Final answer:
The center-to-center distance of a 6" long radius return bend is 12 inches, option b, because it is twice the radius of the bend, each being equal to the nominal pipe size.
Step-by-step explanation:
The correct answer is option b, which is 12 inches. In pipe fitting, a 6-inch long radius return bend refers to the bending radius of the pipe, not the actual distance between the centers of the two ends of the pipe. Since the bend is a long radius bend, we assume the radius of the bend is the same as the nominal pipe size, which in this case is 6 inches. The center-to-center distance in a pipe bend is defined as the length between the apex of the bend and where it intersects with the extension of a line from the straight end of the pipe. Therefore, for a 180-degree return bend, the center-to-center distance is twice the radius: 2 x 6 inches = 12 inches.
The center-to-center distance of a return bend can be understood by considering the radius and the length of the bend. In this case, the bend has a 6-inch long radius. The center-to-center distance is twice the length of the radius, so it would be 2 times 6 inches, which equals 12 inches.