Tweco 95 S Thermal Arc(Nov2010) - Manual (Page 38)

THERMAL ARC 95 S OPERATION
Manual 0-5175 4-10 Operation
E. Preheating
Suitable preheating of parts of the structure other than
the area to be welded can be sometimes used to reduce
distortion. Figure 4-23 shows a simple application. By
removing the heating source from b and c as soon as
welding is completed, the sections b and c will contract
at a similar rate, thus reducing distortion.
Art # A-07707
Figure 4-22: Principle of presetting
Art # A-07708
B
Preheat Preheat
Dotted lines show effect if no preheat is used
Weld
C
Figure 4-23: Reduction of distortion by preheating
Art # A-07709
Figure 4-24: Examples of distortion
Art # A-07710
Figure 4-25: Welding sequence
Art # A-07711
Figure 4-26: Step back sequence
Art # A-07712
Figure 4-27: Chain intermittent welding
Art # A-07713
Figure 4-28: Staggered intermittent welding