Evaluation of the design of the shift work in an open pit coal mine using paired comparison methodology

Introduction
To guarantee continuous operation, global mining companies operate 24/7. They therefore design shift work patterns that, while observing safety provisions related to sleep and fatigue issues and complying with national and international law, allow them to operate continuously. A study was designed to evaluate the impact of the current shift pattern in an open-pit coal mine in northern Colombia in terms of the operation itself as well as its acceptance on the part of employees.

Methods
The methodology is based on the paired comparison model developed by Dean & Nishry (1965), which is used to compare alternatives. Twenty-three (23) variables related to operational, psycho-social, and shift pattern design factors were identified and evaluated in a paired approach by 16 experts representing different disciplines.

Results
Compared with nine shift patterns described in the literature, and implemented in different mines globally, the current shift pattern in this company was classed as the second-best pattern when 23 variables were analysed across the above three categories. However, taking the fatigue factor on its own, the current shift pattern reveals certain disadvantages compared to other methods of shift organization.

Discussion
The application of the Dean & Nishry method for variable comparison, in addition to the appropriate selection of variables and their accurate description, has allowed an objective analysis of the shift pattern design. Alternatives shift patterns to those currently used could provide better safety conditions for operators, but would entail operational difficulties or hurdles to employee acceptance. A creative search for ways of organizing shift patterns that involve employees is the best way to design shift patterns that incur the minimum risk of sleep and fatigue for employees.