Capacity of Diesel Generator Day Tank?

There must be an echo around here.

You asked same question a couple of days ago!

Was it the same guest, though?

Must have cut and pasted the question.

Dear Guest,

In the absense of further details, you need to decide how long your generators may run unattended, before someone refills them with fuel. Assuming, by describing the tanks as "Day Tanks", you want them to last 24hours. The generator engine manual wil give you the fuel consumption per hour at maximum load. From this figure, work out your fuel consumption at maximum load for 24 hours, then add a factor of safety of, say 10%. Your day tank size needs to be at least 20% bigger than this figure! Why, because you do not want to fill your day tank above 90% capacity, in case it overflows when you fill it, and you do not want the tank level to drop below 10%, in case your delivery pipe at the bottom of the tank is exposed, causing fuel starvation, or you suck up any water or dirt that is in the bottom of the tank, blocking your filters. This is the rough rule of thumb I would use - I can't answer whether there are any International Codes or standards for the sizing for land based installations, but for day fuel tanks on ships, LRS Rules state for ships over 500GT there has to be 2 service tanks for each type of fuel used, of sufficient capacity to allow 8 hours running of the main engine(s) and generators for 8 hours at MCR.