BS ISO 13909-2:2016 pdf download – Hard coal and coke — Mechanical sampling Part 2: Coal — Sampling from moving streams

BS ISO 13909-2:2016 pdf download – Hard coal and coke — Mechanical sampling Part 2: Coal — Sampling from moving streams f) Establish the number of sub-lots and the number of increments per sub-lot required to attain the desired precision (see 4.3.4). g) Decide whether to use time-basis or mass-basis sampling (see Clause 5) and define the sampling intervals in minutes for time-basis sampling or in tonnes for mass-basis sampling. h) Ascertain the nominal top size of coal for the purpose of determining the minimum mass of sample (see 4.4 and Table 1). NOTE The nominal top size may initially be ascertained by consulting the consignment details, or by visual estimation, and may be verified, if necessary, by preliminary test work. i) Determine the minimum average increment mass (see 4.5). 4.2 Design of the sampling scheme 4.2.1 Material to be sampled The first stage in the design of the scheme is to identify the coal to be sampled. Samples may be required for technical evaluation, process control, quality control and for commercial reasons by both the producer and the customer. It is essential to ascertain exactly at what stage in the coal-handling process the sample is required and, as far as practicable, to design the scheme accordingly. In some instances, however, it may prove impracticable to obtain samples at the preferred points and, in such cases, a more practicable alternative is required. 4.2.2 Division of lots A lot may be sampled as a whole or as a series of sub-lots, e.g. coal dispatched or delivered over a period of time, a ship load, a train load, a wagon load or coal produced in a certain period, e.g. a shift. It may be necessary to divide a lot into a number of sub-lots in order to improve the precision of the results. For lots sampled over long periods, it may be expedient to divide the lot into a series of sub-lots, obtaining a sample for each. 4.2.3 Basis of sampling Sampling may be carried out on either a time-basis or a mass-basis. In time-basis sampling, the sampling interval is defined in minutes and seconds and the increment mass is proportional to the flow rate at the time of taking the increment. In mass-basis sampling, the sampling interval is defined in tonnes and the mass of increments constituting the sample is uniform. Of these two alternatives, time-basis sampling is easier to implement...