GB/T 19494.1-2023 English PDF (GB/T19494.1-2023)

GB/T 19494.1-2023: Mechanical sampling of coal - Part 1: Method for sampling
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GB/T 19494.1-2023
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 73.040
CCS D 21
Replacing GB/T 19494.1-2004
Mechanical Sampling of Coal - Part 1: Method for Sampling
(ISO 13909-1:2016, Hard coal and coke - Mechanical sampling - Part 1: General
introduction; ISO 13909-2:2016, Hard coal and coke - Mechanical sampling - Part 2:
Coal - Sampling from moving streams; ISO 13909-3:2016, Hard coal and coke -
Mechanical sampling - Part 3: Coal - Sampling from stationary lots, NEQ)
ISSUED ON: NOVEMBER 27, 2023
IMPLEMENTED ON: MARCH 1, 2024
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 3
Introduction ... 4
1 Scope ... 5
2 Normative References ... 5
3 Terms and Definitions ... 5
4 General Requirements and Precision of Sampling ... 9
5 Establishment of Sampling Schemes ... 10
6 Moving Coal Flow Sampling Method ... 19
7 Stationary Coal Sampling Method ... 27
8 Packaging and Marking of Coal Sample ... 33
9 Sampling Report ... 34
Appendix A (informative) Examples of Calculation of the Number of Sampling Units
and the Number of Increments in Each Sampling Unit ... 35
Appendix B (normative) Evaluation of Mass-basis Sampling Equipment ... 37
Mechanical Sampling of Coal - Part 1: Method for Sampling
1 Scope
This document specifies the general requirements and precision of mechanized coal sampling,
the establishment of sampling schemes, the moving coal flow sampling method and stationary
coal sampling method, as well as packaging and marking of coal samples, and sampling reports.
This document is applicable to lignite, bituminous coal and anthracite coal.
2 Normative References
The contents of the following documents constitute indispensable clauses of this document
through the normative references in the text. In terms of references with a specified date, only
versions with a specified date are applicable to this document. In terms of references without a
specified date, the latest version (including all the modifications) is applicable to this document.
GB/T 3715 Terms Relating to Properties and Analysis of Coal
GB/T 19494.2 Mechanical Sampling of Coal - Part 2: Method for Sample Preparation
GB/T 19494.3 Mechanical Sampling of Coal - Part 3: Determination of Precision and Bias Test
3 Terms and Definitions
What is defined in GB/T 3715, and the following terms and definitions are applicable to this
document.
3.1 coal sample
A representative portion of coal taken for the purpose of determining certain properties.
3.2 test sample of coal
Sample prepared to satisfy specific test requirements.
NOTE: specimen for short.
3.3 common sample of coal
Coal sample taken for multiple tests.
3.4 moisture sample of coal
Coal sample specially taken for the determination of total moisture.
4 General Requirements and Precision of Sampling
4.1 General Requirements for Sampling
The purpose of coal sampling and sample preparation is to obtain a test sample of coal whose
test results can represent the entire lot of sampled coal.
The basic process of sampling and sample preparation is to first collect a considerable amount
of coal from many points distributed throughout the entire lot of coal, that is, primary
increments, then, directly merge (or merge after division) the various primary increments into
a gross sample, and finally, prepare the gross sample into the required number and type of test
samples of coal through a series of sample preparation procedures.
The basic requirement for sampling is that all particles of the sampled lot of coal can enter the
sampling equipment, and each particle has an equal probability of being collected into the coal
sample.
In all sampling, sample preparation and assay methods, errors always exist, and meanwhile, the
test results of any specified parameter obtained by such a method will also deviate from the true
value of this parameter. It is impossible to determine the absolute bias of a single result from
the “true value”, but only to estimate the precision of the test result. The degree of coincidence
between the results obtained from a series of determinations on the same coal is precision, and
the deviation of the average value of this series of determination results from an acceptable
reference value is bias (see GB/T 19494.3).
In order to ensure that the precision of the obtained test results of the specimens complies with
the requirements, the following factors shall be considered during sampling:
a) Variability of coal;
b) Number of gross samples taken from this lot of coal;
c) Number of increments for each gross sample;
d) Mass of specimen corresponding to the nominal maximum particle size.
It is of great importance to prevent bias in sampling, which may arise from:
a) Incorrect increment collection location or collection time;
b) Incorrect delimitation and / or collection of increments;
c) The collected coal sample loses its integrity.
In order to satisfy the basic requirements of sampling, the mechanized sampling method of
moving coal flow should be adopted; in places where conditions are unavailable, the
mechanized sampling method of stationary coal may also be adopted. However, no matter
variability of the sampled coal has increased, the sampling precision shall also be verified.
5.2.3 Determination of coal variability
5.2.3.1 Determination of variance of primary increments
The variance of primary increments depends on the variety of coal, the nominal top size, the
degree of processing and mixing, the absolute value of the parameter to be measured and the
mass of increments.
The variance of primary increments VI is obtained through one of the following methods:
a) Directly determine in accordance with one of the methods specified in GB/T 19494.3;
b) Determine based on the variance of increments determined for similar coals in similar
sampling systems;
c) In the absence of increment variance data, it can be assumed that VI = 20, then, verify
in accordance with one of the methods specified in GB/T 19494.3 after sampling.
5.2.3.2 Sample preparation and assay variance
The variance of sample preparation and assay VPT is obtained through one of the following
methods:
a) Directly determine in accordance with one of the methods specified in GB/T 19494.3;
b) Determine based on values measured for similar coal using similar sample preparation
procedures;
c) In the absence of sample preparation and assay variance data, it can be assumed that
VPT = 0.2, then, verify in accordance with one of the methods specified in GB/T
19494.3 after sample preparation and assay.
5.2.4 Number of sampling units and number of increments
5.2.4.1 Overview
Theoretically speaking, the number of increments taken from a lot of coal to obtain a specific
sampling precision is a function of the quality variability of that lot of coal, which has nothing
to do with the size of that lot of coal. However, in practice, due to the serial correlation of coal,
it is related to the quantity of coal. A lot of coal can be used as a whole sampling unit, or it can
be divided into several sampling units, and a gross sample is taken from each sampling unit.
For the following purposes, a lot of coal should be divided into several sampling units:
a) Improve the sampling precision to achieve the required value;
b) Maintain the integrity of the specimen, that is, avoid bias after the specimen is
ma---the absolute minimum increment mass, expressed in (kg);
d---the nominal top size of the sampled coal, expressed in (mm).
6 Moving Coal Flow Sampling Method
6.1 General Rules
The moving coal flow sampling is carried out in a time-basis or mass-basis systematic sampling
mode or a stratified random sampling mode. From the perspective of operational convenience
and economy, time-basis sampling is preferred.
During sampling, it shall be ensured that a complete cross-section of the coal flow is intercepted
as an increment, and the increments shall not fill the sampler or overflow from the sampler.
The specimen shall be taken from the coal flow with a uniform flow rate and load as much as
possible. Try to avoid the load and quality change cycles of the coal flow coinciding with the
operating cycle of the sampler, so as to avoid sampling bias. If this cannot be avoided, then, the
mode of stratified random sampling shall be adopted.
6.2 Systematic Sampling
6.2.1 Time-basis sampling
6.2.1.1 Primary increment collection method
The primary increments are taken at preset time intervals. The first increment is randomly taken
within the first time interval, and the remaining increments are taken at equal time intervals.
During the entire sampling, the velocity of the sampler across the coal flow shall remain
consistent. If the pre-calculated number of increments has been collected, but the coal flow in
the sampling unit has not finished, then, sampling shall continue at the same time interval, until
the coal flow finishes.
6.2.1.2 Sampling interval
Each increment shall be uniformly distributed in the entire sampling unit, and the time interval
T between each primary increment is calculated in accordance with Formula (14):
Where,
T---the time interval between each primary increment, expressed in (min);
m---the mass of coal in the sampling unit, expressed in (t);
G---the maximum coal flow rate, expressed in (t/h);
the coal flow rate. The cutting velocity of each increment is different, but the velocity
is stable during the cutting of a single increment.
b) Use a fixed-velocity sampler with a division device. The collected increments are
divided to a fixed mass, then merged into the gross sample.
NOTE: Method a) is applicable to downflow samplers; Method b) is applicable to cross-belt
samplers.
6.3 Stratified Random Sampling
6.3.1 Basic requirements
The quality of coal may periodically change during the sampling, and its change period shall
not coincide with the increment collection period, otherwise, it may cause unacceptable
sampling bias. For this purpose, stratified random sampling can be adopted.
Stratified random sampling refers to randomly taking an increment within the mass or time
interval divided by mass-basis sampling or time-basis sampling. Stratified random sampling
does not take increments at equal time or mass intervals, instead, it takes increments at random
times or masses within previously divided time or mass intervals.
In stratified random sampling, two increments belonging to different time or mass intervals are
likely to be very close, so the coal unloading box of the primary sampler shall be able to
accommodate at least two increments.
6.3.2 Time-basis stratified random sampling
In accordance with the stipulations of 6.2.1.2 and 6.2.1.3, respectively calculate the sampling
time interval and increment mass.
Divide each time interval from 0 to an interval time number into several segments (s or min),
then, use random methods, for example, drawing lots, to determine the sampling time period
within each time interval, and draw increments at this time number.
6.3.3 Mass-basis stratified random sampling
In accordance with the stipulations of 6.2.2.2 and 6.2.2.3, respectively calculate the sampling
mass interval and increment mass.
Divide each mass interval from 0 to a mass interval number into several segments (t), then, use
random methods, for example, drawing lots, to determine the sampling mass period within each
mass interval, and draw increments at this mass number.
6.4 Reference Sampling
The reference method for coal flow sampling is the stop-belt sampling method, which is only
used when conducting sampling system error tests. This method shall comply with the
stipulations of GB/T 19494.3.
6.5 Moving Coal Flow Sampling Machinery
6.5.1 Basic requirements
The basic conditions for mechanized samplers are as follows:
a) They shall be able to collect increments without relevant bias and conduct tests in
accordance with the stipulations of GB/T 19494.3 to prove it;
b) They shall be able to maintain their working competence under specified conditions.
In order to achieve the above-mentioned conditions, the design and production of the samplers
shall satisfy the following requirements:
a) They shall be reliable enough to work under the worst foreseeable conditions;
b) There shall be sufficient capacity to collect the entire increment or allow it to pass
through without any loss or overflow;
c) They shall be self-cleaning, trouble-free, and require minimal maintenance during
operation;
d) They can avoid coal sample contamination, such as: the entry of impurities during
shutdown and the retention of originally sampled coal when changing to another coal
variety;
e) Changes in the physical and chemical properties of the sampled coal, such as:
moisture and pulverized coal loss, and particle size reduction in the particle size
analysis sample are minimized.
6.5.2 Design of downflow samplers
6.5.2.1 Basic requirements
The sample cutter shall satisfy the following requirements.
a) The cutter can intercept a complete cross-section of the coal flow.
b) The front and rear edges of the cutter shall be on the same plane or cylindrical surface.
The plane or cylindrical surface is preferably perpendicular to the average trajectory
of the coal flow.
c) The cutter shall pass through the coal flow at a uniform velocity, and the cutting
velocity at any point shall not change by more than 5% of the pre-determined
reference cutting velocity.
d) The opening of the cutter shall be designed so that all parts of the coal flow pass
The increments are collected using the sampler specified in 7.4. During sampling, the sampler
shall be inserted into the coal to take a full-depth coal pillar of increment from the top to the
bottom, or it shall be inserted into the coal to a certain depth and take out a stratified increment
when it can ensure that the quality of coal in the carrier is uniform and there is no stratified ...