September 28, 2012
30+ Years of Alignment – A Look Back
By Stan Riddle
Back around 1982, when I made my first forays from machinist into mechanical maintenance, I remember hearing about coupling alignment while working at a now-defunct rope factory in North Carolina. I considered myself a decent machinist, although I had little experience beyond technical school. I remember a welder showing me how to align shafts.
“Straight edging,” he called it. No rim or face straight edging, just rim. Not even horizontal, as I recall – just vertical. No dial indicators. No lasers (I don’t think they had even been invented at that time).
Just straight edging.
Many of you may have learned it the same way. You may still be doing it the same way. And if you’re honest with yourself, “straight edging” is insufficient.
So, if a straight edge isn’t sufficient for precision machinery, what about dial indicators?
As a machinist, I knew how to use them. I performed my first rim and face alignment with dial indicators while working as a millwright for a wood products company in the mid-80’s, using shop-made brackets. Bracket sag? Never heard of it. TIR? Same thing.
Dials are definitely better than straight edges and calipers, but they still require experience and a good grasp of the math required to calculate shims and moves. And when you add the complexity of bracket sag and thermal growth – it becomes a long process, wrought with opportunities for error.
In my career, I have worked for companies that had “alignment gurus” – the guys you called to align the machines, because even though most of the mechanics knew something about it, only a few were good at it. And when the “guru” left or retired, you were back to straight edges.
And then, there were lasers!
The mill I worked for bought a laser alignment tool. And it was awesome, although the beam was invisible, the instructions were probably in German, and we had no training. But my work partner and I sat on opposing buckets – one on each side of the machine – and by much trial and error, learned to use it. But the soft feet, coupling backlash, bolt-bound, and thermal growth things slowed us down quite a bit, because we didn’t know what they were. We thought we were doing pretty well if we could align two machines per day.
Fast forward to today. Shaft alignment is an industry unto itself. I now work for a company that sells shaft alignment tools. Technological advances have made the alignment process fast, simple, and extremely accurate.
But the same alignment problems still exist, which we like to call the Five “T’s”:
- TIME – If you want to perform a good alignment, you must take adequate time to do it right. I’ve heard all the same arguments you have. “We’ve got it get it back on line!” “Just put it back together – we’ll align it on the next outage.” “The coupling is supposed to wear out – that’s its job!” And so on. Sometimes you have to “work slow to work fast”. You can complete the alignment properly, and quickly, and you may not have to do it again for many years.
- TRAINING – Many maintenance specialists today are woefully ignorant of what alignment is, and how to perform it. A generation ago, new millwrights learned alignment either from apprenticeship training, or by working with older, more experienced mechanics. Now many companies assume you’ll learn it by doing it, with little or no instruction as to what “it” is.
- TOOLS – The better the tool, the faster and more accurate the alignment will be.
- TOLERANCES – Aligning to zero is impossible to accomplish, and is a huge waste of time and effort. Find out what you company’s alignment tolerance is. If they don’t have one, you are welcome to use ours. But know when to stop.
- TROUBLESHOOTING – Learn the causes of alignment problems – things like soft foot, coupling looseness, bolt- and base-bound conditions, a proper tightening pattern, pipe strain, dirt on shims and feet. Know them, know how to check for them, and assume that every machine you align may have one or all of these problems.
Spend some time learning shaft alignment. Buy the best alignment tools your company can afford, and use them. Learn about the pitfalls of the alignment process, and what you can do to prevent them. Practice. Aim for a tolerance, and stop once you achieve it.
Make yourself an alignment “guru.”