Tension clamps for OPGW

Hardware& Accessories for Optical Fibre Aerial Cables

Metal-armored (OPGW, OPPW) aerial cables with integrated optical fibers are used to transmit information .The information is transmitted by means of modulated light pulses in the interior of the thin optical fibers. These fibers have a total diameter of approx. 300 µm. Such cables can be stressed up to a limited tensile force without any increase of the optical signal damping in the fibers. However, in the case of a radial force, the optical damping will increase by bounds. This increase can lead to a reduction of the information flow through the fibers.

The fibers with an additional length are in one or several relatively rigid coaxial tubes to avoid inadmissible stress. The core(tube) of the aerial cable is covered with one or more layers of aluminium alloy wires or Aluminium-clad steel wires.

As the optical fibres have to be protected against inadmissible radial forces during and after the installation of optical fibre aerial cables the fittings at the tension-, suspension- and fixing points have to meet special requirements.

The common fittings for tension and suspension points which provoke the necessary griping force by effecting of a high radial force (for example wedge type tension clamp, suspension clamp). Due to the high pressure sensitivity of optical

fibers , these types of fittings are not suitable for optical fibre aerial cables.

The preformed helical fittings are designed which are especially adapted to this purpose. The induced radial forces are spread over a larger contact surface (for example dead end) in such way that the fibers are not stressed and the necessary griping forces are achieved.

Fittings for optical fibre aerial cables mainly consist of the following group of fittings:

- Preformed Helical fittings for tension and suspension points

- Earth connections

- Tower down-lead accessories

- Vibration dampers

The principle of operation of preformed helical accessories is based on the principle of the development of a low pressure over a large area. The inside diameter of the unloaded helical rods is slightly smaller than the outside diameter of the optical fibre aerial cable By wrapping the helical rods on optical fibre aerial cable, a spring tension is created, producing the necessary

frictional contact. This spring tension is elastic and ensures a constant grip.

To ensure the full performance, helical formed accessories must exactly be adapted to the outside diameter of optical fibre aerial cable .

We, Key Link will give you a good solution and performance .

Tension assembly for OPGW

• Product introduction

The preformed helical dead ends are suited for the full tension of self supporting optical fibre aerial cables(OPGW cable) .It’s composed of proper pre-assembled helical rods which are covered with a small-grained sand on the inside to improve the frictional contact. The stranded loop of the dead end is protected from abrasion by means of a thimble. The deformation of the cable is omitted as the radial compression is distributed over a large contact area

These preformed helical dead ends are applied to pull OPGW on top of terminal tower, tension tower, splice tower and tower of angle greater than 25°.

The protecting inner helical rods for tension sets are mounted beneath the helical tension clamp and spread the radial forces on the cable uniformly along the zone of contact.

Especially on the cable at the loop-side of the helical dead end radial forces (depending on the tension force) can stress the optical part of the cable. This will cause high damping which results in a reduced data transmission or in the worst case an interruption.

For optical fibre aerial cables with right-hand outer layer, the protection helical rods with left-hand layer are always used in order to avoid a torsion of the cable by the helical dead end with right-hand layer. A torsion of the aerial cable is causing an elongation or stretching leading to a destruction of the optical part of the cable.

The type is designed and defined according to the cable diameter and tensile requirements

Whole set of tension assembly includes : inner layer-protection helical rods ,outer layer -tension preformed helical rods; one set of thimble; one set earthing wire and clevis ,shackles etc. will be supplied as requirement.

• Product specification

1. Inner protection helical rods: Aluminum-clad steel with particulate grit applied to increase friction.

2. Outer tension preformed helical rods: Aluminum-clad steel with a small-grained sand on the inside and the individual rod assembled into groups to increase the griping strength of tension clamp, and the loop section is stranded to increase the loading strength.

3. Thimble clevis: Steel ,Hot dip galvanized .

4. Earthing wire: AAC cable , with aluminum alloy plug pressed on , one set parallel groove clamp , and one set bolt assembly

5. Connecting fittings : clevis,shackles or extension link etc. : all hot dip galvanized.

• The respective letters or figures have the following meaning:

O: OPGW cable;

N: Tension clamp

Y: Preformed type

First 4 figures group : largest possible cable diameter for which the accessory is suitable (measurement: 0.01mm)

Last 3 figures group : Rated tensile strength of whole assembly set for which the accessory is suitable(measurement: KN)

1.1 Application cope :Rated tensile strength 70KN

1.2 Application cope :Rated tensile strength 100KN

1.3 Application cope :Rated tensile strength 120KN

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