Page 229 - Trenchless Technology Piping Installation and Inspection

Pr oject Considerations for Horizontal Dir ectional Drilling 193

should be noted that in Maxi-HDD operations, due to the larger size,
and greater stiffness of product pipes being installed, the minimum bore
path radius of curvature may depend on the product pipe diameter.

Maxi Horizontal Drilling Rig
Equipment required for a typical Maxi-horizontal drilling operation
can be transported to the job site in approximately seven tractor-trailer
loads. A workspace of 100 ft by 150 ft is typical (Fig. 5.4a) at the drill
rig side. A similar size area at the bore path exit (pipe entry), plus a
50 ft wide segment of sufficient length to accommodate the assembled
pipe and associated equipment and handling (see “Product Pipeline
Fabrication” section below, and as indicated in Fig. 5.4b), will be ade-
quate for most operations. If necessary, the workspace at the drill rig
side for HDD equipment may be reduced to a minimum of 60 ft by 150
ft, but this would restrict the size and capacity of the drilling rig. Space
requirements will vary depending on the make and model of the drill-
ing rig and the position of the various components. However, the
locations of the principal components (drill rig carriage, drill rod, and
control trailer) are fixed by the entry point. The rig carriage must be
positioned in line with the drilled segment and close to the entry point.
The control trailer and drill rod must be positioned adjacent to the rig.
The workspace must be cleared and graded level. The related
equipment is typically supported on the ground surface. Timber mats
may be used where soft ground is encountered.

Product Pipeline Fabrication
Pipeline fabrication is accomplished using the same construction meth-
ods employed to lay a pipeline in a trench, therefore requiring similar
workspace. The location of the fabrication workspace is controlled by
the drilled segment exit point. Space must be available to allow the
pipe to be fed into the drilled borehole. It is preferable to have work-
space in line with the drilled segment and extending back from the exit
point the length of the assembled pipeline plus 200 ft. This will allow
the pipeline to be prefabricated in a single continuous length prior to
installation. If sufficient space is not available, the pipeline may be
assembled in several sections, to be welded or fused together during
installation, or restraint joints can be used (see Chap. 4).
This workspace must also be cleared, but need not be graded level.
Equipment is typically supported on the ground surface. Timber mats
may be used where soft ground is encountered. Figure 5.4b provides
additional information describing the pipe side of the operation.

5.3.4 Drilling Fluids
The primary functions of drilling fluids in Maxi-HDD systems include
cutting or jetting of soft soils, transmission of rotary power to a mud
motor, cleaning of cutters, cooling of downhole tool and electronics, trans-
portation of suspended cuttings, stabilization of the drilled borehole