First
off let’s give credit where credit is due on these universally accepted
Alignment Tolerances - Ludeca, Inc. and Ken
Brook the developer who was the Ludeca Chief Engineer at the time - 1986!
If someone else has told you that they came up with the tolerances shown below
do not believe them as we were there when Ken did his great work! This Alignment
Tolerance table did not exist before Ludeca developed it - period!
Ludeca
felt that as the leader in laser alignment that they needed Alignment
Tolerances that could be given to their customers. In comparing the various
Equipment Manufacturers tolerances (notice we did not say Coupling Manufacturers)
Ken Brook saw that they pretty much fell in line, with each other, when compared
on the operational RPM.
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| Tolerance Card (click) |
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Before
we go further - ya’ll know it is RPM not
RPM’s as you may have seen or heard elsewhere.
RPM is both singular and plural, for example: 1 RPM and 1,775 RPM - that’s
right Revolution or Revolutions Per Minute depending on how many! If you have
been hearing RPM’s the person is actually saying Revolutions Per Minute’s
and there are not many places that would apply on planet Earth - even in racing
engines!
Back
to Ken Brook’s work. Ken decided to look
deeper into the Equipment Manufacturers (Pump, Gearbox, Motor etc.) tolerances
by actually calculating what it would take to get the full rated life out of
the Bearings! (Notice we did not say Couplings as we need
to align for the Bearings and if you do not know that your program is
in serious trouble!) Ken found that we needed to align a little better than
what was previously thought and calculated what is now the Excellent column
on our “Tolerances For Shaft Alignment”
card. By the way, the Manufacturer’s tolerances evolved into the Acceptable
tolerance column.
Note:
These Alignment Tolerances are an integral part
of the alignment program on the Prüftechnik AG, the German Manufacturer's,
Rotalign® Ultra, Rotalign® Pro, Rotalign®,
Optalign® smart, Optalign® Plus, Aligneo®,
ShaftAlign®, smartAlign®, smartScanner®
and PocketALIGN® Laser Shaft Alignment systems! These laser system use
the RPM you entered by comparing your actual
alignment to the built in Tolerances For Shaft Alignment
and gives you an on screen indicator if your alignment is Excellent,
Acceptable or poor!
Yes we show a Smiley face and you would be smiling
too if you were using one of these Prüftechnik
AG systems!
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| New Rotalign® Ultra is Unequaled! |
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| New Optalign® smart with Bluetooth |
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| New Aligneo® |
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| Optalign® Plus Series |
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| Rotalign® Pro EX Intrinsically Safe |
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Recently
we were asked what we thought of “Alignment at the
Feet”! Well that makes about as much sense as “eating
with your feet”! When you have done an alignment using the Alignment
Tolerances shown above, whether you are “short
coupled” and using Gap/Offset or have a Spacer
Shaft, you should not have any alignment related vibration! That was
Ken’s point - when he looked at what a bearing
needed to last the rated life - he created the Excellent column in the table!
On
large machines you may end up with some large numbers at the feet but that can
be explained with a simple Rise over Run example. Do you worry where a trailer’s
wheels are when you hitch it to your car or truck? We doubt it - as you are
very concerned about the hitch (or in our case the coupling)! If
you have been convinced that you need to align at the
feet then you need a class taught by someone who has done alignment
and YOU need to get out there and do some alignments!
To be completely honest with you, if you have not done any alignments (and understandably
some of you haven’t as it is not your job) then you do not have the full
picture!
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"The only correct way to express shaft alignment tolerances is in terms of alignment conditions at the coupling" per Heinz P. Bloch, a top Alignment Authority, as published in the December issue of PUMPS & SYSTEMS.
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© Copyright 2003 Voelzow & Company, Inc. Wingate, North Carolina
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