Field Welding of Ribbon Rail



Taking the last clack " out of the "clickety-clack" so familiar to railroad travelers is the job of Southern's track forces as they accelerate the program of field welding of ribbon rail.

Using a process known as Thermit welding for joining together the quarter-mile strands of ribbon rail, Southern's track forces are now eliminating all joints in rail where the ribbon rail and field-welding process is being used ( except for insulated joints at Centralized Traffic Control-CTC-signal control locations) .

Unloading quarter-mile strands of ribbon rail from one of Southern's three rail trains. A Southern-developed rail unloader feeds out two rails simultaneously, laying it on rail cradles between the rail to be taken up.


Ribbon rail (jointed rail previously taken up, shipped back to Southern's Inman Yard outside Atlanta, inspected, cropped and plant-welded into quarter-mile strands) is delivered to the field in one of Southern's three rail trains where it is unloaded by a Southern developed unloader which simultaneously feeds two strands of rail from the rail train, laying them on rail cradles inside the rail to be taken up.

Following the rail train is an assortment of specialized equipment which takes up the old rail, lays the ribbon rail in place, spikes the tie plates down and anchors the rail to the tie plates. A temporary joint bar is installed to hold the quarter-mile rail sections in position until welded. The in-field welding is done where two quarter mile strands of rail meet and where a permanent rail joint bar would have been installed in the past. For cold.weather rail laying, Southern has developed a preheater which is a self-contained machine equipped with propane heaters. The rail is pre-heated before being anchored to eliminate rail expansion in warm weather.

End and side view of special fire bricks and metal brick covers that form mold box around rail to be welded.


To prepare the rail ends for welding, a small section of rail measuring approximately 15/16-inch is cut off the end of one rail using a cutting torch. Both rail ends are cleaned. The two rails to be welded are then aligned on the top and sides of the ball of the rail, and the gap between the rail ends is checked with a gauge for accurate spacing.

A metal framework is then attached to the rails which will hold a heating torch, a crucible containing molten metal and clamps for clamping in the mold box in place around the area to be welded.

The mold box consists of two specially-shaped fire bricks and metal brick covers. The two halves of the fire bricks are fitted against the gap in the rail and the matched covers placed' over the bricks. All is held in place by clamps. The outside edges of the mold box are packed with a sand and fire clay mixture around all sides to prevent leakage of the molten metal from the mold box.

Mold box installed on rail and clamped in place. Edges of mold box are packed with a sand and fire clay mixture to prevent molten metal leaking out.


After attaching the mold box a heating torch is applied to the rail ends, heating them until they begin to flux. During the time the rail ends are heating ( approximately 11 minutes) , the crucible is mounted on the framework, filled with welding compound and an ignitor fuse is set in the compound.

A cutting torch slices out a section of a rail end where two ribbon rails are to be welded.


As soon as the flux state is reached in the rail ends, the crucible is swung around on the metal framework until it is in position over the mold box. The ignitor is lit, causing the welding compound to burn and form a molten liquid. While the welding compound is still bubbling, a plug in the bottom of the crucible is removed and the molten metal flows into the mold box around the rail.

After about five minutes setting time, the metal framework and metal brick covers are removed from the rail and the fire brick knocked off with a hammer. The excess metal around the weld is trimmed off, then ground smooth with powered grinders. The welded section is ready for traffic as soon as the ball of the rail is ground smooth.

M. L. Denton (right), process engineer, Track, and W. H. Shipp, assistant supervisor maintenance equipment, check progress of rail heating. Crucible at right contains welding compound to be ignited.


While Thermit welding is not new, the method presently used on Southern is-one that has been considerably improved and refined by the German firm that originally developed the process many years ago. Southern officers, who observed the procedures used in

'Germany, report that European railroads utilize the process much more than their American counterparts, with the German railroads making approximately 500,000, the Swiss approximately 350,000, the French 350,000 and the English 200,000 Thermit welds in track each year.

A crucible of molten metal is emptied into the mold box (overflow goes into pan on left side of rail). After metal hardens for approximately five minutes, the mold box will be removed, excess slag knocked off and the rail ground smooth.


Southern first tried out the Thermit field-welding of rail in the latter part of 1966 on portions of The Cincinnati, New Orleans & Texas Pacific. To date, 21 miles of track have now been installed using the process and it is planned that all future ribbon rail placements will utilize field-welding of the quarter-mile strands.

In addition to a smoother, quieter ride for Southern freight and passenger traffic, field-welding will reduce track maintenance by reducing the number of rail joints subject to traffic wear and tear.