Performing The Welding Process - Hürner HWT 400-M Manuel Utilisateur

H Ü R N E R S c h w e i s s t e c h n i k G m b H
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the temperature of it; to ensure consistent bead formation, do
this at drag pressure (P
the Appendix.
• Heating Stage – In this stage, t
remain in contact with the heating element, soaking heat from
it; the pressure is reduced to drag pressure (P
welding value tables in the Appendix.
• Change-over Stage – In this stage, t
is shut off from the components, the carriage moves apart to the
far end to allow taking the heating element out from in-between
the components.
• Joining and Cooling Stage – This stage is characterized by a suc-
cession of events. First, after change-over, the components butts
are put together and pressure increases as a linear ramp to drag
pressure (P ) plus P
t
(t in the diagram). Then, the joint cools down at P
4
until pressure is completely removed from the the components
(t in the diagram) or until pressure is reduced to one-third of P
5
(10 seconds into t
completed 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
1 t
P
2
t t
1
4.4

Performing the Welding Process

To start welding, clamp the components into the master clamping as-
semblies. Use the appropriate reducers if the component size is smaller
than the master clamps.
Select the clamping assemblies appropriate for the welding operation
in hand: for straight and segmented-bend joints, for tee and crosspiece
production or for Y branch-off production. See Sect. 3.4 and 5.1 ff. for
detailed explanations of the differences between the various kinds
of clamping assemblies and of how they are installed and removed.
As a preparation to the welding process and prior to it, the applicable
welding pressures P and welding times t have to be looked up in the
tables in the appendix (see Sect. 4.4.3 ff. below).
All pressure values P in the tables in the appendix are for
a straight joint. In angled joints, all values are identical,
excepting forces, to which apply other values, P
Important
depending on the planned angle α according to the following
equation (α = the angle at which the components are bevel-
cut, i. e., half of the angle of the intended joint):
Version January 2020
) plus P from the welding value tables in
t 1
in the diagram, the components
2
3
from the welding value tables in the Appendix
5
in the diagram); in the second case, cooling is
5
in the diagram). In most cases, however,
6
P + P
5
+ P
t
t t
2 3 4
HÜRNER HWT 400–M User's Manual
) plus P from the
t 2
in the diagram, pressure
+ P , either
t 5
t
t t
5 6
, computed
α
P
P =
α
coeff
5
t
α
15
EN