Exam Question
Write short notes on:
(a) Main air starting valves (4)
(b) Exhaust valve rotator (4)
(c) Scavenge relief valve (4)
(d) Function of Labyrinth Seals in turbocharger (4)
Class 4 (4th Engineer)
MEKM
📅 Oct 2025
Reference Answer
### (a) Main Air Starting Valve
**1. Purpose and Function:**
The main air starting valve is a critical component in the starting system of large, reversible marine diesel engines. Its primary function is to admit a large volume of high-pressure starting air (typically 25-30 bar) directly into the cylinder at the precise moment in the cycle (just after Top Dead Centre on the power stroke) to force the piston down and impart turning moment to the crankshaft. This process is repeated across cylinders in a specific sequence to achieve continuous rotation and start the engine.
**2. Construction:**
**1. Purpose and Function:**
The main air starting valve is a critical component in the starting system of large, reversible marine diesel engines. Its primary function is to admit a large volume of high-pressure starting air (typically 25-30 bar) directly into the cylinder at the precise moment in the cycle (just after Top Dead Centre on the power stroke) to force the piston down and impart turning moment to the crankshaft. This process is repeated across cylinders in a specific sequence to achieve continuous rotation and start the engine.
**2. Construction:**
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