While selecting the hardware for OPGW, we may keep in mind that the hardware or fittings will not cause any degradation of the optical transmission properties of the fibers of OPGW during service. The concern is that while fitting or assembling with the OPGW cable the hardware should not restrict the optical fibers from moving freely inside the metallic or plastic tube.
There are four main hardware items for OPGW installation. They are Tension Assembly, Suspension assembly, Vibration dampers, and Attachment clamps. Let us see the functions of each item.
The tension assembly consists of a line guard and a pre-formed dead end which is placed on the line guard. The line guard is laid in the opposite direction of the outer layer of the OPGW cable and the dead-end is laid in the opposite direction of the line guard. The length of the line is designed to suit the vibration dampers. The line guard protects the OPGW against the radial forces in the area of contact between the dead end and the OPGW. All helical rods are made of Aluminum clad steel material.
The assembly is free to swing to ensure that the clevis stays in line with the OPGW when the OPGW approaches the tower at any horizontal angle within +/- 30 degree angle from the longitudinal direction of the transmission line and at any vertical angle between the horizontal and 20 degrees below the horizontal.
Armor grip suspensions are used at suspension points. The clamp body of the suspension assembly is made of a forged aluminum alloy. The material of the rod is aluminum alloy. The suspension assembly clamp and its hanger are able to swing freely in both the longitudinal and transverse directions up to a 70 degree angle with the vertical.
Generally, installation contractors conduct a survey and study based on the self damping measurements of OPGW cable, span length distribution, the height of OPGW above ground level, wind velocities, temperature, design tension limits, and topology. They will calculate and decide the number, location, and type of vibration dampers according to the span sizes.
The ferrous components of the vibration dampers of OPGW are protected with a zinc coating which is according to ASTM A153 and ASTM A239. The damper clamp is designed to avoid the accumulation of moisture at any point on the damper. A drain hole is provided for dampers. Breakaway bolts are also provided for the dampers.
Attachment clamps that hold the OPGW to the tower splicing points are made of hot-dip galvanized steel.
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