Welding

In cases where field cuts required in unrestrained sections of a pipeline necessitate the need for field fabricated restrained joints, ACIPCO offers the following procedures for fabrication of a restrained joint. When these procedures are followed by welders skilled in the art, strong, dependable restrained joints should be produced. In presenting this procedure, ACIPCO assumes no responsibility for the performance of pipe joints or pipe systems fabricated with this approach.

Welding Equipment and Materials

Welds should be applied using a D.C. arc welder and appropriate welding electrodes. Welding should be accomplished using polarity and amperage ranges recommended by the electrode manufacturer.

The weld electrodes used to deposit the required amount of fillet weld should be in conformance with Class designations AWS A5.15 (E Ni Fe Cl) or AWS A5.6 (ASME SFA 5.6) Class E Cu A1-A2. These electrodes shall be capable of producing suitable welds without preheating or post-heating of the pipe and ring. A recommended electrode, with appropriate weld specifications, is as follows: Inco Alloys International Ni-Rod 55, 3/16" diameter, D.C., reverse polarity, 135-170 amps.

Procedure Using Welding Jigs and Hand-Held Electrodes

This procedure is intended to be used for manual welding. Contact ACIPCO when semi-automatic welding setups are desirable.

STEP 1. MEASURE THE CANDIDATE PIPE DIAMETER (OR CIRCUMFERENCE) at the desired location of the cut to confirm the dimension. The allowable pipe diameter and circumference should fall in the ranges shown in Table 1. Any cut pipe with substantial out-of-roundness should be temporarily rounded with a mechanical jack and shaped timbers, then braced in the rounded shape for this field-welding procedure. The rounding timber or brace should normally be left in place inside the pipe until after complete joint assembly in the field, at which time it should be removed for service.

INT Welding Table 1

STEP 2. CUT THE PIPE AT THE DESIRED LOCATION and bevel the cut end for joint assembly. It is imperative that field cuts for restrained joint welding be smooth, regular, and as square as possible with the axis of the pipe inasmuch as the cut end is usually used as a reference plane to position the welded rings from the end of the pipe.

STEP 3. CLEAN AND GRIND THE WELD LOCATION on the pipe to bright metal prior to positioning the ring. Any coating in the weld area should be removed with a torch or with a solvent wash prior to grinding. Also, the corresponding edge of the ring to be welded should be cleaned and ground to bright metal. Loose locking rings or glands (if required for the particular joint configuration) should be placed on the pipe barrel beyond the weld ring location at this point.

STEP 4. CLAMP THE JOINT WELD RING SECURELY on the pipe in the correct location. This may be accomplished using a special welding fixture. An example of a recommended ring welding fixture available from ACIPCO is shown in Figure 2. If clamping devices not furnished by ACIPCO are utilized for the ring-clamp operation, they should be capable of holding the ring securely in the proper position and straight on the pipe until all weld is applied.

NOTE: If clamps are used, care should be taken to cushion the clamps where they bear on the inside of the pipe to minimize damage to the pipe lining. The cement linings routinely supplied by ACIPCO are normally not adversely affected by the welding procedures described in this web site. If cement lining damage occurs due to any cause, it should be patched in accordance with recommended procedures as noted in this web site. Contact ACIPCO for requirements involving field welding of pipes with special linings.

STEP 5. WELD THE RING TO THE PIPE with the final weld dimensions as shown in Table 1. Appropriate flat or "downhand" techniques for field welding ductile iron should be used. In manual electrode welding, pipe welding rotators or rolling the pipe on timbers or rails is normally necessary to keep the work flat or "downhand." For the same reason, field welding of restrained ends should generally not be done "in situ" (i.e., in the ditch, assembled), as the pipe cannot be rolled or rotated to keep the position "downhand." The use of short, overlapping weld passes will minimize heat buildup, cracking, and thermal stresses as the metal cools. Weld passes should be thoroughly cleaned (peened) and inspected before cooling and prior to the addition of the adjoining passes. Also, the ends of the adjoining passes should not coincide but should be slightly overlapped before the arc is broken. The resulting weld fillet should be of a slightly convex shape and free of significant weld defects. Weld cracks, if they occur, should be ground away and repaired with a weld overlay.

When a recommended welding fixture is utilized, start the weld at one end of the ring and work continuously and progressively to the other end.

After the entire ring has been field welded to the pipe, weld the ring ends to the pipe and weld in the small space remaining between the ring ends to ensure proper weld height at the ring ends.

STEP 6. WIRE BRUSH THE WELD AND RING to remove all slag or weld spatter. Particular care must be taken to brush or chip away any weld spatter which may have accumulated on the pipe spigot which could interfere with proper gasket sealing or joint assembly. Any significant weld bead lumps or irregularities which might interfere with proper joint assembly or performance should also be removed.

STEP 7. PAINT THE RING, WELD, AND CLEANED PIPE METAL area with a smooth uniform coat of appropriate paint or mastic which meets the requirements of the project specifications.