Multiple Compressors on Common Foundation 4

[privateer]

I've started at a new company that does a lot of compressor stations in pipeline facilities. The company has had a lot of success installing multiple compressors (3 to 5 per) on common concrete block foundations - meaning, lined up in a straight row on the common concrete (3-4 feet thick) foundation. There has been no vibration issues. They even install pre-fab metal buildings on the same foundations (even with bridge-cranes) that cover the compressors, without any vibration issues in the structures too. The compressors used are in the 5000-6000 HP range, weighing 110,000-140,000 lbs. (entire package, including the structural skid).

My project manager asserts that this is the way he has always done it, and has had success for about 30 years this way. As a design engineer, I do not dis-believe him - actually I would like to prove him correct somehow (it's not enough to be successful, I need to understand WHY/HOW we are successful..)

I have done compressor foundation analysis before, but by no means am I an expert. But the foundations I have done were a single compressor on a block foundation, and the overhead structure foundation was separated (separate column footings and isolation joints..)

In my research, I have found no design guide to address multiple compressors on a common block foundation, other that several "references" that comment that this is actually a favorable condition - that the vibrations "cancel" or dampen because vibration frequencies are scattered by the multiple machinery running at the same time....

Any thoughts/comments/ideas....????

 

[concretemasonry]

You never know what the next equipment will be and its properties.

Dick

 

[Ron]

Privateer...in its simplest form, the isolators are two plates with stiff springs in between. The bottom plate can be attached to your slab and the column baseplate attached to the top plate.

This would work well for an aluminum structure. You could handle uplift with adjacent cables, though many isolators will handle multi-directional loads.

These are not as heavy and the custom seismic isolators used in high seismic zones, but are more adaptations of machine vibration isolators that have enough capacity to do as your application needs.

Check this link and look at ths OSM-4 series

http://www.vibrasystems.com/?EC=Products&CategoryID=0&page=0

 

[BUNAIN]

You should look at BS CP 2012.
This code gives good advice regarding the design of these foundation types. Also you will need the soil design parameters (Barkan Constants). It includes a list of references for the design of machine foundations. You should consider the dynamic loadings for each machine - consider the forces for all machines as acting together and all in the same directions, so that you can calculate the maximum vibration amplitude at any point on the foundation block. The code also gives the minimum foundation wt./machine wt. ratio. Depending on the soil characteristics you will get the frequency ratios in all directions and the maximum allowable vibration amplitude from a graph(frequency vs displacement).
Regards
BUNAIN