Why does the flexible coupling of the air compressor gear break down?
1. Tooth surface wear (most common)
Symptom: Tooth thickness decreases, tooth surface roughness increases, and in severe cases, step-like wear occurs.
Reasons:
Insufficient lubrication: Insufficient lubricating oil quantity or aged oil, resulting in direct contact and friction between the tooth surfaces.
Impurities intrusion: Failure of sealing, dust and metal particles enter between the teeth, intensifying abrasive wear.
Excessive load: Actual torque exceeds the rated value of the coupling, causing excessive contact stress on the tooth surfaces.
Offset exceeding standard: Misalignment of the two shafts (axial / radial / angular) causes uneven loading on the tooth surfaces, leading to intensified local wear.
2. Tooth surface adhesion
Symptom: Metal on the tooth surface melts and welds due to high temperature, forming grooves.
Reasons:
High speed and heavy load: Friction on the tooth surfaces generates heat at high rotational speeds, causing the oil film to rupture.
Lubrication failure: Insufficient lubricating oil viscosity or poor anti-adhesion performance.
Material mismatch: The hardness difference between the inner and outer teeth is too small (ideal difference is HRC 5 - 10).
3. Bolt fracture
Symptom: Connecting bolts (especially countersunk hole bolts) experience fatigue fractures.
Reasons:
Insufficient pre-tightening force: Failure to tighten according to the specified torque during installation, causing the bolts to be subjected to alternating loads.
Failure to handle loosening in time: Equipment vibration leads to bolt loosening, intensifying stress concentration.
Material defect: Insufficient strength of the bolts or presence of cracks and other defects.
4. Aging and leakage of sealing rings
Symptom: Lubricating oil leaks, visible oil stains on the outside of the coupling.
Reasons:
High temperature: Long-term operation in high-temperature environment, rubber sealing rings age and harden.
Chemical corrosion: Corrosion of the sealing rings by lubricating oil additives or environmental media (such as acidic gases).
Improper installation: The sealing rings are scratched or distorted during installation.
5. Fatigue cracks
Symptom: Cracks appear on the semi-coupling or intermediate sleeve, commonly at the tooth root or keyway.
Reasons:
Frequent start-stop: Frequent start-stop of the equipment generates impact loads.
Resonance: The natural frequency of the coupling is close to the vibration frequency of the equipment, causing resonance.
Material defect: There are air holes, slag inclusions, etc. in the casting, becoming the source of cracks.
II. Case Analysis
Case 1: Excessive tooth surface wear
Background: After one year of operation, the tooth thickness of the coupling of a chemical plant increased by 20% (normal ≤ 10%).
Reasons:
Incorrect selection of lubricating oil (too low viscosity grade), unable to form an effective oil film.
No dust removal device installed at the air intake, dust entered the coupling interior.
Case 2: Breakage of bolts causing machine shutdown
Background: The bolts of the coupling of an air compressor in a certain mine broke consecutively 3 times, resulting in a loss of approximately 50,000 yuan each time due to the shutdown.
Reasons:
During installation, a torque wrench was not used, and the pre-tightening force was insufficient (only reaching 60% of the specified value).
Regular checks on the loosening of the bolts were not conducted, leading to fatigue breakage.
Case 3: Sealing ring aging and oil leakage
Background: The air compressor coupling of a certain dyeing factory was replenished with lubricating oil every week, but still frequently triggered oil shortage alarms.
Reason:
The equipment has been operating in an environment of 80℃ for a long time, and the nitrile rubber sealing ring has aged and cracked.
The lubricating oil contains extreme pressure additives, which accelerate the corrosion of the rubber.
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