Which statement describes a lathe-based variation of routing used for the outside of a pipe?

• A. Profiling the surface 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. Non-destructive ultrasonic measurement

Answer: (B)

Lathe-based routing involves using a lathe to rotate the pipe (or a sample length) and carefully remove the outer material where corrosion exists, continuing until no evidence of corrosion remains. This approach directly measures how much material has been lost and reveals the true remaining wall thickness at the surface, which is why it’s the correct description for evaluating the exterior of a pipe. The other options don’t describe this machining-and-removal approach: profiling with a micrometer merely measures dimensions without removing corrosion; cross-sectioning and inspecting under magnification is a different destructive method not performed in a lathe-based exterior routing; ultrasonic measurement is non-destructive and does not involve machining away material.