Which type of joint is prohibited for copper or copper alloy tubing used for fuel oil?

The use of welded joints for copper or copper alloy tubing in fuel oil systems is prohibited primarily due to safety and performance concerns. Welded connections can introduce potential failure points and may not provide the required flexibility and integrity for the handling of fuel oil. The thermal properties of copper make it susceptible to warping or degradation when subjected to welding temperatures, which can compromise the integrity of the tubing.

In contrast, soldered and brazed joints are permitted as they allow for a more controlled application of heat and better compatibility with the material properties of copper. Compression fittings are also accepted for certain installations as they provide effective sealing without the need for heat application. The prohibition of welded joints is a precautionary measure to prevent leakage and ensure the overall reliability of fuel oil transport systems.