dependencebetwee
33、n paired system and reference measurements. Correla-tion frequently is expressed by the correlation coefficient,which can take a value from minus one (perfect negative linearrelationship) to plus one (perfect positive linear relationship).3.2.9 cross-belt sampler, na single sampling machine orcompon
34、ent of a mechanical sampling system designed toextract an increment directly from a conveyor belt surface bysweeping a sampling device (cutter) through the material onthe conveyor.3.2.10 delimitation error, na material error that occurswhen all the elements in a cross section of a coal stream do not
35、have an equal probability of being intercepted (captured) by thesampler cutter during increment collection.3.2.11 ellipsoidal region, nan area that is formed by planesections of ellipses that are defined by the values selected forthe largest tolerable bias of each coal characteristic used in thebias
36、 test. The region will be used to determine if the system isbiased.3.2.12 falling-stream sampler, na single sampling ma-chine or component of a mechanical sampling system designedto extract an increment from a falling stream of coal at thedischarge end of a conveyor or chute by moving a samplingdevi
37、ce (cutter) through the falling stream of material.3.2.13 Hotellings T2test, na statistical test that is used toevaluate multivariate data. It is the multivariate equivalent ofthe Students t-test.3.2.14 largest tolerable bias (LTB), nan interval whoseupper and lower bounds represent the limits of an
38、 acceptablebias.3.2.15 mechanical sampling system, na single machine orseries of interconnected machines whose purpose is to extractmechanically, or process (divide and reduce), or a combinationthereof, a sample of coal.3.2.16 paired data set, nsystem and reference valuesobserved on samples collecte
39、d and compared from the samebatch of material.3.2.17 precision, na term used to indicate the capability ofa person, an instrument, or a method to obtain reproducibleresults; specifically, a measure of the chance error as expressedby the variance, standard error, or a multiple of the standarderror (s
40、ee Practice E177).3.2.18 reference sample, na sample used in testing of amechanical sampling system which is comprised of one ormore increments collected from the test batch or lot of coal bythe stopped belt method as described in Practice D2234/D2234M.3.2.19 reject stream, nthe coal flow within a m
41、echanicalsampling system, which occurs at each stage of division, beforeand after reduction, and is not included in the system sample.3.2.20 save stream, nthe coal flow within a mechanicalsampling system which occurs at each stage of division, beforeand after reduction, and after the final stage of
42、divisionbecomes the system sample.3.2.21 statistical independence, ntwo sample values arestatistically independent if the occurrence of either one in noway affects the probability assigned to the occurrence of theother.3.2.22 surrogate sample, na sample, used in the evalua-tion of a mechanical sampl
43、ing system, which is comprised ofone or more increments collected from a coal stream within themechanical sampling system in accordance with PracticeD2234/D2234M, Conditions “A” or “B.” Such a sample maybe considered acceptable for evaluation of a mechanicalsampling systems components, excluding the
44、 primary cutter,when demonstrated to be equivalent to the reference sample.3.2.23 system sample, na sample collected from a testbatch or lot of coal by the mechanical sampling system beingtested for bias.3.2.24 unbiased sample (representative sample), nasample free of bias.3.2.25 Walsh averages, ngi
45、ven a series of observations(differences) x1, x2, . xn, the n (n + 1)/2 pair-wise averagesgiven by:xi 1 xj!/2, 1# i # j # n (1)3.2.25.1 DiscussionAs an example of Walsh averages,assume one has three observations (differences) designated asx1, x2, and x3. There are then a total of 3(4)/2 = 6 Walshave
46、rages. They are as follows: x1, x2, x3, (x1+x2)/2, (x1+x3)/2, and (x2+x3)/2.3.2.26 Wilcoxon Signed Rank Test, na non-parametricstatistical procedure for calculating the point estimate andconfidence interval for a sample drawn from a population withsymmetric distribution.3.2.27 within-system preparat
47、ion, nthe process of grosssample preparation carried out mechanically by sequentialcrushing (reduction) equipment and/or division equipment. Itmay be carried out by processing increments individually or bybatching increments together and processing them together asa group. In any case, within-system
48、 preparation is conducted ina manner to minimize moisture changes and without removingthe gross sample or its increments from the sampling system.D7430 123PART A MECHANICAL COLLECTION AND WITHIN-SYSTEM PREPARATION OF A GROSS SAMPLE OFCOAL FROM MOVING STREAMSOld Practice D7256/D7256M4. Summary of Pra
49、ctices4.1 The general-purpose sampling procedures are intendedto provide, in 19 of 20 cases, dry ash results that are within aninterval of 6110 of the average dry ash results that would beobtained in hypothetical repeated sampling.4.2 Special-purpose sampling procedures apply to the sam-pling of coal when other precision limits are required, or whenother constituents are used to specify precision, or for perfor-mance tests.4.3 For coals of known size and condition of preparation, atable (Table 1) is given for the determination of
