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2.6. Selecting the correct welding temperature
The welder heating element is preadjusted to the average welding temperature
for PE-HD pipes (210°C). Depending on the pipe material and the gauge of
the pipe walls, it may be necessary to adjust this temperature. In this case,
observe the manufacturer's information on the pipes or mouldings without fail.
Fig. 5 contains a graph showing the guideline temperatures for heating elements
according to the gauge of the pipe walls. In principle, the higher temperature
should be used for thinner walls and the lower temperature for thick walls, as
far as possible (DVS 2207, Part 1). In addition, environmental influences
(summer/winter) may make it necessary to adjust the temperature. For this
reason, the temperature of the heating element should be checked, e.g. with
an electric surface thermometer. If necessary, the temperature can be adjusted
by turning the temperature adjusting screw (26). In this case, it should be
remembered that the heating element must not be used until 10 minutes after
the preset temperature has been reached.
3. Operation
3.1. Description of process
In the butt welding process, the contact faces of the two components are
matched to each other under pressure on each side of the heating element,
heated to welding temperature at reduced pressure, then joined under pressure
after the heating element has been withdrawn (Fig. 6).
3.2. Preparations of welding
If the machine is used in the open air, care must be taken to ensure that welding
will not be adversely affected by unfavourable environmental condi tions. In bad
weather or strong sunlight, the welding position should be covered, if necessary
with an awning. To prevent the uncontrolled cooling of the welding position by
draughts, the welded pipe ends should be enclosed. Out-of- round pipe ends
must be trued up before welding by e.g. carefully heating with a warm air heater.
Only pipes or pipes and mouldings of the same material and wall thickness
may be welded. Pipes should be cut off with a REMS RAS pipe cutter (see
1.1).
3.3. Clamping the pipes
Pipe clamping inserts (27) corresponding to the pipe diameter should be installed
in the clamps (19) in such a way that the cranked side of the inserts faces the
centre. The inserts are secured with hex screws (28) by means of the wrench
supplied. The two pipe support inserts (29) should be similarly installed on the
pipe supports (30) and secured with hex screws (28). The pipes or pipe sections
should be aligned in the clamping assembly before being clamped. If necessary,
long pipes should be supported with a REMS Herkules (see 1.1). For short
pipe sections, the pipe supports (30) should be adjusted or turned through
180°. For this purpose, loosen clamping knob (31) and reposition the pipe
support or raise knob (32) and turn the pipe support about the axis of the
clamping knob (31). The pipe ends should project 10-20 mm towards the centre
beyond the clamping adapters or clamps to permit planing.
Align the pipes or fittings in such a way that the faces are parallel to each other,
i.e. the pipe walls must be in alignment in the area of the joint. If necessary,
the clamps should be released and the pipes re-aligned and turned (check for
out-of-roundness). If adjustment proves unsuccessful after several attempts,
it will be necessary to readjust the clamping system. For this purpose, the
clamping screws (33) on both clamps should be released and a pipe clamped
in each of the two clamps. If the pipe is not resting in the clamps and on the
pipe supports, centre the clamps by tapping the sides. With the pipe still clamped,
retighten the clamping screws (33).
The clamps must enclose the pipe ends securely. If necessary, readjust the
clamping nut (34) under the clamping cam (35) until the clamping lever (36)
can only be closed with a certain amount of force.
3.4. Planing the pipe ends
Immediately before welding, the pipe ends must be planed flat. For this purpose,
the electric facing cutter (6) is swivelled into the working area and switched on
by means of the rocker switch in the handle (20). While the facing cutter is
running, the pipe ends must be slowly offered up to the planing discs by means
of the contact lever (7). Planing should be continued until an unbroken swarf
is formed on both sides. With the facing cutter still running, now slowly ease
off the contact lever (7) so that no swarf remains on the pipe ends. After the
facing cutter has been swivelled out, the planed pipe ends should be brought
together on a trial basis, so as to check that the faces are parallel and that the
pipes are not axially displaced. Under the application of adapting pressure, the
gap between the parallel faces must not exceed the width specified in Fig. 7
or the displacement on the outside of the pipe exceed 10% of the wall thickness.
The planed faces must not be touched again before welding takes place.
If a pipe or moulding on one side can no longer be planed or must not be planed
at all, whereas further planing is required on the other side, the stop buffer on
the underside of the planer housing should be swivelled out on the side on
which no further planing should take place.
3.5. Butt welding process
In the welding process, the joint faces are heated to welding temperature by a
heating element, then welded together under pressure after the heating element
has been withdrawn. Before each welding process, the temperature of the
heating element in the welding area should be checked. If necessary, it must
be adjusted as described in 2.6. Also before each welding process, the heating
element should be cleaned with non-adherent paper or a non-fraying cloth and
spirit or industrial alcohol. In particular, no remnant of plastic must be left
adhering to the coating on the heating element. Also in the clean ing process,
care must be taken to ensure that the anti-adhesive coating of the heating
element is not damaged by tools.
The process stages are shown in Fig. 8.
3.5.1. Adapting
In the adapting process, the joint faces are pressed against the heating element
until a bulge forms around each circumference. During this process, a matching-
up pressure of e.g. 0.15 N/mm² should be applied for PE (DVS 2207, Part 1).
Depending on the diameter and wall thickness of the pipe, the requisite degree
of pressure must be calculated to ensure a pressure of 0.15 N/mm² at the joint
faces. Pressure F is calculated from the product of adapting pressure p and
pipe face area A (F = p · A), i.e. the greater the pipe face area, the higher the
pressure required. Thus, a pipe of e.g. 110 mm diameter and PN 3.2 (s = 3.5 mm)
gives a pipe face area of 1170 mm² and a requisite adapting pressure of F = 0.15
N/mm² · 1170 mm² = 175 N. A plate (37) is attached to each machine containing
a table indicating which pipes can be welded, up to what pressure stage, and
under how much pressure, with the machine concerned. Figs. 10 to 13 show
these tables for the REMS SSM models 160 R, 160 K, 250 K and 315 RF. Take
the value of the requisite adapting pressure from the respective table (Fig. 9
and 16) and apply with the contact lever (7). When the joint faces are pressed
together by means of the contact lever, the applied pressure can be seen by
reference to the pointer (38).
Before welding takes place, a check must be made to ensure that the clamps
are holding the pipe sections sufficiently securely to enable them, as a minimum,
to absorb the necessary pressure. For this purpose, bring the pipe ends together
cold and apply at least the calculated pressure by means of the contact lever
(7) on a trial basis. If the clamps do not hold the pipe sections securely, the
clamping cams (35) must be readjusted (see 3.3.).
The adapting process is concluded when a bulge, which is at least as high as
the figure given in Fig. 14, column 2, has formed around the entire circumfer-
ence of the pipe sections.
3.5.2. Heating
For the heating process, the pressure is reduced to almost zero. The heat ing
period is given in Fig. 14, column 3. During the heating process, the heat
penetrates into the joint faces, raising them to the necessary welding temper-
ature.
3.5.3. Changeover
After heating, the joint faces shoud be withdrawn from the heating element,
which is then retracted without touching the heated faces. These are then
rapidly brought together until just before they touch. The time taken for this
process must not exceed the limit given in Fig. 14, column 4, otherwise the
joint faces will cool to an impermissible extent.
3.5.4. Joining
The joint faces must be barely moving when brought into contact with each
other. The contact pressure should be uniformly increased to 0.15 N/mm² (DVS
2207, Part 1) and must be maintained during the cooling-off period (Fig. 14,
column 5). The contact lever is secured with the clamping lever/knob (37) during
the cooling-off period. The requisite pressure, as described under 3.5.1., should
be taken from the tables in Figs. 9 – 16. After the joint has been completed, a
uniform, double bulge must have formed around the en tire circumference. The
shape of the bulge gives an initial indication as to the uniformity of the weld.
Dimension K of the bulge (Fig. 15) must always be greater than 0, i.e. the bulge
must project beyond the circumference of the pipe all round.
3.5.5. Releasing the welded pipe
At the conclusion of the cooling-off period, the clamping lever/knob (39), by
which the contact lever is secured, must be released before the clamps are
opened, so that the contact pressure can be slowly relieved without ad verse ly
affecting the welded seam. The clamping lever (36) can then be opened and
the welded pipe removed from the machine. Allow the welded seam to cool
naturally, i.e. do not accelerate the cooling process with water, cold air or similar.
For stress loading capacities, see the manufacturer's information on pipes and
mouldings.
4. Maintenance
WARNING
Pull out the mains plug before carrying out maintenance
or repair work! This work may only be performed by qualified personnel.
4.1. Maintenance
REMS SSM machines are entirely maintenance-free. The gear of the electric
facing cutter runs in a sealed grease housing and therefore does not need any
lubrication.
4.2. lnspection/repairs
The anti-adhesive coating on the heating element must be cleaned with non-
adherent paper or a non-fraying cloth and spirit or industrial alcohol before each
welding process. Any remnants of plastic adhering to the heating unit must be
cleaned off in the same way. In this process, take care to ensure that the anti-
adhesive coating on the heating element is not damaged by tools.
The facing cutter motor is equipped with carbon brushes. These are subject to
wear and must therefore be inspected and/or replaced from time to time. For
this purpose, loosen the four screws on the motor cap (40) approx. 3 mm, pull
the cap to rear and remove the two covers from the motor housing.
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