Pole Line, Span Wire and Mast Arm Installation
Erection and attachment
Pole line work covers pole erection, plumb, anchor-bolt torque, mast arms, span wire, messenger, clamps, insulators, and signal-head attachment. Poles must be plumb within tolerance, anchor bolts torqued to the shop drawing, and leveling nuts grouted. Mast arms must be level and oriented so heads hang over the correct lanes. Span wire systems use a messenger tensioned to a sag or tension value at the installation temperature; signal heads hang vertical from clamps.
Clearance and safety
MUTCD requires overhead signal faces high enough for clearance, commonly at least 15 ft above the roadway; verify the agency standard. NESC and local utility rules govern clearances to power lines. Use safety chains, thimbles, dead-end grips, and listed clamps. Do not stand under a suspended load.
Worked example: A span wire is tensioned on a cold morning without a dynamometer. In summer, thermal expansion reduces tension and the heads sag; the bottom of a head may drop below the required clearance or hang visibly tilted. The correct method is to use the specified tension or sag at the measured conductor temperature and record it. If the wire was over-tensioned cold, inspect clamps and anchors for damage before adjusting. The reasoning is that tension and sag are temperature-dependent, so a value without a temperature record cannot be verified.
Traps: over-torquing anchor bolts; no anti-seize; arm not level; span clamps installed backward; missing safety chain; insufficient clearance; no tension record.