Page 144 - Trenchless Technology Piping Installation and Inspection

110 Cha pte r T h ree

(a) (b)

FIGURE 3.8 (a) Spray head for epoxy lining; (b) Finished epoxy lining.
(Source: CuraFlo Inc.)

Advantages Limitations
1. Has a higher “C” coefficient than 1. Bypass is required.
cement mortar and better improves 2. Pipe must be dry and free
flow capacity of the existing pipe. from standing water during
2. Provides a smooth, pinhole -free lining. application.
3. Resistant to corrosive water. 3. Does not enhance the
4. Does not block service connections. structural integrity of the
5. Only entry and exit pit is required, no existing pipe.
major excavation is required. 4. Tees and bends can pose
installation difficulties.
6. Protects further deterioration of
existing pipe against corrosion. 5. Minimum cure time can be
16 hours.
7. No major reduction in the existing pipe
diameter.

TABLE 3.6 Advantages and Limitations of Epoxy Linings

With a suitable existing pipe surface preparation and substrate
conditions, polyurea provides fastest return to service than com-
peting lining materials. During a field evaluation, it was shown
that polyurea application does not plug service laterals and appur-
tenances (see Fig. 3.9).
Polyurea is formed from reaction of two components, isocyanate
and amine resin. These components, unlike those created by the
crystalline nature of some polyurethane hard segments, form a urea
linkage, which is highly flexible. The material is moisture tolerant
and has low viscosity, thus it can be easily pumped to remote spray
head locations. It provides high build slump resistant linings, and
dependent on manufacturer and class of material (structural or non-
structural) excellent adhesion characteristics. Finished linings are
hard, glossy, and free of surface tack or greasiness. Polyurea linings