If an instrument fitter finds unlabeled tubing mixed with other unlabeled tubing, what should they do first?

The most appropriate course of action in this scenario is to report the problem to the supervisor and have the tubing PMI'd (Preventive Maintenance Inspection Done). Ensuring that tubing and materials are correctly labeled is essential for safety, compliance with industry standards, and the integrity of the installation or repair process. Unlabeled tubing can pose significant risks, as it may be made of different materials or have varied specifications that can affect performance and safety.

By involving the supervisor and initiating a PM inspection, the instrument fitter is taking the necessary steps to identify and rectify the issue before any further work is carried out. This approach not only helps prevent potential errors or accidents that might arise from using the wrong type of tubing but also maintains a standard of quality within the workplace. Proper labeling is vital for traceability and future maintenance, making this action crucial for maintaining safe and effective operations.

The other options, while they may seem practical, do not prioritize safety and compliance as effectively. Simply ordering more tubing does not address the existing problem, and comparing physical properties like wall thickness or conducting a hardness test might not provide the necessary clarity without proper identification of the materials involved.