Enumerate the propeller safety margins in relation to the chief engineer?

[mohit]

Enumerate the propeller safety margins in relation to the chief engineer?

[deepak]

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