ASTM D7430/D7430M-22

Standard Practice for Mechanical Sampling of Coal

SIGNIFICANCE AND USE
6.1 It is intended that this practice be used to provide a sample representative of the coal from which it is collected. Because of the variability of coal and the wide variety of mechanical sampling equipment available, caution should be used in all stages of the sample collection process, the design of sampling system specifications, the equipment procurement, and the acceptance testing of installed equipment.  
6.2 After removal from the sampling system and further preparation (Practice D2013/D2013M), the sample may be analyzed for a number of different parameters. These parameters may define the lot's value, its ability to meet specifications, its environmental impact, as well as other properties.
SCOPE
1.1 This practice is divided into four parts: A, B, C, and D. These four parts represent the previous Practices D7256/D7256M, D4916, D4702, and D6518. These four standards are the four that govern the mechanical sampling of coal and have been combined into one document for the ease of reference of the users of these standards.  
1.2 The scope of Part A can be found in Section 4.  
1.3 The scope of Part B can be found in Section 13.  
1.4 The scope of Part C can be found in Section 19.  
1.5 The scope of Part D can be found in Section 32.  
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For specific hazard statements, see Sections 7, 16, 21, 35, and 38.1.1.  
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Oct-2022
• ICS: 73.040 - Coals
• ICS: 75.160.10 - Solid fuels
• Technical Committee: D05 - Coal and Coke
• Drafting Committee: D05.23 - Sampling

Relations

• Refers: ASTM D121-15(2024) - Standard Terminology of Coal and Coke
• Effective Date: 01-Mar-2024
• Refers: ASTM D2234/D2234M-19 - Standard Practice for Collection of a Gross Sample of Coal
• Effective Date: 01-Dec-2019
• Refers: ASTM D2234/D2234M-17 - Standard Practice for Collection of a Gross Sample of Coal
• Effective Date: 15-Oct-2017
• Refers: ASTM D2234/D2234M-16 - Standard Practice for Collection of a Gross Sample of Coal
• Effective Date: 01-Mar-2016
• Refers: ASTM D121-15 - Standard Terminology of Coal and Coke
• Effective Date: 01-Sep-2015
• Refers: ASTM E177-14 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-May-2014
• Refers: ASTM E177-13 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-May-2013
• Refers: ASTM E122-09e1 - Standard Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average for a Characteristic of a Lot or Process
• Effective Date: 01-Aug-2011
• Refers: ASTM E177-10 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-Oct-2010
• Refers: ASTM E105-10 - Standard Practice for Probability Sampling Of Materials
• Effective Date: 01-Oct-2010
• Refers: ASTM D2234/D2234M-10 - Standard Practice for Collection of a Gross Sample of Coal
• Effective Date: 01-Jan-2010
• Refers: ASTM D2234/D2234M-09a - Standard Practice for Collection of a Gross Sample of Coal
• Effective Date: 01-Oct-2009
• Refers: ASTM D121-09a - Standard Terminology of Coal and Coke
• Effective Date: 01-Oct-2009
• Refers: ASTM E122-09 - Standard Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average for a Characteristic of a Lot or Process
• Effective Date: 01-Aug-2009
• Refers: ASTM D121-09 - Standard Terminology of Coal and Coke
• Effective Date: 01-Feb-2009

Overview

ASTM D7430/D7430M-22 – Standard Practice for Mechanical Sampling of Coal is an internationally recognized standard issued by ASTM International. This comprehensive standard consolidates prior standards (D7256, D4916, D4702, and D6518) to provide uniform guidelines for the mechanical collection and within-system preparation of representative coal samples from moving streams. The standard is critical for ensuring that coal samples are collected in a manner that accurately represents the consignment or lot from which they are taken, accommodating the inherent variability in coal and the complexity of modern coal-handling systems.

Key Topics

• Representative Sampling: Ensures that samples collected are statistically representative of the entire coal lot, minimizing bias and maximizing accuracy.
• Mechanical Sampling Systems: Covers the design, operation, and maintenance of falling-stream, cross-belt, and auger sampling equipment.
• Procedural Requirements: Specifies minimum numbers and mass of sample increments, guidelines for systematic or random collection intervals, and the distribution of increments throughout the entire lot.
• Sample Preparation: Addresses the mechanical division and reduction of the sample within the system prior to laboratory preparation, as per referenced standards such as ASTM D2013/D2013M.
• Equipment Quality Assurance: Emphasizes acceptance testing, regular maintenance, and routine inspections to guarantee sampling system reliability and integrity.
• Safety and Environmental Considerations: Stresses the importance of complying with safety protocols, proper use of personal protective equipment, and responsible environmental practices.
• Quality Management: Outlines the need for quality assurance programs to monitor sampling ratios, sample weights, and system performance.

Applications

The methods and practices set forth in ASTM D7430/D7430M-22 are crucial in a variety of industries and operational contexts, including:

• Coal Production and Processing: Reliable sampling is essential for controlling mining operations, cleaning plant performance, and product quality.
• Quality Assurance and Compliance: Mechanical sampling supports verification that shipments meet contract specifications for constituents such as moisture, ash, and sulfur content, thereby determining the commercial value of coal lots.
• Environmental Monitoring: Accurate coal analysis helps stakeholders understand the environmental impact of coal usage and supports regulatory reporting.
• Plant Efficiency and Cost Allocation: Representative samples enable precise evaluation of plant throughput, operational efficiency, and production costs.
• Trade and Billings: Sampling data is often used as the basis for product valuation and commercial transactions between suppliers and users of coal.

Related Standards

ASTM D7430/D7430M-22 references and works in conjunction with several key standards in the coal industry, including:

• ASTM D121: Terminology of Coal and Coke
• ASTM D2013/D2013M: Practice for Preparing Coal Samples for Analysis
• ASTM D2234/D2234M: Practice for Collection of a Gross Sample of Coal
• ASTM D3302: Test Method for Total Moisture in Coal
• ASTM D4749: Test Method for Performing the Sieve Analysis of Coal and Designating Coal Size
• ASTM E105: Guide for Probability Sampling of Materials
• ASTM E122: Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average for a Characteristic of a Lot or Process
• ASTM E177: Practice for Use of the Terms Precision and Bias in ASTM Test Methods

By adhering to ASTM D7430/D7430M-22, organizations ensure that coal sampling processes are consistent, scientifically sound, and recognized worldwide, supporting both regulatory compliance and commercial best practices in coal sampling and analysis.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D7430/D7430M − 22
Standard Practice for
Mechanical Sampling of Coal
This standard is issued under the fixed designation D7430/D7430M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Analysis data obtained from coal samples are used in establishing price, controlling mine and
cleaning plant operations, allocating production costs, and determining plant or component efficiency.
The task of obtaining a sample of reasonable mass to represent an entire lot presents a number of
problems and emphasizes the necessity for using standard sampling procedures.
Coal is one 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 is
further complicated by the use of the analytical results, the sampling equipment available, the quantity
to be represented by the sample, and the degree of precision required.
This practice gives the overall requirements for the collection and within-system preparation of coal
samples through the use of mechanical sampling systems utilizing falling-stream, cross-belt, and auger
designs. This practice also gives the overall requirements for the bias testing and quality management
of mechanical coal sampling systems. The wide varieties of coal-handling facilities preclude the
publication of detailed procedures for every sampling situation. The proper collection of the sample
involves an understanding and consideration of the physical character of the coal, the number and
mass of increments, and the overall precision required.
1. Scope 1.7 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.1 This practice is divided into four parts: A, B, C, and D.
ization established in the Decision on Principles for the
These four parts represent the previous Practices D7256/
Development of International Standards, Guides and Recom-
D7256M, D4916, D4702, and D6518. These four standards are
mendations issued by the World Trade Organization Technical
the four that govern the mechanical sampling of coal and have
Barriers to Trade (TBT) Committee.
been combined into one document for the ease of reference of
the users of these standards.
2. Referenced Documents
1.2 The scope of Part A can be found in Section 4.
2.1 ASTM Standards:
1.3 The scope of Part B can be found in Section 13.
D121 Terminology of Coal and Coke
D2013/D2013M Practice for Preparing Coal Samples for
1.4 The scope of Part C can be found in Section 19.
Analysis
1.5 The scope of Part D can be found in Section 32.
D2234/D2234M Practice for Collection of a Gross Sample
1.6 This standard does not purport to address all of the
of Coal
safety concerns, if any, associated with its use. It is the
D3302 Test Method for Total Moisture in Coal
responsibility of the user of this standard to establish appro-
D4621 Guide for Quality Management in an Organization
priate safety, health, and environmental practices and deter- 3
That Samples or Tests Coal and Coke (Withdrawn 2010)
mine the applicability of regulatory limitations prior to use.
D4702 Practice for Quality Management of Mechanical
For specific hazard statements, see Sections 7, 16, 21, 35, and 3
Coal Sampling Systems (Withdrawn 2008)
38.1.1.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
This practice is under the jurisdiction of ASTM Committee D05 on Coal and contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Coke and is the direct responsibility of Subcommittee D05.23 on Sampling. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Nov. 1, 2022. Published December 2022. Originally the ASTM website.
approved in 2008. Last previous edition approved in 2021 as D7430/D7430M – 21. The last approved version of this historical standard is referenced on
DOI: 10.1520/D7430_D7430M-22. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7430/D7430M − 22
D4749 Test Method for Performing the Sieve Analysis of 3.2.9 cross-belt sampler, n—a single sampling machine or
Coal and Designating Coal Size component of a mechanical sampling system designed to
D4916 Practice for Mechanical Auger Sampling (Withdrawn extract an increment directly from a conveyor belt surface by
2008) sweeping a sampling device (cutter) through the material on
D6518 Practice for Bias Testing a Mechanical Coal Sam- the conveyor.
pling System (Withdrawn 2008)
3.2.10 delimitation error, n—a material error that occurs
D7256/D7256M Practice for Mechanical Collection and
when all the elements in a cross section of a coal stream do not
Within-System Preparation of a Gross Sample of Coal
have an equal probability of being intercepted (captured) by the
from Moving Streams (Withdrawn 2008)
sampler cutter during increment collection.
E105 Guide for Probability Sampling of Materials
3.2.11 ellipsoidal region, n—an area that is formed by plane
E122 Practice for Calculating Sample Size to Estimate, With
sections of ellipses that are defined by the values selected for
Specified Precision, the Average for a Characteristic of a
the largest tolerable bias of each coal characteristic used in the
Lot or Process
bias test; the region will be used to determine if the system is
E177 Practice for Use of the Terms Precision and Bias in
biased.
ASTM Test Methods
3.2.12 falling-stream sampler, n—a single sampling ma-
chine or component of a mechanical sampling system designed
3. Terminology
to extract an increment from a falling stream of coal at the
3.1 Definitions—Definitions applicable to this practice are
discharge end of a conveyor or chute by moving a sampling
listed in Terminology D121.
device (cutter) through the falling stream of material.
3.2 Definitions of Terms Specific to This Standard:
3.2.13 Hotelling’s Squared T (T ) test, n—a statistical test
3.2.1 accuracy, n—(1) generally, a term used to indicate the
that is used to evaluate multivariate data; it is the multivariate
reliability of a sample, a measurement, or an observation; (2)
equivalent of the Student’s t-test.
specifically, a measure of closeness of agreement between an
3.2.14 largest tolerable bias (LTB), n—an interval whose
experimental result and the true value.
upper and lower bounds represent the limits of an acceptable
3.2.1.1 Discussion—An example is the observed and true
bias.
sulfur content of a coal consignment. This measurement is
affected by random errors as well as by bias. 3.2.15 mechanical sampling system, n—a single machine or
series of interconnected machines whose purpose is to extract
3.2.2 activation interval, n—for a falling-stream or cross-
mechanically, or process (divide and reduce), or a combination
belt cutter, the time from the beginning of movement for taking
thereof, a sample of coal.
an increment, to the beginning of movement for taking of the
next increment. 3.2.16 paired data set, n—system and reference values
observed on samples collected and compared from the same
3.2.3 auger increment, n—the retained portion of one ex-
batch of material.
traction operation of the auger.
3.2.17 precision, n—a term used to indicate the capability of
3.2.4 auger sampler, n—a mechanical device that extracts a
a person, an instrument, or a method to obtain reproducible
columnar sample of coal from a railcar, truck, barge, or
results; specifically, a measure of the random error as ex-
stockpile and any associated sub-system or within-system
pressed by the variance, standard error, or a multiple of the
components.
standard error (see Practice E177).
3.2.5 bias, n—the difference between the population mean
3.2.18 reference sample, n—a sample used in testing of a
of the mechanical sampler test results and the accepted
mechanical sampling system which is comprised of one or
reference value.
more increments collected from the test batch or lot of coal by
3.2.6 confidence interval, n—a numeric interval with a
the stopped belt method as described in Practice D2234/
lower limit and a higher limit within which the true parameter
D2234M.
value is estimated to fall; the confidence interval percentage
3.2.19 reject stream, n—the coal flow within a mechanical
indicates the percentage of time the true value will fall within
sampling system, which occurs at each stage of division, before
the interval if the procedure is continuously repeated.
and after reduction, and is not included in the system sample.
3.2.7 consignment, n—a discrete amount of coal, such as a
3.2.20 sampling ratio, n—the mass of the system sample
shipment, a car load, a unit train, or a day’s production.
divided by the mass of the corresponding coal sampled.
3.2.7.1 Discussion— A consignment may include more than
one lot of coal and may correspond to a specific period of time, 3.2.21 save stream, n—the coal flow within a mechanical
such as a sampling period or a billing period. sampling system which occurs at each stage of division, before
and after reduction, and after the final stage of division
3.2.8 correlation, n—a measure of the linear dependence
becomes the system sample.
between paired system and reference measurements.
3.2.8.1 Discussion—Correlation frequently is expressed by 3.2.22 statistical independence, n—two sample values are
the correlation coefficient, which can take a value from minus statistically independent if the occurrence of either one in no
one (perfect negative linear relationship) to plus one (perfect way affects the probability assigned to the occurrence of the
positive linear relationship). other.
D7430/D7430M − 22
3.2.23 surrogate sample, n—a sample, used in the evalua- 3.2.26.1 Discussion—As an example of Walsh averages,
tion of a mechanical sampling system, which is comprised of assume one has three observations (differences) designated as
one or more increments collected from a coal stream within the x1, x2, and x3. There are then a total of 3(4)/2 = 6 Walsh
mechanical sampling system in accordance with Practice averages. They are as follows: x1, x2, x3, (x1 + x2)/2, (x1 +
D2234/D2234M, Conditions “A” or “B.” x3)/2, and (x2 + x3)/2.
3.2.23.1 Discussion—Such a sample may be considered
3.2.27 Wilcoxon Signed Rank Test, n—a non-parametric
acceptable for evaluation of a mechanical sampling system’s
statistical procedure for calculating the point estimate and
components, excluding the primary cutter, when demonstrated
confidence interval for a sample drawn from a population with
to be equivalent to the reference sample.
symmetric distribution.
3.2.24 system sample, n—a sample collected from a test
3.2.28 within-system preparation, n—the process of gross
batch or lot of coal by the final stage of a mechanical sampling
sample preparation carried out mechanically by sequential
system.
crushing (reduction) equipment or division equipment, or both.
3.2.25 unbiased sample (representative sample), n—a
3.2.28.1 Discussion—It may be carried out by processing
sample free of bias.
increments individually or by batching increments together and
3.2.26 Walsh averages, n—given a series of observations
processing them together as a group. In any case, within-
(differences) x1, x2, . xn, the n (n + 1)/2 pair-wise averages
system preparation is conducted in a manner to minimize
given by:
moisture changes and without removing the gross sample or its
~xi1xj!/2, 1 # i # j # n (1) increments from the sampling system.
D7430/D7430M − 22
PART A – MECHANICAL COLLECTION AND WITHIN-SYSTEM PREPARATION OF A GROSS SAMPLE OF
COAL FROM MOVING STREAMS
[Old Practice D7256/D7256M]
4. Scope
4.1 Part A—Mechanical Collection and Within-System mass of increments required for a gross sample for both
Preparation of a Gross Sample of Coal from Moving Streams— general- and special-purpose sampling.
Covers procedures for the mechanical collection of a sample
5.4 The only processes of sample division and reduction
under Classification I-B-1 and I-B-2 (Practice D2234/
covered in this document are the use of mechanical sample
D2234M) and the within-system preparation (reduction and
dividers for the division of the sample and mechanical crushing
division) of gross samples utilizing various components of the
equipment for the reduction of the sample, both of which are
mechanical sampling system.
within-system components of the mechanical sampling system.
4.1.1 Part A describes mechanical sampling procedures for
5.5 The procedures appear in the following order:
coals (1) by size and condition of preparation (for example,
Test Method Section
mechanically cleaned coal or raw coal), and (2) by sampling
Sampling of Coals Based on Size and Condition 10.1
characteristics.
of Preparation
4.1.2 Units—The values stated in either SI units or inch-
General-Purpose Sampling Procedure 10.1.1
Number and Mass of Increments 10.1.1.2
pound units are to be regarded separately as standard. The
Number of Gross Samples 10.1.1.4
values stated in each system are not necessarily exact equiva-
Special-Purpose Sampling 10.1.2
lents; therefore, to ensure conformance with the standard, each
Number and Mass of Increments 10.1.2.2
Number of Gross Samples 10.1.2.3
system shall be used independently of the other, and values
Division of the Gross Sample Before Crushing 10.2
from the two systems shall not be combined.
Reduction and Division 10.3
4.1.3 In this practice, the term “mass” applies to measure-
ments expressed with both SI units (for example, kg) and
6. Significance and Use
inch-pound units (for example, lb).
6.1 It is intended that this practice be used to provide a
sample representative of the coal from which it is collected.
5. Summary of Practices
Because of the variability of coal and the wide variety of
5.1 The general-purpose sampling procedures are intended
mechanical sampling equipment available, caution should be
to provide, in 19 of 20 cases, dry ash results that are within an
used in all stages of the sample collection process, the design
interval of 6 ⁄10 of the average dry ash results that would be
of sampling system specifications, the equipment procurement,
obtained in hypothetical repeated sampling.
and the acceptance testing of installed equipment.
5.2 Special-purpose sampling procedures apply to the sam-
6.2 After removal from the sampling system and further
pling of coal when other precision limits are required, or when
preparation (Practice D2013/D2013M), the sample may be
other constituents are used to specify precision, or for perfor-
analyzed for a number of different parameters. These param-
mance tests.
eters may define the lot’s value, its ability to meet
specifications, its environmental impact, as well as other
5.3 For coals of known size and condition of preparation, a
properties.
table (Table 1) is given for the determination of the number and
7. Hazards
7.1 This standard does not purport to address all of the
TABLE 1 Number and Mass of Increments for General-Purpose
A
safety concerns, if any, associated with its use. It is the
Sampling Procedure
responsibility of the user of this standard to establish appro-
16 mm 50 mm 150 mm
Top Size
B
[0.625 in.] [2 in.] [6 in.]
priate safety, health, and environmental practices and deter-
C
Mechanically Cleaned Coal mine the applicability of regulatory limitations prior to use.
Minimum number of 15 15 15
7.2 Warning—The operation, inspection, maintenance, and
increments
Minimum mass of 1 [2] 3 [6] 7 [15]
cleaning of mechanical sampling equipment involves hazard-
increments, kg [lb]
ous operations, conditions, and equipment that may result in
C
Raw (Uncleaned Coal)
serious bodily harm or death. These hazards include, but are
Minimum number of 35 35 35
increments
not limited to, intermittent operation, remote startup, powerful
Minimum mass of 1 [2] 3 [6] 7 [15]
electrical or hydraulic drives, moving conveyors, crushers, etc.
increments, kg [lb]
A
Conditions C and D are not addressed in this practice. 7.3 It is essential that personnel wear all required personal
B
For coals above 150 mm [6 in.] top size, the sampling procedure should be
protective equipment. Personnel should be fully knowledge-
mutually agreed upon in advance by all parties concerned.
C able of, and follow, all site-specific safety rules and govern-
See 9.2.2.
mental regulations regarding the equipment in question,
D7430/D7430M − 22
including, but not limited to, releasing stored energy, confined increases with an increase in free impurity. A coal high in
spaces, opening of inspection doors during operation, and inherent impurity and with comparatively little free impurity
electrical power lock out/tag out. Be certain to de-energize may exhibit much less variability than a coal with a low
main power source and not rely on local or control circuits. inherent impurity and a relatively high proportion of free
impurity. For most practical purposes, an increase in the ash
8. Increment Collection Classification
content of a given coal usually indicates an increase in
variability. It is imperative that not less than the minimum
8.1 The type of selection, the conditions under which
specified number of increments of not less than the minimum
individual increments are collected, and the method of spacing
specified mass be collected from the lot.
of increments from the coal consignment or lot are classified
9.2.2 Condition of Preparation—If there is any doubt as to
according to the following descriptions and Table 1 in Practice
the condition of preparation of the coal (for example, mechani-
D2234/D2234M.
cally cleaned coal or raw coal), the number of increments for
8.2 Types of Increments—The only type of selection of
raw coal shall apply. For the purpose of application of the
increments covered by this document is Type I where there is
minimum number of increments in Table 1, mechanically
no human discretion in the selection of the pieces of coal or
cleaned coal is defined as coal which has been mechanically
portions of the coal stream. Type I selection increments
cleaned by a specific gravity process in all sieve sizes above
generally yield more accurate results than Type II where
150 μm mesh [No. 100 USA] Standard. Similarly, although a
human discretion is exercised in the selection of specific pieces
coal has been mechanically cleaned, it may still show signifi-
of coal or of specific portions of the stream, pile, or shipment.
cant variation. For example, the coal may be a blend of two
8.3 Conditions of Increment Collection—The conditions
different portions of one seam or a blend of two different
under which individual increments are collected are the con-
seams. In such cases where significant variation is possible, the
ditions of the main body of coal relative to the portion
number of increments should be as specified for raw (un-
withdrawn. Only Condition B (Full-Stream Cut), in which a
cleaned) coal.
full cross-section cut is removed from a moving stream of coal,
9.3 Distribution of Increments—It is essential that the incre-
is covered by this document.
ments be distributed throughout the lot to be sampled. This
8.4 Spacing of Increments—The spacing of increments per-
distribution is related to the entire volume of the lot, not merely
tains to the kind of intervals between increments. Two spacing
its surface or any linear direction through it or over it. If
methods are recognized: systematic and random. Systematic
circumstances prevent the sampler from applying this
spacing is usually preferable.
principle, the lot is sampled only in part, and the gross sample
8.4.1 Systematic Spacing 1, in which the movements of
is representative only of this part. The spacing of the incre-
individual increment collection are spaced evenly in time or in
ments shall be varied if the possibility exists that increment
position over the lot. This practice allows both time-based and
collection may get “in phase” with the sequence of coal
mass-based distribution of increments.
variability. Example: routine sampling of commercial coal
8.4.2 Random Spacing 2, in which the increments are
from a continuous stream (conveyor belt) in which increment
spaced at random in time or in position over the lot.
collection is automatic and its sequence coincides with the
“highs” or “lows” in the content of fines.
9. Organization and Planning of Sampling Operations
9.3.1 Independence of Cutter Activation Intervals—Select
9.1 This practice provides definitive procedures for the
cutter activation intervals so that cutters do not activate at a set
collection of a gross sample. Parties claiming to use this
time in relation to the cutter from a previous stage. In addition,
practice must adhere to the procedures as set out in this
the activation interval for any sampling stage shall not be
practice. If the sampling is not done in accordance with the
evenly divisible into the previous stage activation interval.
procedures set out in this practice, then that sample may not be
9.4 Dimensions of Sampling Device—The opening of the
suitable for comparison with a sample collected by the proce-
sampling device shall be no less than 3.0 times the nominal top
dures described in this practice. Since it may be impracticable
size of the coal but no less than 31.8 mm [1.25 in.]
or impossible to take another sample of a given lot of coal, it
9.4.1 For systems installed prior to December 31, 2013, the
is essential that parties agree on sampling procedures prior to
opening of the sampling device may be 2.5 times the nominal
undertaking sampling.
top size of the coal but no less than 31.8 mm [1.25 in.].
9.2 Selection of Appropriate Sampling Procedure—
9.4.2 The sampling device shall be of sufficient capacity to
Variations in coal-handling facilities make it impossible to
completely retain or entirely pass the increment without
publish rigid rules covering every sampling situation in com-
spillage at the maximum rate of coal flow.
plete and exact detail. Proper sampling involves an understand-
9.5 Characteristics and Movement of Sampling Device—In
ing and proper consideration of the minimum number and mass
sampling from moving streams of coal, the sampling device
of increments, the size consist of the coal, the condition of
shall be designed to collect each increment with no selective
preparation of the coal, the variability of the constituent sought,
rejection of material by size and with no contamination by
and the degree of precision required.
nonsample material.
9.2.1 Number and Mass of Increments—The number and
mass of increments required for a given degree of precision 9.5.1 Falling-Stream Sampler—In collecting an increment,
depends upon the variability of the coal. This variability the falling-stream cutter moves at a constant velocity through
D7430/D7430M − 22
the entire cross section of the stream of coal. The edges of the damming of conveyed material against the outside of the cutter
cutter opening shall be at the same height and parallel along its body as the cutter travels though the stream. Design the hopper
length. The mass, m, in kg [lb] of material collected in one pass
or chute that receives the primary increment to include skirting
through the stream by a falling-stream cutter, with cutting or other barriers to prevent the inclusion of non-sample
edges and cutter velocity perpendicular to the stream flow, is
material that is swept in its direction by the upstream side plate
calculated from the following equation:
of the primary cutter. Furthermore, ensure by design that a
complete increment is extracted, and that the configuration of
Cw Cw
m 5 m 5 (2)
F G
the conveyor belt fits the arc of travel of the cross-belt cutter
3.6v 1.8v
c c
and prevents deflection of the conveyor away from the primary
where:
cutter at the point of sample collection. This can be accom-
C = stream flow rate in Mg/h [ton/h],
plished with belt support devices which shape the conveyor
w = tip-to-tip cutter aperture width in mm [in.], and
into an arc at the point of sample collection; and a wiper on the
v = average cutter speed in mm/s [in./s].
c
tip of the cutter to ensure collection of fine sized material (see
NOTE 1—Falling-stream cutter speeds of 460 mm ⁄s [18 in. ⁄s] or less
Fig. 2 and Fig. 3). The mass, m, in kg [lb], of material collected
have been found to produce acceptable results.
in one pass through the moving stream by a cutter with cutting
NOTE 2—The constant value 3.6 [1.8] in the denominator of Eq 2
edges and cutter velocity perpendicular to the stream flow is
converts Mg/h to kg/s [ton/h to lb/s].
NOTE 3—If the falling-stream cutter velocity is not constant as it
calculated from the following equation:
traverses the material stream, the mass of collected material may not agree
Cw Cw
with that calculated using Eq 2.
m 5 m 5 (3)
F G
3.6v 1.8v
b b
9.5.1.1 An example of a falling-stream sampler is shown in
Fig. 1. where:
9.5.2 Cross-Belt Sampler—Design and operate the cross-
C = stream flow rate in Mg/h [ton/h],
belt cutter at a velocity across the conveyor surface that is high
w = tip-to-tip cutter aperture width in mm [in.], and
enough to prevent selective rejection of material by size,
v = conveyor belt speed in mm/s [in./s].
b
prevent contamination of the sample with material not col-
NOTE 4—The constant value 3.6 [1.8] in the denominator of Eq 3
lected within the cutter, and avoid mechanical problems due to converts Mg/h to kg/s [ton/h to lb/s].
FIG. 1 Falling-Stream Sampler
D7430/D7430M − 22
FIG. 2 Cross Belt Sampler With Conveyor Arc Support
FIG. 3 Cross-belt Sampler Without Conveyor Arc Support
NOTE 5—To avoid mechanical problems and spillage and to ensure the better. Ratios of cutter speed to belt speed of 1.5 or greater have been
correct sample delimitation, the higher ratio of cutter speed to belt speed found to produce acceptable results.
D7430/D7430M − 22
9.5.2.1 An example of a cross-belt sampler is shown in Fig. minimum to prevent both loss of fines and moisture. Samples
4. in which moisture content is important shall be protected from
excessive air flow and then shall be stored in moisture-tight
9.6 There shall be no structural member or other impedi-
containers. Metal cans with airtight lids, or heavy vapor-
ment within a cutter body that impedes either sample collection
impervious bags, properly sealed, are satisfactory for this
or sample discharge.
purpose.
9.7 Preservation of Moisture—The increments obtained dur-
ing the sampling period shall be protected from changes in 9.8 Contamination—The sampling arrangement shall be
planned so that contamination of the increments with foreign
composition as a result of exposure to rain, snow, wind, sun,
contact with absorbent materials, and extremes of temperature. material or unrelated coal does not create bias of practical
The circulation of air through equipment must be reduced to a consequence.
FIG. 4 Cross-Belt Sampler
D7430/D7430M − 22
9.9 Mechanical System Features—It is essential that mecha- increment masses. Table 1 lists the absolute minimum number
nized systems as a whole, including sampling machines, of increments for general-purpose sampling which may not be
chutes, feed conveyors, crushers and other devices, be self-
reduced, except as specified in 10.1.1.5(2). Other consider-
cleaning and non-clogging and be designed and operated in a ations may make it advisable or necessary to increase this
manner that will facilitate routine inspection and maintenance.
number of increments.
10.1.1.4 Number of Gross Samples—Under the general-
9.10 Personnel—Because of the many variations in the
purpose sampling procedure, for quantities up to approxi-
conditions under which coal must be sampled, and in the nature
mately 1000 Mg [1000 tons], it is recommended that one gross
of the material being sampled, it is essential that the samples be
sample represent the lot. Take this gross sample in accordance
collected under the direct supervision of a person qualified by
with the requirements prescribed in Table 1.
training and experience for this responsibility.
10.1.1.5 For quantities over 1000 Mg [1000 tons], use any
9.11 Criteria of Satisfactory Performance—A satisfactory
of the following alternatives:
arrangement for mechanical collection and within-system
(1) Take one gross sample for the lot and analyze it to
preparation of a gross sample of coal from a moving stream
represent the quality of the lot. Collect the number of incre-
must properly apply the principles of systematic sampling. Use
ments N calculated from Eq 4:
the instructions in Part A to collect increments from the lot
being sampled either at random or even intervals in such a
L
manner that the quality and size consist of each part of the lot N 5 KΠ(4)
has an equal probability of being represented in the sample.
where:
Use the instructions in Part C to evaluate the mechanical
performance of the system as a matter of routine, especially in
L = number of Mg [tons], and
regards to monitoring sampling ratios and system inspections. K = 15.7 [15] for mechanically cleaned coal or 36.7 [35] for
Use the instructions in Part D to bias test the system using
raw coal.
prescribed procedures and methods.
(2) Divide the lot into sub-lots and take a separate gross
sample from each sub-lot. Use Eq 4 to determine the minimum
9.12 Relative Location of Sampling and Weighing—It is
number of increments for each sub-lot, with L being the sub-lot
preferable that coal be weighed and sampled at the same time.
quantity. Mass-average the analyses of the sub-lot samples to
If there is a lapse in time between these two events, consider-
represent the quality of the original lot.
ation should be given by both the purchaser and the seller to
changes in moisture during this interval and the consequent
10.1.1.6 The maximum lot size shall be chosen by mutual
shift in relationship of moisture to the true quality of the coal
agreement between the seller and the buyer of the coal, with
at the instant when ownership of the coal transfers from one to
each party taking into account the risks associated with the
the other.
choice. Potential consequences include:
(1) Large samples requiring excessive off-line preparation
10. Procedures
steps can result in sampling moisture losses.
(2) No quality information is obtained on within-lot vari-
10.1 Sampling of Coals Based on Size and Condition of
ability. Lot sizes generally should not exceed quantities for
Preparation:
which critical quality levels apply in use of the coal.
10.1.1 General-Purpose Sampling:
(3) When a given quantity of coal that might be represented
10.1.1.1 Where probability sampling is employed, the
by a single lot is divided into multiple sub-lots, the imprecision
general-purpose sampling procedures are intended to provide,
of the reported quality for that given quantity is reduced. For a
in 19 of 20 cases, dry ash results that are within the interval of
1 given quantity, the component of imprecision due to sample
6 ⁄10 of the average dry ash results that would be obtained in
preparation and analysis is reduced by 1/=n, where n is the
hypothetical repeated sampling.
number of sub-lots.
10.1.1.2 Number and Mass of Increments—Obtain the num-
ber and mass of increments as specified in Table 1, except as
10.1.2 Special-Purpose Sampling:
provided in 10.1.1.5(2). Determine the minimum number of
10.1.2.1 This special-purpose sampling procedure shall ap-
increments from the condition of preparation, and determine
ply to the sampling of coal when increased precision is
the minimum mass of each increment from the top size of the
required, and the only knowledge of the coal is its top size and
coal. Classify the coals to be sampled according to the general
conditions of preparation.
purpose procedure into three groups by top size. Further
10.1.2.2 Number and Mass of Increments—Take the same
classify each of these groups into two subgroups in accordance
number and mass of increments per gross sample as specified
with the condition of preparation. These classifications are
in Table 1, or as specified in 10.1.1.5(2).
shown in Table 1.
10.1.2.3 Number of Gross Samples—To obtain increased
10.1.1.3 Variations in construction of the sampling device
and flow, structure, or size consist of the coal may make it precision for the final result for a given consignment, increase
the number of gross samples collected from that consignment
impracticable to collect increments as small as the minimum
mass specified in Table 1. In such cases, collect an increment and analyze each gross sample separately, reporting the aver-
age of results. To reduce errors to one half, that is, to “double”
of greater mass. However, do not reduce the minimum number
of increments, regardless of large excesses of individual the precision, take four times as many gross samples. Similarly,
D7430/D7430M − 22
to reduce errors to one third, to “triple” the precision, take nine consideration all site safety rules and which inspections can
times as many gross samples. only be performed while equipment is de-energized and
10.1.3 Sampling for Total Moisture Only: isolated.
10.1.3.1 The increments as established in Table 1 for
11.1.1 Ensure that component hatches and doors are ad-
mechanically cleaned coal are deemed adequate for general
equate in design and located to provide access to key areas of
purpose sampling for total moisture.
the equipment such as: (a) cutters or dividers in parked
positions; (b) condition of high-wear items such as crusher
10.2 Division of the Gross Sample Before Crushing:
hammers, bars and screens, conveyor head and tail pulley
10.2.1 Large primary increments may be divided in quantity
wipers, conveyor and cutter throat skirting, or the wiping edge
before crushing by secondary sampling. In the case of dividing
of cross-belt cutters or dividers; (c) points of potential plug-
a primary increment before crushing, the minimum increment
gage within the system; and (d) other items to that particular
mass must meet the mass specified in Table 1 for the top size
system.
listed.
11.1.2 Enable hatches and doors to be safely opened, closed,
10.2.1.1 If each primary increment is reduced in quantity by
and secured, and include seals to prevent the introduction or
secondary sampling, take at least six secondary increments
escape of air, or the introduction of moisture or contaminants
from each uncrushed primary increment. The method of
into the component.
collection of secondary increments must be proved to be free
from bias. In no case shall the mass of a secondary increment
11.1.3 Provide adequate access to the sampling system (for
be less than shown in the schedule of Table 1.
example, using permanent walkways, stairways, ladders,
platforms, etc.) to allow personnel to work safely and effec-
10.3 Reduction and Division:
tively on and around the equipment.
10.3.1 Reduce the gross or divided sample in stages and
divide by suitable mechanical sample dividers (see 10.4.2) to
11.2 To ensure reliable system performance, develop and
quantities not less than those shown in Table 1 of Practice
consistently perform well-defined and planned system
D2013/D2013M.
inspections, and preventive and corrective maintenance action
10.3.2 Mechanical division of the sample consists of auto-
programs. This will help ensure continuous and reliable opera-
matically collecting a large number of increments of the
tion by detecting and then repairing components that have
properly reduced sample. Distribute this large number of
undergone wear to a critical degree or that are affecting system
increments equally throughout the entire discharge from the
performance. To maximize the effectiveness of the preventive
sample crusher because crushers can introduce appreciable
maintenance program and the detection of issues, conduct
segregation. At each stage of division, take at least 60
frequent measurements of key components and parameters,
increments.
and monitor sample weights and ratios.
11.2.1 It is good practice to have a documented maintenance
NOTE 6—Reduction and division of the mechanical samples that do not
involve within-system components of the mechanical sampling system are
program to guide the implementation of the maintenance work
not covered by this document but governed by Practice D2013/D2013M.
and to record inspection dates, equipment hours, and mainte-
10.4 Reduction and Division Apparatus:
nance performed. Design the program to include, at a
10.4.1 Crushers or Grinders—Jaw, cone, or rotary crusher; minimum, requirements recommended by equipment and com-
ponent manufacturers for the frequency and specifics of
hammer mill; roll; or other suitable crusher to reduce the
sample. Design and operate crushers in a manner to minimize inspection, measurement, routine maintenance, and replace-
the effect of induced air circulation and thus the potential for
ment when necessary. Execute the program on a scheduled
drying the coal.
basis (by calendar, by hours of operation, by tonnage, or a
combination thereof) depending on the sampling system’s
10.4.1.1 Hammer Mill—Completely enclosed to avoid loss
of dust or moisture. frequency of use. An hour or tonnage-based program allows for
improved predictability of when to perform maintenance or
10.4.2 Sample Dividers: Mechanical—A mechanical
equipment replacement.
sample divider using a reciprocating or rotating cutter, a
rotating hopper and spout, a rotating slotted cone, a recipro-
11.2.2 It is good practice to include within the program a
cating hopper and fixed cutter, bucket cutter with either bottom
schedule for frequent and thorough cleaning of equipment to
dump or inverting discharge, slotted belt, rotary disk divider,
remove material buildup, debris, or other contaminants, to
mechanical stopped or moving belt sweeper, or other accept-
minimize the potential for plugging, and to diminish the
able devices for dividing the sample. Typical mechanical
potential for long-term corrosion or decay of equipment.
sample dividers are shown in Fig. 5. These illustrate various
11.2.3 For monitoring sampling system crusher
designs, but other acceptable designs are available.
performance, use the method prescribed in Test Method D4749
to determine the particle size distribution of crushed sample
11. Maintenance of Mechanical Sampling System
material to help prevent oversized material from passing to
Equipment
downstream cutters or dividers. Inspect the crusher
11.1 Design a mechanical sampling system and its compo- components, such as hammers, bars, and screens for wear.
Worn crusher components can cause moisture loss from the
nents to facilitate safe, thorough, and accessible inspection,
cleaning, and maintenance tasks. Safe access must take into sample material due to an increase in the time the material
D7430/D7430M − 22
NOTE 1—
(a) Reciprocating Cutter—Fig. 5(a) shows a section of a cutter which is moved across a stream of coal. At regular intervals, the cutter movement is
reversed and a sample increment is collected on each trip through the coal stream.
(b) Rotating Cutter—Fig. 5(b) shows two cutters attached to a hollow, rotating shaft. Each cutter is designed to extract increments from the feed and
to discharge these into the hollow shaft. One or more cutters may be used.
(c) Rotating Hopper and Spout—Fig. 5(c) shows the totaling hopper that receives the crushed sample and discharges it through a spout over one or
more stationary cutters.
(d) Rotating Cone—Fig. 5(d) shows a sampler developed by the British National Coal Board. Two slotted cones are locked together and rotated on
a vertical shaft so that on each revolution the common slot operating intercepts the falling stream of coal and collects an increment
FIG. 5 Mechanical Sample Dividers
stays in the crushing chamber. Inspect crusher screens fre- 12. Precision and Bias
quently and replace them promptly to prevent oversized
12.1 The precision of the general-purpose sampling
particles from passing to downstream cutters or dividers.
procedure, based on size and condition of preparation, is stated
11.3 Wear of mechanical components, or the failure to
in 10.1.1.1. If a different precision is required, see 10.1.2.
correct equipment not performing to specifications, may even-
12.2 Mechanical sampling systems are tested for bias using
tually cause a sampling system which had previously shown no
the procedures of Part D.
evidence of bias to no longer satisfy that criterion. Consistent
maintenance and inspection, along with the monitoring of
sample weights and ratios, will help ensure that the sampling
system maintains its bias-tested performance.
D7430/D7430M − 22
PART B – MECHANICAL AUGER SAMPLING
[Old Practice D4916]
13. Scope
13.1 Part B—Mechanical Auger Sampling—Describes pro- 16.3 It is essential that personnel wear all required personal
cedures for the collection of an increment, partial sample, or protective equipment. Personnel should be fully knowledge-
gross sample of material using mechanical augers. Reduction able of, and follow, all site-specific safety rules and govern-
and division of the material by mechanical equipment at the mental regulations regarding the equipment in question,
auger is also covered. Further manual or mechanical reduction including, but not limited to, releasing stored energy, confined
or division of the material elsewhere shall be performed in spaces, opening of inspection doors during operation, and
accordance with Practice D2013/D2013M. electrical power lock out/tag out. Be certain to de-energize
main power source and not rely on local or control circuits.
13.1.1 Units—The values stated in either SI units or inch-
pound units are to be regarded separately as standard. The
17. Organization and Planning of Sampling Operations
values stated in each system are not necessarily exact equiva-
lents; therefore, to ensure conformance with the standard, each 17.1 General Considerations—Mechanical auger sampling
system shall be used independently of the other, and values is designated as Condition D, Stationary Coal Sampling. When
from the two systems shall not be combined. using augers to sample, the material taken may only be
representative to the depth sampled. In addition, the parameters
14. Summary of Practice such as top size, degree of preparation, degree of material
segregation, and pattern of auger placement should also be
14.1 A sample of coal is extracted from a stationary load
considered.
contained within a railcar(s), truck(s), or barge(s) by inserting
17.2 Consideration of Top Size—Designs of mechanical
an auger into the vehicle in a vertical manner to extract a
sampling augers vary from high-powered augers with cutter
columnar sample of coal from the vehicle. Protect the coal
bits drilling through the coal to be sampled, to low-powered
collected by the auger, or processed by additional sampling
augers designed to sample loosely compacted coal. The clear-
components, from moisture change and contamination by
placing it into containers and sealing them. ance in the auger assembly and flights should be sufficient to
allow passage of the largest top size in the lot of coal to be
sampled. If the top size of coal makes the auger size
15. Significance and Use
impractical, the auger should be designed to cut through or
15.1 Auger sampling systems may be used to extract
break up the lumps of coal.
samples from trucks, railcars, barges, or static compacted
17.3 Consideration for Number of Auger Increments—The
stockpiles where the use of a full-stream mechanical sampling
number of increments required should be based on the lot size
system may be impractical. The samples obtained from these
and degree of material preparation. For purposes of this
systems can be used to establish the materials’ commercial
practice, the degree of preparation is divided into two
value or c
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7430/D7430M − 21 D7430/D7430M − 22
Standard Practice for
Mechanical Sampling of Coal
This standard is issued under the fixed designation D7430/D7430M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Analysis data obtained from coal samples are used in establishing price, controlling mine and
cleaning plant operations, allocating production costs, and determining plant or component efficiency.
The task of obtaining a sample of reasonable mass to represent an entire lot presents a number of
problems and emphasizes the necessity for using standard sampling procedures.
Coal is one 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 is
further complicated by the use of the analytical results, the sampling equipment available, the quantity
to be represented by the sample, and the degree of precision required.
This practice gives the overall requirements for the collection and within-system preparation of coal
samples through the use of mechanical sampling systems utilizing falling-stream, cross-belt, and auger
designs. This practice also gives the overall requirements for the bias testing and quality management
of mechanical coal sampling systems. The wide varieties of coal-handling facilities preclude the
publication of detailed procedures for every sampling situation. The proper collection of the sample
involves an understanding and consideration of the physical character of the coal, the number and
mass of increments, and the overall precision required.
1. Scope
1.1 This practice is divided into four parts: A, B, C, and D. These four parts represent the previous Practices D7256/D7256M,
D4916, D4702, and D6518. These four standards are the four that govern the mechanical sampling of coal and have been combined
into one document for the ease of reference of the users of these standards.
1.2 The scope of Part A can be found in Section 4.
1.3 The scope of Part B can be found in Section 13.
1.4 The scope of Part C can be found in Section 19.
1.5 The scope of Part D can be found in Section 32.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use. For specific hazard statements, see Sections 7, 16, 21, 35, and 38.1.1.
This practice is under the jurisdiction of ASTM Committee D05 on Coal and Coke and is the direct responsibility of Subcommittee D05.23 on Sampling.
Current edition approved June 1, 2021Nov. 1, 2022. Published July 2021December 2022. Originally approved in 2008. Last previous edition approved in 20202021 as
D7430/D7430M – 20.D7430/D7430M – 21. DOI: 10.1520/D7430_D7430M-21.10.1520/D7430_D7430M-22.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7430/D7430M − 22
1.7 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D121 Terminology of Coal and Coke
D2013/D2013M Practice for Preparing Coal Samples for Analysis
D2234/D2234M Practice for Collection of a Gross Sample of Coal
D3302 Test Method for Total Moisture in Coal
D4621 Guide for Quality Management in an Organization That Samples or Tests Coal and Coke (Withdrawn 2010)
D4702 Practice for Quality Management of Mechanical Coal Sampling Systems (Withdrawn 2008)
D4749 Test Method for Performing the Sieve Analysis of Coal and Designating Coal Size
D4916 Practice for Mechanical Auger Sampling (Withdrawn 2008)
D6518 Practice for Bias Testing a Mechanical Coal Sampling System (Withdrawn 2008)
D7256/D7256M Practice for Mechanical Collection and Within-System Preparation of a Gross Sample of Coal from Moving
Streams (Withdrawn 2008)
E105 Guide for Probability Sampling of Materials
E122 Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average for a Characteristic of a Lot or
Process
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
3. Terminology
3.1 Definitions—Definitions applicable to this practice are listed in Terminology D121.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 accuracy, n—(1) generally,generally, a term used to indicate the reliability of a sample, a measurement, or an observation;
(2) specifically, a measure of closeness of agreement between an experimental result and the true value.
3.2.1.1 Discussion—
An example is the observed and true sulfur content of a coal consignment. This measurement is affected by random errors as well
as by bias.
3.2.2 activation interval, n—for a falling-stream or cross-belt cutter, the time from the beginning of movement for taking an
increment, to the beginning of movement for taking of the next increment.
3.2.3 auger increment, n—the retained portion of one extraction operation of the auger.
3.2.4 auger sampler, n—a mechanical device that extracts a columnar sample of coal from a railcar, truck, barge, or stockpile and
any associated sub-system or within-system components.
3.2.5 bias, n—the difference between the population mean of the mechanical sampler test results and the accepted reference value.
3.2.6 confidence interval, n—a numeric interval with a lower limit and a higher limit within which the true parameter value is
estimated to fall; the confidence interval percentage indicates the percentage of time the true value will fall within the interval if
the procedure is continuously repeated.
3.2.7 consignment, n—a discrete amount of coal, such as a shipment, a car load, a unit train, or a day’s production.
3.2.7.1 Discussion—
A consignment may include more than one lot of coal and may correspond to a specific period of time, such as a sampling period
or a billing period.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
D7430/D7430M − 22
3.2.8 correlation, n—a measure of the linear dependence between paired system and reference measurements.
3.2.8.1 Discussion—
Correlation frequently is expressed by the correlation coefficient, which can take a value from minus one (perfect negative linear
relationship) to plus one (perfect positive linear relationship).
3.2.9 cross-belt sampler, n—a single sampling machine or component of a mechanical sampling system designed to extract an
increment directly from a conveyor belt surface by sweeping a sampling device (cutter) through the material on the conveyor.
3.2.10 delimitation error, n—a material error that occurs when all the elements in a cross section of a coal stream do not have an
equal probability of being intercepted (captured) by the sampler cutter during increment collection.
3.2.11 ellipsoidal region, n—an area that is formed by plane sections of ellipses that are defined by the values selected for the
largest tolerable bias of each coal characteristic used in the bias test; the region will be used to determine if the system is biased.
3.2.12 falling-stream sampler, n—a single sampling machine or component of a mechanical sampling system designed to extract
an increment from a falling stream of coal at the discharge end of a conveyor or chute by moving a sampling device (cutter) through
the falling stream of material.
3.2.13 Hotelling’s Squared T (T ) test, n—a statistical test that is used to evaluate multivariate data; it is the multivariate
equivalent of the Student’s t-test.
3.2.14 largest tolerable bias (LTB), n—an interval whose upper and lower bounds represent the limits of an acceptable bias.
3.2.15 mechanical sampling system, n—a single machine or series of interconnected machines whose purpose is to extract
mechanically, or process (divide and reduce), or a combination thereof, a sample of coal.
3.2.16 paired data set, n—system and reference values observed on samples collected and compared from the same batch of
material.
3.2.17 precision, n—a term used to indicate the capability of a person, an instrument, or a method to obtain reproducible results;
specifically, a measure of the random error as expressed by the variance, standard error, or a multiple of the standard error (see
Practice E177).
3.2.18 reference sample, n—a sample used in testing of a mechanical sampling system which is comprised of one or more
increments collected from the test batch or lot of coal by the stopped belt method as described in Practice D2234/D2234M.
3.2.19 reject stream, n—the coal flow within a mechanical sampling system, which occurs at each stage of division, before and
after reduction, and is not included in the system sample.
3.2.20 sampling ratio, n—the mass of the system sample divided by the mass of the corresponding coal sampled.
3.2.21 save stream, n—the coal flow within a mechanical sampling system which occurs at each stage of division, before and after
reduction, and after the final stage of division becomes the system sample.
3.2.22 statistical independence, n—two sample values are statistically independent if the occurrence of either one in no way affects
the probability assigned to the occurrence of the other.
3.2.23 surrogate sample, n—a sample, used in the evaluation of a mechanical sampling system, which is comprised of one or more
increments collected from a coal stream within the mechanical sampling system in accordance with Practice D2234/D2234M,
Conditions “A” or “B.”
3.2.23.1 Discussion—
Such a sample may be considered acceptable for evaluation of a mechanical sampling system’s components, excluding the primary
cutter, when demonstrated to be equivalent to the reference sample.
D7430/D7430M − 22
3.2.24 system sample, n—a sample collected from a test batch or lot of coal by the final stage of a mechanical sampling system.
3.2.25 unbiased sample (representative sample), n—a sample free of bias.
3.2.26 Walsh averages, n—given a series of observations (differences) x1, x2, . xn, the n (n + 1)/2 pair-wise averages given by:
xi1xj /2, 1# i # j # n (1)
~ !
3.2.26.1 Discussion—
As an example of Walsh averages, assume one has three observations (differences) designated as x1, x2, and x3. There are then
a total of 3(4)/2 = 6 Walsh averages. They are as follows: x1, x2, x3, (x1 + x2)/2, (x1 + x3)/2, and (x2 + x3)/2.
3.2.27 Wilcoxon Signed Rank Test, n—a non-parametric statistical procedure for calculating the point estimate and confidence
interval for a sample drawn from a population with symmetric distribution.
3.2.28 within-system preparation, n—the process of gross sample preparation carried out mechanically by sequential crushing
(reduction) equipment or division equipment, or both.
3.2.28.1 Discussion—
It may be carried out by processing increments individually or by batching increments together and processing them together as
a group. In any case, within-system preparation is conducted in a manner to minimize moisture changes and without removing the
gross sample or its increments from the sampling system.
D7430/D7430M − 22
PART A – MECHANICAL COLLECTION AND WITHIN-SYSTEM PREPARATION OF A GROSS SAMPLE OF
COAL FROM MOVING STREAMS
[Old Practice D7256/D7256M]
4. Scope
4.1 Part A—Mechanical Collection and Within-System Preparation of a Gross Sample of Coal from Moving Streams—Covers
procedures for the mechanical collection of a sample under Classification I-B-1 and I-B-2 (Practice D2234/D2234M) and the
within-system preparation (reduction and division) of gross samples utilizing various components of the mechanical sampling
system.
4.1.1 Part A describes mechanical sampling procedures for coals (1) by size and condition of preparation (for example,
mechanically cleaned coal or raw coal), and (2) by sampling characteristics.
4.1.2 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated
in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used
independently of the other, and values from the two systems shall not be combined.
4.1.3 In this practice, the term “mass” applies to measurements expressed with both SI units (for example, kg) and inch-pound
units (for example, lb).
5. Summary of Practices
5.1 The general-purpose sampling procedures are intended to provide, in 19 of 20 cases, dry ash results that are within an interval
of 6 ⁄10 of the average dry ash results that would be obtained in hypothetical repeated sampling.
5.2 Special-purpose sampling procedures apply to the sampling of coal when other precision limits are required, or when other
constituents are used to specify precision, or for performance tests.
5.3 For coals of known size and condition of preparation, a table (Table 1) is given for the determination of the number and mass
of increments required for a gross sample for both general- and special-purpose sampling.
5.4 The only processes of sample division and reduction covered in this document are the use of mechanical sample dividers for
the division of the sample and mechanical crushing equipment for the reduction of the sample, both of which are within-system
components of the mechanical sampling system.
5.5 The procedures appear in the following order:
Test Method Section
Sampling of Coals Based on Size and Condition 10.1
of Preparation
TABLE 1 Number and Mass of Increments for General-Purpose
A
Sampling Procedure
16 mm 50 mm 150 mm
Top Size
B
[0.625 in.] [2 in.] [6 in.]
C
Mechanically Cleaned Coal
Minimum number of 15 15 15
increments
Minimum mass of 1 [2] 3 [6] 7 [15]
increments, kg [lb]
C
Raw (Uncleaned Coal)
Minimum number of 35 35 35
increments
Minimum mass of 1 [2] 3 [6] 7 [15]
increments, kg [lb]
A
Conditions C and D are not addressed in this practice.
B
For coals above 150 mm [6 in.] top size, the sampling procedure should be
mutually agreed upon in advance by all parties concerned.
C
See 9.2.2.
D7430/D7430M − 22
Test Method Section
General-Purpose Sampling Procedure 10.1.1
Number and Mass of Increments 10.1.1.2
Number of Gross Samples 10.1.1.4
Special-Purpose Sampling 10.1.2
Number and Mass of Increments 10.1.2.2
Number of Gross Samples 10.1.2.3
Division of the Gross Sample Before Crushing 10.2
Reduction and Division 10.3
6. Significance and Use
6.1 It is intended that this practice be used to provide a sample representative of the coal from which it is collected. Because of
the variability of coal and the wide variety of mechanical sampling equipment available, caution should be used in all stages of
the sample collection process, the design of sampling system specifications, the equipment procurement, and the acceptance testing
of installed equipment.
6.2 After removal from the sampling system and further preparation (Practice D2013/D2013M), the sample may be analyzed for
a number of different parameters. These parameters may define the lot’s value, its ability to meet specifications, its environmental
impact, as well as other properties.
7. Hazards
7.1 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of
the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
7.2 Warning—The operation, inspection, maintenance, and cleaning of mechanical sampling equipment involves hazardous
operations, conditions, and equipment that may result in serious bodily harm or death. These hazards include, but are not limited
to, intermittent operation, remote startup, powerful electrical or hydraulic drives, moving conveyors, crushers, etc.
7.3 It is essential that personnel wear all required personal protective equipment. Personnel should be fully knowledgeable of, and
follow, all site-specific safety rules and governmental regulations regarding the equipment in question, including, but not limited
to, releasing stored energy, confined spaces, opening of inspection doors during operation, and electrical power lock out/tag out.
Be certain to de-energize main power source and not rely on local or control circuits.
8. Increment Collection Classification
8.1 The type of selection, the conditions under which individual increments are collected, and the method of spacing of increments
from the coal consignment or lot are classified according to the following descriptions and Table 1 in Practice D2234/D2234M.
8.2 Types of Increments—The only type of selection of increments covered by this document is Type I where there is no human
discretion in the selection of the pieces of coal or portions of the coal stream. Type I selection increments generally yield more
accurate results than Type II where human discretion is exercised in the selection of specific pieces of coal or of specific portions
of the stream, pile, or shipment.
8.3 Conditions of Increment Collection—The conditions under which individual increments are collected are the conditions of the
main body of coal relative to the portion withdrawn. Only Condition B (Full-Stream Cut), in which a full cross-section cut is
removed from a moving stream of coal, is covered by this document.
8.4 Spacing of Increments—The spacing of increments pertains to the kind of intervals between increments. Two spacing methods
are recognized: systematic and random. Systematic spacing is usually preferable.
8.4.1 Systematic Spacing 1, in which the movements of individual increment collection are spaced evenly in time or in position
over the lot. This practice allows both time-based and mass-based distribution of increments.
8.4.2 Random Spacing 2, in which the increments are spaced at random in time or in position over the lot.
D7430/D7430M − 22
9. Organization and Planning of Sampling Operations
9.1 This practice provides definitive procedures for the collection of a gross sample. Parties claiming to use this practice must
adhere to the procedures as set out in this practice. If the sampling is not done in accordance with the procedures set out in this
practice, then that sample may not be suitable for comparison with a sample collected by the procedures described in this practice.
Since it may be impracticable or impossible to take another sample of a given lot of coal, it is essential that parties agree on
sampling procedures prior to undertaking sampling.
9.2 Selection of Appropriate Sampling Procedure—Variations in coal-handling facilities make it impossible to publish rigid rules
covering every sampling situation in complete and exact detail. Proper sampling involves an understanding and proper
consideration of the minimum number and mass of increments, the size consist of the coal, the condition of preparation of the coal,
the variability of the constituent sought, and the degree of precision required.
9.2.1 Number and Mass of Increments—The number and mass of increments required for a given degree of precision depends
upon the variability of the coal. This variability increases with an increase in free impurity. A coal high in inherent impurity and
with comparatively little free impurity may exhibit much less variability than a coal with a low inherent impurity and a relatively
high proportion of free impurity. For most practical purposes, an increase in the ash content of a given coal usually indicates an
increase in variability. It is imperative that not less than the minimum specified number of increments of not less than the minimum
specified mass be collected from the lot.
9.2.2 Condition of Preparation—If there is any doubt as to the condition of preparation of the coal (for example, mechanically
cleaned coal or raw coal), the number of increments for raw coal shall apply. For the purpose of application of the minimum
number of increments in Table 1, mechanically cleaned coal is defined as coal which has been mechanically cleaned by a specific
gravity process in all sieve sizes above 150 μm mesh [No. 100 150 μm mesh [No. 100 USA] Standard. Similarly, although a coal
has been mechanically cleaned, it may still show significant variation. For example, the coal may be a blend of two different
portions of one seam or a blend of two different seams. In such cases where significant variation is possible, the number of
increments should be as specified for raw (uncleaned) coal.
9.3 Distribution of Increments—It is essential that the increments be distributed throughout the lot to be sampled. This distribution
is related to the entire volume of the lot, not merely its surface or any linear direction through it or over it. If circumstances prevent
the sampler from applying this principle, the lot is sampled only in part, and the gross sample is representative only of this part.
The spacing of the increments shall be varied if the possibility exists that increment collection may get “in phase” with the
sequence of coal variability. Example: routine sampling of commercial coal from a continuous stream (conveyor belt) in which
increment collection is automatic and its sequence coincides with the “highs” or “lows” in the content of fines.
9.3.1 Independence of Cutter Activation Intervals—Select cutter activation intervals so that cutters do not activate at a set time in
relation to the cutter from a previous stage. In addition, the activation interval for any sampling stage shall not be evenly divisible
into the previous stage activation interval.
9.4 Dimensions of Sampling Device—The opening of the sampling device shall be no less than 3.0 times the nominal top size of
the coal but no less than 31.8 mm [1.25 in.]31.8 mm [1.25 in.]
9.4.1 For systems installed prior to December 31, 2013, the opening of the sampling device may be 2.5 times the nominal top size
of the coal but no less than 31.8 mm [1.25 in.].31.8 mm [1.25 in.].
9.4.2 The sampling device shall be of sufficient capacity to completely retain or entirely pass the increment without spillage at the
maximum rate of coal flow.
9.5 Characteristics and Movement of Sampling Device—In sampling from moving streams of coal, the sampling device shall be
designed to collect each increment with no selective rejection of material by size and with no contamination by nonsample
material.
9.5.1 Falling-Stream Sampler—In collecting an increment, the falling-stream cutter moves at a constant velocity through the entire
cross section of the stream of coal. The edges of the cutter opening shall be at the same height and parallel along its length. The
mass, m, in kg [lb] of material collected in one pass through the stream by a falling-stream cutter, with cutting edges and cutter
velocity perpendicular to the stream flow, is calculated from the following equation:
D7430/D7430M − 22
NOTE 1—
(a) Reciprocating Cutter—Fig. 15(a) shows a section of a cutter which is moved across a stream of coal. At regular intervals, the cutter movement is
reversed and a sample increment is collected on each trip through the coal stream.
(b) Rotating Cutter—Fig. 15(b) shows two cutters attached to a hollow, rotating shaft. Each cutter is designed to extract increments from the feed and
to discharge these into the hollow shaft. One or more cutters may be used.
(c) Rotating Hopper and Spout—Fig. 15(c) shows the totaling hopper that receives the crushed sample and discharges it through a spout over one or
more stationary cutters.
(d) Rotating Cone—Fig. 15(d) shows a sampler developed by the British National Coal Board. Two slotted cones are locked together and rotated on
a vertical shaft so that on each revolution the common slot operating intercepts the falling stream of coal and collects an increment
FIG. 15 Mechanical Sample Dividers
Cw Cw
m 5 m 5 (2)
F G
3.6v 1.8v
c c
where:
C = stream flow rate in Mg/h [ton/h],
w = tip-to-tip cutter aperture width in mm [in.], and
v = average cutter speed in mm/s [in./s].
c
NOTE 1—Falling-stream cutter speeds of 460460 mm mm/s⁄s [18 in. [18 in./s] ⁄s] or less have been found to produce acceptable results.
D7430/D7430M − 22
NOTE 2—The constant value 3.6 [1.8] in the denominator of Eq 2 converts Mg/h to kg/s [ton/h to lb/s].
NOTE 3—If the falling-stream cutter velocity is not constant as it traverses the material stream, the mass of collected material may not agree with that
calculated using Eq 2.
9.5.1.1 An example of a falling-stream sampler is shown in Fig. 21.
9.5.2 Cross-Belt Sampler—Design and operate the cross-belt cutter at a velocity across the conveyor surface that is high enough
to prevent selective rejection of material by size, prevent contamination of the sample with material not collected within the cutter,
and avoid mechanical problems due to damming of conveyed material against the outside of the cutter body as the cutter travels
though the stream. Design the hopper or chute that receives the primary increment to include skirting or other barriers to prevent
the inclusion of non-sample material that is swept in its direction by the upstream side plate of the primary cutter. Furthermore,
ensure by design that a complete increment is extracted, and that the configuration of the conveyor belt fits the arc of travel of the
cross-belt cutter closely fits the configuration and prevents deflection of the conveyor belt. away from the primary cutter at the point
of sample collection. This can be accomplished with belt support devices which shape the conveyor into an arc at the point of
sample collection; and a wiper on the tip of the cutter to ensure collection of fine sized material (see Fig. 2 and Fig. 3). The mass,
m, in kg [lb], of material collected in one pass through the moving stream by a cutter with cutting edges and cutter velocity
perpendicular to the stream flow is calculated from the following equation:
Cw Cw
m 5 m 5 (3)
F G
3.6v 1.8v
b b
where:
C = stream flow rate in Mg/h [ton/h],
w = tip-to-tip cutter aperture width in mm [in.], and
v = conveyor belt speed in mm/s [in./s].
b
FIG. 21 Falling-Stream Sampler
D7430/D7430M − 22
FIG. 2 Cross Belt Sampler With Conveyor Arc Support
FIG. 3 Cross-belt Sampler Without Conveyor Arc Support
NOTE 4—The constant value 3.6 [1.8] in the denominator of Eq 3 converts Mg/h to kg/s [ton/h to lb/s].
D7430/D7430M − 22
NOTE 5—To avoid mechanical problems and spillage and to ensure correct sample delimitation, the higher ratio of cutter speed to belt speed the better.
Ratios of cutter speed to belt speed of 1.5 or greater have been found to produce acceptable results.
9.5.2.1 An example of a cross-belt sampler is shown in Fig. 34.
9.6 There shall be no structural member or other impediment within a cutter body that impedes either sample collection or sample
discharge.
9.7 Preservation of Moisture—The increments obtained during the sampling period shall be protected from changes in
FIG. 34 Cross-Belt Sampler
D7430/D7430M − 22
composition as a result of exposure to rain, snow, wind, sun, contact with absorbent materials, and extremes of temperature. The
circulation of air through equipment must be reduced to a minimum to prevent both loss of fines and moisture. Samples in which
moisture content is important shall be protected from excessive air flow and then shall be stored in moisture-tight containers. Metal
cans with airtight lids, or heavy vapor-impervious bags, properly sealed, are satisfactory for this purpose.
9.8 Contamination—The sampling arrangement shall be planned so that contamination of the increments with foreign material or
unrelated coal does not create bias of practical consequence.
9.9 Mechanical System Features—It is essential that mechanized systems as a whole, including sampling machines, chutes, feed
conveyors, crushers and other devices, be self-cleaning and non-clogging and be designed and operated in a manner that will
facilitate routine inspection and maintenance.
9.10 Personnel—Because of the many variations in the conditions under which coal must be sampled, and in the nature of the
material being sampled, it is essential that the samples be collected under the direct supervision of a person qualified by training
and experience for this responsibility.
9.11 Criteria of Satisfactory Performance—A satisfactory arrangement for mechanical collection and within-system preparation
of a gross sample of coal from a moving stream must properly apply the principles of systematic sampling. Use the instructions
in Part A to collect increments from the lot being sampled either at random or even intervals in such a manner that the quality and
size consist of each part of the lot has an equal probability of being represented in the sample. Use the instructions in Part C to
evaluate the mechanical performance of the system as a matter of routine, especially in regards to monitoring sampling ratios and
system inspections. Use the instructions in Part D to bias test the system using prescribed procedures and methods.
9.12 Relative Location of Sampling and Weighing—It is preferable that coal be weighed and sampled at the same time. If there
is a lapse in time between these two events, consideration should be given by both the purchaser and the seller to changes in
moisture during this interval and the consequent shift in relationship of moisture to the true quality of the coal at the instant when
ownership of the coal transfers from one to the other.
10. Procedures
10.1 Sampling of Coals Based on Size and Condition of Preparation:
10.1.1 General-Purpose Sampling:
10.1.1.1 Where probability sampling is employed, the general-purpose sampling procedures are intended to provide, in 19 of 20
cases, dry ash results that are within the interval of 6 ⁄10 of the average dry ash results that would be obtained in hypothetical
repeated sampling.
10.1.1.2 Number and Mass of Increments—Obtain the number and mass of increments as specified in Table 1, except as provided
in 10.1.1.5(2). Determine the minimum number of increments from the condition of preparation, and determine the minimum mass
of each increment from the top size of the coal. Classify the coals to be sampled according to the general purpose procedure into
three groups by top size. Further classify each of these groups into two subgroups in accordance with the condition of preparation.
These classifications are shown in Table 1.
10.1.1.3 Variations in construction of the sampling device and flow, structure, or size consist of the coal may make it impracticable
to collect increments as small as the minimum mass specified in Table 1. In such cases, collect an increment of greater mass.
However, do not reduce the minimum number of increments, regardless of large excesses of individual increment masses. Table
1 lists the absolute minimum number of increments for general-purpose sampling which may not be reduced, except as specified
in 10.1.1.5(2). Other considerations may make it advisable or necessary to increase this number of increments.
10.1.1.4 Number of Gross Samples—Under the general-purpose sampling procedure, for quantities up to approximately 1000 Mg
[1000 tons], 1000 Mg [1000 tons], it is recommended that one gross sample represent the lot. Take this gross sample in accordance
with the requirements prescribed in Table 1.
10.1.1.5 For quantities over 1000 Mg [1000 tons], 1000 Mg [1000 tons], use any of the following alternatives:
(1) Take one gross sample for the lot and analyze it to represent the quality of the lot. Collect the number of increments N
calculated from Eq 4:
D7430/D7430M − 22
L
N 5 K (4)
Œ
where:
L = number of Mg [tons], and
K = 15.7 [15] for mechanically cleaned coal or 36.7 [35] for raw coal.
(2) Divide the lot into sub-lots and take a separate gross sample from each sub-lot. Use Eq 4 to determine the minimum
number of increments for each sub-lot, with L being the sub-lot quantity. Mass-average the analyses of the sub-lot samples to
represent the quality of the original lot.
10.1.1.6 The maximum lot size shall be chosen by mutual agreement between the seller and the buyer of the coal, with each party
taking into account the risks associated with the choice. Potential consequences include:
(1) Large samples requiring excessive off-line preparation steps can result in sampling moisture losses.
(2) No quality information is obtained on within-lot variability. Lot sizes generally should not exceed quantities for which
critical quality levels apply in use of the coal.
(3) When a given quantity of coal that might be represented by a single lot is divided into multiple sub-lots, the imprecision
of the reported quality for that given quantity is reduced. For a given quantity, the component of imprecision due to sample
preparation and analysis is reduced by 1/=n, where n is the number of sub-lots.
10.1.2 Special-Purpose Sampling:
10.1.2.1 This special-purpose sampling procedure shall apply to the sampling of coal when increased precision is required, and
the only knowledge of the coal is its top size and conditions of preparation.
10.1.2.2 Number and Mass of Increments—Take the same number and mass of increments per gross sample as specified in Table
1, or as specified in 10.1.1.5(2).
10.1.2.3 Number of Gross Samples—To obtain increased precision for the final result for a given consignment, increase the number
of gross samples collected from that consignment and analyze each gross sample separately, reporting the average of results. To
reduce errors to one half, that is, to “double” the precision, take four times as many gross samples. Similarly, to reduce errors to
one third, to “triple” the precision, take nine times as many gross samples.
10.1.3 Sampling for Total Moisture Only:
10.1.3.1 The increments as established in Table 1 for mechanically cleaned coal are deemed adequate for general purpose
sampling for total moisture.
10.2 Division of the Gross Sample Before Crushing:
10.2.1 Large primary increments may be divided in quantity before crushing by secondary sampling. In the case of dividing a
primary increment before crushing, the minimum increment mass must meet the mass specified in Table 1 for the top size listed.
10.2.1.1 If each primary increment is reduced in quantity by secondary sampling, take at least six secondary increments from each
uncrushed primary increment. The method of collection of secondary increments must be proved to be free from bias. In no case
shall the mass of a secondary increment be less than shown in the schedule of Table 1.
10.3 Reduction and Division:
10.3.1 Reduce the gross or divided sample in stages and divide by suitable mechanical sample dividers (see 10.4.2) to quantities
not less than those shown in Table 1 of Practice D2013/D2013M.
10.3.2 Mechanical division of the sample consists of automatically collecting a large number of increments of the properly reduced
sample. Distribute this large number of increments equally throughout the entire discharge from the sample crusher because
crushers can introduce appreciable segregation. At each stage of division, take at least 60 increments.
NOTE 6—Reduction and division of the mechanical samples that do not involve within-system components of the mechanical sampling system are not
D7430/D7430M − 22
covered by this document but governed by Practice D2013/D2013M.
10.4 Reduction and Division Apparatus:
10.4.1 Crushers or Grinders—Jaw, cone, or rotary crusher; hammer mill; roll; or other suitable crusher to reduce the sample.
Design and operate crushers in a manner to minimize the effect of induced air circulation and thus the potential for drying the coal.
10.4.1.1 Hammer Mill—Completely enclosed to avoid loss of dust or moisture.
10.4.2 Sample Dividers: Mechanical—A mechanical sample divider using a reciprocating or rotating cutter, a rotating hopper and
spout, a rotating slotted cone, a reciprocating hopper and fixed cutter, bucket cutter with either bottom dump or inverting discharge,
slotted belt, rotary disk divider, mechanical stopped or moving belt sweeper, or other acceptable devices for dividing the sample.
Typical mechanical sample dividers are shown in Fig. 15. These illustrate various designs, but other acceptable designs are
available.
11. Maintenance of Mechanical Sampling System Equipment
11.1 Design a mechanical sampling system and its components to facilitate safe, thorough, and accessible inspection, cleaning, and
maintenance tasks. Safe access must take into consideration all site safety rules and which inspections can only be performed while
equipment is de-energized and isolated.
11.1.1 Ensure that component hatches and doors are adequate in design and located to provide access to key areas of the equipment
such as: (a) cutters or dividers in parked positions; (b) condition of high-wear items such as crusher hammers, bars and screens,
conveyor head and tail pulley wipers, conveyor and cutter throat skirting, or the wiping edge of cross-belt cutters or dividers; (c)
points of potential pluggage within the system; and (d) other items to that particular system.
11.1.2 Enable hatches and doors to be safely opened, closed, and secured, and include seals to prevent the introduction or escape
of air, or the introduction of moisture or contaminants into the component.
11.1.3 Provide adequate access to the sampling system (for example, using permanent walkways, stairways, ladders, platforms,
etc.) to allow personnel to work safely and effectively on and around the equipment.
11.2 To ensure reliable system performance, develop and consistently perform well-defined and planned system inspections, and
preventive and corrective maintenance action programs. This will help ensure continuous and reliable operation by detecting and
then repairing components that have undergone wear to a critical degree or that are affecting system performance. To maximize
the effectiveness of the preventive maintenance program and the detection of issues, conduct frequent measurements of key
components and parameters, and monitor sample weights and ratios.
11.2.1 It is good practice to have a documented maintenance program to guide the implementation of the maintenance work and
to record inspection dates, equipment hours, and maintenance performed. Design the program to include, at a minimum,
requirements recommended by equipment and component manufacturers for the frequency and specifics of inspection,
measurement, routine maintenance, and replacement when necessary. Execute the program on a scheduled basis (by calendar, by
hours of operation, by tonnage, or a combination thereof) depending on the sampling system’s frequency of use. An hour or
tonnage-based program allows for improved predictability of when to perform maintenance or equipment replacement.
11.2.2 It is good practice to include within the program a schedule for frequent and thorough cleaning of equipment to remove
material buildup, debris, or other contaminants, to minimize the potential for plugging, and to diminish the potential for long-term
corrosion or decay of equipment.
11.2.3 For monitoring sampling system crusher performance, use the method prescribed in Test Method D4749 to determine the
particle size distribution of crushed sample material to help prevent oversized material from passing to downstream cutters or
dividers. Inspect the crusher components, such as hammers, bars, and screens for wear. Worn crusher components can cause
moisture loss from the sample material due to an increase in the time the material stays in the crushing chamber. Inspect crusher
screens frequently and replace them promptly to prevent oversized particles from passing to downstream cutters or dividers.
11.3 Wear of mechanical components, or the failure to correct equipment not performing to specifications, may eventually cause
D7430/D7430M − 22
a sampling system which had previously shown no evidence of bias to no longer satisfy that criterion. Consistent maintenance and
inspection, along with the monitoring of sample weights and ratios, will help ensure that the sampling system maintains its
bias-tested performance.
12. Precision and Bias
12.1 The precision of the general-purpose sampling procedure, based on size and condition of preparation, is stated in 10.1.1.1.
If a different precision is required, see 10.1.2.
12.2 Mechanical sampling systems are tested for bias using the procedures of Part D.
D7430/D7430M − 22
PART B – MECHANICAL AUGER SAMPLING
[Old Practice D4916]
13. Scope
13.1 Part B—Mechanical Auger Sampling—Describes procedures for the collection of an increment, partial sample, or gross
sample of material using mechanical augers. Reduction and division of the material by mechanical equipment at the auger is also
covered. Further manual or mechanical reduction or division of the material elsewhere shall be performed in accordance with
Practice D2013/D2013M.
13.1.1 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated
in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used
independently of the other, and values from the two systems shall not be combined.
14. Summary of Practice
14.1 A sample of coal is extracted from a stationary load contained within a railcar(s), truck(s), or barge(s) by inserting an auger
into the vehicle in a vertical manner to extract a columnar sample of coal from the vehicle. Protect the coal collected by the auger,
or processed by additional sampling components, from moisture change and contamination by placing it into containers and sealing
them.
15. Significance and Use
15.1 Auger sampling systems may be used to extract samples from trucks, railcars, barges, or static compacted stockpiles where
the use of a full-stream mechanical sampling system may be impractical. The samples obtained from these systems can be used
to establish the materials’ commercial value or constituents for quality control purposes at the shipping or receiving location of
the interested parties in the transaction. The utilization of an auger system and procedures for collecting coal samples for
subsequent analysis should be agreed upon by all parties concerned. Compacted stockpiles should be no higher than the length of
the auger sampler. Otherwise, the deeper areas of the stockpile cannot be sampled.
16. Hazards
16.1 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
16.2 Warning—The operation, inspection, maintenance, and cleaning of mechanical sampling equipment involves hazardous
operations, conditions, and equipment that may result in serious bodily harm or death. These hazards include, but are not limited
to, intermittent operation, remote startup, powerful
...