Which safety measure is required before entering a vessel?

• A. Locking, Tagging, and Blinding lines that feed the vessel
• B. Venting the lines only
• C. PPE only
• D. Training only

Answer: (A)

Before entering a vessel, you need to ensure it is fully isolated from all energy sources and material flow. Locking out the equipment prevents it from being powered or started again, tagging communicates that maintenance is in progress, and blinding the lines that feed the vessel physically blocks any material from flowing in. This combination ensures there’s no pressure, energy, or material entry while someone is inside, preventing sudden releases or inputs that could cause harm. Venting the lines alone only addresses pressure in one part of the system and doesn’t stop other sources from feeding the vessel. PPE and training are essential, but they don’t by themselves guarantee complete isolation.