What variation of routing is used to measure the maximum pit depth on the outside of a pipe?

• A. Profiling the outside with a micrometer
• B. Placing a sample length in a lathe and machining it until no further corrosion is evident
• C. Cross-sectioning the pipe and inspecting under magnification
• D. Grinding the surface and measuring depth with a caliper

Answer: (B)

To determine the maximum pit depth on the outside of a pipe, you want a method that reveals how deep the corrosion actually penetrates from the original surface. Placing a sample length in a lathe and machining it away until no further corrosion is evident exposes the deepest pit and allows you to measure that depth directly from the amount of material removed. This approach is direct and quantitative, and it works on curved surfaces where surface-profile methods might miss a true depth. It provides a single, representative depth for the deepest pit along the sampled length.

Profiling the outside with a micrometer is impractical on a curved pipe and only captures surface variations, not the true depth of pits. Cross-sectioning would require cutting the pipe and only shows a local view, potentially missing the deepest pit elsewhere. Grinding and measuring with a caliper can be imprecise due to uneven removal and surface irregularities, making it harder to capture the actual deepest point.