Main Generator, Auxiliary Generator or Essential Generator

[NickParker]

We have three diesel generators that operate in parallel with a steam turbine generator (STG) on a tanker, of course there is a Main Engine. The excess steam generated from the heat value of VOC gases during cargo loading operations is utilized to drive the steam turbine generator (STG).

Should the diesel generators be referred to as Main Generators, Auxiliary Generators, or Essential Generators? Similarly, considering that the STG operates intermittently in parallel with the diesel generators, would it be classified as a Main Generator, Auxiliary Generator, Essential or Non-Essential Generator?

 

[Gr8blu]

How much power is required to cover all the main (i.e. loading, unloading, and transit) electrical loads - including lighting, pumping, fans, communication, navigation, and propulsion?

From what I recall of the American Bureau of Shipping (ABS), Lloyds Register (LR), and Det Norske Veritas (DNV) rules, all generators that operate on a continuous basis to supply this main load are classed as "MAIN / ESSENTIAL". Depending on the AHJ (authority having jurisdiction) that covers the vessel construction and/or operation, there may also be a "plus one" generating unit that may be the same or smaller than the rest that acts as partial spare or to handle normal peak electrical loads (unusual sea conditions, for example or multiple operations that are possible but not considered "normal"). The "plus one" is there for safety reasons.

Any generation that is not intended for continuous appreciable loading usually gets classed as "Standby / Auxiliary".