We have lazers but seasoned machinist won't use. Say they dont work.(new rotalign)Anyway currently use rev. alignment and tolerances are as follows. Distance between indicators(inches)x .001. No matter at what radius or rpm. Any data on correct tolerances. Thanks!!

Mail me for a tolerance chart and procedure chart (works for all methods including laser). Indicator Reverse and Laser alignment are equally good if used properly. Both laser and indicator methods may have graelims if not addressed in a given method.

Speed dictates tolerance as does precision and type of coupling. Typically a run-of-the-mill application (1800 RPM, A-F brgs, gear coupling): 3 mils on the Rim or parallel and the tangent of the tolerance angle X indicator span. To calculate the angular tolerance for above 1/60th of a degree or 1 minute angle multiply 0.00029 X distance between indicators (10" = 3 mils tolerance). So, 3 mils/10" is basic. Take the two indicator readings and divide by 2 and this will give you the mils deflection per your span. If on a conventional setup indicator A reads -10 and indicator B reads 18 mils with 10" span you would have 4 mils per 10 inches with a parallel offset of five mils. Natually you must have already substracted the effect of gravity prior to this calculation as example give was already corrected for SAG.

Dear Sam,

May I also have a copy of the tolerance chart and procedure please. It's useful having this handy. Thank you.

my mail: gerjes@maltanet.net

Sam has some great info.

Here are recommended alignment tolerances from EASA

EMS_EASA_AlignmentTolerances.pdf (53 Kb, 70 downloads)

Here are recommended tolerances from Pruftechnik (sp?)

AlignmentTolerancesPrufTechnik.PDF (174 Kb, 58 downloads)

Here are recommended alignment tolerances from EPRI/Ludeca

EPRI_LudecaAlignmentTolerances.ppt (192 Kb, 60 downloads)

Thanks Pete! Here's an overview - my tolerance are a little tighter than most but in keeping with Al Campbell and Jack Essinger (all from the older days when we were all a bit younger). Jack's son stil has the business I gather and still has products available.

Philosophy: time is money! if you can use a tight tolerance and do one-shot alignment then your spec is not too tight and cost justifible. Proper procedures will allow you do do one-shot alignment often and even as a rule especially on large equipment.

Alignment_Procedures.doc (22 Kb, 68 downloads) Procedures

And: from company posted intranet. You may also want to visit http://www.pdmengineering.com and I have another site if interested.

AlignTolChart.doc (166 Kb, 56 downloads) Tolerance

Many years ago (probably early 70's) I implementated reverse dial alignment on the test stands at Philadelphia Gear. We used a tolerance of TIR = (11 x span)/RPM and it worked well (span is the distance between "flex" points and is expressed in inches. This was actually pulled from some Exxon procedures at the time. Rarely did we ever have to realign a unit under test and gearboxes under light load are finicky. We did do one modification in the sense that we took into account the anticipated shaft motions since in a typical gearbox with fluid film bearings one rotor is likely to move from the bottom of the bearing to very near the top. We implemenated a programmable calculator to do the work in calculating "moves" for the test stand technicians. The program worked exceptionally well in that it was possible to align a unit in very short periods of time and do it right the first time. Prior to that the test stand used rim and face and often we had to touch up alignment to get a unit to pass test.

John from PA

No one shoe fits all feet. Typically, indicator reverse and/or Long Spacer Coupling methods work well and the best best is most general situations. Sometimes the flexibility of bracket setup on lasers give a wide range for large shafts and coupling spans. All methods are valid in the hands of a qualified technician. A dedicated set of brackets for large machines work well over universal sets. But for long spans such as drive shafts for cooling tower and such type equipment, Long Spacer Coupling method is by far the best, fastest and most accurate. I have programs written to cover Long Spacer Coupling, Rim & Face and Indicator Reverse. Generally the long spacer types are a one-shot deal everytime.

I've found if you put the units to be aligned in a stress free enviornment, they'll stay put there over a long period of time. I've checked machines 3 years later and they were within 3 mils - so, not too shabby!

And some more info - also has vibration field guide - http://members.tripod.com/pdm-engineering/id6.htm

http://www.pdmengineering.com also has info

Not everything is sales!

I appreciate the the info you guys gave me. It was exactly what I was looking for. Thanks!