Class 2 (2nd Engineer) MEP 📅 Oct 2022

Exam Question

Give a reasoned opinion as to the accuracy of the following assertions:

(a) Absence of oil grooves in the liner wall between the oil supply points results in increased wear of liner and rings.

(b) 'Timed lubrication' has little merit,

(c) The most suitable position of the all supply point is immediately below the bottom piston ring with the piston at top dead centre

Reference Answer

(a) Absence of oil groove:
If there are no oil distribution grooves at the oil feed point, the oil tends to be scraped, locally upward and downward, which cannot spread evenly.
By this effect, in a narrow vertical band leading upwards and downwards from the feed point, there is more alkalinity excessive than required to nuetralise any sulphuric acid in the local area.
The surplus metallic salt, such as calcium carbonate, exposed to high temperature and mixed with other thermal decomposition compounds, tends to form abrasive compounds, such as calcium oxide.

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