Page 138 - Trenchless Technology Piping Installation and Inspection

104 Cha pte r T h ree

Prevention Method and
Deficiency Description Possible Remedial Actions
Lining over Lining over corrosion, loose If the fault is localized, it is
debris debris in pipe, inadequate best to rectify by excavation
pipe cleaning. and removal of faulty pipe
section. If faulty pipe section
is extensive, it must be totally
replaced.
Blistering and Round, raised sections If blisters are isolated, they
bubbling of hardened coatings and may be cosmetic in nature
linings caused where there and do not create a long-term
is graphitization on cast weakening of the lining. The
iron pipe walls. It must be integrity of the lining is not
noted that not all instances compromised and no remedial
of graphitization cause action is taken.
blisters.
Uncured lining Malfunction of the lining Using CCTV or other
machine. Only section of inspection methods will reveal
pipe lined with hardened, any sections of uncured lining
fully cured lining may be which must be removed and
returned to service. relined.
Uneven or thin Machine malfunction, Short length can be replaced
lining excessive friction along with new pipe and longer
the hose during winching lengths can be relined.
back through the pipe, Protruding obstacles can
unsatisfactory design of be identified during CCTV
application head, protruding inspection.
obstacles in pipe.
Slump Caused by applying an The extra volume of the lining
excessive thickness of material can reduce the
coating or lining to the pipe desired pipe diameter.
surface or overheating the
components.
Water damage Usually caused by The extent of fault must be
undetected standing water accurately measured by CCTV
or ground water leakage inspection. Short length can
through pipe. be replaced with new pipe
and longer lengths can be
recleaned and relined.
Pinholes Pinhole or discontinuity in Must be repaired by relining
the lining. or as directed by the owner or
the city engineer.

Source: AWWA, 2002.
TABLE 3.4 Summary of Defects and Remedial Actions