Exam Question

(a) To avoid scavenge fires, scavenge trunking must be periodically inspected & cleaned, any buildup of the contamination noted & remedied. The drain pockets should also be cleaned regularly to remove the thicker carbonised oil sludges which do not drain down so easily & which are a common cause of the choked drain pipes. Scavenge drains should be blown regularly & any passage of oil from them noted.
The piston rings must be within wear down limits & lubricated suitably so that ring blow-by is avoided. At the same time one must guard against excess cylinder oil usage. With timed cylinder oil injection the timing should be periodically checked.
The piston-rod packing rings & scraper rings should be measured according to intervals in PMS so that oil is prevented from entering the scavenge space because of the butted ring segments. This may & does occur irrespective of the positive pressure difference between the scavenge trunk & the crankcase space.
Fuel injection equipment must be kept in good condition, timed correctly, & the mean indicated pressure in each cylinder should also be carefully balanced so that individual cylinders are not overloaded.