The use of down-the-hole drilling rigs in grouting operations is more and more extensive, and grouting reinforcement is mostly open-air operation. This paper mainly discusses how to choose the model of crawler type down-the-hole drilling rig.
1, selection principle
(1) Applicable in production
The purchased drilling rig should meet the engineering construction needs, and should be properly configured according to the construction tasks undertaken under the normal conditions of the enterprise, fully consider the scope of application of the drilling rig, not only to meet the current construction needs, but also to take into account the future drilling rigs under other production conditions. The demand, only the production of highly rigable rigs can better show its investment results.
(2) Technically advanced
While meeting the production needs, it is required to maintain its advanced performance, which is conducive to extending its technical life. The small meeting will be eliminated in the short term. In the long run, it is in line with the sustainable development requirements of enterprises and can effectively protect investment.
(3) operability and maintainability
The operation is simple, and it is convenient for workers to master the operation skills and shorten the auxiliary operation time, such as the leveling of the site, the displacement of the rig, the lifting and lowering of the rig, the replacement of the drill pipe, and the adjustment of the valve for gas and water.
The structure of the rig is simple and easy to repair, the versatility of the parts is strong, and the supply of goods is sufficient to reduce the purchase price of the parts, equipment operation and management costs. Drilling machine maintenance is difficult, technical support and after-sales service are guaranteed. In the event of mechanical failure, on-site maintenance workers can repair in time, avoiding delays in construction and production due to waiting for technical rescue by manufacturers.
(4) Safety and environmental performance
At present, the state attaches great importance to the safety and environmental performance of products. When purchasing new equipment, it is necessary to pay attention to whether the manufacturing materials, various safety devices are complete, construction noise, exhaust gas and waste discharge meet the relevant national laws and regulations.
(5) Economically reasonable
The equipment purchase price is reasonable, the energy consumption and maintenance cost are low during the use process, and the investment recovery period is short, which is beneficial to the capital flow of the enterprise.
2. Selection of technical parameters of drilling rig
The grouting operation is mainly carried out by the downhole drilling rig in the required reinforcement depth of the subgrade, and the diameter is drilled. After the drilling is completed, the cement slurry is injected into the soil layer by the hollow drill pipe of the drilling machine through the grouting pump. The voids or pores of the body are filled with slurry and solidified. The air compressor supplies compressed air to the rig impactor, which drives the impactor piston to reciprocate, completes the impact drilling, and blows out the drilling slag. Therefore, while comparing the technical parameters of the downhole drilling rig, it is necessary to take into account the technical indicators and economics of the supporting air compressor.
(1) Work surface hardness
Different rocks have different hardness indexes and different drillability. Ruggedness is often used to indicate how easily the rock is broken. The size of the sturdiness is expressed by the firmness factor, which is also called the hardness coefficient, also known as the Platts hardness factor f value.
In the construction of the project, it is necessary to select a down-the-hole drilling rig that adapts to the hardness of the small working face according to the construction geological conditions, and select the drill bit, drill pipe and impactor of the same form to suit it. The hardness of the rock is the key to the efficiency of the drilling rig. The small downhole drilling rig is most suitable for the rock below the medium and hard.
(2) Drilling diameter and depth
According to the requirements of the diameter, depth and drilling angle of the grouting hole, it is necessary to equip the drill bit and drill pipe with the same diameter and length to meet the technical requirements of the drilling. At the same time, the drilling arm and the guide rail of the drilling machine should have various adjustable The angle to meet the construction needs.
A crawler DTH drill can be used with a variety of drills of various diameters and can be flexibly selected according to the requirements of the construction aperture. The drilling depth is adjusted by using a drill pipe with a small number of joints. The length of the drill pipe is generally 2~9m, and the drill pipe is connected by male and female threads. The outer diameter of the drill pipe affects the drilling efficiency. According to the fluid dynamics theory, the slag can be smoothly discharged outside the hole only when the airflow velocity in the annular passage formed by the drill pipe and the hole wall is greater than the suspension velocity of the rock slag. The velocity of the airflow is mainly determined by the cross-sectional area and length of the channel. The smaller the cross-sectional area of ​​the channel, the higher the flow rate; the longer the channel, the lower the flow rate. Therefore, the larger the diameter of the drill pipe, the higher the airflow speed and the better the slagging effect. Of course, it is also small enough that the dregs are difficult to pass, and the ring width of the ring-like section is preferably 10 - 25 mm. This can be used as a basis for investigating whether the drill pipe is drilled, the drill bit is matched, and the work efficiency is roughly estimated.
(3) Rig rotation speed, torque, propulsion shaft pressure
The parameters such as the slewing speed, the slewing torque and the propulsion shaft pressure of the rig directly match the drilling speed and the drilling cost. Choosing the right swing speed is great for reducing machine vibration, increasing bit life and speeding up the drilling. The rotation speed is determined according to the diameter of the drill hole, the structure of the drill bit, the frequency of the impactor and the nature of the rock. The recommended value of the rotation speed is: when the drill diameter D is 100 mm, the rotation speed n should be 30~40 r/min; when D=150 mm, n is 15~30 r/min; when D=200 mm, n should be 10~20 r/min; when D=250 mm, n should be 8~15 r/min.
The slewing torque is mainly used to overcome the frictional resistance of the drill bit and the bottom of the hole, the shear resistance, and the frictional resistance of the drill and the hole wall during normal drilling. The resistance torque of the drill is proportional to the diameter of the borehole and the depth of the hole. The torque required for normal drilling is small, and the drilling resistance of the hole diameter below 150 mm is generally about 1000 N·m. Usually, the torque of the rig itself is much larger than this value. The larger the torque, the easier it is to remove the drill pipe, the stronger the resistance of the drill, and the deeper the depth of drilling. When drilling and large-aperture deep hole drilling in the fracture zone with relatively developed joints, it is necessary to select a rig with a relatively large torque.
The small axial pressure of the propulsion only affects the life of the drill bit, and more importantly, directly affects the drilling speed. If the propulsion shaft pressure is too large, the drilling tool will rotate small and continuous, causing rotary impact, and at the same time, the drill cuttings at the bottom of the hole will be excessively broken, resulting in waste of energy, affecting the drilling speed, and at the same time accelerating the wear of the drill bit; The rebound is intensified, and the drill bit can be close to the bottom of the hole, so that the impact energy can be effectively applied to the rock at the bottom of the hole, which affects the drilling efficiency and accelerates the damage of the drilling machine and the drilling tool.
Recommended value for propulsion shaft pressure at small bit diameter: when drill diameter
When D = 100 mm, the optimal axial thrust F is 4 000~6000 N; when D=150 mm, F should be 6 000~10 000 N; when D = 200 mm, F should be 10 000~14000 N When D = 250 mm, F should be 14 000~18 000 N.
Understand the influence of the above parameters on the drilling work of the down-the-hole drilling rig and the best matching method. When selecting the rig of the same type, the relevant technical parameters can be compared and demonstrated to judge whether it meets the principle of best matching.
(4) Working pressure and gas consumption
The down-the-hole drilling rig is supplied with compressed air from the air compressor and sent to the impactor through the oil mister. The impactor is powered by the impactor, the piston in the impactor is reciprocated, the drill bit is drilled, and the drill residue is drilled from the other side. Blow out in the hole and empty the hole for the grouting of the next step. The working pressure of the rig is the air pressure when the rig is normally drilled, and the unit is M Pa. The air consumption is the amount of compressed air required to clear the hole.
The small energy simply says that the higher the working pressure, the faster the impact drilling speed, the higher the working pressure can be, the faster the hole forming speed is selected, the empirical value of the drilling wind pressure and the hole forming speed: The wind pressure is 0. 90.98, 1.05, 1.05~1. 121. 12~1. 19 M Pa, the hole forming speed is 11.16, 13.4, 14, 15.3 m/h.
According to the actual work efficiency requirements of the project, the drilling machine with the appropriate working pressure is selected. The small energy pressure is too low, resulting in low efficiency of the drilling machine and too high pressure to meet the required working efficiency. The choice of working pressure of the drilling rig affects the pressure matching of the air compressor at the same time. The higher hole forming speed means that the high-power air compressor needs to be matched with it, and the excessively high hole-forming speed will cause waste of funds.
3. Investment recovery of equipment
Tracked downhole drilling rigs must also consider economic factors such as equipment investment, revenue, depreciation, and maintenance at the time of purchase. The following methods can be used for evaluation.
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