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GB/T 19494.2-2023 English PDF (GBT19494.2-2023)
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GB/T 19494.2-2023: Mechanical sampling of coal - Part 2: Method for sample preparation
GB/T 19494.2-2023
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 73.040
CCS D 21
Replacing GB/T 19494.2-2004
Mechanical Sampling of Coal - Part 2: Method for Sample
Preparation
(ISO 13909-1:2016, Hard coal and coke - Mechanical sampling - Part 1:
General introduction; ISO 13909-4:2016, Hard coal and coke - Mechanical
Sampling - Part 4: Coal - Preparation of Test Sample, 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 ... 5
1 Scope ... 6
2 Normative References ... 6
3 Terms and Definitions ... 6
4 Precision of Coal Sample Preparation ... 7
5 Specimen Composition ... 8
6 Division ... 10
7 Reduction ... 27
8 Mixing ... 28
9 Air-drying ... 28
10 Preparation of Various Coal Samples ... 29
11 Coal Sample for Back-check ... 38
12 Design Requirements for Sample Preparation Equipment ... 38
Mechanical Sampling of Coal - Part 2: Method for Sample
Preparation
1 Scope
This document specifies the precision of coal sample preparation, specimen composition,
division, reduction, mixing and air-drying, as well as the preparation of various coal samples,
coal sample for back-check and the design requirements for sample preparation equipment.
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 211 Determination of Total Moisture in Coal
GB/T 19494.1 Mechanical Sampling of Coal - Part 1: Method for Sampling
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 19494.1, and the following terms and definitions are applicable to this
document.
3.1 sample preparation
The process of bringing coal samples to analysis or testing status.
NOTE: sample preparation includes mixing, reduction and division, and sometimes air-drying. It
can be carried out in several stages.
3.2 on-line sample preparation
Samples are prepared using equipment integrated into the sampling system.
3.3 off-line sample preparation
Use equipment that is not integrated with the mechanized sampling system to prepare coal
samples taken by the mechanical sampling system by manual or mechanized methods.
Where,
PL---the precision estimated (absolute) value of the determination results;
V1---the primary sub-sample variance;
n---the number of sub-samples in each sampling unit;
VPT---the sample preparation and assay variance;
m---the number of sampling units.
The precision of coal sample preparation is the total precision of sample preparation and assay
of a batch of coal under a confidence probability of 95%, which is recorded as VPT when
expressed as the sample preparation and assay variance. A relatively small sample preparation
and assay variance can improve sampling precision or reduce the number of primary sub-
samples.
Sample preparation and assay error almost entirely arises from the process of division and
extraction of several grams of coal sample from the analyzed coal sample. The most important
factors affecting the precision of sample preparation are the uniformity of coal sample before
division and the amount of coal sample retained after division, as well as the number of cuts,
the size of the cut and all particles of the divided coal sample, which have an equal probability
of being cut during the mechanical division. The sample preparation procedures specified in
this document can make the sample preparation and assay variance VPT expressed in ash content
or moisture less than 0.2. If mechanical sample preparation equipment is used, the sample
preparation and assay precision may be better.
For some sample preparation schemes, the limitations of actual conditions may prevent the
sample preparation and assay variance from reaching such a low level. Under this circumstance,
the user shall improve the sampling schemes or divide the coal batch into more sampling units
to achieve the expected total precision of sampling and preparation.
The target value of the sample preparation and assay variance VPT expressed in ash content or
moisture is 0.05PL2. The total error of sample preparation and assay, as well as the error
(expressed as variance) generated in each stage can be inspected by the method specified in
GB/T 19494.3.
5 Specimen Composition
5.1 Overview
A specimen is generally merged by many individual sub-samples, or all sub-samples of the
entire sampling unit, or a part of sub-samples of a sampling unit. Under certain circumstances,
such as: particle size analysis and bias test, a sub-sample constitutes a specimen.
Sub-sample merging procedures vary with the sampling mode---time-based sampling or mass-
(see Chapter 6).
5.2.2 Mass-based sampling
If the mass of the primary sub-samples is close to uniform (that is, the coefficient of variation
of the sub-sample mass is less than 20%, and there is no correlation between the sub-sample
mass and the coal flow rate, see GB/T 19494.1), then, the primary sub-samples can be merged
into a specimen, or directly merged, or merged after the primary sub-samples are divided by
the fixed ratio division method to a certain stage (see Chapter 6).
If the mass of the primary sub-samples is non-uniform, then, they shall be divided by the fixed
mass division method to a certain mass, then, merged into a specimen.
5.3 Specimen Merging
During specimen merging, the mass of each specimen shall be proportional to the mass of each
sampled coal, so that the quality parameter value of the merged specimen is the weighted
average value of the quality parameter value of each merged specimen. The division of each
specimen before merging shall adopt the fixed ratio division method (see Chapter 6).
6 Division
6.1 Basic Requirements
Division is the most critical procedure in sample preparation, and its purpose is to reduce the
amount of coal sample. The division of coal sample can be carried out online or offline using
mechanical methods, or manually. Whenever the conditions permit, mechanical division shall
be applied, so as to minimize human error.
The mechanical divider removes a part or several parts from the coal sample by cutting the coal
sample. When the mass of the coal sample after one division is greater than the required amount,
the divided coal sample can be further divided using the original divider or the next divider.
When the coal sample is obviously wet and cannot smoothly pass through the divider or sticks
to the surface of the divider, before division, it shall be air-dried in accordance with the
stipulations of 10.2.2.
When mechanical division causes the integrity of the coal sample to be compromised, such as:
moisture loss and particle size reduction, etc., the method of manual division shall be adopted.
However, care shall be taken because the manual method itself may cause bias, especially when
the amount of the divided coal sample is relatively large.
Regular...
Get QUOTATION in 1-minute: Click GB/T 19494.2-2023
Historical versions: GB/T 19494.2-2023
Preview True-PDF (Reload/Scroll if blank)
GB/T 19494.2-2023: Mechanical sampling of coal - Part 2: Method for sample preparation
GB/T 19494.2-2023
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 73.040
CCS D 21
Replacing GB/T 19494.2-2004
Mechanical Sampling of Coal - Part 2: Method for Sample
Preparation
(ISO 13909-1:2016, Hard coal and coke - Mechanical sampling - Part 1:
General introduction; ISO 13909-4:2016, Hard coal and coke - Mechanical
Sampling - Part 4: Coal - Preparation of Test Sample, 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 ... 5
1 Scope ... 6
2 Normative References ... 6
3 Terms and Definitions ... 6
4 Precision of Coal Sample Preparation ... 7
5 Specimen Composition ... 8
6 Division ... 10
7 Reduction ... 27
8 Mixing ... 28
9 Air-drying ... 28
10 Preparation of Various Coal Samples ... 29
11 Coal Sample for Back-check ... 38
12 Design Requirements for Sample Preparation Equipment ... 38
Mechanical Sampling of Coal - Part 2: Method for Sample
Preparation
1 Scope
This document specifies the precision of coal sample preparation, specimen composition,
division, reduction, mixing and air-drying, as well as the preparation of various coal samples,
coal sample for back-check and the design requirements for sample preparation equipment.
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 211 Determination of Total Moisture in Coal
GB/T 19494.1 Mechanical Sampling of Coal - Part 1: Method for Sampling
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 19494.1, and the following terms and definitions are applicable to this
document.
3.1 sample preparation
The process of bringing coal samples to analysis or testing status.
NOTE: sample preparation includes mixing, reduction and division, and sometimes air-drying. It
can be carried out in several stages.
3.2 on-line sample preparation
Samples are prepared using equipment integrated into the sampling system.
3.3 off-line sample preparation
Use equipment that is not integrated with the mechanized sampling system to prepare coal
samples taken by the mechanical sampling system by manual or mechanized methods.
Where,
PL---the precision estimated (absolute) value of the determination results;
V1---the primary sub-sample variance;
n---the number of sub-samples in each sampling unit;
VPT---the sample preparation and assay variance;
m---the number of sampling units.
The precision of coal sample preparation is the total precision of sample preparation and assay
of a batch of coal under a confidence probability of 95%, which is recorded as VPT when
expressed as the sample preparation and assay variance. A relatively small sample preparation
and assay variance can improve sampling precision or reduce the number of primary sub-
samples.
Sample preparation and assay error almost entirely arises from the process of division and
extraction of several grams of coal sample from the analyzed coal sample. The most important
factors affecting the precision of sample preparation are the uniformity of coal sample before
division and the amount of coal sample retained after division, as well as the number of cuts,
the size of the cut and all particles of the divided coal sample, which have an equal probability
of being cut during the mechanical division. The sample preparation procedures specified in
this document can make the sample preparation and assay variance VPT expressed in ash content
or moisture less than 0.2. If mechanical sample preparation equipment is used, the sample
preparation and assay precision may be better.
For some sample preparation schemes, the limitations of actual conditions may prevent the
sample preparation and assay variance from reaching such a low level. Under this circumstance,
the user shall improve the sampling schemes or divide the coal batch into more sampling units
to achieve the expected total precision of sampling and preparation.
The target value of the sample preparation and assay variance VPT expressed in ash content or
moisture is 0.05PL2. The total error of sample preparation and assay, as well as the error
(expressed as variance) generated in each stage can be inspected by the method specified in
GB/T 19494.3.
5 Specimen Composition
5.1 Overview
A specimen is generally merged by many individual sub-samples, or all sub-samples of the
entire sampling unit, or a part of sub-samples of a sampling unit. Under certain circumstances,
such as: particle size analysis and bias test, a sub-sample constitutes a specimen.
Sub-sample merging procedures vary with the sampling mode---time-based sampling or mass-
(see Chapter 6).
5.2.2 Mass-based sampling
If the mass of the primary sub-samples is close to uniform (that is, the coefficient of variation
of the sub-sample mass is less than 20%, and there is no correlation between the sub-sample
mass and the coal flow rate, see GB/T 19494.1), then, the primary sub-samples can be merged
into a specimen, or directly merged, or merged after the primary sub-samples are divided by
the fixed ratio division method to a certain stage (see Chapter 6).
If the mass of the primary sub-samples is non-uniform, then, they shall be divided by the fixed
mass division method to a certain mass, then, merged into a specimen.
5.3 Specimen Merging
During specimen merging, the mass of each specimen shall be proportional to the mass of each
sampled coal, so that the quality parameter value of the merged specimen is the weighted
average value of the quality parameter value of each merged specimen. The division of each
specimen before merging shall adopt the fixed ratio division method (see Chapter 6).
6 Division
6.1 Basic Requirements
Division is the most critical procedure in sample preparation, and its purpose is to reduce the
amount of coal sample. The division of coal sample can be carried out online or offline using
mechanical methods, or manually. Whenever the conditions permit, mechanical division shall
be applied, so as to minimize human error.
The mechanical divider removes a part or several parts from the coal sample by cutting the coal
sample. When the mass of the coal sample after one division is greater than the required amount,
the divided coal sample can be further divided using the original divider or the next divider.
When the coal sample is obviously wet and cannot smoothly pass through the divider or sticks
to the surface of the divider, before division, it shall be air-dried in accordance with the
stipulations of 10.2.2.
When mechanical division causes the integrity of the coal sample to be compromised, such as:
moisture loss and particle size reduction, etc., the method of manual division shall be adopted.
However, care shall be taken because the manual method itself may cause bias, especially when
the amount of the divided coal sample is relatively large.
Regular...
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