1、 g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58ICS 73.040Hard coal Sampling of slurriesBRITISH STANDARDBS ISO 20904:2006BS ISO 20904:2006This Brit
2、ish Standard was published under the authority of the Standards Policy and Strategy Committee on 30 November 2006 BSI 2006ISBN 0 580 49617 1Amendments issued since publicationAmd. No. Date Commentscontract. Users are responsible for its correct application.Compliance with a British Standard cannot c
3、onfer immunity from legal obligations.National forewordThis British Standard was published by BSI. It is the UK implementation of ISO 20904:2006.The UK participation in its preparation was entrusted to Technical Committee PTI/16, Solid mineral fuels.A list of organizations represented on PTI/16 can
4、be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a Reference numberISO 20904:2006(E)INTERNATIONAL STANDARD ISO20904First edition2006-10-01Hard coal Sampling of slurries Houille chantillonnage des schlamms BS ISO 20904:2006ii iiiCont
5、ents Page Foreword. v 1 Scope . 1 2 Normative references . 1 3 Definitions . 1 4 Principles of sampling slurries . 2 4.1 General. 2 4.2 Sampling errors 3 4.3 Sampling and overall variance 6 5 Sampling schemes . 7 6 Minimization of bias and unbiased increment mass. 13 6.1 Minimizing bias . 13 6.2 Vol
6、ume of increment for falling stream samplers to avoid bias 14 6.3 Volume of increment for manual sampling to avoid bias. 14 7 Precision of sampling and determination of increment variance 15 7.1 Overall precision. 15 7.2 Primary increment variance. 15 7.3 Preparation and testing variance 16 8 Number
7、 of sub-lots and number of increments per sub-lot. 16 9 Minimum mass of solids in lot and sub-lot samples 17 9.1 General. 17 9.2 Minimum mass of solids in lot samples. 17 9.3 Minimum mass of solids in sub-lot samples .17 9.4 Minimum mass of solids in lot and sub-lot samples after size reduction 17 1
8、0 Time-basis sampling 18 10.1 General. 18 10.2 Sampling interval 18 10.3 Cutters . 18 10.4 Taking of increments 18 10.5 Constitution of lot or sub-lot samples 19 10.6 Division of increments and sub-lot samples . 19 10.7 Division of lot samples. 19 10.8 Number of cuts for division . 19 11 Stratified
9、random sampling within fixed time intervals 19 12 Mechanical sampling from moving streams 20 12.1 General. 20 12.2 Design of the sampling system. 20 12.3 Slurry sample cutters . 22 12.4 Mass of solids in increments. 23 12.5 Number of primary increments . 23 12.6 Routine checking 23 13 Manual samplin
10、g from moving streams. 23 13.1 General. 23 13.2 Choosing the sampling location . 23 13.3 Sampling implements. 24 13.4 Mass of solids in increments. 24 13.5 Number of primary increments . 24 BS ISO 20904:2006iv 13.6 Sampling procedures . 25 14 Sampling of stationary slurries . 25 15 Sample preparatio
11、n procedures 25 15.1 General . 25 15.2 Reduction mills . 25 15.3 Sample division. 25 15.4 Chemical analysis samples 25 15.5 Physical test samples. 26 16 Packing and marking of samples 26 Annex A (informative) Examples of correct slurry devices 27 Annex B (informative) Examples of incorrect slurry sa
12、mpling devices 30 Annex C (normative) Manual sampling implements. 34 Bibliography . 35 BS ISO 20904:2006vForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is norm
13、ally 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 t
14、he work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare
15、 International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some
16、 of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 20904 was prepared by Technical Committee ISO/TC 27, Solid mineral fuels, Subcommittee SC 4, Sampling. BS ISO 20904:2006blank1Hard coal Sampling
17、 of slurries 1 Scope This International Standard sets out the basic methods for sampling fine coal, coal rejects or tailings of nominal top size 4 mm that is mixed with water to form a slurry. At very high ratios of fine solids to water when the material assumes a soft plastic form, the mixture is c
18、orrectly termed a paste. Sampling of pastes is not covered in this International Standard. The procedures described in this International Standard primarily apply to sampling of coal that is transported in moving streams as a slurry. These streams can fall freely or be confined in pipes, launders, c
19、hutes, spirals or similar channels. Sampling of slurries in stationary situations, such as a settled or even a well-stirred slurry in a tank, holding vessel or dam, is not recommended and is not covered in this International Standard. This International Standard describes procedures that are designe
20、d to provide samples representative of the slurry solids and particle size distribution of the slurry under examination. After draining the slurry sample of fluid and measuring the fluid volume, damp samples of the contained solids in the slurry are available for drying (if required) and measurement
21、 of one or more characteristics in an unbiased manner and with a known degree of precision. The characteristics are measured by chemical analysis or physical testing or both. The sampling methods described are applicable to slurries that require inspection to verify compliance with product specifica
22、tions, determination of the value of a characteristic as a basis for settlement between trading partners or estimation of a set of average characteristics and variances that describes a system or procedure. Provided flow rates are not too high, the reference method against which other sampling proce
23、dures are compared is one where the entire stream is diverted into a vessel for a specified time or volume interval. This method corresponds to the stopped-belt method described in ISO 13909-2. 2 Normative references The following referenced documents are indispensable for the application of this do
24、cument. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 1213-1, Solid mineral fuels Vocabulary Part 1: Terms relating to coal preparation ISO 1213-2, Solid mineral fuels Vocabulary Par
25、t 2: Terms relating to sampling, testing and analysis ISO 13909-1, Hard coal and coke Mechanical sampling Part 1: General introduction ISO 13909-4, Hard coal and coke Mechanical sampling Part 4: Coal Preparation of test samples ISO 13909-8, Hard coal and coke Mechanical sampling Part 8: Methods of t
26、esting for bias 3 Definitions For the purpose of this document, the definitions given in ISO 13909-1, ISO 1213-1 and ISO 1213-2 apply. BS ISO 20904:20062 4 Principles of sampling slurries 4.1 General For the purposes of this International Standard, a slurry is defined as fine coal, coal rejects or t
27、ailings of nominal top size 4 mm that is mixed with water, which is frequently used as a convenient form to transport coal, rejects or tailings though plant circuits by means of pumps and pipelines and under gravity in launders or chutes or through long distances in slurry pipelines. Tailings from w
28、et plants are also discharged as a slurry through pipelines to the tailings dam. In many of these operations, collection of increments at selected sample points is required for evaluation of the coal or rejects in the slurry. A lot or sub-lot sample is constituted from a set of unbiased primary incr
29、ements from a lot or sub-lot. The sample container is weighed immediately after collection and combination of increments to avoid water loss by evaporation or spillage. Weighing is necessary to determine the mass percentage of solids in the lot or sub-lot sample. The lot or sub-lot sample can then b
30、e filtered, dried and weighed. Alternatively, the lot or sub-lot sample may be sealed in plastic bags after filtering for transport and drying at a later stage. Except for samples for which their characteristics are determined directly on the slurry, test samples are prepared from lot or sub-lot sam
31、ples after filtering and drying. Test portions may then be taken from the test sample and analysed using an appropriate and properly calibrated analytical method or test procedure under prescribed conditions. The objective of the measurement chain is to determine the characteristic of interest in an
32、 unbiased manner with an acceptable and affordable degree of precision. The general sampling theory, which is based on the additive property of variances, can be used to determine how the variances of sampling, sample preparation and chemical analysis or physical testing propagate and hence determin
33、e the total variance for the measurement chain. This sampling theory can also be used to optimize mechanical sampling systems and manual sampling methods. If a sampling scheme is to provide representative samples, it is necessary that all parts of the slurry in the lot have an equal opportunity of b
34、eing selected and appearing in the lot sample for testing. Any deviation from this basic requirement can result in an unacceptable loss of accuracy. A sampling scheme having incorrect selection techniques, i.e. with non-uniform selection probabilities, cannot be relied upon to provide representative
35、 samples. Sampling of slurries should preferably be carried out by systematic sampling on a time basis (see Clause 10). If the slurry flow rate and the coal-solids concentration vary with time, the slurry volume and the dry solids mass for each increment will vary accordingly. It is necessary to sho
36、w that no systematic error (bias) is introduced by periodic variation in quality or quantity where the proposed sampling interval is approximately equal to a multiple of the period of variation in quantity or quality. Otherwise, stratified random sampling should be used (see Clause 11). Best practic
37、e for sampling slurries is to mechanically cut freely falling streams (see Clause 12), with a complete cross-section of the stream being taken during the traverse of the cutter. Access to freely falling streams can sometimes be engineered at the end of pipes or by incorporating steps or weirs in lau
38、nders and chutes. If samples are not collected in this manner, non-uniform concentration of coal solids in the slurry due to segregation and stratification of the solids can lead to bias in the sample that is collected. Slurry flow in pipes can be homogenous with very fine particles dispersed unifor
39、mly in turbulent suspension along the length and across the diameter of the pipe. However, more commonly, the slurry in a pipe has significant particle-concentration gradients across the pipe and there can be concentration fluctuations along the length of the pipe. These common conditions are called
40、 heterogeneous flow. Examples of such flow are full-pipe flow of a heterogeneous suspension or partial-pipe flow of a fine suspension above a slower moving or even stationary bed of coarser particles in the slurry. For heterogeneous flow, bias is likely to occur where a tapping is made into the slur
41、ry pipe to locate either a flush-fitting sample take-off pipe or a sample tube projecting into the slurry stream for extraction of samples. The bias is caused by non-uniform concentration profiles in the pipe and the different trajectories followed by particles of different masses due to their inert
42、ia, resulting in larger or denser particles being preferentially rejected from or included in the sample. BS ISO 20904:20063In slurry channels such as launders, heterogeneous flow is almost always present, and this non-uniformity in particle concentration is usually preserved in the discharge over a
43、 weir or step. However, sampling at a weir or step allows complete access to the full width and breadth of the stream, thereby enabling all parts of the slurry stream to be collected with equal probability. Sampling of slurries in stationary situations, such as a settled or even a well-stirred slurr
44、y in a tank, holding vessel or dam is not recommended, because it is virtually impossible to ensure that all parts of the slurry in the lot have an equal opportunity of being selected and appearing in the lot sample for testing. Instead, sampling should be carried out from moving streams as the tank
45、, vessel or dam is filled or emptied. 4.2 Sampling errors 4.2.1 General The processes of sampling, sample preparation and measurement are experimental procedures, and each procedure has its own uncertainty appearing as variations in the final results. When the average of these variations is close to
46、 zero, they are called random errors. More serious variations contributing to the uncertainty of results are systematic errors, which have averages biased away from zero. There are also human errors that introduce variations due to departures from prescribed procedures for which statistical analysis
47、 procedures are not applicable. The characteristics of the solids component of a slurry can be determined by extracting samples from the slurry stream, preparing test samples and measuring the required quality characteristics. The total sampling error, ET, can be expressed as the sum of a number of
48、independent components (Gy, 19825; Pitard, 19936). Such a simple additive combination is not possible if the components are correlated. The total sampling error, ET, expressed as a sum of its components, is given by Equation (1): TQ1Q2Q3WDEPE EEEEE E=+ (1) where EQ1is short-range quality fluctuation
49、 error associated with short-range variations in quality of the solids component of the slurry; EQ2is long-range quality fluctuation error associated with long-range variations in quality of the solids component of the slurry; EQ3is periodic quality fluctuation error associated with periodic variations in quality of the solids component of the slurry; EWis weighting error associated with variations in slurry flow rate; EDis increment delimitation error introduced by incorrect increment delimitation; EEis increment
