I Direct Burial & Plough in of of Cables

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Direct Laying Of

Optical Fibre Cables

Surveying and planning of project Cable types

Installation methods


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Surveying and planning

Do feasibility study on most cost effective and

practical installation method

Obtain way leaves before final decision

Presence of services like crossings, power, water,

petrol pipelines will influence method Crossings may have to done with overhead routes

Directional boring can be used in special crossings

Soil conditions will influence depth and cost

Vegetation will be important as some are

indigenous


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Cable types

Only Corrugated Steel Tape (CST)

optical fibre cables can be directlyburied and ploughed in


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Installation methods

Plough in of cable with specialisedmachinery

Direct burial of cable

Directional boring


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Plough in method

Machinery

Route preparation

Plough in procedure

Reinstatement after plough in process


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Machinery required

Suitable machine to do pre-ripping of soil

Cable drum carrier

Excavator (TLB) to do small river and culvert

crossings Cable trailer for sub ducts if required

Plough in machine


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Plough in machine

Cable carrying attachment in front of machine

Hydraulic feeder system on drum with tensioncontrol

Rollers over roof of machine with bend radius

protection for cable and sub duct

Feeder system for marking/danger tape

Plough in attachment at back of machine suitableto lay multiple services


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Plough in machine


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Plough in machine


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Plough in machine


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Route preparation

Do road and railway crossings in advance

Remove all obstructions to plough in machinein advance provide temporary supports

Do pre-ripping if required at greater depth

Final pre-rip in same direction as plough in

Pre-trench creek and river crossings with TLB


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Plough in procedure

Excavate at least 5m at start of route

Position plough in machine over open trench

Load cable drum and feed cable through the chute

If sub duct must be laid in process, it can be fed

from cable trailer or laid out in front of plough inmachine

Load marker tape and feed through 300mm above

sub duct


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Plough in procedure (contd.)

Ensure correct sequence out of plough in chute

Provide sufficient cable slack for splicing

Start machine slowly and hold services by hand

in trench

Minimise stoppages during plough in process

Monitor marker tape at feeding system

Repeat same process at end of each length Plough in process can be stopped in middle of

length at night


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Inner ducts must be jointed with Plasson fittings

in trench Build manholes and jointing pits after plough in

process

Plough cable in as near as possible at end of

route and excavate trench as at start

Test all fibres after plough in process to verifyintegrity

Plough in procedure (contd.)


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Plough in machine


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Reinstatement after plough in process

No compaction of disturbed area is necessary

Back blading with plough machine

Level surface with TLB Repair all fences

Replace all stays and struts


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Direct burial

Applications

Installation method


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Applications

In rural areas where plough in can not be done

In urban areas where cables are buried underlayer of ducts which caters for future network

expansion

Road crossings and services that must be

crossed in urban areas will limit cable lengths

that can be ploughed in


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Installation method

Excavate trench as per normal requirements

Limit width to 370mm if only cable will be buried

Bedding and padding material river sand or

sieved material not greater than 5mm Bedding must be 150mm

Lay cable and cover with 150mm padding


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Installation method (contd.)

Install ducts if required on top of cable

Use same bedding and padding material forducts

Cover cable with 300mm backfill material

Use mechanical compaction to compact backfillin layers of 300mm

Build manholes and jointing pits for future

development after cable laying


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Directional boring

Description Applications

Machinery

Procedure

Advantages/Disadvantages


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Description

Directional boring is the drilling of a required

diameter hole between two points at a specific

depth to accommodate a cable or a duct without

disturbing or damaging any infrastructure


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Diagram


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Applications

Crossing streets, highways and railway lines Crossing foundations of buildings

Crossing rivers, pipelines and water drainage

systems


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Machinery


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Machinery


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Procedure Locate all services

Set up drilling rig Mix bentonite mix to suit soil formation

Drill pilot hole up to required position

Fit reamer to drill end and secure cable or duct

Pull cable/duct back while hole is reamed

Ensure sufficient slack


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Advantages / Disadvantages

Accurate

No trenching and reinstatement of surfaces Cost effective

Difficult crossings is possible and done safely

Only 300m is possible

Specialised equipment is needed

Too many deviations in hole will make haulingimpossible

Documents

I Direct Burial & Plough in of of Cables