Alignment: The Hidden Source of Vibration — and How to Catch It Before It Catches You

Why even perfectly balanced machines start shaking once they warm up

By Josh Iris, President, Ace Electric Motor & Pump Co.

If you’ve been around rotating equipment long enough, you’ve probably seen this one. You rebuild a motor, line it up perfectly, balance the rotor to G 1.0, and it runs smooth as glass at startup. Ten minutes later, the vibration starts creeping up.

You double-check everything — balance, runout, coupling, base — all good. You pull the laser out again just to make sure. Alignment looks perfect.

And yet, the machine keeps shaking once it warms up.

So what’s going on here? Nine times out of ten, it’s not the motor, the balance, or your technique. It’s thermal growth.

When “Perfect” Alignment Isn’t Perfect at All

Most alignments are done cold, on equipment that hasn’t reached operating temperature. On paper, everything looks dead-on. But once the system heats up and starts doing work, things begin to move — especially in blowers, pumps, and compressors that see big temperature swings.

Take a multi-stage blower as an example. Air comes in cool and leaves the discharge end sometimes 100°F hotter. That temperature rise causes the discharge end to grow taller than the inlet end. The result is angular misalignment between the motor and blower shafts as the equipment expands unevenly.

Now, because everything’s bolted to a rigid base, that thermal growth has nowhere to go. It literally twists the shaft centerlines apart as the metal expands. And that’s when your vibration starts climbing, bearings start loading, and the finger-pointing begins.

credit Easy-Laser

The Science Behind the Movement

Here’s the math behind what’s happening. For cast iron, the coefficient of thermal expansion is 0.0000067 in/°F per inch.

If your blower frame is 20 inches tall and the discharge end runs 100°F hotter than the inlet, it’ll grow roughly 0.013 inches on that hot end.

Thirteen thousandths doesn’t sound like much — but in the world of alignment, that’s huge. It’s enough to throw even a perfectly balanced machine out of tolerance.

Field Tip: Always record both cold and hot readings. The difference tells you everything about how your machine really behaves.

Why It Matters

That small amount of thermal growth can load bearings unevenly, chew up couplings, cause seals to leak, and send your vibration trending in all the wrong directions. Most times, the motor or rebuild gets blamed when the real culprit is simply physics.

This is where good reliability practice comes into play — measure it, don’t guess it.

How We Measure Thermal Growth

At Ace Electric, we’ve started using Easy-Laser’s XT770 system with the EasyTrend app and DM brackets to actually see how machines move as they heat up.

This setup lets you measure alignment in real time as the equipment warms up. Here’s the simple version of how it works:

1. Install the DM brackets on both the motor and driven machine.

2. Use the EasyTrend app to record live movement in the horizontal and vertical planes.

3. Start the machine and let it reach normal operating temperature.

4. Watch how the shafts shift and expand on screen — that’s your thermal growth.

5. Adjust your cold alignment accordingly so that everything lines up hot.

No guessing. No “that’s probably close enough.” You get real numbers that reflect what’s happening under actual conditions.

Credit Ludeca Inc

Real Example from the Field

We had a blower setup where vibration kept spiking after every warm-up. Using EasyTrend and DM brackets, we saw the discharge end lifting about 0.015 inches due to thermal growth. Once we realigned cold to compensate for that lift, vibration dropped from 0.35 in/s to 0.07 in/s RMS — and the bearing failures stopped.

Sometimes, the problem isn’t your alignment technique. It’s the timing of your alignment.

A Word for the Techs and the New Guys

If you’re new to alignment work, here’s what I wish someone had told me early on: alignment isn’t static. Machines move — they grow, twist, and settle as they run. A laser only shows you where things are right now, not where they’ll be 20 minutes into operation.

Thermal growth is invisible until you measure it. Once you see it, you can fix it — and that’s where real reliability starts.

Wrapping It Up

Thermal growth is part of the game. You can’t stop it, but you can plan for it. The difference between a good alignment and a great one is knowing how your machine behaves when it’s hot — not just when it’s sitting cold on the floor.

Tools like the Easy-Laser XT770, paired with EasyTrend and DM brackets, make it possible to see that movement, document it, and compensate for it.

Less vibration. Longer bearing life. Happier customers.

And that’s what we’re all after. #KeepItRunning

Special thanks to Ludeca, Inc. for providing the Easy-Laser XT770 system and dynamic measurement tools featured in this article. You can learn more about the EasyTrend dynamic measurement system at www.ludeca.com.

Technical reference and educational content originally inspired by EASA (Electrical Apparatus Service Association) technical publications. Images and diagrams referenced in this article are credited to EASA, Ludeca and Easy-Laser