Foundation Drawing Standards 2

[JamesBarlow]

I'm looking for information on creating Foundation Drawings for large machinery.

This is a drawing that would be given to a Civil Engineer to design the floor that the equipment will be placed on. I'm the machine designer and need a way to comunicate with a Civil so they can design the floor requirements.

I have seen a number of different ways to do this but I would like to find out if there is an acceptable, standard way to create these drawings.

 

[Cockroach]

You're typically looking at eight (8) inches of cement with 28 MPa strength. I would think that the building designer or architect would need to review this, most machinery is bolted to the floor and makes use of isolation pads to mitigate vibrations.

I've seen six (6) inches of cement, but thought this may be pushing it a bit. My shop uses the previous with a bit of silicon in the aggregate to reduce the probablility of future cracking. So far, so good but there is never any guarantee against cracking since the foundation continues to settle beyond the 30 day cement cure requirement.

Hope this points you the right way.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[Tmoose]

For rotating machinery (dynamic loading) the soil loading should be a fraction of the basic allowable for static type loads. There are some guidelines for foundation length/width/depth of approximately that should be used generously beyond the basic ones like "foundation should weigh 3X (or 4X or 5X) the machine weight." And should also include consideration for keeping natural frequencies well away from vibration caused by the machine.

The machine builder should have a lot to offer.

 

[JStephen]

i've not seen a standard for this. You'd typically need to show dead load, live load, etc, wind or seismic overturning/shear if applicable, and how these loads are distributed to the foundation. Loads need to be broken out so load factors can be applied. If the manufacturer's rated loads include allowances for vibration, that should be indicated. For a smaller item, a single vertical load might be all that was required, where a larger item could require more detailed information.

 

[swearingen]

Here's a list I require:

- Location and size of bolt holes
- Location and size of bearing areas
(well dimensioned cut-sheets usually take care of the above, but it is alarming how many cut-sheets don't have this basic information spelled out.)
- Vertical, lateral and overturning loads due to wind, earthquake, and dead and live load, preferably in a tabular form. These loads are to be calculated at to the machine/concrete interface.
- For vibrations, you must provide information on what's causing the vibration and preferably an idea of the forcing function. Where is the center of mass? Is it a rotating mass? Reciprocating compressor or engine? What is the mass of the rotating portion? Where is the CG of the rotating portion? What are the frequencies to be used? How fast does the machine start up/shut down? If it passes through an excitation frequency quickly on its way up or down, it may be acceptable. Ideally, if it's a large machine, you should confer with an experienced machinery foundation guy as the machine/soil interaction can make or break the design.

Also, please note that if you cannot give, or don't know how to give the wind and earthquake loads, a good structural can calculate these if given the general shape and projected areas as well as the center of mass.

I've done some of these foundations and done troubleshooting for some that were causing problems. This is one case where getting it right the first time is very important.

And I couldn't resist picking on Cockroach a little: I wouldn't put my machines on cement. That fine powder won't approach a 28MPa strength. Now, if you mix it with the appropriate amounts of water and aggregate, it becomes concrete and it's a different ball game...

 

[BigInch]

He needs some picking on. Cement or Concrete, I can't see how he justifies a 6 or 8 thickness of cement for a "large machine". Is a large machine in Canada a pickup truck?


BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[Tmoose]

SP-78: Foundations for Equipment and Machinery

http://www.concrete.org/PUBS/JOURNA...cation=Special+Publication&volume=78&ID=14130

There are several papers included in SP-78 on different topics. Some papers resort to rules of thumb like "foundation should weigh 3X (or 4X or 5X or 10X) the machine weight." Other papers show how and why the footprint dimensions and CG height are far more important.

 

[unclesyd]

Our site used two different philosophies on machine support. The manufacturing area used nothing except an 8" floor because the machines were light but over the years as the speed increased they would hit different sweet points and the vibrations would increase to the point that all sorts of thing were done to alleviate things walking around on tables. It was once asked did the vibrations produce a standing wave with water in a petri dish, the answer was that it was enough to slosh mercury over the sides of the dish. Other areas went for mass to minimize any possibility of transmitted vibrations exciting adjacent buildings and equipment.

On all our large machines we isolated the foundation of each machine even though the shop floor was 12" thick. The weight multiple of the block was always 10x or better.

In one of our compressor buildings we had 5 IR 5CVE Steam Driven Hyper Compressors with each having an isolated base with a weight multiple of 20x.

 

[BigInch]

All machine foundations depend on static weights, starting, stopping, short-circuit loads and operating dynamic loads, maintenance loads, and the amplitude, frequency of application, duration and location of the loads AND the dynamic characteristics of the floor support and/or the underlying soil strata. Also depends on the susceptibility of the process to vibration and the capability of the machine to operate under the resulting dynamic conditions. Some machines have a lot less load than others and foundations can be designed or provided with minimal (or no?) engineering input, whereas others may require 1 to 4 or more specific soil borings, evaluation of several soil layers both for bearing capacity and for dynamic response to be completed before any serious attention can be given to the actual foundation design. A foundation for a 500 HP electrically driven centrifugal pump weighing 3000 lbs is vastly different from a 500 HP diesel driven reciprocating pump of similar weight, even before varying soil parameters are considered. Wet sand has vastly different dynamic properties than dry clay. All depends what you're going to install and where you're going to install it.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com