What must be true for the piping system if the operating pressure exceeds 5 psi?

When the operating pressure of a piping system exceeds 5 psi, it is crucial that the piping is welded. This requirement is rooted in the need for ensuring the integrity and safety of the system. At higher pressures, welded joints provide a more secure and leak-resistant connection compared to other methods such as threaded or flanged connections.

Welding creates a continuous joint that is less likely to fail under stress and reduces the likelihood of leaks, which are critical considerations when transporting gas under pressure. The structural strength of welded joints helps to withstand the forces exerted by high-pressure gases, thereby enhancing the overall safety of the propane system.

Other options, while relevant in certain contexts, do not address the specific requirements for systems operating above 5 psi. For instance, insulation may be necessary for temperature control but is not directly related to pressure requirements. Reinforcement of piping can be helpful but does not specifically indicate that welding is required. Plastic materials may be suitable for certain low-pressure applications but are generally not appropriate for high-pressure systems where welding is mandated for safety and reliability.