Page 204 - Trenchless Technology Piping Installation and Inspection

168 Cha pte r F o u r

Advantages Limitations
1. Resistance to both internal and 1. Older PE materials are subject
external corrosion. Low internal to environmental stress
friction. Smooth interior. cracking due to improper
2. Butt-fused joints effectively embedment or excessive local
create a continuous jointless bending. Newer materials,
leak free joint. like PE 4710 have enhanced
resistance.
3. Abrasion resistant. Use to
convey sand and fly ash slurry. 2. Trained labor and special
equipment required for butt-
4. High ductility and flexibility.
fusion. However, training
Lightweight in smaller
is available for equipment
diameters. Typical minimum
manufacturers and distributors
bend radius of 25–30 times pipe
nationwide.
diameter.
5. Excellent resistance to fatigue 3. Slightly smaller inside
and repetitive surge pressures. diameter than other pipes of
the same outside diameter
6. May be repaired using
size. However, proper design
mechanical couplings and
will minimize this issue.
saddles.
4. Cannot be located unless buried
7. High resistance to failure
with metallic wire or tape.
by impact, even at very low
5. Sensitive to temperature
temperatures.
differentials, resulting in
8. Resists shatter-type or rapid
expansion and contraction
crack-propagation failure.
unless restrained by soil
9. Does not easily crack under
embedment after burial.
expansive forces of freezing
6. Unprotected color products
water.
usually cannot have more than
10. PE with carbon black has a long 5 years of UV resistance.
UV resistance.
TABLE 4.14 Advantages and Limitations of HDPE
manufactured the first fiberglass-reinforced polyester resin pipe.
Traditionally used in industrial applications throughout the world,
GRP is rapidly gaining market shares in North America for large-
diameter municipal water and sewer applications. Municipal sewer
installation include direct bury (open-cut), sliplining (premier prod-
uct for 48 in. and larger), direct jacking, casing carrier (tunnel liner)
and above ground on piers. As a plastic material, GRP is designed as
a flexible conduit and is installed accordingly.

Manufacturing
Fiberglass composites are made of glass fiber reinforcements, ther-
mosetting resins, and other additives such as small aggregates, cata-
lysts, hardeners, accelerators, and the like. Types of resin used include