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Horizontal Directional Drilling

Directional drilling technology is seeing enormous growth. Directional drilling operations, uncommon in the past are now quickly becoming everyday scenes at job sites. The application of TT directional drilling rigs enables parallel installations in lengths up to 500 m. with undercrossing rivers or water courses being common practice. The steering technique allows very sophisticated operations, even drilling beneath industrial complexes. The application range extends to all pipe construction including gas, district heating, water supply, the installation of pressure lines for sewers as well as cable protection pipes for telecommunications, traffic routing systems, emergency call boxes or low, medium, high voltage and fibre-optic conductors.

 

 

This installation technique has proved to be extremely friendly towards the environment, with only minor ecological interventions and there are several reasons for also using the HDD steerable method application in town centre areas. The main reasons for this being construction costs, construction times, procedures for gaining permission, soil movement, surface restoration and traffic disturbance, when compared to open trenching methods. The normal course of action prior to using the drilling operation is described in the following:

  1. Planning / preliminary survey
  2. Drill rig and drilling tool selection 
  3. Pilot bore and location
  4. Back-reaming or upsizing bore(s) 
  5. Pulling in the pipe
Basically, the drill rig consists of three main system components:

  1. Drill rig / drilling tools
  2. Bentonite mixing system incorporating a two-tank system and a recycling system,  if volume requires
  3. Hydraulic power unit for driving the Bentonite mixing system
 
A well planned HDD operation includes a preliminary survey of the bore path area to investigate the condition of the soil and look for other already existing pipes/cables. The choice of the drill rig depends upon the bore length, the diameter of the pipe to be installed and the soil type. Compliance with the planned bore path and gradient course is the main problem of the pilot bore if the fluid assisted technique fails due to mechanical ground resistance. To overcome this, high thrust and pulling forces are required, in many cases reaching the limits of capacity. The application of Bentonite may be able to facilitate the pilot bore and pipe pulling, but experience shows that the technical and economical advantages of “soft boring” can hardly be realised in difficult soil conditions with coarse grained components, considerable rock inclusions or building rubble deposits. For these circumstances, TT drill rigs with built-in percussive impact units can be employed; these units can be switched on additionally when the drilling progress becomes unsatisfactory due to problematic ground conditions. To simplify it is a matter of impacting forces similar to that of a displacement hammer relocated to the drill rig as the combination of fluid-assisted drilling with a percussive impact unit allows thrust and steer ability through the problematic ground up to soil grade 5, sometimes even grade 6.


The high demands and expectations regarding the quality of the drilling job to be done require precise detection and steering, with location carried out according to the transmitter-receiver principle. The drilling crew permanently monitors the course of the bore head and all measured values are logged while the directional corrections are passed on to the drilling rig operator via radio transmission. The data found in this way can be stored immediately for printing later with the help of a PC or laptop. Directional control works according to the “clock-hand principle” via slanted surface of the head which changes directions similar to the clock hand adjustment. On arrival at the target pit, the drilling head is replaced with one or more intermediate reaming operations with immediate pulling in of the pipe/s. At present pipes made of PE plastic, steel and cast iron up to OD 600 can be pulled in, single or bundled together. When pulling in PE plastic pipes (especially for gas and potable water), the permissible tensile loads according to GW 321, 322 and 323 shall not be exceeded. At the client’s request, the tensile load forces affecting the pipe are measured and logged. TRACTO-TECHNIK offers a simple device for measuring the tensile loads.

You can also measure the exact position of the installed pipe using Grundocontrol by TRACTO-TECHNIK after completing the drilling job.

The fluid-assisted horizontal directional drilling method is described in the relevant rules and standards GW 304 Pipe Laying and ATV-A 125 respectively. 

Advantages of the method:

  • No breaking up of valuable ground surfaces, no surface damage (highways and road surfaces, resident’s properties etc.) and no reinstatement -  
  • High economical advantages
  • Social costs remain low because diversions, road cones,  barriers and set-up of traffic light signal installations etc. are avoided
  • Recognised procedure
  • Short set up times - short drilling and construction times
  • Very economical method for under river crossings
  • Support of the bore with the dynamic impact of the hammer facilitates thrust and steer ability in grounds of soil grade 5 or even 6
  • Simple to operate 
  • Tensile load measurement and data logging are possible
  • Wide range of applications  

 

The product family of steerable HDD technology has been developed and significantly improved

The small directional drill rigs of the GRUNDOPIT line are listed  here.

 Click here for more information on products



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