Vibration Analysis of Compressor Piping Using VibroMicro
1. Background and Testing Requirements
In air conditioning systems, compressor piping vibration presents significant challenges for reliability and noise control. Excessive vibration can lead to:
Fatigue Failure: Cracking at welding points and joints
Noise Issues: Radiation of structural-borne noise
Performance Degradation: Interference with normal compressor operation
Safety Concerns: Potential for refrigerant leakage
Traditional limitations:
Contact sensors alter the dynamic characteristics of lightweight piping
Limited measurement points provide incomplete vibration data
Difficulty in visualizing complete vibration patterns across complex piping layouts
2. Experimental Setup
2.1 System Configuration
Core Sensor: Dynatronic VibroMicro VM-S-100 Laser Doppler Vibrometer
Scanning System: Automated positioning platform for multi-point measurement
Analysis Software: VibroSoft
Data Acquisition: High-speed simultaneous sampling system
2.2 Measurement Parameters
Test Structure: 4 compressor pipes with complex 3D geometry
Measurement Points: 16 strategically located points (4 points per pipe)
Frequency Range: 0-2000 Hz (covering compressor operating frequencies)
Spatial Resolution: 1 mm grid for vibration cloud mapping
3. Testing Methodology
3.1 Test Procedure
System Configuration:
Mount compressor assembly on vibration isolation foundation
Program automated scanning path covering all 16 measurement points
Align laser beam perpendicular to each measurement surface
Data Acquisition:
Operate compressor under typical working conditions
Simultaneously acquire vibration data from all measurement points
Record compressor speed and operating parameters for correlation
Analysis Approach:
Frequency Domain Analysis: Identify dominant resonance frequencies
Operating Deflection Shapes: Visualize vibration patterns at critical frequencies
Vibration Cloud Mapping: Generate amplitude distribution across piping system
4. Results and Analysis
4.1 Frequency Domain Analysis
Key Findings:
Primary Resonance: 125 Hz - Coinciding with compressor fundamental operating frequency
Secondary Resonances: 387 Hz and 892 Hz - Structural resonances of piping system
Harmonic Content: Multiple integer harmonics of running speed observed
Data Table - Resonance Frequencies and Amplitudes:
| Resonance Order | Frequency (Hz) | Peak Amplitude (μm) | Criticality |
|---|---|---|---|
| 1st | 125 | 15.8 | High |
| 2nd | 387 | 8.2 | Medium |
| 3rd | 892 | 12.1 | High |
4.2 Vibration Cloud Analysis
Spatial Distribution Patterns:
Maximum Vibration: Pipe #2 connection point to compressor (18.2 μm pk-pk)
Minimum Vibration: Pipe #4 far-end support location (2.1 μm pk-pk)
Node Identification: Clear vibration nodes at pipe support locations
Anti-node Locations: Maximum amplitude regions between supports
4.3 Resonance Localization
Critical Area: 75% of vibration energy concentrated in Pipe #2
Problem Identification: Inadequate support spacing causing beam-mode resonance
Secondary Issue: Pipe #3 showing torsional vibration mode at 892 Hz
5. Technical Advantages Demonstrated
5.1 Measurement Performance
Complete Visualization: Vibration cloud mapping provides instant visual identification of problem areas
High Spatial Resolution: 16-point measurement grid captures detailed vibration patterns
Accurate Resonance Detection: Clear identification of structural resonances separate from forcing frequencies
5.2 Analysis Capabilities
Rapid Problem Identification: Complete analysis within 30 minutes per operating condition
Quantitative Data: Precise amplitude measurements enable engineering calculations
Visual Presentation: Vibration cloud maps effectively communicate findings to design teams
6. Engineering Value Delivered
6.1 Immediate Improvements
Support Optimization: Redesigned pipe support locations based on node identification
Damping Application: Targeted damping treatment at high-amplitude regions
Design Modification: Pipe routing adjustments to avoid resonance conditions
6.2 Quality Impact
Vibration Reduction: 65% decrease in peak vibration levels after modifications
Noise Improvement: 8 dB reduction in radiated noise
Reliability Enhancement: Eliminated risk of fatigue failure at identified hot spots
6.3 Process Benefits
Testing Efficiency: 70% faster than traditional accelerometer-based methods
Data Completeness: Comprehensive understanding of system dynamics
Problem Solving: Direct correlation between measured data and physical modifications
7. Implementation Results
Before Modification:
Maximum vibration amplitude: 18.2 μm pk-pk
Multiple resonance frequencies within operating range
High risk of fatigue failure at specific locations
After Modification:
Maximum vibration amplitude: 6.4 μm pk-pk (65% reduction)
Resonance frequencies shifted outside operating range
Vibration energy distribution more uniform across piping system
Conclusion:
The Dynatronic VibroMicro VM-S-100 based testing system provided the compressor manufacturer with a comprehensive solution for piping vibration analysis. Through frequency domain analysis and vibration cloud mapping, the system enabled rapid identification of resonance issues and effective visualization of vibration distribution. The non-contact approach allowed for complete characterization of the piping system dynamics without mass loading effects, leading to targeted design improvements that significantly enhanced product reliability and noise performance. This case demonstrates the powerful capability of laser vibrometry in solving complex industrial vibration problems.
