Figure Typical HDD Drill

must be anchored to provide a reaction against which the mechanical system can operate. Anchoring is typically done by driving stakes through openings at the front of the rig, attaching the rig to a buried weight, or simply attaching the rig to a large, heavy piece of equipment on the surface. The drill rig must provide sufficient thrust (and the drill pipe sufficient strength) to advance the drill string the full length of the proposed bore hole and sufficient pulling force to retract casing into the completed hole. The relationship between thrust and drilling distance also depends on the formation type and use of drilling fluids.

The drill rig must also provide torque to the drill string. Most drilling methods require that the drill string be rotated while it is advanced into the bore hole in order to reduce drag friction on the string. The drill rig must have sufficient capacity to overcome bore-hole friction and supply the necessary torque to the drill string throughout the proposed length of the hole. The drill rig must provide a means to deliver drilling fluid to the drill string. Typically this is accomplished using a pump, capable of handling the drill slurries, to inject fluid through the drill rods and out nozzles in the bit. Most HDD contractors have several directional drill rigs of varying sizes to accommodate various drilling conditions and project demands.

Small (Mini) Rigs

The mini-rig category typically includes drill rigs rated at less than 40,000 pounds of thrust and pullback, less than 4,000 foot-pounds of torque, and a drilling-fluid pump system of less than 75 gallons per minute. Mini drill rigs are usually mounted on a trailer, truck, or a self-propelled track. The self-propelled versions are self-contained units with engine, hydraulic power, and the drilling-fluid pump on the

Directional Drilling RigMini Driil Pump
FIGURE 3-2 Mini HDD Drill Rig © Vermeer Manufacturing Company, all rights reserved

vehicle. Drill units that have auxiliary power and off-board drilling-fluid pump systems are called umbilical units. Drill rigs that are rated below 20,000 pounds of thrust and pullback are used mainly for utility cable and small-diameter product pipes in congested areas. Some of the higher-end models in this category can be used to drill in gravel, cobble, and other formations where the bore-hole stability is hard to maintain. For small drill rigs specialty drilling systems and down-hole tools are now available for drilling through rock of medium hardness as well as cobbles.

Medium (Midi) Rigs

The midi-rig category typically includes drill rigs rated at 40,000 to 100,000 pounds of thrust and pullback, 4,000 to 20,000 foot-pounds of torque, and a drillin-fluid

Vermeer Drill Rigs
FIGURE 3-3 Mini HDD Drill Rig © Vermeer Manufacturing Company, all rights reserved
Horizontal Directional BoringHorizontal Directional Boring

FIGURE 3-4 Midi

HDD Rig © Vermeer Manufacturing Company, all rights reserved

FIGURE 3-4 Midi

HDD Rig © Vermeer Manufacturing Company, all rights reserved pump system of 50 to 200 gallons per minute. Most of the drill rigs in this category are self-contained units. Midi rigs are typically used for installing products up to 16 inches in diameter at distances up to 2,000 feet. This category of drill unit is the primary type used for the installation of municipal pipeline products. These units are compact and can be readily used in urban areas, while offering the capacity to install relatively large-diameter water, gas, and sewer force mains. These units can handle soft to hard soils and soft rock formations. When utilizing down-hole mud motors and specialty reamers, these units can perform drills in hard-rock formations.

Large (Maxi) Rigs

Maxi HDD rigs typically are used in large operations with multiple trailer-mounted support equipment and substantial mobilization periods. These units have higher

Vermeer Maxi Rig

FIGURE 3-5 Midi HDD

Rig © Vermeer Manufacturing Company, all rights reserved

FIGURE 3-5 Midi HDD

Rig © Vermeer Manufacturing Company, all rights reserved

Medium Hdd Rig

FIGURE 3-6 Maxi

HDD Rig © Vermeer Manufacturing Company, all rights reserved

FIGURE 3-6 Maxi

HDD Rig © Vermeer Manufacturing Company, all rights reserved operating costs and require large workspace areas. This usually restricts their use in the urban utility HDD market. Maxi drill rigs are typically used for large-diameter pipelines (16 to 48 inches) or exceptionally long drills up to 6,000 feet. This category of drill rigs is rated at greater than 100,000 pounds of thrust and pullback, more than 20,000 pounds of torque, and with a drill-fluid pump system greater than 200 gallons per minute.

Short Radius Horizontal Drilling

FIGURE 3-7 Maxi

HDD Rig © Vermeer Manufacturing Company, all rights reserved

FIGURE 3-7 Maxi

HDD Rig © Vermeer Manufacturing Company, all rights reserved

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