TL;DR
Vibration at 1x run speed is usually misalignment; vibration at 1x and 2x together points to impeller unbalance. Check coupling alignment first, then impeller condition.
What you might see
- elevated vibration at bearing housings
- rhythmic knocking under load
- premature bearing failure pattern
- visible coupling wear
Likely causes
Shaft misalignment between the pump and driver, angular or parallel
Unbalanced impeller from erosion, product buildup, or casting defect
Worn pump or driver bearings amplifying any imbalance
Soft foot at one or more mounting bolts causing the pump frame to flex
Required tools
- Laser alignment tool or dial indicator with magnetic base
- Shim stock (pre-cut)
- Torque wrench
- Vibration meter
- LOTO kit
Safety first
- Lock out the driver before handling the coupling or opening the casing.
- Replace the coupling guard before re-energizing.
Procedure
- 1
Lock out the pump driver.
- 2
Check for soft foot: loosen each foot bolt one at a time. If the frame lifts more than 0.003 inches at any foot, shim that foot before proceeding.[1]
- 3
Set up a laser alignment tool or dial indicator bracket on the coupling halves.
- 4
Measure parallel and angular offset. Goulds specifies maximum 0.002 inches parallel and 0.001 inches per inch of coupling diameter angular.[1]
- 5
Adjust motor position with shims and horizontal jacks to bring both values within spec. Re-check after torquing each foot bolt.
- 6
If vibration remains after alignment, remove the impeller and inspect for material buildup on the vanes or visible erosion asymmetry.
- 7
Clean buildup or replace a heavily eroded impeller and re-test vibration at operating speed.
Sources
Goulds 3196 i-FRAME Process Pump Installation, Operation & Maintenance Manual, Goulds Pumps (ITT)
Goulds 3196 i-FRAME IOM, shaft alignment and soft-foot procedures (general)
View source
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