Reasons and Solutions for the Failure of the DTH Hammer

Table of Contents

As an important rock drilling tool, the DTH hammer plays an important role in the mining industry, and its rapid development and wide application make it very popular in the market. Unlike rock drills, the DTH hammer cannot be used alone. It is an important part of DTH drilling rigs, mainly used to provide axial reciprocating rock crushing impact to the drill bit, to cool the drill bit, and to carry cuttings. Although it has stable performance, a simple and reliable internal structure, and easy assembly and disassembly, with the increase in service time and changes in working conditions, the DTH hammer will also face various failure problems. Understanding the cause of the DTH hammer failures can help maintenance personnel solve the problem and improve the work efficiency and safety of the DTH hammer.

DTH hammer

In general, there are many reasons for the failure of the DTH hammer, the main manifestations are the non-impact of the DTH hammer, weak impact, intermittent impact, etc. The specific performance is the following five points.

Processing defects

The match between the piston and the cylinder liner of the DTH hammer is relatively tight, the matching length is long, and the machining accuracy and surface smoothness are required to be high, which has very high requirements for the cylindricity of the piston and the cylinder liner. If the cylindricity is not guaranteed, the piston will be stuck in a direction or intermittently, and the drill pipe may eventually have to be lifted and unloaded frequently for DTH hammer maintenance.

In addition, the rigidity of the outer casing of the DTH hammer is also an important factor restricting the service life. If its rigidity is poor, the DTH hammer will deform due to frequent collision with the borehole wall during drilling. When the DTH hammer is not working, we need to vibrate, disassemble, and clean it, which will aggravate the deformation of the outer casing of the DTH hammer. The deformation of the outer casing will cause the internal parts to be stuck, making it impossible to disassemble. Finally, the DTH hammer scraps.

The drill bit is stuck

The drill bit and the DTH hammer are splines matched, the fitting clearance is relatively large, and the spline tail of the drill bit of many types of DTH hammer can expose the matching spline sleeve. If the cuttings are wet, it is easy to form bit balling and stick it to the drill bit. If this condition is not improved in time, the bit balling will enter the spline fitting gap, affecting the effective transmission of the impact power of the DTH hammer piston. What’s worse, the drill bit and the spline sleeve may be stuck together.

Insufficient or no lubrication leads to premature wear or damage

If the lubricating oil cannot reach the impact structure of the DTH hammer, it will cause premature wear. We can check the lubrication device, inject oil from the top of the DTH hammer or increase the oil content of the compressed air to solve the problem.

The impact structure does not work or is not normal

Four reasons lead to this kind of failure in the DTH hammer.

A. The gas channel is blocked.

B. The gap between the piston and the inner and outer cylinders is too large, so is the gap between the piston and the air distributor.

C. The DTH hammer is blocked by dirt.

D. The piston or the tailpipe of drill bit is broken.

We can also use the following four methods to troubleshoot the fault.

A. Check the air pressure to make sure the air passage is clear.

B. Disassemble the DTH hammer, check the wear condition, and replace the worn parts.

C. Disassemble the DTH hammer and clean all the internal parts.

D. Disassemble the DTH hammer and replace pistons or drill bits.

The drill bit comes off

When the DTH hammer is working without right-handed rotation, it can cause the drill bit to fall off. We can hook the detached part and ensure the right-handed rotation during drilling and lifting to resolve such failures.

In addition to the above failure causes, we may encounter new failures during use. Understanding and analyzing the failure causes of the DTH hammer will not only help prolong the service life of the equipment but also help improve the structure and process of the DTH hammer. Of course, the occurrence of failures is not the result we want to see, but to reduce the failures of the DTH hammer, we also need to maintain them in daily use. In addition, we also list 8 points for your reference.

1. Because the joints of the DTH hammer are all right-handed threads, it should always be right-rotated during drilling.

2. At the beginning of drilling a hole, use the minimum impact and propulsion force to make the drill bit enter the rock smoothly.

3. It is important to match the propulsion force with the weight of the drilling tools. The thrust must change with the weight of the drilling tools.

4. The rotary speed of the DTH hammer is generally 15-80rpm. The rotation speed should be determined according to the diameter of the drill bit and the conditions of the rock formation. Under the same conditions, the larger the diameter of the drill bit and the harder the rock, the lower the rotation speed.

5. Because blockages and cavities may lead to stuck drills, it is necessary to regularly use a DTH hammer to blow and clean the bottom of the hole.

6. The proper lubrication of the DTH hammer can never be ignored. Otherwise, it will accelerate the wear of the DTH hammer and even cause damage.

7. During the rod connection process, rock ballast, and various impurities will fall into the DTH hammer, so the threaded end of the loosened drill pipe must be covered to ensure that the drill pipe does not stick to rock ballast and dust.

8. At the end of each work, check the machine and deal with any problems immediately.

This is all about the failure reasons and daily maintenance of the DTH hammer. Only by operating by the relevant precautions of the equipment and dealing with it in time can we ensure better use of the DTH hammer and prolong its service life, which can also help enterprises reduce costs and improve operational efficiency.

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