DIRECT PIPE
Microtunneling and horizontal directional drilling (HDD) are trenchless pipeline installation methods that are used extensively for laying pipelines. When two such tried and tested methods are combined, the result is usually a hybrid that incorporates the advantages of both methods. The direct pipe method is the trenchless installation method that results from the combination of microtunneling and HDD to give rise to a method that is versatile, quick, efficient and cost effective.
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It’s a one-pass method that does not require back reaming as in HDD, and does not require a shaft for pipe thrusting as in microtunneling. The direct pipe method involves simultaneous excavation of the borehole and installation of the pipeline – all in one step – and is suitable for any ground/soil condition.
The product pipeline is welded into a string, inspected, and positioned on rollers. The cutting machine is installed at the leading end of the pipe string, and the pipe thruster is set up to drive the pipe into the ground. Instead of a jacking machine thrusting the pipe into the borehole as in a pipe jacking operation, a pipe thruster clamps the pipeline from the side and pushes the pipe and the cutting machine using its two thrust cylinders in strokes of 5 meters. The thruster is well anchored to a structure and uses clamps to transfer its leverage without damaging the pipe coating. Typical diameters of pipes that can be installed using the direct pipe method are 26”, 42”, 48”, 56” and 60”; maximum distance installable is a function of diameter and geological conditions at site, and varies from 300 m to 1,500m.
