Glossary

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Packer

See Compression Ring.

Packing

Material placed between pipe joints to distribute the jacking loads.

Piezometer

Small-diameter monitoring wells that allow ground water levels or pressures to be monitored.

Pilot Bore

First, usually steerable, pass of any boring operation which later requires back-reaming or other enlargement. Most commonly applied to guided drilling, directional drilling and 2-pass microtunnelling systems

Pilot Tube Method

A multi stage method of accurately installing a product pipe to line and grade by use of a guided pilot tube followed by up-sizing to install the product pipe

Pipe Bursting

Replacement method in which an existing pipe is broken by brittle fracture, using mechanically applied force from within. The pipe fragments are forced into the surrounding ground. At the same time a new pipe, of the same or larger diameter, is drawn in.

Pipe Eating

Replacement method, usually based on microtunnelling, in which a defective pipe is excavated together with the surrounding ground and a new pipe installed. The microtunnelling shield machine will usually need some crushing capability. The defective pipe may be filled with grout to improve steering performance. Alternatively, a proboscis device to seal the pipe in front of the shield may be used.

Pipe Jacking

A system of directly installing pipes behind a shield machine by hydraulic jacking from a drive shaft such that pipes form a continuous string in the ground.

Pipe Lubricant

See Lubrication

Pipe Pulling

Method of replacing small diameter pipes where a new product pipe is attached to the existing pipe which is then pulled out of the ground.

Pipe Ramming

Non-steerable method of forming a bore by driving a steel casing, usually open-ended, with a percussive hammer from a drive pit. The soil may be removed by augering, jetting or compressed air. In appropriate ground conditions a closed casing may be used.

Pipe Splitting

Replacement method for breaking an existing pipe by longitudinal splitting. At the same time a new pipe of the same or larger diameter is pulled in behind the splitting tool.

Point Source Repair

See Localised Repair

Pointing

Method of repairing a brick sewer or manhole by the application of cement mortar where loss has occurred.

Potholing

Method using vacuum excavation for obtaining visual confirmation of utilities and underground obstructions near or crossing the planned bore path.

Power Pack

A hydraulic pump unit feeding fluids to activate the hydraulic jacks.

Preconditioning Work

That part of a project, usually before renovation work on a pipeline, that includes preparatory cleaning and internal inspection.

Preparatory Cleaning

Internal cleaning of pipelines, particularly sewers, prior to inspection, usually with water jetting and removal of material where appropriate.

Pressure Plate

A steel pressure plate located between the rear end of the jacks and the thrust wall to backspread concentrated loadings.

Product Pipe

Pipe used for the conveyance of water, gas, sewage, and other products and services.

Pull-Back

That part of a guided boring or directional drilling operation in which the drill string is pulled back through the bore to the entry pit or surface rig, usually installing the product pipe at the same time.

Pull-Back Force

Tensile load applied to a drill string during pull-back. Guided boring and directional drilling rigs are generally rated by their maximum pull-back force.

Pump Capacity

Measured in gallons per minute or similar measurements of flow; along with thrust/pullback and torque, one of three measurements typically used to describe and classify drill rigs and their suitability to successfully perform an installation.

Push Ring Adapter

Mechanical structure mounted on the thrust ring to prevent the thrust ring from coming into contact with the pipe collar and causing damage to the collar.