What is a precaution to take when heating pipe?

Ensuring the pipe is open throughout its entire length is crucial when heating it because a closed or obstructed section can lead to pressure buildup. If the pipe is filled with liquid or gas that cannot escape, the heat can create pressure that may exceed the pipe's limits, resulting in potential failure or rupture. This safety precaution helps to prevent accidents and ensures that any steam or gas produced can safely exit the pipe, maintaining integrity and safety during the heating process.

While the other options provide important considerations for pipe safety and efficiency, such as having a water source for emergencies or insulating the pipe to retain heat, the critical aspect of keeping the pipe open focuses directly on preventing dangerous pressure situations during heating. Monitoring temperature is essential for achieving desired results, but the primary concern regarding safety during the heating process is ensuring that the pipe is entirely open to allow for the safe release of pressure.