LIGHT WEIGHT PACKAGING SORTING PLANTS 68-69 day. It is recommended not to exceed 2 shifts/day due to the advantages of not having to run this third daily shift: • Flexibility of the facility in case of seasonal increases in plant input material and possible stoppages due to breakdowns, as the time dedicated to the third shift will be used to deal with said problems. • Lower operational costs by avoiding paying night shift bonuses to workers as per collective bargaining agreements. In addition, personnel cost increases due to working on holidays are also avoided, since the third shift requires performing maintenance work on weekends. Standard work shifts are considered to comprise 1,800 h/year, although due to breaks, cleaning time and line availability, the useful working hours per shift are 1,729: Standard for annual useful working hours at light weight packaging sorting plants. Table 8 Operation days/year 247 Hours/shift 8 Break time/shift 0.5 Cleaning time/shift 0.13 Line availability 95% Useful hours/shift*year 1,729 Useful hours/2 shifts*year 3,458 Sizing In order to optimise operational costs it is necessary to have two work shifts at the end of the facility’s service life. Therefore, the nominal capacity of a sorting plant must be such that it allows processing of all inputs at the end of the facility’s service life in two daily work shifts. In this way, the nominal capacity of the facility can be calculated as: Nominal capacity = inputs at the end of the useful lifetime (t/year) / (2 shifts * 1,729 h/year) Seasonal input increases must also be considered. For example, it is common in coastal areas for inputs to increase in the summer months. Therefore, the design capacity of a sorting plant must be such that it allows processing of the seasonal input increases at the end of the facility’s service life in two daily work shifts. In addition, to ensure that all waste is treated the design capacity must be oversized by 10%. The design capacity of the facility can be calculated as: Design capacity = 1.1*(mean monthly input and end of lifetime (t/month) * Input increase in one month (%) / (2 shifts * 144 h/month)).
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