Question 362General Subjects - Assistant Engineer

The correct answer is C) pitch of the screws. The pitch of the screws is one of the main differences between various types of screw pumps. The pitch refers to the distance between the threads or flights of the screws, which affects the pumping capacity and efficiency of the pump. Different applications may require screw pumps with varying pitch designs to optimize performance. The other answer choices are not the primary distinguishing factors between screw pump types. The direction of rotation (A) and type of driving gears (B) can vary, but these are not the main differences. The stuffing box diameter (D) is more related to the pump's sealing mechanism rather than the fundamental screw design.