Expandable rings raise manholesto gradeProblemThe City of Winston-Salem, N.C., annually raises about 100 manholes to grade. “The risers were somewhat difficult to install because they had setscrews, didn’t seat well, and the lids sometimes rattled and popped out,” says streets supervisor Larry Cauthen. “We needed a product that would reduce our materials, time and labor.”SolutionThe city purchased turnbuckle manhole rings from American Highway Products. The installer sets the galvanized steel ring into the manhole rim, then uses a screwdriver to turn the pivoted turnbuckle plus or minus 0.5 inches. A 60-pound force exerts a 5,600-pound tangential force, locking the ring
