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?
Randall's Reliability Driven Pump Handbook page 117 states:
API 686-1996 ("Recommended Practices for Machinery Installation and Installation Design") States:
3 -5X was what I had in mind, but I was none to sure about it .
I appreciate the reference.
I've always worked on the rule of minimum of 3x mass for the base, but I can't point to a source. I have seen real world apps. where mass was less than 3, and problems ensued!
I have a customer that laid (4) 2 X 10's out on the ground and poured them full of concrete. Didn't even level it off or screed it. then installed a fan (probably 1500 - 2000#) on top of it, put some 1/2" Hilti anchors in it, and called it good
It is not.
Did he leave the 2x10's on? Might have made the difference
Good foundation... for a Hot Tub!
Yes, the 2 X 10's are still on
The Hilti's were the first thing to go, I think they are on the third try with anchors (they not only pulled out, but broke the pad where a couple go in). The legs had broken welds.
THis fan is in resonance. When I balanced it (1725 rpm, MOTOR AT 1789), I was bringing it down .2 mils at a time with a grinder just hitting the blades and the weights that were on there. It's sensitive
I was called to "balance" a wood hog. This was a laminated disc-type rotor and they had replaced the knives and disassembled the laminations without marking, then reassembled.
Amazingly enough, it was out of balance. It was anchored with 3/8" "thunderstuds" to the 4-6" thick concrete floor. Edited to substitute "had been" for "was" in the previous sentence.
I don't know what became of it. I gave him an estimate of what it would take to fix it and he never got past just the cost of balancing, much less digging a hole and putting some concrete under the thing.
This place has a wood hog too. But it's running, and looked like it was sitting on a block in the ground. We'll see.
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