I used to know how much concrete it took under a fan to keep it stable. Wasn't a rule of thumb 5 times the weight of the fan, or something like that?
quote:Some conservative rules of good foundation design include:
1. The mass of the concrete foundation should be 5-10 times the mass of the supported equipment.
2. Imaginary lines extended downward 30 degrees to either side of a vertical line through the machinery shaft should pass through the bottom of the foundation and not the sides.
3. The foundation should be 3" wider than the baseplate, all the way around a pump up to about 500 hp, and 6" wider for larger pumps.
quote:2.4.2 A machinery block foundation supported on soil should have a minimum mass ratio of three times the mass of the machinery for centrifugal machines and five times the mass for reciprocating machines, unless analysis demonstrates that a lesser value will perform adequately. A block foundation subject to vibrations may require a dynamic analysis to ensure that the provisions of 2.2.11 are met.
Note: The minimum mass ratios 3:1 and 5:1 are traditional empirical values for foundation mass to equipment mass that should be used unless a lesser amount can be demonstrated to perform adequately. Although the 3- to-5 mass ratio has been a good rule of thumb, in certain installations a dynamic analysis of the rectangular concrete foundation may be necessary to adequately predict its behavior.