18
Welding gun
Component
Fault symptom
Cause
Type
Welding gun overheats
Welding gun underrated for
welding application
Liners
Erratic wire feed, wire snarls up at
outlet guide
Liner of incorrect type and size
for wire in use, worn or dirty liner,
liner too long or too short
Gas distributor
Inadequate gas flow, contaminated
or porous weld
Damaged or blocked distributor
Nozzle
Inadequate gas cover, restricted
joint accessibility
Nozzle too large or too small,
incorrect length or shape
Contact tip
Erratic feeding, wire shudder, wire
burnback, unstable arc, spatter
Incorrect size of contact tip,
incorrect contact tip to nozzle
distance for metal transfer mode,
inferior contact tip material
Nozzle insulator
Arcing between contact tip and
nozzle and between nozzle and
workpiece
No nozzle insulator fitted
Regulator / flowmeter
Component
Fault symptom
Cause
Inlet stem
No gas flow, gas leaks at regulator
body or cylinder valve
Blocked inlet stem, leaking inlet
stem to body thread, bullnose not
properly seated in cylinder case
Gas hose and fitting
Leaks at connections or in the
hose, porosity in the weld
Poorly fitted “o” clips, damaged
hose, air drawn into gas stream
Shielding gas
Component
Fault symptom
Cause
Cylinder, MCPs
No gas flow, porosity in the weld
Gas cylinder closed or empty, faulty
cylinder valves
Bulk
No gas flow, change in welding
conditions
Bulk tank empty, incorrectly set
mixing panel
Welding wire
Component
Fault symptom
Cause
Wire basket and spool
Erratic wire feeding or wire
stoppages
Damaged wire basket, loose
spooling, random-wound wire
Wire
Wire sticks in contact tip, erratic
feeding
Varying wire diameter, copper
flaking, surface damage
Wire
Weld has excessive amount of
spatter
Wrong polarity has been selected
