Frequent breakage of hammer bolts can stem from several issues, including improper installation, excessive vibration, material fatigue, or bolt quality. Understanding these causes is crucial for preventing future failures and ensuring the longevity of your equipment.
● Improper installation
Causes: Failure to tighten to the standard torque: Insufficient torque can loosen bolts, while excessive torque can lead to stress concentration. Bolts are not tightened symmetrically and in stages: Uneven force on one side causes shear forces. Failure to use thread sealant or lock washers: Loosening is likely to occur under vibration.
Typical manifestations: Fatigue marks appear on the fracture surface, and the bolt threads are partially worn.
● Workmanship Defects
Causes: Using non-standard bolts (e.g., ordinary carbon steel instead of alloy steel). Improper heat treatment leading to uneven hardness (too brittle or too soft). Inadequate thread machining precision, resulting in burrs or cracks.
Typical manifestations: Fracture at the thread root or bolt neck, with a rough cross-section.
● High vibration and impact loads
Cause: The hammer’s operating frequency is close to the equipment’s resonant frequency, causing high-frequency vibration. Excessive wear or incorrect drill rod selection results in abnormal transmission of impact force to the bolt.
Typical symptoms: Bolt breakage accompanied by severe equipment vibration or unusual noise.
● Improper structural design
Cause: The bolt specifications do not match the mounting holes (e.g., too small a diameter, insufficient length). Insufficient bolt quantity or improper placement of bolts.
Typical symptoms: Repeated bolt breakage at the same location, causing deformation of surrounding components.
● Corrosion and Fatigue
Cause: Rust caused by long-term exposure to water and acidic mud. Failure to regularly replace bolts leads to accumulation of metal fatigue.
Typical symptoms: Rust on the bolt surface and shell-like fatigue marks on the cross-section.
Solution
● Standardized Installation Procedures:
1. Use a torque wrench to tighten symmetrically in steps according to the manufacturer’s specifications.
2. Apply thread locker and install spring washers or serrated washers.
3. Mark bolt positions after installation to facilitate daily inspection for looseness.
● Recommended Selection of High-Grade Bolts:
Use 12.9-grade alloy steel bolts (tensile strength ≥ 1200 MPa).
● Optimized Vibration Reduction Measures:
1. Install rubber damping pads or copper buffer washers at bolted joints.
2. Check drill rod wear; if wear exceeds 10% of diameter, replace immediately.
3.Adjust the hammer’s operating frequency to avoid the equipment’s resonance range.
● Standardized Operation and Maintenance Measures:
1. Do not tilt the drill rod more than 15° during operation to avoid lateral forces.
2. Stop the machine for cooling every 4 hours of operation to prevent overheating and weakening of the bolts.
3. Check bolt torque every 50 hours of operation and re-tighten according to standards if loose.
● Regular Replacement and Corrosion Prevention Recommendations:
1. Bolts must be replaced after more than 2000 operating hours (even if not broken).
2. After operation, rinse the bolt area and apply grease to prevent rust.
3. Use stainless steel bolts in corrosive environments.
If you have any technical questions about your hydraulic breaker, please feel free to contact HMB excavator attachment. We will be happy to answer your questions.
HMB excavator attachment whatsapp:+8613255531097
Post time: Aug-12-2025
