Arc-Flash Compliance Implementation at Industrial Processing Facilities
This paper highlights an assortment of case studies and explains how arc-flash hazards were identified, measured, and mitigated in various industrial processing facilities. Case studies reviewed include the following: (1) the completion of arc-flash studies and arc-flash remediation for a group of existing cement pyroprocessing plants in North America to achieve compliance with Electrical Workplace Standards National Fire Protection Association 70E-2012 and Canadian Standards Association Z462-2012 for a multisite cement manufacturer; (2) the implementation of an arc-flash analysis at an existing U.S.-based copper mine/copper concentrate facility; (3) the investigation of an arc-flash incident that occurred during energized work at a U.S. chemical processing facility; and (4) a “Safety by Design” installation for a new Greenfield coal preparation plant in Australia. This paper will examine the plans and processes reviewed and considered and the strategy deployed to manage/reduce arc-flash hazards and then discuss lessons learned in the implementation of new systems to improve electrical workplace safety.
Energy Quality and Efficiency of an Open Pit Mine Distribution System: Evaluation and Solution
The operational availability of mining shovels is the focus of this paper. The hypothesis is that energy quality is responsible for the frequent shutdowns of the shovels. Previous engineering studies have highlighted a large presence of harmonics and reactive power in the mine loop electric system. A common solution proposed was to use a combination of active filters, larger mobile substations, shorter mining cables, and equipment location constraints. The aim of this paper is to produce a precise diagnosis of the source and nature of the energy quality issues. Mine loop electric quality monitoring, system modeling, equipment technologies, and shovel's histograms are considered. Results are measured against IEEE standards and shovel's voltage regulation susceptibility. With the diagnosis, the goal was to produce a reliable cost-effective solution. Different alternatives are crosschecked with this paper proposal. The solution presented provides energy quality well within the shovel's susceptibility and improves energy efficiency. The lower energy consumption pays the investment required and is currently under construction.
Nuclear spin-lattice relaxation in transition metal compounds with local tetragonal symmetry.
We report on the various contributions to the total spin-lattice relaxation rate in metallic materials with local tetragonal symmetry. The analytical formulae are given in the tight-binding approximation. The calculations show the relation between various partial electron densities of states and corresponding contributions to the relaxation rates. The presented formulae can be used to compare theoretically calculated electron band structure parameters with those obtained from NMR spin-lattice relaxation time measurements.