Question 67Motor Plants - Assistant Engineer

The correct answer is C) The blocking valve is used to interrupt the control air at port "A" when the turning gear is engaged. The blocking valve is a 3-position, 4-way directional control valve that is used to control the flow of air in the slow-speed diesel engine starting control air distributor. When the turning gear is engaged, the blocking valve interrupts the control air at port "A", preventing the engine from being started. This is a safety feature to prevent the engine from being started while the turning gear is engaged, which could cause damage to the engine. The other answer choices are incorrect because they do not accurately describe the function of the blocking valve in this system. Option A is incorrect because the blocking valve interrupts the control air, not the supply air. Option B is incorrect because the blocking valve interrupts the control air when the turning gear is engaged, not disengaged. Option D is incorrect because the blocking valve interrupts the control air, not the supply air.