During an external inspection of an insulated vessel, how much insulation should be removed to check the surface condition?

The option stating that insulation removal is not required unless corrosion is suspected is valid because, during regular external inspections of insulated vessels, it is not customary to remove insulation unless there are specific indicators that suggest potential issues, such as visible rust or other signs of deterioration.

When conducting an external inspection, the primary focus is to assess the condition of the insulated vessel without the necessity of full insulation removal, which can be labor-intensive and may not be justified if the initial inspection does not reveal any red flags. This approach saves time and resources while still adhering to safety and regulatory standards. Therefore, leaving the insulation intact unless there is an indication of corrosion effectively balances thoroughness in inspection with practical considerations.

In contrast, other options imply a more disruptive approach to inspecting the outer surface. Removing all insulation would be excessive, potentially leading to unnecessary downtime and increased labor. Removing insulation along the entire circumference or a large section may not be warranted unless specific conditions necessitate such actions, which is not often the case in routine inspections.