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Pipe Welding Procedures
Second Edition
by Hoobasar Rampaul
Contents
Forward iv
Preface v
- Introduction 1
- Essentials of Shielded Metal-Arc Welding Technology 10
- Heat Input and Distribution 14
- Reparation of the Pipe Joint 21
- Uphill Welding the Root Bead on Heavy-WallPipe
(5GPosition) 31 - Welding the Rood Bead by the Gas Tungsten Arc
Welding Process 57 - The Intermediate and Cover Passes 81
- Welding Thin-Wall Pipe 100
- Horizontal Pipe Welding (20) 136
- Welding Complicated Pipe Joints 158
- Introduction to Welding Metallurgy 170
- Distortion in Pipe Welding 198
- Pipe Welding Defects 207
- Fitting-UP Pipe 222
- Qualification of the Welding Procedure & the Welder 237
I6.General Welding Safety
Index
Alignment, perpendicular pipe 235. 236
vertical pipe, 234, 235
Alloying elemenls in steel, 185- J88
boron, 188
carbon, 186
chromium, 187
cobalt, 188
manganese. 186
molybdenum, 187
nickel, 187
silicon, 186, 187
titanium, 188
tungsten, 188
vanadium, 187
Aluminum as a deoxidizer in steel, 188
“Amperage,” 10
Arc length, 12, 13
Arc strike cracking, 207, 208
Austenite, 180
Bainite, 180, 181
Base metal – Hiler metal combinations, 75-77
Bend tests, 240-242
Boron as an alloying element in steel. 188
Brittleness, (def.) 174
Carbon as an alloying element in steel, 186
Cementite, [77,178
Chromium as an alloying element in steel, 187
Cleaning the joint surfaces, 23
Coating, electrode. 12
Cobalt as an alloying element in steel. 188
Codes and standards, 8, 9
Complicated pipe joints, full lateral joint in,162-165
intennediate and cover passes in, 160, 161
rool beads in, 158-160
special precautions ill welding, 168
T-joint with intersection at side, 166, 167
T-joint with intersection on bottom, 166
T-joint with intersection On top, 165
welding, 158·169
V-joint, 167
Copper added to steel, 188
Cover passes, in horizontal pipe welding, 148, 149
in mUltilayer welding, 91-93
in Otin·wall pipe welding, 122-23
in welding complicated pipe joints, 160, 161
Cracking, arc strike, 207, 208
restraint, 52, 209·211
underbead 208, 209
Cryogenic services, 156, 157
Current flow. 10
Current setting in multilayer welding, 84-86
Defects in pipe welding, 207-221
Index
Distortion in pipe welding, 198·206
preventing, 206
Distortion in welds, 193- J97
Downhill pipe welding, 3-7
of thin·wall pipe, 102·106
heavy wall and large diameter, 126·128
DUClility, (def.) 174
Electric arc welding, basic concepts of, 10, II
Electrode coating, 12
Electrodes for GTAW process, 62,63
Electrodes for multilayer welding, low-hydrogen, 93, 94
Elements in steel, alloying, 185·188
Fatigue, 174
Faults and their prevention in welding, 211-216
Ferrite, 177
Fifth, sixth, and seventh passes
pipe welding. 148, 149
Fittmgs, pipe, 224
Fitting-up pipe, 23, 24, 222-236
Fit-up, pipe-to-pipe. 224-226
poor, 45-49
Flanges to pipe, welding, 226-230
Flat welding the root bead, 4041
45-degree elbows to pipe, welding, 231-233
Full lateral joint in welding complicated
pipe joints, 162-165
Gas cylinders, safe handling of, 233, 234
Gas tungsten arc welding (GTAW), 57-58
welding the root bead by, 57·80
Grain size, 182·184
Grain structure, 175-177
GTAW, equipment for, 59-63
shielding gas for, 59, 61
torch for, 62
welding machine for. 59
GTAW process,
f;aution, 74, 80
cover passes, 132-135
depositing root bead, 128-129
downhill pipe welding, 126-128
electrodes for, 62, 63
features of, 57
filler passes, 129-132
Heavy-wall pipe welding. 126-135
making a tie-in in, 74, 75
preparation of the weld joint in, 65
procedure for welding the root bead in, 65-70
pulse current, 72-74
rool bead, 72·80
second pass in, 72
shielding the weld metal in, 63·65
stop and restart in, 70, 71
247Index
Handling of gas cylinders, safe, 244
Hardenability, 173
Hardness. (def.) 114
Heat distribution, 14, 15·20
Heat input, 14, 15
Heat withdrawal from weld zone, I5
High temperature services, alloy steel in, I54-156
Horizontal pipe welding, 8, 136-157
coverp~esin, 148. 149
fi fih, sixth, and seventh passes in, 148, 149
making a tie-in in, 14 I
of the root bead, 137-14Q
ofthin·wall pipe, 104
poor fit·up in, 141·143
second pass in, 144·146
stop and restart in, 140
third and fourth passes in, 146-148
using low·hydrogen electrodes, 143
Hot pass in thin-wall pipe welding, 115-119
1nelusions of slag, 212·214
Incomplete penetration, 216
inspecting the weld in uphill welding the rootbead,
44-52
intermediate and cover passes, in welding
complicated pipe joints, 160, 161
on heavy-wall pipe, 81·99
intermediate passes, in multilayer welding, 86-89
in thin-wall pipe welding, 119·122
iron-carbon diagram, 181,182
Keyhole, 27, 28
in uphill welding the root bead, 33, 34
Lack of fusion, 216
Large diameter pipe welding, 126-135
depositing root bead, 128-129
downhill pipe welding, 126-128
Lead added to steel, 188
Low temperature serv ice, 156, I57
Malleability, 174
Manganese as an alloying element in steel, 186
Martensite, 179
Metallurgy, welding, 170-197
Metals, properties of. I 70-174
size changes in, 184, 185
Metal transfer, 11, 12
Molybdenum as an allOying element steel, 187
Multilayer welding, 81·82
current setting in, 84-85
intermediate passes in, 86-89
low-hydrogen eleclfodes for, 93, 94
stop and restart in, 89-91
the cover pass in, 91-93
tie-in in, 91
Multiple layers, 81-82
Nickel as an alloying element in steel, 187
9O-degree elbows to pipe, welding, 230, 231
OXYllC\:tyJene welding, safety regulations for,
245,246
Pearlite, 178
Perfect weld requirements, 239, 240
Phosphorus in steel, 188
Pipe fittings, 224
Pipeline welding, outdoor, 104, 105
Pipe parts to pipe, welding, 226-236
Pipe-IO-pipe fit-up, 224·226
Poor fit·up, in horizontal pipe welding, 141·143
in thin-wall pipe welding, 124
narrow root opening, 48, 49
root face 100 thin, 49
root face too wide, 49
wide and narrow rool openings, 48, 49
wide root openingI 4548
Porosity, 215, 216
Positions for pipe welding, basic, 1,2
Precautions in welding complicated pipe joints, 168
Preparation of the pipe joint, 21-30
Preparation of the rool bead in multilayer
welding, 82-84
Preparation oflhe weldjoinl in GTAW pro-cess, 65
Preparing pipe edges, 21·23
Preventing distorticm in pipe welding, 206
Prevention of welding faults, 211·216
Procedures, bask pipe welding, 3-8
for fitting-up pipe, 222
qualifYing, 237
Properties ofmetals, 170-1 74
Pulse current, root bead, 72-74
Qualification of the welding procedure and
the welder, 237·242
Relieving of stresses, 188, 189
Requirements for a perfect weld, 239, 240
Residual stresses and distortion in welds, 193-197
Restart in uphill welding the rool bead, 37, 38
Restraint cracking, 52, 209-211
Rool bead, flat welding the, 40-41
in complicated pipe joints, 158·160
in uphill welding on heavy-wall pipe, 31-34
vertical uphill welding of the, 38·39
Root bead, GTAW process, 72·80
pulse current, 72-74
Root bead in multilayer welding, prepara-tion of
the, 82·84
Root bead in uphill welding, starting the. 34-36
Root bead welding, summary of, 52-56
thin-wall pipe, 103·108
with low-hydrogen electrodes, 49-52
248Index
Safe handling of gas cylinders, 244
Safety, general welding, 243-246
Safely regulations for oxyacetylene welding, 245,246
Second half of the pipe joint, welding the, 41
Second pass in horizontal pipe welding, 144-146
Shear stress, 172
Shielded metal·arc welding. 10-13
electrode, 94-99
Shielding gas for GTAW process, 59, 61
Shielding the weld metal in GTAW process, 63-65
Silicon as an alloying element in steel, 186, 187
Size changes in metals, 184, 185
Slag inclusions, 212-214
Spheroidite, 180
Standards and codes, 8, 9
Standard symbols designating welding posi-lions, 2
Starting the root bead in uphill welding,34·36
Steel, structural characteristics ot: 177-181
Stop and restart, in GTAW process, 70, 71
in hori7,Ontai pipe welding, 128, 129
in multilayer welding, 89-91
in thin-wall pipe welding, 114·115
in uphill welding the root bead, 37, 38
Stopping the weld, 28-30
Strain, (def.) 172
Strength, 172, 173
ultimate tensile, 173
yield, (def.) 173
Stress, (def) 17I, 172
shear, 172
torsional, 172
Stresses and distortions in welds, residual, 193-197
Stress relieving, 188, 189
Structural characteristics of steel, 177-181
Structure of the weld, 189-193
Structure sleel 78, 79
Sulfur added to steel, 188
Symbols designating welding positions, 2
Tack welding, 25-27
thin-wall pipe, 106-110
Tees to pipe, welding, 234
Tensile strength, ultimate, 173
Tests, bend, 229-231
Thin-wall pipe welding, 100-135
cover pass in, 122·123
downhill, 102·106
horizontal, 104
pass in, 115, II 6 joint tor, 105,106
Thin-wall pipe welding, intermediate passes in,
119-122
poor fit·up in, 124
preparation for the hot pass in, 115, 116
preparation of the pipe joint for, 105, 106
stop and restart in, 1114, 115
tack welding, 106-110
tie-ins in, 115
uphill, 100, !OI
welding the root bead in, 110·114
with pipe axis at 45-degree POSilion,124-125
Third and fourth passes in horizontal pipewelding,
146-148
Tie-in, in GTAW process, 72
in horizontal pipe welding, 141
in multilayer welding, 91
in thin-wall pipe welding, 115
procedure, 41-44
TIG (tungsten inert gas) welding, 57-58
Titanium as an alloying elemen! in sleel, 188
T-joint, in welding complicated pipe joinIs, 164-167
with intersection at side in welding com-plicated
pipejoinls, 166,167
wilh intersection on top in welding com-plicated
pipejoints, 165
Tools required for fitting-up pipe, 209-2 II
Torch for GTAW process, 62
Torsional stress, 172
Toughness, (def.) 174
Tungsten as an alloying element in steel, 188
Ultimate tensile strength, 173
Underbead cracking, 208, 209
Undercutting, 211,212
Uphill pipe welding, 7, 8
wilh pipes in an angular (6G) position, 161,162
Uphill welding the root bead, 36-38
keyhole in, 34
on heavy-wall pipe (50 position), 31-48
vertical, 38-39
UphHl welding thin-wall pipe, 100, 101
Vanadium as an alloying element in steel, 187
Venical uphill Welding of the root bead, 38·39
Voltage, 10
“Weaving,” 20
Weld-affected zone, 190-193
Weld repair, 217-221
“Whipping.” 20, 28
“Whipping and pllllSe,” 39
Widmanstatten structure, 179
Withdrawing heat from weld zOne, 15
Yield strength, (def.) 173
V-joint in welding complicated pipe joints
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