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RE: Vibration Problem

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Thanks Jordan,
The amplification by pipe itself is possible only when pipe is flexible.
& what will happen if pipe is rigid??
If we stiffen the rigid pipe, it may absorb all forces at the point where we connected it rigidly. And may cause more vibration in structure as pipe is only connected to main structure.

First of all we have find that, who is transmitting the vibrations?
If its compressor foundaion itself then, foundation isolation is the best way to reduce vibrations.

But if rigid pipe is rigidly connected to structure & transmitting the maximum vibration then what shall we do, to reduce the vibrations????
Can we provide another rigid support for pipe from outside the structure?

Regards,
Raviraj R. Swami 
Tecnimont ICB,
Civil Dept.
Mumbai-400064
Office : +91-22-67777097 


 -----Original Message-----
From: 	Jordan Truesdell, PE [mailto:seaint2(--nospam--at)truesdellengineering.com] 
Sent:	Friday, April 25, 2008 5:17 PM
To:	seaint(--nospam--at)seaint.org
Subject:	Re: Vibration Problem

Sounds like you've got a resonance in the structure. You might need to 
determine whether the pipe is amplifying the compressor vibration first. 
If the pipe is increasing the amplitude of the compressor vibration, you 
might be able to stiffen or (more likely at higher frequencies) dampen 
the vibration at the pipe. Otherwise, you'll need to isolate the pump 
from the structure, and possibly add a tank/baffle between the 
compressor and pipe to reduce transmission of the compressor pulses in 
your fluid (sorry, can't think of the correct term).

It may be possible to find and dampen the individual components which 
are being excited, but you'll need a detailed FE model to get accurate 
responses and to determine what the modal mass participation is of the 
structure at that frequency to determine if it is large portions of the 
structure instead of individual components.

Jordan



Swami Raviraj (Mumbai - Civil) wrote:
> In one of the process structure(in petroleum industries ) which is @ 60m high & plan dimensions 34 x 54m at bottom (with offset of 9 x 12m ) & reduced to 22x 20m(at top)
> It's RCC up to first level & steel above it.
> It's already erected at site (Operating condition)
> there is one big compressor  at ground level (located at hardly 1 - 1.5m) from  main structure.
> Two big pipes are coming from this compressors (900 dia) & entering in main structure at 25m  level from ground level 
> 3 supports are taken for pipe from main structure at intermediate levels.
>
> when  we start this compressor the structure also starts vibrating (& its really much more like earthquake at 25m level)
>
> Now I have to check that why its happening & what are the remedial measures for it.
>
> So I need your suggestions for it 
>
>
> Regards,
> Raviraj R. Swami 
> Tecnimont ICB,
> Civil Dept.
> Mumbai-400064
>
>
>
>
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