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The laser alignment report looks good. The motor is bolted down, the coupling is assembled, and the pump starts. Then vibration appears—or the next alignment check no longer matches the first one.

That does not automatically mean the millwright made a bad alignment. The first run changes the machine’s conditions. Temperature rises, the pump fills and pressurizes, and forces from the connected piping become part of the operating system. A cold alignment is valuable, but it is only one measurement in that process.

Thermal growth changes shaft position

As a pump and motor warm up, their components expand. They may not grow by the same amount or in the same direction. A machine aligned perfectly shaft-to-shaft while cold can move away from that position at operating temperature.

Some installations therefore use a specified cold alignment target: the shafts are intentionally set at an approved offset so they move closer to the desired position during operation. That target should come from the equipment manufacturer or engineering plan. It should never be guessed from how hot the casing feels.

Piping can move the pump

A pump should not have to hold connected piping in place. Filling, pressure, temperature changes, and insufficient pipe support can put force on its nozzles and shift the casing or base. This is why the condition of the piping matters to the millwright as much as the position of the motor.

Compare alignment readings from the stages specified in the installation procedure, including after piping is connected. If the readings change unexpectedly, investigate the piping and supports with the pipefitting and engineering teams. Moving the motor to compensate for an unresolved piping load may make the coupling look better while leaving the pump under strain.

Soft foot can hide in a good-looking report

Soft foot means a machine foot does not sit properly on its base. Tightening the hold-down bolts can distort the frame and change the shaft position. If the condition was not corrected before alignment, later tightening or movement may reveal it.

Check the mounting surfaces, shims, foot contact, and hold-down condition under the approved procedure. Correct the support problem before repeating the precision alignment.

Record what happens during the first run

The first startup provides information the cold check cannot. Record temperatures, vibration, bearing condition, unusual noise, and whether the pump operates at its intended conditions. A change in vibration deserves investigation, but vibration alone does not prove misalignment. Hydraulic conditions, looseness, bearings, and other faults can produce similar symptoms.

If the plan calls for an operating-condition or post-run alignment check, follow its measurement method and timing. A machine begins cooling after shutdown, so a “hot” reading taken much later may not represent its running position. Keep the original cold report and the follow-up measurements together.

Correct the cause before moving the motor

A useful troubleshooting order is to confirm the measurement, review the specified thermal target, check soft foot and base condition, and investigate piping loads. Then make any alignment correction required by the approved tolerance and operating target.

Isolate and verify the equipment before removing guards, adjusting feet, or working at the coupling. After correction, document the final alignment and check the machine again under operating conditions as the commissioning plan requires.

The takeaway: the first run tells the crew how the installed system behaves. Good millwright work connects the cold alignment report to thermal growth, piping forces, base condition, and the pump’s actual operating data.

Editorial fact-check, separate from the article: Shaft-alignment guidance covers cold targets for thermal growth and soft-foot checks; Hydraulic Institute guidance explains how piping loads and operating conditions can affect pump alignment.