Abnormal noise in screw air compressor units not only reduces operational efficiency but also serves as a critical warning sign of potential mechanical failure. For maintenance personnel, quickly identifying the source of noise and implementing targeted solutions is essential to minimizing downtime. This article systematically outlines common noise phenomena, root causes, and actionable troubleshooting steps to help users "diagnose issues through sound analysis."

 

Common Noise Phenomena and Risks

Abnormal noise in screw compressors typically manifests as excessive vibration and unusual sounds, including:

1. Metallic Clashing: Intermittent or continuous metal-on-metal impacts, often caused by loose or colliding components.
2. Rhythmic Knocking: Regular tapping sounds, usually linked to bearing wear or rotor imbalance.
3. Friction-Induced Squealing: High-pitched screeching from belt slippage or abnormal airflow.
4. Airflow Whistling: Sustained high-frequency noise in specific pressure ranges, often related to valve or pipeline resistance.

Consequences of Ignoring Noise: Accelerated component wear, rotor seizure, bearing failure, or even catastrophic unit damage.

 

Root Cause Analysis and Localization

 

1. Belt Drive System Issues (Belt-Driven Units)

Symptoms: High-frequency squealing with belt vibration.
Causes:
Loose or aged belts causing slippage.
Mismatched pulley groove types (e.g., SPA vs. SPB) leading to abnormal wear.
Diagnosis:
Check belt tension by pressing the midpoint (deflection should be <10–15 mm).
Verify pulley groove markings for consistency.

 

2. Loose Mechanical Components

Symptoms: Irregular metallic clanging, worsening under load.
Causes:
Loose foundation bolts or coupling fasteners.
Failed internal component fixation (e.g., gears, counterweights).
Diagnosis:
Retighten all visible fasteners with a torque wrench.
Isolate noise sources and inspect internal connections.

 

3. Bearing Failure

Symptoms: Rhythmic knocking, elevated operating temperatures, current fluctuations.
Causes:
Metal fatigue from inadequate lubrication.
Bearing fracture due to chronic overload or axial force imbalance.
Critical Warning: If noise coincides with rotor resistance, shut down immediately to prevent seizure!

 

4. Airflow Whistling (Valve/Pipeline Issues)

Symptoms: Sustained whistling in specific pressure ranges (e.g., 0.5–0.7 MPa).
Causes:
Restricted airflow from undersized intake valves or damaged valve plates.
Resonance due to failed springs in minimum pressure valves.
Diagnosis:
Note pressure points where noise occurs.
Use a stethoscope to trace noise to valves or flanges.

 

Troubleshooting Workflow and Best Practices

 

Step 1: Identify the Noise Type

Action: Document noise characteristics (frequency, consistency, load correlation) to distinguish mechanical vs. airflow issues.
Tool: Use a mechanical stethoscope or screwdriver pressed against the ear to localize sources.

 

Step 2: Address External Adjustable Factors

Belt Adjustment:
Tension belts to proper deflection or replace worn belts.
Replace mismatched pulleys (e.g., SPZ→SPA requires full pulley set replacement).
Fastener Retightening:
Re-torque foundation bolts and coupling screws per manufacturer specifications.

 

Step 3: Diagnose Internal Mechanical Faults

Bearing Inspection:
Remove the end cover and manually rotate the rotor to check for resistance.
Inspect bearings for pitting, spalling, or cage deformation.
Solution: Replace bearings, recalibrate rotor alignment, and flush oil passages.

Valve Maintenance:
Disassemble intake and minimum pressure valves to inspect plates and springs.
Solution: Reseal valve seats or replace valve assemblies.

 

Step 4: Post-Repair Validation

Run the unit unloaded for 10 minutes to monitor noise and vibration.
Gradually increase load to rated pressure to confirm noise elimination.

 

Preventive Maintenance Recommendations

 

1. Routine Checks:

Weekly belt tension and wear inspections.
Monthly infrared thermography of bearings (normal ≤80°C).
 

2. Lubrication Management:

Replace synthetic grease regularly (every 4,000–6,000 hours) to prevent carbonization.
 

3. Vibration Analysis:

Quarterly vibration spectrum analysis to detect early bearing degradation.

 

Conclusion

Abnormal noise in screw compressors is a vital "health alert." By correlating acoustic patterns with operational data and following a systematic approach—from external to internal, simple to complex—users can minimize misdiagnosis and repair costs. Remember: Bearing-related noise is a red alert demanding immediate shutdown to avert catastrophic failure!

Note: This guide applies to general screw compressor models. Always refer to the manufacturer’s manual for model-specific protocols.