GB/T 24243-2009Chromium ores -- Increment sampling (English PDF)

1 Scope

The Standard specifies methods for sampling chromium ores at the place of delivery and the place of receipt.

The method is applicable to increment sampling of all natural chromium ores or processed chromium ores by manual and mechanical methods.

Appendix A specifies the procedure for increment sampling of lumpy chromium ores

with a particle size >100 mm by the shovel sampling method using a hammer.

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated references, all subsequent amendments (not including errata content) or revisions do not apply to this standard. However, parties to agreements that are based on this Standard are encouraged to study whether the latest versions of these documents can be used. For undated references, the latest edition applies to this Standard.

GB/T 24232, Manganese and chromium ores - Experimental methods for checking the bias of sampling and sample preparation (GB/T 24232-2009, ISO 8541:1986, IDT) GB/T 24233, Manganese and chromium ores - Experimental methods for evaluation of quality variation and methods for checking the precision of sampling (GB/T 24233-2009, ISO 8542:1986, IDT) ISO 565:1983 (E), Test sieves - Woven metal wire cloth, perforated plate and electroformed sheet - Nominal sizes of openings ISO 6154:1989 (E), Chromium ores - Preparation of samples

3 Terms and definitions

For the purposes of this Standard, the following terms and definitions apply.

lot

A certain quantity of chromium ores processed or produced under assumed identical conditions.

consignment

A certain quantity of chromium ores delivered at one time. A consignment may consist of one lot, several lots or part of a lot of chromium ores.

increment

(1) A certain quantity of chromium ores taken at one time from a consignment of chromium ores using a sampling device.

(2) A certain quantity of chromium ores obtained by increment division.

sub-sample

(1) A certain quantity of chromium ores consisting of two or more increments taken from a consignment of chromium ores.

(2) A sample formed by combining two or more increments after selective crushing and/or selective division, as necessary.

gross sample

(1) A certain quantity of chromium ores consisting of all increments taken from a consignment of chromium ores.

(2) A combination of all increments or all sub-samples after selective crushing and/or selective division, as necessary.

two-stage

Firstly, primary sampling units are selected from a consignment, and then secondary sampling units are selected from the selected primary sampling units. In this standard, this method may be used for sampling from trucks or containers. During sampling, a certain number of trucks or containers shall first be selected as primary sampling units, and then increments shall be taken from the selected trucks or containers as secondary sampling units.

4 General principles of sampling

The following principles are common to and shall be complied with by all parties concerned.

a) Qualified sampling devices or qualified mechanical sampling devices approved by the buyer and/or seller shall be used.

b) Sampling should preferably be carried out simultaneously before and after weighing, or during loading and unloading.

c) When sampling is started at random, systematic sampling shall be adopted.

Sampling of chromium ores from trucks may be carried out by the two-stage method or stratified sampling method.

d) In order to prevent systematic errors from being introduced during sampling, the increment mass shall be determined according to the nominal top size of the chromium ores.

e) The number of increments taken from a consignment shall be determined according to the type of quality variation of the chromium ores and the required sampling precision.

f) Sample contamination shall be prevented throughout the entire sampling process.

g) All sampling methods shall be verified in accordance with GB/T 24232 to confirm that there are no systematic errors.

h) If the expected number of increments has been taken before completion of the operation, increments shall continue to be taken at the same intervals until the loading and unloading operation of the chromium ores in the consignment is completed.

i) Sampling shall be carried out in compliance with national safety standards.

5 General sampling methods