Robvon Backing Rings are inserted into the beveled pipe end with the spacer nubs flush against the pipe land and the ring gap positioned in the area of first bead deposition. The beveled end of the adjoining pipe is slipped onto the Robvon backing ring until the edge of the pipe land is firmly abutted against the spacer nub. Depending upon the Ring Style chosen, the welder has the choice of "striking off" the nubs or leaving them intact.
The welder can either weld the split making a solid ring or weld away from the split allowing the heat of the molten metal to expand the ring forcing it tightly against the inner surface of the pipe. This eliminates gaps, openings, or crevices between the Backing Ring and the pipe, tube, valve or fitting. Robvon engineered flat outer surfaces afford immediate access to the root of the weld and allow complete penetration. The 1/16" lands on the outer ring edges prevent curling. The internal bevels and flat inner land minimize flow turbulence on the downstream side to a nearly incalculable degree.
During welding, the arc should be directed as to penetrate the Robvon backing ring and inner edges of the pipe or fitting. The molten metal should penetrate into the Robvon Backing Ring approximately forty to fifty percent of the cross-sectional dimension thereby forming an integral welded joint.
STARTS AND STOPS OF THE WELD DEPOSIT AT THE "CC" LOCATIONS SHOULD BE AVOIDED IN THE ROOT PASS.