Precautions for Using DTH Hammers

Proper operation and maintenance are critical to equipment life, drilling efficiency, and safety during DTH hammer use. The following precautions are divided into three parts: preparation, operation, and maintenance.

I. Preparation Before Use

1. Check air supply: the compressor pressure should reach the hammer’s specified working pressure (generally 10–25 bar). Air volume must be sufficient; otherwise, impact force will be inadequate and cuttings removal poor. Compressed air must be dry, clean, and oil‑free. An oil‑mist lubricator may be installed.

2. Check drilling tool compatibility: the DTH hammer, bit, drill rods, joints, slips, hoisting equipment, etc., must be correctly matched in model and size. The bit should slide freely into the hammer body without jamming or excessive looseness.

3. Add lubricating oil: use special DTH hammer oil (not ordinary engine oil). Check the oil level every shift (or every 4 hours of continuous operation) to maintain adequate lubrication.

4. Inspect seals and O‑rings: ensure there is no aging, cracking, or deformation. During assembly, take care to prevent O‑rings from being pinched or flattened.

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II. Operation Precautions

1. Starting the hole: at the beginning of drilling, apply low pressure and slow rotation to stabilise the bit position. After confirming that the bit is centred, gradually increase pressure to the normal working level.

2. Normal drilling: maintain a proper match among weight on bit (WOB), air pressure, and rotational speed (generally: high air pressure + appropriate WOB + medium rotation speed). Avoid excessive WOB, which may cause hammer sticking, rod breakage, or insert loss. Also avoid insufficient WOB, which may cause bouncing and uneven wear.

3. Ensure smooth cuttings removal: if poor removal or weak return air is observed, stop immediately and check. This is usually caused by insufficient air pressure, water accumulation in the hole, dust blockage, or excessive bit wear.

4. Prevent water from entering the hammer body: if substantial groundwater is encountered during drilling, dewater the hole before continuing. Water ingress may cause piston rusting, sluggish action, or seizure.

5. Watch for hole deviation and collapse: in inclined holes or fractured zones, reduce WOB and decrease rotational speed. In case of collapse, promptly lift the drilling assembly to clear the hole bottom.

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III. Shutdown and Maintenance

1. Release residual air after shutdown: before turning off the compressor, stop the air supply and empty any remaining air in the lines. This avoids the danger of residual pressure inside the hammer when disassembling.

2. Cleaning and lubrication: after removing the hammer body, clean internal parts to remove mud and dust. Apply rust‑preventive oil, especially on the piston, inner cylinder, and valve components.

3. Regular inspection of wear parts: the bit, outer and inner sleeves, piston, valve plates, etc., are consumable items and should be replaced periodically. Also check joint threads for wear and cracks.

4. Long‑term storage maintenance: before storage, add lubricating oil and seal‑pack to prevent corrosion. Store in a dry, ventilated environment.

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Summary

Ensure clean and sufficient air supply, proper lubrication, matched WOB and air pressure, smooth cuttings removal, and regular maintenance – these are the keys to reliable DTH hammer performance and longevity.