Page 83 - Pipeline Rules of Thumb Handbook

70 Pipeline Rules of Thumb Handbook

Table 1
Criteria for selecting an appropriate repair method (X indicates an acceptable repair)

Type of defect
Manufacturing defect
Environmentally caused defect in ERW or FW
In seam weld In the body of the pipe Seam weld in body, SAW seam or girth weld

ERW and FW
Upturned
SAW fiber Selective
Undercut, imperfection, Hard spot corrosion,
Incomplete Incomplete Lap, Pit, exceeding Hydrogen Hydrogen
fusion, fusion, Seam, R c > 35 stress stress
Incomplete Penetrator, Crack and 2 in. cracking Stress- cracking
penetration, Cold weld, Rolled-in in extent in weld General Pitting corrosion in hard
Repair method Crack Crack Slug or more zone corrosion corrosion cracking spot

Nonleaking O.D. defect (a)
Type A sleeve No filler X ...... X ...... ...... X X X ......
Type A sleeve With filler ...... ...... ...... X (g) ...... X X ...... X
Type B sleeve No filler X ...... X ...... ...... X X X ......
Type B sleeve With filler ...... ...... ...... X ...... X X ...... X
Type B sleeve pressurized X (b) X (b) X (b) X (b) X (b) X (b) X (b) X (b) X (b)
Deposited weld metal (h) X (c) ...... X (c) ...... ..... ...... X (c) ...... ......
Removal X X X X X X X X X
Removal by hot tap ...... ...... X (e) X (e) ...... ...... X (e) ...... X (e)
Nonleaking interior or I.D. defect (a)
Type A sleeve No filler X ...... X ...... ...... X X ...... ......
Type B sleeve No filler X ...... X X ...... X X ...... X
Type B sleeve pressurized X (b) X (b) X (b) X (b) X (b) X (b) X (b) ...... X (b)
Removal X X X X X X X ...... X
Leaking defects
Type B sleeve pressurized X X X X X X X X X
Removal X X X X X X X X X

(a)
Corrosion or other defect which is known to exceed 80 percent of the wall thickness in depth should be treated as though it were a leak.
(b) Pressurization to be accomplished upon completion of repair by drilling hole through carrier pipe through a small tapping nipple.
(c) Only for undercut, laps, and pits where the defect can be safely enlarged to a weldable groove and subject to remaining wall thickness rules.
(e) Only if branch coupon entirely contains and removes defect.
(f) Only with humped sleeve or if flat sleeve is used, girth weld must be ground flush. Do not use if extreme high-low condition exists.

usually innocuous unless they are quite large*—2 percent or deposited weld metal. Gouges-in-dents may be repaired only
more of the diameter—or unless they involve a seam or girth by means which prevent outward movement of the dent.
weld. When the dent is large or welds are included in the dent Sleeves without fillers are not acceptable.
or gouge-in-dent, the repair should prevent its outward move- When dents are involved, hot-tapping is not recommended
ment. Sleeves with fillers or pressurized sleeves are required. since it may not remove the dent entirely. For any gouge or
If the included weld is an ERW or FW seam, the defect gouge-in-dent, repair by deposited weld metal is not recom-
should be removed or the stress relieved with a pressurized mended since concealed cracks may exist. When a dent is
sleeve. present, weld metal may not have sufficient ductility to with-
Gouges without dents in the body of the pipe or in SAW stand the severe strains that accompany outward dent
seams or girth welds may be repaired by any means except movement.
Construction defects in girth weld include undercut,
incomplete fusion, incomplete penetration, and cracks.
Deposited weld metal may be one of the best ways to repair
* Present requirements of federal regulations Part 192 dictate removal of undercut or other externally connected defects in girth welds
dents extending over 2 percent of the pipe diameter. which can be ground for access. Sleeves, if used, should have