How to...
How to...
Butt Weld HDPE
Polyethylene pipe
A step-by-step guide to the Butt Weld jointing of HDPE Pipe -
by Mike de Villiers
T
he Irrigation market is a major user of PVC pressure pipes for main lines and LDPE pipes for small
bore distribution systems. The use of HDPE pipes for main lines is a growing trend, due to the excellent
performance of the pipes in rugged conditions and the ease and reliability of fusion jointing. This editorial
will focus on the butt welding of HDPE pipe..
INTRODUCTION
Raw materials
Plastic pipes fall into two broad chemical families, PVC
(Vinylchlorides) and Polyolefins, including Polypropylene and
Polyethylene. Polyethylene is supplied in various grades of
hardness which are designated as PE grades. PE 32 is termed
as low density (LDPE), PE 40 as medium density and the high
density grades (HDPE) are supplied in PE 63, PE 80 and PE 100,
which designate the hardness (strength) of the pipe material and
therefore also the pipe wall thickness. The minimum required
strength (MRS) for the three grades of material is 6.3, 8.0 and
10.0 MPa respectively as stated in the SANS 4427 Specification.
Polyethylene Pipe Specifications
The overriding SABS specification for HDPE Polyethylene Pipe
is SANS 4427, which only includes OD (outside diameter) pipe
specifications and does not include the PE 32 (LDPE) grade of
26
SABI | DECEMBER 2015/JANUARY 2016
material. The introduction of the SANS 8779 specification for
LDPE piping in 2013 replaced the old SABS 533 ID (inside
diameter) specification. The Industry is therefore reminded that
in about 3 years time all SABS approved LDPE pipe will only
be available in OD dimensions according to the SANS 8779
specification.
The use of PE 63 and PE 80 HDPE pipe grades has largely being
replaced by the PE 100 grade, which provides many advantages
over the “older” grades of material. The most obvious being the
savings in the pipe mass through the thinner walls, made possible
by the higher density of the PE 100 grade of material. The SANS
4427 specification includes OD pipe diameters from DN 16
to DN 10 [