This publication applies to the inspection and evaluation of tubes 12 ft or longer with an outside diameter greater than or equal to 18 in that are supported by the neck mounting surface. Tubes with a smaller diameter are outside the scope of this publication. It provides methods to assess the integrity of tube necks including but not limited to mounting threads, pin or set screw marks, and other damage to identify rejectable tubes.

This publication also applies if a saddle unit is being reconfigured into a unit supported by mounting threads.