Machine Design

Heat-indicating markers verify metal preheats

Tempil Inc.

Technicians and welders from High Steel Structures Inc., Lancaster, Pa., wanted to ensure the welds on the Woodrow Wilson Bridge were done right. The bridge, which replaces an outdated drawbridge, will carry six lanes of traffic, plus shoulders, for more than a mile and at least 70 ft above the Potomac River.

Preheating the metal was one of the critical steps in making proper welds on the bridge, some of which stretch for 120 ft. And on-site DOT inspectors can be sticklers for accuracy and proper procedure.

To verify the preheat temperate and ensure metals are properly prepared, High Steel welders use surface-temperature measurements tools from Tempil, South Plainfield, N.…J. The Tempilstick, a crayonlike waxy stick, can be used to mark metal. Each stick is rated with a specific temperature. Tempilstick markings heated to that point permanently change color. Welders on the bridge use sticks rated 1 through 12, corresponding to 100 through 1,200°F, a common range for heating and straightening steel girders. Each stick is accurate to within ±1°. DOT inspectors readily accept a Tempilstik mark that has changed color as verification that the girder was properly preheated before welding began.

© 2012 Penton Media, Inc.

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