Internal Diesel Storage Tank dimensions

I’m currently trying to estimate the capacity of a sub-base diesel tank beneath a standby generator. Unfortunately, the specifications for this particular unit are unavailable as it is an older model. While a newer, custom-built generator is intended to replace it, we are working with limited information for the existing setup.
The information known is as follows:
- Brand: Massey Ferguson

Key Specifications (based on research):​

• Prime Power (PRP): 300 kW / 375 kVA
• Standby Power (LTP): 330 kW / 412.5 kVA
• Frequency: 60 Hz
• Speed: 1800 RPM
• Voltage: 480V, 3-phase
• Alternator: Leroy-Somer LL5014L
• Winding Configuration: 6/4
• Control Panel: 4001E Series
• Engine: Typically powered by Perkins or AGCO Power engines

In your experience, does measuring the tank externally (using visible dimensions) introduce significant error due to factors like internal baffling or wall thickness, or would it generally provide a reasonably accurate estimate?

I would allow about 1/4 inch for wall thickness and allow at least a 1" air space on top.

Just allow 5% less volume from external dimensions and you'll be fine.

Do you have any requirements for how long this needs to run at power? You should start there. If this is an emergency generator it may be required to meet an equivalent to US EPA Tier 3. These engines often have significantly higher BSFC numbers than any other rating.

The stationary diesel tanks I've seen have double walls in order to have built in secondary containment. Actual interior tank dimensions would be much smaller.

TugboatEng said:

Do you have any requirements for how long this needs to run at power? You should start there. If this is an emergency generator it may be required to meet an equivalent to US EPA Tier 3. These engines often have significantly higher BSFC numbers than any other rating.

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Hello, it is required to run based on the following assumptions:

TugboatEng said:

These engines often have significantly higher BSFC numbers than any other rating.

Click to expand...

Hi Tug.
A long time ago, when I was comparing the fuel consumption of gen-sets, the offerings were NA sets. (Naturally aspirated).
All but one manufacturer listed output at 13 KWHr per Gallon of diesel fuel.
One manufacturer listed 10% higher output, but reading the fine print, they were using 10% heavier fuel than the others.
Can you suggest how the "Gallons per Kilowatt Hour" should be adjusted for the current turbo-aspirated sets?
This is for small sets, less than about 125 KVA.
Thanks.

as a general rule i use 0.25 litres per kwh. in practice, modern diesels sets use less than this.

Fuel demand is irrelevant without knowing what the set up is.

"Day tanks" are common on such units to have a certain amount of fuel available close by. How much can vary from one to two hours running to 24 hours or more, depending on the space available, with more fuel pumped or flowing in on a regular basis from a larger generally external tank.

So IMHO, measure the tank, subtract 5% for internals, double skin, whatever, then maybe assume 80% full and away you go.

Actual time when full will vary by load anyway so whatever number you get will be quite variable in terms of hours supply. Plus it needs to be full when you start....

As LittleInch pointed out, consider the refueling logistics when determining the appropriate size for the new tank. If your requirement is for 24 hours of actual run time, it may be helpful to size the the tank to allow for at least 6 months of routine testing loads in addition to the fuel to run for 24 hours. Scheduling fuel deliveries at precisely 24 hours is also logistically challenging during an extended outage.