Marine Engineering Study Materials

Scavenge inspection or scavenge port inspection refers to inspection of piston, piston rings, cylinder liner, etc. of the main propulsion engine through scavenge ports. This helps for detecting leakages from the piston and cylinder cover, if any. Jacket cooling water and lubricating oil pumps should be running during the scavenge port inspection. Scavenge inspection is carried out partly from under piston area and partly from scavenge air receiver. Inspection procedure is following.

• Make sure that vessel has necessary permission from port authorities or bridge for main engine immobilization.
• Engage turning gear to main engine.
• Remove scavenge port inspection covers and scavenge air receiver covers.

• Ventilate and clean the area.
• Turn the engine to bring the piston of the unit under inspection to BDC (Bottom Dead Center).
• Check for presence of any water or fuel on top of the piston, which indicate leakages.

• Check condition of cylinder liner wall through scavenge ports using mirror.
•  Slowly bring the piston up from BDC.
• Inspect piston top land and piston skirt.
• When piston rings are visible through scavenge ports, move piston up and down several times to ensure that rings are freely moving in the piston grooves.
• Use a wooden stick and press the rings to ensure free movement of piston rings. Any broken piston rings can also be found by this way.
• The first piston ring is normally CPR (Controlled Pressure Relief) type. In that case check that the CPR grooves are not clogged and gap is not enlarged.

• Clearance between ring groove and rings can be measured and recorded.
• Move the piston further upwards and check condition of piston rod.
• Visually inspect the condition of stuffing box.

• Depend on the amount of sludge accumulated at the under piston area, the frequency of scavenge port inspection can be varied.

• In the scavenge air receiver area, check for free movement of flap valves, auxiliary blower impeller, scavenge manifold relief valve, water accumulation near air cooler mist catcher, etc.