Checking Pipe Alignment And Determining Drag Pressure; Bead Build-Up Stage - Hürner HWT 400-M Manuel Utilisateur

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10. When the facing is properly finished, use the immediate-action
full release valve to release the pressure in the circuit. Wait for
the facing tool to have turned for another 1 - 2 rotations.
11. Move the carriage apart again, turn off the facing tool, and tilt
it up from in-between the carriages.
If you discover after the facing process that the butts are still not level,
start over, insert the facing tool and repeat the process, if sufficient
material at the component butt allows the defined distance traveleld
during facing. If not, start the process again at step 3 above. When
facing is properly done, component alignment has to be checked.

4.4.2 Checking Pipe Alignment and Determining Drag Pressure

When the components are properly faced, close in the movable carriage
completely to check whether a potential vertical and horizontal offset
is within the tolerance allowed by the applicable welding standard. If
component alignment is in order, the welding proper can start. If the
offset is outside tolerance, the components must be readjusted in the
clamps and, if needed, facing has to be repeated.
When the components align appropriately, move the carriage apart
using the carriage mover lever; make sure the movable carriage is as
far apart as possible before continuing. Turn the maximum pressure
regulator counter-clockwise as far as it will go to have zero pressure in
the hydraulic circuit. Then set the carriage mover lever to its close-in
position while simultaneously turning the maximum pressure regulator
gradually clockwise. Watch the pressure gauge closely to observe at
which pressure level the carriage is "dragged" to start moving. Take
note of this value, preferably on paper, as the drag pressure P
welding operation.
The exact drag pressure depends on various conditions (size
and material, position/altitude of the machine, etc.) and has
to be determined for every welding individually. The value
Important
P is needed to compute the bead build-up, the heating, and
t
the joining pressures needed for jointing (stages t
t in the welding diagram respectively).
5

4.4.3 Bead Build-up Stage

Use the welding value tables in the Appendix to look up the joining
pressure (maximum pressure to be applied during bead build-up and
joining) appropriate for your situation. Then set the maximum pressure
regulator to joining pressure plus drag pressure (see Sect. 4.3.2) while
observing the actual pressure shown on the gauge, and move apart
the carriage of the machine. Using the welding value tables, check
that the heating element (heating plate) has the correct temperature
and insert it between the butts, move the carriage in on the heating
plate and press the pipe butts to it at a pressure of P
build-up duration given in the welding value tables in the Appendix
(t in the diagram above) until the weld bead has properly formed.
1
When the welding is performed with steel master clamps,
using an optional additional cylinder that adds stability ito
the master clamps is recommended if the size of the welded
components is 250 mm or larger. Install it, if you use it, on
Info
top of the clamps per the manual that ships with it. Keep in
mind that when the additional, reinforcing cylinder is
used, the pressure values from the manual of the ad-
ditional cylinder apply to the welding rather than the
values in this manual you are reading.
Version January 2020
+ P for the bead
1 t
HÜRNER HWT 400–M User's Manual
for this
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EN