Final answer:
True, fillet welds are permissible for attaching butt weld fittings, but it is essential to follow specific engineering standards and codes applicable to the project.
Step-by-step explanation:
The question relates to whether fillet welds are permissible to attach butt weld fittings in an engineering context. This is true; fillet welds can indeed be used for this purpose. Fillet welds are a common method for joining two surfaces at approximately right angles to each other in lap, tee, and corner joints. They are also applied in the attachment of butt weld fittings, which are components used for changing the direction of flow, branching, or altering pipe diameters in piping systems.
In practice, the permissibility of using fillet welds will depend on the specific engineering standards and codes applicable to the project at hand, such as the ASME B31.1 for power piping, ASME B31.3 for process piping, or other relevant piping codes. It is always crucial to follow the specified standards which define the dimensions, tolerances, and conditions under which fillet welds can be used.