Analysis of causes and countermeasures for abnormal vibration of submersible pumps

I. Diagnosis of the root cause of vibration

1.1 Mechanical vibration (accounting for 45% of the causes of failure)

· Impeller dynamic balance failure (＞0.5mm/kg needs to be corrected)

· Bearing clearance exceeds the standard (radial clearance＞0.15mm)

· Coupling centering deviation (angle error ≥0.05mm/m)

1.2 Fluid dynamic vibration (accounting for 35% of the causes of failure)

· Cavitation phenomenon (NPSHa＜NPSHr+0.5m)

· Eddy current excitation (risk surges when flow rate＞2.5m/s)

· Medium gas content exceeds the standard (＞5% volume ratio)

1.3 Structural resonance (accounting for 20% of the causes of failure)

· Natural frequency and speed frequency coincide (±10% danger zone)

· Pipeline support spacing is too large (carbon steel pipe＞3m without support)

II. On-site investigation process

1. Vibration value detection: If ＞4.5mm/s, then (spectrum Analysis)

2. Determine whether it is high-frequency vibration?

3. If yes: check bearings/gears

If not: check whether it is low-frequency vibration?

4. If it is low-frequency vibration: check impeller/coupling

If it is not low-frequency vibration: check fluid system

III. 7 solutions

3.1 Mechanical adjustment

Impeller G6.3 dynamic balancing (residual imbalance <8g)

Use laser alignment instrument for correction (error control within 0.02mm)

3.2 System optimization

Add inducer to improve cavitation

Install damper at outlet (rubber flexible joint recommended)

3.3 Intelligent monitoring

Install wireless vibration sensor (recommended 100Hz sampling rate)

Establish vibration trend map (warning value set to 4.5mm/s of ISO10816-3)

IV. Preventive maintenance plan

Weekly: Check anchor bolt torque (M20 bolts require 450N·m)

Monthly: Lubricating oil particle size detection (within NAS Class 8)

Yearly: Perform modal analysis to verify structural natural frequency