Question 12Motor Plants - 1st Asst/Chief

The correct answer is B) insufficient ring groove clearance. Insufficient ring groove clearance can cause the piston ring to crack on a large, low-speed, main propulsion diesel engine. This is because the piston ring needs adequate clearance in the ring groove to allow for thermal expansion during engine operation. If the clearance is insufficient, the ring will be unable to expand freely, leading to high stresses and potential cracking. The other answer choices are incorrect because: A) high main lubricating oil temperature would not directly cause ring cracking, C) insufficient cylinder liner wear is not a common cause of ring cracking, and D) contaminated lubricating oil would not directly lead to ring cracking in this type of engine.