Plastiline™ - Humes

8 Laying and jointing of pipes lined
with Plastiline
8.1 This section of the specification is not intended to
cover the laying and jointing of the basic concrete pipe but
deals with the additional jointing requirements arising from
the lining only.
It is essential that care should be taken to prevent damage
to the lining during handling and laying of the pipe.
When pipes lined with Plastiline have been laid and
jointed to form a pipeline, the concrete surfaces at the
circumferential joints must be protected either by
connecting and sealing the linings or by constructing a
special joint.
8.2 Field welded joints shall be either Type P1 or
Type P2.
Type P1 — Special Pipe Joint
using cover strip for butt or flush
or spigot & socket joints or for
pipe to structure
8.3 Field welding of strips associated with joint types P1
and P2 shall be carried out by qualified PVC welders using
approved methods and techniques.
8.4 Welding operators must be trained and accredited by
Humes before welding field joints. Proof of welding ability
is required prior to commencing work and approval is based
on the result of tension tests on three sample welds. The
test is carried out according to ASTM D 412 with the
tension transverse to the line of the weld. All samples shall
reach a stress of 13 MPa in the Plastiline sheet away from
the weld, without failure.
8.5 The technique of welding requires the weld strip
to be heat-fused to both sections of the sheet overlapped
by the strip. Particular attention must be given to ensuring
the surfaces to be welded are quite clean and for this
purpose the cleaning agent Applied Chemicals 4480 is
recommended.
8.6 In order to obtain a good quality weld the operator
must achieve the correct temperature to just bring the
mating surfaces to a semi-molten condition. Sufficient
pressure must be applied to force the molten surfaces into
intimate contact until the weld has solidified. Attention
must be given to obtaining weld beads on both sides of the
weld strip (see illust. below). After welding, beads should
be visible on both sides of the weld strip.
Care must be taken not to overheat the Plastiline during
welding. It should be noted that a temperature of 200 O C
or more can cause decomposition of the material. Charring
is evidence of too high a welding temperature.
Type P2 — Normal Pipe Joint
using flap for spigot & socket
joint or butt or flush joints;
straight pipes only
The use of a 100mm flap will not be permitted for splay joints in
reinforced concrete pipelines. Plastiline at splay joints shall be
joined with a type P1 joint.
The Type P1 is used for short length pipes and for splay
joints, and is made by placing a joint strip over the joint,
which is secured and sealed at the edges using two
weld strips.
With the Type P2 joint, which is the most frequently used
for full length pipes in diameters 600mm and larger, a plain
flap of unkeyed lining at the spigot end of one of the
jointed pipes is lapped over the lining of the adjacent pipe
and sealed with a single weld strip.
Plastiline welding plant.
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