🔍 Key Concepts

• Location of the scavenge air space versus the crankcase on a crosshead-type diesel engine • Function of stuffing boxes/piston rod glands in separating different pressure and atmosphere zones • Which side of the rod (top vs. bottom gland) is exposed to pressurized scavenge air and which is exposed to crankcase oil mist

💭 Think About

• From the illustration, trace the piston rod from the crankcase up toward the cylinder: which area is likely filled with oil mist and which with pressurized air? • If there are two glands in series, what contamination or leakage are they trying to prevent in each direction (oil going up, air going down, or something else)? • Which of the answer choices directly relates to controlling scavenge air rather than crankcase conditions?

✅ Before You Answer

• Identify which side of the top gland faces the scavenge air receiver/ports • Decide whether the exam is asking about oil leakage or air leakage at this upper position • Eliminate any options that deal with maintaining overall crankcase pressure or vacuum, since those are usually handled by dedicated crankcase ventilation systems, not just a single gland.