Path: Home > GB/T > Page570 > GB/T 19494.3-2023 || Home > Standard_List > GB/T > Page570 > GB/T 19494.3-2023
GB/T 19494.3-2023 English PDF
Price & DeliveryUS$895.00 · In stock · Download in 9 secondsGB/T 19494.3-2023: [Including 2025XG1] Mechanical sampling of coal - Part 3: Determination of precision and bias test Delivery: 9 seconds. True-PDF full-copy in English & invoice will be downloaded + auto-delivered via email. See step-by-step procedureStatus: Valid
GB/T 19494.3: Evolution and historical versions
| Standard ID | Contents [version] | USD | STEP2 | [PDF] delivery | Name of Chinese Standard | Status |
| GB/T 19494.3-2023 | English | 895 |
Add to Cart
|
0-9 seconds. Auto-delivery
|
[Including 2025XG1] Mechanical sampling of coal - Part 3: Determination of precision and bias test
| Valid |
| GB/T 19494.3-2004 | English | 1759 |
Add to Cart
|
7 days
|
Mechanical sampling of coal -- Part 3: Determination of precision and bias test
| Obsolete |
Excerpted PDFs (Download full copy in 9 seconds upon purchase)PDF Preview: GB/T 19494.3-2023
GB/T 19494.3-2023: [Including 2025XG1] Mechanical sampling of coal - Part 3: Determination of precision and bias test
---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GBT19494.3-2023
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 73.040
CCS D 21
Replacing GB/T 19494.3-2004
Mechanical sampling of coal -- Part 3.Determination of
precision and bias test
(ISO 13909-7.2016, Hard coal and coke -- Mechanical sampling -- Part 7.Methods
for determining the precision of sampling, sample preparation and testing; ISO 13909-
8.2016, Hard coal and coke -- Mechanical sampling -- Part 8.Methods of testing for
bias, NEQ)
Issued on: NOVEMBER 27, 2023
Implemented on: MARCH 01, 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 Sampling, sample preparation, and precision determination of laboratory tests... 6
5 Bias test methods... 33
Annex A (informative) Examples of bias test calculation... 54
Bibliography... 67
Mechanical sampling of coal -- Part 3.Determination of
precision and bias test
1 Scope
This document specifies the methods for mechanized sampling, sample preparation,
and precision determination of coal analysis, as well as bias testing methods.
This document applies to the precision determination and bias test of mechanized coal
sampling.
2 Normative references
The following referenced documents are indispensable for the application of this
document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
GB/T 19494.1, Mechanical sampling of coal - Part 1.Method for sampling
GB/T 19494.2, Mechanical sampling of coal - Part 2.Method for sample
preparation
3 Terms and definitions
For the purposes of this document, the terms and definitions defined in GB/T 19494.1
and GB/T 19494.2 apply.
4 Sampling, sample preparation, and precision determination
of laboratory tests
4.1 Overview
When designing a sampling scheme with acceptable precision, there needs to be a
correlation between precision and coal characteristics and sampling characteristics. The
main correlation factors are coal variability (i.e., subsample variance), sample
preparation and testing errors, number of subsamples and total number of samples, and
specimen quality.
There are several methods for estimating precision, depending on the purpose of
sampling and the sampling scheme and equipment used. There are two main cases.
a) For existing sampling systems, the purpose of testing is to check whether the
sampling scheme can actually achieve the desired precision. If it cannot, it needs
to be improved until the precision reaches the desired value. The most rigorous
method for verifying the precision of routine sampling schemes is double
sampling with multiple sampling units (see 4.4.1).
b) For a specific batch of coal, the purpose of the test is to estimate the achievable
precision from the actual test results. In this case, the best method is the multiple
sampling method (see 4.4.2).
The precision calculation formula presented in this document is based on the following
assumptions. the quality variation of the sampled coal is random; and the quality
observations are normally distributed. Although these two assumptions are not very
accurate for some coal quality parameters, the degree of deviation between the actual
state and the assumed state has no practical impact on the validity of the precision
verification formula, because the statistical methods used in this document are not very
sensitive to non-normal distributions.
Coal quality often exhibits a certain serial correlation, meaning that adjacent coals tend
to have similar compositions, while coals that are far apart tend to have dissimilar
compositions. The variance of the primary subsample obtained from tests may differ
from the actual variance; therefore, the precision estimates obtained from the primary
subsample variance and the variances of sample preparation and analysis will also differ
from the actual results.
4.2 Relationship between sampling, sample preparation, overall precision of
analysis, and its influencing factors
4.2.1 Overview
Precision is the degree of agreement between results obtained by repeatedly performing
a measurement procedure under specified conditions. It is a characteristic of the
measurement method used. The smaller the random error of a method, the higher its
precision. The precision value is usually taken as twice the population standard
deviation.
If j total samples are taken from a sampling unit and prepared and tested separately, the
estimation precision P of a single observation is calculated according to formula (1).
Where,
4.5 Sample preparation and testing error verification
4.5.1 Overview
The sample preparation and testing precision verification methods provided in this
clause are used to estimate the random errors (expressed as variance) at each stage of
sample preparation, including the total variance of sample preparation and testing and
the variance of each stage.
Each sample preparation stage generally includes steps such as crushing, mixing, and
reduction. Sample preparation errors mainly arise from the reduction process and the
final sampling of a certain number of grams from the test specimen. The most important
factors affecting reduction error are the particle size distribution of the specimen before
reduction and the amount of specimen retained after reduction.
Since ash content is the most sensitive parameter to coal particle size distribution, as
long as the ash content variance meets the requirements, other parameters in industrial
analysis and elemental analysis will generally also meet the requirements. However,
total moisture and calorific value may need to be verified. Therefore, this clause uses
ash content as an example for description. In actual verification, all coal quality
parameters can be verified if necessary.
NOTE. These methods were originally designed for manual and non-integrated mechanical
preparation. If sample preparation is performed in an integrated primary sampling/preparation
system, the error of individual components may be difficult to determine. While it can be measured
manually, such as by refeeding discarded material into the system, these methods are not
representative of normal operation. Therefore, the variance of the entire sample preparation stage
may have to be measured together with the variance of the primary subsample.
4.5.2 Target values of sample preparation and testing variance
4.5.2.1 Basic requirements
The total variance VPT estimated according to procedure 4.5.3 can be judged by a target
value. is generally proposed by the sample preparation technician, but shall
meet the requirements of GB/T 19494.2.Individual reduction errors shall be estimated
directly, judged by a target value or as part of the total variance.
Roughly estimated, the variance of a reduction stage is generally twice the variance of
the test. Therefore, the total variance of a 3-stage sample preparation-testing
procedure can be allocated in a 2.2.1 ratio to the variances of the two reduction stages
and the variance of the test.
The final target variance value for the final testing stage can be obtained from the
relevant analytical test method standards according to formula (18).
Where,
r - the repeatability limit for analyzing the test method.
4.5.2.2 Offline sample preparation
The coal sample preparation method specified in GB/T 19494.2 requires that, under the
condition that the sample quantity meets the requirements, the variance of ash content
preparation and analysis shall be below 0.2.For most coals, especially when using
mechanical reducers with a cutting number much greater than the minimum cutting
number specified in the standard, a much lower variance can be obtained. Therefore,
empirically speaking, if similar equipment is used to prepare samples of similar coals,
it is possible to specify a relatively strict target value for the total variance.
The worst-case variance of a single reduction stage (0.08 for ash) is taken as the
maximum reduction variance. This variance value will decrease if mechanical reduction
is used.
4.5.2.3 Online sample preparation
When certain procedures of specimen preparation are performed in a system combined
with a primary subsampler, sample preparation error may be associated with the
primary subsample variance (VI). In this case, the residual VPT may be smaller than the
variance if all sample preparation is performed offline.
It is recommended to determine the actual total variance target value for online sample
preparation based on experience. However, the maximum total variance target value
shall be the sum of the worst single reduction stage variance and the test variance for
each reduction stage (see 4.5.2.1).
4.5.3 Sample preparation and overall (total variance) verification procedures
The first step in the overall verification is to verify whether the total variance of sample
preparation and testing exceeds the target value, that is, whether the difference
between the two is statistically significant.
The verification method is as follows.
In the first stage of specimen reduction, a pair of double specimens are taken. Then,
two test specimens are prepared separately (see Figure 3). Ten pairs of double
specimens are taken in this way.
Let y be the average of the absolute differences of the results of 10 pairs of double
Figure 3 -- Specimen preparation overall test
4.5.4 Staged verification
4.5.4.1 Basic requirements
Two procedures are generally used for staged verification. Procedure 1 (see 4.5.4.2)
involves a larger number of tests and is more expensive. Procedure 2 (see 4.5.4.3)
involves a smaller number of tests, but its accuracy is slightly lower.
According to the principles described in 4.5.4.3 and 4.5.4.4, procedures with more than
two reduction stages can generally be verified.
For example, the error of a three-stage procedure can be decomposed into.
a) Extract the error of Y kg from X kg, V1;
b) Extract the error of 60 kg from Y kg, V2;
c) Extract the error of 1 g and testing error from the test sample with a particle size
less than 0.2 mm, VT.
Then the total variance V of the program is then calculated using formula (19).
When double specimens are taken from an intermediate stage, the total variance shall
be the sum of the variance of that stage and the variances of subsequent stages. For
example, the variance of double specimens taken from the second stage of a three-stage
procedure shall be V² + VT.
To separate the variances, double specimens shall be taken from each stage and the total
variance for each stage shall be calculated. Then, the calculations shall be performed
backwards from the analysis stage.
4.5.4.2 Method for taking double specimens using different dividers (methods)
4.5.4.2.1 Divider
First, divide a specimen into two portions using the divider procedure. Then, collect all
discarded samples. Repeat the process to divide another specimen into two portions
again.
Note the following during operation.
a) During feeding, the coal stream shall be fed in a columnar shape, oscillating back
and forth along the entire length of the separator;
b) The double specimens shall not be taken separately from the two portions of the
specimen obtained from the first reduction.
4.5.4.2.2 Mechanical divider
Adjust the divider so that it can be divided into two specimens simultaneously.
Alternatively, take one specimen first, then discard all samples and return them to the
divider before taking another specimen.
4.5.4.2.3 Other methods
First, reduce the sample size to one specimen using the corresponding operating
procedure. Then, discard all samples and reduce the sample size to one specimen again
using the same operating method.
4.5.4.3 Staged verification procedure 1
4.5.4.3.1 Method
In the first reduction stage, two specimens A and B with a mass of Y kg are taken out
according to method 4.5.4.2 (see Figure 4). Then the remaining specimens are discarded.
Following standard procedures, specimen B is prepared into a general analytical test
coal sample.
In the second reduction stage, two specimens, A1 and A2, each with a mass of 60 g, are
taken from specimen A according to method 4.5.4.2.Each sample is a general analytical
test coal sample.
A certain characteristic parameter, such as ash content, of three specimens A1, A2 and
B is measured twice.
As described above, at least 10 specimens are processed to obtain 10 groups of 6 results
each.
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
Tips & Frequently Asked QuestionsQuestion 1: How long will the true-PDF of English version of GB/T 19494.3-2023 be delivered?Answer: The full copy PDF of English version of GB/T 19494.3-2023 can be downloaded in 9 seconds, and it will also be emailed to you in 9 seconds (double mechanisms to ensure the delivery reliably), with PDF-invoice. Question 2: Can I share the purchased PDF of GB/T 19494.3-2023_English with my colleagues?Answer: Yes. The purchased PDF of GB/T 19494.3-2023_English will be deemed to be sold to your employer/organization who actually paid for it, including your colleagues and your employer's intranet. Question 3: Does the price include tax/VAT?Answer: Yes. Our tax invoice, downloaded/delivered in 9 seconds, includes all tax/VAT and complies with 100+ countries' tax regulations (tax exempted in 100+ countries) -- See Avoidance of Double Taxation Agreements (DTAs): List of DTAs signed between Singapore and 100+ countriesQuestion 4: Do you accept my currency other than USD?Answer: Yes. www.ChineseStandard.us -- GB/T 19494.3-2023 -- Click this link and select your country/currency to pay, the exact amount in your currency will be printed on the invoice. Full PDF will also be downloaded/emailed in 9 seconds. Question 5: Should I purchase the latest version GB/T 19494.3-2023?Answer: Yes. Unless special scenarios such as technical constraints or academic study, you should always prioritize to purchase the latest version GB/T 19494.3-2023 even if the enforcement date is in future. Complying with the latest version means that, by default, it also complies with all the earlier versions, technically. How to buy and download a true PDF of English version of GB/T 19494.3-2023?A step-by-step guide to download PDF of GB/T 19494.3-2023_EnglishStep 1: Visit website https://www.ChineseStandard.net (Pay in USD), or https://www.ChineseStandard.us (Pay in any currencies such as USD, Euro, KRW, JPY, AUD, CAD, RMB, IDR, INR, THB, HKD etc.).
Step 2: Search keyword "GB/T 19494.3-2023".
Step 3: Click "Add to Cart". If multiple PDFs are required, repeat steps 2 and 3 to add up to 12 PDFs to cart.
Step 4: Select payment option (Via payment agents Stripe or PayPal).
Step 5: Customize Tax Invoice -- Fill up your email etc.
Step 6: Click "Checkout".
Step 7: Make payment by credit card, PayPal, Google Pay etc. After the payment is completed and in 9 seconds, you will receive 2 emails attached with the purchased PDFs and PDF-invoice, respectively.
Step 8: Optional -- Go to download PDF.
Step 9: Optional -- Click Open/Download PDF to download PDFs and invoice.
See screenshots for above steps: Steps 1~3 | Steps 4~6 | Step 7 | Step 8 | Step 9
|