Foundation for a Natural Gas Generator 1

[oengineer]

I have a natural gas generator that requires a foundation to support it. I have obtained a vendor cut-sheet for the generator. The cutsheet does NOT provide the Operating Speed (RPM) or Power Rating (HP) for the natural gas generator.

I was looking through ACI 351.3R-04 Foundations for Dynamic Equipment and notice that they mentioned generators in the document. Would a natural gas generator be considered a "Centrifugal Equipment"? If so, it would mean that the foundation should be sized for 3 times the weight, correct?

Is the type of generator mentioned in ACI 351.3R-04 Foundations for Dynamic Equipment different than a natural gas generator? Would only "Turbine Generators" be consider for either a "Centrifugal" or 'Reciprocating" Equipment Foundations?

Comments/Suggestions are appreciated.

 

[oengineer]

What kind of generator? Reciprocating or centrifugal? If it's reciprocating many clients I've worked with have required a 5x multiplier.


If you don't have access to your clients specs you need to request access. If they don't have specs on the limit for dynamic analysis you need to get buy-in from the client to your approach. Don't roll the dice and design to the mass ratio without buy-in. If your foundation vibrates and damages the generator it likely won't end well for your company. Saving a few thousand on a foundation won't get you far if a quarter million dollar piece of equipment is damaged.

I will verify that the Natural Gas Generator is a centrifugal machine.

I was originally provided a weight of 39 kips for the Natural Gas Generator, but after further investigation it has been determined that the actual Natural Gas Generator is only 17.5 kips and metal enclosure & skid for the generator is the additional 21.5 kips.

If I use just the 17.5 kips (the actual weight of the generator) then the mass ratio for the foundation is actually 5.3.

It would appear that the foundation is satisfactory for the Natural Gas Generator, whether it is Reciprocating or centrifugal, since it has a mass ratio of 5.3 (excluding the metal enclosure & skid weight of 21.5 kips).

The sensitivity of these will depend on how many kW the unit is. Little ones like the one in the image are designed for the most part to be skid out to a remote site, attached to a light foundation, and fired up. Big models are different. If this is for your other project, I doubt it is a monster generator. I know of diesel fuel generators operating much larger sites. Those bear on some relatively small piles. If the unit is large and very expensive, you need to find a consultant that specializes in dynamic analysis. The general rules of thumb are inadequate for many.

What are your thoughts on the Natural Gas Generator having a power rating of 450 kW (this is for a different project then the one mentioned in another post)?

 

[oengineer]

Is there anything else that I should consider for this Natural Gas Generator foundation?

 

[1503-44]

Overturning forces and moment from short-circuit load.
Unequal uniform soil loading below, dynamic consolidation and potential differential settlements.

“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"