   |
||
| Member of Minnesota and National Ground Water Associations | ||
Technique The process is used for installing infrastructure such as telecommunications & power cable conduits, water lines, sewer lines, gas lines, oil lines, product pipelines and environmental remediation casings. It is used for crossing waterways, roadways, shore approaches, congested areas, environmentally sensitive areas, and areas where other methods are costlier. Directional boring is used instead of other techniques to provide less traffic disruption, lower cost, deeper and/or longer installation, no access pit, shorter completion times, directional capabilities, and environmental safety. Drilling Process HDD is a trenchless construction method that involves drilling a small pilot hole, using technology that allows the drill to be steered and tracked from the surface. The pilot bore is launched from the surface at an angle between 8 and 20 degrees to the horizontal, and transitions to horizontal as the required depth is reached. A bore path of very gradual curvature or near-straight alignment is normally followed to minimize friction and to stay within the allowable joint deflection and the allowable curve radius for the pipe. This minimizes the chance of getting the pipeline “hung up” in the soil or damaging the pipe. The pilot hole is enlarged (usually approximately 1.5 times the largest outside diameter of the new pipe) by pulling back increasingly larger reamers, or reaming heads, from the pipe insertion point to the rig side. To achieve the appropriate bore path size it may be necessary to perform several reaming operations. Generally, all reaming procedures prior to the actual product installation are referred to as pre-reams, and the final ream to which the product pipe is attached is referred to as the back ream. After the pre-reams, the pulling head and connecting product pipe are attached to the reamer using a swivel, a device that isolates the product pipe from the rotation of the HDD drill pipe. The product pipe is then pulled behind the final reamer back through the horizontal directional drill path to the exit pit on the rig side. Drilling Fluid
For HDD, the proper drilling fluid mixture and delivery pressure is heavily dependent upon the type of soil encountered. It must be formulated for the anticipated geological conditions. For simplicity, soil conditions may be defined as either a coarse soil (sand and gravel) or a fine soil (clay, silt, and shale). In general, for coarse soils bentonite should be used, while for fine soils polymers (possibly added to a bentonite base) are recommended. Locating & guidance
There are two types of locating equipment for locating the bore head: the ‘walk-over’ locating system or a 'wire-line' locating system. In both of the systems a sonde, or transmitter, behind the bore head registers angle, rotation, direction and temperature data. This information is encoded into an electro-magnetic signal and transmitted through the ground to the surface in a walk-over system. At the surface a receiver (usually a hand-held 'locator') is manually positioned over the sonde, the signal decoded and steering directions are relayed to the bore machine operator. In a wireline system, this information is transmitted through the cable fitted within the drill string. Both systems have their own merits and depending upon the site requirements a particular system is chosen. General The technique has extensive use in urban areas for developing subsurface utilities as it helps in avoiding extensive open cut trenches. The use however necessiates that the operator must have the complete information about the existing utilities so that he can plan his hole alignment to avoid damaging those utilities. Since uncontrolled drillings can lead to such damages different agencies/government authorities owning the urban 'right-of-way' or the utilities have formed their rules for safe work execution. For standardization of the techniques different Trenchless Technology promoting organizations have developed Guidelines for this technique. | ||
| 2214 NW Grand Rapids, MN 55744 Phone: 218-326-5859 / Fax: 218-327-0734 |
||
| Let Our 46 Years of Experience Save You Money!! | ||
Horizontal directional drilling (HDD), is a steerable trenchless method of installing underground pipes, conduits and cables in a shallow arc along a prescribed bore path by using a surface launched drilling rig, with minimal impact on the surrounding area. Directional boring is used when trenching or excavating is not practical. Directional boring minimizes environmental disruption.
“Drilling mud” is normally utilized to lubricate the cutting head during the drilling operation and stabilize the reamed bore path
prior to and during pull-back. The “drilling mud” usually consists of a mixture of fresh water and bentonite clay; however, other
materials—such as polymers—are sometimes used. Bentonite is a naturally occurring clay mineral that forms a mud when mixed
with water. Drilling fluids are characterized by their viscosity, gel strength, filtration, fluid loss, fluid density, pH, and lubricity. The
principal functions of drilling fluids used in HDD are:
Location and guidance of the drilling is very important part of the drilling operation as the drilling head is under the ground while drilling and in most cases not visible from the ground surface. An uncontrolled or unguided drilling can lead to substantial destructions. By properly locating and guiding the drill head such destruction can be avoided.