In early 2013, the language in Clause 7.11 Criteria of D 7430 Part A regarding sampling ratios was modified to read In addition, give sampling systems a performance check as a matter of routine. This is done by comparing the weight or volume of collected sample with that of the total flow of coal to ensure a constant sampling ratio. The change in language was in the first sentence. Specifically, the phrase give sampling systems a performance check replaced the phrase sampling systems should be given a performance check. This was done following ASTMs general request that standards be written in the imperative. This language effectively made these performance checks mandatory to comply with the Criteria for Satisfactory Performance in the standard. As a result, questions were raised about some of the terminology used in regards to these performance checks. In particular, there is no definition for performance checks in the Terminology section. There is no standard procedure for comparing the collected sample with the total flow of coal. Also, constant is not defined in relation to the sampling ratio. Subcommittee ballots this summer to clarify these shortcomings in the standard generated a great deal of discussion and were withdrawn to incorporate those comments prior to re-balloting. A significant area of discussion in the Task Group meeting held in October 2013 was the ramifications of a sampling ratio requirement in the field. Although members recognized the importance of the sampling ratio, concern was expressed that the language contributed to the misapplication of the sampling ratio as a performance check that should have a definite result, similar to a bias test. One specific example cited was the acceptance or rejection of the individual sample for a consignment based on its ratio. A second was the acceptance or rejection of a sampling system based on the sampling ratio data even when it had passed a bias test. The ballot(s) related to this work item are a result of the Task Groups efforts to more carefully define the sampling ratio and its role in sampling practice.
Keywordsauger sampling; barge sampling; coal; coal sampling; inspection; mechanical sampling; railroad car sampling; sample division; sample reduction; sampling systems; split-spoon sampling; statistical analysis; stock pile sampling; truck sampling;
Draft Under Development