The quality of the primary sub-samples of the mass-based sampling does not change with the flow of the coal. During the entire sampling process, the primary sub-samples or the primary sub-samples should be basically equal in mass and the coefficient of mass variation should be less than 20%.
The quality of the primary sub-samples can be controlled by the following methods, and the methods described in Appendix B to check whether they meet the requirements.
a) Use a sampler whose cross-cut coal flow speed can be adjusted according to the coal flow rate. The cutting speed of each sub-sample is different, but the speed is stable during the cutting of a single sub-sample.
b) Using a fixed speed sampler with a reduction device, the collected sub-samples are reduced to a fixed mass and incorporated into the total sample.