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Rating Definitions

Propulsion

Heavy Duty(HD)

Typical Operation: Allowable Load Factor is less than 100% of Rated Power.
Allowable Cruising Speed is less than 100% of Rated Speed.
Operating hours is unlimited per year.
Typical Vessel Application: Fishing Boats, Cargo Boats, Pusher Boats

Medium Duty(MD)

Typical Operation: Allowable Load Factor is up to 83% of Rated Power.
Allowable Cruising Speed is up to 94% of Rated Speed.
100% of Rated Power is available intermittently for 8Hr per every 24Hr operation.
Operating hours is less than 6000Hr per year.
Typical Vessel Application: Bay Area Tug Boats, Working Boats, Passenger Boats, Ferry Boats

Light Duty(LD)

Typical Operation: Allowable Load Factor is up to 75% of Rated Power.
Allowable Cruising Speed is up to 91% of Rated Speed.
100% of Rated Power is available intermittently for 1Hr per every 6Hr operation.
Operating hours is less than 3000Hr per year.
Typical Vessel Application: Pleasure Boats, Yachts, Patrol Boats, Fire Fighting Boats

Auxiliary and Generator Set

Prime - Limited Running Time

Definition: Prime-Limited Running Time is applicable for supplying continuous power paralleled with the utility for the limited short-time period.
Typical Operation: Allowable Average Load Factor for 24Hr is 100% of Rated Power.
Over-Load of 110% can be used for less than 25Hr per year on emergency.
Yearly Average Load Factor is less than 100%.
Operating Hour is less than 500Hr per year.
Typical Application: Seasonal Peak Cut, Stand-by Power Source

Prime - Unlimited Running Time

Definition: Prime-Unlimited Running Time is applicable for supplying power with varying load instead of the utility for an unlimited time.
Typical Operation: Allowable Average Load Factor for 24Hr is 80% of Rated Power.
100% of Rated Power is available intermittently for 3Hr per every 24Hr operation.
Over-Load of 110% can be used for less than 25Hr per year on emergency.
Yearly Average Load Factor is less than 60%.
Operating Hour is unlimited.
Typical Application:  Stand alone Power Source, Daily Peak Cut, Power Source for Construction
  • In some cases with special condition or application, engines will not comply with the definition above.

For more information, please contact your local MHI international offices.