DTH Drilling Rig Working Principle And Usage Rules

Working principle of DTH Drilling Rig

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JK520 Crawler Mounted Hydraulic DTH Drilling Rig

DTH drilling rig is a percussive rotary drilling rig. Its internal structure is different from general rock drilling rigs. Its gas distribution and piston reciprocating mechanism are independent. The front end is directly connected to the drill bit and the back end is connected to the drill rod. When rock drilling, the impactor dives into the hole, and the piston (hammer) in the impactor reciprocates to strike the shank through the gas distribution device (valve) so that the drill bit impacts the rock at the bottom of the hole. The high-speed rotation of the impactor in the hole is realized by a motor or a wind-driven rotating device outside the hole through a drill rod connected to the rear end of the impactor. The cuttings produced during the rock drilling process are flushed out of the hole by a mixture of wind and water. The mixed gas is injected into the impactor through the center of the drill rod by the powder discharge mechanism and then enters the bottom of the hole through the air groove on the impactor cylinder.

DTH Drilling Rig usage rules

Rig installation and preparation

1. Prepare the rock-drilling cavern, the specifications of which can be determined according to the method of drilling. Generally speaking, the height of the cavity is 2.6-2.8 meters when drilling a horizontal hole with a down-the-hole drill. When drilling upward, downward, or inclined holes, the width of the cavity is 2.5 meters and the height is 2.8-3 meters.

2. Lead the gas and water pipelines, lighting lines, etc. to near the working surface for later use.

3. Erect the pillars firmly according to the requirements of the hole position design. The upper and lower ends of the pillar should be padded with wooden boards, and the horizontal shaft and the snap ring should be installed on the pillar according to a certain height and direction. Use the hand winch to lift the machine and fix it on the pillar at the required angle. Then adjust the hole direction of the drill.

Pre-work inspection

1. When starting to work, carefully check whether the gas and water pipelines are firmly connected. Check for air leaks and water leaks.

2. Check whether the lubricator has been filled with oil.

3. Check whether the screws, nuts, joints, etc. of each part have been tightened. Check whether the column is really strong.

Drilling procedure

When opening the hole, start the motor first, and pull the push handle of the manipulator after the transfer is normal. Make it get proper propulsion, and then pull the handle that controls the impactor to the working position. After rock drilling, you can open the water valve to keep the gas-water mixture at a proper ratio. Perform normal rock drilling work. When the advancing work moves the rod loader to collide with the brace holder, it is to finish drilling a drill rod. It is necessary to stop the operation of the motor and stop the air and water supply to the impactor. Insert the fork into the drill pipe slot of the drill holder, make the motor reverse the slide plate to retreat, and disconnect the joint from the drill pipe. Then connect the second drill pipe, press this button and you will continue to work in a cycle.

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Down-the-hole drilling (DTH) essentially involves a drilling hammer at the bottom of a drill string. It relies on three elements for drilling holes: bit loading (weight), rotation and air. These active elements combine to be efficient at crushing rock. As the drill string slowly rotates, the drilling hammer is forced into the rock repeatedly. Striking power is provided by compressed air driving a piston inside the hammer.
Down-the-hole (DTH) drilling has made it easier for contractors to drill wells faster and more efficiently, and to transition from dirt boring to rock boring just by adding a compressor and hammer to the drill bit.
Usually, contractors working on a dirt bore would pack up and move on to the next dirt bore when they encountered rock, leaving the rock boring for another contractor to complete.
With DTH drilling, contractors can change the drill that they were using for the current directional bore to a rock drill when they encounter rock by connecting the drill with a compressor and a steerable hammer.
 

Where is it Used?

DTH drilling is often used in the mining industry (blast hole drilling), on construction sites, drilling water wells, and in the oil and gas industry.
 

DTH Advantages

1. The DTH system is easily adaptable to most directional drills in a short period of time.
2. Lower operating costs, as the same drill will be used for drilling through dirt and rock.
3. The use of air makes this method very cost-effective as air does not have to be sourced, transported or treated.
4. Less amount of drilling fluid and additives are required.
5. Less weight-on-bit allows for lighter rigs that are easier to set up and takedown.
6. Since cutting force is supplied by reciprocal force, the bit encounters lesser deflection and therefore drills more precisely.
7. Rate of penetration of DTH is 2-5 times greater than the rotary drilling technique.
8. Lesser time consumed compared to when the contractor has to be changed when geology changes.
9. Less wear and tear on the drill bit during drilling operation as the hammer is doing most of the work.
10. DTH requires a minimal amount of rotational torque to cut rock that also allows the hammer to drill straight.
11. Vibrations from the DTH percussive hammer can stimulate the formation to enhance production capability, reducing the need for hydraulic fracturing.

Application
Among all the drilling method, down-the-hole (DTH) drilling is increasingly used and can be very effective in some cases. Down-the-hole drilling mainly has the following six specific applications.

1. Mining includes Surface drilling and Underground drilling
2. RC – Exploration includes Exploration and Grade control
3. Quarrying includes Aggregate & limestone and Dimension atone industry
4. Construction includes Civil engineering
5. Well drilling includes Water well and Energy well
6.Oil and gas includes Shallow drilling and Seismic
 

Compressed Air Power

The DTH hammer is pneumatically powered, with the compressed air propelling it forward to impact and fracture rock. Compressed air also travels through the drill bit into the hole (air exhaust), which blows the chips and dust out of the hole.
 

Quieter Drilling

From environmental and social perspectives, DTH is a good option because it produces much less noise and vibration than many other drilling methods. Quieter drilling means it is often the preferred drilling method when used in cities and populated areas.
 

What We've Learned

The DTH method is the most productive and cost-effective method. It is environmentally friendly, as it produces lesser noise and vibration compared to other drilling methods making it ideal for cities.
It also leaves a lesser carbon footprint as it uses low amounts of drilling mud and additives, reducing the amount of drilling fluid that needs to be recycled and disposed of, in turn reducing the number of trips required for disposal of used mud.
This technology will help contractors do more in lesser time at lesser cost and help keep ahead in a very competitive market.

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