A post-installation alignment check is the step that most commissioning procedures include but most maintenance teams skip. After completing the initial shaft alignment, fitting the coupling, torquing the bolts, and starting the machine for the first time, the natural assumption is that alignment has been verified and the job is done. In practice, the first 24¨C72 hours of operation introduce new conditions ¡ª thermal growth, baseplate settlement, bolt relaxation ¡ª that can shift the shaft positions from the initial aligned values. Checking alignment after this run-in period catches these shifts before they accumulate into significant bearing damage. This is equally important for rigid flange couplings ¡ª where any misalignment goes directly to the bearings ¡ª and for flexible tyre couplings, where misalignment accelerates elastomeric element fatigue.
Why the Post-Commissioning Check Matters: What Changes in the First 72 Hours
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Thermal Growth
The motor and pump reach operating temperature within 30¨C60 minutes of start-up. Each component expands according to its material and temperature differential ¡ª the motor frame, pump casing, and baseplate all grow by different amounts. Without thermal growth compensation in the initial alignment, the hot alignment will differ from the cold alignment by 0.05¨C0.3 mm depending on temperature differentials.
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Hold-Down Bolt Relaxation
New bolt assemblies ¡ª particularly on painted or slightly rough baseplate surfaces ¡ª relax slightly during initial thermal cycling as surface asperities compress and the coating yields under clamp load. This relaxation can be 5¨C15% of the initial torque value, enough to allow slight motor movement that shifts the alignment.
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Baseplate Settlement
On grouted baseplates installed within the previous 3¨C6 months, the grout continues to cure and may shrink slightly, causing small movements in the motor and pump positions relative to their initial installation values. On ungrouted or bolted-down baseplates, the first thermal cycles can settle the base slightly under the combination of motor weight and vibration.
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First Load Application
The machine’s first full-load run applies the actual working forces ¡ª motor rotor side-pull, pump hydraulic radial load, belt or pipe tension ¡ª that were not present during the alignment procedure. These forces can slightly deflect the machine structure, shifting shaft positions from the unloaded alignment values.
The Post-Commissioning Alignment Check Procedure
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Run the Machine to Thermal EquilibriumAllow the machine to operate at its normal load for at least 30¨C60 minutes before taking the alignment check readings. Thermal equilibrium is reached when the motor casing temperature stabilises ¡ª check with an infrared thermometer. This ensures that the alignment readings reflect the actual hot-operating shaft positions.
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Option A ¡ª Hot Check with Laser System RunningSome laser alignment systems can take measurements while the machine is rotating, using specially designed brackets and non-contact measurement. This is the gold standard for post-commissioning hot-alignment verification. The machine does not need to be stopped, and the readings reflect the true operating alignment.
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Option B ¡ª Immediate Post-Shutdown CheckIf a live-running laser check is not available, shut down the machine immediately after reaching thermal equilibrium, lock out and tag out, and perform the laser alignment measurement within 10¨C15 minutes. The machine temperature has not changed significantly in this time, and the readings approximate the hot-operating alignment. Re-start is delayed by the time needed for the alignment check ¡ª typically 20¨C40 minutes.
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Compare to Initial Cold Alignment ValuesCompare the hot-check readings to the initial cold alignment values recorded at installation. Differences represent the thermal growth differential between the motor and pump. If these differences are within the acceptable misalignment tolerance, no correction is needed ¡ª the thermal growth is within the coupling’s accommodation range. If differences exceed the tolerance, correct the cold alignment by introducing an offset equal to the measured thermal growth.
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Correct and Re-Verify if RequiredIf correction is required, apply cold-alignment offsets (deliberately misalign in the cold state by the amount of thermal growth, so that at operating temperature the shafts are co-linear). Re-check cold alignment after correction, then re-run the machine and take another hot-check to confirm the correction was effective.
Enables future checks to reference the same machine
Date and time of check
Full date; time relative to machine start-up
Confirms check was taken at thermal equilibrium
Cold alignment values (initial)
Angular and parallel in both planes from installation
Baseline for comparison with hot values
Hot alignment values (post-commissioning)
Angular and parallel in both planes
Reveals thermal growth differential
Thermal growth differential
Hot minus cold in each plane
Used to set future cold-alignment offsets
Shim stack at each motor foot
Shim thickness and material at each foot
Essential for future alignment corrections ¡ª avoids measuring from scratch
Next alignment check due date
12 months from commissioning or as scheduled
Builds the ongoing alignment maintenance programme
Frequently Asked Questions
How soon after installation should I check coupling alignment?+
A post-commissioning alignment check should be performed after the first 24¨C72 hours of operation at normal load and temperature. During this initial run-in period, several factors can shift the machine’s alignment from the initial cold alignment: thermal growth of the motor and pump reaching steady-state temperatures; relaxation of hold-down bolt preload from vibration; initial settling of the baseplate under operating loads; and, on grouted baseplates, early-stage grout curing that can cause slight movement. Correcting any alignment drift found at the 72-hour check establishes the stable hot-alignment baseline that subsequent annual checks can be compared against.
What are acceptable alignment tolerances for a post-installation check?+
The tolerances for a post-installation check are the same as for the initial alignment ¡ª the machine must be within specification regardless of when the check is performed. For flexible tyre couplings: within 0.10¡ã angular and 0.10 mm parallel in both planes. For rigid flange couplings: within 0.03¡ã and 0.03 mm. If the post-commissioning check reveals drift beyond these tolerances ¡ª which happens on roughly 20¨C30% of first-checks in our experience ¡ª correct the alignment before extending the run period. A machine that was correctly aligned at installation but has drifted after 72 hours of operation is almost always experiencing thermal growth effects that will repeat on every subsequent start-up.
Do I need to check alignment in both the vertical and horizontal planes?+
Yes, always. Misalignment occurs simultaneously in the vertical and horizontal planes, and the corrections for each plane are different ¡ª vertical misalignment is corrected by shimming (adding or removing shims at the motor feet), while horizontal misalignment is corrected by moving the motor laterally. Both planes must be within tolerance for the alignment to be acceptable. A machine aligned within tolerance in the vertical plane but misaligned in the horizontal plane will still damage bearings ¡ª both dimensions matter equally.
Can I check alignment without a laser system or dial indicators?+
A straight edge placed across the two coupling hub faces gives a rough indication of angular misalignment ¡ª any visible gap between the straight edge and either hub face is angular misalignment. A feeler gauge can quantify the gap. This is not a precision method and should not be used as the primary alignment check for any drive above 5 kW or 500 RPM. For smaller, lower-speed machines where precision is less critical, a straight edge check provides a useful minimum verification that alignment is not grossly off before first commissioning.
What should I do if alignment has drifted significantly between annual checks?+
A significant alignment drift between annual checks ¡ª more than 0.1 mm additional misalignment per year ¡ª is a signal that something structural is happening: baseplate settling, foundation movement, thermal growth not accounted for, or loosening of hold-down bolts. Correct the alignment, but also investigate the cause. Check all hold-down bolts for correct torque and soft-foot. Inspect the baseplate for cracking or grout deterioration. If the machine is on a raised frame or structural platform, check for structural deflection under load. Treating the symptom (misalignment) without finding the cause will result in the same drift recurring after the next correction.
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