Tiêu chuẩn iso 13909 4 2016

INTERNATIONAL STANDARD ISO 13909-4 Second edition 2016-07-01 Hard coal and coke — Mechanical sampling — Part 4: Coal — Preparation of test samples Houille et coke — Échantillonnage mécanique — Partie 4: Charbon — Préparation des échantillons pour essai Reference number ISO 13909-4:2016(E) © ISO 2016 ISO 13909-4:2016(E) COPYRIGHT PROTECTED DOCUMENT © ISO 2016, Published in Switzerland All rights reserved Unless otherwise specified, no part o f this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission Permission can be requested from either ISO at the address below or ISO’s member body in the country o f the requester ISO copyright o ffice Ch de Blandonnet • CP 401 CH-1214 Vernier, Geneva, Switzerland Tel +41 22 749 01 11 Fax +41 22 749 09 47 copyright@iso.org www.iso.org ii © ISO 2016 – All rights reserved ISO 13909-4:2016(E) Contents Page Foreword v Introduction vi Scope Normative references Terms and definitions Precision of sample preparation Constitution of a sample 5.1 5.2 5.3 Division 6.1 6.2 6.3 10 Introduction Combination of increments 5.2.1 Time-basis sampling 5.2.2 Mass-basis sampling Combination of samples General Mechanical methods 10 6.2.1 General 10 6.2.2 Mass of cut 10 6.2.3 Interval between cuts 10 6.2.4 Division of individual increments 10 6.2.5 Division of samples 13 Manual methods 14 6.3.1 Ri ffle method 14 6.3.2 Flattened-heap method 15 6.3.3 Strip-mixing and splitting method 17 Reduction 19 7.1 7.2 General 19 Reduction mills 19 Mixing 19 Air-drying 19 Preparation o f samples for specific tests 20 10.1 10.2 Types o f test samples 20 Preparation o f samples for determination o f total moisture only 20 10.2.1 General 20 10.2.2 Storage 22 10.2.3 Sample reduction 22 10.2.4 Sample division 23 10.3 Preparation o f samples for general analysis only 23 10.3.1 General 23 10.3.2 Air-drying 23 10.3.3 Reduction and division 23 10.4 Common samples 24 10.4.1 General 24 10.4.2 Extraction o f moisture sample by mechanical division 25 10.4.3 Extraction o f moisture sample by manual method 25 10.5 Preparation o f size-analysis sample 26 10.6 Preparation of samples for other tests 27 11 12 Reserve sample 28 Design of equipment for preparation 28 12.1 Dividers 28 © ISO 2016 – All rights reserved iii ISO 13909-4:2016(E) 12.2 Design of cutters for falling-stream dividers 28 12.2.1 General 28 29 29 12.3.1 General 29 12.3.2 Design criteria 29 12.3.3 Abnormal operation 30 12.4 Provision for checking for precision 30 12.5 Provision for testing for bias 30 2 2 Cutter velo city Prep aratio n sys tems Bibliography 31 iv © ISO 2016 – All rights reserved ISO 13909-4:2016(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies) The work o f preparing International Standards is normally carried out through ISO technical committees Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters o f electrotechnical standardization The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part In particular the different approval criteria needed for the di fferent types o f ISO documents should be noted This document was dra fted in accordance with the editorial rules of the ISO/IEC Directives, Part (see www.iso.org/directives) Attention is drawn to the possibility that some o f the elements o f this document may be the subject o f patent rights ISO shall not be held responsible for identi fying any or all such patent rights Details o f any patent rights identified during the development o f the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents) Any trade name used in this document is in formation given for the convenience o f users and does not constitute an endorsement For an explanation on the meaning o f ISO specific terms and expressions related to formity assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers to Trade (TBT), see the following URL: Foreword — Supplementary in formation The committee responsible for this document is ISO/TC 27, Solid mineral fuels, Subcommittee SC 4, Sampling This second edition cancels and replaces the first edition (ISO 13909-4:2001), which has been technically revised ISO 13909 consists of the following parts, under the general title Hard coal and coke — Mechanical sampling: — Part 1: General introduction — Part 2: Coal — Sampling from moving streams — Part 3: Coal — Sampling from stationary lots — Part 4: Coal — Preparation of test samples — Part 5: Coke — Sampling from moving streams — Part 6: Coke — Preparation of test samples — Part 7: Methods for determining the precision of sampling, sample preparation and testing — Part 8: Methods of testing for bias © ISO 2016 – All rights reserved v ISO 13909-4:2016(E) Introduction T he obj e c tive o f s ample prep aration i s to prep are one or more te s t s a mple s for from the pri ma r y i ncrements s ub s e quent ana lys i s T he re qui s ite mas s a nd p ar ticle s i ze o f the te s t s a mple dep end on the te s t to b e carried out T he pro ce s s o f s ample prep aration may i nvolve s titution o f s ample s , re duc tion, d ivi s ion, m i xi ng a nd d r yi ng , or a l l or a combi nation o f the s e P ri mar y i nc rements may b e prep are d i nd ividua l ly as te s t s ample s or combi ne d to s titute s ample s either a s ta ken or a fter h avi ng b e en prep are d b y re duc tion and/or d ivi s ion S a mp le s may either b e prep a re d i nd ividua l ly a s te s t s a mp le s or combi ne d on a weighte d b a s i s to s titute a fu r ther s a mple When d i ffic u lty i n h and l i ng the co a l or co a l s b ei ng s ample d i s exp e c te d at a p ar tic u la r s tage i n s ample prep a ration, or i f there i s a l i kel i ho o d o f lo s i ng moi s tu re b y evap oration, it i s ne ce s s a r y to withd raw the s a mple or i nc rement and proceed off-line vi from the on-l i ne s ys tem at the s tage i m me d i ately prior to the p oi nt o f d i ffic u lty © ISO 2016 – All rights reserved INTERNATIONAL STANDARD ISO 13909-4:2016(E) Hard coal and coke — Mechanical sampling — Part 4: Coal — Preparation of test samples Scope T h i s p a r t o f I S O 9 de s c rib e s the prep aration o f s ample s o f co a l i nc rements to the prep aration o f s ample s for from the combi nation o f pri mar y s p e c i fic te s ts Normative references T he fol lowi ng i nd i s p en s able c u ments , i n whole or i n p ar t, are normatively re ference d i n th i s c u ment a nd are for its appl ic ation For date d re ference s , on ly the e d ition cite d appl ie s For u ndate d re ference s , the late s t e d ition o f the re ference d c u ment (i nclud i ng any amend ments) appl ie s ISO 589, Hard coal — Determination of total moisture ISO 3310-1, Test sieves — Technical requirements and testing — Part 1: Test sieves of metal wire cloth ISO 13909-1, Hard coal and coke — Mechanical sampling — Part 1: General introduction ISO 13909-2, Hard coal and coke — Mechanical sampling — Part 2: Coal — Sampling from moving streams ISO 13909-3, Hard coal and coke — Mechanical sampling — Part 3: Coal — Sampling from stationary lots ISO 13909-7, Hard coal and coke — Mechanical sampling — Part 7: Methods for determining the precision of sampling, sample preparation and testing ISO 13909-8, Hard coal and coke — Mechanical sampling — Part 8: Methods of testing for bias Terms and definitions For the pu r p o s e s o f th i s c u ment, the term s and defi nition s given i n I S O 9 -1 apply Precision of sample preparation From the equations given in ISO 13909-7, the estimated absolute value of the precision of the result Formula (1): f PL f ob ta i ne d or the lo t at the % fidence level, VI + VPT PL = n m , or s ampl i ng i s gi ven b y (1) where © ISO 2016 – All rights reserved ISO 13909-4:2016(E) PL is the estimated overall precision of sampling, sample preparation and testing for the lot at a 95 % confidence level, expressed as a percentage absolute; VI is the primary increment variance; VPT is the preparation and testing variance for both o ff-line and on-line systems; n is the number o f increments to be taken from a sub-lot; is the number of sub-lots in the lot The procedures given in this part of ISO 13909 are designed to achieve levels of VPT of 0,2 or less for both ash and moisture tests Better levels are expected when using mechanical dividers m For some preparation schemes, however, practical restrictions may prevent the preparation and testing variance being as low as this Under these circumstances, the user should decide whether to achieve the desired overall precision by improving the preparation scheme or by dividing the lot into a greater number of sub-lots The errors occurring in the various stages o f preparation and analysis, expressed in terms o f variance, may be checked by the method given in ISO 13909-7 Constitution of a sample 5.1 Introduction Primary increments shall be taken in accordance with the procedures specified in ISO 13909-2 and ISO 13909-3 Individual increments are usually combined to form a sample A single sample may be constituted by combination o f increments taken from a complete sub-lot or by combining increments taken from individual parts o f a sub-lot Under some circumstances, e.g size analysis or bias testing, the sample consists of a single increment which is prepared and tested Examples of the constitution of samples are shown in Figure The procedures for increment combination (5.2 ) may vary according to whether the primary increments were taken using a time-basis (5.2.1) or a mass-basis (5.2.2) sampling scheme Samples may also be prepared by the combination o f other samples (see 5.3) 5.2 5.2.1 Combination of increments Time-basis sampling The mass o f the primary increments shall be proportional to the flow rate at the time o f sampling The primary increments may be combined into a sample either directly as taken or a fter having been prepared individually to an appropriate stage by fixed-ratio division (see Clause 6) 5.2.2 Mass-basis sampling I f the primary increments are o f almost uni form mass (see note), they may be combined into a sample, either directly as taken or a fter having been prepared individually to an appropriate stage by fixed- ratio division (see Clause 6) NOTE Almost uni form mass has been achieved i f the coe fficient o f variation o f the increment masses is less than 20 % and there is no significant correlation between the flow rate at the time o f taking the increment and the mass of the increment (see ISO 13909-2:2016, Annex A) © ISO 2016 – All rights reserved ISO 13909-4:2016(E) I f the pri ma r y i nc rements a re no t o f a l mo s t u ni form mas s , they may on ly b e combi ne d i nto s ample s a fter h avi ng b e en d ivide d i nd ividua l ly b y fi xe d-mas s d ivi s ion (s e e Clause 6) a) Example b) Example Figure — Examples of the constitution of samples 5.3 Combination of samples When combi n i ng s ample s , the mas s o f the i nd ividua l s a mple s sha l l b e d i re c tly prop or tiona l to the ma s s o f the co a l for from wh ich they were ta ken i n order to ob tai n a weighte d me a n o f the qua l ity charac teri s tic the s ub -lo t P rior to combi nation, d ivi s ion s l l b e by fi xe d-ratio d ivi s ion (s e e Clause 6) Division 6.1 General Division can be — on-l i ne me ch an ic a l ly, or — o ff-l i ne me cha nic a l ly or manua l ly Whenever possible, mechanical methods are preferred to manual methods to minimize human error Examples of dividers are shown in Figure © ISO 2016 – All rights reserved ISO 13909-4:2016(E) Mechanical dividers are designed to extract one or more parts o f the coal in a number o f cuts o f relatively small mass When the smallest mass of the divided sample that can be obtained in one pass through the divider is greater than that required further passes through the same divider or subsequent passes through further dividers may be necessary I f coal does not run freely through a sample divider it may be necessary to air-dry the sample as described in Clause 10 before sample division is undertaken Manual division is normally applied when mechanical methods would result in loss o f integrity, e.g loss o f moisture or size degradation Manual methods may themselves result in bias, particularly i f the mass of coal to be divided is large a) Rotating disc type Key b) Rotating cone type Key feed reject divided sample The material from a mixing container is fed by scrapers to the centre of the dividing disc From there it is discharged over the range of the disc through special clearing arms The sample falls through adjustable slots into chutes; the reject is carried away through a feed rotating cone adjustable slot divided sample reject A stream o f coal is allowed to fall onto a rotating cone; the adjustable slot with lips in the cone allows the stream to fall directly onto the sample receiver for part o f each revolution cleaning conduit The whole interior space is cleaned by scrapers Figure — Examples of dividers © ISO 2016 – All rights reserved ISO 13909-4:2016(E) Key increment sampling frame 18 © ISO 2016 – All rights reserved ISO 13909-4:2016(E) end plates (“book ends”) Figure — Strip-mixing and splitting method Reduction 7.1 General Mechanical equipment shall be used to reduce the particle size, but manual crushing is permitted for the bre a kage o f large materia l to me e t the ma xi mu m fe e d s i ze accep table to the fi rs t- s tage m i l l T he te s t s ample s l l b e re duce d to the p ar ticle s i z e s p e c i fie d i n the relevant te s t me tho d T he m i l l s e tti ngs shou ld b e che cke d re gu l arly b y s ievi ng and de term i n i ng the nom i na l top s i z e pro duce d b y e ach m i l l 7.2 Reduction mills The particle size produced depends on the speed of the mill and its design Mills shall be designed such that the required particle size of the reduced sample can be achieved without using extreme settings Loss of sample or retention of material from previous samples, which might contaminate succeeding samples, shall be minimized Heating of the sample and airstream effects shall be f determination, and coking tests There shall be no contact between the metal surfaces in order to avoid localized heating of the sample m i n i m i z e d , p a r tic u l arly where the s ample i s to b e u s e d To ta l ly clo s e d , h igh- s p e e d (>2 H z) ball mills or to ta l moi s tu re de term i nation, c a lori fic va lue sha l l no t b e u s e d T he p ar ticle s i z e o f the output i s i n fluence d b y the h ard ne s s o f the co a l, but the e ffe c t wi l l dep end on the s p e e d range For cer tai n te s ts , s p e c i fie d s i z e grad i ngs are re qui re d and the typ e o f m i l l s l l b e cho s en to en s u re that the required size is obtained Mixing M i xi ng i s no t p o s s ible where s ample s or i nc rements are flowi ng th rough a ny form o f prep aration s ys tem and i s there fore re s tric te d to o ff-l i ne prep aration I n the or y, thorough m i xi ng o f a s ample prior to its d ivi s ion re duce s errors due to s ample prep aration I n prac tice, th i s i s no t e a s y to ach ieve a nd s ome me tho d s o f hand m i xi ng , e g form i ng and re form i ng i nto a ic a l pi le, ca n have the opp o s ite e ffe c t le ad i ng to i ncre as e d s e gregation M i xi ng may a l s o re s u lt i n loss of moisture 6.3.1 divider [see Figure c)] three times, reuniting the parts after each pass If mechanical sample dividers f required precision O ne me tho d th at c an b e u s e d i s to p ou r the s ample th rough a ri ffle ( are u s e d i n the cours e o NO TE ) or a conta i ner-typ e s a mp le prep aration, a n add itiona l m i xi ng s tep i s no t norma l ly ne ce s s ar y to me e t the M e ch a n ic a l m i xi ng m ay b e u s e fu l at the fi n a l s tage o f prep a ration o f te s t s a mp le s Air-drying T he s ample i s s pre ad i n a th i n l ayer and a l lowe d to attai n e qu i l ibrium with the atmo s phere at ambient temperatures T he co a l layer s l l no t e xce e d a th ickne s s o f , ti me s the nom i na l top s i z e o f the co a l or a lo ad i ng o f g/cm , whichever is the greater © ISO 2016 – All rights reserved 19 ISO 13909-4:2016(E) The recommended times to attain equilibrium at different ambient temperatures up to 40 °C are given in Table The times recommended in Table f f f oxidation wi l l norma l ly b e s u fic ient, but i ne ce s s ar y a longer d r yi ng ti me may b e u s e d, provide d that any i nc re a s e i s kep t to a m i n i mu m, e s p e c ia l ly or co a l s s u s cep tible to Table — Recommended drying times for air-drying Drying temperature Drying time °C 20 30 40 h P re ferab ly no t to e xce e d P re ferab ly no t to e xce e d P re ferab ly no t to e xce e d D r yi ng temp erature s ab ove ° C s l l no t b e u s e d on s ample s l i kely to b e s u s cep tible to oxidation or i f the s ample i s to b e u s e d for a ny o f the fol lowi ng te s ts: a) c a lori fic va lue; b) c a ki ng prop er tie s; c) s wel l i ng prop er tie s; d) r- d r yi ng as p ar t o f a de term i nation o f to ta l moi s tu re For d r yi ng temp eratu re s ab ove norma l ambient, a c abi ne t or oven with appropri ate r- cha nge faci l itie s sha l l b e u s e d I f d r yi ng h as b e en c arrie d out at s uch temp eratu re s , the s ample s l l b e co ole d u nti l moisture equilibrium at normal ambient temperature is achieved before reweighing The cooling period f f has been dried at 40 °C re qu i re d wi l l dep end on the d r yi ng temp eratu re For e xample, h i s norma l ly s u fic ient i P r e p a r a t i o n o f s a m p l e s f o r s p e c i f i c t e s the s ample t s 10.1 Types of test samples T he fol lowi ng typ e s o f te s t s a mple may b e prep are d: a) s ample s for de term i nation o f to ta l moi s ture on ly; b) s ample s for genera l ana lys i s on ly (i e no t to b e u s e d c) com mon s ample s d) s ample s for s i z e a na lys i s; e) s ample s for o ther te s ts , e g de term i nation o f H ardgrove Gri ndabi l ity I ndex for for de term i n i ng to ta l moi s tu re) ; b o th to ta l moi s tu re de term i nation and for genera l a na lys i s; The methods of preparation will depend on the purpose for which the original sample was collected 10.2 Preparation of samples for determination of total moisture only 10.2.1 General The test sample for the determination of total moisture content shall be prepared to meet the requirements of ISO 589 f f f f ISO 589:1981 1) , 8.2 I r- dr yi ng i s p er ormed at any s tage o recorded and included in the calculation o 1) 20 prep aration, the percentage lo s s in mas s shal l b e total moi s ture as s p eci fied in This is a withdrawn I nternatio nal S tandard and has b een rep laced by I S O : 0 © ISO 2016 – All rights reserved ISO 909-4: 01 6(E) A major problem with the preparation o f test samples for the determination o f moisture content is the risk of bias due to inadvertent loss of moisture The amount of this loss is dependent on such factors as the effectiveness of the sealing of the sample containers, the level of moisture content of the sample, the ambient conditions, the type o f coal and the reduction and division equipment and procedures used A sample may be prepared as a test sample with or without preliminary air-drying, but the pre ferred procedure is to divide the uncrushed sample to a mass not less than that given in Table and air-dry it The sample is then crushed and divided to the required test sample state Preliminary air-drying may be necessary in order to minimize moisture loss in any subsequent reduction/division stages Reduction/division shall only be carried out prior to air-drying i f it does not result in moisture bias If the coal is so wet that water separates from the coal in the sample container, the whole of the sample and the container shall be air-dried and the loss in mass recorded and included in the calculation of total moisture content as specified in ISO 589 I f the mass o f the uncrushed sample is so large that air-drying is impracticable, the samples shall be crushed and divided be fore air-drying Crushing shall be kept to the minimum necessary to allow division to a manageable mass The absence of bias due to these procedures shall be checked using the procedures given in ISO 13909-8 If the particle size of the sample is so large that the mass given in Table makes its air-drying impracticable, the sample shall be crushed and divided be fore air-drying Crushing shall be kept to the minimum necessary to allow division to a manageable mass The preparation process shall be tested for bias using the procedures given in ISO 13909-8, by comparison with the method o f drying samples without reduction An example of a scheme for the preparation of a sample for a two-stage moisture test is given in Figure © ISO 2016 – All rights reserved 21 ISO 13909-4:2016(E) Note Reduce to p article s ize s p ecified D ivide to mas s s p ecified Figure — Example of a two-stage moisture-test sample preparation 10.2.2 Storage Precautions shall be taken to minimize changes of moisture content during preparation due to the use of unsuitable containers and to evaporation during handling All samples for moisture determination shall be kept in moisture-tight containers in a cool place, under cover, before and during preparation as wel l as du ri ng any i nter va l b e twe en s tep s o f s ample prep a ration If excessive standing time causes bias, increase the number of sub-lots to overcome these problems (see ISO 13909-2 or ISO 13909-3) Weigh the s ample s s tore d for moi s ture de term i nation b e fore s torage to a l low de term i nation o f any moisture change that takes place during storage 10.2.3 Sample reduction C are s l l b e ta ken to m i n i m i z e ch ange s i n moi s tu re content du ri ng re duc tion, b y u s i ng e qu ipment i n wh ich there i s no appre c iable he ati ng a nd b y re duci ng to a m i n i mu m the flow o f a i r th rough the m i l l If such changes cannot be minimized, then the uncrushed sample shall be air-dried prior to crushing according to ISO 589 22 © ISO 2016 – All rights reserved ISO 13909-4:2016(E) 10.2.4 Sample division When carrying out sample division prior to air-drying o f a sample or increment, care shall be taken to minimize changes o f moisture content To this end, all divisions shall be carried out as quickly as possible and mechanically operated dividers with limited ingress o f air shall be used NOTE For coals which are too moist to flow through a sample divider and for which it is also impossible to air-dry the entire sample, it may be necessary to divide the sample by collecting increments from a flattenedheap (6.3.2 ) or by strip-mixing and splitting (6.3.3) This divided sample is then air-dried 10.3 Preparation of samples for general analysis only 10.3.1 General The objective o f general-analysis sample preparation is to prepare a test sample which will pass a sieve with 212 µm nominal size openings conforming to the requirements of ISO 3310-1 The mass of the test sample depends on the analysis required, but is between 60 g and 300 g Sample preparation is normally carried out in two or three stages, each consisting o f drying (i f necessary), size reduction, mixing (i f necessary) and division 10.3.2 Air-drying Air-drying in connection with preparation for general analysis is only carried out to ensure that the coals can pass freely through the equipment Loss o f moisture during the preparation is o f no relevance and consequently it is not necessary to measure the loss o f mass Air-drying may be carried out at any stage, provided that it does not a ffect the quality o f the sample For example, i f the sample is to be used for the determination o f calorific value, coking or swelling properties, the maximum drying temperature shall be 40 °C I f drying can be avoided during the first stage o f preparation, the procedure can be simplified 10.3.3 Reduction and division Reduction and/or division of increments takes place in accordance with the requirements of Clause and Clause down to a nominal top size of 2,8 mm prior to their combination to form samples NOTE I f the coal is wet, it may not be possible to crush it so finely because o f blocking o f chutes, dividers, mills, feeders, etc I f possible, reduce the coal to a nominal top size o f 2,8 mm in the first stage in order to minimize the mass of sample retained for the next stage as well as to minimize errors due to sample division NOTE It may be necessary to use a stamp or a maul to break oversize particles to the maximum feed size o f the crushing device If the original nominal top size of the coal is too large, or if the coal is too wet, an intermediate stage may be required In this case, the retained sample from the first stage shall be passed through a second mill to reduce the nominal top size to 2,8 mm The sample shall be divided by means o f a suitable sample divider to the mass corresponding to the nominal top size in accordance with Table The sample is reduced and divided in one or two further stages to the nominal top size and mass required for the test sample and it is finally thoroughly mixed Mechanical or manual division may be used, the former being pre ferred For mechanical division, a suitable divider to give 60 g to 300 g o f 212 µm coal is required For manual division, a ri ffle may be used, or the sample spread out and 60 g to 300 g taken by hand in not less than 20 increments from various parts o f the flattened heap © ISO 2016 – All rights reserved 23 ISO 13909-4:2016(E) An example o f a scheme for preparation o f a general-analysis test sample is given in Figure Note Reduce to particle size specified Divide to mass specified Figure — Example of preparation of a general-analysis test sample 10.4 Common samples 10.4.1 General In some circumstances, it is more convenient to take a common sample for both moisture determination and general analysis It is pre ferable to extract the moisture sample by using a mechanically operated divider in accordance with 10.4.2 24 © ISO 2016 – All rights reserved ISO 13909-4:2016(E) I f the common sample is visibly wet and it is impossible to air-dry the entire sample, use a manual method in accordance with 10.4.3 Examples o f schemes for the preparation o f separate test samples for moisture and for general analysis from a common sample are given in Figure Sometimes a single test sample may be prepared for both moisture determination and general analysis As a result of the extraction, the common sample has been divided into two parts, one for preparation o f the moisture test sample and one for preparation o f the general-analysis test sample Each part shall fulfil the requirements for minimum mass specified in Table and further treatment of the parts shall be in accordance with 10.2 and 10.3 respectively 10.4.2 Extraction of moisture sample by mechanical division The extraction o f the moisture sample may be carried out at any convenient stage o f the preparation procedure consistent with the requirements of 10.2.3 Prior to extraction, the sample shall be treated in accordance with 10.2 in order to avoid any inadvertent loss of moisture I f air-drying is part of the preparation prior to extraction, the loss o f mass during the drying shall be measured, recorded and included in the calculation o f total moisture content as specified in ISO 589 10.4.3 Extraction of moisture sample by manual method Extract a moisture sample by collecting increments by the flattened-heap method (6.3.2 ) or by the strip mixing and splitting method (6.3.3) Avoid further treatment o f the moisture sample be fore air-drying to reduce the risk o f bias in the moisture determination Further treatment a fter air-drying shall be carried out as described in 10.2 The residual coal a fter extraction constitutes the sample from which the general-analysis test sample is prepared, and is treated as described in 10.3 © ISO 2016 – All rights reserved 25 ISO 13909-4:2016(E) Note Reduce to particle size specified Divide to mass specified Figure — Examples of preparation of test samples from a common sample for moisture determination and general analysis 10.5 Preparation of size-analysis sample I f the mass o f the size-analysis sample is more than twice that given in Table for the appropriate nominal top size, it may be divided to a mass not less than that given in Table 1, provided that the requirements for division (see Clause 6) are satisfied Also, some samples will need to be air-dried as described in Clause 10 before sample division and size analysis is undertaken During division, precautions shall be taken to avoid breakage An example of a scheme for the preparation of test samples for size analysis is given in Figure 10 If the nominal top size of the coal is greater than one-third of the cutting aperture of the sample divider, oversize material may be removed by sieving out and the whole o f this oversize portion subjected to 26 © ISO 2016 – All rights reserved ISO 13909-4:2016(E) Table for the results combined with those from the oversized coal, weighted according to their relative proportions in the original sample s i ze a na lys i s T he u nders i z e co a l s hou ld b e d ivide d to a mas s no t le s s than that given i n appropri ate nom i na l top s i z e T he d ivide d s ample shou ld then b e s ubj e c te d to s i z e a na lys i s and the Note Figure 10 — Example of preparation of samples for size analysis and/or other tests 10.6 Preparation of samples for other tests Preparation shall be as described in 10.3 or 10.4, except that the nominal top size and mass of the test sample shall be as required in the relevant test method An example of a scheme for the preparation of such test samples is given in Figure 10 © ISO 2016 – All rights reserved 27 ISO 13909-4:2016(E) 11 Reserve sample I f a re s er ve s a mple i s ta ken for e xam i nation i n the event o f a d i s pute or i n c as e the re s u lts o f the fi rs t te s ts are lo s t or i nva l id, it s l l b e col le c te d at the s ame ti me a nd prep are d i n the s ame way as the ord i nar y s ample It is recommended that the reserve sample be divided as little as possible and no further than to the maximum mass which it is still practicable to store It should not be reduced further than to the nominal top size consistent with the mass given in Table 12 Design of equipment for preparation 12.1 Dividers Division devices shall a) b) have s u fficient c ap acity to re tai n comple tely or to p a s s the enti re s ample without lo s s or s pi l l age, no t i ntro duce bia s , moisture, NO TE for example b y s ele c tive col le c tion (or rej e c tion) b y p ar ticle s i z e or b y lo s s o f I n o rder to avo id mo i s tu re lo s s , i n s o me c i rc u m s ta nce s to ta l l y enclo s e d d ividers m ay b e ne ce s s a r y c) use a method of feeding which minimizes the segregation of the coal, d) provide a control le d u n i form flow to the e quipment at e ach s tage o f d ivi s ion, and e) in the case of on-line mechanical dividers, have cutting frequencies which are not in phase with preceding equipment I t i s de s i rable that the e qu ipment b e able to provide a random s tar t with i n the fi rs t s ampl i ng i nter va l for the fi rs t c ut on e ach mas s o f co a l to b e d ivide d i n order to m i n i m i z e bia s I t i s e s s entia l that the divider be set in motion before feeding of coal commences 12.2 Design of cutters for falling-stream dividers 12.2.1 General A cutter intended for dividing a falling stream of coal shall be designed to meet the following 12.1: re qu i rements i n add ition to tho s e s p e ci fie d i n a) b) the c utter sha l l ta ke a comple te cro s s - s e c tion o f the s tre a m; the le ad i ng and trai l i ng c utti ng e dge s sha l l de s crib e the s ame pla ne or the s ame c yl i nd ric a l s u r face, a s appropri ate, a nd th i s p lane or s u r face sha l l b e norma l to the me an traj e c tor y o f the s tre am; c) the c utter s l l travel th rough the co a l s tre am at a un i form velo c ity, i e the velo city s l l no t 12.2.2 d) the design of the cutter aperture shall be such that all parts of the stream are exposed to the deviate b y more th an % ap er tu re e) for from the pre s ele c te d re ference velo c ity at a ny p oi nt (s e e ); the s a me leng th o f ti me; the e ffe c tive cap ac ity o f the s ampl i ng c utter sh a l l b e s uch that, at the exp e c te d ma xi mu m flow rate of the coal stream, it will retain or pass the whole of the increment without loss or spillage and without any p ar t o f the c utter b e com i ng blo cke d or re s tric te d b y materi a l a l re ady col le c te d; f) the width of the cutter aperture shall be at least three times the nominal top size of the coal If the c utter ap er tu re i s tap ere d , as i s the c a s e with s ome s wi ng- arm typ e s a mplers , the m i n i mu m width re qui rement sh a l l apply to the narrow end 28 © ISO 2016 – All rights reserved ISO 13909-4:2016(E) 12.2.2 Cutter velocity T he width o f the c utter ap er tu re and the c utter velo city a re i mp or tant p arame ters to b e s idere d when de s ign i ng a s ample c utter Ta ken j oi ntly with the velo c ity o f the co a l s tre am, the s e p arame ters will determine the effective width of the cutter aperture, i.e the width of that part of the aperture into wh ich the s tre am o f co a l c an flow u n i mp e de d For falling-stream cutters, experimental work on ores[2] has shown that for sampling heterogeneous f introduced when the cutter speed exceeds 0,6 m/s or the cutter aperture is less than three times the nominal top size of the material materi a l s tre a m s o low b elt lo ad i ng , where p ar ticle s i ze d i s tribution i s ver y narrow, bia s may b e T he ratio o f the e ffe c tive c utter width to the nom i na l top s i z e o f the co a l wi l l de c i s ively i n fluence the c ap abi l ity o f the c utter to ta ke u nbia s e d i nc rements , s i nce the gre ater th i s ratio i s , the le s s wi l l the tendenc y b e to s ele c tively rej e c t the l arger p a r ticle s On the basis of this evidence, cutters that have a cutter aperture width, b, equal to three times the nominal top size of the coal shall not exceed a cutter speed of 0,6 m/s For cutters where the aperture is in excess of three times the nominal top size, the maximum cutter speed, vC , can be increased in accordance with Formula (3) f , s ubj e c t to a ma xi mu m s p e e d o  b   3d  v C = 0,  + where b , m/s: (3)  i s the c utter ap er tu re width , i n m i l l i me tre s; is the nominal top size of the coal, in millimetres Irrespective of cutter speed and aperture, the cutter shall be shown to be capable of collecting unbiased increments d 12.3 Preparation systems 12.3.1 General I de a l ly, the me chan ic a l s ys tem sha l l b e de s igne d at the s ame ti me a s the co a l-h and l i ng plant I n that event, the ma i n pl ant c a n b e de s igne d to accom mo date the me cha nic a l s ampl i ng s ys tem a nd the b e s t prac tic able cond ition s for its op eration c an b e en s u re d However, even i f the s ys tem i s adde d to an exi s ti ng pl ant, it i s e s s enti a l that engi ne eri ng exp e d ienc y i s no t a l lowe d to c au s e any cond ition wh ich wou ld ma ke the s ys tem bi as e d T he de s ign o f the s ys tem for s ampl i ng a nd s ample prep aration s l l b e relate d to the typ e s o f co a l to b e hand le d, the qua l ity charac teri s tics to b e de term i ne d a nd the ma xi mum numb er, ma s s and of increments anticipated as discussed in Clause fre quenc y 12.3.2 Design criteria T he s ys tem s l l b e de s igne d and engi ne ere d i n s uch a way that a) it i s c ap able o f prep ari ng s a mple s i n an unbia s e d man ner, a nd c an ma i nta i n th i s c ap abi l ity under a l l cond ition s o f s a mp l i ng that a re s tipu late d i n the relevant s p e c i fic ation s and without ne ce s s itati ng interruption of preparation for cleaning or maintenance, b) due s ideration i s given to the s a fe ty o f the op eration from the i n iti a l s tage s o f de s ign a nd s truc tion and a l l s a fe ty co de s appl ic able at the s ite where the e qu ipment i s to b e i n s ta l le d are respected, © ISO 2016 – All rights reserved 29 ISO 13909-4:2016(E) c) it is su fficiently robust to withstand adverse operating conditions, d) the system as a whole, including dividers, chutes, hoppers, feeders, crushers and other equipment, can operate in a manner that facilitates material flow and minimizes the need for cleaning to prevent and clear blockages, e) any contamination o f the sample, e.g by material retained from an earlier sample, is avoided, f) degradation of the constituent particles is minimized if a sample is taken for particle-size determination, and g) any change in moisture content, chemical or physical properties, or loss o f fine coal (e.g caused by excessive air flow through the equipment) is minimized 12.3.3 Abnormal operation A mechanical system shall be designed to ensure a su fficient degree o f operating flexibility such that even under abnormal conditions, for instance when part or parts o f the system are disabled due to breakdown or because they have become choked, the remainder o f the system (assisted i f necessary by suitable o ff-line preparation) is still capable o f per forming satis factorily 12.4 Provision for checking for precision The sampling system shall be capable o f either processing the increments to constitute duplicate samples by combining the increments alternately, or processing the increments to constitute replicate samples by combining the increments in rotation The latter capability should pre ferably be available when sampling coals o f unknown variability Procedures for checking precision by means o f duplicate and replicate sampling are described in ISO 13909-7 12.5 Provision for testing for bias To allow bias tests to be carried out in accordance with ISO 13909-8, provision shall be made for reference samples to be taken Adequate access shall be provided to allow correct sampling from the coal stream within the system to facilitate dynamic testing o f subsystems and components (see ISO 13909-8) 30 © ISO 2016 – All rights reserved ISO 13909-4:2016(E) Bibliography [1] HOLMES R.J Assessment of Minimum Sample Mass for Coal, Mineral Engineering Communication, [2] GY f Publishing, Amsterdam 1992 M I E/C , C S I RO D ivi s ion o f M i nera l E ngi ne eri ng , M ay 19 7, P M S ampl i ng © ISO 2016 – All rights reserved o H e tero gene ou s a nd D ynam ic M ateri a l S ys tem s , E l s evier S c ienti fic 31 ISO 909-4: 01 6(E) ICS  73.040 Price based on 31 pages © ISO 2016 – All rights reserved