Page 210 - Trenchless Technology Piping Installation and Inspection

174 Cha pte r F o u r

Pressure Standards Nonpressure Standards Available Diameters (in.)
— ASTM A716
— ASTM A746 4–64
AWWA C150/C151 AWWA C150/C151
TABLE 4.17 Applicable Ductile Iron Standards for Trenchless Technology

The pipe is cast using a centrifugal method, after which it is annealed
in furnaces. An asphaltic coating is applied to the outside of the pipe,
while the interior is coated with a cement-mortar lining. Unlike gray
iron pipe, ductile iron pipe will bend significantly without breaking
when subjected to even quite great loads, impacts, or deflections.
Applicable Standards Table 4.17 lists a number of standards available
for trenchless applications. It should be noted that these pipes can
also be installed via open-cut methods. For trenchless pull-in installa-
tions, the joints must be restrained, as discussed in the following sec-
tion. In recent years, ductile iron pipes with restrained joints have
been used in trenchless construction methods (TCM) as well as for
trenchless renewal and replacement methods (TRMs).

Joints Restrained joints in ductile iron pipe are available primarily
to accommodate the thrust forces acting on a pipeline. However,
pipes with these restrained joints have been used in recent years for
various types of trenchless projects, both new constructions as well as
renewals. HDD and pipe bursting have been the most common appli-
cations of the restrained joint ductile iron pipe. The joints are capable
of withstanding tensile forces encountered during pull-in process.
Proprietary restrained joints have been designed by various manu-
facturers which incorporate a push-on gasket and special bell design
in conjunction with their restraint mechanisms. Because of their pro-
prietary nature, the push-on gaskets used in these joints may not be
compatible with standard push-on gaskets. In the 350 psi allowable
working pressure range, the joints are suitable for pipe diameters of
4 through 24 in. In the 250 psi range, the joints are available for diame-
ters of 30 through 64 in. Figure 4.32 shows five such proprietary joints.
Advantages and Limitations Table 4.18 summarizes the advantages
and limitations of ductile iron pipe. The high load-bearing capacity,
high impact strength, and high beam strength makes it a sturdy pip-
ing material for pressure applications. There are many different
types of joints, including restrained joints, which are used in trench-
less applications. The long lengths of ductile iron pipe (20 ft) mini-
mize the number of joints within a water or sewer system. The wide