Page 192 - Trenchless Technology Piping Installation and Inspection

Pipe and Pipe Installation Considerations 157

direction. Also, the resulting HDB is increased from 4000 to
7100 psi. Consequently, this stronger material can have a
thinner wall than a conventional PVC pipe of the same pres-
sure capacity. The manufacture process of PVC-O in the
United States uses both of the technologies available for
manufacturing the product. Both the batch (offline) and con-
tinuous (inline) processes are used. PVC-O pipe is not used
in gravity applications.
3. PVC-M: Modified PVC is produced by incorporation of addi-
tives or impact modifiers to enhance the toughness of the mate-
rial. Resistance to fracture by absorption and dissipation of
energy is an evidence of the toughness of the pipe material.
PVC-M is made and used mainly in Europe and Australia,
whereas only one manufacturer in the United States produces
this type of pipe for nonburied applications.

Solid Wall and Profile Wall PVC Pipes
PVC pipes are available for pressure applications only as solid wall
pipes. For gravity applications, both solid wall and profile wall pipes
are manufactured. Solid wall pipe, as the name suggests, are made of
a continuous wall of PVC of uniform thickness, as shown in Fig. 4.27a.
Profile wall pipe, on the other hand, is braced spirally or circumferen-
tially with structural shapes, but provides a smooth-wall interior, as
shown in Fig. 4.27b. Profile wall pipes economize on the amount of
material needed for fabrication; by altering the shape of the wall, the
same stiffness as solid-wall pipe is achieved, using less material.
Profile wall pipes generally fall into three categories—open profile
(OP), closed profile (CP), and dual-wall corrugated profile (DWCP).
OP pipes have their rib enforcements exposed on the outside of the
pipe. CP pipes make use of a closed profile that provides a continu-
ous outer wall where the wall sections are hollow and are often
described as an I-beam or honeycomb. DWCP pipes have a smooth-
wall waterway, braced circumferentially with an external corru-
gated wall.

(a) (b)

FIGURE 4.27 (a) and (b) Solid wall and profi le wall PVC pipe.