The maintenance team did everything right: They shut down the motor, took precise shaft alignment measurements, and made the necessary adjustments. At room temperature, the numbers were perfect. But a few hours after startup, something was wrong.
The machine was vibrating more than expected. Bearings were running hotter than usual. Couplings showed signs of premature wear. Within weeks, the team troubleshoots again, wondering what they had missed. Most technicians assume that if a machine is aligned at rest, it will stay that way. But once the system is up and running, heat changes everything.
Thermal expansion is the silent force that changes shaft alignment when temperatures rise. As rotating equipment heats up, metal components expand — sometimes by mere thousandths of an inch, sometimes by millimeters. High-temperature environments, such as power plants and refineries, are especially vulnerable to this thermal dynamic change.
Staying ahead of thermal growth can be the difference between smooth operation and frequent breakdowns. Technicians can benefit from knowing how to factor in heat expansion during alignment and account for changes as machines heat up.
The Invisible Shift: How Heat Changes Alignment
While most teams understand that heat causes expansion, they don’t realize how unpredictable it can be. Uneven heating, varying material properties, and different load weights mean thermal growth does not always happen the way you would expect. And because thermal expansion occurs in all directions, alignment changes are not always linear or even. One part of the machine may heat up faster than another, or one material may expand more than its nearby counterpart.
Therefore, alignment that looks perfect in the workshop seems to suddenly turn into misalignment in the field. This can lead to:
- Excessive vibration
- Increased energy consumption
- Premature bearing and seal failure
- Unplanned downtime
And shaft misalignment is not the only concern. If a machine runs hotter than expected, it could signal bearing wear, electrical inefficiencies, or other underlying issues. Even with proper lubrication, friction still generates heat. Motors and electrical components add to the load as resistance builds in their circuits.
Left unchecked, what starts as thermal expansion alignment issues can turn into a much bigger reliability problem — costing thousands in downtime, repairs, and lost production.
The Calculation That Changes Everything
So, how do you prepare for thermal growth misalignment, given its unpredictability and variability from one machine to the next?
You start by understanding exactly how much movement is happening — and where. That means measuring how much thermal expansion you can expect for each machine.
To predict thermal expansion, you need three numbers:
1. Temperature change (T) – Difference between ambient and operating temperature
2. Shaft length (L) – Distance from the machine base to the shaft centerline
3. Material coefficient (C) – The rate at which the metal expands per degree of temperature change
Thermal Growth = T x L x C
For example, if a stainless steel shaft starts at 70 degrees Fahrenheit, heats up to 130 degrees, and is 10 inches long, it will grow: 60 × 10 × 0.0000074 = 0.00444 inches.
That’s just under five-thousandths of an inch — small, but enough to throw rotating machinery out of alignment.
How to Stay One Step Ahead of Thermal Growth
Knowing how much a machine will expand is the first step — actually compensating for it is the next.
Here’s the good news: Thermal growth does not have to be a guessing game. By planning for it during alignment, you can ensure shafts stay aligned within spec when it matters most. Instead of realigning after thermal growth happens, you can predict movement by pre-entering the thermal growth targets into the RotAlign Touch, adjust accordingly, and get it right the first time. Here’s how:
Identify Thermal Expansion Risks
Review your equipment’s past temperature data and measure actual operating temperatures instead of relying on estimates. Manufacturer specifications offer a useful starting point, but confirming them with real-world data ensures greater accuracy and reliability.
Let the ROTALIGN Touch Thermal Growth Calculator Do the Work
With RotAlign Touch, adjusting for thermal growth is simple.
Just enter three values:
- Starting temperature (when the machine is off)
- Operating temperature (when running at full load)
- Distance from the machine base to the shaft centerline
The system automatically calculates the exact thermal growth compensation needed — no complex math required.
See Changes in Real Time
RotAlign Touch’s Live Trend feature tracks how shafts move as the machine dynamically heats up, allowing you to see whether thermal growth occurs evenly or if misalignment develops in one direction more than the other.
The system uses high-precision laser sensors to monitor positional changes as the machine moves from cold start to full operation. Once the machine turns on and begins to heat up, the device logs every positional shift — tracking both vertical and horizontal thermal growth as temperatures rise. When the machine reaches full operating temperature, the system captures the final alignment state. Technicians can use that data to set precise alignment targets, ensuring that once thermal expansion occurs, the shafts are positioned exactly where they should be. Therefore, by aligning based on actual machine behavior, you eliminate the trial and error of correcting misalignment after startup.
Live Trend also monitors pipe strain and process-related machine movement during the run-up and coast-down phases, giving you a complete picture of how forces act on your equipment throughout its operating cycle. And because alignment is only part of the equation, Live Trend also tracks machine vibration, helping catch early warning signs of imbalance, excessive strain, or developing faults before they escalate.
Align Once, Run Smoothly
With RotAlign Touch at hand, accounting for thermal growth is quick, precise, and effortless — so you can align with confidence and keep your machines running at peak efficiency.
A global turbine manufacturer learned this firsthand. Their machines were perfectly aligned at shutdown, but after startup, everything changed. High speeds and extreme temperatures caused shafts to shift unpredictably, creating vibration issues that traditional alignment methods could not catch.
Using RotAlign Touch, they monitored shaft position throughout warm-up and full operation. The data revealed why their machines were not staying aligned and what needed to change.
Are You Aligning for the Future?
You would not set your watch to the wrong time and expect to be on schedule. So why align a machine at room temperature and expect it to stay that way when it’s running hot?
With RotAlign Touch, you can factor in thermal expansion before it throws off machine alignment. In the real world, machines don’t just run — they dynamically move, expand and settle. And if your alignment does not account for that, you will always be one step behind.
With RotAlign Touch, you can align for how your machine runs, not how it rests.
