Causes of Abnormal Breakage of Rock Drill Shanks

The rock drill shank is a critical component of hydraulic rock drills, responsible for transmitting rotational and impact energy. During operation, it endures complex loads delivered by the impact piston and rotary motor of the rock drill. A typical failure mode of rock drill shanks is abnormal breakage, often occurring within a working period of fewer than ten shifts. The fracture generally occurs at the thread root or along the thread itself.

Failure Analysis of Abnormal Rock Drill Shank Breakage

Loose Connections

Impact forces generated during the operation of the rock drill can loosen the bolts connecting the rock drill to the mounting plate, causing the rock drill to wobble during operation.

Excessive Wear in the Drill Shank Guide Sleeve

Failure to replace the guide sleeve after its inner bore exceeds the wear limit results in an excessive gap between the rock drill and the guide sleeve, leading to wobbling of the front end of the rock drill shank during operation.

Insufficient Lubrication

Inadequate lubrication during drilling prevents the rock drill shank from being effectively lubricated and cooled, resulting in excessive heat, reduced strength, and ultimately failure.

Mismatch Between Feed Pressure and Impact Pressure

An imbalance between feed pressure and impact pressure can cause the rock drill to produce "dry strikes," subjecting the rock drill shank to unnecessary and excessive impact loads.

Incorrect Installation of the Rock Drill

Improper installation of the rock drill on the feed beam can misalign the rock drill shank's centerline with the axes of the front and intermediate shank holders, resulting in additional radial forces on the rock drill shank.

Preventive Measures for Abnormal Rock Drill Shank Breakage

Lubrication Check Before Each Shift

Before starting the machine, check the lubrication spray at the machine head. Observe the oil film on the rock drill shank to ensure it is even and meets lubrication requirements before drilling operations commence.

Regular Inspection of Bolts and Alignment

Inspect the connection between the rock drill mounting bolts and the mounting seat every 40 impact-hours of operation. Ensure normal bolt torque, alignment of the rock drill shank's center with the axes of the front and intermediate shank holders, and an idle feed pressure of less than 3 MPa.

Adjust Feed Pressure Based on Rock Conditions

During drilling, adjust the feed pressure in response to rock conditions. Decrease the feed pressure for hard rock and increase it for soft rock to avoid "dry strikes."

Routine Replacement of the Guide Sleeve

Regularly inspect the inner diameter of the rock drill shank guide sleeve and replace it every 800 impact-hours of operation. This prevents wobbling caused by excessive wear in the guide sleeve's bore.

By adhering to these preventive measures and conducting regular maintenance, abnormal breakage of rock drill shanks can be minimized, improving both the efficiency and longevity of hydraulic rock drills.