TL;DR

Shaft vibration on the Lightnin XE usually traces to an imbalanced or fouled impeller, or worn drive-end bearings. Measure shaft runout first, then inspect the impeller.

What you might see

rhythmic shaking of the mixer shaft
vibration measurable at the gearbox housing
shaft deflection visible at speed
noise worsens at specific RPM

Likely causes

Tap to mark as ruled out

Impeller imbalance from uneven coating buildup, bent blade, or missing hardware
Worn or pitted drive-end or intermediate bearings
Shaft deflection from bending load on a long unsupported shaft
Resonance at operating speed caused by the shaft natural frequency matching the run speed

Required tools

Dial indicator with magnetic base
Torque wrench with appropriate socket for impeller hub fasteners
Handheld vibration meter
Scraper or brush for buildup removal
LOTO kit

Safety first

Lock out the motor disconnect before approaching the shaft or impeller. The mixer can restart on control-system command.
Never attempt to measure shaft runout while the mixer is running.

Procedure

8 steps · ~60 min

1
Stop the mixer and lock out the motor disconnect. Verify zero rotation before approaching the shaft.
2
Visually inspect the impeller blades for buildup, bent sections, missing fasteners, or obvious physical damage.[1]
3
Clean any process buildup from the impeller blades with a scraper and measure the blade-to-blade weight balance with a scale. Blades should be within 5% of each other.
4
Check impeller hub fasteners for tightness per the Lightnin torque specification for the XE frame size.[1]
5
Mount a dial indicator on the tank wall or a fixed support and measure shaft runout within 150 mm of the bottom impeller. Runout exceeding 0.5 mm indicates shaft deflection or bearing wear.
6
If runout is within tolerance but vibration persists, the issue may be resonance. Log the vibration amplitude at several speeds between 50% and 100% of operating speed to identify a resonance peak.
7
Contact Lightnin application engineering if the operating speed coincides with a shaft resonance peak. A steady-rest bearing or a speed change may be required.[1]
8
If bearing noise is detected during the shaft rotation check, remove the gearbox and inspect the bearing races and rolling elements. Replace any bearing showing pitting, fluting, or cage damage.

Sources

SPX Lightnin XE Series Industrial Mixer Installation, Operation & Maintenance Manual, SPX Lightnin
SPX Lightnin XE Series Industrial Mixer Installation, Operation and Maintenance Manual, impeller inspection and shaft runout procedures (general)
View source

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