Question 21 QMED02 - Electrician-Refrigerating Engineer

The Correct Answer is D. **Why option D is correct:** Before performing any work on electrical equipment, such as an electric cargo winch master switch or controller, the primary safety procedure mandated by industry standards (like OSHA or relevant maritime regulations) is to **de-energize the circuit** and ensure it cannot be accidentally re-energized. * **Open the circuit breaker in the power supply:** This action physically disconnects the power source, de-energizing the equipment. * **Tag-out (Lockout/Tagout - LOTO):** This procedure involves placing a lock and a tag on the open circuit breaker. The lock prevents unauthorized or accidental closing of the breaker, and the tag provides warning and identification of who is working on the circuit. This is the crucial step for preventing serious injury or death from electrical shock or arc flash. **Why the other options are incorrect:** * **A) heat the switch box to remove any moisture:** While moisture is undesirable in electrical enclosures, heating the box is not a necessary preliminary safety step before beginning work, nor is it standard procedure for moisture mitigation. More importantly, it does not address the immediate hazard of live voltage. * **B) spray the gasket surface with a solvent:** Applying solvents to gaskets is irrelevant to the immediate safety requirements. Furthermore, certain solvents can degrade gasket material, compromising the enclosure's weatherproofing later. * **C) drain condensate from the box:** Draining condensate (if a drain valve exists) is a maintenance task. While good practice, it is secondary to the immediate safety requirement of de-energizing and locking out the power supply. Draining condensate from a live box still poses an electrical hazard.