FLOW CHART FOR CHEK ON RECEIPT OF CABLE ::

Great deal of attention is to be paid during laying of cables. As the cable laying is resorted to through outside agencies, departmental officials should exercise a close supervision of activities in progress . The contractor may be considered as a businessman interested in getting maximum profit for minimum effort. His as well as his worker’s intention, therefore maybe more on completion of work speedily rather than caring for standards, precautions, warning to pedestrians and vehicular traffic, damage to existing cable etc.

Therefore supervision by departmental officials is necessary. Being an underground activity. once laid and the trench back filled, it is difficult for an inspecting official to see the defect directly. It is necessary to dig trial pits at suspected spots to check for correct depth, warning layer. GI Pipe, clearance between water pipe and cable etc. Alternatively the best way of supervision however will be to see on day-to-day basis and conduct surprise checks at random. It is suggested that the following nine commandments may be enforced on the contractor so as to achieve satisfactory results.

I. Mark the route where cable is to be laid and a route map issued to the contractor who has to strictly follow the same.

II. Mark the route where Telecom and Electric cables exist and ask him to take special care to avoid damage/accidental contact.

IV. Earmark BT/Berm cutting for strict compliance and avoid inconvenience to smooth flow of traffic or pedestrians.

V. Enlighten contractor about precautions such as drawing cables using cable grip &

cable rollers where necessary. Let him engage more men for paying out and laying in cities to avoid damage to the cable and inconvenience to traffic.

VI. He should use winch, cable rollers, pulley blocks, nylon rope etc while higher size cables are drawn in ducts. he should ensure that draw hooks are attached to the cable ends and only moderate pulling tension is applied on the cable.

VII. He should use proper warning layer over cable as per instructions and should the identification tags/collars at specified intervals before closure of trench.

VIII. He should properly mark all jointing spots and leave only optimum joint length on each cable as per requirement of DOT so that no cable is wasted at the time of jointing.

IX. He should immediately report to construction Officer DOT any instance of objection raised by PWD/Local Authority or private individual so that such grievances can be settled by the construction Officer amicably.

3.3.1 Tender Conditions.

The practice of calling sealed tenders, accepting the lowest rates and awarding the work for more than one financial year creates some practical difficulties. Since the labor rates and other incidentals are subjected to change year after year, the successful tenderer may try to backout after one year’s work or ask for enhanced rates. So it is desirable to call for tenders on year-to-year basis for cable laying work. In rural areas where close supervision is difficult, contractors may try to maintain insufficient depth for trench and avoid using warning layer. In semi urban and other developed cities, it is advisable to engage more men for laying so that the entire operation progresses quickly and gets completed with barest minimum inconvenience to shopkeepers and general public Unlike other civil construction works, tender conditions for carrying out cable laying works should take into account all these important aspects and give more stress on precautions to be taken while laying, as any defective practice will lead to network instability at a later date.

3.3.2 Some Common Wrong Practices and Their Remedies.

Some of the wrong practices often noticed in laying cables on public roads by contractors are enumerated in the following paragraphs, which can be rectified as suggested.

3.3.3. Crossing Water Pipes.

Wherever water pipes exist at insufficient depths and the contractor lays the cable over it, it causes unequal dynamic stress on the cable by vehicular traffic , ultimately developing a sheath crack and consequential failure of circuits. In such cases, the contractor should get specific instructions from the Construction Officer and lay the telecom cable through GI pipe further below the level of water pipe with a soft earth cushioning between water pipe and cable terrains may preferably be made using

water blocking powder on the upstream side and protect the ends of cables by using insulation tapes during laying.

The following diagrams in the next page illustrate better about the laying across water pipe lines and culverts.

CROSS- SECTION OF ROAD SHOWING TELECOM CABLE LAID

OVER WATER PIPE WITHOUT CLEARANCE AND SUBJECTED TO EXCESSIVE DYNAMIC LOADS FIGURE-2

3.3.4 Crossing Culverts

While laying cables across a culvert, the usual practice followed is by using GI pipes cut at the ends in V- shape on the outer surface and bend downwards so as to lead in the cable from end to the trench. This apart from weakening the strength of GI pipes, damages the outer sheath of cable due to abrasion. Moreover, the pipe itself is broken at this weak spot whenever any vehicle runs over it. The V-cut also reduces the inner volume of the pipe. making it difficult to draw further cables through it. the cut portion allows mud to enter the pipe and clog the inner space during heavy monsoon and in course of time renders the pipe unfit for further drawl of cables. The use of 45^o bends of the same size as that of the pipe at the ends with necessary couplings and sealing at both ends using plaster of Paris or light cement mortar mix, after all cables are drawn through the pipe, is found to be an advantageous method. A typical arrangement is shown in figure 3 Where the pipe could not be taken close to the wheel guard of the culvert or below it, the pipe may be enclosed inside the parapet wall by dismantling and reconstructing it with the specific approval of the PWD.

Sealing the ends of pipes in both the above cases is an important precaution to avoid accumulation of mud and prevention of entry of harmful rodents, rats etc. Where the culverts are not provided with parapet walls, it is preferable to enclose the GI pipe along with cable in cement concrete through the length of culvert as shown in Figure 4 Care should be taken to draw further cables in the same pipes where sufficient space is available and finally seal the mouths so as to avoid wastage of pipes.

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TYPICAL METHOD OF LAYING CABLE THROUGH PIPE OVER CULVERTS USING 45^oBENDS FIGURE 3

3.3.5 Crossing 11KV Electric Cables

Instances we may come across where 11KV electric cables exist in parallel or across a proposed Telecom cable route. In respect of parallelism, it is advisable to take the telecom cable with maximum horizontal clearance as far as practicable but not less than 0.6 meters, so that the intensity of inductive interference can be minimized.

Absence of sheath continuity and armour continuity in Telecom cable and it’s improper earthing in the vicinity of power cable will result in AC induction and consequent impairment of the telecom circuits. When the power parallelism is more than 0.8 kms the cable route should be referred to Power Telecom Co-ordination Committee (PTCC) for recommendation of protection measures. In case of crossings, care should be taken see that telecom cable crosses at right angles and at a vertical clearance preferably of 0.6 meters but not less than 0.3 meters at any point. When the specified clearances cannot be maintained, it is preferable to lay the telecom cable through cement concrete pipes for a length of 1 meter on either side of power cable at the crossing and seal the mouths at both ends. Electricity authorities should also be requested to lay the electric cable at crossing location in solid or through cement concrete pipe. Conventionally telecom cables are laid only on one side of the road and preferably on thru route through which telephone alignment runs. However if a 11 KV cable exists in any route, Electricity Board Authorities should be consulted and correct location of the electric cable, crossing location etc are to ascertained, before starting telecom cable laying work. Figure 5 shows a practical arrangement of telecom cable crossing an electric cable.

LAYING CABLE THROUGH GI PIPES EMBEDDED IN PCC ACROSS CULTVERTS HAVING NO PARAPETS FIGURE 4

4.0 JOINTING ACTIVITY

It is very important to follow standard construction practices and good workmanship in cable construction work. This important task is vested with the DOT staff who are given necessary training in conductor jointing, splice closure technique earthing protection, mechanical protection to joints etc.

Any physical cable pair can be jointed in a haphazard way in a number of through joints and made available at the distant end for working a circuit. This non standard practice not only causes difficulties to the maintenance staff in tracing the circuits at the time of faults, but also impairs the performance quality of the network, It is therefore necessary to follow standard construction practices only. Transmission properties could be maintained at a satisfactory level only when the conductor jointing is done in perfect 1:1 order. This means all pairs in layers should be jointed to the corresponding pairs in the other bit of cable in the same layer. Thus the correct pair jointing in through/ branch joints and in CT boxes and DPs forms a homogeneous medium for building up a satisfactory communication network.

Unlike paper cored cables, polythene insulated conductors in the Jelly Filled ( JE) cables pose no problem, since the color of conductor insulation in polythene insulated conductors does not fade in course of time and identification of tip and ring conductors is easy. Making the joints hastily or without taking proper care should be avoided. Close supervision at every stage of cable construction activities is therefore necessary. Joints should not be allowed to be closed unless all cable pairs and sheath continuity are tested.

Some cable splicers may have a wrong notion that water does not affect the JF cable and therefore they sometimes make joints in rains, keep the end of cable in water till joints are made etc. Experience has shown that water trapped inside joints flows through the crevices of the cable core and gets collected in the lower most joint.

Even through UY-connectors and splice - modules are theoretically supposed to be watertight, instances have been noticed where water trapped inside a joints finds it’s way into the splice modules and UY-connectors and cause low insulation faults. This is observed to be due to the fact that jelly filling inside some cables is not viscous in nature but crystalline, which allows water to travel through the core of the cable,

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method. Therefore joints in JF cables in the sloppy terrains may preferably be made using water blocking powder on the upstream side and protect the ends of cables by using insulation tapes during laying.

4.1 Necessity of Using Proper Tools and Implements.

Due to adoption of newer technologies in cable jointing, cable splicers are required to use different and entirely new tools. It is necessary to make them realize that the tools must be used for the purpose for which it is meant. Splicing staff must refrain from using ordinary blowlamp in place of low heat modified blowlamp. They should use only flat face crimping pliers for connecting polythene-insulated conductors in UY- connectors instead of using ordinary pliers. There are imported as well as indigenous type LSA PLUS Krone connecting tools for use in Krone type CTBs and Dps. Such connectors should be exclusively used for those works only

4.2 Precautions to be taken during Jointing of a Cable.

The following points require careful attention when joints are made.

I. Do not hesitate to use a tent or tarpaulin to protect joint and splicing staff from Sun and rain. This will not only reduce the fatigue of workers but also will protect the cable joints from possible entry of moisture and dust.

II. Keep the cable on raised platform while joints are made, so that cable splicer is able to operate correct pair and layer conveniently.

III. Keep all tools and hands of splicing staff clean before starting jointing operation.

IV. Clean the ends of cables using abrading cloth and cleaning liquid before fixing XAGA.

V. When doing branch joints, take care to fix branch off clip properly and take extra care in shrinking the portion where branch off clip is fixed so as to avoid any gap through which water may enter.

VI. Remember tying the identification tags or collars on each and every cable at frequent intervals near joints.

VII. Do not operate all cables to trace a fault in a cable without referring to records or proper investigation and identification of faulty cable.

VIII. Ensure keeping finished joints on joint stands inside the duct manholes so that the joints are not subjected to tensile stress.

IX. Ensure using exhaust fan and proper light inside duct manhole while joints are made.

6.0 CONCLUSION :

A reliable subscriber network is a basic requirement of any telecommunication installation. Taking into consideration the huge investment in the external plant, underground telecom cables used should be made less vulnerable to catastrophic faults. This could be achieved by adopting careful planning and construction practices and the impetus given on sanctioning sufficient field staff for patrolling, supervision of cable laying works, jointing operation, annual fault clearance checks etc. The success of introduction of any new technology switching systems largely

depends on the reliable and efficient cable network. With reliable external plant DOT will be in a position to meet the challenges of Global information Revolution.