How can blisters on a vessel shell be easily detected?

Blisters on a vessel shell can be effectively detected using a visual examination with a flashlight beam directed parallel to the shell. This method enhances the visibility of surface irregularities, such as blisters, because it creates shadows that emphasize the contours of the vessel's surface. When the light is angled properly, it highlights the raised areas caused by blisters, making them easier to spot.

While other methods like ultrasonic testing and thermal imaging can provide valuable information about the integrity of a pressure vessel, they may not be as straightforward for identifying surface defects that are clearly visible with a simpler visual examination. Similarly, radiographic examination is primarily used for detecting internal flaws rather than surface characteristics. Therefore, utilizing a flashlight beam in a visual inspection is a practical and efficient approach for identifying blisters on the vessel shell.