Baseplate deflection limits and corrections

[curious cat]

What are the deflection limits of a turbine generator baseplate mounted on 3 point supports ?
If there's a need to correct it, how it should be done ?

 

[mfgenggear]

I am curious why use 3 points vs 4 point I would think that base would rock excessively.

 

[mfgenggear]

did you run the numbers?

 

[saplanti]

It seems that you are looking at the problrm statically. You need to read about foundations of rotating equipment. At least try google.

 

[Artisi]

And what does the equipment manufacturer say about installing their equipment, assuming they supplied the unit as a package?

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[electricpete]

To help evaluate (one of the) adverse effects of deflection, you could monitor for changes in shaft-to-shaft alignment, using equipment like Permalign.

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(2B)+(2B)' ?

 

[drawoh]

curious cat,

Why do you care?

Your three[‑]point mount will not twist your floor. There will be specifications on how much you can safely twist your turbine generator. That should be your specification, along with a generous safety factor.

--
JHG

 

[Artisi]

When all else fails, read the instructions, or post it on Eng-Tips and get someone elso to do it on your behalf

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[mfgenggear]

maybe at adding stiffeners at the base to make it more rigid, welded to the base. as always research it well before continuing

 

[electricpete]

It brings a question to my mind. The driving torque in electrical machines is transmitted electromagnetically between rotor and the stator accross the airgap. Normally we think about the torque on the rotor (which drives the load in a motor) but there is indeed an equal / opposite reaction torque on the stator which gets transmitted to the foundation (on motors and generators).

For fluid machines (pumps, fans, and turbines), the amount of any torque on the stationary parts is a little more mysterious to me as was discussed here: thread404-259495

This machine in op has 2 supports under the electrical machine but only one support under the fluid machine. Obviously two supports can help the baseplate resist movement under the influence of torque from the mounted machine a lot better than 1 support can. It leads me to believe that maybe the designer of this support thinks the stationary turbine parts do not experience any significant torque. Would you guys agree?


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(2B)+(2B)' ?

 

[desertfox]

Hi electricpete

I remember from my old college days that a three legged stool is more stable than a four legged one and I found this pargraph:-

A three-legged base is always more stable than one with 4 or more legs. Going back to Geometry 101, remember that any three points not on a line define a plane. Any four points not in the same plane define space.

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

 

[mfgenggear]

Desertfox

three points are great to stabilize for measurement, it easier to levels, however with heavy machinery that has vibration. and moments (and I probably out of my league here)
would seem to my opinion easier to stabilize, make it more rigid. every heavy machinery I have ben around never used 3 points.
that said maybe it is easier to align as tugboat said. I say OP needs to consult the manufacture of the product and get better answers.

 

[mfgenggear]

to add the machinery I been around had adjustable screw to level the machines with a precision level.
then all points were solid on the foundation, then were bolted into the cement to prevent movement and vibration.
and when necessary the foundation was demo out and a deeper. and higher PSI cement was re install when necessary.

 

[3DDave]

I would expect that the frame of the machine is designed to limit deflection from it's own operation and using 3 points of support underneath prevents whatever it is fastened to from adding to that deflection.

That said, the maker of said machine would have installation recommendations.

 

[MintJulep]

Looking at curious cat's other posts, we might guess that they are installing this on a ship, or ship-like thing.

The deck May not be as stiff as the equipment manufacturer would want.

 

[mfgenggear]

if that's the case steel plates under may be helpful

 

[saplanti]

The following document page 65 Clause 16.1.1 mentions;

“Gimbals provide protection against G-forces generated by vessel pitch and roll movements and against deflection, twisting, and thermal growth of the mounting deck. Gimbals may be used for three-point package mounting.”

https://usermanual.wiki/Caterpillar/CaterpillarTaurus70UsersManual536177.1512634278/view

If this is the case you need talk to the turbo-generator supplier if this is applicable for your case.

 

[saplanti]

Additionally you need to look for the document was mentioned in the following clause;

“18.4 Mechanical Installation
18.4.1 TPIM-1010 Solar’s document TPIM-1010 “Package Installation Guideline – Compressor Sets and Mechanical Drives” outlines the responsibilities of the Customer and Solar regarding installation of the package. It provides guidelines for the installation of the standard package design and the interface with the turbine driven equipment”

“16.1.6 Deck Deflection Limits
The package supporting deck structure must have sufficient stiffness to maintain alignment of the turbine and driven equipment under dynamic vessel motion. Solar’s engineering specification ES 2379, “Offshore Product Motion Requirements for Oil & Gas Package Designs,” lists the maximum allowable deflections measured between the furthest mounting points. With analysis, these limits may be extended through the use of gimbals or AVMs”

“16.1.7 Angular Displacement and Acceleration ES 2379 lists the maximum allowable angular displacement and acceleration limits for marine applications. The Basic Duty category is met by the standard package without any additional modification. Moderate Duty and Severe Duty categories require modification”

 

[saplanti]

The following document has some interesting information;

http://www.gasprocessingnews.com/fe...age-design-requirements-for-fpsos—part-2.aspx

 

[saplanti]

The following has some additional information especially on mountings;

https://core.ac.uk/download/pdf/84815272.pdf