Page 211 - Trenchless Technology Piping Installation and Inspection

Pipe and Pipe Installation Considerations 175

FIGURE 4.32 Proprietary ductile iron restrained joints used in trenchless
construction.

Advantages Limitations
1. Wide variety of internal and 1. Highly susceptible to corrosion,
external corrosion protection both internally and externally,
systems available unless protected
2. Internal cement mortar lining 2. Not all available corrosion
prevents tuberculation and protection methods are effective
enhances hydraulic capability 3. Internal cement mortar lining is
3. Strong material, with high easily damaged if struck with a
load bearing strength, impact backhoe.
strength, and beam strength 4. Cathodic protection is cost
4. Wide variety of joints prohibitive and is rarely used in
enable various applications, municipal systems
including trenchless 5. Polyethylene encasement is easily
5. Available for both pressure damaged and subject to improper
and gravity applications installation
6. Wide range of diameters and 6. Heavy weight, resulting in high
pressure classes available cost of labor
7. Long laying lengths reduce 7. Lack of flexibility is an obstacle in
joints in the system trenchless installations
8. Pipe is highly resistant to 8. Gaskets in the joints are highly
chemical permeation in vulnerable to chemical attack in
contaminated areas contaminated soils

TABLE 4.18 Advantages and Limitations of Ductile Iron Pipe