1、Designation:D 7256/D 7256M 08Standard Practice forMechanical Collection and Within-System Preparation of aGross Sample of Coal from Moving Streams1This standard is issued under the fixed designation D 7256/D 7256M;the number immediately following the designation indicates theyear of original adoptio
2、n or,in the case of revision,the year of last revision.A number in parentheses indicates the year of lastreapproval.A superscript epsilon(e)indicates an editorial change since the last revision or reapproval.INTRODUCTIONAnalysis data obtained from coal samples are used in establishing price,controll
3、ing mine andcleaning plant operations,allocating production costs,and determining 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
4、of the most difficult of materials to sample,varying in composition from noncombus-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
5、 by the sample,and the degree of precision required.This practice gives the overall requirements for the collection and within-system preparation of coalsamples through the use of mechanical sampling systems.The wide varieties of coal-handlingfacilities preclude the publication of detailed procedure
6、s for every sampling situation.The propercollection of the sample involves an understanding and consideration of the physical character of thecoal,the number and weight of increments,and the overall precision required.1.Scope1.1 This practice covers procedures for the mechanicalcollection of a sampl
7、e under Classification I-B-1 and I-B-2(Practice D 2234/D 2234M)and the within-system preparation(reduction and division)of gross samples utilizing variouscomponents of the mechanical sampling system.1.2 This practice describes mechanical sampling proceduresfor coals(1)by size and condition of prepar
8、ation(for example,mechanically cleaned coal or raw coal)and(2)by samplingcharacteristics.1.3 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard.Within the text theinch-pound units are shown in brackets.The values stated ineach system may not be exact eq
9、uivalents;therefore,use eachsystem independently of the other.Combining values from thetwo systems may result in nonconformance with the standard.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 standar
10、d 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:2D 121 Terminology of Coal and CokeD 2013 Practice for Preparing Coal Samples for AnalysisD 2234/D 2234M Practice for Collection of
11、 a Gross Sampleof CoalD 4702 Practice for Quality Management of MechanicalCoal Sampling SystemsD 6518 Practice for Bias Testing a Mechanical Coal Sam-pling SystemE 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE 456 Terminology Relating to Quality and Statistics3.Terminolog
12、y3.1 Definitions of Terms Specific to This StandardManyterms used in this practice may be found in TerminologiesD 121 and E 456 and in Practice E 177.3.1.1 activation intervalfor a falling-stream or cross-beltcutter,the time from the beginning of movement for taking anincrement,to the beginning of m
13、ovement for taking of the nextincrement.1This practice is under the jurisdiction of ASTM Committee D05 on Coal andCoke and is the direct responsibility of Subcommittee D05.23 on Sampling.Current edition approved April 15,2008.Published May 2008.Originallypublished in 2006.Last previous edition appro
14、ved in 2006 as D 7256/D 7256M-06a.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.1Copyright ASTM International,10
15、0 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.NOTICE:This standard has either been superseded and replaced by a new version or withdrawn.Contact ASTM International(www.astm.org)for the latest information3.1.2 cross-belt samplera single sampling machine orcomponent of
16、a mechanical sampling system designed toextract an increment directly from a conveyor belt surface bysweeping a sampling device(cutter)through the material onthe conveyor.3.1.3 falling-stream samplera single sampling machine orcomponent of a mechanical sampling system designed toextract an increment from a falling stream of coal at thedischarge end of a conveyor or chute by moving a samplingdevice(cutter)through the falling stream of material.3.1.4 mechanical sampling systema single machine orse
