Glossary

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Hand Shield

An open face shield for manual excavation.

Hole Openers

Downhole tool that uses rolling cutters to enlarge a hole in hard soil and rock formations.

Horizontal Directional Drilling (HDD)

Method for the installation of pipes, conduits and cables using a surface-launched drilling rig. A pilot bore is drilled using a rotating drill string and is then enlarged by a back reamer to the size required for the product pipe. During the pilot bore the direction of the drill string is controlled by the orientation of a slanted face to the drill head, eccentric fluid jets or a combination of these, usually in conjunction with a locator.

Hose Lining

Lining system for pressure applications where a woven flat fiber reinforced polyethylene hose is pulled into the host pipe and secured by special end fittings. Once inserted, the woven hose liner is inflated to the service pressure expanding the liner until it contacts the wall of the host pipe.

Hydraulic Jacks

High pressure hydraulically operated jacks providing the power to move the pipeline.

Hydrofracture

The inadvertent loss of drilling fluid from the borehole annulus to the surrounding soil as a result of excess downhole fluid pressure.

Hydrolock

A phenomenon that occurs when circulation is lost creating a hydraulic cylinder in front of a reamer with holding pressure greater than the pullback capacity of the drill rig.