GB/T 19494.2-2004 English PDF (GBT19494.2-2004)

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GB/T 19494.2-2004: Mechanical sampling of coal -- Part 2: Method for sample preparation
GB/T 19494.2-2004
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 73.040
D 21
Mechanical sampling of coal -
Part 2: Method for sample preparation
(ISO 13909-1:2001 Hard coal and coke - Mechanical sampling - Part 1:
General introduction, ISO 13909-4:2001 Hard coal and coke - Mechanical
sampling - Part 4: Coal - Preparation of test samples, NEQ)
ISSUED ON: APRIL 30, 2004
IMPLEMENTED ON: OCTOBER 01, 2004
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine;
Standardization Administration of PRC;
Table of Contents
Foreword ... 3 
1 Scope ... 5 
2 Normative references ... 5 
3 Terms and definitions ... 6 
4 Precision of sample preparation ... 7 
5 Composition of samples ... 8 
6 Division ... 9 
7 Reduction ... 23 
8 Mixing ... 24 
9 Air drying ... 24 
10 Preparation of various coal samples ... 25 
11 Coal samples retained for reference ... 32 
12 Design of sample preparation equipment ... 32 
Mechanical sampling of coal -
Part 2: Method for sample preparation
1 Scope
This part of GB/T 19494 specifies the terms and definitions for coal sample
preparation; the composition, division, reduction, mixing, air drying of samples;
the preparation of various coal samples; the design of reference coal samples
and sample preparation equipment.
This part applies to lignite, bituminous and anthracite.
2 Normative references
The provisions in following documents become the provisions of this part
through reference in this part of GB/T 19494. For the dated references, the
subsequent amendments (excluding corrections) or revisions do not apply to
this part; however, parties who reach an agreement based on this part are
encouraged to study if the latest versions of these documents are applicable.
For undated references, the latest edition of the referenced document applies.
GB/T 211 Determination of full moisture in coal (GB/T 211-1996, eqv ISO
589:1981)
GB/T 19494.1 Mechanical sampling of coal - Part 1: Method for sampling
(GB/T 19494.1-2004, ISO13909-1:2001 Hard coal and coke - Mechanical
sampling -Part 1: General introduction, ISO 13909-2:2001 Hard coal and
coke -Mechanical sampling - Part 2: Coal - Sampling from moving streams,
ISO 13909-3:2001 Hard coal and coke - Mechanical sampling - Part 3: Coal
-Sampling from stationary lots, NEQ)
GB/T 19494.3 Mechanical sampling of coal - Part 3: Determination of
precision and bias test (GB/T 19494.3-2004, ISO 13909-7:2001 Hard coal
and coke - Mechanical sampling - Part 7: Methods for determining the
precision of sampling, sample preparation and testing, ISO 13909-8:2001
Hard coal and coke - Mechanical sampling - Part 8: Methods of testing for
bias, NEQ)
3 Terms and definitions
The terms and definitions as specified in GB/T 19494.1 and the following terms
and definitions apply to this part.
3.1
Sample preparation
The process of bringing a coal sample to an analytical or experimental state.
Note: Sample preparation includes mixing, reduction, division, and
sometimes air drying. It can be done 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
The coal sample taken by the mechanical sampling system is manually or
mechanically prepared by the use of equipment that is not integrated with
the mechanical sampling system.
3.4
Sample division
Sample preparation process of dividing the sample into representative,
separated parts.
3.5
Fixed mass division
Division method with constant retained sample mass and independent of the
mass of the divided sample.
3.6
Fixed ratio division
A method of division with a certain division ratio, that is, the amount of
samples retained is proportional to the amount of samples to be divided.
samples. The most important factors affecting the precision of sample
preparation are the homogeneity of the coal sample before the division and the
remaining amount of the coal sample after the division. The sample preparation
procedures specified in this standard can make the variance of sample
preparation and assay VPT as expressed by ash or moisture be below 0.2. If
mechanical sample preparation equipment is used, sample preparation and
assay precision may be better.
The errors (represented by variance) at each stage of sample preparation and
assay can be tested by the method specified in GB/T 19494.3.
5 Composition of samples
5.1 Overview
A sample is generally composed of many single sub-samples, or synthesized
from all the sub-samples of the entire sampling unit, or synthesized from a part
of the sub-samples of a sampling unit. In some cases, such as particle size
analysis and bias test, a sub-sample constitutes a specimen.
The subsample merging procedure varies depending on the sampling method
- time-based sampling or mass-based sampling (see 5.2).
A specimen may also be a combination of several smaller specimens (see 5.3).
5.2 Merging of subsamples
5.2.1 Time-based sampling
The mass of the sub-samples in time-based sampling is proportional to the coal
flow during sampling. At this time, the sample can be directly combined from
the primary sub-samples, or can be combined from the post-division sub-
samples that have been prepared to a certain stage by the fixed ratio division
method (see 6).
5.2.2 Mass-based sampling
If the mass of the primary sub-samples is nearly uniform (that is, the coefficient
of variation of the mass of the sub-samples is less than 20%, meanwhile there
is no correlation between the mass of the sub-samples and the coal flow rate -
see GB/T 19494.1 Appendix B), the primary sub-samples can be combined into
a sample, or combined directly, or combine the primary sub-samples after
dividing it into a certain stage by using the fixed ratio division method (see 6).
If the mass of the primary sub-samples is not uniform, they shall be divided to
a certain mass according to the fixed mass division method and then combined
into a specimen (see 7).
Where:
mSO - The mass of the specimen after division at a given nominal maximum
particle size as specified in Table 1, in kilogram (kg);
PO - The precision of a given division stage as specified in Table 1;
PR - Precision required for a given division stage.
When a coal is routinely sampled in the same environment, the precision of all
required quality parameters shall be checked as much as possible (see GB/T
19494.3), meanwhile the mass of the specimen after division shall be adjusted,
but its mass must not be less than the minimum required by the relevant
analytical method standard.
When preparing coal samples for various purposes, the required mass and
particle size composition of each sample shall be fully considered.
6.3 Artificial division method
6.3.1 Riffle
The riffle is a simple and effective divider (the structure is shown in Figure 4). It
consists of two sets of oppositely arranged grid slots and receivers. The number
of slots on both sides is equal, at least 8 on each side. The size of the cell
opening is at least 3 times the nominal maximum particle size of the specimen.
The inclination of the slot to the horizontal plane is at least 60°. In order to
prevent the loss of pulverized coal and moisture, the receiver and the main body
of the riffle shall be closely matched, preferably closed.
When division, the s...