Yes, but special procedures must be followed.  High pressure steam lines at near 425 °F will slow any investigation considerably.  Pressurized high temperature hot water presents a similar issue.  First is the need to remove up to 6 in. thick and potentially hard formed insulation, followed by working in close physical proximity to such hot surfaces and the need to actually touch the pipe with the surface probe.  Metal expands beyond its normal wall thickness at higher temperatures – therefore requiring an additional effort to perform calibration of the equipment to standards at the same temperature.

High temperatures will destroy the sensitive and fragile ultrasonic transducers.  Therefore, they must be allowed to cool at intervals, which in turn slows any investigation. Overall, additional time should be planned for any high temperature investigation.  Lower temperature piping systems such as hot water, reheat, and domestic hot water present far fewer issues of concern.