PAD VIBRATOR ISOLATORS

[Yousef ZAA]

Hi!
I am a structural engineer, and I am designing a project in which has a generator at the roof, the EOR has sent me the generator specs, showing a statement that the generator has built in vibration pads, with that information, I can assume that there is no vibration and consequently no dynamic load imposed on my floor slabs, right?

 

[desertfox]

Hi Yousef ZAA

Not necessarily, the pad idolaters won’t be a 100% therefore some vibration will pass into your floor structure, whether that dynamic load is significant or not will depend on the information about the pads you have.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[Denial]

I agree with desertfox.[ ] Vibration pads (provided they are correctly matched to the generator) should reduce the magnitude of the vibration experienced by your structure, but will not eliminate it.[ ] They will not change its frequency.

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^{Engineering mathematician/analyst.[ ] See my profile for more details.}

 

[Tmoose]

"there is no vibration and consequently no dynamic load imposed on my floor slabs..."
I would not assume that. No sir.

Generator with an gasoline or propane fired multi-cylinder engine?
Located midspan, and over the CEO's office?

Any thoughts to the noise when the generator is running ?

I think of "pads" as rubber etc .5" to 1" thick.
Typically not enough static deflection to provide good isolation for machine rotating and reciprocating frequencies.

The manufacturer needs to provide tech info about the "pads".
The pads themselves.
- material
- static defection when installed ( NOT LOAD RATING ! )
The design work behind the pad selection.
- expected inertial frequencies and forces ( especially if a reciprocating engine )
- for roof mounted equipment, or equipment installed on grade?
I'd push for something like " the support structure must not have resonant frequencies in the range of 15 to 250 Hz with a 2500 lb generator installed mid-span.
- requirements for electrical, fuel, exhaust and auxilliary and cooling connections to the generator. Clamped conduit and pipes can and will provide wonderfully effective paths for vibration to pass right into the roof.

Check out this lecture from the '60s about the complications of roof mounted equipment.

https://mason-ind.com/ashrae-lecture/

Basically isolators for roof mounted equipment needs to be about 10X softer than slab mounted equipment.