And you are typically taking different readings.
Do you know what the general condition is? Do you know what kind of damage you are looking for?
If you have reason to suspect localized damage (low spots, high spots, transitions) the LRUT may be better suited. If you want a broad picture then go IP.
UT pigging works good in heaters, in long pipe lines you need to have your line prepared with the proper devices to introduce the pigs. With LRUT, when the pipe goes underground or is buried this technic can induces some kind of erroneous indications which makes the examination somewhat confused. In the past I have used both technics, with acceptable and bad results.
