GB/T 6678-2003 (GB/T6678-2003, GBT 6678-2003, GBT6678-2003)
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General principles for sampling chemical products
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GB/T 6678-2003
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Standards related to: GB/T 6678-2003
| Standard ID | GB/T 6678-2003 (GB/T6678-2003) | | Description (Translated English) | General principles for sampling chemical products | | Sector / Industry | National Standard (Recommended) | | Classification of Chinese Standard | G04 | | Classification of International Standard | 71.100.01 | | Word Count Estimation | 16,114 | | Date of Issue | 2003-10-11 | | Date of Implementation | 2004-05-01 | | Older Standard (superseded by this standard) | GB/T 6678-1986 | | Quoted Standard | GB/T 3723; GB/T 4650; GB/T 6679; GB/T 6680; GB/T 6681 | | Drafting Organization | The Chemical Institute of Standardization | | Administrative Organization | National Chemical Standardization Technical Committee | | Regulation (derived from) | Chinese national standard approved by the announcement in 2003 No. 14 (No. 62 overall) | | Proposing organization | China Petroleum and Chemical Industry Association | | Issuing agency(ies) | General Administration of Quality Supervision, Inspection and Quarantine of the People Republic of China | | Summary | This standard specifies: Chemical sampling terminology and definitions, sample projects -, the basic principles of sampling, sample programs, sampling techniques, sample security, sample records and sample reports, sample containers and stored measurement time sampling and testing. This standard applies to: chemical products sampled. | GB/T 6678-2003
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 71.100.01
G 04
Replacing GB/T 6678-1986
General Principles for Sampling Chemical Products
ISSUED ON: OCTOBER 11, 2003
IMPLEMENTED ON: MAY 01, 2004
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative References ... 4
3 Terms and Definitions ... 4
4 Purposes of Sampling ... 4
5 Basic Principle of Sampling ... 6
6 Sampling Plan ... 6
7 Sampling Technology ... 7
8 Sampling Safety ... 11
9 Sampling Records and Sampling Report ... 11
10 Sample Container and Storage ... 12
11 Measuring One-Time Sampling Inspection ... 12
Appendix A (Informative) Relevant Examples of this Standard ... 19
Appendix B (Normative) Relevant Schedules of this Standard ... 24
General Principles for Sampling Chemical Products
1 Scope
This Standard specifies the terms and definitions of chemical product sampling, sampling
purposes, basic principles of sampling, sampling plans, sampling techniques, sampling safety,
sampling records and sampling reports, sample containers and storage, and metering one-time
sampling inspection.
This Standard applies to the sampling of chemical products.
2 Normative References
The provisions in following documents become the provisions of this Standard through
reference in this Standard. For dated references, the subsequent amendments (excluding
corrigendum) or revisions do not apply to this Standard; however, parties who reach an
agreement based on this Standard 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 3723 Sampling of Chemical Products for Industrial Use - Safety in Sampling (GB/T
3723-1999, idt ISO 3165:1976)
GB/T 4650 Chemical Products for Industrial Use – Sampling – Vocabulary (GB/T 4650-
1998, idt ISO 6206:1979)
GB/T 6679 General Rules for Sampling Solid Chemical Products
GB/T 6680 General Rules for Sampling Liquid Chemical Products
GB/T 6681 General Rules for Sampling Gaseous Chemical Products
3 Terms and Definitions
For the purposes of this Standard, the terms and definitions given in GB/T 4650 apply.
4 Purposes of Sampling
The basic purpose of sampling is to obtain a representative sample from the overall material to
be tested, and to obtain data within the allowable error through the detection of the sample, so
4.4.3 To classify materials by hazard, etc.
5 Basic Principle of Sampling
The basic principle of sampling is to make the collected samples fully representative.
When the cost of sampling (such as material cost, operation cost, etc.) is high, the sampling
error and cost can be properly considered when designing the sampling plan, but the
requirements for sampling error shall be met.
6 Sampling Plan
6.1 Factors influencing the sampling plan
6.1.1 The nature, physical state and range of the overall material to be collected. The range can
be a certain delivery batch agreed by the purchaser and supplier, or a certain production batch
produced intermittently; and in the case of continuous production, it can be the material
produced within a certain time interval;
6.1.2 The possibility of contamination or deterioration of the overall material during or after
production;
6.1.3 Acceptable sampling error;
6.1.4 Specifications of inspected materials;
6.1.5 Characteristic definition of material judgment standard;
6.1.6 Precision of the detection method;
6.1.7 Value of the material;
6.1.8 Possibility to simplify sampling operations.
6.2 Basic content of sampling plan
6.2.1 Determine the range of the overall material;
6.2.2 Determine the sampling unit and the secondary sampling unit;
6.2.3 Determine the number of samples, the quantity of samples and sampling location;
6.2.4 Specify sampling operation methods and sampling tools;
6.2.5 Specify the processing method of the sample;
The variability of the overall material characteristic values and their types are the basis for
designing a sampling plan. They exist objectively, but it is expensive and difficult to operate to
estimate them through the detected data. Therefore, the actual measurement is generally not
carried out when designing the sampling plan, but inferences and assumptions are made based
on experience and the material information that has been mastered.
7.4 Sampling of uniform material
7.4.1 The uniformity of uniform materials may vary with the size of the specified unit to be
investigated. For example, 10 t of material packed in 50 kg barrels has no significant difference
in the average value of characteristics between barrels. Therefore, this batch of materials are
uniform materials for the barrel unit. If the materials in the barrel are segregated during
processing, there will be differences in the average characteristic values between 500 g portions
of materials taken from different parts of the barrel. Therefore, for the 500 g material as the
inspection unit, the material is non-uniform.
7.4.2 Sampling of uniform materials can, in principle, be carried out at any part of the materials.
But beware:
7.4.2.1 Impurities shall not be brought into during the sampling process.
7.4.2.2 Avoid material changes (such as water absorption, oxidation, etc.) during the sampling
process.
7.5 Sampling of non-uniform materials
For the sampling of non-uniform materials, in addition to paying attention to the same two
points as uniform materials, random sampling is generally adopted. The obtained samples are
measured separately; and the results of all samples are aggregated to obtain an estimate of the
average and variability of the characteristics of the overall material. If several equal samples
(or unequal samples taken in proportion to the amount of represented material) are randomly
selected from the overall materials, combined into a large sample, and then reduced into the
final sample; then the estimate quantitative error of the average value of the characteristics
obtained from it is large, meanwhile, the information about the variability of the characteristic
value cannot be obtained.
Designing the sampling plan according to the variability types of the acquired characteristic
values can make the collected samples better represent the overall materials and save the cost.
7.5.1 Sampling of random non-uniform materials
A random non-uniform material refers to a material in which the average value of the
characteristics of any part of the overall material is independent of the average value of the
characteristics of the adjacent parts. The sampling can be randomly selected or non-randomly
selected.
7.5.2 Sampling of oriented non-random non-unform materials
Oriented non-random non-uniform materials refer to materials in which the characteristic
values of the overall material change along a certain direction. For example, when the solid
granular material is conveyed, the material that is separated vertically and horizontally due to
the difference in particle size and weight. Another example is that after filling at high
temperature, it gradually solidifies from the near wall to the center, and the materials that the
impurities content must form a gradient with the solidification sequence. Such materials shall
be sampled in layers, and samples that can represent the layer of materials shall be taken from
each layer with different characteristic values as far as possible.
7.5.3 Sampling of periodic non-random non-uniform materials
Periodic non-random non-uniform materials refer to materials whose characteristic values show
periodic changes in a continuous material flow, and the change period has a certain frequency
and amplitude. For such materials, it is best to sample on the material flow line; and the
sampling frequency shall be higher than the change frequency of the material characteristic
value, and the two shall not be synchronized. Increasing the number of sampling units shall
help reduce sampling bias.
7.5.4 Sampling of mixed non-random non-uniform materials
Mixed non-random non-uniform material refers to a mixed material composed of two or more
characteristic value variability types or two or more characteristic average values. For example,
a material that is combined from several production batches. For this type of material, first
separate the components as much as possible, and then sample according to the above-
mentioned sampling methods for various types of materials.
7.6 The number of samples and the quantity of samples
Under the premise of meeting the needs, the minimum number of samples and the minimum
quantity of samples that can give the required information are the optimal number of samples
and the optimal quantity of samples.
7.6.1 The number of samples
For general chemical products, multi-unit materials can be used for processing. Its unit
boundaries may be tangible, such as a container; or imagined, such as a specific time interval
for flowing material.
For multi-unit materials to be sampled, the sampling operation is divided into two steps. The
first step is to select a certain number of sampling units; the second step is to sample each unit
according to the variability of material characteristic values.
If the unit number of the overall material is less than 500, the number of sampling units is
recommended to be determined according to the provisions of Table 1. If the unit number of
the overall material is greater than 500, the number of sampling units is recommended to be
When sampling, the condition and sampling operation of the collected materials shall be
recorded, such as the name, source, serial number, quantity, packaging, storage environment,
sampling location of the materials, the number of samples and the quantity of samples, sampling
date, name of sampling personnel, etc. If necessary, fill in the sampling report according to the
records.
For routine general sampling, the above specification can be simplified.
10 Sample Container and Storage
10.1 Sample container
10.1.1 Caps, plugs or valves that meet the requirements must be washed and dried before use;
10.1.2 The material must not interact with the sample material and must not be permeable;
10.1.3 For photosensitive materials, the sample container shall be light-tight, or cover the
container with a light-proof plastic bag.
10.2 Sample label
10.2.1 The name and serial number of sample;
10.2.2 Batch number and quantity of overall material;
10.2.3 Production units;
10.2.4 Sampling location;
10.2.5 The quantity of sample;
10.2.6 Sampling date;
10.2.7 Samplers, etc.
10.3 Saving and withdrawing of samples
The product sampling method standard or sampling operation procedure shall stipulate the
storage amount of the sample (as a test-pre sample), storage environment, storage time and
withdrawal method. For the saving and withdrawing of highly toxic and dangerous samples, in
addition to complying with general regulations, relevant regulations on toxic substances or
hazardous chemicals shall also be followed.
11 Measuring One-Time Sampling Inspection
Appendix A
(Informative)
Relevant Examples of this Standard
A.1 Example 1 (example for standard deviation is known in 11.2.1.1):
Given a batch of chemical raw materials, the distribution of a certain chemical composition is
normal, and its standard deviation σ = 0.45 (%) is known. It is hoped that the average value of
this chemical composition shall be no lower than 42 (%). If it does not exceed 41 (%), it can
only be accepted with a small probability. And specify α = 0.05, β = 0.01, try to give a sampling
acceptance scheme (n, k) that meets the above requirements.
Substitute into the formula, and obtain n=3.2 (by n=4), k=41.6; thus, the sampling acceptance
plan is:
Collect 4 unit-products from the overall materials; detect and calculate the average value (%)
of its chemical composition, and obtain the judgment rules as follows:
A.2 Example 2 (example for standard deviation is unknown in 11.2.1.1):
In Example 1, if σ is unknown, 0.45 (%) is only a less precise estimate of it, and find the
sampling acceptance plan.
Solution: According to the formula, n = 4.54 (by n = 5), k = -0.92. Therefore, the sampling
acceptance plan is:
Take 5 unit-products from the overall materials, detect and calculate the average value (%)
of its chemical composition and the standard deviation s of the sample, and the judgment rule
is obtained as follows:
Solution: it is known It can obtain from Table B.1 of Appendix B
If
If
, it is judged as qualified
, it is judged as unqualified
If
If
, it is judged as qualified
, it is judged as unqualified
A.3 Example 3 (example for standard deviation is known in 11.2.1.2):
A batch of steel plates for manufacturing chemical equipment, it is stipulated that when the
average Rockwell hardness does not exceed 70, it is considered to be a qualified product; and
if the average hardness is equal to 73, it is considered to be unqualified; and it is specified that
α=0.05, β=0.10, and it is known that σ =2. Find a one-time sampling acceptance scheme (n, k)
that meets the requirements.
Substitute into formula, obtain n=3.79 (by n=4), k=71.68; therefore, sampling acceptance plan
is:
Take 4 blocks of samples from such batch of steel plates, determine its hardness; and calculate
their average value (%); and obtain the judgment rules are:
A.4 Example 4 (example for standard deviation is unknown in 11.2.1.2):
In the above example, assume that σ is unknown, find the sampling acceptance plan.
Solution: According to the inspection data of recent batches of similar products, the σ value is
estimated to be about 2.5. Substitute the data into the formula, obtain n = 7.26 (by n = 8) and k
= 0.67. Therefore, the sampling acceptance plan is:
Take 8 blocks of samples from such batch of steel plates; measure their hardness; calculate their
average value and sample standard deviation s, obtain the judgment rules are:
A.5 Example 5 (example in 11.2.2):
The quality indicator μ0=1.40 (%) for the average content μ of a certain component in the
material, it is required that the deviation from μ0 be as small as possible; and the tolerance
d0=0.07. According to historical data, it is known that σ = 0.043, when μ = μ0, the probability
of being judged as a Class-1 product is 0.999; and if , it shall be judged to be
downgraded; and the probability of misjudgment does not exceed 0.10. Find its one-time
sampling acceptance plan (n, d).
Solution: it is known It can obtain from Table B.1 of Appendix B
If
If
, it is judged as qualified
, it is judged as unqualified
If
If
, it is judged as qualified
, it is judged as unqualified
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