The use of pipe & cables installation techniques can reduce environmental impact, social costs and at the same time provide economic alternatives to traditional open cut methods. Pipe & cables installation techniques include:
Micro tunnelling is used here as a general term to describe remotely controlled mechanical tunnelling systems where the spoil is removed from the cutting head within the new pipeline which is advanced by pipe jacking. Micro tunnelling machines have now been developed to work from drive shafts in almost all types of ground conditions. The cutting head has to be carefully selected to deal with the expected ground conditions, with the appropriate cutting tools and crushing devices for the range of gravels, sands, silts, and clays. Water or bentonite may be used to convert the soil into slurry at the cutting face. The slurry is then pumped to the surface where the solids are separated before disposal. Both systems provide face support by mechanical earth pressure balance. Slurry pressure at the face can also be used to combat external ground water.
Guided Boring & Directional Drilling
Horizontal Directional Drilling (Guided Boring) is ideal for the underground installation of gas, electric, water, telecommunication or soil remediation lines - without excavation or trenching. Horizontal directional drilling ensures minimal or no environmental disruption and is an excellent choice for installations in diverse rock and soil conditions. Once the pilot bore is completed, a reamer/backreamer is attached to the drill stem string and pulled back -- enlarging the bore wall to comfortably accommodate the product wire, conduit or pipe that is subsequently pulled into place.
Rocks can be classified in strength as:
- soft rock 2,500 to 5000 psi, (17 to 35 mpa)
- medium rock 5000 to 10,000 psi (35 to 70 mpa)
- hard rock 10000 psi upwards.
Hardest surface rocks being max 40,000 psi (270 Mpa). The key to successful ``Rock Boring`` is by engineering, planning and selection of the correct drilling package knowing the particular ground conditions / rock strengths etc. We can still use the ``Directional Drilling m/c`` but with certain modifications / special tooling, comprising of:
- drill bit
- drill motor
- hole opener / reamer
The drill bit is probably the most important of all the tooling. Depending on the rock strength it is usually either roller cone bit, either a TCI (tungsten carbide inserts) or milled tooth diamond. These hole openers rotate at only 50 to 100 rpm. Optimum penetration rates are achieved by operating the "Drill Motor" at the recommended flow rate for Drill Bit size (diameter). This mud flow rate is dictated by;
- mud pump flow rate
- bore diameter of drill rods
Drill Rods as well as having a large enough bore for the mud flow should also be have enough strength for the rotary torque and the pull back of the Hole Openers /pipe weight. Guidance of the "Pilot Bore" is either a "walk-over" or remote "wire line" tracking system as is normally used with Horizontal Direction Drilling.
Cable pulling is the oldest method of inserting a cable into existing ducting. This entails feeding a winch rope through the ducting and attaching it to the cable with a compression sleeve or sock. As the cable is winched into the ducting the sock tightens its grip on the cable. On larger cables a cable pusher is used to assist the winch and thus reduce tension in the cable.
Cable Blow in Systems
Cable blowing is used to insert relatively small diameter, light weight electric or fibre optic cables into existing ducting. Compressed air is introduced into the duct and the velocity of the air moves the cable. This is particularly relevant to fibre optic cables.
LOCATION, DETECTION & INSPECTION
There are various systems involved in location, detection and inspection of underground tunnels and infrastructure, including:
Ground Probing Radar (GPR)
The first ground penetrating radar survey was performed in Austria in 1929 to sound the depth of a glacier. Since then its development has permitted extensive use in many sectors of industry from utilities to archaeology. GPR uses electromagnetic wave propagation and scattering to image, locate and quantitatively identify changes in electrical and magnetic properties in the ground (Olhoeft, 2000). The resolution of the image produced depends on the ground strata but with favourable conditions it is in the magnitude of ustomize s.
Mapping & GIS
Most if not all Utilities hold information about their networks electronically. These systems provide the ability to display a utility’s networks in relation to a background map. This allows utilities to hold accurately surveyed information to pinpoint the exact location of their services although data accuracy is still a contentious issue with many utilities. Data in systems such as geographical information systems (GIS) is held as features or objects and each feature can be held as a separate map layer allowing users to ustomize the display.
Since its peak in 1994/95 leakage has fallen by a commendable 33% or the equivalent of the daily needs of about 12 million people. The 2001/02 leakage level was down to 146 litres per person per day, the equivalent of 1.5 baths per person per day. Traditional methods can now be supplemented by exciting new techniques such as ground penetrating radar.
The purpose of intelligent pigging is to assess the condition of a metallic pipeline. By far the majority of pipeline inspection is on steel pipes with some on Ductile Iron pipe. There is a selection of pigs available to determine different aspects of pipe condition. The loss of wall thickness can be determined, lamination can be detected as can damage to a pipeline. In the majority of instances differential pressure across the pig is used to move it forwards at a controlled speed. On board intelligence records data regarding the pipelines condition and location, which can then be used to locate any faults found from ground level, following down loading of the information at a data gathering facility.
EQUIPMENT & MATERIALS
- pipe handling equipment
- pipe pushers
- ancillary pipe equipment
- PE pipes & fittings
- clayware pipes & fittings
- concrete pipes & fittings
- metal pipes & fittings