Manufacturing Skill Standards Council (MSSC) Safety Assessment Practice Test

What is the most reliable method to lock out a motor?

1. Satisfy OSHA

2. Safely ground a motor

3. Turn off a motor

4. Interrupting the power circuit at the motor disconnect

The correct answer is: Interrupting the power circuit at the motor disconnect

The most reliable method to lock out a motor is by interrupting the power circuit at the motor disconnect. This method ensures that the power supply to the motor is completely cut off, preventing accidental startup while maintenance or repairs are being conducted. It provides a clear and direct way to isolate the machine from its energy source, which is a critical aspect of lockout/tagout procedures aimed at protecting workers. Using a motor disconnect is also a best practice as it typically involves a physical mechanism that can be locked in the off position, which adds an additional layer of safety. This prevents unauthorized personnel from accidentally re-energizing the motor while maintenance work is ongoing. While satisfying OSHA regulations and safely grounding a motor may contribute to overall safety practices, they do not specifically focus on the direct methodology of isolating the motor’s power source. Turning off the motor alone is insufficient without ensuring that the energy source cannot be inadvertently re-engaged.