1. Description of the problem and scope of application
Excessive vibration is the main sign of reduced reliability of rotary equipment (pumps, fans, motors, compressors). This manual is intended for service technicians and reliability engineers dealing with vibration problems. Timely diagnosis allows you to prevent catastrophic failures, reduce the costs of emergency repairs and increase the interval between repairs.
Field of application: industrial rotary equipment operating in modes from low to high revolutions. The criticality of the condition is assessed according to the DSTU ISO 10816 standard. Any indication of vibration exceeding zone 'B' (satisfactory) or moving into zone 'C' (unsatisfactory) according to the ISO classification, should be diagnosed immediately.
2. Safety measures
WARNING: Operating rotating equipment carries a risk of injury or death.
- Be sure to perform the Lockout/Tagout (LOTO) procedure before beginning diagnostics unless diagnostics require operating the equipment under load.
- When measuring on working equipment, use protective clothing, glasses and avoid contact with moving parts.
- Make sure there is no stored energy (pressure in the system, rotor inertia).
- Use personal protective equipment (PPE) appropriate for production conditions.
3. Necessary diagnostic tools
| Tool | Specification/Model | Range | Purpose |
|---|---|---|---|
| Vibration analyzer | FFT analyzer (2-4 channels) | 0-20 kHz | Spectral analysis, detection of malfunction frequencies |
| Stroboscope | Digital with adjustable frequency | 60-50,000 CPM | Visual phase check, speed check |
| Thermal imager | High resolution | -20...+500°C | Detection of local heating of bearings |
| Multimeter | True RMS | AC/DC V, A, Ohm | Engine power check |
| Clock type indicator | Magnetic stand, accuracy 0.01 mm | 0-10 mm | Axial/radial backlash measurement, centering check |
4. Initial assessment checklist
| Parameter | What to check | Priority |
|---|---|---|
| Appearance | The presence of weakened fasteners, foundation cracks | Tall |
| Working mode | Compliance of the load with passport data | Average |
| Changes | Have any repairs or parts been replaced recently? | Tall |
| History | When was the last time the bearings were lubricated? Analysis of vibration trends | Tall |
| noise | The nature of the sound (hum, howl, knock) | Average |
5. Systematic diagnostic algorithm (Decision tree)
- Step 1: Spectrum Data Acquisition (FFT)
- A) Dominant 1x RPM:
- Probable Cause: Imbalance.
- Action: Check the presence of dirt on the blades, the absence of balancing weights.
- B) Dominant frequency of 2x revolutions (RPM):
- Probable cause: Misalignment (of shafts or coupling).
- Action: Carry out laser alignment, check the rigidity of the foundation.
- B) High-frequency harmonics (non-synchronous):
- Probable cause: Rolling bearing defect.
- Action: Check the temperature, conduct an envelope analysis (Envelope analysis).
- D) High vibration when passing through a certain speed (resonance):
- Probable cause: Coincidence of own frequency with working frequency.
- Action: Carry out a coast down test, a bump test.
- A) Dominant 1x RPM:
6. Matrix "Symptom - Probable cause"
| Symptom (spectrum) | Probable causes (rank) | Diagnostic test | Expected result |
|---|---|---|---|
| High 1x RPM | 1. Imbalance; 2. Bending of the shaft | Phase measurement | Stable phase for imbalance |
| High 2x RPM | 1. Decentralization; 2. Loose coupling | Laser centering | Improvement after correction |
| High frequency bursts | 1. Bearing wear; 2. Lack of lubrication | Spectrum analysis (BPFO/BPFI) | Detection of characteristic frequencies |
| "Bouquet" spectrum (many peaks) | 1. Backlash; 2. Weakening of the foundation | Visual inspection of fasteners | Detection of weakened anchors |
7. Analysis of the main reasons
Imbalance
It occurs when the mass of the rotor is unevenly distributed relative to the axis of rotation. Accumulation of sediments, blade erosion, loss of balancing loads can be the reasons. If not eliminated, this leads to significant dynamic loads on the bearings and premature failure of the foundation.
Decentralization
Misalignment of engine and equipment shafts. Causes stress in couplings and bearings, resulting in heating and accelerated wear. Manifested by a high level of vibration at 2x RPM.
Bearing defects
Wear of raceways or rolling elements due to metal fatigue, contamination or lack of lubrication. If a defect is confirmed, the bearing must be replaced immediately, as its destruction can jam the shaft.
Resonance
Occurs when the excitation frequency coincides with the natural frequency of the system (foundation, body, rotor). This leads to a significant amplification of the vibration amplitude. Requires a change in the stiffness of the system or its mass.
8. Step-by-step elimination procedures
- Elimination of imbalance: Clean the rotor. Perform dynamic balancing at the installation locations (in-situ) or on the machine. Check the mass of cargo.
- Misalignment correction: Use a laser system to measure and correct the position of the motor relative to the pump. The values must be within the tolerances for the coupling types (rigid/flexible).
- Replacement of bearings: Ensure cleanliness of the workplace. Use induction heaters for installation (prevent local overheating). Use only lubricants recommended by the manufacturer.
- Combating resonance: Changing the stiffness of the frame (welding reinforcements) or installing additional supports. Change in operating speed (if VFD is used).
9. Preventive measures
| The reason | Strategy | Monitoring method | Interval |
|---|---|---|---|
| Imbalance | Periodic cleaning | FFT spectrum (1x) | Every 3 months |
| Decentralization | Regular inspection | Laser centering | Annually |
| Bearing wear | Proper lubrication | Vibration analysis/ultrasound | Every month |
10. Spare parts and components
To ensure trouble-free operation, use only certified components.
| Description | Specification | When to replace | Category UNITEC |
|---|---|---|---|
| Bearings | SKF/FAG (ISO standard) | When noise or peaks appear on the BPFO/BPFI frequencies | Bearings |
| Couplings | Elastic/Hard | With visual signs of cracks or deformations | Couplings |
| Anchor bolts | Strength class 8.8+ | After stretching or corrosion | Fastening |
Order the necessary spare parts on the official portal: https://www.unitecd.com/e-catalog/
11. Links
- DSTU ISO 10816-3: Mechanical vibration. Evaluation of machine vibration.
- OEM instructions for applicable equipment.
- UNITEC Pump and Motor Maintenance Manual.
