With the entry of urban pipelines into the ground, the expansion of highways and railways, and the improvement of environmental protection requirements, trenchless construction has become the preferred method for laying electricity, communication, gas, water supply and drainage pipelines. Trenchless drilling rigs (also known as horizontal directional drilling rigs) complete pipeline crossing without damaging the ground, which has the significant advantages of fast construction speed and small interference to traffic and the environment. However, the requirements for drilling rigs vary greatly from different projects, and improper selection can lead to low efficiency at best, and inability to complete crossing at worst. This article starts with five key parameters to help you choose scientifically.

1. Key parameter 1: Pullback force - determine the maximum crossing length and pipe diameter

The retraction force is the ability of the drill rig to "pull" the reamer or pipe back, usually in tons (t) or kilonewtons (kN). It directly determines how long and large the pipe diameter the drill can complete.

Experience Reference:

Electricity/communication pipes within 200 meters and below DN200 in diameter: 15-25 tons of traction force

Gas/water supply pipes through 300-500 meters with a pipe diameter of DN300-DN500: return towing force 40-80 tons

Large pipe diameter that crosses more than 600 meters or pipe diameter DN600 or more: return towing force of 100 tons and above

Selection suggestion: Select the rated pullback force of the drilling rig according to 1.3-1.5 times the expected maximum drag force, leaving room to cope with changes in actual working conditions (such as increased formation resistance).

2. Key parameter 2: torque - determines whether hard formations can be drilled

Torque is the ability of the drill bit to rotate through soil or rock, usually in N·m (N·m) or kN·m (kN·m). When working in hard clay, dense sand layer, and weathered rock, high torque is a prerequisite for smooth drilling.

Experience Reference:

Soft soil, ordinary clay: torque 4000-6000 N·m

Hard clay, dense sand layer: torque 8000-12000 N·m

Pebble layer, weathered rock, hard rock: torque above 15000 N·m, and need to be equipped with rock drilling tools (such as tricone drill bits, pneumatic DTH hammers)

Selection suggestion: First understand the stratum of the crossing path, if there is a hard layer or pebbles, the high-torque model should be given priority or the guided drilling + reaming grading process should be adopted.

3. Key parameter 3: feed/back towing speed - determines the construction efficiency

The feed speed (drill pipe advance speed) and the dragback speed (pipe pulling speed) affect the construction time of a single hole. Typically the speed range is 0-20 m/min, but is actually limited by the hardness of the formation and the combination of drilling tools.

Note:

It is not that the faster the better, it needs to be adjusted according to the formation to prevent the guide from being out of control or overloading the drilling tool

When crossing long distances (> 500 meters), it is recommended to choose a drilling rig with an automatic hydraulic control system to achieve automatic matching of speed and torque, reducing the difficulty of operation

4. Key parameter 4: drill pipe diameter and length - affect the traversal accuracy and handling convenience

Drill pipe diameter: small diameter drill pipe (Φ60-73mm) is suitable for short distances, small pipe diameter crossing, and light handling; Large diameter drill pipe (Φ89-127mm) has good rigidity and is suitable for long distances and large torque transmission, but it is heavier.

Drill pipe length: commonly 3 meters or 4.5 meters. The 3-meter drill pipe is suitable for urban construction sites with limited operating space; The 4.5-meter drill pipe reduces the number of joints and improves the efficiency of deep hole drilling.

5. Key parameter 5: The size of the whole machine and the way of walking - adapt to narrow construction sites

Municipal construction is often carried out in crowded roads, communities or green belts with limited equipment size.

Split drilling rig: the power station, the operating table and the main body of the drilling rig are separated, which can be disassembled and transported, and is suitable for passing through narrow passages

Integrated rubber crawler drilling rig: The whole machine is compact, can walk on asphalt without damaging the road surface, suitable for construction sites with frequent changes

Vehicle-mounted drilling rig: fast transition speed, suitable for continuous operation in the suburbs and long-distance construction sites

The trenchless drilling rigs produced by our company cover a variety of specifications of 15 tons to 150 tons of traction force, and can be equipped with rock drilling guidance system and automatic mud mixing device to adapt to common formations such as clay, sand layer, pebbles, and weathered rock.

6. Quick selection comparison table

7. Precautions other than selection

Mud systems cannot be ignored: trenchless drilling requires large amounts of mud for wall retaining, slag carrying and lubrication. When choosing a drilling rig, pay attention to the supporting mud pump flow, pressure and mud recovery equipment (vibrating screen, desiltator), otherwise the drilling efficiency will be greatly reduced.

Guide configuration: Medium and long-distance crossing must be equipped with a wireless guide or wired guide system to accurately control the depth and orientation of the drill bit to prevent damage to the existing pipeline.

Operator training: Trenchless construction requires high operator experience, and it is recommended to require manufacturers to provide on-site training or assign experienced operators.

Finally, it is recommended that before purchasing a trenchless drilling rig, provide the specific engineering parameters (traversal length, pipe diameter, formation conditions, site restrictions) to the equipment manufacturer's technicians. Our company can provide selection calculations and construction plan suggestions according to your needs to ensure that the equipment is in place in one step and does not waste investment.