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The Main Hardwares used for Installation of ADSS and OPGW Optical Cable

DATE: 2011-12-15 | SOURCE: HOPE | Click:

Principle of Cable Hardware selection

As All Dielectric Self-supporting Aerial Cable (ADSS) and Optical Fiber Composited Overhead Ground Wire (OPGW) fiber optic cable are made ​​of brittle material , so it can not put too much strain.  And fiber diameter is very small, so he 's tensile strength very weak .In choosing the cable hardware, the principle is not only to meet all the features and characteristics of the cable should be inclusive , but shall take into account the payment of grip strength with uniform , non-metallic sheath degradation , wear , vibration breeze , dancing , exceed the allowable bending stress and reverse parameters. Therefore, the general provisions is "Hardware’s squeeze should not exceed  with more than two cables design limits , hardwares should not be designed for a range of diameters ."

The Main Technical Parameters for Selection

1)Climatic conditions

Temperature(°C),The annual average temperature(°C),Relative Humidity(%),Thunderstorm days(Day),Ice thickness(mm),Wind velocity(m/s)。

2)Electrical parameters of the system

Voltage(kv),Maximum system voltage(kv), Power frequency(Hz)。

3)Cable parameters

Models, cross-sectional area(m㎡),diameter (mm), weight (kg / m); nominal damage load (KN), permissible bending radius (mm), linear expansion coefficient (/ ° C); the average annual job tension ( KN), the maximum working tension (KN).

4)Tower parameters

Tower type , model, each span (m), elevation (m).

 

The Structure and Installation of the ADSS & OPGW Cable Hardware

Let me introduce the suspension clamps below:

As the special requirements of ADSS and OPGW structure , when designed those products, it will adopt with more than 10 times of ADSS& OPGW allowed bending radius , with a damping function to reduce wear and the large curvature of the suspension clamps . The basic structure  forms include pre- twisted wire , insulation and large curvature suspension clamps three types .

1)Pre- twisted wire suspension clamps

Pre- twisted wire suspension clamp has the advantages of manufacture ​​simple, easy to install , use effective, etc.

Composed of four parts, there are preformed rod, rubber sheath , clamp body , hanging plate.

The preformed rod used the aluminium alloy materials, through the preformed rod forming drawing mold forming in advance, front end is a smooth spherical, surface no crack, burr and serious wounds, forming aperture is ADSS and OPGW outside diameter 84% ~ 85%. Single diamete 2.5 mm to φ 6.3 mm is advisable.

ADSS suspension clamp, has pre- twisted wire external and internal layers, inner diameter smaller than the outer diameter of single-1mm, length longer than the outer 20%~30%, gripping power is smaller than the outer 25%.    

Rubber sheath, with heart & bone and mindless bones two types. As the sheathed element for OPGW suspension clamps, it must have good damping properties, excellent fatigue resistance and therefore need good mechanical strength, appropriate compression stiffness, better resistance to oxidation and UV resistance, corrosion resistance, low degradation and OPGW greater starting hand grip, and starting hand grip relaxation speed (pressure decay) to be particularly slow. Only high polymer can meet these requirements, mainly with natural rubber and synthetic rubber as the main ingredient, and additive blending, reinforcing agents, plasticizer, etc, forming a multi-component synthetic rubber sheath. Because "Chloroprene rubber contains more unsaturated double bond, the ozone aging, resistance to oxidation and UV, weathering performance is poor. Design of rubber sheath thickness of 8~14mm,  it’s length wrap for pre screen intermodulation formed from the long 80% or so.

Clamp body is manufactured with high-strength aluminum alloy.

Hanging plate tensile strength not less than 372.5N/ m㎡ of steel punching, hot-dip galvanized anticorrosion.

2)Insulation type suspension clamps (also called FDS installations)

Insulation type suspension clamps supported by shell, lining, bolts, devices (hoop or pendant bolts). The shell is used high strength insulating materials, lined is with a soft, flexible material.

3)Large curvature suspension clamps

Ontology and plate thickness of contact surface on the part of the mosaic-4~6mm alloy. Aluminum alloy Board, the ontology uses, the rest of the steel products, hot-dip galvanized anticorrosion coating. Large curvature clamp trunking refers to ontology structures of curvature radius of curvature, curvature (Central slots for line segments, curves on either side) and two curvatures. Its curvature (bulk channel and plate) radius not less than diameter of OPGW 200 times and, of course, you can design a variety of different structures with large curvature suspension clamps, basic structure forms.

 

Performance comparison of 3 kinds of suspension clamps

*Pre- twisted wire suspension clamps comparison

1)Reduce the support points of inherent stress;

2)Reduce the breeze vibration caused by dynamic stress;

3)Enhanced hang point cable stiffness to avoid stress concentration, serve to protect the cable core;

4)Cable up to 60 ° angle;

5)Easy to install;

6)Higher price.

*Insulation type suspension clamps

1)Structure is simple;

2)Can sliding;

3)Easy to install;

4) Low price;

5) Restricted the scope of use (span less than 25mm, <185m, cable diameter cable point ≤ 20 °).

 

*Large curvature suspension clamps

1)Structure is simple;

2)Low price;

3)Installing the pressure plate bolt torque should be restricted;

4)Only for OPGW, ADSS should not be used.

 

Installation points and method for three type suspension clamps installation

*Pre- twisted wire suspension clamps

 1)Upon installation, cable specifications, model, corresponding to the clip you want to install the selected one by one;

 2)Check product quality;

 3)Installation method, has normal type, bar type, with the grounding on the vertex type and double overhang corner double pendant and double cable type. Installation requires pre- twisted wire evenly tightened in cable, not too large gaps between single and overlap.

 4)Cable angle 30 ° ~60 ° (horizontal angle and steering angle). Benefit is the increased stiffness, increasing the radius of curvature, guarantee that the core will not damage.

*Insulation type suspension clamps

 Hold or fasten fixed with bolts.

*Large curvature suspension clamps

Pressure plate bolt torque as designed for fastening。

 

As described above, when in selection of suspension clamps, recommended the pre- twisted wire suspension clamps, in terms of performance, quality, or on the installation convenience, is incomparable to the others. I hope the introduction above can give you some help when you choose the cable hardwares.

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