From Lineman's and Cableman's Handbook, Eleventh Edition

Sagging operations begin as soon as the conductor stringing is completed, to establish the proper conductor tension for the conditions at the time the work is performed. The correct conductor tension and sag for various sag or control spans are detailed in the construction specifications or standards to provide proper clearances. The weather conditions, including temperature and wind velocity, must be taken into consideration to complete the process. The proper conductor tension can be obtained by establishing the proper sag in the control spans. Sighting methods using a surveyor's transit or targets can be used to measure the sag in the conductor. The tension in the conductor can be measured with a dynamometer or determined by timing mechanical waves induced into the conductor.

All conductor grips, come-alongs, stringing blocks, and pulley wheels used in the sagging operations must be of a design which will not damage the conductors by kinking, scouring, or unduly bending them. Sag sections must be selected before the operations are started. The lengths of sag sections are limited by dead-ends, angle structures, and the terrain. The sag sections are normally not longer than 4 miles.

Sag sections must have control spans. The control spans will be used to measure the sag for each sag section. If the control spans are properly sagged, the conductors in the sag section should all be at the proper tension. The control spans should be approximately the length of the ruling span. Ruling spans are a calculated dead-end span length assumed...


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Spherometers are used to measure the radius or curvature of spherical surfaces such as optical lenses, spherical mirrors, and balls.

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