Enumerate the propeller safety margins in relation to the chief engineer?
Announcement
Collapse
No announcement yet.
Enumerate the propeller safety margins in relation to the chief engineer?
Collapse
X
-
-
o PD- propeller design point (obtained theoretically in experimental tanks)
o SEA MARGIN- Over a period, hull and propeller become fouled, and hence resistance increase demanding more power for same speed.
- Also when weather is bad, resistance increases further
- Hence for determining engine power, it is normal to give 15% allowance as sea margin
o ENGINE MARGIN:- Engine margin is 10 – 15% and is added to operational margin of engine
Shaft Generator Margin- Is required if shaft generator is present and additional margin kept for shaft power
o LIGHT RUNNING MARGIN- Over a period hull and propeller is fouled, and hence power will be required to maintain same speed
- This margin is 5 – 6% when deciding power and speed characteristics of the engine
Comment