Which factor reduces the distance a locating signal can travel due to pipe diameter?

• A. Larger diameter pipe
• B. Smaller diameter pipe
• C. Increased insulation
• D. Water content

Answer: (A)

When a locating signal is sent to a buried metal pipe, energy travels along the pipe by inducing current on its wall. The distance the signal can be detected depends on how well that energy remains concentrated in the pipe as it moves. A larger diameter pipe provides a wider surface for the current to spread around, which lowers current density and lets more energy leak into the surrounding soil. This increased dispersion attenuates the signal faster, reducing the detectable distance. A smaller diameter pipe keeps the current more concentrated, helping the signal travel farther. Other factors like insulation or soil moisture affect coupling and loss as well, but the effect driven by pipe diameter is that larger diameter reduces how far the locating signal can travel.