Polyethylene (PE) is a very robust and ductile pipe material. In its early days
it was often referred to
as "Alkathene", which was, in today's parlance, MDPE or Medium Density Poly-Ethylene. Although MDPE is
still used for some smaller
bore pipe systems, larger bore systems are HDPE (High Density Polyethylene).
PE pipe tends to come in three main colours;
Blue - Approved for potable water systems
Black - Used for non-potable systems
Yellow - Used for gas, yellow PE pipe is, unlike standard PE, not gas permeable and is manufactured with
a special lining.
We primarily supply black PE systems comprising of pipe, electrofusion and long
spigot fittings. We also supply
small
bore blue MDPE pipe from
stock, and can provide quotations
for larger bore blue polyethylene pipe and fittings if required.
We do not supply yellow gas PE pipe and fittings.
Connecting PE pipes
Polyethylene cannot be glued or solvent welded (like PVC and ABS pipe). The
jointing methods therefore need to either rely on
mechanical or heat welded methods.
Jointing Method
Compression Jointing
Electrofusion Jointing
Butt Welding
Compression couplings incorporate a grip ring that holds the pipe
firm once it has been pushed through
an O-Ring. A compression ring is then turned, which tightens the grip. Compression fittings are usually
made from Polypropylene (PP) with an EPDM
O-Ring, although some metal fittings are occasionally used. Compression fittings can be installed by
non-skilled persons without the need for special tools or equipment.
Electrofusion fittings (also called EF) have a copper coil wound
through the inside of the fitting. The pipes
are pushed into either side of the fitting and an electric current passed through the coil. The current
heats the copper coil and melts the two surfaces together.
Butt welding uses specialist hydraulic clamping machinery to trim
the ends of two pipes perfectly flat. A heat plate is then
placed between the ends and after they have been heated for a preset period, the plate is removed and
the machinery pushes
the two ends together, causing them to melt into each other. A raised "bead" is formed as a
result of the joint, running around the inside and outside of the join. This can cause
issues if a smooth internal bore is required. Machinery can be used to remove the bead, but this adds
another
complication to the process. Butt welding is most commonly used on larger pipe bores, where the cost or
availability
of EF fittings prohibits their use.
