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4.2
Welding Process Overview
The welding process proper, after pipe butt facing and pipe align-
ment check, has the following four stages, or phases, which are also
illustrated by the time-and-pressure diagram below.
• Bead Build-up Stage – In this stage, t
are pressed against the heating element and heated to the tem-
perature of it; to ensure consistent bead formation, do this at
drag pressure (P
) plus P
t
Appendix.
• Heating Stage – In this stage, t
in contact with the heating element, soaking heat from it; the
pressure is reduced to drag pressure (P
value tables in the Appendix.
• Change-over Stage – In this stage, t
shut off from the pipes, the carriage moves apart to the far end
to allow taking the heating element out from in-between the
pipes.
• Joining and Cooling Stage – This stage is characterized by a
succession of events. First, after change-over, the pipe butts are
put together and pressure increases as a linear ramp to drag pres-
sure (P
) plus P
from the welding value table in the Appendix (t
t
5
in the diagram). Then, the joint cools down at P
pressure is completely removed from the the pipes (t
gram) or until pressure is reduced to one-third of P
into t
in the diagram); in the second case, cooling is completed
5
at the reduced pressure.
Pipe and fitting manufacturers may include data on how long
the new joint should not be exposed to external strain. Also, the
applicable welding standard may require a minimum cool-on time
after pressure shut-off (t
t
is not relevant to the welder.
6
P
P
+ P
+ P
P
P
1
1
t
t
P
P
2
2
t
t
1
1
4.3
Performing the Welding Process
To s t a r t w e l d i n g , c l a m p t h e p i p e s i n t o t h e m a c h i n e
chassis. Use the appropriate reducer inserts if the component
size is smaller than the basic machine chassis. When the fourth
clamp of the machine is removed, tees and elbows can be pro-
cessed.
4.3.1 Facing the Pipe Butts
To ensure that the pipe butts are level, insert the pipe facing tool be-
tween the machine carriages and turn it on. Using the carriage mover
lever on the hydraulic unit, have the movable carriage close in toward
the center in order to bring the pipes into contact with the facing tool.
Use the pressure regulator to adjust the pressure manually while the
facing tool is trimming the pipes.
Version April 2011
1
from the welding value tables in the
1
in the diagram, the pipes remain
2
) plus P
t
in the diagram, pressure is
3
in the diagram). In most cases, however,
6
P
P
+ P
+ P
5
5
+ P
+ P
t
t
t
t
t
t
t
t
2
2
3
3
4
4
HÜRNER Manual 315-R User's Manual
in the diagram, the pipes
from the welding
2
+ P
, either until
t
5
in the dia-
5
(10 seconds
5
t
t
t
t
t
t
5
5
6
6
4
t
t
11
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