Page 296 - Trenchless Technology Piping Installation and Inspection

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pipe to move if expansion or contraction occurs. The PVC fitting
requires HDPE pipes with SDR of 21 or lower.

6.9.9 Pipe Connection to Other Pipes
HDPE pipes are joined to other PE fittings by heat fusion or
mechanical fittings. They are joined to other material by means of
compression fittings, flanges, or other qualified transition fittings
(PPI, 2008).

6.9.10 Pipe Bursting Water Mains
The most common materials for existing water mains are cast iron,
ductile iron, and PVC. All three can be replaced by pipe bursting, but
each requires a different piping burst approach. Cast-iron pipe is a
relatively brittle material, and, therefore, the basic pipe bursting sys-
tem is sufficient to shatter the pipe. PVC pipes are not brittle and
require multiblade cutting accessories in front of the bursting head to
facilitate cutting the pipe. Ductile iron pipe is also not brittle; there-
fore, pipe splitting is the most suitable bursting system.
Connections between the replacement HDPE pipe and remaining
segments of existing pipe (non-HDPE pipe), including valves, are
accomplished by mechanical joint (MJ) adapters, which are butt fused
to the HDPE pipe. A gland ring is then used to make a restrained con-
nection between the two types of pipes. Figure 6.14 shows connec-
tions to PVC or ductile iron pipes made using a female MJ connector,
which is butt fused to the HDPE pipe. This connection provides a
restrained connection.

Stainless steel
Retaining reinforcing collar
gland
Ductile iron
or PVC pipe Gland ring

D3 Standard MJ D2 Pipe OD
gasket

L

FIGURE 6.14 Connection to existing PVC or DI pipes using female MJ adapter.
(Source: Handbook of Polyethylene Pipe, 2008.)