Page 403 - Trenchless Technology Piping Installation and Inspection

Inspection and QA/QC for Trenchless Installation and Replacement Methods 353

5. Replacing reinforced concrete pipe is difficult unless the
concrete and reinforcing steel are deteriorated. Although
powerful equipment may be used to burst the pipe, care-
ful evaluation must be made on the reinforcement and
deterioration.
6. Steel and ductile iron pipe are not suitable for pipe burst-
ing. But in smaller diameters, they can be replaced by pipe-
splitting technique.
7. PVC and other plastic pipes may be replaced using an appro-
priate combination of bursting and splitting techniques
according to the strength and ductility of the pipe.
8. Asbestos cement pipes are generally good candidates for pipe
bursting. Care must be taken to determine the class of the
existing pipe. Thicker, higher tensile strength pipes require
increased bursting forces. Modifications to standard bursting
heads must include cutter blades to split the pipe.

Replacement Pipe
1. High-density polyethylene pipe (HDPE) is normally used as
replacement pipe for pipe-replacement methods. HDPE
must be solid wall and in conformance with ASTM F714.
All pipe and fittings must be new high-density polyethyl-
ene pipe. The pipe material must be manufactured from a
high-density, high-molecular-weight polyethylene com-
pound which conforms to ASTM D 1248 and meets the
requirements for Type III, Class C, Grade P-34, Category 5,
and has a PPI rating of PE 3408. The pipe produced from
this resin must have a minimum cell classification of
345434C (inner wall will be light in color) under ASTM D
3350. The value for the hydrostatic design basis must not be
less than 1600 psi per ASTM D 2837. Pipe must have ultra-
violet protection.
2. If there is insufficient space to fuse and layout the PE pipe,
PVC pipe with a mechanical spline-locking design joint may
be used for pipe-jacking operations.
3. Special flush-joint ductile iron pipe has recently been devel-
oped as a replacement pipe, which can be used as a carrier
pipe, for either sewer or potable water.
4. Cast-iron pipe, vitrified clay pipe, and reinforced concrete
pipe can be used as replacement pipe in pipe-bursting oper-
ations. However, the bursting head and pipe-installation
technique needs to be modified to avoid significant tensile
force on pipe joints.