WBGT (Occupational Heat Index)
Calculate the WBGT (wet bulb globe temperature) for indoor environments without solar load, WBGT = 0.7·t_nw + 0.3·t_g, from the natural wet-bulb temperature t_nw and the globe temperature t_g (°C). The result, in °C, is the heat stress index used to assess heat exposure: compared with tolerance limits according to the activity's metabolic rate, it sets the allowed work-rest regime. For environments with solar load, the dry-bulb temperature is also included. Enter the natural wet-bulb and globe temperatures.
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IBUTG (índice de sobrecarga térmica)
O IBUTG (Índice de Bulbo Úmido Termômetro de Globo, em inglês WBGT) é o índice oficial para avaliar a exposição ao calor no trabalho, porque combina num único número os fatores que determinam a sobrecarga térmica: temperatura, umidade (que limita a evaporação do suor) e calor radiante (de fornos, chamas, sol). Para ambientes internos ou externos sem carga solar, a fórmula é IBUTG = 0,7·t_bn + 0,3·t_g, onde t_bn é a temperatura de bulbo úmido natural (um termômetro com gaze umedecida exposto à ventilação natural — captura o efeito da umidade) e t_g é a temperatura de globo (um termômetro dentro de uma esfera negra de 15 cm — captura o calor radiante). Os pesos (70% e 30%) refletem que a umidade é o fator mais crítico. Para ambientes com carga solar (a céu aberto, sob o sol), acrescenta-se a temperatura de bulbo seco com pesos 0,7/0,2/0,1. O resultado, em °C, é comparado na NR-15 (Anexo 3) aos limites de tolerância, que dependem da taxa metabólica da atividade (trabalho leve, moderado ou pesado): quanto mais pesado o esforço, menor o IBUTG tolerável. Quando o IBUTG ultrapassa o limite, a norma exige um regime de trabalho-descanso (alternância de períodos de labor e de pausa em local fresco) para evitar o estresse térmico e suas consequências — da fadiga e cãibras à exaustão e à intermação. Informe as temperaturas de bulbo úmido natural e de globo.
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Noise Dose
Calculate the occupational noise dose, D = (C ÷ T) × 100%, dividing the effective exposure time C by the maximum allowed time T for the measured noise level and multiplying by 100. The result, in %, shows how much of the maximum daily exposure the worker accumulated: 100% is the tolerance limit (85 dB(A) for 8 hours, with a 5 dB exchange rate in Brazil). Doses above 100% require controls and indicate risk of noise-induced hearing loss. For several levels, the C/T terms are summed. Enter the exposure time and the maximum allowed time.
Rankine Cycle Efficiency
Calculate the thermal efficiency of a Rankine cycle, η = (w_turbine − w_pump) ÷ q_boiler × 100%, dividing the net work (turbine work minus pump work) by the heat added in the boiler, all in kJ/kg. The Rankine cycle is the basis of steam power plants: water is pumped, heated and vaporized in the boiler, expands through the turbine producing work, then condenses. The result, in %, measures how much boiler heat becomes useful work; real cycles run 30–45%. Enter the turbine work, the pump work and the boiler heat.
Hand-Arm Vibration A(8)
Calculate the normalized hand-arm vibration exposure A(8), A(8) = a_w·√(t ÷ 8), from the resultant acceleration a_w (m/s²) and the exposure time t (hours). The result, in m/s², normalizes the exposure to an 8-hour shift, allowing comparison with the action and tolerance levels. Prolonged exposure to tool vibration (grinders, breakers, chainsaws) causes hand-arm vibration syndrome, with vascular and neurological damage. Enter the resultant acceleration and the exposure time.
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