What is a common method to check the base metal condition under a deteriorated lining?

To assess the condition of the base metal under a deteriorated lining, conducting an ultrasonic thickness (UT) scan from the external surface over areas of concern proves to be an effective technique. This method allows inspectors to evaluate the thickness of the base metal without having to remove the lining. By utilizing ultrasonic waves, the inspector can gather data about the metal's condition, identify potential areas of corrosion or degradation, and determine whether the structural integrity of the pressure vessel is compromised.

Ultrasonic testing is particularly advantageous because it can effectively penetrate the lining material, providing reliable thickness measurements and offering insights into any hidden defects that may not be visible through visual inspection. This capability is crucial since deteriorated linings can hide significant issues with the base metal underneath.

While visual inspections can provide some information on the condition of the lining itself, they may not reveal the underlying base metal issues. Magnetic testing, on the other hand, is generally used for materials that can be magnetized and is not as effective for assessing metal under a non-metallic lining. Pressure testing primarily evaluates the integrity of the entire vessel under pressure conditions but does not directly assess the condition of the base metal beneath a lining. Therefore, utilizing an ultrasonic thickness scan from the outside serves as the most competent method