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Minerals 2018, 8(7), 310; https://doi.org/10.3390/min8070310

Variographic Assessment of Total Process Measurement System Performance for a Complete Ore-to-Shipping Value Chain

1,2,†,* and 2,3,4,5
1
Luossavaara-Kiirunavaara AB (LKAB), Kiruna 98186, Sweden
2
Department of Chemistry and Bioscience, Aalborg University, Esbjerg 6700, Denmark
3
KHE Consulting, Copenhagen 2100, Denmark
4
Geological Survey of Denmark and Greenland (GEUS), Copenhagen 1350, Denmark
5
Sciences de la Terre, Université du Québec à Chicoutimi, Quebec, QC G7H 2B1, Canada
Industrial PhD student, Aalborg University, Denmark.
*
Author to whom correspondence should be addressed.
Received: 21 June 2018 / Revised: 18 July 2018 / Accepted: 19 July 2018 / Published: 23 July 2018
(This article belongs to the Special Issue Sampling across the Mine Value Chain)
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Abstract

Variographic characterisation has been shown to be a powerful tool to assess the performance of process measurement systems, using existing process data. Variogram interpretation enables decomposition of variabilities stemming from the process and measurement system, respectively, allowing to determine if measurements are able to describe the true process variability with sufficient resolution. This study evaluated 14 critical sampling locations, covering a total of 34 separate measurement systems, along the full processing value chain at Luossavaara Kiirunavaara limited company (LKAB), Sweden. A majority of the variograms show low sill levels, indicating that many sub-processes are well controlled. Many also show low nugget effect, indicating satisfactory measurement systems. However, some notable exceptions were observed, pointing to systems in the need of improvement. Even if some of these were previously recognized internally at LKAB, the use of variographic characterisation provide objective and numerical evidence of measurement system performance. The study also showed some unexpected results, for example that slurry shark-fin and spear sampling show acceptable variogram characteristics for the present materials, despite the associated incorrect sampling errors. On the other hand, the results support previous conclusions indicating that manual sampling and cross belt hammer samplers are leading to unacceptably large sampling errors and should be abandoned. Such specific findings underline the strength of comprehensive empirical studies. Based on the present compilation of results, it is possible to conduct rational enquiry of all evaluated measurement systems, enabling objective prioritization of where improvement efforts will have the largest cost–benefit effect. View Full-Text
Keywords: iron ore; process sampling; variographic characterisation; Theory of Sampling (TOS); theory of sampling; measurement systems; quality control iron ore; process sampling; variographic characterisation; Theory of Sampling (TOS); theory of sampling; measurement systems; quality control
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Engström, K.; Esbensen, K.H. Variographic Assessment of Total Process Measurement System Performance for a Complete Ore-to-Shipping Value Chain. Minerals 2018, 8, 310.

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