Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
Notes on this paper
National Exams — December 2019 — 11-CS-2 Engineering in Society: Health and Safety. Closed book. Do any five of the seven questions (each 10 marks). Full essay-type answers are expected; sketches may support the explanations. Complete answers to all seven questions follow.
Note on the reference charts. Questions 2 and 7 depend on the two attachment pages: page 6 is the Brauer/Dalziel chart of the effects of 60 Hz AC current on a 150 lb (68 kg) man, and page 7 is the Fine risk-assessment nomograph. The nomograph prints only the qualitative descriptors (no numbers appear on its Likelihood, Exposure or Consequence axes), so the scale points used below (Likelihood 10 / 6 / 3 / 1 / 0.5 / 0.1, Exposure 10 / 6 / 3 / 2 / 1 / 0.5, Consequence 100 / 40 / 15 / 7 / 3 / 1) are the standard Fine–Kinney values that the chart's own axis spacing reproduces. Selecting a descriptor for each activity is a matter of judgement; the choices are stated explicitly below and reasonable justified alternatives are equally acceptable, as the paper's Note 8 permits.
(i) Effects — when the environment is hot and/or humid, the body cannot dissipate its metabolic heat; the core temperature rises, the cardiovascular system is strained (blood diverted to the skin), and fluid/electrolytes are lost through sweating, leading to dehydration.
(ii) Symptoms and remedy — progressing in severity: heat rash; heat cramps (salt/fluid loss); heat exhaustion (heavy sweating, weakness, nausea, headache, clammy skin, rapid pulse); and heat stroke (hot, often dry skin, very high temperature, confusion, collapse—a medical emergency). Remedy: move the worker to a cool area, rest, hydrate and cool the body; for heat stroke, aggressive cooling and immediate medical aid. Heat strain is assessed with the WBGT (Wet-Bulb Globe Temperature) index.
(iii) Monitoring — measure WBGT (accounting for air temperature, humidity and radiant heat), set work/rest schedules by WBGT and workload, and monitor air velocity; physiological monitoring (heart rate, hydration) and acclimatization for exposed workers.
(b) Very Low Temperatures
(i) Effects — the body loses heat faster than it produces it; blood flow to the extremities is reduced (to protect the core), impairing dexterity, and the core temperature can fall.
(ii) Symptoms and remedy — shivering and numbness; frostnip/frostbite (freezing of skin and tissue—fingers, toes, ears, nose); and hypothermia (shivering, then confusion, loss of coordination, unconsciousness). Remedy: move to a warm area, remove wet clothing, rewarm gradually; seek medical aid for frostbite/hypothermia (rewarm frostbite carefully, do not rub). Index of stress: the cold-side counterpart of WBGT is the wind-chill index / equivalent chill temperature, which combines air temperature with wind speed to give the equivalent still-air cooling power; the TLV work/warm-up schedule is tabulated against it, and it is the index against which the symptoms above are anticipated rather than merely observed.
(iii) Monitoring — measure air temperature and wind speed to determine the wind-chill index, set work/warm-up schedules based on it, monitor exposure time and watch for symptoms; ensure dry, layered clothing.
