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Horizontal directional drilling: advantages of the method and work phases

1.What problems does the HDD drilling technology solve?

2.Advantages and disadvantages of the horizontal directional drilling method, What equipment is involved?

3.Stages of HDD drilling

Gone are the days of digging trenches to lay communications. Trenchless laying technology, such as horizontal directional drilling (HDD), is gaining popularity due to its minimal disruption. Increasingly, situations arise when the classic (with digging of trenches) laying of communications is undesirable or impossible. In these cases, the HDD method comes to the rescue with its special drilling rigs, which make it possible not to disturb the top layer of soil. The technology is used to lay the following types of communications:

Water supply (including for transporting drinking water).

High pressure gas pipeline.

Heating networks.

Gravity sewerage.

Electrical cables.

Cases for communication cables, telephone and fiber-optic communication lines (fiber-optic communication lines).

Replacement of outdated communications.

Formation of underground passages of any degree of complexity.

zlconn zl350a/760 HDD machine india working site
zlconn zl350a/760 HDD machine india working site

Top Advantages of Horizontal Directional Drilling:

1.Work can be carried out in any place: in the historical center of the city, under densely populated areas, under roads and railways, buildings and water barriers, building structures and sites.

2. HDD directional drilling is carried out at any time of the year.

3. There is no risk to other utility networks; obstacles on the surface (buildings, plants) can be ignored.

4. The HDD technology is environmentally friendly. It does not affect ground objects or road surfaces; the landscape remains intact (which is important for suburban areas).

5. In comparison to the open method, laying communications is faster and requires less time. There’s no need to remove fences, cut down bushes, or damage the lawn.

6. Networks laid using the HDD method have a longer service life and avoid soil settlement, a common issue with trench digging.

80ton hdd drilling machine
80ton hdd drilling machine

The HDD drilling method has two significant disadvantages:

If you need to lay communications over a long distance or at a considerable depth, it will cost more than the traditional method.

For standard equipment, the maximum range does not exceed 350-400 m. If a longer route is planned, joints will have to be made.

What equipment is involved in HDD drilling?

Horizontal directional drilling is a complex technology, so the work involves a variety of drilling equipment and specialized materials. The standard set of equipment is as follows:

HDD installation (HDD drilling machine). Specialized equipment with rod feeder and control panel. The chassis can be tracked or wheeled and is powered by a diesel engine. The main characteristic: maximum broaching force, drilling length and expansion diameter are also important.

Mini installations Compact HDD machine cope well with installation in hard-to-reach places, but have a reduced service life. The capabilities are limited to a puncture length of up to 100 m, and the traction force does not exceed 50 tons.

Control system. Drilling must be carried out under constant supervision, and for this purpose a locating probe is used. It is located on the drill head, and its movement is tracked using a locator. The detector records the operating parameters of the process: angle and direction of drilling, temperature of the working area, drill speed.

Drilling fluids. They facilitate the drilling process and affect the productivity and efficiency of work. The choice of flushing liquid depends on the quality and composition of the soil. Sandy soils intensively absorb water, clay soils swell and stick to the drill. To prevent breakdowns and delays, bentonite drilling fluids with various additives and stabilizers are used.

Copper-graphite grease. It is needed for processing dynamic parts and threaded connections of drill rods to prevent jamming. Modern lubricating compounds have the form of a thick, flowing paste; include petroleum oils, graphite and copper powders, lithium stearate, improving additives.

Auxiliary tool. To organize HDD drilling, the technology requires devices that help push (pierce) the soil. These are a variety of expanders, rods, and a motor pump that removes drilling fluid.

HDD drilling technology involves going through the following stages:

Video description

How HDD technology works in the following video:

Construction of a working well. To expand the well to the desired diameter, it may take from 1 to 3 consecutive passes of the reamer (in this case, it is changed each time to a device of a larger diameter). The number of passes depends on the characteristics of the installation and soil parameters.

The diameter of the finished well is 25-30% greater than the diameter of the pipeline.

Pipe pulling. Using special fasteners and clamps, the string of pipes is pulled into the well. In long wells, the force for tightening the pipes is created by the drilling rig, which also lays the pipe correctly. If the well is small-sized, lined with polymer pipes, installation can be done manually.

Cementing. If laying is carried out in difficult geological conditions, a cementing solution is pumped under pressure into the space between the pipe and the well wall.

After the pipe is in the correct position, it is disconnected from the drill string, the working platform is rolled up and removed, and the as-built documentation is handed over to the customer, and horizontally inclined drilling is considered completed.

The cost of HDD services depends on the diameter of the pipes (the cost of laying 1 m.p. is considered), the equipment used, and the characteristics of the soil (hard rocks are considered difficult).

Briefly

Horizontal directional drilling allows you to bypass any obstacles without extra costs and preserve the landscape on the site. Before starting work, a careful analysis of the territory, existing communications and soil is carried out; this allows you to select the right tools and materials.

At the first stage, a pilot well is prepared. Its task is to outline the trajectory for laying communications. Betonite is fed into the well through special holes; it strengthens the soil and brings remaining soil to the surface. Then the well is expanded to the required diameter and a pre-prepared pipeline string is pulled through, monitoring the correct installation.

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