0.02mm/m leveling on gearbox on an FPSO

[curious cat]

0.02mm/m leveling on gearbox on an FPSO.
Is it achievable , considering FPSO is a floating structure that rolls constantly .

 

[MintJulep]

Relative to...

 

[Artisi]

Relative to.... Maybe advertising...

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.)

 

[IRstuff]

4 arcsec is not impossible; need a reference reflector cube and high-end theodolite

https://www.precisionoptical.com/precision-optics/alignment-cube/

https://www.swisstek.com/images/wild_leica/TM6100A_UserManual_v1.0.2en_en.pdf

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[TugboatEng]

With gearboxes in marine structures we are not so concerned about level, only alignment.

 

[Pud]

Something lost in translation?


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[dik]

I was not aware of reflector cubes... thanks IRS...

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[mfgenggear]

irstuff

in my old days we were lucky to obtain .001 inch (.0254 mm) tolerance with theodolite system
how precise does the one in your post post obtain, being out of the loop.

https://en.wikipedia.org/wiki/Theodolite

 

[IRstuff]

Theodolites measure angles, so 0.001 inches corresponds to about 3.5 ft, assuming 0.5 arcsec, but that's awfully close range.

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[dik]

My theodolite (Hilger and Watts, old mechanical one about 80 years old, and in excellent shape) does 5 sec...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[SwinnyGG]

Modern robotic total stations are capable of distance measurement in the range of +/- 2-3 ppm, and angle measurements of .5 arcsec or less. So how accurately you can measure depends on how close you are to your target. If you're right on top of it, you'll get to the micron. If you're 1500 m away, you're going to get 1-2mm at best, assuming free stationing. If you're using an accurately laid reference grid, you can get =/- 3 ppm over any length you want; the only limiting factors will be line of sight and the accuracy of your reference grid.

 

[mfgenggear]

so being it is accurate to 4 arc sec, then to get the best measurements getting close as possible.
we use to do both level and distance for jigs and fixtures, and station lines for aircraft and rockets.
so it can be done surely current equipment is more precise. and repeatable.
great care must be used to obtain the correct measurements.