Exam Question
(a) How does a modern 4-stroke medium-speed marine diesel engine exhaust valve spindle rotate? (8)
(b) What happens if the tappet clearance between the rocker arm tappet and the exhaust valve stem is too large? (8)
Class 4 (4th Engineer)
MEKM
📅 Mar 2025
Reference Answer
## Part (a): Exhaust Valve Spindle Rotation
A modern 4-stroke medium-speed marine diesel engine exhaust valve spindle is positively rotated during operation to ensure its longevity and reliable performance. This is primarily achieved using a mechanical device known as a **Rotocap**.
### Mechanism: The Rotocap
The Rotocap is a self-contained mechanical unit that replaces the standard valve spring retainer. It is fitted on top of the valve spring(s) and below the rocker arm tappet.
A modern 4-stroke medium-speed marine diesel engine exhaust valve spindle is positively rotated during operation to ensure its longevity and reliable performance. This is primarily achieved using a mechanical device known as a **Rotocap**.
### Mechanism: The Rotocap
The Rotocap is a self-contained mechanical unit that replaces the standard valve spring retainer. It is fitted on top of the valve spring(s) and below the rocker arm tappet.
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