SECTION B
In this section of the paper, the candidates’ answers were just satisfactory. However, question 15 was not attempted by many candidates; questions 12 and 13 were not adequately answered. Their solutions are accordingly given below.
Question 12
(a) Explain the following properties of lubricating oil:
(i) body;
(ii) flow;
(iii) viscosity.
(b) What is multigrade oil?
(c) List:
(i) three components of engine lubricating system.
(ii) two methods of engine lubrication.
(iii) two types of oil filtration.
Observation
Solution
(a) Explanation of the lubricating oil properties
- Body
- Flow
- Viscosity
This is the ability of the oil to maintain an unbroken film of oil between two surfaces under all normal conditions of speed and load.
This is the ability of the oil to spread easily over the surfaces and to pass easily through small holes and clearances.
This is the measure of the rate of flow of oil
(b) What multigrade oil is
This is the oil that contains additives which reduce the effect of temperature on their viscosity.
(c) .
(i) The components of engine lubricating system
Sump, pump, wire-gauze filter, gallery, feed pipe, pressure relief valve, crankcase venting, by-pass or full-flow filters, dipstick, warning lamp and switch, pressure gauge
(ii) Methods of engine Lubrication
Splash feed method, mist feed method, pressure-feed, petroil method, boundary method, wet sump method, dry sump method
(iii) Types of oil filtration
By-pass or partial filtration and full-flow filtration.