Hi guys,

Is it a good practice to loose the coupling bolts while aligning machines using laser?

Have a nice day!!

Much too broad a statement: which specific coupling?

If you rough align within reason; falk grid type, zurn, fast, etc., gear types, dodge, woods, pin ---- many and most do not need to be loose.

What are you thinking of specificly?

Jenish,

I do on most all couplings (except one with a rubber insert like a woods).

Dave

As Sam said, the question is much too broad. However, during rough alignment, I usually do temporarily loosen the setscrews on one of the coupling halves. I remove the grid, spider, whatever is in the way.
Move the coupling halves together so they touch. Then, you can easily see any misalignment. Of course, the first thing to look for a gap between them, top or bottom. On the machines I align, the coupling needs to be complete and tight during precision alignment.

Webcruiser,

Why does the coupling matter if you are doing shaft center alignment?
Or do you use dial indicators with rim/face?

Dave

With dynamic alignment you don't want anymore looseness than you have to have. The alignment using this method aligns the concentric centerlines of the bearings forming a perfect straight line. So a bent shaft or run-outs won't be seen by the data acquisition device. Hence it is necessary to perform run-out checks.

Generally speaking; the in-house guy likes Indicator Reverse, Long Spacer Coupling or Rim & Face whereas the consultant likes laser. I think the biggest reason is - the in-house guy has the advantage of having the correct brackets or dedicated brackets which are better, faster and less expensive. The outside guy needs a flexible set that can be configured to a wide variety machine configurations.

All methods are good in the hands of qualified people. But, some methods fit a machine better than others. I just did a cooling tower using the "Long Spacer Coupling" mehtod. It is faster and better than laser. Achieveing alignment is getting the job done regardless of your method as long as the numbers are reality and meaningful.

If the coupling is similar to the type that uses an elastomer directly attached to the metal band that bolts to the coupling hubs and it was tightened up with the hubs misaligned, there will be a limit as to how far you can move before you need to loosen the bolts and let the coupling relax.

Ken

quote:

Generally speaking; the in-house guy likes Indicator Reverse, Long Spacer Coupling or Rim & Face.

Sam,

You and I play in different neighborhoods.

Dave

Dave,

Unsure as to what you're saying?

The in-house people can have dedicated machine brackets always available for that given machine. They are custom made for that machine. Swing a bracket on, no adjustments - it fits correctly everytime and ready to take measurements with in the shortest time, accurate and repeatable. So you have speed and accuracy.

On the other hand; the consultant travels from job to job and needs more compact universal sets. They have to be setup for each machine and calibrated before each use. So you don't have the speed. Accuracy should be the same.

I've done MI to FL to TX to Saudi - big hood.

quote:

I think the biggest reason is - the in-house guy has the advantage of having the correct brackets or dedicated brackets which are better, faster and less expensive.

Sam, are you saying that indicators are "better and faster" than using a laser? If so, you've been reading/listening to too much Piotrowski.

In 80% of alignment situations, a good laser, in the hands of an experienced, well-equiped consultant will give faster, and usually better, results than indicators. One should use what works best in a given situation. That's not always a laser, but it's definitely not always indicators.

quote:

Dave,

Unsure as to what you're saying?

Sam,

I've been all over this country, and several foreign ones too (missed Saudi, didn't accept Aramco), and I guess I just haven't been to the right facilities in these strange lands (the playgrounds I spoke of). I can't remember one of these facilities I've been in for various jobs having dedicated brackets made up for any particular machine. Shoot, most are lucky if they have someone knowledgable enough to use dial indicators. Many still use the ole eyeball, or keystock and feeler guages.
I agree with your reasoning with the laser and brackets for a consultant. I have 2 different magnetic brackets, a bolt hole bracket, and a custom length of chain for my regular brackets. You're right, you never know what you're going to get into.
Not trying to be difficult, I've just never seen anyone anywhere who could open up a tool box and have more than a standard set up for dial indicator alignment (The millwrights working for Bucyrus Erie field service probably come closer than anyone). They are just rare in my playgrounds.
But maybe Jesus had the answer as to why I don't see them when he said "It is not the well who need the doctor"

Dave

Hi guys,

Thanks for all the good comments..

Actually, i intentionaly made the question broad because i was looking for a broad answer!!

Like Dave, I normally will loose the coupling bolts before alignment and now somebody is questioning on this.. According to them, itz a waste of time to loose the bolts if you are using Laser!! Is there any advantage in loosening the bolts?

Have a nice day!!

Jenish,

I loosen the bolts on gear couplings, grids, Thomas, Rubber Tire type, or any coupling I think may hold the two shaft ends tightly together, especially if one or both are sleeve bearing mmachines, or any (like Thomas and tire type) that I feel may effect the vibes after alignment. The Thomas will "oil can" and the rubber tire (or neopreme, or whatever) often takes a "set" and doesn't like being moved any way. SOmetimes it's just best to replace that element (if they have one )

Dave

quote:

Posted 02 May 2008 02:19 PM Hide Post
quote:
I think the biggest reason is - the in-house guy has the advantage of having the correct brackets or dedicated brackets which are better, faster and less expensive.


Sam, are you saying that indicators are "better and faster" than using a laser? If so, you've been reading/listening to too much Piotrowski.

In 80% of alignment situations, a good laser, in the hands of an experienced, well-equiped consultant will give faster, and usually better, results than indicators. One should use what works best in a given situation. That's not always a laser, but it's definitely not always indicators.

Rusty all methods are valid. All give the same accuracy else you don't know what you're doing.

95% of the time 'Long Spacer Coupling' method is better and much faster than laser on cooling towers if not 100% of the time.

I have my own book (~330 pages) thank you, and use tighter tolerances than Mr. Piotrowski and maybe a little different approach. But I've only been doing this for 40 years.

Was using lasers back in the '70's and shooting through mirrors and around machines and yes with optics and such as well. Used Dynalign (Dodd Bars) and Acculign (Jack Essinger).

If you setup on a machine and use a laser; dial indicators should get the same results else you have a seriour problem; same shim change and same lateral shift - if not one of your methods or procedures is not good enough.

One must calibrate or check calibration each and every time you use a laser on every job. Also one must index readings with certain laser systems on certain machines - I'm sure you do this. Dedicated brackets for their specific machines are stamped with SAG values and only need attaching which is extremely fast and give accuracy to 0.001" or better if you choose to use higher resolution indicators - you can work to 0.0001" if you want and the machines demand.

Many times indicators are faster and the fastest method and give the best attainable results.

I can take a set of readings in Indicator Reverse and tell you what the other methods will read and plot them out.

Regardless; all alignment should have a final reading and show final machine positions and filed in a record and kept for future reference - I'm sure all do this as well!

If you can't use dial indicators to produce these results, then how do you know alignment and able to function with a laser? I will contend that if you can't produce alignment with indicators you probably can't do it with lasers either.

This is not directed to anyone specific but to everyone! All in maintenance who are responsible for machine setup should know the fundamentals of machinery setup and alignment.

quote:

One must calibrate or check calibration each and every time you use a laser on every job.

Why is that, Sam? How did you deduce this? Where does this come from? I've only been doing this 27 years, but I've never heard that. Do you "calibrate" your dial indicators before every job? If not, why not?

Yes I do! Never ASSUME anything. You don't know if your readings are correct if there's no point of reference. I was taught as a professional; you document, document, document!!!

If you see an optical guy setup, the first thing he/she does is calibrate and then take readings - move, and re-calibrate - ALWAYS!

If you use a liquid vial level - check calibration. These things are 'must', not options.

And address 'indexing' - when do you index machines when using your method? All things that can affect/effect your job must be considered.

Jenish
To answer your specific question...
I was taught that you loosen bolting on "hard" couplings (e.g. on most turbines that I'm familiar with). As I understand it, the purpose is to ensure that you dont introduce coupling strain into the readings.
For the majority of my alignment jobs, the equipment have "flexible" couplings which have enough play they dont put significant strain to affect the readings. This IMPLIES that I have rough aligned the shafts BEFORE I even put the alignment brackets on (as well as all the other gremlins you fix before you align - bent shaft, soft foot, etc).

Regards
Jim Powers

quote:

Why does the coupling matter if you are doing shaft center alignment?
Or do you use dial indicators with rim/face?

RSS_Dave,
Sorry, I just got back to the forums (had a long weekend). I totally agree, the couplings do not matter for shaft alignment. The method I described is just for very rough alignment, before indicators or lasers are strapped on the shafts.

Does anybody use an Excel spreadsheet instead of plotting on graph paper (for reverse dial indicators)? I haven't seen it mentioned on this forum.

Yes!