The DTH hammer is a commonly used equipment in drilling engineering. It consists of many parts, the core of which is the piston. Its role is pivotal in the overall functioning of the DTH hammer, subject to intricate and alternating stresses during operation. The service life of the piston holds direct significance as it profoundly impacts the progress and cost of a project utilizing DTH drilling. With the wide application of DTH hammers, people have higher and higher requirements for them. Improving the service life of DTH hammer pistons has become an essential issue in drilling engineering.
Piston load analysis
When the piston of the DTH hammer is working, the piston hits the drill bit at a high speed and frequency. The energy of the piston is transmitted to the rock through the drill bit and carbide button in the form of stress waves. The magnitude and direction of the force exerted on the piston are periodic. The stress changes suddenly from zero to nearly 0.1MPa in about 100μs and then drops to zero after several hundred microseconds. It is under the action of this stress wave that the piston undergoes fatigue fracture.
Factors affecting piston service life
Material quality
The material quality of the piston has a significant impact on the service life. High-quality materials are resistant to abrasion, wear, and corrosion, thus extending the life of the piston.
Structural design
The structural design of the piston also has a significant impact on its service life. Reasonable structural design can reduce the impact effectively and protect the piston from damage. Unreasonable design will cause uneven force on the piston and easily cause fatigue cracks.
Manufacturing process
The manufacturing process of the piston also has a vital impact on its service life. Precision manufacturing technology can ensure the dimensional accuracy and surface quality of the piston, thereby extending its service life. If the quality or accuracy of the piston during manufacturing does not meet the requirements, it may cause cracks and other problems on the surface, and cracks are the root cause of fracture and failure of the parts.
Usage environment
The working environment of DTH hammers is often harsh, such as high temperature, high pressure, and corrosion. These factors will accelerate the aging and wear of the piston.
Methods to improve the piston service life
Choose a reasonable structural shape
By optimizing the structure of the piston, we can significantly enhance its durability. For example, the design uses a reasonable piston structural shape to match the drill bit to reduce the peak stress wave.
Choose reasonable materials
Selecting high-quality materials is the basis for improving piston life. Considering the operational principles of the DTH hammer and the specific features of the piston’s function, the piston surface should have high hardness and wear resistance, the heart should have enough strength and toughness, and the ideal organizational structure is the so-called thin shell structure. Hammer pistons predominantly utilize steel materials, with carburizing steel and high-carbon tool steel being the primary choices.
Selection of appropriate heat treatment process
Using advanced heat treatment technology can ensure the manufacturing quality of the piston, thereby increasing its service life. The so-called “thin shell structure” should be obtained after heat treatment of the piston. It has a thin shell with a high hardness on the surface to improve wear resistance, and the core must have appropriate hardness to ensure sufficient strength and toughness. After quenching, the surface hardened layer generally has a compressive stress of 400~700MPa, so It can improve the fatigue strength mainly based on tensile stress. In addition, it should also make the structure uniform and prevent surface oxidation and decarburization.
Improve cold processing quality
Piston failure is mainly due to fatigue fracture, so there are strict requirements for the piston structure and surface finish. It is necessary to avoid sudden changes in the cross-section, reduce stress concentration, and adopt arc transitions to improve surface finish and prevent knife marks, chips, and scratches.
Regular maintenance
Regularly inspect and maintain the DTH hammer to detect and deal with problems in time to extend the service life of the piston. It includes changing lubricants, cleaning DTH hammers, checking piston wear, etc.
Operating instructions
Ensure that the operator follows the operating procedures to avoid damage to the piston due to improper operation. For example, ensure that the hammer is fully lubricated before starting it, and allow the DTH hammer to cool down completely before cleaning and maintenance after shutdown.
Improving the piston life of the DTH hammer is of great significance to drilling engineering. From material selection to structural design, from the manufacturing process to the usage environment, every aspect affects the service life of the piston. Therefore, we need to take comprehensive measures to improve piston service life. These measures can effectively improve the service life and working efficiency of the DTH hammer piston, reduce the cost and risk of the project, and provide strong support for the development of rock drilling projects.
