A Case of Utilizing Results
Creation of Visual Inspection Criteria for Deterioration of PVC
Pipes
OGAWA Fumiaki, Head; FUKATANI Wataru, Senior Researcher; SUEHISA Masaki ,Researcher; KAYA Takuro , Guest Research Engineer
Wastewater System Division, Water Quality Control Department
Keywords: sewer, maintenance guideline, PVC pipe, visual inspection criteria
1. Introduction
In recent years, road cave-ins and similar accidents
have been frequently seen. To prevent such accidents,
the deterioration in sewers should be accurately detected.
Deterioration in sewers is commonly determined inaccordance with visual inspection criteria using TV
cameras, but these inspection criteria were establishedmainly for rigid pipes such as reinforced concrete pipes.
It is, therefore, difficult to detect deterioration with theconventional criteria for PVC pipes, which are plastic
flexible pipes and account for about 50% of the total
length of pipe in the country.
Considering such circumstances, NILIM has
established visual inspection criteria (draft) for detecting
deterioration in PVC pipes.

pipes and create visual inspection criteria for deterioration,and conducted TV camera surveys of PVC pipes laid
more than 30 years ago, and load-proof performance tests
and two-dimensional nonlinear static analyses (CAE) ofdeteriorated PVC pipes.
Consequently, as deterioration characteristics of PVC
pipe, the presence of overall section change (Photo 1) andlocal section change (Photo 2), and the relationshipbetween cracking and load bearing capacity wereclarified. Based on these findings, we added the flatness
and deformation of PVC pipes to visual inspection
criteria, and clearly positioned the inspection criteria forcracks, etc. (Table).

2. Preparation of visual inspection criteria for
PVC pipes
For sewerage, rigid pipes such as reinforced concrete
pipes and earthenware pipes, and plastic flexible pipes
such as PVC pipes are mainly used. These two types ofpiping are greatly different in structure and material, so
their characteristics of deterioration are also different.
For example, reinforced concrete pipes are very strong
but are susceptible to changes in material properties,
while PVC pipes are not susceptible to such propertychanges but are susceptible to changes in shape.
Accordingly, NILIM collected and analyzed TV
camera survey data from local governments in order toidentify the deterioration characteristics unique to PVC

Photo 1: Example ofFlatness

Photo 2: Example ofDeformation

3. Conclusion
The Japan Sewage Works Association is revising theSewerage Maintenance Guideline, to which the visualinspection criteria for PVC pipes, created by NILIM, will
be added.

Table: Visual Inspection Criteria (Extract)
Rank

Inspection for each pipe

ItemOperation
Reinforced
concrete pipe

Damage and axial
crack to pipeaLack
Axial crack 5 mm ormore in width

Lack
Earthenware pipe
PVC pipe

Flatness

PVC pipe

Deformation(Projecting inward)

PVC pipe

Axial crack at least
one-half of the pipe
lengthMap crack
Axial crackbc

Axial crack 2 mm orAxial crack lessmore in widththan 2 mm in width
Axial crack less than
one-half of the pipe
length---Flat with flexibility
Flat with flexibility
factor of 15% or more factor of 5% or moreWhitened or projecting
Projecting inward lessinward less than 10%
than 10% of the innerof the inner diameter
diameter of the pipeof the pipe-