Which type of insulation is required before a vessel is entered?

• A. Locking, Tagging, and Blinding lines that feed the vessel
• B. Venting the lines only
• C. Electrical insulation
• D. No isolation required

Answer: (A)

Positive isolation of all energy sources feeding the vessel is essential before entry. Locking the line control devices prevents re-energizing, tagging provides a clear warning that work is in progress, and blinding the lines physically blocks any flow into the vessel. Together, these steps ensure no hazardous material or pressure can enter or build up during entry, protecting workers from unexpected releases and exposures.

Venting lines alone might relieve pressure, but it does not stop all energy or flow from other sources, and it doesn’t address stored energy or parts of the system that could still fill the vessel. Electrical insulation only tackles electrical energy and leaves fluid, mechanical, or thermal hazards unchecked. No isolation is not acceptable because it would allow energy, pressure, or hazardous contents to reach the worker. Therefore, locking, tagging, and blinding the feeding lines is the proper approach.