Page 141 - Trenchless Technology Piping Installation and Inspection

Coatings and Linings for Potable W ater Pipe Distributions 107

FIGURE 3.6 Cement-mortar lining troweled fi nish. (Source: www.cementlining.
com.)

(AWWA-C602, 2000). Cement-mortar-lined pipes are centrifugally
lined to ensure that a uniform thickness of mortar is distributed
throughout the length of the existing pipe. Cement-mortar linings
prevent tuberculation by creating a high pH at the pipe wall. They act
as a physical barrier between water and the existing pipe with a
smooth finish, which potentially may increase hydraulic capacity of
the existing pipe, in spite of slight internal diameter reduction. The
protective properties of cement linings are due to two properties of
cement: chemically alkaline reaction of the cement and water reduc-
tion in contact with the iron pipe.
Cement-mortar lining is applied by a rotating spray head con-
nected to a hose that is attached to the lining rig. Mortar is supplied
to the machine through the high-pressure hose, and a uniform thick-
ness of lining is applied as the machine moves through the existing
pipe at a constant speed. The thickness of the applied liner is directly
related to the speed at which the machine moves. After the liner has
been applied, a rotating or conical drag trowel provides a smooth
finish (see Fig. 3.6).
*
Installation Procedure of Cement-Mortar Linings
1. Inspecting the existing pipe to determine the location of
valves, hydrants, bends, level of deterioration, displacement
of joints, and so on.

∗ Refer to Table 3.9 for detailed description about the steps involved during the
installation of spray-on coatings and linings.