How to...
Pipe jointing systems:
Compression fittings: Small bore pipes from DN 16
to DN 110 are mechanically joined with compression
fittings. These fittings incorporate an inner seal and an
outer grip ring that provides a positively locked joint
that enables the pipe to handle end-thrust created
by the internal water pressure and can be tightened
by hand. The range of fittings includes connectors,
elbows, flange adaptors, male and female adaptors
and tee’s.
Electro-fusion fittings: These fittings include a metal
coil in the socket and jointing is achieved through the
use of a machine that has leads that plug into the
fitting and heat the coils to the required temperature
in order to create a fusion joint. A full range of
fittings is available in sizes up to about DN 250 with
couplings available up to DN 700, dependent on the
manufacturer.
Butt-welding: Butt welding creates a fusion joint
through the use of a butt-welding machine. The
machine includes a system of pipe clamps and a hot
plate that heats the pipe ends and holds them together
to achieve a permanent fusion joint when cooled. The
system is used for the connection of large diameter
pipes from about DN 250 to DN 1000 in various
pressure classes and also the fabrication and jointing
of plain ended HDPE fittings suitable for in-line butt
welding applications.
It cannot be stressed enough that HDPE fusion welding is a
highly specialised process and requires the operator to have
professional training and extensive experience in order to
achieve the required level of jointing quality. Refer to your
Irrigation Design Engineer, who will either have a qualified
jointing team available or may call on independent
contractors to carry out the jointing process
The butt welding process
Butt Welding machines are all based on the same principle, in
that they contain pipe clamps of various sizes which are mounted
on rails utilising levers or hydraulic actuators to vary the distance
between the pipe ends and a removable heating plate. Each
unit is designed to accommodate a limited range of diameters,
with the smaller units being compact and easily portable and the
larger units having separate components that require the use of
a digger loader or a similar mechanical lifting device to position
the components.
PREPARATION
Step 1
Gather the required equipment and materials
ff It is extremely important to ensure that the pipe and
fittings supplied are of the same diameter, SDR ratio
(pressure class) and PE grade
ff Generator, with sufficient fuel and extension leads in
order to supply power to the jointing location
ff Butt welding machine with the correct size of clamps,
face trimmer, heating plate, hydraulic pump and timer
ff Butt-welding time and pressure tables
ff Electro-fusion machine and pipe peeling tool or scraper,
as well as a correctly sized electro-fusion coupling, as
required in this application
ff Pipe support rollers, used to support the pipe during the
jointing process
ff A cutting tool to suit the pipe diameter
ff Tent or suitable structure to protect the jointing location
from wind and rain
ff Cleaning materials including paper towel and a cleaning
solvent
ff Marking pen
Step 2
Ensure that the welding equipment is clean and in good
working order
ff Conduct a temperature test on the preheated welding
plate. Jointing temperatures may vary from 195 to 200
°C dependent on the ambient temperature
ff Ensure that the trimming tool and hydraulic pump are
operational and ready for use
Step 3
Place the pipes to be joined in the cradles and tighten the
clamps
ff Use the additional support rollers to align, support and
level full pipe lengths
ff The clamps serve the dual function of holding as well as
re-rounding the pipes in the joint area
The following is a step by step procedure to complete a large
diameter butt-fusion joint and a brief description of the electrofusion process for fittings. The procedures described have been
summarised and should not be considered as being complete in
terms of detail. Procedure Manuals and Codes of Practice such as
SANS 0269 are available from the pipe and fitting Manufacturers
SABI | DECEMBER 2015/JANUARY 2016
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