generator and fuel tank

[dahualin]

I am doing a pump station design with a generator to back up two 200hp pumps. Both pumps will not start at same time. My calculation for sizing the generator is listed below
FLA of 200hp pump (460v) (table 430.250): 240A
LRA of 200hp pump (460v) (table 430.251B): 1450A

The total starting current is 240+1450=1690A
The total starting KVA is 1690A x 480V x 1.732 = 1405 KVA

The total KW is (240 + 240) x 480 x 1.732 = 399 KW

So I have to select a 400 KW generator with at least 1450 starting KVA. Am I right?

Any thought about fuel tank? We will put a 24 hours back up fuel tank. Which code talk about the location of fuel tank?

Thanks.

 

[JeffD]

My rule of thumb for generator fuel is that they consume 8 gallons per hour for every 100 kw so if you are planning on running a 400 kw genset for 24 hours at full load the calc will be


400 kw / 100 kw x 8 gallons/hour x 24 hours = 800 gallon tank

An easy way to figure it out is go to a genset supplier tell him your requirements see what he comes up with.

 

[hardworkingstiff]

Any thought about fuel tank? We will put a 24 hours back up fuel tank. Which code talk about the location of fuel tank?

Are you just having the 24-hour tank? Is there going to be a day tank fed from a storage tank? Do you need to design fuel polishing into the system?

Fuel systems for generators are a specialty within themselves. If you have not done one before, I'd contact someone how has for collaboration.

 

[adavey]

I would multiply your calculated load by 1.25 (25 %) for growth; then size your genset to that; as well as your starting KVA. Assuming you have soft starting on your 200HP motors, a soft transition ATS is not worth it. This would increase the life of your genset. Contact the genset manufacturer, they will incorporate the fuel tank and genset in one enclusure for you (I use cummins). Do a google search and you can easily find a fuel consumption chart based on 1/2, 3/4 or full load (search manufactur's website). Do yourself a favor and ask the manufacturer for a recommended foundation and anchoring plan for your genset.

 

[BAHTAH]

Generator and Fuel Tank

Generator and Fuel Tank

You could reduce the starting current by using VFD's if you have that option in your design. In pumping applications there are many advantages to the use of VFD's with respect to water hammer, flow control and energy savings.

Grant

 

[e57]

Is there going to be a day tank fed from a storage tank? Do you need to design fuel polishing into the system?

Just an aside on terminology: Just about all diesel engines will have what is reffered to as a "Day Tank", which is normally mounted close to the injector pump to maintain the pump prime. And that is of course always fed from a storage tank, as the day tank may only hold about 5-30 minutes of fuel. (They ought to call it a "Minute Tank") And that is often enough time to change over to another fuel source, normal to reserve. Loose that primary fuel pump prime with a dry day tank and you are screwed! (Those of us who have had to prime a diesel engine will agree...)

And fuel consumption is engine and load specific, the manufacturer will be the best source of info on that. Engines have become a lot more efficiant in the last several years.

As far as other codes about location of the fuel tanks - check with the AHJ about what thier requirements will be.

Is this a legally required back-up?

 

[wirenut1980]

I am doing a pump station design with a generator to back up two 200hp pumps. Both pumps will not start at same time. My calculation for sizing the generator is listed below
FLA of 200hp pump (460v) (table 430.250): 240A
LRA of 200hp pump (460v) (table 430.251B): 1450A

The total starting current is 240+1450=1690A
The total starting KVA is 1690A x 480V x 1.732 = 1405 KVA

The total KW is (240 + 240) x 480 x 1.732 = 399 KW

So I have to select a 400 KW generator with at least 1450 starting KVA. Am I right?

Any thought about fuel tank? We will put a 24 hours back up fuel tank. Which code talk about the location of fuel tank?

Thanks.

I am not sure that you have to add the locked rotor amps and the running full load amps to get your starting kVA. The maximum the motor would draw would be the LRA and then it would settle down to something at or less than the full load current.

It would also make the design much easier if you had a more specific motor in mind, but if not, then it is good to go with the maximum in Table 430.251(B) as you have done.