Issue link: https://www.e-digitaleditions.com/i/1192126
30 I ICT TODAY The following additional information has been harvested through observations and discussions with the client: • Dust is present during normal production operations, but the area is not deemed classified under NEC/CEC. • The dust is metallic and, therefore, electrically conductive. • The production area is not environmentally controlled, and the factory is located in a humid climate where seasonal temperature extremes are normal. • The operator station/control room and each of the control panels are environmentally controlled. • This area contains an 8 megawatt electric arc furnace that is used to melt steel. • The area has heavy lift trucks, including overhead cranes moving buckets of scrap steel or ladles contain- ing molten steel. • The client has a stipulation that all electrical/commu- nications wiring and cabling be protected in schedule 40 galvanized steel to 30 feet above floor level for physical protection. • There are existing cable trays with low voltage wiring sections located above the 30 feet above finished floor (AFF) mark that travel along pathways that are mostly accessible during production. • There are three specific zones, each with a 30 ft. radius where radiant heat temperatures can reach 500 °C directly above the furnace roof, the pour station, and the furnace batch sample door. • There are several areas of the factory floor that are not readily accessible during production. • Production runs 24/7 with only one week of shut- down per year, and the work cannot wait until the shutdown window. • This area is not conducive to nor has a requirement for wireless communication. ANSI/TIA-1005-A refers to accompanying charts that provide various measurement thresholds to aid in rating an area using MICE. Tables 1 and 2 are spe- cific regarding the requirements for each criteria of the MICE environmental classification system. Table 10 – MICE Environmental Conditions Mechanical M 1 M 2 M 3 Shock/bump (see note 1) Peak acceleration 40 m/s -2 100 m/s -2 250 m/s -2 Vibration Displacement amplitude (2 Hz to 9 Hz) 1.5 mm 7.0 mm 15.0 mm Acceleration amplitude (9 Hz to 500 Hz) 5 m/s -2 20 m/s -2 50 m/s -2 Tensile force See b) See b) See b) Crush 45 N over 25 mm (linear) min. 1 100 N over 150 mm (linear) min. 2 200 N over 150 mm (linear) min. Impact 1 J 10 J 30 J Bending, flexing and torsion See b) See b) See b) Ingress I 1 I 2 I 3 Particulate ingress (dia. max) 12.5 mm 50 µm 50 µm Immersion None Intermittent liquid jet ≤ 12.5 l/min ≥ 6.3 mm jet > 2.5 m distance Intermittent liquid jet ≤ 12.5 l/min ≥ 6.3 mm jet > 2.5 m distance and immersion (≤ 1 m for <= 30 minutes) TABLE 1: Mechanical and ingress classification system per MICE environmental conditions. Source: TIA-568.O-D Annex D.